D. F. Shankle

Field Measurement of Switching Surges on Unterminated 345-Kv Transmisson Lines

Field measurements are presented for switching surge line-to-ground voltages at both bus and receiving ends of unterminated 345-kv transmission lines of intermediate length, when energizing and re-energizing. Varied and representative configurations were studied. Effects of source configuration and breaker-pole closing sequence and prestriking are demonstrated. An estimate of overvoltage probability is attempted as well as a rationalized description of waveforms. Comparison tests on 138-kv lines were conducted, and data presented therefrom.

Prevention of Covered Conductor Burndown on Distribution Circuits-Arcing Protection Devices

The mechanism of covered conductor burndown is discussed in light of experience by the Pennsylvania Power and Light Company (PP&L) on 12-kV distribution circuits. A summary of laboratory test results is given to allow extension of this work to other distribution circuits. Details and early field experience are included on the Arcing Protection Device (APD), selected in an earlier study1 as the superior burndown prevention technique.

Field Measurement of 345-Kv Lightning Arrester Switching Surge Perrormance

The purpose of this paper is to present lightning arrester switching surge voltages and currents, measured during a field test program on a 345-kv system. Surges were produced by energization of a transformer-terminated line and by ultra-high-speed re-energization (UHSR) of arrester-terminated lines. Arrester-sparkover levels were 1.1 to 1.7 pu (per unit) of arrester rating, and arrester follow-current peaks were 135 to 940 amperes.

Field Measurement or Switching Surges as Modified by Unloaded 345-Kv Transformers

This paper presents results and analyses of extensive field tests to determine how unloaded transformers affect switching surge waveform and magnitude when energizing and de-energizing intermediate-length lines. Particular emphasis is placed on transformer-terminated lines. Switching of transformer-tapped lines and low-side switching of combined autotransformer and connecting high-side line are discussed, and the results include data from tests on both 345-kv and 138-kv systems.

The Apple Grove 750-kV Project- Equipment Design and Instrumentation

The Apple Grove 750-kV project, jointly sponsored by American Electric Power Service Corporation and Westinghouse Electric Corporation, with six other participating companies, was designed to provide data on corona loss and radio influence performance of conductors at a nominal voltage of 750 kV and to determine the technical and economic feasibility of transmitting power at this extra-high-voltage. The project also incorporates facilities for studying conductor configuration, insulator assemblies, spacers, connectors, splices, hardware, and steel structures. Operating experience has been gained on a 750-kV transformer, lightning arresters, coupling capacitors, and line traps, as well as on a typical 500-kV line design. This paper describes equipment design, instrumentation, and special project features, such as the determination of conductor performance on a statistical basis by the use of simultaneous comparison under the same environmental conditions.

Surge Protection for Pipeline Motors

Recent field tests on motors in service on pipelines and powerhouse systems have shown that the switching surge voltage appearing at the motor terminals during initial energization for starting frequently reach magnitudes approaching 2.0 per unit normal crest line-to-ground operating voltage with time-to-crest as short as 0.2 As. This is more severe than normally believed and may endanger turn-to-turn insulation.

Incremental Voltage Uprating of Transmission Lines

Many electric utilities face the problem of expanding transmission systems where new transmission line right-of-way (ROW) is increasingly more costly and difficult to obtain. One alternative is to uprate the voltage of lines on existing ROW to obtain increased transmission capacity. This paper discusses the technical and economic considerations of incrementally uprating the voltage of existing lines. Cost comparisons are made with building new lines on new ROW. There is a broad range of ROW costs and system transmission requirements where voltage uprating of existing transmission lines may be economically attractive.

The Apple Grove 750-kV Project- 500-kV Switching Surge and Line Flashover Tests

Rational design of extra-high-voltage systems depends on analytic studies to predict switching surge overvoltage magnitude and probability, and on laboratory tests for tower system switching surge withstand capability. Laboratory tests have been confined to ideal waveforms applied to single window configurations. Correlation with flashover performance of a typical 3-phase installation exposed to actual switching surge waveforms is attempted. The influence of interphase coupling and multiple circuit breaker operations in promoting multiphase flashover, which may curtail system performance margins, is also studied.