[Explained] Phantom Loading in Energy Meter

The term "Phantom" means someone who appears to be present but really there is no one. In other words Phantom means ghosts.
So in the case of an energy meter, phantom load means some load is connected to the energy meter but actually there is no load. Phantom Loading is used for testing of energy meters.

What is Phantom Loading in Energy Meter?

To perform accurate testing we need to connect a rated load to the energy meter.
During the testing of an energy meter, a virtual load is connected to the energy meter which is called a phantom load.

Let's go to know how the phantom load is provided to the energy meter during testing.

An Energy Meter has two coils one is the Pressure Coil(P.C) or voltage coil and another one is the current coil(C.C). In the phantom loading technique, those two coils are excited separately.

The pressure coil(P.C) is excited by a voltage equal to the load voltage or rater voltage of that coil. The pressure coil has very high resistance, so there is no problem if the full rated voltage is given.

Current Coil(C.C) has very low resistance, so it is excited by very low voltage for which rated current will flow through the coil.

Now You may understand, there is no load connected to the energy meter but voltages are applied to those coils in such a way that it experiences the load is connected.

Read Also: Working and connection diagram of Single Phasing Preventer

Why Phantom Loading is used instead of Direct Loading?

Now, you may think that is why we did not use a real load.

It is very difficult to find the load that can take the exact rated current and voltage.
Another problem is that if we used a real load it would waste a huge power.

Let's go to understand with an example.

Suppose a DC energy meter has a rating of 230V and 10A. The resistance of the pressure coil and the current coil is 5290 ohm and 0.1 Ohm respectively.

Now if we connect a real load that takes 10A current at 230V.

The power consumption in pressure coil will be {(230)^2}/5290 = 10 watt
The power consumption in the current coil will be 230*9 = 2070 watt
So the total power consumption is 10+2070 = 2080 watts.

Now if we used the phantom loading technique,

The power consumption in pressure coil will be {(230)^2}/5290 = 10 watt
The resistance of the current coil is 0.1 Ohm. So, if we apply just 1V across the current coil, 10A current will flow through it and the power consumption will be 1*10 = 10 watts.
So the total power consumption is 10+10 = 20 watts.

Now you may understand, that if we use real load instead of phantom loading for testing, (2080-20) = 2060 watt power will be wasted.

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