To facilitate both generation and retailing to have an open access to the transmission grid for trading electricity, a real time procedure is proposed. The line flows for an operation are assumed to be available from PMU and WAM validated state estimation. Power tracing determines different transactions to supply a retailer's demand, losses related to each transaction, extent of use each transaction makes of a transmission circuit and its associated losses. A generalized quadratic form learns relationships between a retailer's demand and, (i) a generation's contribution to it at a point of receipt, (ii) losses in a transaction, (iii) share of a transaction in a line, (iv) its associated losses, through learning coefficients. The procedure then predicts a generator's contribution to a retailer's demand at the point of receipt, power loss for the transaction, share of transactions in a line at the retail end and its associated line losses, for an oncoming operating scenario. © 2010 John Wiley & Sons, Ltd.