How To Wire Three Phase Meters?

Three phase meters have a direct connection, transformer connection, current, voltage transformer connection, and other wiring methods.

1. Three phase meters’ direct access type

The direct connection type is also called straight-through connection, which can be directly connected within the range allowed by the load function meter, that is, the current specification of the three phase meter can meet the needs of users, and this method can be used.

1) 1 and 2 are called U, which are the live wires of the three-phase four-wire ammeter, connected to the incoming terminal of phase A, and connected to the outgoing terminal of phase A;

(2) 4 and 5 are called V, which are the live wires of the three-phase four-wire ammeter, connected to the B-phase incoming terminal, and 6 connected to the B-phase outgoing terminal;

(3) 7 and 8 are called W, which is the live wires of the three-phase four-wire ammeter, connected to the C-phase incoming terminal, and 9 connected to the C-phase outgoing terminal;

(4) A, B, and C three-phase outlets are connected to the load;

(5) 10 is connected to the neutral line, and connected to the following wiring.

2. The three phase meters are connected through the transformer

When the 3 phase meter measures the power consumption of a single-phase circuit with a large current because the current flowing through the line is very large, such as 300-500A, it is impossible to use the direct connection method and a current transformer should be used for current conversion. The current is replaced by a small current, that is, the current that the three phase energy meter can withstand, and then measured.

(1) 1, 4, and 7 must be connected to the S1 terminal on the secondary side of the current transformer, which is the incoming terminal of the current;

(2) 3, 6, and 9 must be connected to the S2 terminal on the secondary side of the current transformer, which is the outlet terminal of the current;

(3) 2, 5, and 8 are respectively connected to A, B, and C three-phase power supplies;

(4) 10 is connected to the neutral line. Generally, for the sake of safety, the S2 terminal of the current transformer must be connected and then grounded.

Note: The current measurement sampling of each current transformer must be kept in phase with its voltage sampling, that is, 1, 2, 3 are a group; 4, 5, 6 are a group; 7, 8, 9 are a group.

3. Three phase meters are connected through the current and voltage transformers

When the 3 phase electric meter measures a large current and high voltage, because the voltage and current are very large, it cannot be directly connected. Voltage and current transformers should be used for voltage and current conversion, and high voltage and high current should be replaced with small voltage and low current. That is, the voltage and current that the three phase energy meter can withstand, and then measure.

(1) 1, 4, and 7 must be connected to the S1 terminal on the secondary side of the current transformer, which is the incoming terminal of the current;

(2) 3, 6, and 9 must be connected to the S2 terminal on the secondary side of the current transformer, which is the outlet terminal of the current;

(3) 2, 5, and 8 are respectively connected to the voltage transformer;

(4) 10 should be connected to the neutral line and grounded together with the voltage transformer;

4. Precautions for three phase meter wiring

In actual work, the 3 phase electric meter customers that power supply employees come into contact with are often low-voltage power supplies, and most of them use mechanical three-phase four-wire watt-hour meters.

After installing the three phase electric energy meter, it is also possible to check whether the electric energy meter is running forward and whether the speed is normal, but it is often neglected to test whether the phase sequence of the three-phase voltage is correct.

If a reactive energy meter is installed, you can judge whether the phase sequence is correct or not by observing whether the reactive energy meter is rotating forward or not. However, only the active energy meter is installed, and the correct phase sequence cannot be judged by the positive rotation of the 3 phase energy meter.

Because when the reverse phase sequence is connected, the three-phase active energy meter can still rotate forward. Therefore, in order to avoid creep and additional errors caused by the reverse phase sequence to the three-phase electric energy meter, after installing the three-phase electric energy meter, it is necessary to conduct a power-on inspection test and use the phase sequence meter to retest whether the three-phase voltage phase sequence is correct.

If it is a reverse phase sequence, the incoming and outgoing lines of the two phases can be exchanged arbitrarily to change to a positive phase sequence. In the phase sequence of the electric energy meter with transformer, it should be noted that the voltage and current of the same phase must be exchanged at the same time to be correct.