Operational Constraints

Dispatch is when the control centres in EirGrid and SONI send instructions to:

These instructions are about their times, fuel, manner of operation or output.

Dispatch Balancing Costs are payments related to how generators are instructed. They include:

The Transmission System Operators are responsible for forecasting and managing Dispatch Balancing Costs.

The costs are recovered through the Imperfections Charge. It also recovers make whole payments and the net cost of energy imbalances. SEMO levies this charge on suppliers in the Single Electricity Market (SEM).

The Transmission Operators make sure we have a secure power in real time. At times, they may have to dispatch or call in some power generators differently from the wholesale power market schedule. This prevents overloads and maintains enough generation reserve. It may also happen because of generator testing.

When power stations run differently to the market schedule, it is called a “constraint”. Constraint payments account for the difference between the market schedule and what actually happened. They keep generators financially neutral. This is subject to the Trading and Settlement Code and Firm Access.

Generators can be constrained:

There is always an overall net cost to the system associated with constraints.

The market schedule will not always be technically feasible. Mathematical limitations, approximations and assumptions all play a part in the schedule. It can take longer for power stations to increase output and link up with the power system.

All dispatchable generation must follow instructions from the control centres within practical limits. This ensures the safe, secure operation of the power system. Failure to do so leads to increased costs or major system problems.  

The Uninstructed Imbalance Payments mechanism gives economic signals that ensure dispatchable generation follows its instructions. This is set out in the Trading and Settlement code.

The level of firm financial access available in the transmission network for a generator is know as its Firm Access Quantity. Firm financial access means that if a generator is constrained on or off, it is eligible for compensation. The following report details of the methodology for firm access review.  

See our Publications section for the firm access quantity results of previous projects.

ATRs are new or upgraded transmission infrastructure projects. They are associated with a generation project and must be complete to release a generation project’s FAQ allocation.

Since October 2022 ATR updates are contained in our Network Delivery Portfolio (NDP). The NDP includes progress updates on our work to develop the power system.

See our Publications section for previous ATRs.
 

SCRs are important in connecting a generator. They refer to transmission infrastructure or equipment which needs to be replaced before the connection happens. As of 2017, all SCRs are now complete.

See our Publications section for previous SCRs.