Jonathan Woodworth Distribution Grid...application of arresters to mitigate the effect of lightning...

8.4kV MCOV Distribution Arrester

Jonathan Woodworth Arresterworks

Best Application Practices

• Distribution

• Transformer Protection

• Open Point Protection

• Line Protection

• Line Protection on Transmission Towers

• Shunt Cap Protection

• Underground

• Industrial Complex

• Substation

• Distribution Exits

• Wind Farm Collectors

• Small Power Plants

• Underbuilt Systems

8.4kV MCOV Distribution Arrester

Todays Topics

Jonathan Woodworth ArresterWorks 2

Who is ArresterWorks?In 2007 Jonathan Woodworth and Deborah Limburg made the decision to join their business expertise to start ArresterWorks Consulting. Their aim was to provide a resource for those seeking to improve power system reliability through design, production and application of arresters to mitigate the effect of lightning and other transients. Their efforts have lead to ArresterWorks.com which is a website devoted to providing educational information on the topic of surge protection of power systems and a consulting business that continues to grow.

Since 2007 and the start of ArresterWorks, they have developed a comprehensive library of articles on surge protection that is now second to none in the world. They have also developed and honed their transient analysis skills using ATP software to model and problem solve in the industry. They have added on line seminars, e-Consulting, and much more to their list of services to the industry.

3

Jonathan Woodworth• Arrester Design Engineering Manager

• Arrester Marketing Manager

• Worked for Cooper Power Systems for majority of time in industry

• Involved in Arrester Standards for 20 years– Current Chair of IEEE WG on Arrester Testing Standards SPD 3.3.11

– Current Co-Convenor of IEC on Arrester Testing StandardsTC37 MT4

Contact Info: [email protected]

+1.716.307.2431

Deborah Limburg• Arrester and Engineering Software Designer• Worked for Cooper Power Systems for majority of time in

industry• Software designer

– Virtual Documentation of Arrester Products– Arrester Design Software Tools– Manufacturing Process Software

Contact Info: [email protected]+1.716-378-1419

ArresterWorks.com

Jonathan Woodworth ArresterWorks

mailto:[email protected]

mailto:[email protected]

When was the first lightning arrester put into service?

History Quiz

4

Rendition of first lightning arrester as described by Joseph Henry 1850ish

Protecting Telegraph Lines

5

Typical

Power

System

6

1. Because Insulation can fail when subjected to Surges….

2. To Reduce Outages

3. To Reduce Costs and Time of Replacing Failed Equipment

4. Because it makes good Economic Sense

Substation Fires are Costly

When the lights go out we have problemsJonathan Woodworth ArresterWorks 7

Important Considerations in Surge Protection

• Economic Realities must always be part of the Protection Equation

• 100% protection can be costly, but properly placed protection can be very cost effective

• Partial protection of a transmission line can reduce the outage rate by 80% in some cases.

• There is always more than one way to meet your Protection Goals, and they should all be considered

• Sectionalizing to reduce the effect of an outage

• Fuses and Cutouts can reduce outage effects.

• Shield wires can be very effective

• Never Forget the Environmental Impact• Ensure that however you choose to protect your system, it is done with

products that were manufactured in an environmentally friendly facility.

• Consider reusing arresters

• Consider arresters with lower losses

Co

st

Added Benefit


Back to AgendaJonathan Woodworth ArresterWorks 9

Transformer Mounted Arrester

Arrester Line Lead

Arrester Ground Lead

System Neutral

System Ground or Down Conductor

11

Distribution Transformer

Protection

Purpose:

The purpose of this application is to

reduce the risk of transformer failure

due to lightning.------------------------------------------------------------------------------------------------------------------------------------------------

Usage:

>50 million in service in US alone,

>95% of all distribution transformers in

the US are arrester protected------------------------------------------------------------------------------------------------------------------------------------------------

Installation Considerations:

• 15 and 18kV systems may need

wildlife protection

• Some systems are protected with

current limiting fuse as well as

arrester

• Lead length needs to be considered

and kept at a minimum

• Mounting the arrester on the

transformer is the preferred

configurations to keep the leads

short. ------------------------------------------------------------------------------------------------------------------------------------------------


Distribution

Transformer

Protection

-------------------------------------------------------------------------------------------

Another Installation

Consideration

Cross-arm or Bracket

mounted arresters. They do

protect the transformer as

well as tank mounted

arresters. For fast rising

surges the lead inductance

can cause higher than

expected voltage across the

windings of the transformer.

