Research On The Relay Protection Of 10kV Distributed System With Photovoltaic Generation

The development of renewable energy is an effective and feasible way to solve the problem that the fossil energy is on the verge of exhaustion. In the process of using energy to power generation, considering all kinds of environmental reasons and the development ability of energy, photovoltaic power generation is the most obvious and the most development potential. In recent years, China’s photovoltaic power generation technology can be described as a rapid development. The permeability of grid connected photovoltaic power is also increasing, which brings the challenge to the distribution network. The characteristics of the system, the distribution of power flow, the flow direction of short circuit current and the node voltage will be changed because of its access. The configuration of the original protection no longer meet the requirements, is no longer applicable to the current distribution network environment. Distribution network will no longer be stable and reliable operation, electrical equipment will be damaged, and the worst case situation is a chain reaction that causes a large area power outage and eventually a power system paralysis. Therefore, the research of this subject has profound practical significance.First of all, it introduces some related concepts, tasks and requirements of Relay protection, as well as three-current protection operation principle often used in the traditional distribution network and the principle of setting and the sensitivity checking method. And explain how the protection of mutual cooperation between the operation, the reliability of the fault isolation. The main functions and relative parameters of photovoltaic power supply model and inverter in ETAP software are introduced in this paper. Based on the structure and protection characteristics of the actual distribution network, the lOkV system model was established by using ETAP software, and the parameters of each component in the model were set up scientifically and reasonably. The model design of this paper is scientific and reasonable by the way of running power flow.Secondly, in theory, the impact of different access conditions on the protection of PV is analyzed in detail. Based on the simulation model of ETAP software, the three factors which affect the normal operation of the Relay protection are the access capacity, the location of the access point as well as position relation between fault point and access point. And Simulation Analysis on the specific impact of protection while only one of the three factors undergo changes. According to the simulation results, it is concluded that the location of the fault point, the location of the protection and the PV access point, the position relationship between the three points will have different effect on the short circuit current.Finally, according to the specific situation, the access capacity of the photovoltaic power supply is calculated, and the capacity of the access is limited on the basis of the original protection configuration. Using the ETAP software to verify the above strategies, and also confirm the correctness of the theory part.