Arrester Protection of Lower Voltage Circuits on Multi-Voltage Towers: Issues Opportunities

摘要

Distribution system engineers sometimes take advantage of existing transmission right-of-way to route their medium-voltage (MV) circuits when standards show there is adequate vertical clearance to high-voltage (HV) transmission circuits above. Often, the lightning performance of the HV circuit improves, while the tripout rate of the MV circuit is disappointing. Line surge arresters offer an opportunity to retain the benefits of improved electromagnetic coupling of lightning to the HV circuit above, while mitigating induced and backflashover overvoltages on the MV circuit below. A tutorial approach, using Excel surge impedance matrix calculations, supports the analysis. With appropriate selection, arresters on the lower circuit can also mitigate cross-system contact faults.