The Research Of20kV Distribution Network Adaptive Relay Protection

With the increasing density of power load, more power supply capacity is needed.The10kV distribution network is difficult to satisfy the needs of distribution network development. It is feasible to boost the existing10kV distribution network facilities to20kV. Some pilot cities or regions have been put it into operation.It is the inevitable trend of development to use20kV voltage level distribution network. When the distribution network voltage level upgrades, users’ requirement of relay protection of the distribution network will also improve. The conventional relay protection has exposed a lot of flaws, such as changes in operation modes and the types of fault will reduce protection performance, etc. Hower, the adaptive protection can overcome the shortcomings of traditional quick break protection,and change the protection action setting value in real time according to load size, operation mode and the change of fault type, significantly expanding the scope of protection. So the protection can reach the best condition.Firstly, the domestic and foreign development status and trends of20kV distribution network and Adaptive Protection technology are presented in this paper. An adaptive instantaneous trip current protection theory based on phase current fault component is proposed. And a analysis comparison between traditional relay protection and Adaptive Protection theoretical ismade.The results show that the Adaptive Protection can automatically adapt to changes in grid operation conditions, but also has a broader scope of protection than traditional relay protection.The data processing method of Adaptive Protection theoretical is described in details and Fourier series algorithm is selected for data acquisition and processing for its filtering effect.Secondly, a simulation model of20kV distribution network is established by MATLAB/Simulink simulation software. The situations are simulated, includingthe phase current differential fault component based Adaptive Protection algorithm, adaptive voltage protection, traditional voltage-current protection.The simulation results are consistent with the theoretical analysis results.The20kV distribution network ground is briefly introducted..Then a simulation mode ofsingle phase to ground fault is established with low resistance grounding, no grounding and the arc suppression coil grounding manner. The simulate results show that zero sequence current protection is required when the20kV distribution network grounds through the low resistance. Acooring to simulation results,the improvement opinion is put forward on zero-sequence current protection.