DWG – Dependable Capacity Kevin Harris, ColumbiaGrid TEPPC\Hydro Modeling Task Force - Chair

Overview GADS EFORd and SOF for Understanding Maintenance in GV – Risk of Scheduling Maintenance in PCM Dependable Capacity – Concept presented at WECC DWG on 2/13/2014 and GridView user group 10/19/2015 2

NERC GADS NERC GADS (Generation Availability Data System) EFORd: Equivalent Forced Outage Rate Demand – EFORd measures the probability that a unit will not meet its demand periods for generating requirements because of forced outages or deratings. SOF: Scheduled outage factor AF: Availability Factor 3 PW: Diablo & PV BW: Columbia GS

Understanding Maintenance in GV 4 A LOLP (Loss Of Load Probability) or equivalent method measures a systems ability reliably serve load – A commend criterial is 1 day in 10 years or probability of – LOLP ranges from Maintenance is scheduled when LOLP is low LOLP inputs: units rating, forced outage rate and served peak demand In GV outage rate are not considered for Hydro, and hourly shapes ( like Hydro, wind, solar), i.e. its perfect/firm capacity – As the penetration of Hydro, wind, and solar capacity increases LOLP drops to zero Existing PNW Supply (WA, OR, ID and MT): 24% dispatchable (13,610 MW), 61% Hydro (35,487 MW) and 13% renewable (8,662 MW)

Understanding Maintenance in GV 5 LOLP is calculated weekly based on inputted hourly loads – Maintenance is scheduled based on a nominal year (by season/monthly) Maintenance is preformed by regions which may not line up with actual operations – The use of a user define maintenance areas where areas and/or units can be assigned

Dependable Capacity Dependable capacity should be used instead of physical capacity when calculating LOLP for maintenance scheduling – Dependable capacity is used only for scheduling maintenance – Expected available capability during the peak hour – If an EFOR is not modeled some form of probability of exceedance should be applied for expected peak hour Dependable Capacity is: – For traditional thermal units this is the winter/summer rating – For Hydro dependable capacity is limited to the plants ability to serve load on a daily bases Dependable Hydro:= Min(Rating or [ROR (aMW) + (Gen – ROR (aMW)) * 2 (Equiv to 12 hours of op [24/12]) Example: 50% CF with 40% of generation used for base load (ROR): – min(100%, 20% [50%*40% ROR] + (50% - 20%) * 2):= min(100%, 80%):= 80% rating If 100% ROR formula results in dependable capacity equal to ROR capacity In an emergency full load capability can be achieved. – For Wind/Solar the expected capacity during the peak hour with a 90+% probability of exceedance Effective Load Carrying Capability (ELCC) California NQC 6

Dependable Hydro 7 Dependable Hydro capacity is limited by the available Hydro energy to serve load Dependable Hydro:=Min(Rating, ROR aMW + [Mo Gen – ROR aMW] * 2) Hydro gen in the fall cannot support full rating except for short periods of time Assuming 20,000 MW rating Dependable Cap in Sept is 12,000 MW, a 8,000 MW derate Including a ROR component decreases dependable capacity

Example PNW Dependable Capacity 8 Hydro and thermal maintenance patterns are not similar – They peak during different seasons Dependable capacity in June is 10,000 MW less than capability A 12,000 MW reduction in dependable capacity from Jun to Sep Sep dependable capacity is 30% lower than capability Dependable Capacity ST, CC, GT:= 100% Wind:= 0% Solar:= 0% Hydro:= Daily Sched Capability Min(Max, ROR + 2*[Gen-ROR]) Chart from 2/13/2014 DWG presentation

9 Kevin Harris (503)