Earth Leakage Current Too High!

Marks and Spencers? I am too lazy to google that. What type of equipment are you primarily powering?

If you really want to nail this down, you can go panel by panel. 10A may be fine in your specific case.

everything from lights, sockets, pc equipment,fire alarm .intruder alarms, extract fans fan coil units cctv supplies security panels, you name it !! how does a person reduce earth leakage when location of problem is found? thanks

First off, you need to identify if there actually is a problem. Go panel by panel and determine the largest "offender" for leakage. Then go circuit by circuit.

You may find that the equipment is operating within specs.

We had a similar "problem" at a power plant I worked for. Your method is EXACTLY what we did and funny enough, what we found was precisely as you say... well within normal parameters!

GA!

increase resistance :D

please post a photograph of the 10 amp "reading" . . .

How can you have 10 A leakage! A 30 mA leakage will already cause the ELCB to trip. An d if you operate your building with the ELCB deactivated or bypassed , it is dangerous!

Something is amiss here!

10A total leakage. This is sum leakage current. This will not trip the breakers which are upstream of the "total" leakage.

Just a thought on this.

10A/30mA= 334 upstream earth leakage breakers. This seems unlikely!

Unlikely...but not impossible from my original perspective. I did not know that this was a department store. That changes my perspective.

I measure nearly 8 amps at my ground field lead, but I have thousands of breakers to occupy my time, and a unique environment.

Megger the connected appliances and wiring separately to identify the culprit

Carry out circuit by circuit megger testing. For procedure refer to manufacturer's guide or Google. This will identify the offending circuit. A 10amps earth leakage current is fairly high and should not be left unattended.

1. find Yellow Pages

2. Look up "Electrical Engineers"

3. Interview several firms

4. Employ a qualified electrical engineering ot electrcian

5. Put a competent trained professional on the job

6. Take her/his advice

7. Pay them

Problem solved

If there is a large number of PC's, computer based equipment, inverters (fans, refrigeration) I am not surprised, all adds up. Also older cabling.

EL is normally on final circuits now a days not on main supplies.

10amps is a little high but it does depend on how much of the above stuff you have.

How is this 10 amps measured? CTs in each phase are unlikely to be better than +/-1% error. So at 1000 amp rating +/- 10 amp error around 3 CTs (one in each phase) is probable. So you cannot expect accuracy from residual current of 3 CTs. 10 km of PVC cable could have 4 microfarad capacity to earth - but 10amps @ 240V 50 Hz sine means 120 microfarads. Lots of equipment has RFI filter capacitors of about 0.002 microfarad - 1000 items for 2 microfarad. Power factor compensation capacitors in luminaires will have capacitance to their case (earth). But these causes do not seem likely to be enough. Are you talking core-balance CTs?? Have you assessed the measurement error, to be sure this is not a "red herring"?? If current is genuine, since when has it occurred? If unbalance is real, I would try a clamp-on ammeter on the earth returns of sub-circuits (or compare reading with clamp around live + neutral with live alone), or isolating sub-circuits while measuring "Earth leakage". Perhaps, somewhere there is a an equipment connected live-earth, instead of live-neutral.

After all that...a reversed (N/G) circuit would definitely cause this. That's why I suggested going panel by panel.

A sensible person who has a polarity checker ($5.00 at HD or Lowes) could find that problem in about half-an-hour.

10 AMPS? You are talking about a Marks & Spencers store, where they sell mostly clothing and household goods, right? Not some weird M&S where they demo 50 different 3 phase drills, mills and lathes at the same time, right?

10A for earth leakage isn't going to save anyone at all - even a large house or hotel will rarely go beyond 40mA earth leakage on the trip, because the whole point is for it to, you know, trip!

The idea is that when someone gets the start of an electric shock, the trip cuts the power before a lethal current can pass - hopefully. 10A is far, far beyond anything you could ever get for earth leakage unless you used a good screwdriver driven into the ground, then shorted it down with some decent thickness copper cable.

Go find someone expert in this stuff, employ them, and use their insurance if anything ever goes wrong.

Insurance is a good idea...with culpability. Seeing as how the OP has some basis for stating 10A leakage I "assume" he used some type of "test equipment" to get the data and therefore "must" be some kind of "technician".

That's a lot of assumption on my part.

10A for total leakage for a facility is not too farfetched. I don't know the type of facility he is working in though.

Marks & Spencer? Think of a fairly posh chain store, higher end and smaller stores. https://www.marksandspencer.com/

Sure they might have a few rows of fridges and perhaps a small freezer section (if they have a food section), air-con, the lights and (unlikely in the UK as we tend to use gas) the heating, but I doubt they would be using more than a small sub-station, and likely just be running off a 3 phase supply if it is a smaller store.

No way 10A of earth leakage should be happening.

