Study on Trade Benefits for SAPP Electricity Market and Exploitation of Available Transfer Capability of Interconnected Inter-Utility Power Systems

A. Obok Opok and G.O. Anderson (Botswana)


SAPP, Trade Benefits, Available Transfer Capability


Available Transfer Capability is a measure of the ability of interconnected electric systems to reliably move or transfer electric power from one area to another area by way of transmission lines between those areas under specified system conditions. The area in the context of this paper refers to configuration of generating stations, connecting transmission lines that define an electric system for a member utility forming the Southern African Power Pool (SAPP). The overall goal of this study is to determine the on-line Available Transfer Capability (ATC) of tie-lines between control areas of interconnected transmission systems of utilities forming the Southern African Power Pool subject to static as well as dynamic security constraints of credible contingencies such as line thermal limits, bus voltage limits, steady state stability limits, and transient stability limits; the first two being referred to as the soft limits, while the last two are the hard limits. The approach proposed for the study will take into account the non linear nature of interconnected electric systems so that the determination of ATCs between utilities, which form the control areas, will depend on the operating conditions of the interconnected systems and binding constraints. The operating conditions will therefore be defined in different time frames by the different load demands, network configuration, and different generation dispatches and the scheduled power transfers among the utilities participating in the SAPP electricity market. The determination of ATC will be contingent upon key constraints comprising: network configuration of utility power systems; systems capability to ride through dynamic power swings; and ability of systems to operate within emergency ratings.

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