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PAIDDALLAS, TX

PERMIT 1786

The

Electrical TesterThe Industry’s Recognized Power & Telecommunications Information Tool

PUBLISHED BY MEGGER SPRING 2007

4271 Bronze WayDallas, TX 75237-1088

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The “X Model” Insulation Tester is here! . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2New options to consider when reviewing your future power factor test set leasing or purchase requirements . . . . . . . . . . . . . . . . . . . . . . . . 3Introducing today’s most advanced Distribution Profiler . . . . . . . . . . . . . . . . . . . . . . . 4Protective Devices Maintenance as it Applies to the Arc/Flash Hazard . . . . . . . . . . . . 6What do you do with a cable fault that won’t "THUMP"? . . . . . . . . . . . . . . . . . . . . . . 8Underground Cable Fault Locating Season is here! . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8Dealing with corroded or open concentric on unjacketed under ground cables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8Why users are raving about these new ground testers . . . . . . . . . . . . . . . . . . . . . . . . . 9Testing Panel Meters with the MPRT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10Underground Fault Locator Pin-Points the Problem . . . . . . . . . . . . . . . . . . . . . . . . . . . 10A Practical Guide to Megger Ground Fault Tracers, the BGFT and BGL . . . . . . . . . . . 11Why CAT IV? A small fault becomes a big problem on Category IV high energy unfused supplies! . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11AVO Training Institute Course Schedule . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12Did You Know? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

The NEW Megger MIT400 Serieshas won a National ElectricalContractor Association (NECA)Showstopper Product Award and a Product of the Year finalisthonor from EC&M Magazine.

Why?Because, in both cases, a panel of your peers inthe electrical testing industry judged it to be theeasiest-to-use, safest and most advanced 1kVinsulation tester available today!

The Megger MPRT continues to be the leader in power capability(its constant power output feature), ease-of-use (with its handheld controller) and its unique overall flexibility. The MPRT’simpressive feature set continues to expand as additional testingcapabilities are introduced.

New feature and capabilities

The latest additions to the MPRT testing capabilities are significantas follows:

• New, rugged “uni-body” chassis/enclosure provides robust,yet lighter weight protection compared to the older,

Batteries are a Waste of Money –

or Are They?

Why has this new instrument alreadywon two prestigious awards?

Rick Lawrence and Marius Pitzer, Megger

Introduction

Batteries are indeed, a waste of money. Thatstatement means to say that if the Power Gridwere 100% perfect, batteries would not benecessary. The many worldwide outages overthe past several years validate the need forbatteries. Who actually gives batteries a secondthought? We simply expect them to workwhen called upon. Experience has shown thatthis expectation is pure fiction.

Batteries are extremely important to provideelectricity to support many assets and revenuestreams during outages. For example, in agenerating station, if the turbine suffers anoutage, without the back-up battery theturbine lube oil priming pumps would notcontinuously keep the bearings lubricatedcausing major damage and lengthy outages. Inhospitals, who wants to be in the middle of anoperation when an ac outage occurs withoutproper battery back-up? The applications for

Megger MIT400 1kV Insulation Tester

Megger, the original inventor of the insulation tester,introduces its “next generation” of high performance 5 kVand 10 kV insulation testers called the SI Series.

The new S1 Series of 5 kV and 10 kV insulation resistancetesters are designed specifically to assist the user with thetesting and maintenance of high voltage equipment. Thisseries of testers includes distinct capabilities including voltage,test current and noise rejection as follows.

Model # Output Voltage Test Current Noise Rejection

S1-552 5 kV 5 mA 2 mA

S1-1052 10 kV 5 mA 2 mA

S1-554 5 kV 5 mA 4 mA

S1-1054 10 kV 5 mA 4 mA

All four models are heavy duty and reliable with features thatmeet the most demanding testing applications in existencetoday.

Users have a choice of 5 kV or 10 kV voltage outputcapability. The 10 kV option is particularly suitable for testingto the IEEE standards required for testing motors ratedgreater than 12 kV.

Includes...High Noise Rejection Feature

Announcing a new,professional line of

5 kV and 10 kVInsulation Testers

MEGGER MPRT RELAY TEST SET

Announcing Significant NEW Testing Capabilities

heavier steel enclosure. The new enclosure also includesside handles which makes it easier to pickup and moveabout.

• New, streamlined firmware provides more precise pulseramp capability. This in-turn provides new capabilitieswithin AVTS software such as binary search and dynamic,multi-state testing of multi-zone impedance relays.Other firmware enhancements have been added to providemore precise timing of multi-state events such as testingreclosing relays. This includes up to 17 virtual timers within

The instrument of choice for commercial and plant electricians

This instrument is perfect for commercial and plant electricians, as well as for testing applications found in electric utilities.

The range

The range consists of eight instruments:

� MIT400 250 V, 500 V and 1000 V� MIT410 50 V, 100 V, 250 V, 500 V and 1000 V plus PI

and DAR� MIT420 Same as Model 410 plus result storage

and download� MIT430 Same as Model 420 plus Bluetooth® download� MIT480 50 V, 100 V� MIT481 50 V, 100 V, 250 V, 500 V, 1000 V plus PI, DAR

and result storage� MIT485 Same as Model 481, plus Bluetooth® download� MIT40X 10 V to 100 V in 1 V steps

Megger not only manufactures andmarkets high quality test and measuringinstruments. Megger also employees astaff of people who are experts in theirfield ranging from ground testing toinsulation testing to cable fault finding.

We share this knowledge base through aseries of publications and case studies thatare yours for the asking. This issuefeatures the following documents availableon CD free of charge.

• Getting Down to Earth – The number one authority on groundtesting covering everything you everwanted to know about propergrounding and ground testingtechniques.

• Fault Finding Solutions forElectric Power Cables – A comprehensive study of variouspower cable as well as how toeffectively find faults in buriedunderground power cable.

• PowerDB Test Data ManagementTutorial – Learn more about thesoftware package that can provideyou a better, more efficient way tomanage your electrical apparatusmaintenance test data.

• Megger Product Catalog – No matter what your timing is whenit comes to budgeting for new testequipment, this product catalog willserve as a great reference tool. It includes over 200 different test sets covering applications from relaytest equipment to watthour metertest sets to a variety of substationtest equipment. Ask for your freecopy today.

All of these CDs are in stock and available now:Email: sales@megger.comPhone: 1-800-723-2861Or Fill out the attached card and mailit to us today

MPRT

As a result ofstreamlining theMPRT firmware, anew AVTS testfeature has beenintroduced calledDynamic Control.Dynamic Controlprovides easy testingof single or multi-shot reclosing relays.It also providesMulti-StateSequence testing ofrelays and relayprotection schemes.With MPRT’s 10binary inputs, 6binary outputs andAVTS 17 virtualtimers, a user cantest variouscommunication andnon-communicationbased protectionlogic schemes.The MPRT firmwarealso providescapture of theanalog waveformoutputs and

the firmware that work with the AVTS software for timing multiple relay operations.

• A new Wave Index feature provides theability to create new waveforms “on-the-fly”. Thus users will be able to adjustharmonic waveforms in real-time. Anapplication example is the testing ofharmonic restraint current differential relays.

New AVTS RIO File Import - RIO is a file formatthat defines the operating characteristic of a relay.Importing the RIO file into the Click On Fault testscreen provides a quick and easy setup of the testscreen for the relay to be tested.

New SS1 File Reader - Another new AVTS featureis the importing of State-Sequence Files (SS1) fromAspen One-Liner™ and Electrocon CAPE™ powersystem simulation software programs. CAPE andOne-Liner are used world-wide by powercompanies to model their power systems, do loadflow analysis and create relay settings. They canalso be used to create State-Sequence files, whichdefine the pre-fault load condition and simulatedfault values that relays would see in their powersystem. AVTS SS1 File Reader will read the SS1 fileand create a dynamic state sequence playback file.The relay can then be tested dynamically usingrealistic system test scenarios.

New Modbus Communications - Capability AVTSnow has the capability to communicate with relaysvia the Modbus protocol. AVTS will automaticallydownload relay settings (similar to the AVTS One-Touch™) from the relay via the Modbus addressing.This enables the user to scheme into the AVTS relaysetting screen. Test the relay without making anychanges to the relay by monitoring a Modbusaddress from the relay.

Doble Test Result Import – AVTS now reads theDoble test result files and import them into theAVTS database for record keeping and reportgeneration.

AVTS now includes a protected 50/60 Hertzvariable selection. It sets the default frequency foreither 50 or 60 Hertz depending on a user’s defaultpreference. The user sets this one time and fromthere on the default test windows will be set to thedesired system frequency.

Summary

These new capabilities and improvements make theMPRT one of the leaders in the sophisticated worldof relay testing. The MPRT will continue to evolveas our team of Megger design engineers introduceadditional hardware, firmware and softwareadvancements. Their objective is to provide youwith the finest, high performance protective relaytest set in the industry.

2

XApplicationsMIT Models 400, 410, 420 and 430Industrial and Power Electrical Installation Testing:These models include all the features required for electricians, technicians and engineers working in a range of industries. Available features are selected to make testing easyand fast in a range of situations. Typical applications include:

� Building/Campus electrical maintenance� Large and small scale electrical installations� Periodic electrical systems inspection and testing� Cable testing Service, Repair and Maintenance:The MIT Models 410, 420 and 430 add additional featuresrequired for technicians and engineers working on moredemanding applications. Functions such as PI and DAR,capacitance measurement and a higher insulation range increasethe suitability for applications such as:

� Plant maintenance and production testing� Panelboard testing� Railway and other transportation maintenance

and testing� Motor testing� Cable inspection/quality control� Street lighting maintenance� Avionics ground testing and maintenance� Military hardware and facility maintenance

MIT Models 480, 481 and 485Telecommunication TestingDesigned to satisfy the additional requirements of thetelecommunications industry, MIT Models 480, 481 and 485include 50 V and 100 V range insulation testing as standard, plushigher voltages as required.

In addition, the voltage detection test inhibit feature has beenraised to 75 V (from 50 V), to allow testing of cables withcoactivity coupled induced voltages, which would normally inhibitsuch testing with a 50 V protected instrument.

Finally the MIT481 and MIT485 models include measurement ofcable distance by capacitance, providing a convenient cable lengthwithout the need to use TDR technology, with adjustable cablecapacitance from 40 nF/Km to 60 nF/Km (default is 50 nF/Km).

MIT400 Series, cont. from page 1.

MPRT, cont. from page 1.

The “X Model”Insulation

Tester is here!It’s the instrument that can handle the most unusualmeasurement requirements. We call it the Model MIT40X“special applications” instrument, for those who need aunique test voltage.

The “X Model” offers a variable insulation test voltagefrom 10 V to 100 V applications in 1 V steps, providing asolution to practically any unusual measurement

requirement you may have.

