Reducing Partial Discharge Activity in a Large Generator Unit by Increasing Hydrogen (H2) Pressure

There are several coal-fired power plants in Indonesia. Typically, this power generation district consists of some generator units with a capacity of several thousand MW. Generators with large capacities are generally hydrogen-cooled, water-cooled, or a combination of both. One of the problems that occur in a generator is the high partial discharge (PD) activity at several areas within the stator part. The phenomenon of partial discharge can be recorded by the coupling capacitor sensor and the Resistance Temperature Detector (RTD) Module assembled into one monitoring equipment. The Coupling Capacitor function is to detect partial discharge for each phase, while the RTD module function is as a partial discharge detector through radio frequency and correlates it with temperature and humidity data in a wide range of sensing and spreads throughout the generator winding area. This paper describes the Partial Discharge in the hydrogen-cooled generator and how to reduce the Partial Discharge activity. Hydrogen pressure effects on the Partial Discharge activity were investigated. Partial discharge activity is observed in the form of point of view magnitude and pulse per cycle (PPC) by varying the pressure. Increasing the pressure is taken as a mitigation step so that the generator can operate continuously until the time for rewinding comes. It was found that partial discharge activity reduced significantly as the hydrogen pressure on the generator is increased from the nominal pressure. The Partial Discharge Intensity value can decrease from 250 milliwatts to around 160 milliwatts at a pressure of 0.35 MPa and can even decrease to an average value of 120 milliwatts at a pressure of 0.4 MPa This phenomenon was explained by using the increasing of Partial Discharge inception according to Paschen Law for hydrogen.