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Test certification & changes to supply characteristics

TaZ10101

Looking for some guidance please, I am working on a construction site with a large temporary accommodation block due to be occupied asap. Due to design issues the HV/ LV supply has been delayed, to work around this a generator will be utilised as a short term solution. 
This means testing & inspection will be completed via the genset and certs issued, when the new substation is completed the generator will be disconnected and sub-mains will be connected to the permanent LV supply. 
This raises a question regarding re-test, in my experience usually best practice would be a full re-test, but some on the project are suggesting only the sub-mains will require re-testing. 
To me this would probably come down to the designer signing the test cert and what they are prepared to accept, if only re-testing the sub-mains  I would think the final circuits Zs/ Pfc would have to be calculated as the previous test results/certs from the generator would be invalid due to the change of supply characteristics right?

So can anyone offer advice as to the options and is there anything in BS7671 regs that would be relevant to this situation, it’s also worth considering that if a EIC is issued for the generator can there be another issued for the LV supply? Is it possible to issue more than 1 EIC or  update the original or would be a condition report? 
I’ve come across this situation before and it always seems to be a contentious subject with lots of different opinions, sorry for the long winded post, but would really appreciate some professional opinions on this, thanks Pray 

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    It rather depends what changes when the final supply is connected. As others have alluded it will really be PSSC and Zs and anyy circuits that are being paralleled up for the genset that may be split once power arrives.

    IF the first set of tests on the genset are done with a nod to this, (most gensets do not really have a PSSC that is as high as predicted by the test gear that does a small voltage drop test, preferring to stall or to drop out of regulation)  it should be possible to minimise duplicated testing.

    To that end a few more DC dead results of Z2 in some key places may be needed where the fault path will change on re-connection. Then a live PSSC/Zs test on the new supply, and the rest is probably calculation adding the DC test results and the new Zs,  and an inspection of the actual  new connections .

    The real question has to be could a dangerous condition sneak past such hybrid testing that would have been found on a full retest. I suspect that with care the answer can be arranged to be 'no'.

    What you write on the paperwork will also need some thought, as it will be dead tests of ABC on one day live tests with genset of XYZ  and then a little bit of final test on new supply.

    M

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  • 0

    It rather depends what changes when the final supply is connected. As others have alluded it will really be PSSC and Zs and anyy circuits that are being paralleled up for the genset that may be split once power arrives.

    IF the first set of tests on the genset are done with a nod to this, (most gensets do not really have a PSSC that is as high as predicted by the test gear that does a small voltage drop test, preferring to stall or to drop out of regulation)  it should be possible to minimise duplicated testing.

    To that end a few more DC dead results of Z2 in some key places may be needed where the fault path will change on re-connection. Then a live PSSC/Zs test on the new supply, and the rest is probably calculation adding the DC test results and the new Zs,  and an inspection of the actual  new connections .

    The real question has to be could a dangerous condition sneak past such hybrid testing that would have been found on a full retest. I suspect that with care the answer can be arranged to be 'no'.

    What you write on the paperwork will also need some thought, as it will be dead tests of ABC on one day live tests with genset of XYZ  and then a little bit of final test on new supply.

    M

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