Bender Brochure

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Overview

Protection Relays



2

The Power In

Ground Fault Detection, Location, and Protection Products

A comprehensive line of ground fault protection products, utilizing the latest in technology, and covering a multitude of applications and sy-

stems. BENDER‘s ground fault relays safeguard equipment, personnel, and processes while reducing your costs and system downtime.

Global Experts in Electrical SafetyFor over 70 years, BENDER has been a global leader in ground fault protection. With over 50 agencies and partners across the globe,

BENDER has a local office to help you from the design phase through the support phase. Our years of technical experience and broadportfolio of products utilizing the latest in protection technology will help you create the best solution to meet your needs. Top-

notch service and support ensure that your electrical network remains in peak condition. From industrial plants to mines to hospitals,

customers trust BENDER to protect their electrical systems.



www.bender.orgYour online electrical safety resource

n Complete listings of products with comparisons, documen-

tation, datasheets, and technical information

n Your electrical safety questions answered in our extensive

knowledgebase with application notes

n Ground Fault Relay and GFCI Selection Tools

n Current Transformer Sizing Application

n Complete Isolated Power Solution Builder

n Local representative information

Electrical Safety

Voltage and Current Relays

A multitude of protection relays for monitoring system performance

and safety outside of ground fault protection. Voltage relays, current

relays, frequency relays, and more provide predictive maintenance

and troubleshooting for your electrical system.

Hospital Isolated Power Systems

Hospital grade isolated power panels and monitors to ensure your

critical areas remain fault-free. Our panels are built to your specifi-

cations and include the state-of-the-art LIM2000plus Line Isolation

Monitor.



4

Ground Fault Detection / Location

Ungrounded AC/DC Systems

Reduce system downtime and provide predictive

maintenance capability by locating ground faults quickly

Reduce maintenance costs by detecting ground

faults before a hazardous situation occurs

BENDER Ground Fault Detectors for Ungrounded Systems

Ungrounded systems offer an invaluable advantage - a first

ground fault does not generate sufficient leakage current to

create a hazardous situation. Early detection allows for critical

systems to remain online while problems are located and resol-

ved. BENDER Ground Fault Detectors and Location Systems detect

ground faults quickly and easily across all types of applications,

including DC systems as well as systems containing variable

frequency drives (VFDs).

Online Ground Fault Location - the BENDER Difference

When others say ground fault location in an ungrounded system

is not possible, BENDER says it is. The EDS series of ground fault

location products offers fast and easy-to-use location of faults

with both portable and installed options. BENDER‘s advanced EDS

system can locate ground faults down to the load level to find thefaulty device, all while the system remains online.

The BENDER Advantage

BENDER‘s complete line of ground fault products for ungrounded

systems offers impressive advantages to keep your system online

and running healthy:

n Exceeds requirements for NEC 250.21(B) and CEC 10-106(2) for

ground detectors on ungrounded systems

n Works in AC, DC, and AC/DC applications up to 7.2 kV

n Works with Variable Frequency Drives (VFDs)

n Detects symmetrical faults

n AMP measuring principle allows for accurate insulation

measurements across all types of systems

n Simple and fast ground fault location in ungrounded AC

and DC systems with both portable and fixed equipment

n Reduce cost, reduce downtime, and protect vital equip

ment and processes with accurate early warning ground

fault detection and location

Complete Ground Fault Location System



IR425-D4 - Ground Fault Detector - Low Voltage AC/DC Ungrounded Systems

The IR425-D4 Ground Fault Detector monitors ungrounded AC/DC circuits up to 300 V for early indication of ground faults. A digi-

tal display gives real-time readings of the system‘s insulation resistance to ground to provide predictive maintenance capability

and troubleshooting for ground faults. Its compact size allows for easy installation and retrofitting.

IRDH275 and IRDH375 - Ground Fault Detectors - Ungrounded AC/DC Systems

The IRDH series of ground detectors provides state-of-the-art protection for your ungrounded system. The AMP Plus measuring

principle ensures that an accurate measurement is taken through all forms of power conversion, such as DC rectifiers and drives.

