Overvoltage Mechanism, Properties and Restriction Requirements of AC Half-wave Length Transmission System

There are types of acting voltages such as continuous operating voltage, temporary overvoltage and switching overvoltage in the half-wave length transmission system (HWLS) in the conventional power system, but they have different generating conditions and mechanisms, and their classification and characteristics are distinct. Through the principle analysis and the EMTP simulation, it is concluded that the crucial reason of the overvoltage inhibition in the HWLS lies mainly in the ground fault condition in the region, which presents three types of ground fault overvoltage (GFO), resonance overvoltage (RO) and power fluctuation overvoltage (PFO). The RO and PFO with the characteristics of temporary overvoltage are high in amplitude, long in duration, and wide in coverage of the whole line, which are difficult to suppress. It is an inevitable choice to install the metal zinc oxide arresters (MOA) along the line, whereas it is necessary to redefine the limit requirements for the MOA to withstand such applied voltages. Therefore, the control requirements of the overvoltage for the HWLS and the differential configuration method of the MOAs along the line are proposed. With reference to the conventional UHV projects, the overvoltage control standards for the point-to-grid UHV HWLS are proposed, including the elements of the predicted operating conditions, the overvoltage amplitude and duration, and the withstand performance of the equipment along the line. The overvoltage suppression scheme is presented that 90 groups of MOAs with rated voltage of 876kV are configured along the line and the closing resistance of UHV circuit breaker can be canceled. © 2023 Power System Technology Press. All rights reserved.