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For the past 6 months there has been increase in my electricity bill. The reason is that the maximum demand is higher (6kW) than the sanctioned maximum demand (3kW.)

We have a 3HP 3 phase borewell motor. We have had the same motor for more than 5 years now and for the past 6 months it seems to be drawing 6.2kW power instead of under 3kW. This borewell motor is also the only load connected to the energy meter.

Nothing has changed in the past 6 months except some re-wiring at the energy meter (this is what I am suspecting.)

The people at electricity board are asking me to increase the sanctioned limit.

The current drawn is ~10 amperes and RYB to neutral voltage is ~230V.

Please help me how to troubleshoot this issue. Nobody here seems to understand that the issue is the motor drawing 6kW while it should be drawing <3kW.

Could bad wiring at energy meter cause this, or a faulty energy meter? Could the motor itself be faulty? It seems to be doing its job of pumping the water perfectly, though. The energy meter showing max demand connections. Electrician used insulation tape to tag RYB The motor started box

In the second picture, I see there's an additional red wire going into the fuse with Blue phase. I'm not sure where it is coming from.

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    \$\begingroup\$ Like I mentioned, there's no other load connected to the energy meter. Also I checked the energy meter go from 0 to 6kW when I turned on the borewell motor. \$\endgroup\$
    – Arun Gowda
    Feb 24 at 12:18
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    \$\begingroup\$ Maybe when they changed your "wiring" they started monitoring apparent power, rather than real power, although a jump of 100% would imply a terrible power factor to begin with. Perhaps, during the "rewiring" they accidentally disabled a bunch of PFC stuff? \$\endgroup\$ Feb 24 at 12:57
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    \$\begingroup\$ "does [the water level] matter?" Yes. The power required is proportional to the height the water is being lifted through (for a constant flow rate). Assuming the discharge height is fixed then a falling water level in the well (e.g. due to dry weather) will require more power to pump. The distance of the pump below the water level is irrelevant (because the pressure on the inlet side compensates for the back pressure on the outlet side). \$\endgroup\$
    – Graham Nye
    Feb 24 at 12:58
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    \$\begingroup\$ Last time.... you said this: The pump is in the same position from earth surface. say 250 meters. Now does it matter if the water level is 150 meters below earth's surface (100m above pump) or 200 meters(50m above pump) from earth surface? <-- yes, it totally matters. \$\endgroup\$
    – Andy aka
    Feb 24 at 13:12
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    \$\begingroup\$ "I'm looking for a starting point." Can you check the water level in the well yourself? The next step would be to get a professional electrician (preferably one with borehole pump experience) to check the surface wiring and confirm the real and apparent motor consumption. (It is possible for energy meters to read incorrectly and motors shouldn't be consuming twice their rating.) The final step (because it's presumably quite involved) would be to haul the motor/pump up and have them serviced. \$\endgroup\$
    – Graham Nye
    Feb 24 at 13:29

1 Answer 1

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The key question seems to be whether the energy meter is working correctly or not.

Have you measured the current to the pump using an independent meter (such as a clamp on ammeter), or are you reading 10A from the display of the same meter which is giving a suspect power reading?

If the independent current reading is ~10A, then the load has almost certainly changed (and there are lots of good comments on the question as to possible causes).

If the independent reading is nearer 5A, the meter setup is wrong.

If the latter, I'd look at the meter configuration to check the CT ratio (if an indirect meter), and also check how many times the supply leads are passing through the CT window. I've seen inexperienced engineers pass the cable through twice, unintentionally doubling the metered current.

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