In times of extreme market stress, AEMO can declare to temporarily suspend the spot market. In this situation, bidding and dispatch continues where possible, but AEMO issues dispatch instructions based on what they believe will be the most practical. Spot price is set based on a Market Suspension Pricing Schedule which is published weekly, 2 weeks in advance. The schedule is region specific and sets half-hour prices for business/non-business days based on a 28-day average for that specific region, day type, and time period (with 48 half hour periods in one day), with resultant prices then capped at $300/MWh.
Please contact our office if you would like any further information.