A interturn fault protection method of HV shunt reactors based on unbalanced parameter detection

An interturn fault protection method of the HV shunt reactor is put forward in this paper, which is based on the unbalanced parameter detection. This method is established on the basis of the time-domain parameter model, and uses the electrical quantities at two terminals of the HV reactor to calculate the electrical parameters of each phase by mean of least squares algorithm. Suppose that the interturn short-circuit faults of the HV phase-separated shunt reactors impossibly occur at three phases at the same time, we could identify whether the interturn short-circuit fault of the HV reactor occurs by designing the comprehensive detection criterion which could reflect three-phase unbalanced parameters and parameter mutation. The interturn protection of HV reactors could avoid the impact from power swings and frequency deviation. This method is based on the measurement and the comparison of per-phase equivalent inductance parameters of the reactor. The setting of the protection is simple and convenient to implement. Furthermore, the protection has high sensitivity. Because this interturn protection detects the variation of per-phase inductance parameters, it could avoid the influence from the system operating mode and the fault while those based on the principle of sequence components cannot. It is also adaptive to the installation location of the voltage transformer (PT), and could be easily applied to HV reactors of both transmission lines and busbars.