For example, typical applications include but are not limited to:

• Commercial avionics testing

• Military land, marine and air communications testing

• Manufacturing / production line testing

• Electrostatic test and measurement (see photo above)

• Component testing

• Battery powered traction and lifting equipmenttesting

The possibilities are endless and it’s only available with the“X Model” (Model MIT40X).

Electrostatic test using the Megger MIT40X.

AND LAST BUT NOT LEAST!

The MIT40X is unusual enough to warrant aseparate overview of this very unique product…see the side bar article at right.

time-tags the binary inputs / outputs. At thesame time, AVTS software uses this capabilityto display the voltage and current outputwaveforms in time sequence with the binaryinputs and outputs. This is used whenperforming multi-shot reclosing tests. It alsorecords Sequence of Events for StateSequence testing of relays and relayprotection schemes. It may also be used tocapture complex output waveformsgenerated by the Wave Index feature (in thepast a user had to generate complexwaveforms, but did not know what theylooked like without using an external scope).

Additional New CapabilitiesNew AVTS Click-On-Fault (COF) Feature - The user can define the type of operatingcharacteristic using the AVTS Theo Import, or RIO Import, then click at a point on thecharacteristic that they wish to test for, either as a Shot, a Check Point or using the click-and-dragSearch feature.

The Power of Knowledge

3

Lease to Own Program

Megger DELTA 2000 Power Factor Test Set

Don’t just lease it…”Lease to

Own” it! It saves significant

money, it’s customizable and

guarantees you equipment

ownership in a very

reasonable period of time

WITHOUT costing you

additional money!

Finally…now you have some

really solid and attractive

alternatives to consider your

future course of action with

power factor testing.

Consider the following:

� Choose our popular DELTA 2000 Power FactorTest Set OR our BRAND NEW DELTA 3000

� Membership in our exclusive Priority Access Program

� New, customizable Lease to Own programFor more information see the article below, “Kick the Long Term Leasing Habit for Good!”

Here are the details:

� Choice of power factor test sets:DELTA 2000 10 kV Automated Insulation PowerFactor Test Set• Extremely easy to use, without any extensive hardware

or software set-up• Designed to work in high interference switchyards up

to 765 kV• Built-in capability for storing, printing and

downloading test results• Rugged, portable design for field/shop use

New DELTA 3000 10 kV Automated Test Set• All the features of the DELTA 2000, plus PowerDB

inside• PowerDB software interface programmed into the test

set with on-screen forms for capturing test results• Automatically sequences through multiple tests• Test results stored on USB memory sticks for import

into PowerDB• Eliminates the need to take a PC into the field

New optionsto consider when reviewing your future powerfactor test set leasing or purchase requirements

Kick the Long Term Leasing Habit for Good!the test equipment and there are no more lease payments.Imagine the impact of this. After only a few lease payments(no larger than what you are spending on your current leaseprogram), you can start spending your savings on somethingelse.

It also provides you with choices. You can buy other neededtest equipment. Or, you might decide to purchase neededaccessories for your power factor test set such as an oil testcell or a calibration standard. Finally, you might decide to buyanother power factor test set.

Customize this plan to fit your needs

The terms of your Lease-to-Own plan can be as flexible asyou want to make them, and to fit your particular financialsituation.

For instance, consider this real life example:

A customer recently designed their plan to make just twolease payments over a term of 13 months, after which theequipment was owned outright by them. And those twolease payments were essentially the same amount as they had been paying on their original, never-ending annual leasearrangement!

That’s just one example. Maybe you would prefer to makemonthly payments. Or, perhaps would prefer lower annualpayments over a longer period of time so you can reduce yourcost right away. Regardless of your current budget situation,you can create your own Lease-to-Own plan that’saffordable and fits your precise needs.

Now, that’s the easy way to kick the long term leasing habit!

Isn’t it time to change how you lease a powerfactor test set?

We all know leasing test equipment can be a very expensivehabit. Money from your operating expense budget is spentyear-after-year in order to keep test equipment available whenit is needed.

This is really the norm when it comes to power factor testing. An annual equipment lease has become the standard practicefor those users, almost without exception. We think nothingof spending $20,000 or more per year – per test set – with noend in sight!

The other alternative to kicking this long term leasing habit is toconsider an outright purchase of the test equipment you need.Yes, this will eliminate those constant annual lease payments.However, a power factor test set is expensive enough thatapproval for that size “capital” expenditure may be next to impossible.

A new, better alternative

It’s time to consider this option…a Lease-to-Own plan. Thistype of plan still allows you to make a series of lease paymentsusing money from your expense budget. But the difference is,there’s an end to those lease payments, at which time you own

• Extended Warranty CoverageReceive extended warranty coverage on your DELTA 2000 foreach year that you commit to this program (refer to theservice agreement for complete details).

• Rental Discounts on Other EquipmentReceive special discounts on rental of other Meggerequipment, as necessary.

� Priority Access ProgramPriority Access provides specific guaranteed support and valuableservices to assure you get full utilization of either the DELTA 2000or DELTA 3000 Test Set.

This exclusive program includes:• Priority Technical Support and Consultation Services

You are provided direct access to an experienced technicalresource pool via telephone on a 24/7 basis. Applicationengineers are on call to provide you support with analysis of testresults, testing procedures and answer questions about variouselectrical apparatus.

• Customized On-Site TrainingExpert product/application training is provided for up to 2 fulldays at your site or the Megger Dallas facility during the first year.

• PowerDB Software Package60 day free trial of PowerDB software including a start-up 2 houronline tutorial.

• Annual Equipment Calibration and Certification ServiceWe will perform an annual equipment calibration andcertification service on your DELTA 2000 at no charge. (This service should be scheduled in advance and does notinclude the cost of freight involved in this service).

• Priority Repair ServicesIf you ever experience a problem with a DELTA 2000, there is nocharge for any standard repair service (excluding freight charges).In addition, we guarantee a fast 5 day turnaround time on allrepairs.

• Quick Loaner Replacement Test Set. . . Anytime, AnywhereKeep any downtime to a minimum with the security of knowingif you ever experience a problem with your test set, one call willhave a loaner replacement unit on its way to you within 24hours.

• Firmware and Software UpgradesReceive all firmware and software upgrades at no charge.

• Discounted AVO Institute Training on Substation CoursesTraining is provided at a greatly reduced discount rate at the AVOTraining Institute located in Dallas, Texas.

All training is performed by knowledgeable application engineerswith over 100 years of hands-on field testing experience.

4

Additionally, all four models feature extra noise rejection capability,with Models S1-554 and 1054 providing an industry best (4 mAnoise rejection). This virtually eliminates the possibility of poor,unreliable or unstable readings being made in noisy 400 kV andabove substations or switchyards.

All four models are heavy duty and are reliable with features thatmeet the most demanding high voltage testing applications inexistence today.

High Noise Rejection• Problem free operation in high voltage yards and stations• S1-552 and 1052 – 2 mA noise immunity• S1-554 and 1054 – 4 mA noise immunity

Highest Charging Current in the Industry 5 mA• Fast, repeatable measurements on difficult capacitive

equipment like large motors, generators and cables

Burn Mode• Conditions hidden faults • Locates problems easier and faster

Data Storage and Download• Includes easy to use software• Accurate and easy to maintain record keeping• Battery or Line Operation• Ready to test even with exhausted battery

S1 Series, cont. from page 1.

The Megger MDP Series of

distribution profilers provides

power utilities with the most

accurate and extensive

information ever to precisely

evaluate loading on

feeders/overhead lines and to

identify needed upgrades or

replacement. Three different

models range from a simple

“current-only” version to the

most advanced unit that offers a

number of market-requested

features. Each MDP can be easily

upgraded to the next model at

any time.

Introducing today’s most advanced

DistributionProfiler

MDP1 (basic)Records actual current RMSmagnitude up to 1000 amps, withan additional 200 amp over-range

MDP2 (mid range)Records:• Actual current RMS magnitude

up to 1000 amps, with anadditional 200 amp over-range

• Relative voltage RMS magnitude• Power factor and power

MDP3 (advanced)Records:• Actual current RMS magnitude

up to 1000 amps, with anadditional 200 amp over-rangeand waveform capture

• Relative voltage RMS magnitudeand waveform capture

• Power factor and power• Harmonics• THD (Total Harmonic Distortion)

Specifically designed to bequickly installed on adistribution line

The Profilers are quickly installed atany point on the distribution line. Anarrow on the back of the MDP unitshould point towards the load. Sinceall units are mechanically identical andweigh less than 4.6 lbs (2.1 kg), theyare easily mountable to many readily

available clamp sticks for installationon live lines. Cable diameters from0.2 in. to 1.2 in. (.5 cm to 3.0 cm)can be accommodated.

Features you can’t findelsewhere

Virtually unlimited data recording– Depending on the RMS storageinterval selected, the Profiler canrecord for days, weeks, or evenmonths. The unit offers virtuallyunlimited data recording/storagecapacity with no potential loss, evenwith battery failure.

Wide range of data recordingoptions – Record necessary dataranging from a simple survey study toa complete circuit analysis includingconductor sizing and capacitorplacement.

Effective performance andprotection – Each Profiler performseffectively when in direct exposure toall weather conditions. The moldedunit offers the greatest protectionagainst either ingress, a major issueencountered by power utilities usingother line recording devices.

Easy battery replacement andplug-in access – Lightweight, durableunit with simple plug-in access andtrouble-free battery replacement.

Easy installation – The light weight ofthe Profiler allows for quick and easyinstallation on live lines. It is easilymountable to many readily availableclamp sticks.

Easily acquire extensive line data

Powerful internal software allows fast,easy acquisition of data you need toknow. Features include:

• Easy, fill-in-the-form instrumentsetup and configuration

• Data retrieval from up to 4Profilers at a specific site, mergedinto one data file

• Specific data file location usingthe integrated search function

• Voltage/current and demand datachart access

• Harmonic and waveform analysis• Individual harmonics, THD,

frequency and imbalance charting• Zoom/unzoom on specific

graphical areas of interest• Several built-in analysis reports

MeggerDistributionProfiler Series

Complete Range of Measurements• Capacitance• Leakage Current• Actual applied voltage

Built-In Industry Standard TestsPI Polarization Index

• Meets IEEE, NETA and ANSI Standards• Eliminates need for temperature correction

SV Step Voltage• Safely perform Overvoltage Tests

DD Dielectric Discharge• Identify problems in multilayer insulation

IR Insulation Resistance• Built in timer means fast and accurate testing

DAR Dielectric Absorption Ratio• Easily perform dielectric absorption ratio tests

Overall Easier Operation• “Quick Start” guide located in the lid

Extended Measurement Ranges• 15TΩ (S1-552/554)• 35TΩ (S1-1052/1054)

Multiple Built-in Safety Features• Meets EN61010 safety requirements• Live voltage warning• Safety lockout over 50 V on 5 kV testers and

80 V on 10 kV testers• Automatic energy discharge• Line or battery operation

INTERCELL

VRLA

BASICS

5

batteries are innumerable and frequently unseen. In this worldof dependency upon electricity, it is impossible to survivewithout battery back-up.

