We have a problem with the Voltage regulator in Piha. This one is actually a bank of two auto transformers which can step up or down and regulate the feeder voltage within ± 10%, over 16 steps either way.
The set up is for one regulator in the red phase and one in the blue phase ( 2 wattmeter method ).
Some photo's are in the photo gallery to give an idea of the set up.
It must have gone with a good bang. 2 * 11kV Lightning arrestors were blown off the pole and one 3 kV arrestor across the series winding gone up in fire as well.
No thunder or lightning prior to the faillure which happened last week wednesday.
These units are put at the end of long 11 or 22 kV feeder lines where the voltage can be down by 8 to 10 % and this way it can be boosted to avoid voltage complaints.
These areas don't have the population base to warrant a 7.5 MVA substation.
The LV voltages were with the bypass switch closed down to around 211 Volts instead of a normal 235 Volts.
Today we tested the replacement spare unit with the winding ratio tester, in the workshop and got a heavy hiab in to put the unit in service position on the pole platform, with traffic management in place.
Tomorrow will be the livening up and complete commisioning because this afternoon the weather turned to custard.
Interesting to disassemble the unit and see what was wrong with it.
I wonder if these arrangements are used in other countries around the world as well.
It has been quite on the non US forums hence this post about some local utility work in New Zealand.
Regards, Raymond
Last edited by RODALCO; 04/16/08 06:03 AM. Reason: typo's
