Interconnector Watch

The dominant flow right now is VIC1-NSW1 (Vic–NSW interconnector) carrying 757.65 MW northward from Victoria into New South Wales, running at 64% of its 1,188.62 MW export limit — comfortably below capacity and not binding. This flow is consistent with Victoria's $67.16/MWh price sitting $11.84 below NSW's $79.00/MWh, with arbitrage driving generation surplus southward across the border. On the QNI (NSW1-QLD1), 133.27 MW is flowing southward from Queensland into NSW, at 75% of its current southward limit of 176.89 MW — again not binding, and directionally aligned with Queensland ($77.94/MWh) pricing marginally below NSW. Neither of the two main mainland north–south interconnectors is binding in this interval.

The most operationally significant constraint active today is the V-HYTR constraint set, invoked following an unplanned outage of the Tarrone–Heywood/APD 500 kV line in Victoria at 1152 hrs on 17 April (AEMO Market Notice 141109). This constraint set has equations covering V-SA, T-V-MNSP1, VIC1-NSW1, NSW1-QLD1, and V-S-MNSP1 on the left-hand side, meaning transfer capability across multiple interconnectors is derated relative to normal limits. Despite this, no interconnector is recorded as binding in the 06:00 AEST interval. The Heywood interconnector (V-SA) is flowing 236.81 MW westward from Victoria into South Australia and is sitting exactly at its import limit of -236.81 MW — technically at limit, though flagged as not binding in the dispatch solution. Traders should note that with the 500 kV Tarrone–Heywood line still out, V-SA's effective transfer capability remains reduced and any increase in SA demand or decrease in Victorian supply could push this link into a binding state.

Murraylink (V-S-MNSP1) carries 62.95 MW from Victoria into South Australia and is at its export limit of -62.95 MW, again flagged as non-binding — the limit itself appears to have been set to the current flow, suggesting the constraint set is holding it at this level rather than the link being freely dispatched. SA's $55.10/MWh is the lowest NEM price this interval, $12.06 below Victoria, which would ordinarily incentivise less westward flow; the combination of Heywood and Murraylink both at or near their westward limits under the V-HYTR derating is suppressing SA prices relative to what a fully unconstrained network would produce. Basslink (T-V-MNSP1) shows zero flow in both directions, sitting mid-range within its ±125 MW capability, while Tasmania prices at $88.16/MWh — the highest in the NEM — suggest the island is price-isolated from the mainland at this interval rather than exporting to arbitrage the spread. The DirectLink (N-Q-MNSP1) is also at zero flow. Today's key watch point is whether the Tarrone–Heywood outage is rectified: restoration would lift V-SA and Murraylink limits, ease the V-HYTR constraint set, and likely compress the SA–VIC price spread.