Zhou Zexin

Impact of the distributed photovoltaic on the current protection of 10kV distribution network

Compared with other distributed generators, distributed photovoltaic (PV) is quite different in the fault characteristics. The impact of the distributed PV on the current protection of the distribution network is still unclear, making it difficult to guide the operation and management of power grid. In this paper, a typical model of distribution network with the distributed PV is established based on PV inverter control characteristics and relevant technical regulations of state grid corporation of China; the influence of the distributed PV capacity on fault currents of the distribution network is also quantitatively analyzed. Moreover, according to relationship between the different capacity of distributed PV and the amplitude of fault current, the corresponding countermeasures are proposed to provide technical support to renovation of relay protection for the distribution grid with high penetration of the distributed PVs.

Research on Inverter-Based Distribution Generation and its effect on Distribution Network based on PSCAD/EMTDC

This paper has researched the Inverter-Based Distribution Generation and its effects on Distribution Network based on PSCAD/EMTDC Simulink software. The access of the Distribution Generation will change the structure of the Distribution Network, and then the fault characteristic of the Distribution Network will be different. Aiming at these problems, the mathematical model and control strategies of the Inverter-Based Distribution Generation represented by photovoltaic power and Direct-drive Permanent Magnet type Wind Turbine has been analyzed. According to the parameters and control strategies of the gird-connected inverter system, the Inverter-Based Distribution Generation simulation models with Outer inner voltage-current dual closed loop control system has been constructed under the PSCAD/EMTEDC environment, then the influence of IBDG on the fault characteristic of Distribution Network has been calculated. Based on the analysis result, this paper proposed the protection configure strategies of the distribution network adapting to Inverter-Based Distribution Generation.

Dynamic simulation inspection test for protection equipment in China

Testing the protection equipment on dynamic simulation test systems is very valuable not only for finding software bugs and design deficiencies of protection but also for performance and characteristics understanding. To strictly test different kinds of protection relay, the test systems must been designed carefully by selecting the connection and parameters of the system. The test items are designed specially for every kind of protection. This paper introduces some special technical requirements in China, and important test items for different protection schemes. Several ideas and algorithms of some protections are also compared in this paper, such as power swing blocking methods in line protection, current transformer saturation countermeasures in transformer and busbar protection, inrush currents, blocking methods in transformer protection, current transformer single-phase open detection methods, etc. Several problems appeared in the test and the reason of these problems are described and analyzed in this paper.

A phase selection element for zero sequence current differential protection

A phase selection method for zero sequence current differential protection was proposed in this paper. In the first, electrical quantities characteristics of different ground faults were analyzed. Then zero sequence differential current was used as reference value and sizes of sequence differential currents and zero sequence differential current were compared to identify fault phase. Phase differential current was used to identify healthy phase of two phases to ground faults, theory analysis and simulation results show that the phase selection criterion can identify fault phase correctly and is not affect by load current and fault resistance. It is more sensitive than zero sequence current differential protection.