Program 1

Project 1 - Impulse Testing of Underground, Direct-Buried Cable

The goal of this project was to execute and analyze full-scale high voltage impulse tests on underground distribution cable. The system was composed of direct-buried bare concentric neutral cable, terminations, a rise pole and a short overhead line. The tests validated classical underground distribution system overvoltage protection theory, and included comparisons of SiC and ZnO arrester performance, comparisons of arrester placement, and mid-span voltage magnification due to taps.

Tagged: Equipment Testing/Evaluation, P1, Engineering Guidelines, P1-1, System Protection

Project 2 - Secondary Surge and Jacketed Cable Investigation

The objectives of this project were to: 1) determine the sensitivity of secondary surges with respect to circuit parameters, and 2) determine the magnitude of neutral-to-ground voltages on jacketed cables with and without counterpoise.

Full-scale impulse tests were conducted on jacketed cable and a parametric study was conducted to investigate secondary surges and currents as a function of transformer construction, triplex length, load variation and secondary arresters all with high resistance primary grounding. Also, a computer-based tutorial on underground distribution overvoltage protection was created.

Overvoltage protection application guidelines from the P1-1 and P1-2 test results were also summarized in a separate document.

Tagged: Equipment Testing/Evaluation, P1, Engineering Guidelines, P2-1, System Protection

Project 3 - Fast and Slow-Front Surges

The objective of this investigation was to assess the impact of fast-front current surges on jacketed cable systems using full-scale impulse tests. Items that were investigated include: 1) lead length effects, 2) cable jacket potentials, 3) counterpoise performance, and 4) multiple system ground performance.

Guidelines and recommendations for utilities were developed to help utilities improves system design and/or enhance understanding of underground systems during surges with short times to crest.

Tagged: Equipment Testing/Evaluation, P1, Engineering Guidelines, System Protection, P3-1