Servicios

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.

Special safety procedures for work at 72 kV/13.8 kV substations, during frozen soil conditions, at Syncrude Aurora mine.

Study of safety at 72 kV/7.2 kV tailing booster pumphouse substation during fault conditions on 72 kV and 260 kV systems, at Suncor mine. Included interpretation of soil resistivity measurements, computer modeling of pumphouse substation and 72 kV distribution system, examination of safety at 72 kV substation and transferred potentials to pumphouse and piping, formulation of recommendations.

Planning stage modelling of extended grounding system of a proposed mine, with pipelines, in order to provide guidelines for control of GPR, transferred potential, induced AC voltage, touch and step voltages throughout the mine. Parametric analysis to estimate transferred potentials throughout mine as a function of fault current levels, connection or isolation of 260 kV substations, soil structure, and fault location.

The objective of this study was to compute touch voltages, step voltages, GPR (ground potential rise) and ground resistance of a system of 5 local interconnected grounding systems at the Kirkland Lake Peaking Plant and two remote grounding grids, during 115 kV fault conditions.

An extensive system of twenty 72 kV substations and associated transmission lines was modeled in order to determine what measures were required to maintain transferred potentials to facilities near substations to acceptable levels, during phase-to-ground fault conditions. It was found that enhanced ground return paths to the fault current source provided significant relief. On the other hand, ground wells on the 72 kV line ground return conductors, even when placed a minimum of 100 m from the substation, while reducing the GPR values of the faulted substations, actually increased the transferred potentials to the facilities served by the substations, in some cases. This study underlined the importance of modeling not only substations and adjacent facilities, but also neighboring substations and grounding on the power lines.

In this project, SES modeled 78 substations (500 kV, 220 kV, and 110 kV), associated transmission lines, and other infrastructure, in order to investigate problems associated with dc circulating currents flowing into the substation transformer primary windings through the neutral ground connections. SES also studied ac circulating currents during fault conditions in this major station, which is supplied directly by the Three Gorges Dam project. A key result of this study was the development of a new conceptual grounding method, which greatly reduces dc circulating currents and, thereby, wear on the station transformers.

This study, carried out in close collaboration with Manitoba Hydro, made use of detailed testing of soil resistivities and temperatures, as a function of depth, from the autumn of 2003 through the spring of 2004: winter and early spring soil conditions represent worst-case conditions that must be considered in areas where the soil freezes beneath grid depth. Ground impedance measurements of this 600 m x 1000 m station were interpreted with HIFREQ, which reproduced inductive and conductive coupling encountered during the testing, based on a detailed model of the grounding grid, test leads, and 12 transmission lines (230 kV and 500 kV). This study also examined the sensitivity of grounding grid performance to ground rod density. Protection of a railway spur entering the substation and an associated main track was also studied.

SES recommended, as a precautionary measure, the installation of crushed rock along two sections of the fence running along the access road to the power plant. The client requested that SES conduct testing along the fence to determine if native soil resistivities are sufficiently high to obviate the need for crushed rock. Custom equipment was built and testing was carried out. A mitigation alternative was found: displacement of a steel water pipe.

Grounding analysis for three 72 kV shovel substations at Syncrude Aurora Mine, as a function of seasonal variations and as a function of neutral ground resistance at supply transformer.

Safety evaluation of Henday and Radisson AC/DC Converter Stations in Northern Manitoba during fault conditions: interpretation of soil resistivity data and fall-of-potential impedance measurements; modelling of 138 kV and 230 kV lines, nearby substations, hydro-electric plant, and railway spur.

Analysis of hydro-electric plant and 115 kV switchyard grounding, as a function of soil resistivity and grid conductor integrity, in view of increases in fault current duty.

Computer modelling and measurements (electric fields in water, grounding grid continuity, grounding grid impedance, soil resistivity) at Sullivan hydroelectric plant, in order to assess need for protective measures for fish and divers in the event of a fault with future fault current levels.

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.

As part of an AC interference study between two 60 kV transmission lines and two main railroad tracks, results from the Right-of-Way Pro and MultiFields software packages were compared and a parametric analysis was carried out. Induced voltages computed by the two software packages for similar models agreed reasonably well. However, the addition of nearby network of municipal water pipes and 12 kV distribution line neutrals in the HIFREQ model made it possible to demonstrate that induced voltages were significantly different than would otherwise have been expected: maximum variations of ±20% were observed between the two models, during worst case load conditions. For the parametric analysis, parameters such as ballast resistance, train position, train length, rail unbalance, track-connected equipment impedances, power line current unbalance, power line phase arrangement, and overhead ground wire connections were studied. It was found that for rail-to-rail voltages, the worst case ballast resistance is a function of the impedances of the track-connected equipment and does not occur, as intuition might have it, for the maximum ballast resistance. A new method of using an overhead ground wire to reduce AC interference during fault conditions, without a corresponding increase during load conditions, was developed.

Review of the report dated November 25, 2003 and associated data files submitted by ARK Engineering & Technical Services, Inc. following its AC interference study of Line 500 of Gulfstream Natural Gas System’s Phase II project.

An exacting client, subject to strong pressure from a local community, required a method to reduce magnetic field levels over a 345 kV buried cable to 1 milliGauss (!) at grade, at a location where the cable crossed a park, at a burial depth of 6 m. SES examined fields generated by unbalanced current flowing in the cable cores, corresponding induced currents in the cable sheaths, armors, ground return conductors and magnetic shields, and zero sequence ground return currents caused by interactions with the load substation autotransformers and their grounding system, near the park. SES demonstrated how the 1 milliGauss limit could be achieved for these magnetic field sources, with a suitable choice of grounding points. Stray currents from other sources were excluded from the study, by the client and by the design specifications.

AC mitigation study and radio noise analysis for proposed power plant and 345 kV transmission line to be built along high speed Amtrak railway.

AC mitigation study involving corridor shared by 138 kV and 25 kV circuits, two water pipes, and two carbon dioxide pipes.