Site temps nuisance tripping

[Cazmac1]

Hi Guys I took over a site that had an existing site temps. I haven't got round to testing them yet and plan to do it after xmas. The site temps have been up and running since I been on site some 6 weeks now. I got one of my sparks to cross bond the Swa at the bottom of the site DB as there where no banjos on the swa's and the main supply cable was not bonded to the DB. After Bonding The site stated to experience nuisance tripping, The db is on a 100m amp rcd and the zs at the DB is 0.44 ohm's this is connected to the incoming supply via a time delay rcd set on 300ma. without getting too bogged down has anyone got any quick Ideas as to the reason and how do I prevent it. The site is closed now for xmas otherwise I would have tested the installation. :santa_cheesy:

 

[davesparks]

Was it supposed to be connected to the armour of the swa? Or had it been set up with a seperate earthing system deliberately (which would explain the 100mA RCD

 

[telectrix]

Was it supposed to be connected to the armour of the swa? Or had it been set up with a seperate earthing system deliberately (which would explain the 100mA RCD

the armour should still be earthed at the source.

 

[Cazmac1]

Hi Guys I took over a site that had an existing site temps. I haven't got round to testing them yet and plan to do it after xmas. The site temps have been up and running since I been on site some 6 weeks now. I got one of my sparks to cross bond the Swa at the bottom of the site DB as there where no banjos on the swa's and the main supply cable was not bonded to the DB. After Bonding The site stated to experience nuisance tripping, The db is on a 100m amp rcd and the ze at the DB is 0.44 ohm's this is connected to the incoming supply via a time delay rcd set on 300ma. without getting too bogged down has anyone got any quick Ideas as to the reason and how do I prevent it. The site is closed now for xmas otherwise I would have tested the installation. :santa_cheesy:

sorry guys zs should be ze

 

[Cazmac1]

The supply is earthed at source with a earth rod and is with permitted maximum EFLI readings. The DB main switch is 100m amp to allow for discrimination. All final circuits from the DB are protected by 30 mm rcbo's. I've done nothing other than cross bond all the swa to ensure that all swa have a good earth. I will need to test the whole system when I get back from Holiday. I'm going down the route of nuisance tripping due to earth leakage on the transformers. It either that or the spark working on the db has done something silly but cant see it.

 

[Leesparkykent]

The supply is earthed at source with a earth rod and is with permitted maximum EFLI readings. The DB main switch is 100m amp to allow for discrimination. All final circuits from the DB are protected by 30 mm rcbo's. I've done nothing other than cross bond all the swa to ensure that all swa have a good earth. I will need to test the whole system when I get back from Holiday. I'm going down the route of nuisance tripping due to earth leakage on the transformers. It either that or the spark working on the db has done something silly but cant see it.

I would hope the RCBO's are double pole or single pole switched neutral? Is the 100mA RCD an "S" type?

 

[Cazmac1]

The only other thing done was I got my sparks to mount a rotary isolator on the side of the DB to allow for switching the site temps/transformers off It is this swa that when cross bonded to the others that is causing the trip. If he got the phase rotation wrong would this cause the trip when cross bonding the swa???.

 

[telectrix]

leakage on SWA or the transformer/s????

 

[gnselectricals]

Is it tripping when being isolated ? maybe the switch contacts not opening at the same time

 

[Cazmac1]

Is it tripping when being isolated ? maybe the switch contacts not opening at the same time

No when every circuit is on as soon as the bond is connected to the swa of the transformer Armour it trips. He must have introduced a fault as it was all working for three years prior to me taking control of the site six weeks ago.
I was hoping for a quick pointer from someone who may have come across this type of thing before. I think I'll just leave it till after xmas and test the system. Thanks for your help

 

[telectrix]

start with IR test on the transformer/s and the SWA. maybe bridge the RCD and try to measure leakage with an earth leakage clamp meter.

 

[Cazmac1]

Ok, found out what the **** did. When he disconnect the the 4 core swa to mount the rotary isolator he reconnected the blue cable that was marked as the CPC into the neutral bar. All tested and working fine now.

 

[Farmelectrics]

Ze of 0.44 for a tt system is a good reading never had one as low as that

 

[PEG]

Ze of 0.44 for a tt system is a good reading never had one as low as that

...Maybe that figure is more PSSC than PEFC,if his conductors are all jumbled up...:lips: