Sub transmission voltage regulators
Sub transmission voltage regulators
(OP)
Hi guys, I will start with I am not a Engineer but work as a HV ( LV to 33kv ) distribution designer and have a question for the knowledgeable engineers on here. I have recently upgrade a 3 tank 3 phase star connected 33kv voltage regulator site from 200A regs ( 22kv rated) to 300A regs( 22kv rated )... When comissioned one of the regs had a growling/vibrating noise being emitted. The decision has been made to put them in by-pass and take them out of service to remove offending unit for testing and maintenance... Our zone substations group was arranging to put one of the old 200A reg units back up in place of the 300A being removed for testing as to keep the site "online". I've put a stop on this as I have concerns about the differing impedences of the 200 and 300 amp units and the effect this will have on the common star point. I feel there will be an out of balance created and cause a rise on the earthing system connected to the star point along with other issues that are beyond my ability to figure out. Our zone subs engineers "thinks" it will work but couldn't give me any concrete evidence it would. Has anyone had experience in this situation and could anyone explain the full effects that could happen to the sub-transmission system if the 200A was put in place... Thank you in advance for any responses.






RE: Sub transmission voltage regulators
RE: Sub transmission voltage regulators
RE: Sub transmission voltage regulators
RE: Sub transmission voltage regulators
The primary wye point will give you a stable neutral reference for the regulators.
50 KVA or 75 KVA will probably be large enough.
100 KVA will be better.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Sub transmission voltage regulators
RE: Sub transmission voltage regulators
We seem to be getting away from the original question, I will follow up on the earthing situation tomorrow ( they were meant to test earth continuity from each tank to earth ring and resistance to earth of the ring) and ferroresonance suggestions, thank you very much for these. But if someone could explain what the effects would be of putting the 1 x 200a reg into service with 2 x 300a on a locally grounded ( local earth ring at site , no O/H earth system neutral) in Wye configuration,and why it would or wouldn't work, I would be forever grateful...
RE: Sub transmission voltage regulators
My understanding is that the NESC requires a neutral run back to the supply substation for any wye connected loads and I would imagine the IEC requires the same.
RE: Sub transmission voltage regulators
RE: Sub transmission voltage regulators
RE: Sub transmission voltage regulators
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Sub transmission voltage regulators
In the meantime, let us know the following background information:
- Why the 200A units were replaced by the 300A rated units?
.- There is any issue with overvoltage or large harmonics (3rd & 5th harmonics could be an issue for Y connection)
.- Is the connected load greater than 11 MVA?
.below are a few remark and extra information that I hope could be helpful to advance this thread from good opinion to more concrete technical answer:
RE: Sub transmission voltage regulators
Waross - sorry mate didn't even think of single phase subs. Ours are only made up to 25kva in singles, so went straight over my head.
Cuky2000 - sorry was out of the office today will chase up impedences tomorrow, will try get some photos of name plates uploaded.
They are being upgrade due to a significant load increase on the line in the next couple of months. They were nearly maxed as it was and will nearly be maxed out again once the new loads are applied ( this is what I have been told by planning dept) and will continue to be heavily loaded until a new additional feeder can be built.
The issues are with under voltage due to the length of the feeder/ the amount of load on the line. It would be approx 60km long with large inductive loads (Chicken sheds and pumping loads) at the extremities and many SWER feeders off the main line, conductor is 3W 19/3.75mm AAAC (Neon). This feeder is also a back feed for another town about 120km away if the 132kv radial for that town goes down...
RE: Sub transmission voltage regulators
RE: Sub transmission voltage regulators
The large unit appear to run above the 20MVA load current rating. If one of the larger unit is substituted by one of the smaller regulators, the situation to be at risk to operated at overloaded conditions even without considering the effect of potential circulating current and the impact of the 3rd & 5th harmonic derating effects.
Did you considered to run temporarily in open delta with a reduced capability?
Could you please clarify the rating provided earlier "200A regs @ 22kv rated and 300A regs @ 22kv rated" connected to a 33 kV delta system (Phase-phase-to-phase).
See a typical voltage regulator rating below.
RE: Sub transmission voltage regulators
RE: Sub transmission voltage regulators