Intermittent ELCB Failure

There is a fault, which has personal safety implications. It can be found by disconnecting each individual circuit downstream of the ELCB and measuring ohms between the earth conductor and the neutral conductor of this circuit in turn. Find out what is causing it and remove it.

If in doubt, consult a qualified electrician.

Hi,

We have perfoemed insulation test for all electrical panel for all phase, found ok. Neutral is common in all circuits. Spark at one end in circuit will affect the ELCB at different end just because of neutral????

What happens to load if Neutral opens? We have 3 phase UPS which generates power in case of power failure but same time neutral was also cut by input breaker. We have all load in single phase. UPS output is Delta hence only 3 phase will be as output.

Look elsewhere. The fault is a neutral-to-earth connection in a circuit downstream.

The ELCB hasn't "failed"; it is merely doing what it is supposed to by disconnecting the downstream service in the event of an earth fault for safety reasons. Depending on its severity, in the absence of the ELCB the fault would manifest itself otherwise as a shock that is strong enough to kill, to a fault that would disconnect an overcurrent device, to a fire causing process materials and/or time loss, damage to the facility, injury or death. So stop work, investigate, and remove the fault as a matter of high priority.

Hire an electrician

so why don't you replace it with another one?

If you have the same tripping problem, then as stated in an earlier comment, the trip is doing it's job and you have a problem somewhere else!

It is an intermittent, and you already performed reasonable tests, as I understand. Feeding the instrument(s) thru an isolation transformer (50/60Hz, 1:1) can verify the negative: If no more tripping, it was really caused by one of the instruments. Then eliminate one by one. A side benefit is, that the pesky and dangerous leak cannot occur thru an isolation transformer.

That's nonsense. With the isolation transformer looking after the trip, the fault, assuming it is still there, is now presenting at the terminals of the isolation transformer instead, with the same implications.

One might as well simply ditch the ELCB!

My mistake.

My long professional life long I was tracking and eliminating intermittent ground fault currents by introducing a (low capacity primary vs.secondary) 1:1 isolating transformer. In days or weeks the offending instrument was located, repaired or discarded.

Where I live ground fault relays are standard. If that is not feasible, double insulated construction, with very high insulation value in the primary transformer is required.

I might have led a sheltered life, as I have never encountered a stray voltage sensing gizmo. Nor did I miss it.

Seems that ELCB is behaving like RCCB .

ELCB - Voltage type with Lab instruments being connected in common ground ( to nearby wall/window/ground connection ) can solve this observation .

Residual current could be making these such scenarios , please .

How can you have an electrical incoming supply arrangement for UPS which trips when the supply is interrupted. This smacks of poor engineering logic and application. Is it deliberately designed to trip. If not, please remove UV coil or any other scheme which isolates the supply. Another serious flaw is the incomer breaker is 4 pole and common neutral is extended to load side also. In case the breaker trips (like what is happening now), neutral will be isolated leading to disastrous results to connected single phase loads. You are sitting on a potential bomb which can blow on your face. thank your stars it has not happened till now. i will strongly recommend you to immediately replace the incomer breaker with TP breaker with non isolatable neutral. Regarding trippng of ELCB, I suspect intermingling of UPS neutral (after the ELCB) and raw power neutral. Please check the wiring. I will also advice you to check the UPS neutral current for high level of harmonics. If harmonics are present, please replace the ELCB with high immunised type "D" curve ELCB. Higher E-N voltage in only D.G mode indicates loose connection in D.G neutral circuit. Please check right from D.G system up to the EB / DG changeover arrangement. Get a competent electrical engineer to have look at the installation. If I were you, I would also go in for ultra isolation transformer for 80 KVA UPS, so that dedicated neutral can be provided for down stream equipments. If the ELCB is now provided after the isolation transformer, it will not allow for intermingling of UPS and raw power neutral.