The only purpose of the

arrester is to protect the

internal windings and the

external bushing.

Long Leads reduce protection of transformer


Distribution

Transformer

Protection

Arrester Types Used:

Normal Duty and Heavy Duty

Arresters are both used for

this applications. >80% are

heavy duty. ------------------------------------------------------------------------------------------------

Grounding:

Transformer grounding does

not affect the high voltage

side protection, but can affect

the low voltage side

protection.------------------------------------------------------------------------------------------------

Future Trends:

• Continued migration to the

tank.

• Underoil Arrester

Protection may one day

become popular.

Normal Duty Heavy Duty

High Current

Capability65kA 100kA

Typical Clamping Voltage at

10kA

35-40kV 30-35kV

ND HD


Distribution Transformer

Protection

Failure Considerations:

Arresters equipped with disconnectors

are recommended.

Polymer Housings are safer than

porcelain housings for this application------------------------------------------------------------------------------------------------------------------------------------------------


Historical

Distribution

Transformer

Protection

Historical:

Expulsion arrester with >60 years of use.

Unit on right has blown its porcelain

housing off and continues to protect

Historical:

Circa 1950-60 internally and externally

gapped arrester. Note no disconnector

used since it is externally gapped. -


Arrester Value Consideration for Distribution Transformer

Protection

When a lightning strike directly hits a line near a transformer without an arrester there is a 100%

probability it will cause the transformer to fail. If an arrester is installed on the transformer, this

probability becomes nearly zero.

0-.1

.1-.5.5-1

1-2

2-3 3-4

4-56-8

5-68-10

10-14Using this calculator you can see just how often

an arrester saves a transformer over its

lifetimeJonathan Woodworth ArresterWorks 17

OVP Supporting Documents/Distribution_Arrester_Value_Calculator.xlsx

Ground Flash Density and Number of Transformers Saves in 20 years

-

5; 5.4

8; 8.76; 6.5

10; 10.9

14; 15

GFD; Saves in 20 years

4; 4.3

3; 3.2

2; 2.1

1; 1

.5; .5.1; .1


Open Point

ProtectionPotentially

Open Switch


Open Point and Switch

Insulation Protection

Purpose:


reduce the risk of insulator flashover.

The issue here is that open points can

lead to voltage doubling and if there is

no arrester at an open point a

flashover is more likely

------------------------------------------------------------------------------------------------------------------------------------------------

Usage:

Approx. 20% of inline switches are

protected by arresters. It is very utility

specific------------------------------------------------------------------------------------------------------------------------------------------------


Since the surge can come from either

direction, arresters on both side of the

switch are recommended.

------------------------------------------------------------------------------------------------------------------------------------------------

Potentially

Open Switch


Open Point /Switch



Disconnectors are recommended to

avoid a long term outage------------------------------------------------------------------------------------------------------------------------------------------------


Normal and Heavy Duty Arresters are

both used.------------------------------------------------------------------------------------------------------------------------------------------------

Grounding:

Pole ground level is not relevant.------------------------------------------------------------------------------------------------------------------------------------------------

Future Trends:

No obvious ones emerging however if

momentary outages are to be reduced,

this application is an option------------------------------------------------------------------------------------------------------------------------------------------------

Historical:


reduce the risk of transformer failure

due to lightning.------------------------------------------------------------------------------------------------------------------------------------------------

Value Consideration

Since an insulator flashover seldom

results in a long term outage or

equipment damage, this application is

hard to justify------------------------------------------------------------------------------------------------------------------------------------------------

Open Switch


Open Point /Switch



Congestion can be a issue so lead

management and disconnectors are

important------------------------------------------------------------------------------------------------------------------------------------------------

Open Switch


Distribution

Line

Protection


Distribution Line Protection

Purpose:


reduce insulator flashover caused by

lightning------------------------------------------------------------------------------------------------------------------------------------------------

Usage:

>20 million in service in US

More in southern states where

lightning occurrence is higher------------------------------------------------------------------------------------------------------------------------------------------------


The 4 per mile rule reduces outage

rates by just a few percent if at all

A Zero lightning induced outage rate

can be achieved with arresters on

every insulator.

