5th Apr 2011

Mod_09_11: Explanatory Notes

SEMO Market Development

Intro

MSP Software does not model Loading Rates as operating range below Min Stable Generation not represented

Rather than ignoring the effect of Loading Rates, Ramp Rates are used instead as an approximation to limit the rate of change during Start Up and Shutdown

However, the descriptions of these limits in the Code is not consistent and needs to be aligned

Current Rules

Start-Up and Shutdown limits are described differently. We believe this was an unintentional drafting error.

AND option

One option is to adopt AND rule used for Shutdown in the case of Start Up

Other option is to adopt OR rule used for Start Up in the case of Shutdown

OR option

SEMO view

Ramp Rates (and Block Load) are used to approximate Loading Limits.

Min Stable Generation is only included to prevent a Unit being forced to operate below MSG as this would be infeasible.

Therefore, OR is most appropriate.

Shutdown should be changed from AND to OR to make Code internally consistent.

We believe this was a drafting error as Systems built this way already.

Mod_09_11 written on this basis