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The Rules of the Grid: Transmission Policy and Motives Gehind It

Making sense of RTO Week, the mediation talks, and FERC's promised new rulemaking.
Fortnightly Magazine - December 2001

estimators basically provide a snapshot of the status of the electric system, including the distribution of generation and load, using a partial set of inputs to estimate the status of the entire system.

"The availability of a 'good' state estimator solution is very important. It is a key element in the PJM pricing structure, and a very desirable improvement for New York, which currently does not include state estimation results in their real-time operations, but instead uses [an] assumed distribution of load.

"My conclusion would be that the presence of a state estimator would contribute significantly to improving the ability to secure the reliability concerns that New York has expressed, as New York currently is unable to as accurately estimate the location of load, and thus power flows on its system in real time."

2. VOLTAGE AND FREQUENCY CONTROL. "This is another area where ... the PJM current practice ... would offer significant regional reliability benefits. ..

"Currently, PJM has procedurally integrated AC [alternating current] security runs on a 15-minute basis into its real-time dispatch. That means that operating limits and contingencies may be modified in the DC [direct current] characterization of the dispatch to reflect real-time AC limits.

"New York does not have this capability. Their AC security runs are done off line, and cannot be directly integrated into the real-time dispatch of the system. This means that not only does the New York system have to operate more conservatively, in terms of approaching operating limits and the full utilization of their system, they also face potential operating risks that may not be seen, or are only seen abruptly."

3. UNIT DISPATCH (DAY-AHEAD). "Both PJM and New York run a SCUC [security constrained, unit commitment model] program in the day-ahead market. The same would be true for the RNMC 3-M proposal. Both existing SCUCs attempt to find the lowest-bid cost set of generators that can reliably meet load and reserve requirements while honoring all relevant operating security requirements.

"The PJM and New York SCUC procedures ... both fully accommodate ... reliability requirements ... and would do so if either structure were applied to the other physical market. ... The models are very much the same. ...

"The 'scare factor' of reliability is raised repeatedly ... as a factor to oppose ... a single market. [But] there is absolutely no reason to assume there is any merit to these concerns.

"In New York City, there are a number of double contingencies, some of which are under the control of Con Ed, and not the ISO. These are the 'special' security conditions that New York suggests PJM ignores. The reality is that they are not ignored by PJM. [They] simply do not reflect current PJM operating contingencies with the PJM control area. ... There is no magic here ... just different inputs.

"If Con Ed or PECO for that matter has specific contingencies ... Con Ed and any other transmission owner would be free under the PJM system to establish all reasonable security requirements they feel are necessary."