Managing South Australia’s Power System Under Non-Credible Contingencies with two AC Interconnectors

(SA) and New South Wales (NSW). The SA–NSW interconnector (SNI) provides a geographically diverse second AC connection into SA, complementing the existing Heywood

Interconnector (HIC).

This paper outlines the work undertaken by ElectraNet, the Transmission Network Service

Provider (TNSP) for SA together with Transgrid (TNSP for NSW), AEMO Victorian Planning

(System Planner for Victoria), AusNet (TNSP for Victoria), and AEMO as the system operator, to integrate the SNI into the National Electricity Market (NEM) while maintaining power system resilience for high-impact, low-probability events. The integration required extensive system studies as part of joint planning between the TNSPs, as well as the design, deployment, and commissioning of remedial action schemes (RAS) across three states. In addition to deploying RAS, existing under-frequency load shedding (UFLS) and over-frequency generation shedding (OFGS) schemes were modified. These actions were complemented by enhancements to operational management practices.

The work presented in this paper is broadly applicable in regions with low inertia and long or weak transmission connections. They also support integration of inverter-based generation

(IBR) and new transmission infrastructure into existing networks while maintaining system resiliency.