Excitation System of Hydro Power Generator

Abstract

In modern hydroelectric power plants, synchronous generators are commonly used due to their ability to deliver stable and efficient electrical power. For proper operation of a synchronous generator, an excitation system is essential as it supplies direct current to the rotor winding. In high-capacity hydroelectric generating units, such as 40 MW generators, a large and reliable excitation system is required to maintain voltage stability and system performance under varying load conditions.

The Lower Jurala Hydroelectric Power Plant consists of six generating units, each having a capacity of 40 MW. Due to the large rating of these generators, the excitation system must be robust and capable of providing sufficient field current. A secure and well-designed excitation system ensures smooth generator operation, improves system reliability, and enables the generator to withstand abnormal operating conditions and electrical disturbances. To protect the generator and excitation system from abnormal operating conditions, various protection schemes are provided such as voltage protection, stator current protection, over-excitation and under-excitation protection, and digital control protections. Each unit is equipped with an Automatic Voltage Regulator (AVR) and Field Current Regulator (FCR) for controlling terminal voltage and excitation current. In digital excitation systems, a small error margin known as droop, typically ranging from 0% to 5%, is maintained to ensure continuous relay operation and system stability. Since the excitation system handles high currents, it is prone to temperature rise during operation. Therefore, adequate heat sinks and cooling systems are provided to dissipate heat effectively, ensuring reliable performance and long service life of the excitation system. It also reduces maintenance requirements and improves overall system availability.