A digital display gives a real-time reading of the system‘s resistance. Optional RS-485 communication is available.

EDS3090 - Portable Ground Fault Location System - Ungrounded AC/DC Systems

The EDS3090 provides a portable location system to quickly find ground faults in any size system. The system can be used in

conjunction with BENDER‘s installed ground fault detectors or on its own as a completely portable location system. The simple

clamp-on meter provides quick location of faulty loads. Installed location devices additionally provide RS-485 communication.

Ground Fault Products

Ungrounded AC/DC Systems

Features

n For AC and DC systems up to 300 V

n Digital display with real-time readout

n Adjustable setpoint from 1 to 200 kΩ

n Two separately adjustable alarms with

N.E. / N.D. SPDT contacts for each

Features

n For AC and DC systems up to 793 VAC,

650 VDC (voltage couplers extends

range up to 7.2 kV AC. 1.6 kV DC)

n Digital display with real-time readoutn Adjustable setpoint from 1 kΩ to 10 MΩ

n Two separately adjustable alarms with

Features

n For AC and DC systems

n Installed and portable versions

n Quickly identify and locate ground faults

n RS-485 communication with installed

location devices for remote indication

More information: bender.org/ir.aspx

More information: bender.org/irdh.aspx

More information: bender.org/eds.aspx

Applications

n Single-phase AC and DC systems

n Industrial control circuits

n Remote operated vehicles

n Low-voltage motors and drives

n General low-voltage applications

Applications

n Single- and three-phase AC and DC

n 480 V / 600 V industrial systems

n Variable frequency drives

n Solar fields

n Offshore platforms

n Backup battery systems

Applications


n Large motor control centers

n Ships

n Power stations



6

Ground Fault Monitoring

Grounded AC/DC Systems

Protect equipment from damage and fire and

reduce your bottom line

Protect personnel from shock hazards and injury

BENDER Ground Fault Monitors for Grounded Systems

BENDER ground fault relays provide critical protection for

personnel and equipment in environments where safety is a

must. The RCM series provides advanced warning of ground

faults without the problems associated with nuisance tripping

on grounded and high-resistance grounded systems. Accu-

rate tripping across steplessly adjustable setpoints means

BENDER‘s RCM series can easily be tailored to your particular

application. Output contacts can be used for indication, inter-

ruption, or both.

AC/DC True RMS Detection - the BENDER Difference

The RCM series provides relays that not only protect AC, but

pure DC power as well. Pure DC measurements are still taken

via a special current transformer. Digital versions feature true

RMS reading of the leakage current. The multi-channel relayseven feature harmonics analysis of the leakage current down

to the 40th harmonic. This device also features RS-485 commu-

nication capabilities for remote analysis.


BENDER‘s complete line of ground fault products for groun-

ded and high-resistance grounded systems offers impressive

advantages to keep your system online and running healthy:

n Works on AC, DC, and AC/DC systems

n Utilization of a single current transformer means voltage

and load current do not impact measurements

n

Works on systems with Variable Frequency Drives (VFDs)n Digital series provides true RMS readings and frequency

ranges up to 2000 Hz

n RS-485 communication capability for remote monitoring

and integration into signaling systems

n Reduce cost, reduce downtime, and protect personnel and

and equipment with BENDER ground fault protection AC/DC Multi-Channel Ground Fault Monitoring System

Grounded SystemCurrent transformers

for AC/DC loads (0 2000 Hz)

Current transformers

for AC loads (42 2000 Hz)



RCM470LY - Ground Fault Monitor - Grounded and High-Resistance Grounded AC Systems

The RCM470LY family of ground fault monitors detects ground faults in grounded and high-resistance grounded AC systems,

both single-phase and three-phase. A wide, steplessly adjustable trip range allows for flexibility in application and installation. A

DPDT alarm contact can be utilized for both remote indication as well as power interruption.

