SQSS

The Security and Quality of Supply Standard (SQSS) sets the criteria for planning and operating the GB transmission system. It defines the minimum levels of redundancy, generation adequacy, and demand security that the system must meet. The standard applies to NESO and the three transmission owners (National Grid, SSEN Transmission, SP Transmission). NESO administers the code.

The modification process

Anyone can propose an SQSS modification. Once raised, it goes to the SQSS Review Panel, which assigns it to a Workgroup of technical experts. The Workgroup develops the solution and produces a report. NESO then runs a Code Administrator Consultation (CAC) so all affected parties can respond. After consultation, a Final Modification Report goes to the Panel, which votes and recommends to Ofgem. Ofgem makes the final decision unless the modification qualifies as Self-Governance, in which case the Panel decides.

Key concepts

• Deterministic vs probabilistic planning standards. The SQSS traditionally uses deterministic criteria (fixed redundancy levels) but is evolving towards probabilistic approaches that account for the changing generation mix.
• Self-Governance applies when a modification will not materially affect consumers, competition, or system security. The Panel decides; parties can appeal within 15 working days.
• Cross-code impact means the modification affects other industry codes (Grid Code, CUSC, STC). When this happens, the codes must be changed in coordination.