Which document outlines the rules ensuring the safe operation of the transmission system?

The Grid Code is a critical document that outlines the necessary rules and standards for the safe and reliable operation of the electricity transmission system. It serves as a framework that provides guidance on various aspects such as operational procedures, technical requirements, and safety protocols. This ensures that all participants in the electricity market operate within defined limits to maintain system stability and integrity.

Specifically, the Grid Code addresses how generation, transmission, and distribution entities must coordinate their activities to manage the flow of electricity effectively and mitigate risks. By adhering to these rules, operators can ensure that the transmission network operates efficiently while minimizing the likelihood of failures or disturbances in the power supply.

Other options, while relevant in a broader context, do not serve the same primary function as the Grid Code. For instance, a Generation Schedule pertains to the planning and timing of electricity generation rather than operational standards. Good Industry Practice refers to generally accepted practices but does not constitute a formal set of rules for operation. Frequency Variation relates to specific operational measures concerning the frequency of electricity supply but does not encompass the comprehensive safety and operational standards provided by the Grid Code.