变压器空载时三相三线电能表出现负电流的分析

Negative current analysis of in three-phase three-wire watt-hour meter occurring negative current under transformer being no-load

针对计量人员在变压器空载时检查电能表发现电能表出现负电流的情况,分析了三相三线电能表的测量原理,给出了变压器空载功率因数的计算式,对多种型号变压器空载时一次侧的功率因数进行测算。用数据证明了变压器空载时一次侧的功率因数极低,并通过实例计算证明了功率因数低会导致电能表出现一相负电流。该分析为计量人员在开展电能表检查时提供理论依据,有一定的参考价值。

According to the real situation of the measurement of negative current in watt-hour meter when the measuring principle of three-phase three-wire watt-hour meter is analyzed under the transformer being no-load. The calculation formula of no-load power factor of transformer is given, and the power factors of various type transformers are calculated. It is proved that the power factor of the primary side is extremely low when transformer is no-load, and the calculation of an example proves that the low power factor will cause a phase negative current in the watt-hour meter. This analysis provides a theoretical guide for the metrology personnel to carry out the watt-hour meter check, and has certain reference value.