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Topic Title: merlin gerin breaker
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Created On: 21 January 2013 04:35 AM
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 21 January 2013 04:35 AM
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BESATSAKEN

Posts: 6
Joined: 20 January 2013

Fellow electrical practitioner;

I would like to post a problem on my merlin gerin breaker which rondamly trips during start of its pump load. the trip indication is always earthfault. I made insulation tests of the pumps (2 line pumps rated 7.5hp and 1 supply pump rated 60hp) and found them good with all in Giga ohms. Likewise the insulation resistance of the cables from the breaker to load is good at Giga ohms. The pumps have MCC and during the start of any pump, the merlin gerin breaker trips and no trip occurs at the MCC individual breaker. During one time the pumps are set to run, i set-up 1 clampmeter on the neutral cable to check if there is an abnormal spike during starting. I found no rise at all on the current (4 Amp but the setting for earthfault is 500 A) but there is an earth fault trip. Could it be possible that i have a nuisance tripping. I am suspecting now the merlin gerin breaker as the problem.
 21 January 2013 04:16 PM
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sfchew

Posts: 589
Joined: 10 December 2002

Test the earthfault protection by primary current injection. It appears that starting currents created the random trippings. Earthfault protection is based on residual currents. Poor CT connections may also be a cause.

Is the EF in time delay mode?

Regards
Chris Chew
 22 January 2013 05:02 AM
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BESATSAKEN

Posts: 6
Joined: 20 January 2013

Yes, the earthfault has a time delay in "on" of 0.4 sec. of 500 A eartfault setting. As I observed in my fluke clampmeter clamped in the neutral cable (its where the Neutral sensor is clamped feeding to earthfault processor in breaker) during starting of pump, it is very small compared to the 500 A setting, But it is still tripping. I'm still taking consdierations on every possible cause of such tripping.Thank you of your recommendation.
 23 January 2013 07:55 PM
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cookers

Posts: 204
Joined: 10 February 2012

Schneider produce various protection schemes for restricted earth fault etc using CT's and or Rogowski coils.

It could be a breaker problem or even CT's or neutral earth point in wrong position.

I would start by asking Schneider.
 25 June 2013 10:59 AM
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TanyaVisco

Posts: 1
Joined: 25 June 2013

Hi,

I am looking for Merlin Gerin Distribution Board - 16way, 3phase and 60a. I was informed that the lowest amp they do is 125a and if i want to lower it I need to purchase additional rccd? Is this info correct?

Many thanks!!!!
IET » Energy » merlin gerin breaker

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