Performance of uprated substations in contaminated environments

Uprated substations have proven to be a viable economic alternative to rebuilding in order to increase power system capacity. The key economic factor in uprated designs is the use of lower than traditional insulation margins in high voltage substations. The experience of these uprated substations has been good and insulation design procedures for uprated substations have been developed to show other engineers how to take advantage of this design alternative. While these design procedures and other publications including the results of actual tests have given ample evidence of the success of the uprated designs, it has been noted that several areas need more study and testing. Among those areas which need further study are the effects of the dynamic forces caused by higher fault currents in the uprated substations and the ability of the reduced creepage distances of the uprated design to withstand pollution severity. This study covers the pollution severity issue by examining the results of flashover tests on the uprated substation insulators under various contamination conditions. The tests, which were done at the EPRI Power Deliver Center at Lenox, USA, are believed to be the only flashover tests ever conducted with uprated insulators. As might be expected, the uprated design is shown to be very sensitive to pollution severity. Sites chosen for uprating should include a pollution severity assessment as part of the design review.