topgroove
05-04-2008, 05:48 PM
Just a little lesson for some of the younger guys without much expierence with un-grounded delta primarys.
I got a single no lights call last friday night. arrived at the address and noticed it was single phase 4.8 kv delta primary. It was a rural country road with each customer on thier own transformer. checked the service out for a tree problem and everything was in the clear. noticed the customers on either side had their own transformers and were in power. went up and tried to reset the switch ( it was a 25kva csp ) dead at the secondary bushings. checked the voltage at the primary bushings and found 0 volts at H1 and 6000 volts on h2. checked the primary out and found 0 volts on A phase and 6000 volts on B phase. Phase to phase A to B was also 6000 volts. can you guess what the problem was.
I got a single no lights call last friday night. arrived at the address and noticed it was single phase 4.8 kv delta primary. It was a rural country road with each customer on thier own transformer. checked the service out for a tree problem and everything was in the clear. noticed the customers on either side had their own transformers and were in power. went up and tried to reset the switch ( it was a 25kva csp ) dead at the secondary bushings. checked the voltage at the primary bushings and found 0 volts at H1 and 6000 volts on h2. checked the primary out and found 0 volts on A phase and 6000 volts on B phase. Phase to phase A to B was also 6000 volts. can you guess what the problem was.