Guys, Appreciate everyones input so thanks. May i add this marks and spencers is currently the biggest in Europe. Its consisting of everything from AHU Panels, 2 Generators,Static Invertor Panels for Emergency back up, BMS Modules CONSISTING of invertors for large extract fans and a whole lot more . Unfortunately ive never had this sort of an issue before as any other project ive worked on was efficient. I myself havent witnessed the engineer who took these readings performing the test. Im anxious to "easy fix" this dilemma as im swamped with other issues. Once again thanks to all even the sarcastic people amongst ye.

So you have an engineer who took the readings and is now telling you that you have a problem. Is that it?

If it was a power quality survey that you paid for and he/she only checked the service entrance then you got ripped off.

trust me mate its not my money involved. wise up

The only "easy-fix" is that this "earth leakage" is a misunderstanding of a measurement. My guess is that your 3 phase incomer has a CT in each phase plus neutral and the summation current of the four goes through an "earth fault" relay. Maybe someone has read the current in that relay on the assumption it is an accurate calculation of a real earth current?

Your description suggests a 3 phase & neutral incomer of hundreds to 1000 amp rating. Even with that, an earth leakage of 10 amps is not believable.

I would take the line, with whoever is pressing you about this, that such an earth leakage is not believable and that I would not worry about or take any time over it unless it is explained exactly where, when, how and by whom it was measured and why it represents an "earth leakage" (in writing, with the relevant circuits attached).

Dear All,

In our company I measured the earth leakage through clamp meter, it is showing 20Amps, the load is 800Amps DC drive running DC motor.Is it acceptable or it needs to be arrested?.The main incoming is 3Phase + earth, No neutral connection.

No neutral connection...anywhere?

Somebody may need to explain the differences between your EGC and GEC.

Separately derived neutral anyone?

Neutral is there, But it is not connected to the Main drive panel, as DC drive is connected with 3 phase, earth and other loads are 415V, and control voltage is 24V DC, No neutral is used in the panel.

One caution about clamp meters. They are not immune to fields "outside the ring".

What do you read with the clamp closed, close to the high current cable, but not around a cable??

67model

There is a reference to neutral starting at your service, or should be. Whether it is the facility's incoming power or a separately derived service from an internal isolation, distribution, or whatever transformer...there has to be a GEC/neutral bond in that stream (at the source). This would be a major determinant in excessive current being measured in your earthing connections.

Where is the control voltage derived from? Is it a separate source from, maybe, a different distribution center (low-voltage bus)? If the 24V is derived from a single phase internal power supply, then there should be a neutral connection there.

If you have a question as to outside influence on clamp meters...that is possible, but not likely at that level. The current seems excessive for outside influence unless yard work is involved. You can bring your system down, power off and tag it..whatever. Connect your test equipment for in-line current measurement and run it back up (preferably with monitoring/logging). This will give you a more accurate reading and a better picture of possibilities.

yes, you are right, The earth cables and neutral cables are bonded together in the Main panel and current is measured on the EGC.

Is it normal to have this much current on the EGC cable where neutral is not utilized in the load and only earth cable connected?

Thanks for your information.

*Normal* for some...but not what should be acceptable without further investigation.

You need to identify the source of the current down to the device(s). If you have an imbalance between the phases and a grounded conductor where it isn't supposed to be, the system will try to balance itself.

The neutral in your system is probably used on one of the shared phases on the down side of your supply transformer, yes? The neutral and ground are bonded at same, yes? That makes the ground appear as a neutral in some instances. The phase imbalance will find a way.

Do you have shared neutrals? Are your neutrals properly sized?

Reference reply #29. I just got my clamp meter and tried it with an 8 amp current in a ring of cable. It reads 8amps with the clamp around the cable, but with the clamp closed (not around the cable) and touching the cable the reading varies from 0.05 to 0.3 amp - depending on position around the clamp. The 0.3 amp is on the curved prong of the clamp, while minimum is on the straight prong of the clamp [the clamp springs together where straight and curved prongs meet]. So, scaling the values, if you put the clamp around an earth core which is close to an 800 amp load conductor, you may read 30 amps without any current in the earth. You do not know you have a problem until you know your measurement is dependable. If it is dependable, the suggestion to measure the ground conductor current on sub-circuits is the way to close-in on the problem. 67model

Flux density results from a Hall effect clamp meter is logarithmic, not linear...

The plane of incidence and the direction of the current flow must also be considered. Whether the "curved" or "straight" portion of a particular clamp on meter is used for measurement with any conductor external to the clamp (open or closed) is not part of the schema for any clamp meter.

Inductive effects for single strand testing (currents higher than 1 amp, generally) are not considered. In highly inductive environments (yards) conductors must be kept as straight as possible to avoid the incidental effects and yield accurate readings.

If you are considering an EGC as a GEC and are using earth as a return leg, you have other issues to contend with.