RCMA420 - Ground Fault Monitor - Grounded and High-Resistance Grounded AC/DC Systems

The RCMA420 monitors for ground faults in grounded and high-resistance grounded AC and DC systems. Features include a true

RMS reading, real-time values displayed on its LCD screen, and two separately adjustable alarms with an SPDT contact for each.

This device is perfect for grounded and high-resistance grounded systems running variable frequency drives (VFDs).

RCMS460 / RCMS490 - Multi-Channel Ground Fault Monitors - Grounded and High-Resistance Grounded AC/DC Systems

The RCMS family detects ground faults in grounded and high-resistance grounded AC and DC systems. Up to 12 separate

channels may be connected to one device. Features include a detailed LCD display of each individual channel‘s value, harmonics

analysis, and contact outputs for each individual channel on the RCMS490 model. RS-485 communication is also available.

Ground Fault Products


Features

n LED bar graph indicating ground fault

n Adjustable trip level from 10 mA to 10 A

(optional 6 to 600 mA trip range available)

n Failsafe or non-failsafe mode selectable

n N.E. / N.D. DPDT contact output

Features

n True RMS readings


n Adjustable setpoint from 30 to 500 mA

n Two separately adjustable alarms

n Works with DC power and drives

Features

n For AC and DC systems

n Digital display indicates real-time values for

each individual channel

n Quickly identify and locate ground faults

n RS-485 communication, DPDT contact out-

puts; 490 model features individual outputs

More information: bender.org/rcm.aspx

More information: bender.org/rcma.aspx

More information: bender.org/rcms.aspx

Applications

n Single- and three-phase AC

n General industrial use - panel

boards, motors, generators, and

more

n Heat tracing systems

Applications




moren Variable frequency drives (VFDs)

n DC battery systems

Applications




more

n Large motor control centers

n Heat tracing systems

n DC battery systems



8

Ground Fault Circuit Interrupters


Lifeguard Series Ground Fault Circuit Interrupters

The BENDER Lifeguard series of Ground Fault Circuit Interrup-

ters gives your system the added safety of both ground fault

detection and interruption. The Lifeguard series is customiz-

able to fit the needs of your system, from load amperage (up

to 100 A standard, higher versions available upon request),

voltage (including 480 V and 600 V systems), trip level, and

more.


BENDER‘s complete line of ground fault circuit interrupters

offers impressive advantages to keep your system online and

running healthy:


n Customizable to many different types of systems, including

480V and 600V three-phase systems

n Many setpoint options available: 6 mA, 20 mA, or steplessly

adjustable options

n 6 mA and 20 mA options operate on an inverse time curve

per UL943

n Connection monitoring and grounded neutral protection

n Customizable enclosure options available, including NEMA

4X fiberglass and stainless steel options

Protection Against Nuisance Tripping

The Lifeguard GFCI contains a special ground fault monitor

that protects against nuisance tripping while still maintainingthe level of protection you require.

Features of the 6 mA and 20 mA versions include:


n Inverse time curve for tripping per UL943

n Advanced filtering circuitry

n Connection monitoring

n Grounded neutral protection

Features of the adjustable versions include:

n Works on AC (AC/DC version available)n Adjustable trip level

n Adjustable time delay

n Connection Monitoring

Inverse time tripping curve built into BENDER‘s

6 mA and 20 mA versions

Applications

n Motors and Drives

n Pumps

n Generators

n Spas and pools

n Construction

Build your GFCI online: Visit bender.org/selector/gfci.



VME420 and VMD420 - Voltage and Frequency Relays

The VME420 (single-phase AC and DC up to 300 V) and VMD420 (three-phase AC up to 500 V) relays are powerful, all-in-one

devices monitoring overvoltage, undervoltage, overfrequency, and underfrequency. Precise, explicit values may be entered in for

alarms and real-time values may be viewed via the onboard LCD display.

CME420 - Current Relay

The CME420 monitors for overcurrent and/or undercurrent in AC systems. The digital display gives real-time readouts of the

current being measured. The CME420 may be directly connected to a system up to 16 A. The device may also be connected to x/5

current transformers. Entering the current transformer ratio into the device will negate the need for any type of calculations.

