How to Choose Single-Phase Energy Meter?
How to choose a single-phase watt-hour meter is more or less accessible to today's families. The use of single-phase watt-hour meters is mainly used in household electricity meters. A typical household watt-hour meter is initially installed by the power department or by the developer. However, in some places, you will need to install a single-phase watt-hour meter by yourself for meter measurement. Therefore, I will introduce to you how to choose a single-phase watt-hour meter so that it can be used when needed later.
How to choose a meter?
1. Determination of range
Why do you need to determine the range of a single-phase watt-hour meter in the first place? For later safe use, it is necessary to ensure that the current of the watt-hour meter under test does not exceed the maximum measured value. The configuration of the single-phase watt-hour meter should be determined according to the debt power. The single-phase electrical current is 4.5A per kilowatt, then the meter range should be configured to be 1.2-1.5 times the current. If the total power of a household appliance is 4KW and the current is 18A, a 5 (20) A single-phase watt-hour meter can be selected.
2. Determination of capacity
The general voltage specification of a single-phase watt-hour meter is 220V, and the current specification is 1.5(6)A, 5(20)A, 5(60)A, 15(60)A, 20(80)A, etc. The choice of the current specification mainly depends on the user's load. Generally, the upper limit of the load current cannot exceed the rated current of the watt-hour meter. The lower limit is not lower than the load current specified within the allowable error range of the watt-hour meter. For example, the total power consumption of the user is about 10KW, the voltage is 220V, and the current is 10000÷220≈46A. That is to say, divide the electric power by 220, and the current value is about 46A. Considering the need to reserve a certain margin, the current specifications of 5 (60) and 15 (60) A can be selected. You can also choose a smaller current specification, and then connect the current transformer.
3. Selection of current transformers
The current transformer is selected for those users with large current, which can convert the primary current with a large value into a secondary current with a small value through a certain amount, which is used for protection and measurement purposes. For example, a 100/5 current transformer can convert a 100A social current into a 5A current. The selection of the specifications of the current transformer is mainly for low-voltage users. Low-voltage users may not be able to estimate the power consumption because the power load may change at will, so the transformer specification is not easy to choose. It is usually calculated based on the known power consumption. For example, for a user whose electrical power is 100KW, the voltage is 220V, and the current is approximately equal to 100000÷220≈455A. It is also necessary to consider a certain margin, and a current transformer of 500A needs to be selected. The secondary output current of the transformer is generally 5A. Therefore, a 500 to 5 transformer is selected. Regarding the accuracy of the current transformer, it needs to be at least at the same level as the meter.
