PRINCETON, N.J., Nov. 29, 2000–The North American Electric Reliability Council (NERC) says there will be sufficient electricity resources to meet winter demand despite an expected 3% increase in peak demand compared to last winter.
But NERC also warned that unanticipated equipment problems and extreme weather could combine to produce demands that exceed generation margins and transmission capability.
NERC points to parts of East Central Area Reliability Coordination Agreement (ECAR) and the Pacific Northwest as potential trouble spots this winter. Despite two transmission lines being out of service, New York�s electricity system is expected to be adequate barring unusually cold weather.
Natural gas supplies will continue to be tight, driving prices up. So far, gas prices have tripled over the past 18 months. With prices rising, NERC suggests that some industrial gas users may reduce consumption, freeing more gas for use in residential heating and electricity production. Electricity production that consumes 28% of the total gas demand is usually the first to be cut off should gas supplies become scarce. The danger of natural gas curtailments to the power sector run highest in Southern California, NERC says.
NERC posted �available capacity margins� in the range of 20% to 37% for most of the operating regions and power pools. The exceptions to this estimate were Rocky Mountain in the Western Systems Coordinating Council, or WSCC, which had 17.4% capacity margin and New York, an operating region of the Northeast Power Coordinating Council or NPCC, with 16.5%. The available capacity margin for the entire country averages 30%.
The available capacity margin is defined as the amount of capacity above planned peak system demand available to provide for scheduled maintenance, emergency outages, system operating requirements or unforeseen electricity demand. A more stringent measure of reliability is reserve margin expressed as a percentage of total capability. Reserve margin is the amount of unused available capability that can be applied to the system within 10 minutes at peak load.
The California Independent System Operator estimated that the reserve margin last summer in that state fell into the single digits. And most experts put the average reserve margin in the US at about 15%.
NERC does express some concern about electric reliability and the transmission system in (ECAR), should severe weather hit the region.
�There is a small possibility that severe weather (abnormally cold), unexpectedly low generation availability, limitations on gas supplies for electric generation, and the unavailability of power from outside the region could make it necessary to curtail additional demand beyond interruptible demands,� NERC says in its report.
The transmission system could become constrained due to generation dispatch or power transfers into and across the region. With constraints certain operating procedures and �limitations� must be enforced to maintain the system security, NERC says. If not, uncontrolled area-wide black outs could occur.
One such procedure could be to curtail or limit west-to-east transfers to ensure adequate reliability. Other procedures must be employed to limit excessive power transfers through American Electric Power Co.�s southeastern transmission system until a new line is completed.
NERC forecasts peak demand this winter in New York to be less than 1% above the all-time winter peak of 24,051 Mw which occurred last year. Installed capacity is 35,636 Mw. Scheduled outages sum to 3,918 Mw, unplanned outages estimated at 4,811 Mw and operating reserve requirement of 1,800 Mw. This gives New York a net margin of 1,207 Mw.
Two lines are out of service that could impact local reliability, NERC says. The Hudson-Farragut 345 kV circuit is out of service because of a transformer failure. Replacement is expected in middle of February 2001. Another transformer at Goethals in series with the PSE&G-ConEdison Linden-Goethals 230kV interconnection failed because of an internal fault. Replacement is not expected until June 2001.
Both of these lines out could cause a reduction of about 150 Mw of imported power.
�The New York metropolitan demand centers are summer peaking. (The line outages) this should not pose a significant reliability risk,� NERC says.
The projected capacity margins in this region are adequate and reliability will be adequate except if several portions of this region peak at the same time.
�Public appeals to reduce electricity consumption and other measures may be instituted as necessary to ensure adequate operating reserves,� NERC says.
Transmission of power to the Pacific Northwest from California could be limited during times of extreme cold weather. Natural gas limitations during cold weather could also mean significant generation reductions and electricity service limitations during natural gas curtailment conditions.
In the Pacific Northwest, NERC is warning that the Puget Sound area in Northwestern Washington could have voltage stability problems. Studies indicate that this area is at highest risk of an �underfrequency event� during light demand hours in the winter coincident with imports from Montana, Idaho and California. To protect against this, the area has designed and will implement a load shedding (curtailment) program.