Lead management is important. If the

arrester fails, the line BIL needs to be

restored to full insulator level. ------------------------------------------------------------------------------------------------------------------------------------------------



Installation Considerations

Protecting only the top phase makes it

act like a Overhead ground wire.

Backflash on other phases needs to be

considered.



both used.

------------------------------------------------------------------------------------------------------------------------------------------------

Grounding:

Pole ground levels are not relevant in

this application. Lower ground

resistance will increase the current

through the arrester, but not improve

the line protection.------------------------------------------------------------------------------------------------------------------------------------------------

Isolated Down

Ground


Distribution Line

Protection

“End Point Protection”

Special Case

Similar to an open point is the

dead end pole. As with an open

point, voltage doubling can occur

and insulator flashover is at a

higher risk if arresters are not

installed.--------------------------------------------------------------------------------------------------------------------




Watch leads after failure.

Polymer housings are recommended

for circuits with >1kA fault current----------------------------------------------------




This is a good example of how a

polymer housed arrester acts if it fails.

The ground lead disconnector moves

to a good distance from the arrester,

the polymer housing has come off and

arrester is isolated from the system.


The future of Line protection EGLA


Distribution

Line

Protection

on

Transmission

Line Towers

(Lightning Protection of

Underbuilt Circuits)


Underbuilt Distribution

System Lightning

Protection

Purpose:


mitigate the risk of backflash from the

down ground to the phase. Could be

for line insulators or distribution

transformers------------------------------------------------------------------------------------------------------------------------------------------------

Usage:

If for transformers, 100% usage. If for

line protection, limited usage------------------------------------------------------------------------------------------------------------------------------------------------


Must be on every phase of every tower

to be effective.

Lead length for line protection is not an

issue. Lead length for transformer

protection is still an issue------------------------------------------------------------------------------------------------------------------------------------------------


Underbuilt Distribution

System Lightning

ProtectionFailure Considerations:

Managing lead length is important.

Disconnectors are recommended------------------------------------------------------------------------------------------------------------------------------------------------


Normal or Heavy Duty can be used.

Heavy Duty seems to be the dominant

arrester applied here. However normal

duty would do perfectly since current

levels are always low.------------------------------------------------------------------------------------------------------------------------------------------------

Grounding:

If the pole grounding is good, backflash

to the underbuilt circuit is a lower risk.

If arresters are used to protect the

underbuilt circuit, the ground

resistance is not relevant for

protection.------------------------------------------------------------------------------------------------------------------------------------------------

Future Trends:

This is a growing application since

right-a-ways are harder to gain so

using distribution right-a-ways for T-

Lines is on the increase.------------------------------------------------------------------------------------------------------------------------------------------------


Distribution Shunt

Capacitor Protection

34

Distribution Shunt

Capacitor and Switch

Protection



both used.------------------------------------------------------------------------------------------------------------------------------------------------

Grounding:

Pole ground level is not relevant.-----------------------------------------------------------------------------------------

Trends

This application is increasing with the

need for improved power quality

Cap Switch

Cap

Ground Nut Wildlife ProtectorProtector

35

Distribution Underground Circuit Protection


Riser Poles, Terminators and URD Cable

Underground Cable

Terminator for transition to underground

Riser Pole Arrester

System Neutral

Short Ground Lead

Short Line Lead

37

The Voltage Doubling

Phenomena

When a surge travels down the

line, it is reduced in amplitude by

the Riser Pole Arrester. When the

reduced surge reaches the pad

mount arrester it doubles.

38

Distribution Riser Pole

Protection (Also called

terminal pole or dip pole)

Purpose:


reduce the magnitude of the surge that

travels past the arrester into the

underground circuit. Lowest possible

levels are desired to reduce the affect

of doubling at the end of the

underground cable.

Both transformers and cable are being

protected by the riser pole arrester------------------------------------------------------------------------------------------------------------------------------------------------

Usage

It is rare to see an underground cable

unprotected anywhere in the world.

Even in low lightning areas,

underground terminal poles are

equipped with arresters. ------------------------------------------------------------------------------------------------------------------------------------------------


Locating the arrester as close as

possible to the terminator and keep the

leads short

URD Cable

Cable Terminator

Jonathan Woodworth ArresterWorks 39Exacter Grid Resiliency Conference Nov 13-15, 2018



terminal pole or dip pole)------------------------------------------------------------------------------------------------------------------------------------------------


An example of how not to install riser

pole arresters. The arresters are

mounted far above the terminators.

