DC-offset faults on 38KV utility lines
DC-offset faults on 38KV utility lines
(OP)
Hello all,
On occasion there has been known to be DC-offsets that occur on 38KV utility lines during some fault conditions. The fact that these faults rarely exist still prompts the switchgear controls to delay opening the breaker five cycles. Apparently the DC-offset fault is cleared in most cases inside of five cycles. I am wondering if anyone has any information on how to measure these DC-offsets on AC utility lines of this nature. Thanks for any help.
On occasion there has been known to be DC-offsets that occur on 38KV utility lines during some fault conditions. The fact that these faults rarely exist still prompts the switchgear controls to delay opening the breaker five cycles. Apparently the DC-offset fault is cleared in most cases inside of five cycles. I am wondering if anyone has any information on how to measure these DC-offsets on AC utility lines of this nature. Thanks for any help.






RE: DC-offset faults on 38KV utility lines
I usually don't see much offset beyond 3 cycles.
RE: DC-offset faults on 38KV utility lines
RE: DC-offset faults on 38KV utility lines
RE: DC-offset faults on 38KV utility lines
RE: DC-offset faults on 38KV utility lines
Asymmetrical fault current is the norm, not the exception. The decay of the dc component is a function of the system X/R ratio looking into the fault. It is also a function of the voltage phase angle at the time of the fault, so it will be different in each phase.
RE: DC-offset faults on 38KV utility lines
RE: DC-offset faults on 38KV utility lines
As for saturation of current transformers due to dc currents, this is not instantaneous. Virtually any level of dc current will eventually saturate a CT, but it takes time. This is a well-researched topic so you should be able to find plenty of information on this.
I have no idea what you are trying to accomplish, but before you invest much time on this, you might want to do a good search of previous research. This is a mature field, so you may be re-inventing a new wheel.
Good luck.