Relay Rehabilitation Programs In Bus Transformation Project

Zhejiang500kV-substation's220kV bus is commonly used dual-bus-dual-segmented wiring, which is completed in phases:phase one,dual-bus-no-segmented wiring,with only#1bus-contact breaker and its isolators installed;phase two,dual-bus-single-segment wiring,adding#2bus-contact breaker and positive-section breaker; phase three,the final form of dual-bus-dual-segment wiring, adding negative-section breaker. There is a more complicated switching operation and wiring transformation throughout the "three-step" program.It will bring a more complex loop transformation by design and reconstitution time after time, with the following alteration much more complex.It conflicts with ZheJiang Electric Power Corporation,because power reliability evaluation is very strict at present. It becomes much more cautious to approve power cut plan, because users and businesses do not want any power outage. There is nobody or fewer people on duty in most substation, but more and more tasks, which increase the risk of power system for different types of work. Too many unnecessary reconstruction will greatly increase operating personnel and construction workers'work intensity and workload, and lead to t various errors.This paper presents a rehabilitation programs about220kV bus changed directly from the dual-bus-no-segmented wiring to dual-bus-dual-segmented wiring, which will reduce the workload, the power grid and personnel risks.The article is divided into four parts. The first part describes the basic principles, including preventing any extended power outage, reducing the switch operation, reducing the difficulty and the risk, etc. The second part describes the "two-step" program in detail, including the voltage, current, DC power supply and switch circuit transformation of220kV transmission line protection, transformer protection and busbar protection. Part three evaluates the "two-step" program, pointed out that compared with "three-step" program,the "two-step" program has advantages in the feasibility, economic, risk and complexity. Part four analyses the problems in " two-step " program, and proposes solutions to the problem of the REB-103composite voltage lockout circuit,and the problem of REB-103secondary contact's poor contact, which may lead to relay protection malfunction or tripping proposed a viable solution.