Ferroresonance
Ferroresonance
(OP)
Hi
Does anybody know where theres a good reference or a document that suggests limitng length of cables terminating to a 1500KVA 27.6/600 delta-wye transformer? In my application total length of cables is approximately 438m (375m underground and the rest is above ground on a roof) before it terminates to a 1500KVA transformer. In order to convince the owner to extend the aerial network closer to the transformer, need a credible document.
Does anybody know where theres a good reference or a document that suggests limitng length of cables terminating to a 1500KVA 27.6/600 delta-wye transformer? In my application total length of cables is approximately 438m (375m underground and the rest is above ground on a roof) before it terminates to a 1500KVA transformer. In order to convince the owner to extend the aerial network closer to the transformer, need a credible document.






RE: Ferroresonance
RE: Ferroresonance
RE: Ferroresonance
A three phase pole mounted vacuum switch and set of PTs just beyond the fuses for the underground run could be set up with loss of phase protection.
RE: Ferroresonance
Would it be possible to mount a 34.5kv recloser with a 3 phase transformer that will open the cable with a loss of a phase at the point where the line goes underground? It may not be the best solution but its the only solution I can think of at the moment.
RE: Ferroresonance
What I am wondering is even if Ferroresonace phenominon is a singnificant issue in the power system distribution/protection, we are not able to find a published document by any of the utilities that outliens sugested cable lenghts for various voltage and transformer sizes?
RE: Ferroresonance
"Throughout space there is energy. Is this energy static or kinetic! If static our hopes are in vain; if kinetic — and this we know it is, for certain — then it is a mere question of time when men will succeed in attaching their machinery to the very wheelwork of nature". – Nikola Tesla
RE: Ferroresonance
RE: Ferroresonance
The DSTAR results look about right for 7.2 kV phase to ground. Couldn't resist!
With a delta high side connection and 27.6 kV, it is likely that you've gone beyond the limits of cable lengths to avoid ferroresonance. Without looking at the DSTAR results, I think they were all based on grounded wye grounded wye transformers since our company and two others participated in the field tests.
The 8% minimum load will likely reduce the voltage magnitudes when single phase switching occurs but going with a gang operated three phase switch would be a wiser idea.
RE: Ferroresonance
For a 1000 KVA delta-wye transformer critical length of conductor at 13.8 kV is 69 ft cable and at 34.5 kV , 11 ft cable.But this may not be an issue, if only three phase switching is used and switches are located at the transformer terminals.