Voltage and Current Relays

AC and DC Systems

Features

n True RMS readings


n Precise voltage and frequency alarms

may be entered

n Two separately adjustable alarms

n Works with DC power and drives

Features

n True RMS readings


n Precise alarm values may be entered

n Two SPDT contacts

n May be directly connected (up to 16 A)

or connected via an x/5 current trans-

forner

More information: bender.org/voltage-relays.aspx

More information: bender.org/current-relays.aspx

Applications


n General industrial use

n Battery monitoring and charging

stations

n Dump load controller

n Generators

Applications

n AC systems

n General industrial use

n Generators

n Pumps

n General load monitoring

BENDER Voltage and Current Relays for AC/DC Systems

BENDER‘s portfolio is not just limited to ground fault protec-

tion - it also includes powerful safety relays for monitoring

many different aspects of an electrical system. The VME420,

VMD420, and CME420 monitor for many different alarms,

including voltage, current, phase loss, phase sequence, and

more. True RMS readings are shown via digital displays in real-

time.

Two highly configurable SPDT contacts on each device may

be set to trigger on whichever type of alarm your application

demands. Optional versions also include standard analog out-

puts (0 - 10 V, 0 - 20 mA, 4 - 20 mA) for remote signaling.

Current relays may be connected either directly to the system

or through current transformers. If a current transformer is

used, the ratio may be entered into the CME420. Once this is

entered, you may set alarms and view readings as if the devicewere directly connected - no calculations necessary.



10

Communication

Integrate BENDER Devices Into Your Safety Network

Many BENDER ground fault detection devices can be linked

together across a communication network for remote moni-

toring. Utilizing a special protocol across RS-485, these devices

can give control stations detailed information as to the

condition of the system. Gateway devices utilizing standard

protocols such as Ethernet, MODBUS and PROFIBUS ensure

your BENDER system is easily integrated into an exisiting com-

munication system. Special remote indicators placed in critical

areas and connected to the network can also display device

information. Many devices also support settings changes via

remote communication.


n Fast, detailed information and parameterization from acentral point

n Easily integratable into an exisiting communication system

n Gateway device to standard protocols such as Ethernet,

MODBUS, and PROFIBUS

n Option to view status of all devices via a web browser

n E-mail and SMS alerts when an alarm becomes active

n Optional Remote indicator station provides information on

all connected devices

n Reduce costs and downtime



Accessories

Current Transformers

Name Features and Description For Use With

W Series Current transformers for use in single-phase and three-phase AC systems RCM series, RCMS series, EDS series

WAB SeriesCurrent transformers for use in single-phase and three-phase AC and DC

systems

RCMA420, RCMS series

WF SeriesFlexible, rope-style current transformersfor use in single- and three-phase AC sy-stems

RCMS series

More information: bender.org/ct.aspx

Remote Indication

Name Features and Description For Use With

9604 and 7204 SeriesAnalog external meters indicating percen-tage towards alarm for RCM devices or in-sulation reading for IR devices

RCM470LY, RCM420-DM Series,IR470LY, IRDH Series

MK2430 Digital remote indicator for multiple de-vices connected via RS-485

IRDH B Versions, EDS Series,RCMS Series

More information: bender.org/remotes.aspx



12

Information and Applications

Ungrounded Systems

Ungrounded Systems

Floating systems are derived from a power source where there is vir-

tually no connection to ground. 480VAC delta configured transformers

are a typical supply for a floating system. Some deltas in the mining

industry can be found in hoists. 480VAC deltas are also in wide spread

use to supply 1000Amp - 2000Amp main feeder circuits in general

industrial applications. Floating systems are often used in areas where

a sudden shut down must not occur. Examples are intensive care units

(ICUs) in hospitals, signal circuits, and emergency backup systems.

The magnitude of ground fault current in an ungrounded system on a

first ground fault is very small. It depends on the system voltage, the

resistance of the ground fault causing part and the system capacitances.

