A. Plant/Substation Grounding and Lightning Studies

1. Keewatinohk Converter Station Grounding Study

Project Outline:

Grounding study of 0.5 km x 0.5 km 230 kV AC / 500 kV DC converter station, connected to five 230 kV transmission lines and one 500 kV HVDC transmission line, in northern Manitoba. Used MultiFields software to simultaneously carry out fault current split calculation and grounding, accounting for inductive coupling between overhead lines and buswork in the station with grounding conductors, thus reducing computed touch and step voltages significantly. Induced currents in the soil were found to yield an apparent grid impedance with a capacitive reactance, due to very high deep soil resistivity and very low shallow to moderate soil resistivity. Optimized grounding performance, accounting for soil freezing down to 4.5 m, difficulty driving ground rods much deeper than 12 m, need to meet IEEE Standard 80 limits in certain areas without an insulating layer of crushed stone, saving millions of dollars.

2. Wildcat Point Generation Facility Gas Yard Grounding Study

Project Outline:

Grounding design study for gas yard adjacent to Wildcat Point Generation Facility. Included modeling of interactions of cathodic protection system of gas yard with adjacent 500 kV switchyard and other plant grounding and identified locations with peak leakage current densities.

3. Wildcat Point Generation Facility, Plant & Switchyard Grounding - Phases I and II

Project Outline:

Two-part grounding study, first to determine safety in area of plant being rebuilt, in the absence of grounding conductors, in the event of a 500 kV fault, and recommend required mitigation, next to evaluate the final conceptual design for the entire plant area, consisting of existing and new generation.

4. Napanee GS Grounding Study

Project Outline:

Short-circuit study, fault current split calculation and grounding recommendations for TransCanada Napanee Generating Station. Included modeling of interconnected and interacting grounding systems of two power plants and one major adjacent 500 kV / 230 kV transformer station, two major three-winding, three-phase auto-transformers, six 500 kV circuits, four 230 kV circuits, local generators, 4 remote generators, 3 remote transformer stations and equivalent transfer impedances between them. Study demonstrated that consideration of all interacting system components made it possible to meet grounding design criteria without any need for deep wells or additional remote grounding electrodes outside the generating station, as would otherwise have been required.

5. AEP Sorenson Substation Grounding Study

Project Outline:

Grounding study of 2,300 ft long 765 kV / 345 kV / 138 kV substation. Faults studied at multiple locations throughout station, accounting for circulating currents. Demonstrated potential savings on the order of $1 M with cost-effective mitigation approach.

6. Grounding Study for LCRA Ferguson Replacement Project

Project Outline:

Grounding study of a large power plant next to a lake. Studied grounding performance with and without supplementary grid in lake, using finite-volume soil structures to represent water, soil and rock. Modeled 138 kV transmission line system up to 39 miles away (11 circuits), in order to find worst case fault location and benefit as much as possible from fault current split provided by conductive shield wires.

7. LADWP HVDC Sea Electrode Study

Project Outline:

Study of the impact of an HVDC electrode in the sea and transferred potentials to nearby gas pipeline. The sensitivity of the results to the method used to represent the sea bed was examined: e.g., infinitely long sloped plane versus trapezoidal volumes.

8. BGE High Ridge Substation GIS Grounding Design and Substation Test & Analysis

Project Outline:

Study of the optimal method to ground a 230 kV GIS to the grounding system of an existing air-insulated substation. Included the modeling of the phase conductors and bus enclosures and associated inductive coupling and provided training in field testing of the substation: soil resistivity measurements, fall-of-potential test, touch and step voltage measurements.

9. Habshan-5 Utilities & Offsites: Grounding and Lightning Shielding Study

Project Outline:

Lightning shielding design study for utilities & offsites areas of 2 km x 2 km Habshan-5 gas development project. Grounding study as well for the entire plant, for 132 kV and 220 kV faults at the 4 high-voltage substations on site. Study also of resistance versus solid grounding for 132 kV transformers at this site.

10. Riel Substation Grounding Study

Project Outline:

Riel Station is a 230kV/500 kV power station Manitoba Hydro is planning to build. In addition to several 230 kV and 500 kV AC power lines, 500 kV DC lines are also planned to be connected to the station. The station is extensive, about 1700m by 800m, and is located near an extensive system of water pipes, which must be considered in the calculation of earth potential gradients and transferred potentials. The objective of the study is to design a satisfactory grounding system, which will ensure the safety of personnel and the integrity of the equipment at the station under fault conditions, accounting for contingency conditions and seasonal variations (freezing and thawing of soil).

11. National Grid Underground Safety Analysis

Project Outline:

This study consisted of a detailed parametric analysis of underground cable systems and safety of personnel during load and fault conditions, for different contact situations, cable types, vault types and safety bonding scenarios. Different ground mat designs for switch handles of overhead distribution lines were also compared.

