20Hz Injection Kit
In order to implement a 100 % stator earth fault protection based on sub harmonic injection, a 20Hz voltage is injected into the generator star point. The 20-Hz generator SGEN-1001 is used in combination with the band pass filter SBPF-1001 in the Stator Earth fault protection. Injection can be performed by connecting the SGEN-1001 and the SBPF-1001 to the load resistor of an earthing or neutral transformer. If an earth fault occurs in the generator star point, the 20 Hz voltage drives a current through the fault resistance. From the driving voltage and the fault current, the protective relay determines the fault resistance.
20Hz Injection Kit Monitoring Display
The Display used to monitor the 20Hz and 50Hz current passing through NGT transformer. This could help to monitor the stator earth fault and could record the current every minute. The current shall be displayed in milli Amps for both 20Hz and 50Hz. If an earth fault occurs in the generator star point, the 20 Hz voltage drives a current through the fault resistance. The current can be measured using clamp on CT which would clamped between load resistor and NGT. It gives indication if the current values are lower or higher than the set threshold.