synchronization of 4-generators in parallel
synchronization of 4-generators in parallel
(OP)
A typical transformer unit of a power plant comprises:
- A step-up transformer with 3 windings 230 kV (star grounding) -13, 8 kV (delta) -13, 8 kV (delta)
- Two bus generation directly connected to 13.8 kV low voltage side of step-up transformer
- Each two hidrogenerators are connected to the bus generation through circuit breaker.
The high side of transformer is connected to SF6-substation through circuit breaker.
The ideal procedure for synchronizing the power plant to the 230kV system would be:
- Synchronize the four generators at the LV transformer by bus generation.
- Synchronize HV transformer to SF6-substation by controlling the set of four generators.
People of regulation and governor do not agree , because of circulating current between generators. Generators should be connected one by one.
Someone could explain the problem?
- A step-up transformer with 3 windings 230 kV (star grounding) -13, 8 kV (delta) -13, 8 kV (delta)
- Two bus generation directly connected to 13.8 kV low voltage side of step-up transformer
- Each two hidrogenerators are connected to the bus generation through circuit breaker.
The high side of transformer is connected to SF6-substation through circuit breaker.
The ideal procedure for synchronizing the power plant to the 230kV system would be:
- Synchronize the four generators at the LV transformer by bus generation.
- Synchronize HV transformer to SF6-substation by controlling the set of four generators.
People of regulation and governor do not agree , because of circulating current between generators. Generators should be connected one by one.
Someone could explain the problem?





RE: synchronization of 4-generators in parallel
As far as I'm concerned, the ideal order would be energize the transformer from the 230kV side and then parallel each generator one at a time across its own 13.8kV breaker.
Obviously that wouldn't work for black start if that is a concern.
RE: synchronization of 4-generators in parallel
RE: synchronization of 4-generators in parallel
RE: synchronization of 4-generators in parallel
...from the 230kV side and then parallel and add load each generator one at a time across its own 13.8kV breaker.
RE: synchronization of 4-generators in parallel
You could energize the transformer from the 230 kV side but bringing it up with the first generator avoids inrush issues.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: synchronization of 4-generators in parallel
...Then synchronize(at 230kV) with the substation or grid. The pick up some load and proceed to sync(at 13,8kV) and load the other generators one by one.
RE: synchronization of 4-generators in parallel
RE: synchronization of 4-generators in parallel
1- normal synchronization
the ideal order would be energize the transformer from the 230kV side and then synchronize and add load each generator one at a time across its own 13.8kV breaker.
2- black start:
-connect the transformer to the first generator before the generator is started and ramp the transformer up with the generator and connect to substation 230kV ( previously desenergized)
-Connect 230kV transmission line up to remote busbar substation.
- Add some load.
- For other generators synchronize and add load each generator one at a time across its own 13.8kV breaker.
My concern is the inrush current of transformer in black-start over generator:- If we assume a value of 10 times rated current transformer, this will be 40 times rated current generator.
RE: synchronization of 4-generators in parallel
RE: synchronization of 4-generators in parallel
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: synchronization of 4-generators in parallel
At another power plant with a similar case, they should modify the ramp of automatic starting of AVR and other precautions.
I do not know how the energization sequence of the this power plant.
In what case , could that happened?
RE: synchronization of 4-generators in parallel
The frequency and the voltage may be ramped up together to maintain the Volts/Hertz ratio.
The generator may be brought up to speed and then the voltage may be ramped up.
The second method is not suitable for starting relatively large motors.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: synchronization of 4-generators in parallel
- could increase tension in the generator very slowly to the rated value.
Manual starting is only for maintenance.
The automatic starting by regulators is the operating procedure.
In this case there is the risk of inrush current.
RE: synchronization of 4-generators in parallel