Example: If a grounded object with low resistance touches a live con-ductor, the resulting current flow will be negligible. The ground fault

loop will be incomplete because the return path to the source is mis-

sing. Grounding may only occur through system leakage capacitance to

ground. The Possible resulting current is also known as charging current.

On a single ground fault, ungrounded systems will not produce the

amount of fault current needed to trip a common GFR. The IMD is the

device of choice for the protection of floating systems.

T2

T3

T1

GND

L e a k a g e

c a p a c i t a n c e

L1

L2

L3

L1

L2

L3

G r o u n d

F a u l t

i . e .

D e a d

s h o r t

circuit breaker motor, 3 phsupply side, 480 VAC

The ungrounded system with one ground fault path.

The Active IMD on AC Systems

An active IMD is the ground detector of choice for ungrounded

systems. The active IMD can detect ground faults regardless of

quantity and severity, as well as the ability to have early warnings

and trending.

The active IMD is considered to be an online megger. It connects via

pilot wires between the system and ground. A constant measuring

signal is sent from the IMD into the power wires. It will spread out

evenly into the secondary side of the transformer and the attached

loads. If this signal finds a breakthrough path to ground, it will take

this path of least resistance and return to the monitor. The IMD‘s

internal circuitry will process the signal and trip a set of indicators

when the resistance of the fault reaches a certain trip level. By the

nature of the ungrounded system, leakage current may or may not

be present at this time, however the ground fault will still be seenthrough the insulation resistance. Because of this, IMDs measure in

Ohms (resistance) and not in Amps (current). A ground fault will be

indicated as insulation breakdown.

A good insulation value for a typical system would be a value of

multiple kΩ to MΩ. A low insulation value for a typical system

would be low kΩ to less than one kΩ. However, the value of a

system‘s overall resistance may vary depending on the number of

loads, type of insulation used, age of the installation, environmen-

tal conditions, etc.

T2

T3

T1

GND

L1

L2

L3

L1

L2

L3

G F

( i . e .

D e a d

s h o r t )

Bender IMD relay(1)

V 1 G = 4 8 0 V

V 2 G = 4 8 0 V

V 3 G = 0 V

AMP measuring mode

circuit breakersupply side, 480 VAC motor, 3 ph

Ungrounded three-phase AC system with BENDER IMD




Ungrounded Systems

The Active IMD on DC Systems

The active IMD is the preferred choice for ungrounded DC

systems as well. As in floating AC systems, a DC IMD will be

connected via pilot wires between the system and ground. A

constant measurement signal will be sent from the IMD into

the power wires. From there, it spreads out evenly into the

secondary side of the supply (e.g. a battery) and the attached

loads. Again, the signal will take the path of least resistance

and return to the monitor if it finds a breakthrough to ground.

For DC systems, as well as AC systems that have varying volta-

ges or power conversion equipment including variable fre-

quency drives, a special measurement signal is applied.

BENDER‘s AMP Plus measurement principle, found in devi-

ces such as the IRDH275, have the ability to be used univer-

sally in AC, DC, and AC/DC systems, as well as overcoming

adverse system conditions, such as high leakage capacitance.

S u p p l y s i d e :

B a t t e r y s y s t e m

1 2 5 / 2 5 0 V D C

Schematic 21: 125 / 250 V DC system with Bender IMD technology

L1

L2

circuit breaker

+

-

+

-

V 1 N =

1 2 5 V

V 2 N =

1 2 5 V

L1

N

L2

V 1 2 =

2 5 0 V

V 2 G =

1 2 5 V

V 1 G =

1 2 5 V

1 25 V l oa d 2 50 V lo ad

Bender IMD relay(1)

G F

= r e s

i s t a n c e

b r e a

k d o w n

t o 1 0 0 0 O h m s o n

t w o

l e g s

i . e .

c a

b l e u n

d e r w a

t e r

( B a

l a n c e

d f a u

l t s

i t u a

t i o n

)

AMP measuring mode

Ungrounded 125/240 VDC system with BENDER IMD

Ground Fault Location in an Ungrounded System

Locating ground faults in an ungrounded system is simple with

the right technology. The techniques are different than loca-

ting ground faults in a grounded system. In a grounded system,

locating faults is done via a multi-channel Ground Fault Relay

utilizing current transformers to pick up on leakage current for

each individual circuit/load. However, due to the nature of theungrounded system where a first ground fault will not create

leakage current, a different technique must be employed.

