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Capturing Distributed Benefits

Factoring customer-owned generation into forecasting, planning, and operations.

Fortnightly Magazine - August 2012

location, has allowed Con Edison to defer traditional, costly utility infrastructure investments. Notably, many of the new large CHP projects have faced technical challenges—such as equipment not operating as planned, leading to costly outages and high standby-rate backup charges. Until reliable operations are demonstrated, these aren’t included as a load reduction in load relief plans.

The criteria for capacity integration differ based on the contingency design of the area substation that feeds the network where the DG is located. For example, a substation with second-contingency design can include a reliable DG source as part of substation capability, as long as operating protocols are in place to back up the DG capacity. Protocols need to be in place by the summer the projected peak load exceeds the substation capability. The operating protocols would be called if the DG is out of service on a peak summer day in addition to having two substation transformers out of service. For first-contingency design substations, the same method applies, but the operating protocol must be in place assuming the DG is out of service as well as only one substation transformer. For networks with several independent DG installations Con Edison would review the diversity of DG installations to determine which should be included.

Taking a proactive approach to incorporating DG into company planning has yielded multiple operational benefits. Con Edison’s corporate long-range plans are now focused on examining cross-commodity synergies, and DG has been a natural focus for these efforts as it involves all three of the utility’s primary commodities—electric, gas, and steam. DG has been a central point for bringing these three divisions together to strategize the revenue and infrastructure implications of DG adoption. Gaining a better understanding of the costs and benefits of different approaches will help to ensure Con Edison can accommodate increased DG deployment and ensure revenue stability and positive rate impacts for customers.

Case Study: DG Delivery System Benefits

In one case in Manhattan, a customer served by a second-contingency design substation under a traditional load relief plan has for the past three years been running a 7.5 MW CHP generator during network peak periods, equipped with four-second-interval telemetry read at Con Edison’s control center. Analyzing the historical telemetry data has allowed engineers to comfortably rely on this DG capacity at the substation level, and thereby to defer future T&D load-relief efforts. In addressing the concern for assurance of capacity availability in factoring this particular generator into area load relief plans, the engineering team first set monitoring requirements on real-time interval data. The team ensured that working, reliable telemetry was in place for DG breaker status, output of kW and kVARs, as well as voltage, amperes, and power factor. This allows monitoring DG performance, including the coincidence of generator output with substation peak loads. This level of telemetry is already required under Con Edison specifications for new DG installations over 2 MW connected at medium-level voltage. This particular generator had more than two years of historical data that helped operators to understand the outage rate on weekdays during the summer period, average