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
Insulation Levels for VEPCO 500-Kv Substation Equipment
A detailed study has been made of the Virginia Electric and Power Copmany (VEPCO) 500-kv transmission sytem to determine optimum insulation levels for the substation equipment. Results of this study depend on both economic and technical considerations. For the VEPCO system, a 70% arrester can be used at the generator step-up transformer locations, and a 75% will be required at step-down substations. Adequate impulse and switching surge margins permit a transformer BIL (basic impulse insulation level) of 1,300 kv to be used at all locations. The most practical circuit breaker BIL, consistent with good engineering practice and economy of application, is 1,550 kv.
Transmission Line Models for Switching Studies: Design Criteria II. Selection of Section Length, Model Design and Tests
A criterion is presented and evaluated for establishing the relation between section length of a transmission model and the desired accuracy over a frequency band. This criterion along with those established in a companion paperl are used to design a transmission line model. The details of the design are presented. Test results made on a newly constructed model are presented to establish the validity of the design criteria.