Design of Overvoltage Monitoring Device for 10 kV Power Grid and Contrastive Analysis of Its Measured and Simulation Waveforms

To understand the propagation process of lightning overvoltage transmitting from power lines to substations and the overvoltage's waveform characteristics and impact factors, we used an on-line monitoring device based on two-stage capacitive/resistor voltage division for 10 kV grid to measure the lightning overvoltage on a 10 kV bus, and analyzed the waveforms of back flashover lightning overvoltage. The obtained overvoltage waveforms have oscillation, and their amplitudes are less than 50 kV. We also built electromagnetic transient models of substations and transmission lines using PSCAD/EMTDC, and then discussed the influences of feeders, capacitive equipment, and arrester action on the overvoltage waveforms through simulations. The results show that the short rising edge in lightning overvoltage is caused by flashover on insulators. Capacitive equipment connected to the bus in parallel will strengthen the oscillations, while feeders can cause periodical oscillations in the overvoltage waveforms. Meanwhile, the oscillation periods decrease with the increase of feeder number. Due to the effect of arrester action, back flashover lightning overvoltage attenuates rapidly; its waveform has irregular oscillations, and its amplitude is limited to 50 kV.