Research Of EHV Transmission Line Optical Fiber Phase Current Differential Protection

Fiber-based digital current differential protection, has become the ideal main protection of transmission line. However, there are still some problems in actual operation, such as CT saturation, the load current, the distributed capacitance current and double-end data synchronization problems, be likely to make protection maloperation or closure.This paper analyzes several problems which exist in actual operation of optical fiber current differential protection, especially researches distributed capacitance current and double-sides data synchronization.It summarize several typical criterion of the domestic and abroad. It researches its reasons about the problem of CT saturated, and points OECT can solve this problem. Fault- based component current differential protection may avoid the effect of load current, but exist time of fault component is very short and more difficult to extract. For the effect of EHV long lines for the distributed capacitance, especially to T circuit, is analyzed and simulinked whether the shunt reactor, concluded that domain transient is better than the steady-state compensation, but it could not still compensate fully in the case of no-load closing and other.For the double-end data synchronization, the introduction of device "Clock poor" concept, based on the traditional "ping-pong time", aiding to electric, it can solve the problem that no synchronization of double-sides data, protection misoperations because of imbalance current. Bergeron long line modeling method-based phase current differential protection, it overcomes the impact of distributed capacitive current by comparing the current of same rather than the opposite side; Sampling value differential protection has the advantages of the movement speed and low computation, what is more, which itself has a "natural " anti-CT saturation capacity; Sampling value differential protection based on Bergeron model owes both of their advantages, it analyzes single phase and three phase fault, and then makes a number of typical fault simulation, demonstrates its effectiveness and superiority.Finally, It summaries the full text, and prospects the further work.