Incoming tails problem, loss of power in apartment

[TheCodboy]

Looking for some help with this one. Had a call to an apartment today, reporting a loss of power. Got to the job and sure enough nothing on the incoming tails. Went to the meter cupboard where we have a 3 phase incomer, going to banks of BS5419 100a isolators, then to the meter, then to a DP isolator, then the tails from there go through the fabric of the building to the flat about 30/40 meters away. We have 240v coming out of the isolator (L-N) but not at the DB. So, I isolated and removed L-N from the outgoing side of the DP iso and out of the main switch from the DB. IR tested the tails at the DB end, 0.01 at 500v and also a continuity reading between them (700ohms). Carried out the same test at the meter end, IR >999 and no continuity (as should be expected). So its appears that up to one point the cable is fine, and then it appears to have a dead short somewhere. So, if there was a dead short on the tails, Surely there would have been a rather large bang somewhere? Cant physically trace the tails as they disappear into the building in the meter cupboard and dont appear back till the DB in the flat. Building was constructed late 90's-ish. Any help here would be appreciated as the lad in the flat has 2 kids and no power!!

 

[loz2754]

I suspect there's maybe another fused isolator somewhere.

 

[TheCodboy]

I suspect there's maybe another fused isolator somewhere.

There's no communal areas,risers etc. There's a meter cupboard and that's it. Even if there was another isolator, how would I be getting a virtual dead short between L-N?

 

[westward10]

700 ohm is not a dead short it would only create 0.30A.

 

[TheCodboy]

700 ohm is not a dead short it would only create 0.30A.

No,I have an ohms reading of 700 when the tails are separated at both ends. I have an IR reading of 0.01. this is at the DB end. At the meter end we have an IR reading of >999 and no continuity.

 

[littlespark]

Are you sure you disconnected the right flats tails at the supply end?

what is the cable type between plant room and flat? Curiosity.

 

[TheCodboy]

Are you sure you disconnected the right flats tails at the supply end?

what is the cable type between plant room and flat? Curiosity.

He had a new meter and isolator installed this morning after he called his energy provider. It's the only meter there with a DP isolator and the customer tells me it's definitely that meter & isolator.

 

[snowhead]

Ist rule of fault finding, gather information and trust none of it unless YOU can verify it.

Assuming correct tails each end,
Then it could be the tails have been cut or drilled through and are touching (to earth) in the direction of the D.B and separated in the direction of the Cutout.

Depending on the building layout it could have been a hole drilled from outside,.

 

[TheCodboy]

Ist rule of fault finding, gather information and trust none of it unless YOU can verify it.

Assuming correct tails each end,
Then it could be the tails have been cut or drilled through and are touching (to earth) in the direction of the D.B and separated in the direction of the Cutout.

Depending on the building layout it could have been a hole drilled from outside,.

I've asked him to get the meter number from the provider so I can double check

 

[westward10]

You need to do continuity tests with them disconnected and linked to the cpc.

 

[Howard Hindle]

Looking for some help with this one. Had a call to an apartment today, reporting a loss of power. Got to the job and sure enough nothing on the incoming tails. Went to the meter cupboard where we have a 3 phase incomer, going to banks of BS5419 100a isolators, then to the meter, then to a DP isolator, then the tails from there go through the fabric of the building to the flat about 30/40 meters away. We have 240v coming out of the isolator (L-N) but not at the DB. So, I isolated and removed L-N from the outgoing side of the DP iso and out of the main switch from the DB. IR tested the tails at the DB end, 0.01 at 500v and also a continuity reading between them (700ohms). Carried out the same test at the meter end, IR >999 and no continuity in (as should be expected). So its appears that up to one point the cable is fine, and then it appears to have a dead short somewhere. So, if there was a dead short on the tails, Surely there would have been a rather large bang somewhere? Cant physically trace the tails as they disappear into the building in the meter cupboard and dont appear back till the DB in the flat. Building was constructed late 90's-ish. Any help here would be appreciated as the lad in the flat has 2 kids and no power!!

 

[Strima]

The customer should have the meter serial number on their suppliers bill.

 

[TheCodboy]

You need to do continuity tests with them disconnected and linked to th

The customer should have the meter serial number on their suppliers bill.

It's a brand new meter,only installed Friday morning.