Ground fault location in an ungrounded system can be done via

a fixed installation, portable devices, or a combination of both.

A controlling device with a pulse generator is present upstream in the

system. This device sends a low level artificial signal into the faulted

system. The signal will be impressed between the power wires and ground.

Naturally, it will follow the ground fault path into ground and return to

the pulse generator. This signal can be traced with special fixed current

transformers or a special portable current probe. This method works

while the system is still online, and ground faults can be located down

to the load causing the problem while all systems remain in operation.

Ground Fault Location - Fixed Installation

The fixed installation is useful where 24/7 monitoring is required,

as well as giving portable location a head start as to which cir-

cuit is causing the problem. The system consists of the following:

- IRDH575 Ground Fault Detector and Controller

- EDS460 or EDS490 Ground Fault Location Devices

- W series current transformers

The Bender EDS ground fault location - detection system is an

excellent tool for the maintenance personnel in a large facility

with extensive wiring. Faults will be located automatically during

normal business operation. No shutdown is required. No hand-

held tracing and/or accessing panels is required. The beauty of this

system lies in its non invasive operation. The ungrounded system is

only safe for its user as long as the occurring faults are immediately

traced down and eliminated. If that is not the case, then the second

ground will follow sooner or later and short circuit the system.

Ground Fault Location - Portable

The EDS3090 portable ground fault location series can be used as

a completely standalone location system or used in tandem with

installed units. Pulse generation is done either by an installed IRDH575

or a portable pulse generator that can be connected up to the main

system. The pulse is traced via a hand-held clamp. The general pro-

cess for this system is by starting at the point of pulse generation,

and tracing the pulse down to the load causing the ground fault withthe clamp. Ground faults can be located quickly and easily while the

system remains online and operational. Using the EDS460 and EDS490

installed ground fault locators in tandem with the portable EDS3090

system gives technicians a head start as to where to begin clamping.



14


Grounded Systems

Grounded Systems

Grounded systems are derived from a power source where the neutral

is solidly tied to ground via a ground neutral bonding jumper (NG).

Often encountered is the typical three phase 208/120V Y or 480/277V Y

configuration. Another possibility is a single phase transformer where

the neutral is tied into ground or sometimes, in very rare occasions,

corner-grounded delta configurations are employed. The general

public is very familiar with solidly grounded systems due to the fact

that nearly every residence in the U.S. is derived from a 240/120V trans-

former with center tap. The center tap is bonded solidly to ground.

As always, there are advantages and disadvantages to the grounded

power system. One disadvantage is the high amount of possible fault

current in a ground fault situation. Fire damage or personnel injury

can occur. Nevertheless, a tripped overcurrent breaker or a GFCI

will enable the electrician to quickly identify a faulty branch. Action

will often be taken after a fault has occurred. Preventative main-

tenance is not necessarily associated with the grounded system.

Neutral Ground (NG)Jumper

T2

T3

T1

GND

L1

L2

L3

L1

L2

L3

V

V12

=480 V V13

=480 V

V23

=480 V

V3G

=277 V

V

VNG

=0 V

circuit breakersupply side, 480 / 277 VAC motor, 3 ph

The grounded system.