Battery Basics

So what makes a battery tick? All batteries, whetherrechargeable (secondary) or disposable (primary), use chemicalreactions to make electricity. It is necessary to have twodissimilar metallic materials in a current-carrying medium. Inlead-acid batteries, the two dissimilar metallic materials arelead and lead oxide in a sulphuric acid medium. NickelCadmium batteries use nickel and cadmium compounds in apotassium hydroxide electrolyte medium. Nickel Metal Hydride(NiMH) is comprised of the same nickel compound as in NiCdcells but the cadmium compound is replaced with a metallichydride and the liquid electrolyte is replaced with a paste tocarry the current. The two types of nickel cells are virtuallyidentical in performance. Even their voltages are the same!Lithium uses a lithium-containing oxide or phosphate andcarbon. For the purposes of stationary battery testing, thisarticle focuses on lead-acid batteries.

So now that we know the importance of batteries, a little bitabout their chemistry (and don’t forget safety) information,how do we know if they are good or bad? The age-oldprinciple of testing only the voltage and specific gravitydoesn’t work, never has, never will. Here’s why: the sum of allof the cells’ voltages must equal the charger output. Voltage(and specific gravity) of lead-acid batteries basically follows thesulphate. If a battery is fully charged, the sulphate will be inthe acid and its voltage and specific gravity will be normal(with few exceptions.) If it is in a discharged state, the voltagewill be low and since there is at least some sulphate on theplates, the specific gravity will also be low. If the battery has anormal voltage, there is no indication of the condition of thebattery. When the voltage is abnormal, it may be anindication of a potential problem.

Nickel Cadmium batteries behave somewhat differently thanlead-acid. In lead-acid, the acid actually is part of theelectrochemical process; it reacts with the lead and lead oxideto make electricity. The KOH electrolyte in NiCd is simply acarrier for the current and does not enter the chemicalreaction. Therefore, measuring specific gravity of NiCdbatteries in service doesn’t indicate anything about thecondition of the battery. The one exception is carbonation ofthe electrolyte. This is caused over time by the absorption ofcarbon dioxide from the air into the KOH and will reduce thespecific gravity of the electrolyte. If this happens, check withthe battery manufacturer. It may simply be a matter ofreplacing the electrolyte.

Battery Tests

The range of tests on a battery encompasses nothing (not agood idea) to everything (still not a good idea). The actualtests are voltage, specific gravity, float current, ripple current,cell temperature, ambient temperature, discharge current andtime, intercell connection resistance, capacity (a.k.a. load test),impedance (an internal ohmic test), among others as requiredby various authorities.

Float Voltage

Taking them one at a time, voltage can be one of thosemisleading tests. Voltage is important, absolutely, and if it isabnormal, then it indicates something about the condition ofthe battery. If it is normal, it indicates nothing at all about abattery’s condition. This is because voltage is more of anindicator that the charger is functioning properly. The sum ofthe voltages of all of the batteries in the bank must equal thecharger output, resistive losses excluded. There are a numberof references1, 2 to reinforce the idea that a normal voltage isnot an indicator of battery capacity yet an abnormal voltageneeds further investigation.

Specific Gravity

Specific gravity is similar to voltage. The sulphate is part of theelectrochemical reaction. If the battery is discharged, some ofthe sulphate migrates to the plates and the acid is reduced inspecific gravity. If the battery is fully charged, all of thesulphate is in the acid and the specific gravity is normal, say1.215. There aren’t any studies to validate any correlationbetween specific gravity and battery capacity. In fact, IEEE 450has de-emphasized specific gravity to the point of checkingonly 10% of the batteries each quarter and the full bankannually.

Float Current

In order to keep a battery charged, there is a battle of sorts inthe battery between its self-discharge and the charger. Thebattery is always in a state of self-discharge which creates adifferential in potential between the battery bank and thecharger. This differential in potential causes a small current toflow to keep the battery fully charged. This dc current is calledfloat current.

In flooded lead-acid batteries, there is no such thing asthermal runaway since the liquid acid cools the batterythrough the process of evaporative cooling. However, VRLAbatteries do not have extra acid, nor is it in a free liquid form.

If the float current increases due to some impending failure orovercharging condition, the temperature increases3. The increasedtemperature allows for more current to flow and further increasesthe temperature of the battery. It becomes a runaway chemicalreaction which can lead to the melting of the battery causing anopen circuit. The time frame between when the float current startsto increase and when thermal runaway can occur is from one tofour months. Float current is an important parameter to measurein VRLA batteries.

Ripple Current

Ripple current is an artifact of the charger which is designed toconvert ac into dc. No charger has a 100% efficient conversionprocess which is why filters are frequently added to certainapplications. Ripple current generally increases slowly over time aselectronic components degrade. If, however, a diode blows, theripple current can double. As with float current, an increase inripple current to a point greater than about 5 amps rms for every100Ah of battery capacity (5%) leads to increased temperatureand shortened battery life. Ripple current is another parameter thatshould be measured periodically.

Temperature

Battery and ambient temperature, although they don’t dictateimmediate doom for a battery, can lead to premature failure. Everyincrease of 10° C in battery temperature, the battery life is halved.This then means that a 20 year battery maintained at 35° Cinstead of the specified 25° C will only last about ten years. In

Europe the standard temperature is 20° C and 15 year design lifefor flooded batteries.

Discharge Current and Time

Discharge current and time is being used more frequently in on-linemonitors to aid in determining Amp-hours removed and replaced.The value of measuring current and time and calculating Ahremoved and replaced is that battery capacity can presumably becalculated. This author believes that there is value in this calculation.The caveat is discussed below under capacity (load) tests.

Intercell Connection Resistance

Intercell connection resistance is one of those tests that truly needsto be performed, especially if frequent outages occur. It has beensaid that more than 50% of battery bank failures are due to looseintercell connectors. It is a straightforward test that can be done inconjunction with impedance (discussed below) or as a stand-alonetest using a Low Resistance Ohmmeter.

Intercell connections come loose due to heating and cooling cyclescaused by discharging and recharging as a result of outages. Theposts expand and contract and lead being very malleable will “coldflow” with each cycle. This is one of the reasons that batterymanufacturers tend to recommend tightening bolts to the low endof the torque range so as not to add further stress during cycling.

Capacity tests have long been a necessary evil. If performedproperly, they are expensive, time-consuming and have limitedpredictive value depending upon their frequency. Let’s take for themoment a battery bank that is designed to provide eight hours ofback up time. A proper capacity test incorporates a second batteryin the event of an ac outage during the discharge test. This secondbattery must be at least the same size or bigger than the mainbattery being tested. The resistive load bank must be connected tothe main battery bank and voltage leads are connected to eachbattery in the bank. This is usually day #1. On day 2, the eighthour test begins. Frequently, a test for intercell connectionresistance is performed before the start of the capacity test. Thereare two schools of thought about performing the intercellconnection resistance test: 1) it is not representative of a true “asfound” autonomy test and 2) certain precautions need to be takento ensure that no major malfunctions occur that could have beenavoided. If there are major malfunctions, then the bank or at leastsome of the batteries will need to be replaced in an emergencysituation. This decision is for those at each company who writeprocedures and maintain batteries. Day 3 is the continuation of the

Batteries, cont. from page 1. recharge of the main bank. The voltage leads are removed

and the resistive load bank is disconnected and returned. Themain battery recharge continues on day 4 or may be fullyrecharged and ready for service. A properly run capacity test isthe only true method of determining the bank’s actualcapacity.

Impedance, an internal ohmic test, is a measure of thecapability of a cell to deliver current. It is correlated tocapacity. Although correlation to capacity is not 100%, it isexcellent at finding weak batteries in the bank. The EPRI study4

reveals how well impedance and other internal ohmic testswork in finding weak cells. Impedance applies and measuresan ac current signal and measures simultaneously the acvoltage drop across a battery caused by the ac current signal.Following Ohm’s law, Z = E/i, impedance is calculated.Impedance is inversely proportional to capacity in that ascapacity decreases, impedance increases. This test is fast(about 30 minutes for a 60-cell substation battery bank) and isnon-invasive.

Data Analysis

What is one to do with all of these data? How do the dataget interpreted to ensure that the battery bank will meet theduty cycle? With the advent of better testing methods such asimpedance, currents, etc., more useful data (rather thanvoltage and specific gravity) can now be obtained. With muchdata come the data-handling problem and analysis paralysis.

The recommended method is to use a database to track andtrend all battery data over time and dispense with forms thatdon’t compare today’s data with yesterday’s data. A specialiseddatabase, one with space for all measured parameters, isimportant to aid in determining the condition of batteries andbanks.

By entering limits, with which the user is comfortable in orderto gain the most life from a battery without increasing risk,aids tremendously in extracting the most from a battery. Thelimits should be set for each parameter measured. Forexample, float voltage limits should follow manufacturers’guidelines. Internal ohmic test limits are more debatable. Insome cases, users will set a “failure limit” of 50% impedanceincrease for VRLA batteries from a predetermined baselinevalue. Float current limits tend to be less precise dependingupon the size, age and alloy of the battery.

Conclusion

There are many failure modes in batteries. With care andmeasurements, these can be dramatically reduced, especially iflittle to no testing is being performed today. Remember, thebattery is installed, not to add to one’s work load, but tosupport critical electrical equipment or revenue streams.Proper testing and data analysis can help determine when abattery should be replaced. Testing regimes also help reduceemergency battery replacements and assist in budgetaryplanning, thus reducing cost. A properly implemented batterytesting regime does not necessarily reduce the work load andit will, most likely, increase reliability of the entire dcnewtwork.

1 Stationary Battery Monitoring by Internal OhmicMeasurements, EPRI, Palo Alto, CA, 2002. Report No.1002925

2 “Lead Acid Battery Periodic Measurements – What Does theData Mean?”, Tom Ruhlmann, Power Quality ConferenceProceedings 2002, pp176-187.

3 “An Investigation into the Effects of Abuse Charging andThermal Runaway in VRLA Batteries”, Culpin, B., Wainwright,P.L., Intelec, 2001, Edinburgh, Scotland.

4 Stationary Battery Monitoring by Internal OhmicMeasurements, op. cit.

Testing a battery bank with the Megger DLRO200

6

The 2005 edition of the National ElectricalCode, Section 110.16 titled “Flash Protection”states “Switchboards, panelboards, industrialcontrol panels, and motor control centers thatare in other than dwelling occupancies and arelikely to require examination, adjustment,servicing, or maintenance while energized shallbe field marked to warn qualified persons ofpotential electric arc flash hazards. The markingshall be located so as to be clearly visible toqualified persons before examination,adjustment, servicing, or maintenance of theequipment.”

