ETAP generator modeling - swing & voltage control
ETAP generator modeling - swing & voltage control
(OP)
I will have 12 480V generators in parallel with KW and KVAR load sharing connected to a 4160V bus through a bunch of 2500kVA transformers. I am attempting to run a Dynamic motor start study with one 5000HP motor running and one 5000HP motor starting on the 4160V bus. The 5000HP motors are started on a 250% to 350% current ramp soft starter.
Here is my issue:
Upon hitting the start button, the voltage will initially drop. In reality, then generators' AVR's will excite the generator into providing more VAR than the motor requires to start, which will pick the voltage back up to 480V (on the generator terminals) even while the motor is accelerating. I don't know how to simulate this using ETAP.
All the generators are identical - there is no "swing" generator or a "voltage control" generator. They all provide the KW and KVAR required by the load, plus KVAR to raise the voltage to near nominal volts. In ETAP, when I put the generators on "swing", they do not react to correct voltage. When I select "voltage control", the KW output does not change with the load requirements.
I know that there must be one "swing" generator on the system for ETAP to operate correctly. Is there any way I can get the generators to have both properties - swing and voltage control at the same time?
Here's a graph of the voltage vs time during the motor acceleration. The green line is ETAP's calculation (I would expect the curve to look like this if the power source was utility power with no voltage regulation). The red (which I drew in using mspaint) is what I would expect the actual voltage to look like in my scenario.
http://files.engineering.com/getfile.aspx?folder=88f42dd5-edaa-4db1-9894-e9932fa220bd&file=voltage_vs_time.bmp
What do you guys think?
Here is my issue:
Upon hitting the start button, the voltage will initially drop. In reality, then generators' AVR's will excite the generator into providing more VAR than the motor requires to start, which will pick the voltage back up to 480V (on the generator terminals) even while the motor is accelerating. I don't know how to simulate this using ETAP.
All the generators are identical - there is no "swing" generator or a "voltage control" generator. They all provide the KW and KVAR required by the load, plus KVAR to raise the voltage to near nominal volts. In ETAP, when I put the generators on "swing", they do not react to correct voltage. When I select "voltage control", the KW output does not change with the load requirements.
I know that there must be one "swing" generator on the system for ETAP to operate correctly. Is there any way I can get the generators to have both properties - swing and voltage control at the same time?
Here's a graph of the voltage vs time during the motor acceleration. The green line is ETAP's calculation (I would expect the curve to look like this if the power source was utility power with no voltage regulation). The red (which I drew in using mspaint) is what I would expect the actual voltage to look like in my scenario.
http://files.engineering.com/getfile.aspx?folder=88f42dd5-edaa-4db1-9894-e9932fa220bd&file=voltage_vs_time.bmp
What do you guys think?






RE: ETAP generator modeling - swing & voltage control
In your figure, it appears that the AVRs do respond to the transient in around 1-second. Attached is a good reference that shows the transient responses to an event for different devices. At approximately 1 second the AVRs do correct the voltage to pre-start values so the model seems correct.
RE: ETAP generator modeling - swing & voltage control
As far as I think, the current ramp starter will not help in the motor starting. Because even though it will improve the voltage at the generator bus, it will drop the voltage at the motor terminals. Because by principal, the soft starter decreases both the current and voltage across the motor terminals.
RE: ETAP generator modeling - swing & voltage control
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: ETAP generator modeling - swing & voltage control
RE: ETAP generator modeling - swing & voltage control
Bill
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: ETAP generator modeling - swing & voltage control
RE: ETAP generator modeling - swing & voltage control
You should contact Hamid at ETAP in Irvine,CA. He is the generator modeling expert and one of the key ETAP developers.
RE: ETAP generator modeling - swing & voltage control
RE: ETAP generator modeling - swing & voltage control