12. ABB Nobel Substation Grounding Study

Project Outline:

Two 500 kV series capacitor banks are to be installed midway along a pair of transmission lines, at a location where the soil resistivity is extremely high (on the order of 4,000 to 5,000 ohm-m). The size of the station is 244 m by 124 m. The first objective of the study is design a grounding system resulting in acceptable touch and step voltages. A second objective is to determine the GPR of the station, which is highly dependent on the ground impedance of the 500 kV transmission line shield wires. A specification to measure the equivalent ground impedance presented by the shield wires was developed by SES, which also participated in the testing.

13. EWCC – EnWin – Ford Composite Grounding System Analysis

Project Outline:

This is an extensive grounding study involving the modeling of the two interconnected power plants, an associated switching station expansion, and two Ford motor plants, the objective being to investigate safety in the switching station expansion area and at the other facilities to which the substation is connected and to recommend any required mitigation.

14. Suncor Firebag Substation Grounding Study

Project Outline:

This study involved detailed modeling of a system of two 260 kV/144 kV substations, three 144 kV substations, two large generating plants, and 5 well pad substations, along with the interconnecting 260 kV and 144 kV transmission lines (over 100 km), the objective being to evaluate safety at the substations and plants and make recommendations, as applicable, to meet IEEE Standard 80, Canadian Electrical Code, and Alberta Electrical and Communication Utility Code safety requirements. It was found that grounded plant infrastructure and the optical shield wires used for the transmission system had a major impact on the results.

15. Suncor Voyageur Upgrader Project (VUP) Grounding Study

Project Outline:

Modeling of a 1 mile x 1 mile oil sands site and two offsites, with 15 substations ranging from 34.5 kV to 260 kV, two overhead 260 kV circuits, buried and overhead 34.5 kV circuits, cable/pipe racks and a good number of pipelines, whose through-earth and magnetic field interactions were studied, in designing a conceptual grounding system for the entire VUP meeting IEEE Standard 80. It was found that consideration of the grounding provided by supporting infrastructure (piles and interconnecting structures) tremendously reduced the need for any additional buried grounding conductors.

16. Marble River Wind Farm – Clinton/Ellenburg 230 kV/34.5 kV Substation Grounding Analysis

Project Outline:

A wind farm with 109 turbines, 2.1 MW each, was studied. Conceptual grounding designs for the main 230 kV/34.5 kV substation and for the turbines were evaluated, accounting for collector line grounding and current return in the 230 kV transmission line static wires. A total of 74 representative faults were simulated on the 34.5 kV collector system and at wind turbines, in addition to faults at the main 230 kV/34.5 kV substation. Frozen, partially frozen and unfrozen soil conditions were considered. Recommendations were made with respect to the most cost-effective grounding, accounting for the interactions of all wind farm components.

17. Herblet Lake Performance & Measurements Analysis

Project Outline:

This study involved the verification of the grounding of a 230 kV substation located in an area with high soil resistivities (on the order of 3000 – 6000 ohm-m near the surface and 700 ohm-m below that). Detailed soil resistivity measurements were made in both winter and summer and considered in the analysis. Various contingencies, such as the loss of a line or loss of ground rods, were also examined. It was found that the high surface soil resistivities, while resulting in greater touch and step voltages, also resulted in allowable touch and step voltage limits, ultimately providing a satisfactory solution to an otherwise difficult problem.

18. Paca & Orchard Substation Grounding Study

Project Outline:

This study involved two urban 115 kV substations with GIS and 60 kA fault levels. SES demonstrated that the buried cable ground conductor/concentric pipe return paths and the metallic water system surrounding the substations reduced grounding requirements significantly despite the high fault current levels. SES also demonstrated the effectiveness of the unipolar Wenner method for soil resistivity testing.

B. Mitigation of AC Interference from Electric Power Systems

1. EMI Mitigation Design Study for FGT 12" Gandy Blvd Relocation Project

Project Outline:

AC interference mitigation design study for 12" directionally drilled high pressure natural gas pipeline installed parallel to 115 kV and 230 kV underground circuits, over distance of roughly 3 miles, in very low resistivity soil. AC corrosion concerns dominated this design effort, which applied novel mitigation design techniques to achieve acceptable current density levels in a brackish water environment. Power plant at one of the joint-use corridor, 230 kV / 115 kV substation at the other, and surrounding transmission system and urban infrastructure were also modeled.

2. EMI Study for Jackson's Ferry - Wythe/Progress Park 138 kV Transmission Line Project

Project Outline:

AC interference mitigation design study for 138 kV dual-circuit overhead transmission line running parallel to 24" high pressure natural gas pipeline for a distance of 3 miles.

3. EMI Study for ETT Clear Crossing - Dermott 345 kV Transmission Line Project

Project Outline:

AC interference mitigation design study for 90-mile double-circuit 345 kV transmission line running parallel to 16" natural gas pipeline over distance of roughly 6.3 miles, in very low resistivity soil, crossing it at 3 locations. A total of 7 pipelines with exposure to the transmission line were studied, along with another 345 kV line and a 138 kV line. Severe AC corrosion concerns dominated this design effort. Optimization of the mitigation, compared with an alternative design initially submitted by others, resulted in cost savings estimated to be on the order of 10% of the entire transmission line construction cost.

