Leakage Current

What are the loads being powered? Are there any EMI filters wired into these that are active when the CBs are closed?

If you have EMI filters, it's possible a capacitor is leaking, and drawing more then the reactive power it normally would.

GA. Even the GFI contain monitoring electronics that consume tiny amounts. For OP to have measurable results, most likely it's a transformer, as you say. There are many " vampire " circuits these days, the only way to track them down is load shedding. Any equipment " off " but on standby could have tiny drains. GA.

Good answer, and a classroom classic as well, a bump on the head followed by an enlightening lesson.

Is there no one on your staff who has even a rudimentary understanding of electricity?

Just asking.

They surely have, but they all are too dazed by the miriads of new devices which turn a light ON, to indicate that the device is OFF.

Open the breaker box, get a clamp on ammeter, and check the current for each breaker.

If you have any buried (underground) wiring, it is possible there is a cut in the insulation.The cut does not have to be very large,just a minor nick will do it.The surrounding ground will absorb the heat.This frequently occurs when wires are not buried deep enough,or if there is very rough back fill over the wire,such as crushed brick,etc.

Isolate the circuit as previously described to determine the particular one of interest.

You have electric clocks, door bell, clock radio, cable box, and other electronic appliances like TV, cellphone chargers, etc. that have built-in timers that are always ON and consuming power even if their power switches are on OFF positon!

Even supplying power on long cables, uses a small amount of power, even though nothing is switched on at the end of them.

The longer the cables, the greater the effects....

Its best to activate circuits with long cables only when actually needed....but also remember, the effects are "cumulative" and a dozen short cable runs will add up to the same power loss as a longer single cable run.....roughly speaking.

How so?Please explain,aside from capacitive charging,which is very negligible,and not a constant drain.I have seen capacitive effects on long communication lines, but never on normal neighborhood occupancy power.

Has the OP stated ".....normal neighborhood occupancy power."

I never saw it. Please be so kind as to mention which post that was?

My impression was that it was industrial, not domestic....

The losses from power station lines can be 5-6%......the national average is in that range, partly resistive of course.....remember. the lower the voltage, the higher the losses....

We are working here with incomplete infos.....remember G.I.G.O?

Now are you surprised? I won't be, either way.....

Where did he mention "power stations" or long distance power transmission,or a national or regional problem?

He mentioned MCB's which are normally indicative of low voltage conditions and a meter,not meters,(Which would consist of 3 meters in industrial applications:

1ea KVa meter, 1ea Kvar meter, And 1ea Demand meter.)

Would the OP please clarify which type system he is referring too, to avoid ambiguity in answers?

I note he says "we" and not "I", which makes me think of a firm rather than a family.....not that its truly indicative either way.....just a thought!!

I am not going to play this game of semantics with you.I will wait for the OP to clarify his question.....or not.

Why not? Its the only best game in Town!!

Leakage current is the current that flows through out the protective ground conductor through ground. There are types of leakage current, these are AC leakage, DC leakage etc. To isolate the leakage current, the measurement of leakage current is one of the most important tests in electrical current, to isolate the leakage current by supplying voltage current normally, apply the DUT power source to isolate the leakage current.