“FPN No. 1: NFPA 70E-2004, Standard forElectrical Safety in the Workplace, providesassistance in determining severity of potentialexposure, planning safe work practices, andselecting personal protective equipment.”

Figure 1 is an illustration of the minimum labelthat NEC 110.16 requires; Figure 2 is anillustration of the recommended label.

Figure 1. NEC 110.16 Required Label

Figure 2. Recommended Label

One of the key components of the Flash HazardAnalysis, which is required by NFPA 70E-2004, isthe clearing time of the protective devices,primarily circuit breakers, fuses, and protectiverelays. Fuses, although they are protectivedevices, do not have operating mechanisms thatwould require periodic maintenance; therefore,this paper will not address them. The primaryfocus of this paper will be the maintenanceissues for circuit breakers and protective relays.

Molded case and low-voltage power circuitbreakers (600-volts or less) will generally clear afault condition in 3 to 8 cycles. To beconservative a clearing time of 8 cycles shouldbe used. The majority of older medium-voltagecircuit breakers (2300-volts or greater) will cleara fault in around 8 cycles with the newer onesclearing in 3 to 5 cycles. Protective relays willgenerally add approximately 3 to 4 cycles to theclearing time of the medium circuit breaker.Where proper maintenance and testing are notperformed, extended clearing times could occurcreating an unintentional time delay that willaffect the results of flash hazard analysis.

All maintenance and testing of the electricalprotective devices addressed in this article mustbe accomplished in accordance with themanufacturer’s instructions. The NFPA 70BRecommended Practices for Electrical EquipmentMaintenance as well as the NETA “MaintenanceTesting Specifications for Electrical PowerDistribution Equipment and Systems” is anexcellent source of information for performingthe required maintenance and testing of thesedevices. Visit the NETA website for moreinformation at http://www.netaworld.org.

This article will address some of the issuesconcerning proper maintenance and testing ofthese protective devices, according to themanufacturer’s instructions. It will also addresshow protective device maintenance relates tothe electrical arc/flash hazard.

Protective Devices Maintenance

Molded-Case Circuit Breakers

Generally, maintenance on molded-case circuitbreakers is limited to proper mechanicalmounting, electrical connections, and periodicmanual operation. Most lighting, appliance, andpower panel circuit breakers have riveted framesand are not designed to be opened for internalinspection or maintenance. All other molded-case circuit breakers that are UL approved arefactory-sealed to prevent access to the calibratedelements. An unbroken seal indicates that themechanism has not been tampered with andthat it should function as specified by UL. Abroken seal voids the UL listing and themanufacturers’ warranty of the device. In thiscase, the integrity of the device would bequestionable. The only exception to this wouldbe a seal being broken by a manufacturer’sauthorized facility.

Molded-case circuit breakers receive extensivetesting and calibration at the manufacturers’plants. These tests are performed in accordancewith UL 489, Standard for Safety, Molded-CaseCircuit Breakers, Molded-Case Switches andCircuit Breaker Enclosures. Molded-case circuitbreakers, other than the riveted frame types, arepermitted to be reconditioned and returned tothe manufacturer’s original condition. In order toconform to the manufacturer’s original design,circuit breakers must be reconditioned accordingto recognized standards. The ProfessionalElectrical Apparatus Recyclers League (PEARL)companies follow rigid standards to reconditionlow-voltage industrial and commercial molded-case circuit breakers. It is highly recommendedthat only authorized professionals reconditionmolded-case circuit breakers. Visit the PEARLwebsite for more information athttp://www.pearl1.org.

Circuit breakers installed in a system are oftenforgotten. Even though the breakers have beensitting in place supplying power to a circuit foryears, there are several things that can gowrong. The circuit breaker can fail to open dueto a burned out trip coil or because themechanism is frozen due to dirt, dried lubricant,or corrosion. The overcurrent device can fail dueto inactivity or a burned out electroniccomponent. Many problems can occur whenproper maintenance is not performed and thebreaker fails to open under fault conditions. Thiscombination of events can result in fires, damageto equipment or injuries to personnel.

All too often, a circuit breaker fails because theminimum maintenance (as specified by themanufacturer) was not performed or wasperformed improperly. Small things, like failingto properly clean and/or lubricate a circuitbreaker, can lead to operational failure orcomplete destruction due to overheating of theinternal components. Common sense, as well asmanufacturers’ literature, must be used whenmaintaining circuit breakers. Mostmanufacturers, as well as NFPA 70B, recommendthat if a molded-case circuit breaker has notbeen operated, opened or closed, eithermanually or by automatic means, within as littleas six months time, it should be removed fromservice and manually exercised several times.This manual exercise helps to keep the contactsclean due to their wiping action and ensures thatthe operating mechanism moves freely. Thisexercise however does not operate themechanical linkages in the tripping mechanism(Figure 3). The only way to properly exercise theentire breaker operating and trippingmechanisms is to remove the breaker fromservice and test the overcurrent and short-circuittripping capabilities. A stiff or sticky mechanismcan cause an unintentional time delay in itsoperation under fault conditions. This coulddramatically increase the arc/flash incidentenergy level to a value in excess of the rating ofpersonal protective equipment. There will bemore on incident energy later in this article.

Figure 3. Principle Components of a Molded-CaseeCircuit Breaker

Another consideration is addressed by OSHA in29 CFR 1910.334(b)(2) which states:

“Reclosing circuits after protective deviceoperation. After a circuit is deenergized by acircuit protective device, the circuit may NOT bemanually reenergized until it has beendetermined that the equipment and circuit canbe safely reenergized. The repetitive manualreclosing of circuit breakers or reenergizingcircuits through replaced fuses is prohibited.

NOTE: When it can be determined from thedesign of the circuit and the overcurrent devicesinvolved that the automatic operation of a devicewas caused by an overload rather than a faultcondition, no examination of the circuit orconnected equipment is needed before thecircuit is reenergized.”

The safety of the employee, manually operatingthe circuit breaker, is at risk if the short circuitcondition still exists when reclosing the breaker.OSHA no longer allows the past practice ofresetting circuit breaker one, two, or three timesbefore investigating the cause of the trip. Thisprevious practice has caused numerous burninjuries that resulted from the explosion ofelectrical equipment. Before resetting a circuitbreaker, it, along with the circuit and equipment,must be tested and inspected, by a qualifiedperson, to ensure a short circuit condition doesnot exist and that it is safe to reset.

Any time a circuit breaker has operated and thereason is unknown, the breaker must beinspected. Melted arc chutes will not interruptfault currents. If the breaker cannot interrupt asecond fault, it will fail and may destroy itsenclosure and create a hazard for anyoneworking near the equipment.

To further emphasize this point the followingquote from the National EquipmentManufacturer’s Association (NEMA) is provided:(Vince A. Baclawski, Technical Director, PowerDistribution Products, NEMA; published in EC&Mmagazine, pp. 10, January 1995)

“After a high level fault has occurred inequipment that is properly rated and installed, itis not always clear to investigating electricianswhat damage has occurred inside encasedequipment. The circuit breaker may well appearvirtually clean while its internal condition isunknown. For such situations, the NEMA AB4‘Guidelines for Inspection and PreventiveMaintenance of MCCBs Used in Commercial andIndustrial Applications’ may be of help. Circuitbreakers unsuitable for continued service may beidentified by simple inspection under theseguidelines. Testing outlined in the document isanother and more definite step that will help toidentify circuit breakers that are not suitable forcontinued service.

After the occurrence of a short circuit, it isimportant that the cause be investigated andrepaired and that the condition of the installedequipment be investigated. A circuit breaker mayrequire replacement just as any other switchingdevice, wiring or electrical equipment in thecircuit that has been exposed to a short circuit.Questionable circuit breakers must be replacedfor continued, dependable circuit protection.”

The condition of the circuit breaker must beknown to ensure that it functions properly andsafely before it is put it back into service.

Low-Voltage Power Circuit Breakers

Low-voltage power circuit breakers aremanufactured under a high degree of qualitycontrol, of the best materials available, and witha high degree of tooling for operationalaccuracy. Manufacturer’s tests show these circuitbreakers to have durability beyond the minimumstandards requirements. All of these factors givethese circuit breakers a very high reliability rating.However, because of the varying applicationconditions and the dependence placed uponthem for protection of electrical systems andequipment as well as the assurance of servicecontinuity, inspections and maintenance checksmust be made on a regular basis. Several studieshave shown that low-voltage power circuitbreakers, which were not maintained within a 5-year period, have a 50% failure rate. (See IEEE Standard 493, Chapter 5 for additionalinformation on circuit breaker failure rates.)

Maintenance of these breakers will generallyconsist of keeping them clean and properlylubricated. The frequency of maintenance willdepend to some extent on the cleanliness of thesurrounding area. If there were very much dust,lint, moisture, or other foreign matter presentthen obviously more frequent maintenancewould be required.

Industry standards for, as well as manufacturersof, low-voltage power circuit breakersrecommend a general inspection and lubricationafter a specified number of operations or at leastonce per year, whichever comes first. Somemanufacturers also recommend this sameinspection and maintenance be performed afterthe first six months of service regardless of thenumber of operations. If the breaker remainsopen or closed for a long period of time, it isrecommended that arrangements be made toopen and close the breaker several times insuccession, preferably under no-load conditions.Environmental conditions play a major role in thescheduling of inspections and maintenance. Ifthe initial inspection indicates that maintenanceis not required at that time, the period may beextended to a more economical point. However,more frequent inspections and maintenance maybe required if severe load conditions exist or if aninspection reveals heavy accumulations of dirt,moisture, or other foreign matter that mightcause mechanical, insulation, or electrical failure.Mechanical failure would include anunintentional time delay in the circuit breakerstripping operation due to dry, dirty or corrodedpivot points or by hardened or sticky lubricant inthe moving parts of the operating mechanism.The manufacturer’s instructions must be followedin order to minimize the risk of any unintentionaltime delay.

Figure 4 provides an illustration of the numerouspoints where lubrication would be required andwhere dirt, moisture, corrosion or other foreignmatter could accumulate causing a time delay in,or complete failure of, the circuit breakeroperation.

Figure 4. Power-Operated Mechanism of aCutler/Hammer “DS” Circuit Breaker

as it

applies

to the

By Dennis K. Neitzel, CPE, AVO Training Institute

Arc/Flash Hazard

7

Medium-Voltage Power Circuit Breakers

Most of the inspection and maintenancerequirements for low-voltage power circuitbreakers also apply to medium-voltage powercircuit breakers. Manufacturers recommend thatthese breakers be removed from service andinspected at least once per year. They also statethat the number and severity of interruptionsmay indicate the need for more frequentmaintenance checks. Always follow themanufacturer’s instructions because everybreaker is different. Figures 5 and 6 illustratetwo types of operating mechanisms for medium-voltage power circuit breakers. Thesemechanisms are typical of the types used for air,vacuum, oil and SF6 circuit breakers. As can beseen in these figures, there are many points thatwould require cleaning and lubrication in orderto function properly.

