Abnormal Voltages on distribution Feeders
Abnormal Voltages on distribution Feeders
(OP)
Is there anyone out there that might be experiencing this problem. The problem is on our 13 kV distribution system, our C Phase bus voltage is significantly lower than both A and B phase. Initial investigation found that A phase had slightly leading power factor. However all capacitor banks were taken off of this particular phase and the problem was not resolved. Then the problem is starting to show up on other parts of the system and consistently A phase is higher than both B and C by approximately 3-5 volts on a 120V base. The laods are generally balanced between all three phases. The issue is that when C phase voltage is at 120, my A phase voltage is at the top of the Tariff. Unfourtenately, I do not then have room for the LTC on the transformer to increase witout having high voltage. Is there anyone out there that has ever heard of a similar problem and what they have found
Thanks
Chris
Thanks
Chris






RE: Abnormal Voltages on distribution Feeders
RE: Abnormal Voltages on distribution Feeders
RE: Abnormal Voltages on distribution Feeders
What does not make sense is that in other substations where the load is imbalanced, the voltage will be almost perfectly balanced.
Thanks for your quick response. I do appreciate it. If you do know anything, please pass along
Thanks
Chris
RE: Abnormal Voltages on distribution Feeders
RE: Abnormal Voltages on distribution Feeders
Have you confirmed that the ammeter readings are correct and that the system is genuinely balanced?
As mentioned above, what is the nuetral position reading?
Is the LTC operating in boost or buck (raise or lower)?If there was a shorted turn in the regulator coil, it seems like the condition would reverse in the opposite direction. Does it?
Last resort would be to take the xfmr out of service and do a transformer turns ratio test on each phase.
RE: Abnormal Voltages on distribution Feeders
RE: Abnormal Voltages on distribution Feeders
What is the type of earthing adopted in your 13kV system. Is it high impedance grounded or isolated system!! Even if not, do you think there could be some problem in the transformer neutral - to - earth circuit, such as loose connection or open circuit!!
How much are you sure that the problem is in 13kV system and not in the VT / VT secondary circuit!! More often, this kind of things happen because of some trouble in the VT windings. If your system is old, you should especially suspect this.
RE: Abnormal Voltages on distribution Feeders
The last thread posted...we have a multigrounded distribution system. Also the problem is system wide, not isolated to just one or two substations.
Thanks for the help.
Also, am I way off on the possibility of the change of A phase from H1 to H3?
Thanks
Chris