HOW TO MEASURE ZERO SEQUENCE IMPEDANCE OF AN EARTHING TRANSFORMER
EARTHING TRANSFORMER IS AN IMPORTANT PART OF UNGROUNDED POWER SYSTEM. IN ANY POWER SYSTEM WHICH IS FEEDED FROM DELTA SIDE OF A POWER TRANSFORMER OR A GENERATOR THERE IS NO PATH FOR ZERO SEQUENCE CURRENT TO FLOW TO EARTH. OR WE CAN SAY THERE IS NO EARTH REFERENCE FOR THIS TYPE OF POWER SYSTEM. BUT FOR PROPER OPERATION AS WELL AS PROTECTION POINT OF VIEW THIS TYPE OF POWER SYSTEM NEED AN EARTH REFERENCE, AND THAT IS PROVIDED BY EARTHING TRANSFORMER. EARTHING TRANSFORMERS ARE ALSO CALLED AS GROUNDING TRANSFORMER AND IN ANY DELTA BUS THERE MAY BE ONE OR MANY EARTHING TRANSFORMERS CONNECTED SIMULTANEOUSLY.