In the power measurement circuit of power plants and substations, the outdoor voltage transformer is far away from the energy meter installed on the control panel of the control room, generally 200~ Around 400 m, the entire circuit has terminal blocks, switches, fuses and wires, and there must be contact resistance, wire resistance and distribution parameters, so there is a certain loop impedance, resulting in a secondary return between the voltage transformer and the energy meter There is a voltage drop on the road. We take the “GY4300 secondary voltage drop and load tester” of Guoyi Technology as an example. When selecting, we should pay attention to the following aspects: 1. Three-phase three-wire, three-phase four-wire, single-phase full Automatic measurement; 2. After the measurement is completed, the parameters related to the load are calculated automatically, which is convenient for customers to analyze and test. 3. The secondary load test uses a clamp ammeter to sample the current without disconnecting the secondary circuit. It can be achieved without power failure. Online measurement.