Investigation of loss-of-mains detection on induction generators based on simple reactive power changes detection

Abstract

A self-excited induction generator (SEIG) is widely used in micro hydropower plants. Generally, in Indonesia, the plant is integrated to a secondary distribution line and acts as a distributed generation (DG). If the distribution line is disconnected from the grid (loss-of-mains, LoM), then the plant must be immediately isolated before the distribution network contact equipment closes back in an out-of-synchronous mode. Voltage relays and frequency relays are commonly used to detect the occurrence of LoM on plants using SEIG. However, those relays are unable to detect all of the LoM events. This paper describes the excitation capacitor sizing strategy so that the direction of the reactive power flow changes in the event of a LoM. The change of direction of reactive power flow was used as an indicator of the occurrence of LoM. Detection of the direction of reactive power flow was done by manipulating the multiplication of instantaneous voltage and current. The result of excitation capacitor determination and LoM detection method was simulated using SIMULINK-Matlab. The simulation results showed that the proposed method could detect LoM, which could not be detected either by voltage relays or by frequency relays. The disadvantage of this method was not able to detect the LoM if the load and the power grid were capacitive. However, it is almost certain that the load and the distribution network are always inductive. The results of this study can be used as a direction for the application of LoM protection on SEIG.