Abstract Transmission system operation with wind generators has been well analyzed for issues like forecasting, reliability, control, power quality, and fault ride through (FRT) impacts following large-scale integration. However, there are still no standardized protection schemes for wind farms such as those practiced for the protection of conventional generation plants. Wind generators’ collective response under high penetration scenarios needs special attention especially under abnormal operations such as grid disturbances and faults. During abnormal grid situations like faults, protection requirements for wind farms depend on a variety of factors. Different wind generation technologies exhibit different dynamic characteristics compared to conventional synchronous generator plants. Network characteristics and their interaction with available wind technologies also impact the fault behavior. This chapter first comprehensively reviews the integration characteristics and criteria for three different wind generator technologies con- nected to high voltage (HV) transmission systems. Aspects such as selection of time step and impact of additional controls such as crowbar protection are also discussed with their possible impacts on fault current estimation. A case study in DIgSILENT® PowerFactory has been developed to assess and compare the fault response of wind generator technology types. The response of each WTG type is generalized and analyzed in time domain to determine the number of electrical frequency cycles before the fault current reaches to steady-state value. Based on the estimated number of cycles and in the scenario of weaker interconnecting grids, protection schemes performance and protection relay operation are mainly assessed for each wind turbine generator (WTG) type. Technical challenges and difficulties are also highlighted before concluding.
Introduction
The protection practices for wind farms are not standardized. This chapter first reviews the general existing protection practice at wind farms. A brief comparison has been made between conventional generation and wind farm layout to further explore the protection design in each case. The chapter discusses a number of factors effecting fault current or its calculation for different wind generator tech- nologies types as highlighted in earlier chapters. In order to investigate possible issues with existing protection schemes in case of a large wind farm, a specific case study representing a weak grid scenario has been established. This case study, thereafter, is assessed for all the four types of wind generator technologies at the same time. Through dynamic analyses using DIgSILENT® PowerFactory, com- parative fault behavior analyses are achieved. Using results from the case study, the protection performance of each individual WTG type is investigated. Challenges to wind technology modeling and standardization efforts are also high- lighted in this chapter.