Analysis of transmission loss model in New Zealand Electricity Market dispatch

A 3-segment piece-wise linear model is used in New Zealand Electricity Market dispatch for transmission loss calculation. Although the loss model delivers efficient software performance, the loss linearisation introduces small fraction of modelling error to be multiplied in the wholesale market settlement. This paper revisits the quadratic loss model linearisation in the context of market scheduling and dispatch, and then analyses the effect of loss modelling on economic dispatch using the IEEE 30-bus network. GAMS and MATPOWER are used in conjunction for linear programming and load flow analysis respectively. The results show that loss modelling error has no effect on individual nodal price variation, and its impact on market settlement becomes not negligible only when marginal generator is affected during high system loading.