Dear All,

Thanks for reply. We have main electrcial panel connected with two input (AEC Govt Supply & DG Set suuply) and both have separate Earthing and 4 pole Breaker which cut the neutral as and when UV coil activates (no power condition). UPS is regerative power which generated three phase but no neutral. Isolation transofrmer may be the best solution as will isolate power problems as well as generates independant Neutral for downsteam critical load.

Our Electrical contractor was not recommending for bypass Neutral from input breaker (i don't know the reason). Can any one suggest any technical input in same?

Our Electrical consultant has recommended to tie separate earth in UPS output neutral line which will serve as neutral in absence of input power as cost effective solution (no need to purchase Isolation Xformer). Please let me know electrically it is safe or not?

I have noticed due to spark in any part of company (MCB protection given at all location and it will trip during the same incidence) our LAB ELCB (1or 2 out of 7 LCMSMS systems) trips randomly. We found only neutral as common in between all circuits. Please let me how is this possible and what action to be taken for same?

Thanks to all for suggestion.

I do not understand what you mean by " UPS is regerative power which generated three phase but no neutral". Does it mean, by design, UPS out put voltage is delta connected. If yes, then you cannot use this configuration for connecting single phase loads to your UPS. You will necessarily have to provide Delta / star isolation transformer to generate neutral point for UPS system.

Your Electrical contractor is right. You should not bypass the isolatable neutral ( 4th Pole of Breaker ) with a fixed neutral when EB / DG changeover facility is provided.

Your Consultant does not know what he is talking. Multiple point earthing of neutral is absolutely bad engineering.

If you provide isolation transformer, segregate the loads ( ie wiring ) and provide HPi type ( highly immunized ) ELCB after the isolation transformer, your problem will be solved. ELCB at this point will straight away indicate any screw up in wiring. If installation is correct 30mA ELCB should be sufficient.

Thanks

Our UPS (APC make Galaxy 5000) has delta output only and we use single phase loan same.

Please guide me why isolateble neutral can not be bypass in case EB/DG change over facility? What to do in case of 3 pole breaker? Please advise.

Objective of separate Earth tie with neutral is to provide neutral/groun path for return current in absence of neutral. Is that right?

Please also note, we have 4 pole ELCB (3 phase ELCB, 25A, 300mA Leakage current) in place. Previosuly Load was distributed on all three phases (R:4A, Y:1A; B:0.5A) and hence resultant neutral current was 4A. We had modified design by keeping load on single phase (load is actually singel phase but previously different module on diffrent phase) hence resultant neutral current was almost less than 1A with same ELCB (3 input butoutput connected to 1 line near by neutral in ELCB). Now the frequency of problem is very less.

My reply in Bold font.

Our UPS (APC make Galaxy 5000) has delta output only and we use single phase loan same. Your UPS selection is bad.

Please guide me why isolateble neutral can not be bypass in case EB/DG change over facility? What to do in case of 3 pole breaker? Please advise. If You have multiple neutral earth points, earth fault protection schemes will not function properly. 3 Pole Breakers will not be used in changeover schemes. Period. It is too big a topic to discuss in this forum.

Objective of separate Earth tie with neutral is to provide neutral/groun path for return current in absence of neutral. Is that right? Absolutely wrong. Please brush up on earthing schemes ( TN-S, TN-C-S, TT etc ) and their principle. We in India follow TN-S system of earthing.

Please also note, we have 4 pole ELCB (3 phase ELCB, 25A, 300mA Leakage current) in place. Previosuly Load was distributed on all three phases (R:4A, Y:1A; B:0.5A) and hence resultant neutral current was 4A. We had modified design by keeping load on single phase (load is actually singel phase but previously different module on diffrent phase) hence resultant neutral current was almost less than 1A with same ELCB (3 input butoutput connected to 1 line near by neutral in ELCB). Now the frequency of problem is very less. Just because you have distributed your single phase loads across 3 phases will not solve your problem. Do as recommended earlier or keep praying that your loads do not blow up.

That's brilliant Mr. Pattabhi! GA to you!

Thank you sir. Greetings and regards.

Dear Sir,

Thanks for all ur support.