ROCOF settings
ROCOF settings
(OP)
Hi All,
Can somebody give me any guidelines on what settings to use for rate of change of frequency? Would you normally do some simulations before choosing settings or just use a 'generic' recommended one.
Also, would you tend to use normal ROCOF or frequency supervised one?
Can somebody give me any guidelines on what settings to use for rate of change of frequency? Would you normally do some simulations before choosing settings or just use a 'generic' recommended one.
Also, would you tend to use normal ROCOF or frequency supervised one?






RE: ROCOF settings
Is this for a large scale load shedding scheme?
I have seen simple underfrequency relays used for load shedding at a large plant as a condition of supply from the utility.
A drop in frequency was taken as an indication that the grid was overloaded and the plant was warned to curtail usage at 58 Hz. If the frequency dropped to 56 Hz there was an automatic trip of the main breaker.
Are you using rate of change to discriminate between events that may be ridden through and events that demand an immediate trip?
Bill
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"Why not the best?"
Jimmy Carter
RE: ROCOF settings
RE: ROCOF settings
and MVA rating, this is not an accurate method for setting a ROCOF relay because the rotational inertia of
the complete network being fed by the generation is required. If you have a system with a small inertia then the frequency response will be faster. You should be able to come up with some underfrequency settings that dump the load before the system collapses because the frequency excursion will be rapid with a small system. If you try to implement ROCOF on a small system you will be very susceptible to false trips. It is more typically used as anti-islanding protection rather than for load shedding.
Regards
Marmite
RE: ROCOF settings
Why do you think there would be a lot of false trips? If I set the relay to, let's say, 5Hz/s this is some serious ROCOF now and shouldn't happen under healthy conditions. Unless what the relay is measuring and what is actually happening on the system doesn't align...
RE: ROCOF settings