Standby power generation under utility curtailment contract agreements

Many electric utilities in the United States offer large industrial and commercial customers power sales contracts which have attractive rates under a curtailment requirement. This curtailment requirement allows the utility to require the customer to reduce its power demand to a predetermined level within a specific time period. If the required curtailment is not achieved by the customer within the allocated time period, stiff financial penalties are usually enforced by the utility. The attractiveness of the contract rates usually is proportional to the amount of curtailment required. To take advantage of these attractive rates, a customer must be able to withstand the curtailment without supplemental generation or must add standby generation to meet its needs. Obviously, the cost of the curtailments to the customer should not exceed the economic benefits of reduced rates. This paper reviews the alternatives faced by a curtailment contract customer together with potential load-shedding and standby-generation system designs. An example of implementing a curtailment contract at an existing industrial facility is presented. The example facility. Boeing Helicopters, Philadelphia, PA, USA, required both load shedding and standby generation. The load-shedding scheme is fairly complex and is controlled by a programmable logic controller (PLC). The standby-generation and load-shedding systems for the example facility are examined in detail. Also, lessons learned from implementing the required modifications to the example facility are discussed