Capacitor bank protection for simple and complex configurations

Economical operation of modern power systems requires more distributed voltage support than ever before. Load and distributed generation characteristics have both changed to require increased VAR support throughout the power system. Substation capacitor banks are the most economical form of adding VARs to the system, yet because of harmonics, grounding, and operational concerns, there are many different types of capacitor banks. Capacitor banks also form the heart of filter banks necessary for the application of high-voltage direct current (HVDC) and other flexible ac transmission systems (FACTS) devices. These filter banks also come in a variety of connection types. Microprocessor-based relays make it possible to provide sensitive protection for many different types of capacitor banks. The protection methodology is dependent on the configuration of the bank, the location of instrument transformers, and the capabilities of the protective relay. This paper details the protection methods applied to traditional grounded and ungrounded banks, as well as a number of novel banks with connections that are far from traditional. This paper discusses the application, sensitivity, and speed of the applied protection schemes. Bank configurations studied include traditional as well as C-type filter banks, capacitively grounded banks, and double H banks. Applications beyond protection, such as capacitor fault location, are also discussed to provide added benefits to substation personnel.