Conventional Wiring Methods for Single-Phase and Three-Phase Electricity Meters

1, Direct connection method  

If the load power is within the allowable range of the electricity meter, that is, the current passing through the current coil of the electricity meter does not cause the coil to burn out, then the direct connection method can be used.
Direct connection method: A single-phase electricity meter has four wiring terminals, numbered 1, 2, 3, and 4 from left to right. There are generally two wiring methods: one is to connect the incoming lines to terminals 1 and 3, and the outgoing lines to terminals 2 and 4; the other is to connect the incoming lines to terminals 1 and 2, and the outgoing lines to terminals 3 and 4. Regardless of the wiring method, the phase line (live wire) must be connected to the current coil terminals of the electricity meter. Since some electricity meters have special wiring, the specific wiring method should refer to the wiring diagram on the terminal cover.

 2, Current transformer connection method  

When measuring the power consumption of a single-phase circuit with a large current using a single-phase electricity meter, a current transformer should be used to transform the current. The current transformer is connected to the current coil of the electricity meter.
There are two wiring methods:
① Wiring method when terminals 5 and 1 inside the single-phase electricity meter are not disconnected. Since the shorting piece inside the meter is not disconnected, the K2 terminal of the current transformer must not be grounded.
② Wiring method when the shorting piece between terminals 5 and 1 inside the single-phase electricity meter is disconnected. Since the shorting piece is disconnected, the K2 terminal of the current transformer should be grounded. At the same time, the voltage coil should be connected across the power supply terminals.

Two, Three-phase four-wire electricity meter wiring method

 1, Direct connection method  

If the load power is within the allowable range of the electricity meter, then the direct connection method can be used.

 2, Current transformer connection method  

When the electricity meter is used to measure the power consumption of a three-phase circuit with a large current, since the current flowing through the line is very large, for example, 300-500A, the direct connection method cannot be used. A current transformer should be used to transform the current, converting the large current into a small current that the electricity meter can withstand, and then perform the measurement. Generally, the secondary side current of the current transformer is 5A, such as 300/5, 100/5.
Note: The K2 terminal of the current transformer should be grounded rather than connected to the neutral wire.

Three, Electricity meter wiring precautions:
1. The outgoing lines of low-voltage energy meters should use insulated copper core wires with a rated voltage of 500V. The current-carrying capacity of the wires should match the load, and the wire cross-section should be no less than 2.5 square millimeters.
2. The laying of plastic-insulated wires should use wire codes, plastic trough plates, or plastic pipes for installation.
3. The phase sequence of the outgoing lines of three-phase three-wire and three-phase four-wire energy meters should be marked with yellow, green, and red wires or painted with yellow, green, and red colors on the wires to distinguish the phases. If the neutral wire is black, no color should be applied.
4. When connecting the primary lines of low-voltage current transformers, attention should be paid to the marked ratio turns and joints, and the outgoing lines should be crimped with terminal lugs.
5. The wiring of the electricity meter should be based on the accompanying diagram and the wiring diagram on the back of the meter cover, especially for new meters. For old meters, extra caution is needed, as the wiring diagram on the back of the meter cover may not be accurate, since you do not know whether the cover is the original one for the meter or if it has been accidentally replaced. To be safe, use a multimeter to measure and identify the wiring terminals for the current coil and voltage coil. Generally, the resistance of the voltage coil is 700-800 ohms, and the resistance of the current coil is 0 ohms. Failing to do this step may lead to a short-circuit fault.
6. When connecting a three-phase four-wire electricity meter with a current transformer, the three voltage coil connection pieces on the electricity meter should be removed. If not removed, it will cause a short circuit.
7. The polarity of the current transformer must be correctly connected. When the main circuit wire passes from the P1 terminal to the P2 terminal, the K1 of the transformer secondary side should be connected to terminals 1, 4, and 7 of the electricity meter, and K2 should be connected to terminals 3, 6, and 9. If K1 and K2 are all reversed, the electricity meter will either not rotate (for electricity meters with a reverse-stop device) or rotate in reverse (for electricity meters without a reverse-stop device). If only one or two are reversed, the electricity meter will under-register the power consumption.

Huabang Electric Power Technology Co., Ltd. specializes in producing rail-mounted energy meters, wall-mounted energy meters, and digital multifunctional power meters. The wiring method for rail-mounted energy meters is generally bottom-in and top-out. Transparent housings are generally bottom-in and bottom-out. Special requirements can be met with top-in and bottom-out configurations. The wiring method for wall-mounted energy meters follows the conventional method. Digital multifunctional power meters have terminals at the back and are wired according to the terminal diagram, with the meter having a wiring diagram.