Three-Phase Four-Wire Meter Wiring Diagram (1)
There are many wiring forms of electricity meters, including single-phase electricity meter connection methods, and three-phase electricity meter connection methods. Among them, the three-phase meter mainly measures the "sum of power consumption" of the three live wires with a voltage of 380V. The three-phase meter is divided into a three-phase three-wire meter and a three-phase four-wire meter. Next, let's learn how to connect the three-phase four-wire meter and the connection method of the three-phase four-wire meter transformer.
Three-phase four-wire meter wiring diagram
There are many wiring forms of electricity meters, but in general, there are only two kinds of loops, voltage loop and current loop. The general principle of meter wiring is: the current coil is connected in series with the load or connected to the secondary side of the current transformer, and the voltage coil is connected in parallel with the load or connected to the secondary side of the voltage transformer.
The three-phase four-wire active meter consists of three driving components, called a three-element meter. The biggest difference in appearance from single-phase and three-phase three-wire meters is that there are 11 terminals in total. This meter is often used in power supply circuits where power and lighting are mixed. The wiring diagram is as follows:
The picture above (left) shows the direct connection of the three-phase four-wire active meter. The live wires U, V, and W are connected to terminals 1, 4, and 7 respectively, terminals 3, 6, and 9 are connected to the load, the neutral wire is connected to terminal 10, and the terminal 11 is connected to the other end of the load.
The above picture (right) shows that the three-phase four-wire active meter is connected through the current transformer. The live wires U, V, and W are respectively connected to the head end L1 of the primary side of the current transformer, and the end L2 of the primary side is connected to the load. Terminals 1, 4 and 7 of the watt-hour meter are respectively connected to the head end K1 of the secondary side of the current transformer, and terminals 3, 6 and 9 are respectively connected to the end K2 of the secondary side. Terminals 2, 5, and 8 of the electric meter are respectively connected to the L1 terminal of the primary side of the current transformer, and the connecting piece should be removed. To ensure safety, the terminal K2 of the secondary side of the current transformer should be grounded separately. The picture on the right is a simulation demonstration of the wiring diagram. Pay attention to the wiring between the current transformer and the meter.
1. Wiring method for three-phase power transmission
The three-phase four-wire system means that there are A, B, C, and N, among which, the N line is the neutral line, also called the zero line. The N line is designed to obtain the 220V line-to-line voltage from the 380V line-to-line voltage. In some cases, it can also be used for zero-sequence current detection to monitor the balance of the three-phase power supply. The A wire is yellow, the B wire is blue, the C wire is red, the N wire is brown, and the PE wire is yellow-green.
2. What is the difference between single-phase three-wire, three-phase four-wire, and three-phase five-wire?
Single-phase double-wire----------1 live wire and 1 neutral wire
Single-phase three-wire----------1 live wire 1 neutral wire + 1 ground wire
Three-phase four-wire----------3 phase wires and 1 neutral wire
Three-phase five-wire----------3 phase wires 1 neutral wire + 1 ground wire
The single-phase electricity meter mainly measures the "power consumption" of a single live wire with a voltage of 220V, which is mainly used for urban residents' electricity consumption and lighting electricity consumption.
The three-phase electric meter mainly measures the "sum of power consumption" of the three live wires with a voltage of 380V. It is mainly used in the electric energy measurement at the gateway, industrial, mining and commercial enterprises and other large power consumption units, generally in high-voltage lines. It has several ways of 3-wire, 4-wire and 5-wire according to the occasion:
Three wires----------3 live wires (without neutral wire N and ground wire PE)
Four wires----------3 live wires + 1 neutral wire N (TN-C system)
Five wires----------3 live wires + 1 neutral wire N+1 ground wire PE (TN-S system)
3. Why should add a transformer to a three-phase meter?
Generally, less than 100A does not need to add a transformer, and more than 100A after adding a transformer is equivalent to turning a large current into a small current before entering the meter, which will not burn the meter. After adding the transformer, when reading the meter number, it should be multiplied by the corresponding multiple of the transformer.