4. CoSyn FFT Pipeline EMI Study

Project Outline:

Study of induced voltages in 42” FFT aboveground pipeline in oil sands mine, due to adjacent 72 kV circuits. Found capacitive coupling to be the dominant mechanism during load conditions. Minimal mitigation found to eliminate potential nuisance shocks.

5. ETT Simple EMI Mitigation Study Illustrating Impact of Modeling Coating Holidays

Project Outline:

Feasibility study illustrating the great impact on mitigation requirements of accounting for through-earth coupling from gradient control wires when assessing ac leakage currents from coated pipes due to magnetic field induction from nearby double-circuit 345 kV transmission line.

6. Electromagnetic Interference Analysis of Underground Circulating Water Pipe

Project Outline:

Determination of ac leakage current density, potential rise and temperature rise of underground circulating water pipes exposed to induction from adjacent 230 kV transmission line at Entergy’s Ninemile Power Plant. Required detailed modeling of prestressed concrete cylinder pipes.

7. Maine Power Reinforcement Project – 345 kV Transmission Line Impact Study

Project Outline:

This is an analysis of the impact of (Phase I) and design of mitigation for (Phase II) a 247-mile 345 kV transmission line system and nearby 115 kV transmission lines on parallel pipelines (on the order of 125 miles) and railways (on the order of 10 short parallel sections or crossings). The impact of the new 345 kV lines on lower voltage transmission lines (115 kV and 37 kV), when de‑energized, is also being examined. This very large project has required custom automation of the CDEGS software package. Furthermore, it has required the development of a methodology to correct soil resistivity measurements for distortion introduced by bare metallic structures buried along the joint-use corridor.

8. BP Skarv Swivel EMI Interference Study

Project Outline:

Evaluation of induced voltages and currents between power cables and other types of cabling associated with a floating production and offloading vessel.

9. Greater Springfield Reliability Project – Electromagnetic Interference Study

Project Outline:

Impact analysis and mitigation, as required, for 5 natural gas pipelines and 4 railways following or intersecting a planned 35-mile 345 kV transmission line and several 115 kV lines, to be built as part of the New England East-West Solution (NEEWS).

10. National Grid – MBCR/MBTA Transit System – AC Interference Investigation

Project Outline:

In the spring of 2008, MBCR, the agency operating the commuter rail for the Massachusetts Bay Transportation Authority (“MBTA”), notified National Grid of problems it was experiencing with its control and signal circuitry in the vicinity of Massachusetts Electric Company’s Ward Hill Substation. MBCR/MBTA believed these problems were associated with the close proximity of the 23 kV circuits running alongside two sets of tracks abutting on the substation property. MBCR/MBTA personnel reported various equipment failures that allegedly have resulted in operational delays for commuter trains. The main purpose of the study is to determine the magnitude of the electromagnetic interference (EMI) levels caused by the local electric distribution circuits on the railway system, based on detailed realistic computer models, during worst case steady state (load) conditions and phase-to-ground fault conditions and, if needed, determine mitigation measures that would be the most effective in reducing any excessive induced voltages and currents to acceptable levels.

11. Benton Lake Telephone Lines Harmonic Interference Analysis

Project Outline:

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. Further testing after construction of the 115 kV line validated the predictions of the impact of the 115 kV line.

12. Norfolk Southern – Cleveland Public Power – AC Interference Analysis

Project Outline:

Study of AC interference between proposed 138 kV transmission line and two sections of track belonging to Norfolk Southern Railway Company, for a total of approximately 7 miles of joint-use corridor. Existing 345 kV and 138 kV transmission lines and four substations located near the railway must also be considered, for both load and fault conditions, with multiple failure contingencies and possible train locations.

13. Bethel-Norwalk Extended Electromagnetic Compatibility Analysis

Project Outline:

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.

14. Verification of Mitigation: NRI 345 kV Line/ M&N Pipeline

Project Outline:

Verification of as-built mitigation for M&N Pipeline, which runs parallel to the soon to be energized NRI 345 kV line in the State of Maine, U.S.A. Computer modeling and field testing of mitigation. Test procedures were devised to verify the performance of mitigation during both fault and steady state conditions. This involved measurements at approximately 100 sites, including one compressor station, 5 valve sites, approximately 70 test stations, and 30 additional mitigation connection locations.

15. Middleton-Norwalk Electromagnetic Interference Study

Project Outline:

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.

16. Benton Lake Telephone Lines Harmonic Interference Analysis

Project Outline:

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.

17. GMCW 345 kV Line NEV Study

Project Outline:

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.

18. Neutral to Remote Earth Voltage Analysis - Jefferson Transmission Line Project: Phase II

Project Outline:

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.

19. Neutral to Remote Earth Voltage Analysis – North Randolph-Fox Lake-North Beaver Dam Transmission Line

Project Outline:

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.

20. Neutral to Remote Earth Voltage Analysis - Duplainville Transmission Line Project

Project Outline:

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.

21. Glenbrook-Norwalk Electromagnetic Interference Study

Project Outline:

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 minimal corrective measures were required.