Overvoltage Study Of Cable Metal Sheaths In 500kV Pumped Storage Power Plants

The cables in a pumped storage power plant can appear high impulse voltages in the cable sheath during lightning,VFTO,and closing no-load line conditions,so attention needs to be paid to the overvoltage in the cable sheath to ensure equipment and personnel safety.In this paper,the electromagnetic transient calculation program ATP-EMTP is used as the calculation tool,and a pumped storage power plant project is used as the simulation object to simulate the lightning overvoltage,the very-fast transient overvoltage caused by the breaking operation of the disconnect switch and the closing of the empty line in the pumped storage power plant.By analyzing the simulation results,the distribution rules of the induced overvoltage in the metal layer of the cable inlet section of the station are discussed and the corresponding overvoltage suppression scheme is proposed,and the effectiveness of the suppression scheme is verified.This is an important reference for similar problems in other 500kV pumped storage power stations.The results show that:1.under lightning intrusion and VFTO,the inductive overvoltage of the incoming cable section endangers the safety of cable insulation and requires effective inductive overvoltage suppression measures,while the inductive overvoltage of the combined airline operation in the cable sheath does not endanger the cable insulation.2.for the suppression of the inductive overvoltage of the cable metal layer,the use of the cable metal sheath cross interconnection and the Y0 wiring of the cable sheath protector has the best effect.The best;one end of the cable sheath is directly grounded,the other end is grounded by the sheath protector is the second;the effect of adding a return line is the weakest.3.For short distance cables,due to the cumbersome operation of cross interconnection,it is recommended to use the scheme of direct grounding at one end of the cable sheath and grounding at the other end via the sheath protector to suppress the cable sheath induced overvoltage.For longer distance cables,if the cross interconnection of metal sheath is feasible,it is recommended to use the suppression scheme of direct grounding at one end of the cable sheath and grounding at the other end through the sheath protector.