The magnitude of a ground fault current in a solidly grounded system

can be very high. Its magnitude depends on the system voltage and

the resistance of the ground fault causing part itself. The ground fault

current can easily reach a value which is multiple times higher than

the nominal load current. A simplified calculation will explain how the

high amounts of current are generated:

IF = Fault Current

V3G = Voltage between faulted phase and ground

RGF = Resistance value at shorted point

RGR = Resistance of ground path

RNG = Resistance of neutral ground bonding jumper

A theoretical fault current will be devastating if a dead short

occurs. Nevertheless, a ground fault relay or overcurrent protec-

tive devices should trip immediately and interrupt power from

the load. How many Amps would flow if a human would touch the

same circuit? Answer: Replace the dead short value of 0.1 Ohm

with a more realistic figure for a human body part. Lets assume

that a person is resting on the frame of a motor. For example,

assume 1000 Ω of resistance from phase L3 and a human body.

The current is a multiple of 15 mA, which is considered to be

the let-go value for humans. 50 mA is considered to be lethal.


L1

L2

L3

L1

L2

L3

Motor, 3 ph

T2

T3

T1

GND

Fault 1(break)

Fault 2 (GF)

i.e. dead short

Resistance = 0.1 Ohm

VV

3G=277 V

Fault current path via ground

(resistance assumed 0.2 Ohm) N G

p a t h

( r e s i s t a n c e

a s s u m e d 0 . 1

O h m )

circuit breakersupply side, 480 / 277 VAC

The grounded system with a single ground fault

and broken ground.

Ground Fault Relays on Grounded Systems

Most technicians are very familiar with a current transformer based

ground fault current relay. Even non-technical personnel encoun-

ter them on a daily basis in public restrooms protecting a wall

outlet in a wet area. The operating theory behind the relay is as

follows. A current transformer (CT) or “donut” is placed around the

power wires leading to the protected load. It is important that hot

and neutral wires are fed through the CT. This goes for both, single

phase and three phase systems. One might come across a three-

phase system without a neutral, feeding a pump or an industrialmotor. In this case the three phases only will be fed through the CT.

For three-phase systems, if a neutral is carried out to the load, it

should be fed through the CT. The ground fault relay will still func-

tion properly when monitoring a load not using the neutral.

0.1 Ω 0. Ω 0.1 Ω .




Grounded Systems

The current transformer will always read zero current in a healthy

system even under a full load condition. In accordance with Kirch-

hoffs laws, incoming and outgoing currents will cancel each other

out. Assume a 10A load connected to a 480/277VAC system. 10A

will be fed from the source into the load, therefore 10A will have

to return from the load back to the source. The CT will measure

both simultaneously since it is placed around all conductors.

The schematic below is a typical application of current

transformer based ground fault detection. In a healthy

system, the current across all three phases will equal zero.

A ground fault (as an example, 1 A) will divert some of the current

from the arrangement and bypass the CT via the ground wire,a frame or the building ground and return back to the source.

The new equation for the CT is now: 10A - 5A - 4A = 1A where 10 A

goes into the load, 9 A returns to the source via the phase L2 and

L3, and 1 A returns to the source via the ground wire. The CT will

step the current (1A) down and forward it to the Ground Fault Relay

(GFR). The GFR will then alarm when its set point has been increased.

The GF relay in combination with a zero sequence CT will work in

resistance grounded systems as well. It will run into its limitations

in circuits where waveform modifying equipment, such as Variable

Frequency Drives (VFDs), or rectifier components are installed.

Grounded DC Systems

Bender RCMA devices monitor DC and mixed AC/DC systems.

The unique measuring principle can be used for protection if

the DC system is grounded as shown below. In this case the

negative pole of the DC power supply or the battery is tied into

a chassis or the building ground. The active CT would be placed

around both, the negative and positive conductor leading to the

load. A DC leakage current will bypass the CT through ground.

Variable Frequency Drives

60 cycle GFRs have limitations when the circuitry involves VFDs(Variable Frequency Drives). A variable frequency drive converts

the incoming AC internally into DC, which will then be modulated

again into a variable cycle AC leading to the load. Internal VFD - DC

grounds can not be detected with conventional GFR technology.

The common “passive” CT needs alternating currents to detect a

ground fault, therefore DC currents will go unnoticed. Some drives

may be equipped with their own internal scheme to detect ground

faults which will eventually trip in the high Ampere range. Early war-

ning or personnel protection cannot be guaranteed in this case.


