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
Overvoltages and Harmonics on EHV Systems
Steady-state overvoltages can occur on EHV transmission systems during various system operating conditions. The voltage waveforms are characterized by a periodic waveform which may be distorted by harmonics if iron saturation of equipment on the lines occurs. This paper discusses the results of digital and transient network analyzer (Anacom) studies which analyzed system parameters with respect to their effect on harmonics in steady-state overvoltages. Special emphasis was focused on the factors influencing harmonic distortion of the steady-state voltages.
Overvoltages on the AEP 765-kV System
Overvoltages on the American Electric Power 765-kV transmission system and their influence on its design are studied. Overvoltage phenomena are defined and described during the transient, dynamic, and steady-state periods. The effect of these periods on equipment and means for their control are discussed. Examples of data important in arriving at final system design are given. Analytical tools used during the overvoltage studies are discussed and areas requiring further research are listed.