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sarmapratap
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Join Date: Sep 2011
Posts: 3

Failure of Lightning Arrestors

09/12/2011 3:33 AM

We have installed lightning arrestors type 1 (MO type) with booster transformers on railway traction. Recently the line is energized but we are facing a problem, the lightning arrestors with booster transformers in a particular sections are only failing. I want to know

1) Whether the lightning arrestor's are defective

2) Lighting arrestors are under rated (The nominal voltage is 25KV and the rated voltage is 38.5kv)

3) We have modified earthing arragnement and provided a seperate earth electrode, even then it is failing.

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electricalexpert65
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Join Date: Oct 2009
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Good Answers: 169
#1

Re: Failure of Lightning arrestors

09/12/2011 7:39 AM

What is te method of your system earthing?
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sarmapratap
Participant

Join Date: Sep 2011
Posts: 3
#2
In reply to #1

Re: Failure of Lightning arrestors

09/12/2011 10:07 AM

There is one earth wire running parallel to track for both up and down lines and there are intertrack bonds, structure bonds and structure to earth wire bond at an average distance of 350mtrs. Where the lightning arrestor is installed, it is directly earthed to the earth wire.

Regards

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Bluestone
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Join Date: Nov 2006
Location: OH USA
Posts: 549
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#3

Re: Failure of Lightning Arrestors

09/12/2011 10:46 PM

You may be exceeding the arrester's TOV (temporary overvoltage) capability. Remember surge arresters are only intended to discharge impulse overvoltages; not AC or DC (in the case of special DC traction surge arresters).

Review the circuit source and connections to make sure the available system voltage across the arrester terminals does not exceed the arrester TOV rating. This is particularly important with gapless MOV arresters.
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bubbapebi
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Join Date: Apr 2007
Posts: 414
Good Answers: 19
#4
In reply to #3

Re: Failure of Lightning Arrestors

09/13/2011 12:52 AM

Yep. Here's some more detailed information, courtesy of GE, one manufacturer of this type of device. You might inquire about comparable equipment from your vendor.

http://www.geindustrial.com/Newsletter/lightning_arresters_guide.pdf
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WAWAUS
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Join Date: Aug 2010
Location: Melbourne, Australia
Posts: 740
Good Answers: 24
#5

Re: Failure of Lightning Arrestors

09/13/2011 5:00 AM

A couple of thoughts:

25kV AC RMS -> 35.35kV peak.

How clean is the waveform? - are there spikes on it? If so how big? how frequent?

Is the a DC offset?

In a Railway traction system I would expect there to be significant spikes from the motors being impressed on the supply as they pass your arrestors - not to mention significant back EMF during braking ......
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sarmapratap
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Join Date: Sep 2011
Posts: 3
#6
In reply to #5

Re: Failure of Lightning Arrestors

09/13/2011 8:21 AM

THE MAXIMUM SYSTEM OPERATING VOLTAGE RECORDED IS 26KV AND HENCE TOV MAY NOT BE THE CASE.

WE SUSPECT THE 19TH HARMONICS IS AFFECTING THE SYSTEM. CAN IT HAPPEN DUE TO IT.
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Users who posted comments:

Bluestone (1); bubbapebi (1); electricalexpert65 (1); sarmapratap (2); WAWAUS (1)

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