Figure 5. Operating Mechanism Air Circuit Breaker

Figure 6. Solenoid-Operated Mechanism

Protective Relays

Relays must continuously monitor complexpower circuit conditions, such as current andvoltage magnitudes, phase angle relationships,direction of power flow, and frequency. Whenan intolerable circuit condition, such as a shortcircuit (or fault) is detected, the relay respondsand closes its contacts, and the abnormalportion of the circuit is deenergized via thecircuit breaker. The ultimate goal of protectiverelaying is to disconnect a faulty system elementas quickly as possible. Sensitivity and selectivityare essential to ensure that the proper circuitbreakers are tripped at the proper speed to clearthe fault, minimize damage to equipment, andto reduce the hazards to personnel.

A clear understanding of the possible causes ofprimary relaying failure is necessary for a betterappreciation of the practices involved in backuprelaying. One of several things may happen toprevent primary relaying from disconnecting apower system fault:

• Current or voltage supplies to the relaysare incorrect.

• DC tripping voltage supply is low or absent.

• Protective relay malfunctions.• Tripping circuit or breaker mechanism

hangs up.

There are two groups of protective relays:primary and backup. Primary relaying is the so-called first line of defense, and backup relayingis sometimes considered to be a subordinatetype of protection. Many companies, however,prefer to supply two “lines” of relaying and donot think of them as primary and backup. Figure7 illustrates primary relaying. Circuit breakers arefound in the connections to each power systemelement. This provision makes it possible todisconnect only the faulty part of the system.Each element of the system has zones ofprotection surrounding the element. A faultwithin the given zone should cause the trippingof all circuit breakers within that zone and notripping of breakers outside that zone. Adjacent

zones of protection can overlap, and in fact, thispractice is preferred, because for failuresanywhere in the zone, except in the overlapregion, the minimum numbers of circuit breakersare tripped.

In addition, if faults occur in the overlap region,several breakers respond and isolate the sectionsfrom the power system. Backup relaying isgenerally used only for protection against shortcircuits. Since most power system failures arecaused by short circuits, short circuit primaryrelaying is called on more often than most othertypes. Therefore, short circuit primary relaying ismore likely to fail.

FIGURE 7. Primary Relaying for an Electric PowerSystem

Voltage and current transformers play a vital rolein the power protection scheme. Thesetransformers are used to isolate and protect bothpeople and devices from high voltage, and toallow current carrying devices such as relays,meters, and other instruments to have areasonable amount of insulation. It should beclearly understood that the performance of arelay is only as good as the voltage and currenttransformers connected to it. A basicunderstanding of the operating characteristics,application, and function of instrumenttransformers is essential to the certified relaytechnician.

Some overcurrent relays are equipped with aninstantaneous overcurrent unit, which operateswhen the current reaches its minimum pickuppoint (see Figure 8). An instantaneous unit is arelay having no intentional time delay. Should anovercurrent of sufficient magnitude be applied tothe relay, both the induction disc and theinstantaneous unit will operate. However, theinstantaneous unit will trip the circuit breaker,since it has no intentional time delay. In Figure 6,the operating coil is in the AC portion of therelay in series with the induction coil. Thecontacts are directly across the trip circuit and thespiral spring is never involved in the trippingaction.

FIGURE 8. Instantaneous Trip Unit

The instantaneous trip unit is a small, AC-operated clapper device. A magnetic armature,to which leaf-spring-mounted contacts areattached, is attracted to the magnetic core uponenergization. When the instantaneous unitcloses, the moving contacts bridge two stationarycontacts and complete the trip circuit. The corescrew, accessible from the top of the unit,provides the adjustable pickup range. Newerdesigns also feature tapped coils to allow evengreater ranges of adjustment.

The instantaneous unit, like the ICS unit, isequipped with an indicator target. This indicationshows that the relay has operated. It is importantto know which relay has operated, and no relaytarget should be reset without the supervisor’sknowledge and permission.

As can be seen, several things can go wrong thatwould prevent the instantaneous unit from

operating properly. These things include an openor shunted current transformer, open coil, or dirtycontacts. Protective relays, like circuit breakers,require periodic inspection, maintenance, andtesting to function properly. Most manufacturersrecommend that periodic inspections andmaintenance be performed at intervals of one totwo years. The intervals between periodicinspection and maintenance will vary dependingupon environment, type of relay, and the user’sexperience with periodic testing.

The periodic inspections, maintenance, andtesting are intended to ensure that the protectiverelays are functioning properly and have notdeviated from the design settings. If deviationsare found, the relay must be retested andserviced as described in the manufacturer’sinstructions.

Flash Hazard Analysis

Maintenance and testing is also essential toensure proper protection of equipment andpersonnel. With regard to personnel protection,NFPA 70E-2004 requires a flash hazard analysisbe performed before anyone approaches exposedelectrical conductors or circuit parts that have not

been placed in an electrically safe workcondition. In addition it requires a flashprotection boundary be established. Allcalculations for determining the incident energyof an arc, and for establishing a flash protectionboundary, require the arc clearing time. Thisclearing time is derived from the engineeringcoordination study which is based on what theprotective devices are supposed to do.

If, for example, a low-voltage power circuitbreaker had not been operated or maintainedfor several years and the lubrication had becomesticky or hardened, the circuit breaker could takeseveral additional cycles, seconds, minutes, orlonger to clear a fault condition. The followingare specific examples:

Two Flash Hazard Analyses will be performedusing a 20,000-amp short-circuit with theworker 18 inches from the arc:

1. Based on what the system is supposed todo: 0.1 second (6 cycles)

2. Due to a sticky mechanism the breakernow has an unintentional time delay:0.5 second (30 cycles)

Example #1:

EMB = maximum 20 in. cubic box incident energy, cal/cm2

DB = distance from arc electrodes, inches (for distances 18 in. and greater)

tA = arc duration, seconds

F = short circuit current, kA (for the range of 16 kA to 50 kA)

(1) DA = 18 in.

(2) tA = 0.1 second (6 cycles)

(3) F = 20kA

EMB = 1038.7DB-1.4738 tA [0.0093F2 - 0.3453F + 5.9675]

= 1038 x 0.0141 x 0.1[0.0093 x 400 - 0.3453 x 20 + 5.9675]

= 1.4636 x [2.7815]

= 4.071 cal/cm2

NFPA 70E-2004, Table 130.7(C)(11) requires Category 1 protection (FR shirt and FR pants or FRcoverall) plus a hard hat and safety glasses.

Example #2:

EMB = maximum 20 in. cubic box incident energy, cal/cm2

DB = distance from arc electrodes, inches (for distances 18 in. and greater)

tA = arc duration, seconds

F = short circuit current, kA (for the range of 16 kA to 50 kA)

(1) DA = 18 in.

(2) tA = 0.5 second (30 cycles)

(3) F = 20kA

EMB = 1038.7DB-1.4738 tA [0.0093F2 - 0.3453F + 5.9675]

= 1038 x 0.0141 x 0.5[0.0093 x 400 - 0.3453 x 20 + 5.9675]

= 7.3179 x [2.7815]

= 20.3547 cal/cm2

NFPA 70E-2004, Table 130.7(C)(11) requires Category 3 protection (cotton underwear plus FR shirt and FR pants plus

FR coverall, or cotton underwear plus two FR coveralls) Category 3 also requires a hard hat, safety glasses or

goggles, flash suit hood, hearing protection, leather gloves, and leather work shoes. [6]

If the worker is protected based on what thesystem is supposed to do (0.1 second or 6 cycles)and an unintentional time delay occurs (0.5second or 30 cycles), the worker could beseriously injured or killed because he/she wouldnow be under protected.

As can be seen, maintenance is extremelyimportant to an electrical safety program.Maintenance must be performed according tothe manufacturer’s instructions in order tominimize the risk of having an unintentional timedelay in the operation of the circuit protectivedevices.

Summary

With the proper mixture of common sense,training, manufacturers’ literature and spareparts, proper maintenance can be performed andpower systems kept in a safe, reliable condition.Circuit breakers, if installed within their ratingsand properly maintained, should operate trouble-free for many years. However, if operated outsideof their ratings or without proper maintenance,catastrophic failure of the power system, circuitbreaker, or switchgear can occur causing not onlythe destruction of the equipment but seriousinjury or even death of employees working in the area.

Dennis K. Neitzel, CPE (Senior Member, IEEE) Mr.

Neitzel is the Director of AVO Training Institute, Inc. (a

Subsidiary of Megger); Dallas, Texas. Mr. Neitzel earned

his Bachelor’s degree in Electrical Engineering

Management and his Master’s degree in Electrical

Engineering Applied Sciences. He is an active member

of IEEE, ASSE, NFPA, AFE, and IAEI. He is a Certified

Plant Engineer and a Certified Electrical Inspector. Mr.

Neitzel serves as a Principal Committee Member for the

NFPA 70E, "Standard for Electrical Safety in the

Workplace", is co-author of the Electrical Safety

Handbook, McGraw-Hill Publishers, and is the Working

Group Chairman for revising IEEE Std. 902 (the Yellow

Book), “IEEE Guide for Maintenance, Operation, and

Safety of Industrial and Commercial Power Systems”.

Mr. Neitzel serves as the Vice-Chairman of the IEEE-

PPIC-TSSC Sub-Committee and also serves as a member

of the ASSE Body of Knowledge Committee. He

received the Engineering Practice Specialty “Safety

Professional of the Year” award for 2003-2004 and the

Southwest Chapter, “Jesse Locke Member Safety

Award” for 2006 from the American Society of Safety

Engineers. He has authored, published, and presented

numerous technical papers and magazine articles on

electrical safety, maintenance, and training. Contact Mr.

Neitzel at dennis.neitzel@avotraining.com.

8

When you work in the role of technical supportyou tend to get exposed to some verychallenging situations. That has been thisApplication Engineer's experience. When alineman throws in the towel and picks up a cellphone to ask for help you know that he hasexhausted all options. After all ‘real’ mendon't stop to ask for directions!

One of the most typical challenges that wereceive from our customer’s is the elusive cablefault that will not ‘thump’. This is a typicalproblem with faults within a splice, blow-outswith either burnt back conductors or neutralsand bolted (solid short) faults. In all threesituations the problem lies within the gapdistance between the conductor and neutral.

The sole basis of ‘thumping’ and high voltageradar techniques is to create an arc or highvoltage breakdown at the point of the fault.The breakdown that is established reduces theimpedance of the fault allowing the cable radarto reflect a pulse off the arc that is produced.In the case of splice faults or burnt-backconductors or neutrals, the distance betweenthe conductor and neutral (gap) may beexcessive.

When a proof test or high potential test isperformed the meters indicate a fault toground; excessive leakage current and low tono voltage can be sustained. This test confirmsthat the cable is faulted by the measurement ofexcessive leakage current, but does not indicatethe condition of the gap that the surgedvoltage from the 'thumper' must bridge.

