VIC1 experienced sustained negative pricing at approximately −$6.51/MWh for three consecutive intervals (18:25–18:35) on 18 August 2026, followed by a gradual recovery to near-zero prices. The negative pricing occurred during a period of high wind generation (3717.88 MW and 3516.35 MW across the region) combined with substantial brown coal generation (2705.88 MW), resulting in excess supply relative to demand.
The negative pricing was driven by binding constraints with material marginal values, most notably constraint F_T+LREG_0050 which exhibited marginal values around $20.36–$20.46/MWh during the negative price periods. The combination of high wind output, inflexible brown coal generation, and the binding constraint preventing further dispatch reductions created a supply-demand imbalance where the market clearing price fell to negative levels. The subsequent recovery to near-zero prices from 19:05 onwards indicates the constraint relaxation allowed the system to rebalance.
Causal analysis generated by gridIQ's synthesis model from live AEMO market data: dispatch prices, generation mix, interconnector flows and market notices in the interval surrounding the event.