 

[snowhead]

Did the energy supplier fit the meter and isolator after being notified of loss of power, in an attempt to resolve it?

 

[TheCodboy]

Did the energy supplier fit the meter and isolator after being notified of loss of power, in an attempt to resolve it?

Yeah that's the scenario. The meter guy proved 240 coming out of the DP isolator and that's as far as he went.

 

[ipf]

Yeah that's the scenario. The meter guy proved 240 coming out of the DP isolator and that's as far as he went.

Those jokers are better at reading meters than fault finding.

If a supply fault's been reported to the supply authority they wouldn't have sent a meter installer to solve things by changing the meter.

If they did, It's worrying.

 

[snowhead]

Is the power still off to the apartment?

Makes you wonder what was going through the meter fitters head whilst they were there going to all that trouble and still not fixing the problem.

 

[Strima]

Did the meter monkey get the cables in the clamps and tighten them up?

 

[TheCodboy]

Those jokers are better at reading meters than fault finding.

If a supply fault's been reported to the supply authority they wouldn't have sent a meter installer to solve things by changing the meter.

If they did, It's worrying.

I think the lad rang his supplier rather than the dno.

 

[pc1966]

I have an IR reading of 0.01.

Is that Mohm, as typically for insulation test?

If so, that would be the resolution limit of an IR tester and it could be anywhere from 0 ohm to 20k ohm.

 

[TheCodboy]

So, we have power. Mystery solved. The perfect storm of mistakes hit at once. Firstly, all the meters in the meter cupboard have been marked up incorrectly, So the meter guy changed the meter for what he believed was the correct flat. It wasn't. It now transpires that another meter company were on site earlier on the day he lost power. He didn't know this till yesterday after talking to another resident. Turns out that they had isolated the wrong property. This also explains why i had healthy readings at one end and poor at the other, as his tails were still connected in his meter. So as the saying goes..... Every day is a school day. Many thanks for all your help guys!

 

[timhoward]

This also explains why i had healthy readings at one end and poor at the other, as his tails were still connected in his meter

This sounds like if could have been quite dangerous for you. Glad nothing worse happened.

 

[pc1966]

This sounds like if could have been quite dangerous for you. Glad nothing worse happened.

Indeed, hence the "safe isolation" and check before you poke procedures drilled in. No matter what you think you have switched off, you can never be sure!

 

[brianmoooore]

Reminds me of one I had once. Farmhouse renovation, with a supply to outbuildings and another supply to the house.
Wall with meter, etc. in farmhouse coming down, so supply to be removed, and house fed on sub main from outside.
Requested SWEB to attend and remove supply. Date agreed.
Date came and went by some weeks, contacted SWEB again, and they said the job had been done. Builders can do no more until wall removed, so ladder up the service pole, chop the service cable, remove it all and place meter, cut out, the lot, in a cardboard box.
Meter reader turns up, unfortunately when I wasn't there. Apparently, when presented with the meter in a box, he went bright purple with rage, danced around a bit, before storming off, vowing to have everyone involved prosecuted to the full extent of the law.
Of course, we heard no more about the matter.
A few weeks later, the farmer asked me to attend some farm buildings he rented about three miles away. They had gone over there to shear sheep, and found there was no electricity. The reason was quite obvious. Meter, cut out, and service cable had disappeared.

 

[littlespark]

So I was right at #6?

Glad it sorted now, but no power for a weekend is a bit of an inconvenience to say the least.

 

[brianmoooore]

So have the tenants been paying each others bills as well?

 

[HappyHippyDad]

Are you sure you disconnected the right flats tails at the supply end?

what is the cable type between plant room and flat? Curiosity.

I had a similar problem a year ago, although a little different.

I went to the meter room, switched off switched fuse, back up to the top floor flat, still had power! Tried it a few times, until I realised I'd gone into the meter room for the wrong block of flats ?.

No angry faces out of the window, so I got away with that one. Felt a bit silly.

 

[ipf]

In the early 2000's one apprentice came a cropper in some fairly local flats. They were local authority workers installing mains isolators for council flats. I don't remember the actual details but know he was working alone, with other electricians on site. There was some sort of confusion with supplies and one found him unconscious grasping cables. Awful business all round but it goes to show the definitive, when it comes to safe isolation.