This causes extra high surge entering

the underground cable.

Remember the voltage at the end point

doubles and if it enters the system

higher than it should, when it doubles

the risk of equipment failure is higher




terminal pole or dip pole)



both used.------------------------------------------------------------------------------------------------------------------------------------------------

Grounding:

Pole ground level is important to keep

the surge magnitude that enters the

cable as low as possible relative to

ground.-----------------------------------------------------------------------------------------

Trends

This application will continue to grow

as underground residential housing

grows.


Distribution Underground Padmount Transformer or

SwitchgearPurpose:

Purpose is to protect end points and pad mount transformers from lightning

surges that travel on the line past the riser pole arrester. ------------------------------------------------------------------------------------------------------------------------------------------------

Usage:

20-30% of this type of equipment is protected with arresters. Many believe that

the riser pole is sufficient. ------------------------------------------------------------------------------------------------------------------------------------------------


There are many housing configurations. There is always congestion. If the

arrester design blows out the bottom when if fails, make sure there is room for

this event.------------------------------------------------------------------------------------------------------------------------------------------------


The elbow arrester is always used at this location. Some are normal duty but

standards only call for light duty------------------------------------------------------------------------------------------------------------------------------------------------

42Exacter Grid Resiliency Conference Nov 13-15, 2018

Protecting theIndustrial Complex


Distribution SwitchgearProtection

45

Distribution Switchgear ProtectionPurpose:

The most common purpose is protect transformers,

motors and variable frequency drives from

switching surges caused by prestriking and re-

striking breakers

Lightning surges that manage to find their way to

switch gear are usually of very low current

magnitude------------------------------------------------------------------------------------------------------------------------------------------------

Usage:

Very misunderstood application so arrester are used

where they should not be and not where they should

be. ------------------------------------------------------------------------------------------------------------------------------------------------


Ground lead disconnectors are not used enough. ------------------------------------------------------------------------------------------------------------------------------------------------


Fault current can be very high in these applications

so sometime a station class arrester should be

used.------------------------------------------------------------------------------------------------------------------------------------------------


Normal duty , Heavy duty, Intermediate and Station

class are all used in this application.------------------------------------------------------------------------------------------------------------------------------------------------

Back to AgendaJonathan Woodworth ArresterWorks 46

Protecting Small Power Plants

Back to Agenda Jonathan Woodworth ArresterWorks 47

•

Rotating Machinery

Protection

Purpose:

Reduce the risk of winding

damage from switching

surges or system flashovers--------------------------------------------------------------------------------------------------------------


Lead length and location are

critical. Generator and

motor windings have very

low impulse withstand also.

Surge Capacitors often used

in conjunction with arresters

for this application-------------------------------------------------------------------------------------------------------------

Failure Mode:

High fault current may be

available

1MW

Generator

15kV


•

Rotating Machinery

Protection

Usage:

Vastly under utilized application.

High value assets go un protected

due to lack of understanding of this

option--------------------------------------------------------------------------------------------------------------

Surge Pack

• 1 3phase .25uF cap

• 3 18kV rated Intermediate

Arresters

Surge

Capacitor


Back to Agenda 51

Types of Arresters:

Station or Intermediate arresters

without disconnectors are

recommended.------------------------------------------------------------------

Value Considerations

This arrester eliminates the

significant insurance claims that

occur after unprotected events.

The arrester should be easily

justified

Underbuilt Line Protection from Higher

Voltage AC Line DropsPurpose:

To clamp the 60hZ voltage at a safe level if a higher

voltage line drops on the underbuilt circuit--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------


The arrester must remain on the circuit until the event is

over and shunt all higher voltage fault current during the

process--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Failure Mode:

High fault current may be available. Fault indicators can

assist in showing operation----------------------------------------------------------------------------------------------------------------------------------

ArresterFacts 022 – The Underbuilt Line Arrester


ArresterWorks Knowledge CenterArresterFacts are a compilation of facts about arresters to assist all stakeholders of Arresters in the application and understanding of arresters

53

Services

• Arrester Failure Analysis

• Insulation Coordination

• Substation Assessment

• Expert Witness

• Arrester Design

• e-Consulting

Exacter Grid Resiliency Conference Nov 13-15, 2018 Jonathan Woodworth ArresterWorks 54

Jonathan Woodworth Distribution Grid...application of arresters to mitigate the effect of lightning...

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