ML&P proposes Railbelt power dispatch solution

Offers service to utilities to help make best use of available electricity generation facilities on the Railbelt transmission grid

Alan Bailey

Petroleum News

Anchorage electric utility Municipal Light & Power is offering power dispatch services to the other utilities on the Alaska Railbelt transmission grid, to evaluate the benefits to be gained from the most efficient use of power stations on the grid, James Trent, ML&P general manager, told the Regulatory Commission of Alaska on June 3. ML&P has implemented a state-of-the-art computer system for managing the dispatch of electrical power and is offering to use the system to help other utilities make optimum use of power generation facilities and to collect data on any resulting economic benefits, Trent told the commissioners. The proposed arrangement would last for one year, on a trial basis, at no cost to the utilities that sign up.

To date four of the five Railbelt utilities have concurred with implementing the proposed service, Trent said.

At issue is the question of what is referred to as “economic dispatch,” an arrangement whereby hour-by-hour power demand on an electricity grid is met by preferentially operating the lowest cost sources of energy.

Trent said that the computer system that ML&P is now using to manage its own economic dispatch is operating successfully throughout the Lower 48 and is also used in Europe. Under the proposed one-year program ML&P would use the system to provide utilities on a day-ahead basis the information that they need to decide which of their power generators to run, with the utilities retaining the ability to choose whether to follow the advice that the system provides. The system would then track the cost savings achieved, depending on the decisions that individual utilities make, Trent said. The system takes into account numerous economic factors, he said.

At the end of the one-year trial it would be possible to assess the effectiveness of the computer system in managing economic dispatch on the Railbelt grid, Trent said. The hope is that the arrangement would also enable the evaluation of actual cost savings from economic dispatch, thus providing data for evaluating future benefits to be gained from improving the way in which the power transmission grid is managed and operated.

Although, ideally, under an economic dispatch arrangement, maximum use of the most economic power source would always be used, in practice this ideal must be balanced against limitations in the transmission system’s capacity to carry power, and against the need to have some redundant power available to ensure the reliability of the power supply.

David LeVee, a power forecasting consultant, told the commissioners that the computer system that ML&P is using takes into account the various constraints in a power generation and transmission system when determining the optimum balance of power generation usage. It is possible to specify the constraints, so that the system can determine when transmission loads, for example, would hit the transmission limits, he said.

There has been a multi-year debate in Alaska over whether or how to change the manner in which the Railbelt transmission grid is managed and operated, to address the current grid’s shortcomings and ultimately facilitate economic dispatch. In the latest phase of this debate the state Legislature has tasked the commission with making a recommendation on whether management of the grid should be transferred to some form of independent operator.

Trent told the commissioners that, although ML&P has been actively involved in discussions over various models for the unified operation of the Railbelt grid, the utility has been unable to make an effective business case for adopting any of the models proposed. However, the implementation of economic dispatch is embedded in all proposals, he said. ML&P’s proposed arrangement would provide the opportunity for at least some economic savings from the more efficient use of Railbelt power generation, Trent told the commissioners.