Earth fault/leakage current tracing

[sparkydude]

Hi all , we have a situation on one of our current jobs with a substantial earth leakage , varies from 50A to 3300A the other day for a millisecond LoL, All cables are swa using the armour as cpc, in this scenario obviously we have some hefty cores to deal with and all are three phase. I doubt the meter above would be upto the job as the cables are upto 300mm 4 cores Anyone got a recommendation as to how we would go about tracking this down , bearing in mind we have approx 36 cables to test I was thinking we would need a meter with sepperate clamp cts to go round the cables to monitor it .

Any help appreciated


Nick

 

[telectrix]

think you'll have to go down the route of isolating and IR testing here.

 

[Chr!s]

Whats the supply type, PME?

What sort of equipment is connected?

 

[sparkydude]

Supply is TNCS supplied via two new 11kv transformers sited outside the switchroom. Equipment conected is general submains feeding subpanels and several operating theatres , and a couple of MRI scanners.

We need preferably a non intrusive method of pinpointing the circuit/s with issues as being a hospital isolating parts for any kind of testing is such a nightmare its not funny,


Nick

 

[IQ Electrical]

What did you use to measure the fault duration?

 

[sparkydude]

The fault current is being constantly monitored on the main panels SEPAM unit , and it is constantly registering between 50-70A now , but as said before it spiked once to 3300A for a millisecond

 

[IQ Electrical]

My first action would be to connect a power quality monitor at the main panel, 1 week duration to capture any 'events' in that period.

I'd make sure that records of the times of use of any specialist equipment (such as MRI etc.) were available to compare with any 'events' highlighted during the monitoring.

Has the designer been consulted regarding an expected level of leakage for the installation?

Is the 50-70 Amp leakage present at all times?

 

[sparkydude]

we have been tasked with carrying out data logging on the outgoing ways but are unsure if this is going to help us in finding this circuit/circuits that have the leakage current on them as they are specifically concerned with overloading of existing circuits .

The 50-70A is a constant fluctuating reading from the SEPAM,

I doubt the designer will be interested, the main panel and submains are 25-30 years old


Nick

 

[IQ Electrical]

we have been tasked with carrying out data logging on the outgoing ways but are unsure if this is going to help us in finding this circuit/circuits that have the leakage current on them as they are specifically concerned with overloading of existing circuits .

The 50-70A is a constant fluctuating reading from the SEPAM,

I doubt the designer will be interested, the main panel and submains are 25-30 years old


Nick

Ah, I assumed this was a newly completed installation.

At some point, you will have to look at isolation of parts of the installation, even on a process of elimination basis, a methodical approach is needed.

I can see an extended 'duty test' of the essential services generator or alternative supply source!

 

[malcolmsanford]

I would go along with IQ but I would think that in a 25 yr old installation under those sorts of loads, your having a gland joint go. Can you also get hold and use of a thermal camera and take some pictures of terminating glands, see if you have any hot spots.