When performing an Arc Reflection test areflection from the fault is never capturedbecause a suitable arc cannot be establishedacross the excessive gap. In the situation of a

What do you do with a cable fault that won’t

"THUMP"? bolted fault or solid short the problem is thatthere is NO gap. When this fault is surgedwe experience a rush of current through theshort circuit, but no arc and therefore no’thump‘.

So how are these elusive faults found? Thefirst task will be to localize the fault. TheMegger DART Cable Fault Analyzer is a verypowerful tool with many tricks up its sleeve.If the problem is a bolted fault (solid short),the DART's Time Domain Reflectometer willclearly show a negative reflection at the pointof the failure. Simply measure the distance tothis reflection to obtain an approximatelocation of the failure. A blow-out (opencircuit) will produce a significant positivereflection. Simply measure to this event tolocalize the fault. The splice is morechallenging.

If the Arc Reflection technique does notrender results, the DART can also perform theSurge Pulse (Impulse Current) fault locatingtechnique. This technique takes fulladvantage of the thumper discharged energyand will typically produce results even withexcessive gaps.

How do you pinpoint a fault that will notthump? That use to be a problem untilduring an underground workshop a seasonedcable fault veteran taught this ApplicationEngineer a new trick.

The non-thumping fault can be pinpointed byusing the receiver portion of a cablelocator/tracer kit much like the MeggerL1070. Apply breakdown surges with thethumper. At the point of the fault the peakdeflection measured on the tracer's receiverwill jump off scale. Now that's a neat trick!

Over the past year it appears that nearly 45% of my technical support calls or product

demonstrations involve unjacketed cable with corroded or open concentric. Corrosion on, or

opened, concentric neutrals will present several issues during a fault locating exercise.

Remember the concentric is designed to carry fault current; if the integrity of the concentric is

jeopardized due to open strands or high levels of corrosion the concentric may no longer

provide the lowest resistance path back to the surge generator (thumper). In this case the

fault current will follow the least resistant path which may be fence posts, phone shields, cable

TV shields, gas tracer wires, other utility cables or the damp earth itself. Take warning,

humans or animals touching the fence post, TV, waterline, etc. can be injured or killed. The

use of a surge generator (thumper) should be approached with great caution. Keep surge

levels at the lowest possible voltage and for the shortest amount of time.

Modern ‘radar’ style fault locating techniques such as Time Domain Reflectometry (TDR), Arc

Reflection and Surge Pulse Reflection (also referred to as Impulse Current) can all help in

dealing with concentric problems and reducing the risks associated with ‘thumping’ on cables

with poor concentric returns. Analyzing a TDR signature can help to identify possible

corrosion issues prior to using a surge generator (thumper). Small random reflection, typically

positive in orientation, may be observed indicating areas of high metallic resistance. It may

also be difficult to detect the end of the cable, even on relatively short cable runs, due to

excessive attenuation of the high frequency transmitted TDR pulses.

When the Arc Reflection test is performed a negative reflection will be captured at the

location of the arc or 'thump.' If corrosion is extreme or if the concentric is missing all

together the Arc Reflection test may not show any change in the TDR signature. If this is the

case the Surge Pulse Reflection (also known as Impulse Current Reflection) technique may

render better results.

If using the Surge Pulse technique on a cable with corroded concentric it is recommended to

use the external surge coupler (Megger Catalog No. 658001). The advantage of the external

coupler is that it can be connected to the conductor side of the circuit and thus reduce the

distortion typically captured when viewing the concentric side of the circuit.

A few tips to remember when using the Surge Pulse technique:

1. The Surge Pulse technique is performed with the surge generator set to a direct

surge (thump) mode position. The arc reflection filter is not used in this test.

2. The Surge Pulse technique captures the current transient, a shock wave style

pattern, created when a cable is surged (thumped). Therefore no pattern will be

seen until the cable is 'thumped.'

3. Since the patterns near the tail of the transient wave tend to be cleaner to view,

the measurement range set on the cable analyzer should be set about three times

longer than the cable's actual length.

4. The transient wave will typically travel slower than TDR pulses. Using velocity of

propagation values approximately 10 counts less than those used with TDR or Arc

Reflection will render the best measurement accuracy.

5. The Surge Pulse technique does not compensate for test leads. Remember to

subtract your equipment's test lead length from your final measurement.

Regardless of whether the fault was localized using the arc reflection test or surge pulse

reflection test safety precautions should be taken during the use of the surge generator.

Wear appropriate protective gear such as rubber overshoes or use of rubber mats.

Corroded concentric presents step potential hazards.

Dealing with

corroded or

open concentric on unjacketed under ground cablesBy Thomas Sandri, Application Engineer

Spring marks the beginning of the busiest time forunderground cable fault locating and maintenance.

Megger offers a complete line of cable fault locatingequipment that can make your cable fault locatingfaster and easier.

Megger also offers a staff of knowledgeable cablefault locating engineers who are available to answerany questions you may have.

You can reach an applications engineer at 1-800-723-2861 ext. 3519.

Finally, and most important, Megger operates threecable fault locating trailers. Each trailer holds acomplete line of Megger Cable Fault Locating gear which can be pulled directly to your locationfor demonstration purposes to you and your staff of personnel.

These trailers are currently located in northern California (San Francisco area), Houston andPhiladelphia.

Reserve your date for getting a close-up look at the latest in cable fault locatingequipment and actual live demonstrations. Call 1-800-723-2861 ext. 3591.

Underground Cable FaultLocating Season is here!

Special Terminal AdaptersYou asked for ‘em, We have ‘em.

These terminal adaptors are optional accessories used to allowthe terminals on the DET3 and DET4 units to accept alternativecable connections.

9

Approximately one year ago

Megger introduced a new generation

of ground testers. This new family

of ground testers has taken the

market by storm!

Hundreds of new testers have been sold and thousands of thenew, improved booklet on ground testing have been distributed(see side bar article on the famous booklet “Getting Down toEarth”).

Why are these products so popular? Here’s what our customers are saying:

“It’s really easy to use…and fast”• Simple one button operation• Oversized display and selector switch• Battery powered with bargraph that indicates battery

strength (eliminates downtime)• Safety rated to CAT IV, 100 V• Extra rugged…IP 54 rated

“You can select a model that fits your exact needs”• Variety of models to choose from• 2, 3 and 4 pole measurements with ground resistance,

soil resistivity and bond testing capabilities

“There are no add-ons or extras to buy”Each instrument comes with everything you need to test,including:• Test leads• Stakes• Batteries• Calibration certificate• Rugged polypropylene carry case

Now…additional NEW models for more applications

Building on the success and popularity of the initial new ground testers, Megger has expanded the line to include twomore new units.

This great line-up now includes these six instruments:

Model Description

DET3TD For basic requirements it provides digitalground testing and bond testingcapabilities

DET3TA For those who prefer an analog display

DET3TC The revolutionary new model with thecapability of testing on-site groundswithout disconnecting the utilityconnection

DET4TD For the added feature of a fourthterminal (for the measurement of soilresistivity)

NEW DET4TC For 4 pole testing as well as attached rodtechnique and stakeless techniques

NEW DET4TCR Rechargeable tester for 4 pole testing,attached rod technique and stakelesstechniques

The new DET4TC and 4TCR provide these additionalcapabilities:• User selectable 25 V or 50 V output for specific compliance

with IEC 61557-5• Perform stakeless measurements where driving stakes is

not practical

New, updatedGetting Down to Earth

The most requested publicationin the area of ground testing,now in its 15th printing withtens of thousands beingreferred to regularly in thefield.

Request you free copy today

Phone: 1-800-723-2861ext 8536

WHY USERS ARE RAVING about these newground testers

Email: sales@megger.com

Snail Mail: check the box on the cardenclosed with this newsletter

Using ART method with the DET3TC to test commercialground without disconnecting the system.

Model DET4TCRshown performingthe stakeless groundtesting methodusing only clamps.

Model DET4TCR shown performing the classic fall-of-potentialtest method.

For everything you wanted to know about ground testing,including application guides and notes and a graphical runthrough on how to test grounds, go to our microsite atwww.megger.com/det.

...that is the question. Whether ‘tis nobler in the minds ofmen to earth test with four leads, or three. Megger GroundResistance Testers are available in both three- and four-terminalmodels. Deciding on which type suits your needs may be yourfirst decision on the way to selecting a Ground ResistanceTester. Of the six available models, three are three-terminaltypes, and are comparatively economical. The remaining threehave a full complement of four terminals, and cost more. Whatis involved in making this determination?

There are just two prime considerations in deciding upon thenumber of terminals (hence, number of test leads) required:resistivity and resolution. This note will deal with resistivity.

The term resistivity is easily confused with resistance, andsometimes the two terms are used interchangeably (andincorrectly). Resistance refers to the primary measurement

To Lead or Not To Lead... Deciding on a 3-Terminal or 4-Terminal Ground Tester

performed by an earth tester, the resistance relationshipbetween a buried electrode and the surrounding soil. It is givenin Ohms. Resistivity, on the other hand, has nothing to do withany installed electrical structure, but is a pure measurement ofthe electrical conductivity of the soil itself, and is commonlyrendered in Ohm-centimeters.

All can perform a resistance test, in full conformance with theFall of Potential Method accepted by IEEE. However, to performresistivity measurements, in accordance with the establishedWenner Method, you must have a four-terminal model.

The full four terminals are used to improve the accuracy andresolution of the measurement by eliminating lead and contactresistance. All resistance measurements can be made optionallybetween either a three- or four-terminal configuration. Three-terminal is the quicker and simpler, with one less lead to string.

However, use of all four terminals establishes a true four-wireKelvin bridge measurement that is free of any lead or contactresistance. If the operator is only trying to meet the standard NECrequirement of 25Ω or less, the few tenths that are normallycontributed by the common lead are not a significant part of themeasurement, and a quicker three-terminal test is sufficient. Butto check, for instance, a computer room ground, that may bemandated as low as 1Ω , the extra work of running a fourth leadmay be worth the effort, by resulting in a clear, sharpmeasurement of only the ground resistance. Once the number ofterminals has been considered, go on to examine ranges, noiseprotection, power source, and other features, to make the finaldetermination of the model that best suits the operator'srequirements and preferences. Just remember, if some otherfeature catches your attention, you can use a four-terminal modelin a three-terminal application, but not the other way around.