T2

T3

T1

GND

L1

L2

L3

L1

L2

L3

I1=10 A Fault 1

(isolation)

I1=5 A

I1=4 A

I1=1 A

Bender

GF relaywith summation

transformer


transformer,passive

motor, 3 ph

The grounded system with single ground fault

with ground fault relay.

L+

L-

I(L+)

=10 A

BENDER RCMA relay

with active transformer

+

- I(L-)

=9 A

Fault(isolation)

IF=1 A

V

V ( L - G ) = 0 V

V

V ( L + G ) = 2 4 V

G N D

T2

T1

A1

A2

F1

F2

circuit breakersupply side, 24 VDC

transformer,

activemotor, DC

Grounded 24 VDC system with single fault and

RCMA technology


T2

T3

T1

G N D

L1

L2

L3

L1

L2

L3

diode SCR

Rectifier Inverter EMI filter DC link

PossibleACfault

60Hz

Capacitive

leakagethrough

EMI filters

Internal

DC fault

AC fault

Variable

cycle

AC faults


BENDER RCMA relay

with active transformer

variable frequency drive motor, 3 ph

The grounded system with drive and RCMA technology

Other issues include: EMI filters sometimes incorporated into drivescan provide a leakage path to ground and add to the overall system

leakage; multiple KHz carrier frequencies used can cross the gap bet-

ween insulation and ground; and harmonic content. The solution: Pro-

tect by means of an active current transformer with built-in filtering

technology. RCMA devices employ a double-coil system which enables

them to accurately measure AC, DC, and mixed AC/DC currents from 0

to 2000 Hz.



Solutions For Your Electrical Safety Needs

With our complete portfolio of relay protection products

For over 70 years, BENDER has been a leader in meeting elecrtical safety needs with our large portfolio of ground fault

protection products. BENDER products enhance the safety of electrical systems and help to save money, reduce down-

time, and give the peace of mind that your system is protected by the latest in electrical safety technology.

n Ground Fault Monitors and GFCIs for grounded and high-resistance grounded systems

n Ground Fault Detectors for ungrounded systems

n Voltage, Current, and Frequency Relays

n Remote Communication Solutions

General Purpose Protection RelaysGround Fault Protection for Ungrounded Systems

Ground Fault Protection for Grounded Systems

n A-ISOMETER® Ground Detector Series

n EDS Ground Fault Location Systems

n RCM Series Ground Fault Monitors for Single-Phase and

Three-Phase AC Systems

n RCMA Series Ground Fault Monitors for Single-Phase AC,

Three-Phase AC, and DC Systems

n RCMS Series Multi-Channel Ground Fault Monitors for

Single-Phase AC, Three-Phase AC, and DC Systems

n Lifeguard Series Ground Fault Circuit Interrupters for

Single-Phase AC, Three-Phase AC, and DC Systems

n Undervoltage and Overvoltage Relays for AC and DC

Systems

n Overfrequency and Underfrequency Relays

n Overcurrent and Undercurrent Relays for AC and DC

Systems

Communication Solutions

n Standard Protocol Converters for Ethernet, MODBUS, and

PROFIBUS

n Customizable Visualization Capabilities

n Simple System Integration

Visit www.bender.org for information, tools, and more:n Complete listings of products, documentation, datasheets, and technical information

n Knowledgebase of technical information answering your ground fault questions

n Product selection tools, including ground fault relays, currrent transformers, and more

n Local representative information

Canada

5 Edvac Dr, Unit 14 • Brampton, ON L6S 5P3

Toll-Free: 800-243-2438 • Fax: 905-799-3051

North American Headquarters

700 Fox Chase • Coatesville, PA 19320

Toll-Free: 800-356-4266 • Fax: 610-383-7100

USA, West Coast Office

4555 West Chermak St • Burbank, CA 91505

Toll-Free: 800-236-3378 • Fax: 818-565-3552

www.bender.org • E-mail: [email protected]

Bender Brochure

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