Discussion on stage difference coordination of DC system in qingyuan pumped storage power station

Abstract

In the power system of pumped storage power station, DC power supply, as the control power supply, relay protection and device power supply and the power supply of some important motors, is an important guarantee for the safe and stable operation of the whole unit. With the continuous advancement of smart grid technology, the protection and control loads within power stations are increasing, which further enhances the demand for automated and intelligent equipment. In DC systems, higher standards are set for overload protection and short-circuit protection of protective devices, requiring these devices to neither false operate nor refuse to operate, especially to avoid over-stepping actions. Once such a situation occurs, it may cause damage to power components, leading to an expansion of the accident scope, and even potentially triggering large-scale blackouts. The State Grid Corporation has initiated a series of research efforts regarding the reliability of DC power supplies, with a key task being the optimization of short-circuit level coordination for air switches in DC systems. The differential coordination of DC air switch is one of the main indicators to judge the reasonable configuration and safe operation of DC power supply system. The differential coordination calculation verifies whether the upper and lower air switches of DC power supply comply with the design specifications, and whether the fault removing range can be limited to the minimum to ensure the reliability of DC power supply to the greatest extent. This paper explains the basic principle and main method of range matching calculation in detail. Combined with the DC system level difference matching calculation of Qingyuan Pumped Storage Power Station, the paper puts forward the method and suggestions to optimize the DC power system configuration, eliminate the hidden dangers, and strengthen the operation and maintenance.

Keywords

DC system / stage difference coordination / model selection advice