Services

A. Plant/Substation Grounding and Lightning Studies

B. Mitigation of AC Interference from Electric Power Systems

Grounding study performed on 230 kV/66 kV station, including detailed modeling of station (buried and overhead structures), nearby gas facility, gas pipelines, and 230 kV towers with overhead ground wires. Soil resistivity interpretation, ground impedance interpretation, station safety study and transferred potential analysis. Both frozen and non-frozen soil conditions studied. Simulation of ground impedance test, at 70 Hz and 1 kHz.

Interference mitigation study involving proposed 27-mile 115 kV transmission line and parallel telephone cables. Study included comparing computer model predictions and measured induced voltages associated with 34.5 kV collector lines from wind farms, running parallel to telephone cables. Excellent agreement was obtained. Effective mitigation for influence of 115 kV line was designed.

Study of mitigation methods to reduce neutral-to-earth voltages induced in 34.5 kV distribution underbuild (length of 3400 ft) and 12 kV buried distribution cable (parallel length of 3.4 miles), along 345 kV/138 kV transmission line.

This and the two following studies were undertaken in order to investigate methods to reduce undesirable voltages that could be induced in distribution neutral conductors by parallel transmission lines. The Jefferson project involved a planned 16-mile 138 kV transmission line, with distribution circuits running parallel to it for a total distance of approximately 6.5 miles. An extensive parametric analysis was carried out in order to investigate the effects of shield wire interruptions, continuous counterpoise, separation distance between circuits, phasing, phase unbalance, ground resistances, use of buried distribution feeder versus underbuild, changes in distribution neutral size, transmission line cross-sectional configuration, installation of a supplementary underbuild shield wire and bonding of a buried cable’s concentric neutral to the transmission line shield wire.

A 1-mile underbuilt section of a distribution feeder neutral was instrumented and approximately voltages and currents measured for 52 different energization and connection configurations, such as the following: with the transmission line energized and de-energized; with the overhead distribution feeder in service and with it replaced by a buried feeder; with the customer neutrals isolated and connected to the primary neutral; with the feeder neutral isolated and connected to the remainder of the distribution system; with the neutral connected to the static wire by means of a temporary jumper at each end of the feeder and without the jumper; with the transmission shield wire interrupted at each end of the feeder and continuous. Good agreement was obtained between the computer model and the field data.

A 138 kV transmission line was energized with both zero and positive sequence 65 Hz currents and computer model predictions of induced neutral current and neutral-to-earth voltage were compared with those measured with a dynamic signal analyzer. Given the urban environment and unknown customer grounding, computer model predictions matched measured data quite well. New methods of measuring steel pole ground resistances were also tested.

This AC interference mitigation study involved an 8.8-mile, double-circuit, 115 kV, buried, solid dielectric cable line running parallel to an electrified railroad, gas pipelines, and water pipes. SES’s mandate was to investigate the electromagnetic interference caused by the proposed 115-kV underground cables during load and fault conditions and to design appropriate corrective measures. By building a comprehensive electromagnetic interference model, including the mitigative influence of metallic infrastructure in the surrounding suburban area, SES demonstrated that no corrective were required.

This project involved the computer modeling of approximately 30.4 miles of new and reconstructed 345 kV and 115 kV lines, for the most part sited within existing transmission corridors or public roadways. The new 345 kV transmission line runs roughly parallel to existing railroad tracks. The objective of the study was to design any required corrective measures due to power frequency transferred voltage and current levels during fault and load conditions that could potentially interfere with the railroad signaling, communications, and grade crossing equipment, or represent a direct electrical safety concern. As part of this study, several efficient, economical and non-intrusive mitigation techniques were identified that significantly reduce interference levels caused by high voltage transmission lines.

This electromagnetic interference study involved new 345 kV transmission lines running a total length of 69 miles, including an underground cable section of about 23 miles. Of concern was exposure of a railroad, for a total length of about 13 miles, and three gas pipelines, for a total length of 8 miles. It was demonstrated that no mitigation was required along the exposure to the underground cable, nor were interference levels excessive during peak load conditions along the overhead line. Cost-effective, non-intrusive mitigation was designed to address fault conditions on the overhead line.

Modeling, field testing and mitigation of electromagnetic interactions between 230 kV and 21 kV circuits and buried recycled water pipeline. High levels of third harmonics in the 21 kV distribution circuits resulted in excessive induced voltages in a coated water pipeline running parallel to these lines for a distance of 2 miles. Fault conditions were also studied. Field testing confirmed computer model predictions, which minimized mitigation requirements.

Project in collaboration with Corrpro Companies to study the influence of the proposed Northeast Reliability Interconnect (NRI) 345 kV transmission line on the existing Maritimes & Northeast (M&N) pipeline, throughout the proposed joint-use corridor, known as the “Consolidated Corridor Re-Route,” which runs for a distance of approximately 86 miles, from Orrington Substation, in the State of Maine, to the Canadian Border, near Baileyville, Maine. The mandate of the authors was to create detailed computer models of the interacting utilities and explore, in a rapid and approximate manner, by what practical means voltages transferred to the pipeline could be maintained within satisfactory limits, during anticipated worst case steady state and short-circuit conditions. This was achieved by creating a custom, automated version of the Right-of-Way Pro software package.

Study the influence of two 69 kV and two 230 kV transmission lines on the proposed raw water main running parallel to these circuits for approximately 2 miles between the Eastern Regional Water Supply Facility (ERWSF) and the ECON Water Treatment Plant, in Orange County, Florida. SES’s mandate was to provide conceptual designs of corrective measures, if any were required, such as to limit pipe-to-soil voltages to acceptable levels along the pipeline, located within the Progress Energy Corporation transmission line easement.