Electrical outages. cyber attacks ?

John,

Very well said. The obvious conclusion that I see is that the setting of the RoCoF should be re-evaluated. Having spent most of my career dealing with ships I am aware of the frequency transients that occur when large loads are switched and the standards (e.g. IEC 60092, BS8450) and the Class Society Rules (e.g. LR, DNV, ABS, etc.) allow a 5% permanent deviation and a 10% transient deviation with a recovery time of 5 seconds, so obviously a 10% deviation has a minimum RoCoF of 2.0 Hz/s (from the initial excursion beyond the permitted 5% deviation down to 10% then back up to the permitted 5%). In reality the rate of change is much faster on the way down than during the recovery and so is probably around 10 Hz/s since the load switched is probably a relatively large percentage of the generating capacity (say 10%) and the system is designed to cope with this. It makes me think that doubling the present setting to 0.25 Hz/s would allow the system to function, but the problem then becomes "with what size of islanded section of the grid would we then fail to detect the problem?"

The problem could subsequently become somewhat different as a small island of high inertia generators may then be more resilient to frequency changes than a much larger island of low inertia generators.

Alasdair

John,

Very well said. The obvious conclusion that I see is that the setting of the RoCoF should be re-evaluated. Having spent most of my career dealing with ships I am aware of the frequency transients that occur when large loads are switched and the standards (e.g. IEC 60092, BS8450) and the Class Society Rules (e.g. LR, DNV, ABS, etc.) allow a 5% permanent deviation and a 10% transient deviation with a recovery time of 5 seconds, so obviously a 10% deviation has a minimum RoCoF of 2.0 Hz/s (from the initial excursion beyond the permitted 5% deviation down to 10% then back up to the permitted 5%). In reality the rate of change is much faster on the way down than during the recovery and so is probably around 10 Hz/s since the load switched is probably a relatively large percentage of the generating capacity (say 10%) and the system is designed to cope with this. It makes me think that doubling the present setting to 0.25 Hz/s would allow the system to function, but the problem then becomes "with what size of islanded section of the grid would we then fail to detect the problem?"

The problem could subsequently become somewhat different as a small island of high inertia generators may then be more resilient to frequency changes than a much larger island of low inertia generators.

Alasdair