How to choose a single-phase smart meter?
The use of single-phase smart meters is mainly used in household electricity meters. Usually household meters are installed by the power department or developer, but there are places where a single-phase meter must be installed to measure residential or rental meters. So here is how to choose a single-phase smart meter so that it can be used in the future.
1. Range confirmation
Why must the single-phase smart meter range be confirmed first? For future safe use, it must be ensured that the measured current of the meter does not exceed the measured value. The configuration of a single-phase smart meter must be based on the power of the debt. The current of single-phase appliances is 4.5A per KW, so the meter range should be configured to be 1.2-1.5 times the current. If the total power of the household appliance is 4KW and the current is 18A, a 5(20)A single-phase electric energy meter can be used.
2. Capacity confirmation
The typical voltage specification of a single-phase smart 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 specification at this stage is mainly based on the user's load. Usually, the upper limit of the load current cannot exceed the rated current of the electric energy meter, and the lower limit is not less than the load current specified within the allowable error range of the electric energy 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, the power is divided by 220, which means that a certain margin is fully considered, and the current value is about 46A. You can choose the current specification of 5(60) 15(60)A. You can also choose a smaller current size and connect a current transformer.
3. Selection of current transformers Current transformers are specially designed for high current users. It is capable of converting large currents with larger values to secondary currents with smaller values for safeguard and measurement purposes. For example, a 100/5 current transformer can convert 100A to 5A of current. The selection of current transformer specifications is mainly for low-voltage users. Low-voltage users may not be able to estimate power consumption due to random load variations. Therefore, the transformer specifications are not fixed. It is usually calculated based on known power. For example, for a user with an electric power of 100KW, the voltage is 220V, the current is equal to 100000÷220≈455A, and a certain margin needs to be considered. A 500A current transformer must be selected. The secondary output current of the transformer is usually 5A, so we choose a 500 to 5 transformer. The accuracy of the current transformer must be at least the same as the meter.