MPP1000

10

NEW Underground Fault Locator

Pin-Points the ProblemTesting Panel Meters

W I T H T H E M P R TBy Stan Thompson, Product Manager - Relay Test Equipment

Introduction

A customer recently called wanting to know how the accuracy of the MPRT stacked up against theArbiter 1040C Panel Meter Calibrator. Even though the MPRT was not designed with that applicationin mind, it could certainly be used for some panel meter test applications. The MPRT is not like the1040C panel meter calibrator, nor is the 1040C like the MPRT relay test set. However, the MPRT couldbe used to test meters. With that in mind I investigated what advantages each unit had in terms ofoutput voltages, currents and accuracy. This comparison is between the voltage and current outputsfrom the two units. Any other comparison would not be fair, since the MPRT can out perform the1040C in almost every respect. For example, the output compliance voltage for the AC and DCcurrents from the MPRT exceeds the 1040C by a factor of 8 times. It would be like trying to comparethe power train of a Ferrari to a VW Beetle. However, the 1040C does have some advantages at lowlevel outputs. Again, trying to compare the low level outputs of the 1040C to the MPRT is likecomparing the gas mileage of the VW to the Ferrari. In other words each unit has its advantages.Therefore, in this comparison we will only review the outputs and the accuracy of the outputs.

AC Voltage Output

The 1040C has one advantage, it can provide up to 750 Volts AC single phase. The MPRT with twovoltages in series can provide up to 600 Volts. If the application is to test 480 volts single phase, thenplace two MPRT Voltage amplifiers in series at 240 volts each. In comparing the voltage outputs andaccuracies you need to consider output ranges. According to the Arbiter instruction manual the1040C can provide from 1.5 to 750 Volts AC, with two ranges 0 – 150 and 151 to 300. The MPRThas three ranges, 0-30, 150 and 300. In comparing voltage outputs from 1.5 to 300 Volts, the MPRTis 2.5 times more accurate in the 150 Volt range and 4.5 times more accurate up to 300 Volts.

DC Voltage Output

The 1040C has a big advantage in DC voltage, since it has a more dynamic output range. It canprovide 0.1 millivolts up to 1000 Volts DC. The MPRT has the three ranges 30, 150 and 300 Volts. In comparing outputs both units had spot advantages. For example, the 1040C is more accurate atthe low mV outputs (no surprise there). However, when we get up to test voltages from 15 to 30volts, the MPRT is more accurate. The same is true for voltages from 110 up to 300 Volts.

AC Current Output

Again both units have their advantages. The 1040C is more accurate at the lower output currents,while the MPRT is more accurate at the higher test currents. For test currents from 0.1 to 3 amperesthe 1040C is more accurate. As the test current rises from 3 to 6 amperes their margin of accuracygets thin. For example, at 6 amperes the 1040C is more accurate by 0.0005 amperes (that’s thin). The big disadvantage of the 1040C is it is limited to a maximum output of 7.5 Amperes. At 7.5Amperes the MPRT is more accurate by 0.0075 amperes. In actual usage, both units are basicallyequal at 5 amperes. A milliamp one way or the other doesn’t make much difference at 5 amperes.

DC Current Output

Like the AC current output each unit has advantages. The 1040C is better at the lower currents, whilethe MPRT is better at the higher currents. The 1040C has a dynamic range from 0.1 mA to 10.5Amperes, while the MPRT is 0.6 to 30 amperes DC. Depending on the range of operation, the 1040Cis more accurate up to about 1 ampere then the MPRT becomes more accurate from 1 amp up to themaximum output of the 1040C of 10.5 amperes. The MPRT has the output advantage of being ableto supply up to 30 amperes DC.

Phase Angle

The 1040C has an adjustment of ±180 degrees, with an accuracy of ±0.33 degrees. The MPRT hasthe advantage in both adjustability and accuracy. Remember that the 1040C is a single phase unit,while the MPRT is modular. The MPRT can be a single phase unit or more than likely it’s a three phaseunit. The user can set the phase angles to be adjustable in either ±180 degrees, like the 1040C, or beadjustable 0 – 360 degrees either Leading or Lagging. When it comes to testing Watt and VAR, thiscan be a big advantage for the MPRT. The MPRT also has the accuracy advantage. The MPRT istypically ±0.02 degrees. However, allowing for all temperature conditions, the MPRT can be ±0.25 degrees.

Frequency

Like phase angle, the MPRT has the advantage in range, adjustability and accuracy. The MPRT has 4times more accuracy in output frequency. The output range of the 1040C is limited: 50 to 75 Hz and333 to 500 Hz. The MPRT has an output range of DC to 1,000 Hz.

Conclusions

Both units have advantages and disadvantages. If using the unit to test and calibrate typical AC panelmeters, then the MPRT has the advantage. At a typical full scale test voltage of 150 Volts, the MPRT isseveral times more accurate than the 1040C. At a typical test current of 5 amperes, the 1040C has avery small advantage of (±0.002 amperes). That’s a difference of only 0.04 %. With such a smalldifference, one could consider the units equal at that test current value. The MPRT also has theadvantage in output frequency and phase angle accuracies. Depending on the application, yes theMPRT can be used to test panel meters with better accuracy than the Arbiter 1040C.

Megger MPRT Relay Test Set

Megger Tradeshow Schedule

Megger participates in a variety of tradeshows and conferences every year in the US,and internationally, in order to bring the latest technologies and new products to asmany local events as possible, and help customers reduce expenses and time away frombusy schedules. Here is the current US Tradeshow Schedule, further information on anyof these events can be obtained by contacting Megger at: 214-330-3245 or 1-800-723-2861, ext. 3245 or go to our website at www.megger.com.

April 9-11 Indiana REMC Suppliers Meeting French Lick, IN

April 9-12 Marshall Hot Line School Marshall, MN

April 12-13 NEPPA/ECNE O&S Conference Boxboro, MA

April 23-27 NWPPA E&O Conference Tacoma, WA

April 30 - May 11 MESA Hot Line School Grand Junction, CO

May 1-3 Battcon 2007 Tampa, FL

May 1-4 Georgia Tech Relay Conference Atlanta, GA

May 2-4 IMEA Spring Conference Ft Watyne, IN

May 7-11 Mid-South Electric Meter School Nashville, TN

May 14-17 NCAMES Greenville, NC

May 15-18 MMUA Underground School Marshall, MN

May 21-24 ECNE Metering Conference Worcester, MA

June 11-13 SWEMA Summer Meeting Galveston, TX

June 24-28 North Carolina Meter School Sunset Beach, NC

August 6-9 Great Lakes Electric Meter School (GLEMS) Grand Rapids, MI

August 19-22 NEPPA Utility Conference & Expo Rockport, ME

Megger recently introduced the MPP1000Pinpointer Instrument. Below are excerptstaken from a resent article written about thetest set.

The MPP1000 senses electromagnetic andacoustic pulses to locate faults in undergroundpower lines. The problem for us reviewers isthat we didn’t have ready access to anunderground fault condition – and you knowhow understanding utilities are when you startmessing around with their lines withoutpermission!

So, we dialed up a knowledgeable testingengineer with a major mid-west utility. Heand his fellow engineers spend some part ofevery day locating and fixing undergroundfaults, particularly in the summer when heavyloads, higher temperatures, and aging cablescombine to cause problems for electricaldistribution.

“The MPP1000 really speeds up operations,”he explained. “We can go with a single probeinstead of a double probe, and the system’sability to filter out acoustic noise caused bynearby roads and similar issues makes theprocess much faster and easier.”

The unit ships with a handheld unit; metalrods for holding one or two geophone sensorheads, depending on your configuration;

removable spikes, cables, and hand knobsfor each geophone, and a pair ofheadphones.

In operation, this test engineer’s crew hooksthe faulted line up to a surge generator andsends a wave of high-voltage electricitydown the broken line. The gap in the linecreates an arcing fault that generates bothan electromagnetic pulse and an acousticwave. The MPP1000 senses the strength ofboth the electromagnetic wave and theacoustic wave. The handheld unit displays

the strength of both pulses, andestimates distance to the fault bythe time delay between theelectromagnetic pulse andacoustic wave. A two geophonesystem also allows triangulation.

He further commented that theMPP1000 unit’s ability tocalibrate before takingmeasurements and then filter out‘ambient’ acoustic ground noisereally speeds up the locatingprocess, which reduces the wearon the line caused by repeatedlysending electrical surges alongthe faulted cable.

This particular testing engineerhas also had plenty ofopportunity to test theruggedness of the handheld unit,pronouncing it impervious torainy conditions. He also agreedwith yours truly that the interfacewas extremely intuitive and easyto use with eight oversizedbuttons designed for specifictasks: start test, filter on/off,

backlight, volume, etc. The display shows thedelay between the pulses, an arrow pointingin the direction of the pulse, andapproximate distance to the fault.

If you work for a utility or other largeinstallation where ground faults arecommon, the MPP1000 can save more thanjust time, it can save you on repairs too.Generating the surges required to findunderground faults can cause their ownfaults, so limiting the detection period iscritical to preserving electrical infrastructure.

For more information about the MPP1000Pinpointer please contact us today!

Email: sales@megger.comPhone: 1-800-723-2861Website: www.megger.com

or fill out the enclosed card.

Megger MPP1000 Pin Pointer

11

In a perfect world, category rating would not matter. But

in the real world every mains supply has transients

superimposed on it, and that’s what category ratings are all

about.

A distant lightning strike, for example, can produce a

transient of several kV on the supply. The transient may

only last for a few tens of microseconds and, in itself, it is

likely to do little damage. The problems is that it may

initiate an arc and, this arc then presents a low impedance

path for current from the mains supply.

Often, that supply can deliver 1,000 A or more until the

breaker or other protective device operates. In that time,

the amount of energy liberated at the site of the arc is

easily enough to start a fire or even cause an explosion.

If the arc is within a test instrument that happened to be in

use when the transient occurred, there is a high probability

that you the user will be injured or worse!

The solution is simple – design the instruments with

internal clearances that are large enough to prevent

transients from establishing an arc in the first place, along

with appropriate protection devices. Guidance to this is

given in IEC61010 in order to comply with category ratings

defined in IEC60664.

In practice, transients are damped quite quickly as they pass

through a typical building distribution system. Their energy

is highest at the point where the supply enters the building,

A small faultbecomes a bigproblem onCategory IV highenergy unfusedsupplies!

Why CAT IV?and only instruments with a CATIV rating are suitable for

use at this point.

Once the supply has passed through the distribution board,

the transients have lower energy levels, and CATIII

instruments are safe to use. At a socket outlet, the energy

levels are lower still.

For performing tests within appliances, such as television

and photocopiers, CATI instruments can be used although

major suppliers rarely offer instruments of this type.

Many instruments in use today are rated CATII, with the

better ones CATIII. These should be fine within their

limitations, but they’re simply not designed – and not safe

– for use by anyone whose work involves testing on mains

circuits before they enter a building, or at the point of

entry. They should use a CATIV instrument.

There is simply no case for making compromises.

Fortunately, there is no need to, as Megger’s MIT400 series

insulation resistance testers are suitable for CATIV 600 V

applications, and its LT300 loop tester is rated suitable for

CATIV 300 V applications.

At first, the CATIV rating may seem unnecessary for the

MIT400, since insulation testers are used on dead circuits.

