How Many Wiring Methods Are There for Three-Phase Electric Meters?

There are various wiring methods for electric meters due to different types. These include single-phase meter wiring, three-phase meter wiring, direct wiring, and voltage transformer wiring. Among these, three-phase meter wiring is relatively complex. Let's take a look at how to wire a three-phase electric meter.

Wiring Methods for Three-Phase Electric Meters

There are two main methods for wiring 3-phase electric meters. The first method is as follows: connect the input to terminals 1, 4, and 7, and the output to terminals 2, 5, and 8. It is crucial to connect the input and output terminals correctly to avoid reversing them. The second method involves using current transformers to reduce high current to a lower level before it enters the meter. In this setup, terminals 1, 4, and 7 should be connected to the S1 terminals of three current transformers, and the S2 terminals of the current transformers should be connected together to the ground. Regardless of the wiring method, always connect the incoming wires before connecting the outgoing wires.

In general, there are two types of wiring circuits: the voltage circuit and the current circuit. The principle is that the current coil is connected in series with the load, while the voltage coil is connected in parallel with the load.

The primary visual difference between a three-phase meter and a single-phase meter is that the three-phase meter has multiple connection terminals. This meter is commonly used in circuits supplying both power and lighting.

Differences Between Single-Phase and Three-Phase Wiring

• Single-Phase Two-Wire: 1 live wire and 1 neutral wire.

• Single-Phase Three-Wire: 1 live wire, 1 neutral wire, and 1 ground wire.

• Three-Phase Four-Wire: 3 live wires and 1 neutral wire.

• Three-Phase Five-Wire: 3 live wires, 1 neutral wire, and 1 ground wire.

Why Use Current Transformers for Three-Phase Electric Meters

For currents less than 100A, current transformers are not necessary. However, for currents greater than 100A, current transformers are required to reduce the high current to a lower level before it enters the meter. This is to prevent damage to the meter and serves as protection of transformer in power system.