[paulmac_ie]

We control a mixture of loads, but for Fast Frequency Response (FFR), it's mainly compressor/ motors, with the occassional mains breaker thrown in. Large cement factories, refrigeration companies etc.

As for how we control them so quickly, it's usually via a direct connection to a breaker of some description, or where there's a SCADA system that can trip out the loads in the required time frames. Before the site can participate in these services, we perform extensive testing to ensure they meet the required time constraints.

Our system monitors the grid voltage and current at 8 kHz, and we down sample that to 50 Hz (average grid frequency). We can detect a frequency event across 3 phases within 60 milliseconds. (We check all three phases for multiple cycles to reduce any false positives.)

When we trip out the loads, production stops. We'll notify the client why their loads have been turned off, but the SMS message will usually arrive a few seconds after the trip.

The clients that participate in these services get paid quite well to make their loads available and they're aware of the process. They agree to turn off demand without notice when there's a frequency event.

It's not suitable for every site. We work quite a lot with pharma companies for "regular" demand response, but very few can do FFR. Shutting down a pharma plant with no notice can cost a lot of money in wasted product and down time as they clear the wasted product off the production lines.