The MIT400, however, also offers useful facilities for

measuring voltage, so the CAT rating is every bit as

important as it is for a multimeter.

In live circuit applications, a CATIV instrument is essential

for loop testing carried out at or before the incoming

cutout. CATIV-rated instruments are also particularly

important for electrical utilities, as all of their installations

are all in CATIV environments, which is why EdF in France

and other utility companies now insist that all of their

contractors use CATIV instruments.

TRACE FAULTSThere have been many peoplewith the same basic question,“Which ground fault tracershould I buy, the BGL or theBGFT?”

Megger Ground Fault Tracers,the BGFT and BGL

station ground makes a complete circuit enablingtracing the fault to its exact location. Simply tracethe injected signal. Any branch circuit with a faultwill have some amount of injected current. Anybranch circuit without a fault will have no acsignal.

In generating stations with many rotatingmachines and high electrical noise, the BGFT isthe only one that should be recommendedbecause of its 80W of output power (comparedto 3W for the BGL.)

In substations, noise is usually not as critical acriterion as other aspects such as user knowledgelevel, frequency of faults and ease of use. To beperfectly honest, ease of use is a relative termdepending upon how each person defines it. Theprocess of tracing faults should be an infrequentevent and therefore, the instrument and its usemust be easy enough that a complete trainingprogram is not required for each fault-findingevent.

companies’ protocols, faults are not traced untilthe resistance falls below the 25 to 50 kΩ rangewhich is usually when a second fault occurs.Then both faults are traced and corrected. Theone exception to this, generally, is the nuclearindustry where the first fault is tracedimmediately.

Both the BGFT and the BGL can be very easy touse. Both units have bridges to measurecapacitance and resistance, individually. The BGLhas an automatic bridge which is easier than theBGFT’s manual bridge. Of course, the manualbridge need not be used. However, if the bridgeis not used, it is possible to trace phantom faultsdue to high capacitance.

The bridge, whether manual or automatic, isused to search for the circuits with the real faults,i.e., resistance versus capacitance. Using themanual bridge of the BGFT can be timeconsuming in one respect; verifying each branchcircuit with a high current to determine whichbranch(es) has the fault(s). In the other respect,tracing phantom faults can also be time-consuming and there is more walking involved.If, however, there have been many faults and it isa well-characterized system, usually the culpritcircuit is known and simply needs confirmation.A bridge is not required in this instance.

The benefit of having a stationary, line-poweredtransmitter connected at the battery or first panelis that the “Receiver-CT” which is used to takethe readings of total current (resistance pluscapacitance) at each branch circuit is carried toeach panel. The Receiver-CT weighs less than onepound (1⁄2 kg). The downside to the Receiver-CTis that there is no capability to separately

measure resistance from capacitance. Simplytrace any high reading and usually there aren’tso many of them. Therefore, tracing phantomfaults is not very time consuming and thereadings decrease linearly in value as one goesfurther into the dc network.

The BGL combines the BGFT’s Transmitter andReceiver-CT in a single unit. The advantage isthat only real faults are traced using theautomatic bridge at each panel and each branchcircuit. There are no extra knobs or adjustments,simply push a switch and measure. It is fullyautomatic. The BGL is battery-operated and isrelatively lightweight at 25 lbs. (11 kg).

Some helpful hints to aid in quicklyfinding faults:• Mark each branch circuit with the

base value

• Know where the problem areas have been(during rainy seasons, sensitive components, etc.)

• Have schematics readily available

The differences are not so great as to causemajor concern and both work very well. Bothhave been in production for many years, arewell-supported and very reliable. It is hard tomake a mistake with either one (with theexception of noisy systems). The real mistake isnot taking advantage of the technology. Turningoff breakers to find a fault is both dangerousand time-consuming, not to mentionunnecessary. The BGFT and BGL are the answersto many a maintenance person’s ground faultnightmares due to their ease of use andsimplicity.

By Rick Lawrence, Product Marketing Engineer, Norristown, PA

A Practical Guide to

Megger Battery Ground Fault Tracer

BGFT BGL

Generating Station �

Noisy System �

Frequent User � �

Infrequent User �

Few Faults �

Many Faults �

There are several main differences between thetwo instruments including relative ease of use,output power and line- versus battery-operated.The similarities are that they both find (andmeasure) very well single and multiple faults inungrounded DC systems. They both do their jobswhile the battery is on-line and neither one tripscircuit breakers because they both ramp thecurrent and voltage. The differences arediscussed in detail below.

Both utilize the same basic principle: they bothinject a low frequency ac signal across one sideof the dc buss to the station ground creating areturn path for the signal. The signal will flowthrough the dc buss to the fault location andthen pass to ground. The connection to the

Both instruments can trace faults in “normalranges of resistance” that most people worryabout. The BGFT can detect resistance faults upto about 400 kΩ and the BGL can detectresistance faults up to about 100 kΩ. In manycases and depending upon individual

…We get letters…and emailsWe always want to know when things aren’t exactly right. We also want toknow when things are going right, too….or when one or more of ourpeople truly shine in their customer service performance.

A few examples follow:• I wish to express this lab’s gratitude for a JOB WELL DONE! Rodney

Vargas and Kelly Combs went beyond the “call of duty” to help usout on repairing and drop shipping an Epoch 40 to a Nuclear Plantfor immediate use. They both showed what customer service shouldalways be! Even when customers are as aggravating and sometimesas demanding as we were, because of a desperate situation.Rodney was patient and went out of his way to make sure I wasinformed on all progress and of the completion of the task andKelly did an excellent job of putting our needs ahead of otherpressing work. I know your company has many other customers andtheir requests, but last week, I felt like JML was the only customerMegger had and I want all credit for the success of this job to go toRodney and Kelly.

• We have owned an EBite for several years now. I needed updatedsoftware to download information from it. I was able to easily getwhat I needed from your website and it worked great. I justwanted to say thanks for having a great website. Keep up the good work!

• I am from the U.S. Army Defense Ammunition Center (DAC). Youand I spoke previously regarding the Getting Down to Earth books.We are again in need of more. We teach approximately 10-15lightning protection classes per year. Our class sizes average 20people per class. We service all of the U.S. Military for lightningprotection training. We utilize the books to discuss the “Fall ofPotential” method and the effects soil has on resistivity.Additionally, we use the books and our Megger testers whendiscussing testing methods.

NOTE: Our most popular testing applications book ever, GettingDown to Earth, is used at many educational institutions worldwideand is readily available upon request at 1-800-723-2861 ext. 8536 orat sales@megger.com.

Megger was an active participant at NETA PowerTest 2007 in mid March inDenver. This national event is held annually by the InterNational ElectricalTesting Association and attracts over 300 attendees who provide electricaltesting services for industrials, facilities and electric utilities in NorthAmerica and elsewhere. Megger’s participation included an exhibit andhospitality suite where hands-on product displays were used to showcustomers the latest in new test and measurement equipment and design.

Please see page 10 for other events where you can see more newtest equipment being introduced during 2007.

See Megger atnumerous events during 2007

DID YOU KNOW?

MIL/28M/4.2007

Direct comments to: Editor, THE ELECTRICAL TESTER

Megger, 4271 Bronze Way, Dallas, TX 75237-1019Phone: 1-800-723-2861 Fax: 214-331-7379

E-mail: ussales@megger.com

Would you like to reference previous issues of The Electrical Tester?

View them on-line at www.megger.com.

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Lansing, MichiganCircuit Breaker Maintenance, Low-Voltage May 7-11, 2007 $1595Circuit Breaker Maintenance, Molded- and Insulated-Case May 14-15, 2007 $645OSHA Electrical Safety-Related Work Practices May 16-17, 2007 $645

Las Vegas, NevadaNFPA 70E Electrical Safety May 8-9, 2007 $695Arc-Flash Hazard Analysis Seminar May 10-11, 2007 $645Electrical Safety for Industrial Facilities May 15-18, 2007 $1045

Orem, UtahNFPA 70E Electrical Safety May 15-16, 2007 $695Arc-Flash Hazard Analysis Seminar May 17-18, 2007 $645Electrical Safety for Industrial Facilities May 21-24, 2007 $1045

Orlando, FloridaCircuit Breaker Maintenance, Medium-Voltage May 15-18, 2007 $1245

Portland, OregonNFPA 70E Electrical Safety June 5-6, 2007 $695Arc Flash Hazard Analysis Seminar June 7-8, 2007 $645Electrical Safety for Industrial Facilities June 11-14, 2007 $1045Protective Relay Maintenance, Basic June 18-22, 2007 $1545Protective Relay Maintenance, Advanced June 25-29, 2007 $1545

Reading, MassachusettsSubstation Maintenance I June 4-8, 2007 $1545Substation Maintenance II June 11-15, 2007 $1545

Roseville, CaliforniaProtective Relay Maintenance, Basic May 21-25, 2007 $1545Protective Relay Maintenance, Advanced May 29 – June 1, 2007 $1545NFPA 70E Electrical Safety June 19-20 2007 $695Arc Flash Hazard Analysis Seminar June 21-22, 2007 $645Electrical Safety for Industrial Facilities June 25-28, 2007 $1045

Toronto, CanadaProtective Relay Maintenance, Basic May 14-18, 2007 $1545Protective Relay Maintenance, Advanced May 21-25, 2007 $1545Advanced Visual Testing Software June 4-8, 2007 $1545

Valley Forge, PennsylvaniaBattery Maintenance and Testing May 30-31, 2007 $645

Here’s why AEES is not just anotherengineering services company.Focused – AEES is not a division of a huge apparatus manufacturer or engineering firm. There are no distractions from other directions or responsibilities.

Experienced – AEES offers the experience and expertise to offer a fullcomplement of electrical power system engineering services, including:

• Arc Flash Hazard Analysis• Short Circuit Analysis• Protective Device Coordination Studies• Low Flow Studies• Power Factor Correction Studies• Equipment Evaluation Studies• Single-Line Drawing Development• And more

Economical – AEES does not have any large backroom operation to support. Overhead is deliberately kept low to be very competitive when bidding for your business.

Responsive – AEES acts as your “in-house consultant”, providingpersonalized start-to-finish project management.

AEES customers say it all“In working towards complying with the requirement of NFPA70E…afterseveral discussions with potential partners we chose Benny May with AVOEngineering”.

Dave DavoltElectrical Supervisor, Nucor Steel

“Their quickness to respond, efficiency in performing the work on handand a very professional atmosphere are other reasons why I have goodexperiences with them”.

Neil StromElectrical Engineer, Carlisle SynTec, Inc.

AEES is not just another engineering services company. For all the details, contact Benny May today:

Email: benny.may@avoeeservices.comPhone: 1-877-594-3156, ext. 3559

1-214-330-8559Fax: 1-214-331-7363Web: www.avoeeservices.com

The AVO Training Institute

(a subsidiary of Megger)

also operates a division

providing electrical

engineering services called

AEES, or AVO Electrical

Engineering Services.