etap mode problems

[Ali Mohamud Jisow]

Hi everyone I am Júnior engineer and i started using etap 19.0.1 and i am responsible for etap and designing in my company I made single line diagram of my company consist of 8 generators 6 of them are low voltage means 415V which have 1.5 mva each one of them and that is 9 mva all of the 6 generators and then they connected by synchronizing panel and then three transformers which have 2.5mva each one of them and then 11kv switchgear and other hand i have 2 generators which have 11kv and 2.5 mva are connected directly to the 11kv switchgear when i made load flow i faced these problems, when i choose swing mode all my load comes into 2 generators of 11kv and they overloaded when i chose one of the 11kv generators in swing and all my grid generators to voltage control or other mode this generator became overloaded. how i solve for that problems?

 

[dpc]

Double check of your entered data, especially the generator voltages, kVA, and impedances. Also verify that ETAP allows multiple generators to be in swing mode when operating in parallel. If not, put the largest unit in swing and changes others to voltage control. Verify that your voltage setpoints in ETAP are basically the same for all units. Also, check all of the cables and other impedances between the generators for a major data entry error.

 

[waross]

One and only one generator in swing mode or isochronous mode.

All other generators in droop mode above nominal frequency.
Apply this to each droop mode generator:
No frequency is given so I will use 50 Hz for an example.

With the governor set to 50 Hz, the generator will not pick up any load.
With the governor set to 50 Hz plus 1.5 Hz, or 51.5 Hz, the generator will pick up full rated load.
The following settings will determine the load that each droop generator will pick up.
10% of 1.5 Hz is 0.15 Hz.
Speed setting, / load as a percentage of rated load.
50 Hz / 0% of rated load.
50.15 Hz / 10% of rated load.
50.3 Hz / 20% of rated load.
50.45 Hz / 30% of rated load.
50.6 Hz / 40% of rated load.
50.75 Hz / 50% of rated load.
50.9 Hz / 60% of rated load.
51.05 Hz / 70% of rated load.
51.2 Hz / 80% of rated load.
51.35 Hz / 90% of rated load.
51.5 Hz / 100% of rated load.
The droop sets do not have to be at the same settings.
I knew of one hydro set that was kept spinning at 10% of rated load when it was not needed and ramped up to 90% of rated load when extra capacity was needed.

The number of generators on-line and the total load picked up by the droop generators must be controlled, either manually or by some sort of load control system.
Typically, as the load increases or decreases, the load dispatch system Increases or decreases the load picked up by the droop machines or calls up more droop machines to be added to the grid, or drops some machines off of the grid.
The load is balanced to keep the swing set at around the mid-range of its rating.

 

[waross]

Voltage settings, cable impedances, transformer impedances, etc. have an effect on the reactive power and on the power factor.
Voltage control is an AVR function.
Only the prime mover input, as controlled by setting the frequency of a droop machine above nominal frequency, varies the real power output.
Frequency control is a governor function.
The only way that two machines can work together in isoch. mode is if a load control panel is monitoring the frequency and independently varying the throttle controls of two or more machines.
The easiest way to do this is if the controlled machines are in droop and the load control panel controls the frequency setting of the machines, so the actual machines are not really in isoch. mode.