Training and Consulting
Grounding System Design
J Williamson Engineering Inc. available services include the following:
Specifically, These Services May Include The Following:
Field Measurements of Soil Electrical Resistivity
Field measurements of electrical resistivity are carried out with the AEMC 6472 or the Megger DET test sets, typically using the 4 point Wenner method. Aerial resistivity measurements using electromagnetic methods have been used on large transmission line projects.
Grounding System Design Using CDEGS Grounding Design Software
Grounding system design is completed using CDEGS software. Supplied by Safe Engineering Services & Technologies Ltd, the CDEGS software is a world leader in grounding system design.
Soil resistivity data is inputted into RESAP, and the grounding system design is completed using MALT or MALZ modules. The current split is determined using the SPLITS module.
Grounding impedance, Ground Potential Rise and Step/Touch voltages are computed to verify the safety of the grounding system.
Field Testing of Grounding Systems
Field testing of grounding systems is carried out to verify the design model and the overall safety of the grounding system. Testing of a substation grounding system includes measurement of ground impedance, current split, Step/Touch voltages, and resistance of buried connections. These measurements are used to determine Ground Potential Rise (GPR), ensure, Step/Touch voltages are safe and verify that all station components are grounded and bonded correctly.
Integrity testing of grounding system conductors and connectors is carried out with a Safearth CS3 continuity test set to ensure that all components are properly grounded and all connections are good electrical connections.
Substation ground system testing may require specialized test equipment rather than the traditional portable grounding test sets. J Williamson has experience using the new Omicron test model CPC 100 Multifunctional Primary Test System with the CP CU1 coupling unit for Line and Ground Impedance measurement. Current injection is done at 40 and 80 hertz, followed by measurements of Step/Touch voltages. Step and Touch voltages are measured with the Omicron Frequency Selective Voltmeter CP AL1.
Transmission structure and pole grounding systems can be accurately measured using the AEMC 6472/6474 Pylon Earth Tester. This test set uses Rogowski coil technology to accurately measure the structure ground impedance while still connected to a multi grounded system.
Lightning Performance Analysis Software
J Williamson Engineering Inc. utilizes the Sigma family of insulation coordination software. There are three modules to this software family which are SLP, SPX, and SSH.
Mitigation of Transmission Line Lightning Performance
J Williamson Engineering has considerable experience in the application of transmission line surge arresters and the use of shield wires to achieve acceptable lightning performance of the line. Surge arrester experience is well documented in technical papers which discuss arrester mechanical defects, installation problems as well as the superior performance of arresters under lightning conditions.
Shield wires perform well when the grounding impedance is low. Arresters on all phases on all structures can achieve zero outages due to lightning, provided the lightning strike energy does not exceed the arrester capability and cause an arrester failure. When shield wires are included along with arresters, the shield wire will reduce the lightning energy carried by an arrester and thus reduce the potential for an arrester failure.
Lightning Protection and Lightning Performance Studies Using Sigma Lightning Performance Software – SLP, SPX, and SSH
Grounding System Training Seminar (One Day)
This seminar is specifically related to electrical power grounding systems with the course material supported by years of experience troubleshooting utility grounding problems. The course is structured to provide a very fundamental introduction into grounding systems beginning with grounding system design followed by maintenance and testing of grounding systems. A brief discussion of lightning protection is included. The course material is based on ANSI/IEEE Standard #80 “IEEE Guide for Safety in AC Substations Grounding.”
This course is suitable for both new and experienced engineering and electrical staff involved in grounding system design, maintenance, and testing. It is very suitable for utility staff responsible for operating and maintaining grounding systems. The course is very appropriate as a refresher course for engineering staff and also for industrial electrical staff wanting a better understanding of power system grounding substation grounding particularly.