CROSS BORDER TRADING

摘要

Electric Energy utilities engage in cross border import and export of electricity due to various factors which prompt cross border trading in electric energy. Historic reasons often include the need to supply specific loads in one country from a neighbouring country who happen to have surplus energy. The need to share resources in a given region and optimise utilisation of resources for the benefits of neighbouring countries also promotes cross border electric energy trading. Another factor which propels cross border trading is a reduction of investment costs and enhancing of system reliability through the equitable sharing of resources (economies of scale) and co-ordinated operation of the power system. The generation mix (differences in structures of generation systems) is also a major factor influencing cross border trading. Nowadays, the liberalisation in the Electricity Supply Industry and regional integration is a major driving factor in the development of regional Electricity Markets hence cross border trading is on the increase. Cross border trading entails Interconnections of power networks in neighbouring countries and as the regional interconnections increase, the operations of the power system becomes more complex and challenging which pushes for automation of control systems. Interconnectors also give rise to a number of technical issues such as system stability and the question of transfer limits. The telecommunications aspect for both automated control and operation of the interconnected power system is essential to support cross border trading. Historically cross border electricity trading calls for bilateral commercial agreements among utilities in the form of Power Purchase Agreements on bilateral lines. The agreements may also have to encompass other members who provide services to the other two trading parties. Typically this service is transportation of the power from the Seller to the Buyer. New trends are developing with the introduction of regional power markets (power exchange). Competitive electricity trading rules are developed by members to facilitate cross boarder trading. Other commercial aspects are developed with cross border trading. These include management of system losses especially where a wheeler is involved, wheeling tariff for use of one's transmission infrastructure for transportation of power. Traditionally, the numerous arrangements for sale of electrical energy among countries using bilateral and tripartite contracts are becoming more complex and Power Pools were formed on co-operative lines. The impact of reforms in the electricity sector of member countries is the transformation of these co-operative Power Pools to competitive Power Pools where Electricity Markets are being established. The electricity market provides for cross border trading through long term bilateral contracts, Short Term bilateral contracts and spot trading. In order to ensure system security and reliability the modern trend is to introduce trade in ancillary services in the competitive market as well. The establishment of markets calls for open access on the transmission infrastructure to facilitate cross border trading. The main paper covers in detail the aspects of power trading, interconnections, Operational Aspects and Trading Agreements. References are made to the Southern African Power Pool (SAPP) in the form of study cases to illustrate various aspects of electricity trading.