EMT Studies and Models for National Grid ESO

For those of you that are not that involved in Grid Studies, National Grid ESO has recently published a guidance note on the need for EMT studies for generation connected plant. This requirement is off the back of the GC0141 modification, that followed the August 2019 blackout, and is aimed to help define the performance of generator modules more accurately – specifically during faults, where issues like PLL behaviour and FRT abilities might not be correctly represented in an RMS simulation.

The document is pretty short, and isn’t too wordy, so if you are interested in system studies, or have a need for Grid Code studies its worth a read.

The short version is that we now have to prepare and submit an EMT model for the system in PSCAD for NG ESO to use and verify.

For Inverter based generation (Solar, Storage and most Wind) the requirements are not too bad, as although a detailed model is still required. The chances are that the equipment suppliers will already have a detailed model of the Inverter and the PPC.

For synchronous based generation, the situation looks a bit more complex. It requires that the following is included:
1) Models of the mechanical masses and the associated multi shaft mass data and torsional interactions
2) Models of the governor, Exciter / AVR, UEL, OEL and other associated control systems
3) Models for all of the protection systems associated with balanced and unbalanced faults

The modelling for inverter based resources looks like it will be ok, but this seems like a massive burden for small generators that fall in the 50MW+ category, and especially for any generators in the 30MW+ category for Southern Scotland or 10MW+ category in Northern Scotland.

If you are interested in how Aurora can help with PSCAD modelling and simulation techniques please get in touch.