How to include a three-phase meter of active electric energy in a high-voltage network

When the electricity meter is connected to the high voltage network, two current transformers and two voltage transformers are selected.

The current windings of the measuring instrument are connected to the secondary circuits of the measuring current transformers. The voltage coils are connected to the secondary voltage of the voltage measuring transformer. When connecting these windings, the internal jumpers between the sources of the current voltage coils are removed and the voltage coils are turned on independently of the current circuit (Fig. 1).

Scheme for connecting a two-element active energy meter to a high-voltage network

Rice. 1 Diagram for connecting a two-element active energy meter to a high-voltage network

The value of consumed electrical energy with this inclusion can be determined by the expression W = WcchNS Kni x Knu,

where Kni — transformation efficiency of current transformers, Knu — transformation coefficient of voltage transformers.

At high primary voltages and high currents, the transformation ratios can be large. In this case, when determining the consumed electrical energy, the counter readings are multiplied by rather large numbers.

So, for example, for U1n=10 kV and I1 = 100 A, you need to take a voltage transformer TN-10000/100 with a transformation factor of 100 and a current transformer TK-100/5 s Yes with a transformation factor — 20. Therefore, in order to determine the consumed electricity, the meter readings must be multiplied by 2000, that is, the cost of one meter section becomes very significant. The switching scheme of the meter is shown in Figure 2.

Connection diagram of a three-element meter with a four-wire network

Rice. 2. Connection diagram of a three-element meter with a four-wire network

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