Fault Clearing Overvoltages on Long Transformer Terminated Lines
The results of Transient Network Analyzer (TNA) studies evaluating the feasibility of low-side switching long transformer terminated lines is reported. It is shown that overvoltages following line dropping and fault clearing can severely stress surge arresters and circuit brtakers exceeding capabilities specified in ANSI standards. These overvoltages are often not carefully considered in design studies, since the available literature on low-side switching of EHV transmission lines primarily deals with energizing the line and transformer.1,2,3,4
THEANALYSISAND PREDICTIONOF-HARMONIC RESONANTOVERVOLTAGESRESULTINGFROM LINEDROPPINGAND FAULTCLEARINGTRANSFORMER-TERMINATEDEHVLINES
An analyticalmethod to predictharmonic resonant overvoltages resultingfrom line dropping and fault clearing-transformer-terminated transmission lines ispresented.The method yield's close correlation to results of Transient Network Analyzer'(TNA) studies and actual fieldtests. Applicationof the techniq'ues described in' this paper will aid utility
Circuit-Breaker Field Testing at 87% of Line-To-Line Voltage
A 3-phase interrupting test on a circuit breaker is the most severe test to demonstrate the breaker's interrupting ability. To demonstrate the 3-phase interrupting capability on a single-pole test, the fundamental frequency recovery voltage must be equal to 87% of line-to-line voltage. Most power utilities find it difficult to obtain proper voltage for this type of field test. This paper describes the test equipment and method employed, and the principle involved, in obtaining a single-pole circuit-breaker test at 87% of line-to-line voltage of 34.5-kv circuit breakers, conducted by the Department of Water and Power (DW&P) of The City of Los Angeles.