The International Conference on Large Electric Systems I-II. [antikvár]

PROCEEDINGS OF THE 21ST SESSION : 1966 NOTES ON THE SESSION I. — OBJEGTS AND METHODS OF CIGRÉ l.i. Objects of CIGrRÉ. — The statutory objects of CIGRÉ are to facilitate and promote the interchange of technical know-ledge and information between all countries in the field of elec-tricity generation and transmission at high voltages. Its activities are particularly concerned with : a. the electrical aspects of electricity generation; b. the construction and operation of substations and transformer stations and their associated equipment; c. the construction, insulation, and operation of high voltage electrical lines; d. the interconnection of systems and the operation and pro-tection of interconnected systems. REPORT 1. INTRODTJCTION. The rapid growth of electricity supply over the past two decades and the consequent increase in the unit rating of electrical plánt installed to meet this demand has focused attention on the high cost of circuit disconnections due to service faults. In Great Britain this has been estimated as ranging from L 10 000 to L 2 000 per day depending upon plánt merit and availability and, whilst advances in design and techniques of material utilisation has enabled the development of power system transformers toward ratings of 1000 MVA for use at voltages up to 750 kV, their security and efíicient operation is dependent upon the reliability of their acces-sories. Experience has shewn that accessory failure is responsible for a greater fault incidence than that due to service faults on the primary equipment. At 3ist March, 1965, the Central Electricity Generating Board for England and Wales had installed on its system a gross transformer capacity of 104,368 MVA, in 1746 units operating at voltages of 132 kV and above. In the last three years orders have been placed with British Manufacturers for a totál of one-hundred and fifty-eight, 400 kV transformers of various types of 3-phase units; twenty-six having double wound ratings of 570 or 600 MVA. Larger ratings are contemplated for the near future. Of necessity, priority has been given to design aspects of the primary equipment, research and development effort for this having provided a greater return in terms of transformer rating. Increasing attention is, however, now being directed to improvement in accessary design and application to ensure standards of reliability commensurate with the primary equipment. Among those accessories which poten-tially hazard security, the following have been selected for detailed study. Electrical connection entries. - These are generally condenser bushings. In Great Britain the re-entrant type of bushing has been adopted as a standard for 275 and 400 kV transformers. Whilst at first this design conferred somé advantages in minimising transformer tank sizes, with modern transformer constructions, the advantages of the re-entrant profilé seem now to be marginal.