An interesting story...
WECC Joint OC/PCC/MIC Meeting
Merrill Schultz Comments on
The History of the 5%/7% Contingency Reserve
Don Badley, NWPP Coordination Group, asked me to drop by and recount the history of the development of the 5%/7% Contingency Reserve criterion in WSCC. I don’t know why he did that – but I’m here. I explained to Don that I had, when I retired five years ago, given away or thrown away virtually all my files. Thus, I’d have to tell the story completely from memory. That’s OK, he said. On the other hand, I told him that, like most guys my age, my memory of discussions that took place more than 35 years ago is crystal clear. Frequently wrong – but absolutely clear. Despite that, I’m here.
Time for history…
Starting in the mid-60s, big things were happening in the electrical West.
Virtually all at once, the electrically isolated areas (1) the Pacific Northwest, (2) the
In each case, operators, who had long looked upon their colleagues in neighboring, but so far blissfully unconnected, areas either as clumsy Neanderthals or as insufferably arrogant and prissy aristocrats, now had to contemplate being shackled together forever, like those fugitives from the chain-gang in the movie. It was like the ultimate reality show – exciting, but scary as hell.
A succession of operations committees was formed in the years before the establishment of WSCC. When WSCC was begun in ’66 or ’67, the then existing Western Operations Committee was absorbed into the new organization as WSCC-OC.
Of course, WSCC-OC formed a Reliability Criteria for System Operations Working Group, and it, in turn, spawned an Operating Reserve Task Force. The Task Force comprised four people – Reed Canady, SCE; Bill Williams, SRP; Ab Watts, USBR; and I, NWPP Coordination Group.
The NWPP, which had been in existence since 1942, already had reliability criteria, as did the newly established CA Power Pool. AZ-NM, by virtue of the planning for 4-Corners and Navajo Plants, subscribed to the CA Criteria.
The negotiations rumbled on for many months, with Mr. Canady and me as the main protagonists
The NWPP’s Criteria defined the equivalent of Contingency Reserve to be 5% of load, all of which could be in the form of interruptible load or non-spinning generation, but it had to be realizable with five minutes to qualify
The CA Criteria defined the similar thing to be the larger of the biggest single contingency or 7% of load, all as spinning generator capacity. I don’t recall that there was any time limit for its pickup – if it was spinning, it was spinning reserve.
I don’t know the basis for the CA Power Pool’s 7%, and what I believe to be the basis for the PNW’s five percent is irrelevant to Operating Reserve.
Mr. Canady was adamant in rejecting interruptible load as Operating Reserve; it is clearly not automatically responsive to system contingencies. My biggest member utility, Bonneville Power Admin, was equally adamant about keeping it in – since interruptibility was seen as a contribution of value by the aluminum smelters and, therefore, was BPA’s justification for continuing to serve those loads
For the same lack-of-response reason, Mr. Canady would not accept shut-down capacity as spinning reserve
Likewise, the respective Pools were stubborn about moving off their chosen percentages, even though no one could explain, with rigor, how they were arrived at. Mr. Canady thought 5% was clearly “too low”. I rejoined that, applied to the NW, it was really much more conservative than the 7%, applied to CA. The largest contingency in the NW at that time was a GCL unit, at 125 Mw less than a half of one percent. The first contingency in CA was much larger, percentage-wise. Furthermore, the NW was almost totally hydro – hydro units could be started from dead-stop, synchronized and loaded within the five-minute criterion. Thermal units, constituting most of CA’s generation, required hours, in most cases, to start up and load
The arguments raged on for months
I believe it was Mr. Canady who finally proposed the diplomatic finesse: Contingency Reserve would be 5% hydro and 7% thermal. Thus, the NW would retain its 5% and CA would keep its 7%.
And I think it was I who reciprocated by proposing that, of the Contingency Reserve, a portion must be true spinning reserve, responsive to frequency deviations. That portion would be equal to one-and-a-half times the control area’s frequency bias, more or less half the Contingency Reserve – the rest could be interruptible load or anything else that can be activated in ten minutes.
The logic, or rationale, was that there is a basic amount of reserve capacity that must be provided to allow recovery to schedule within the ten-minute period, a portion of which must be spinning and responsive to keep the system operating smoothly and close to schedule.
We congratulated each other for our innovation and reasonableness and disbanded.
Now you know the truth. And you are shocked!! Shocked!! The actual origin of the five- and seven-percent figures is undocumented – probably, their adoption was largely based on what other pools were doing, but I can guarantee that no relevant, rigorous analysis was involved. Their application, respectively, to hydro and thermal has no basis in objective analysis of the characteristics of those kinds of generation – the numbers were established to smooth over what could have been endless debate between the two biggest pools in WSCC. Similarly, the split between spinning and non-spinning components of Contingency Reserve was adopted as a compromise between those same pools.
Does this lack of rigor matter to system reliability? No. I maintain that Operating Reserve is an issue almost totally of equity, NOT reliability. And equity is whatever the parties decide is equitable. I do believe that monitoring and compliance is very important; failure to provide agreed-upon reserve must not be allowed to become pervasive. Then it might, indeed, become a reliability issue.