Grounding and Lightning Task Force

Grounding systems are installed throughout power and telecommunication systems to dissipate energy under lightning, fault and steady-state conditions. Today there is a greater awareness and desire to ensure that grounding for safety is achieved. There is also a stronger focus on improving lightning performance of transmission and distribution systems.

Grounding issues across the world have typically been dealt with by technical groups, each with their own specific terms of reference. The GLTF takes a broad spectrum view of grounding related topics by bringing together grounding experts to provide peer-to-peer guidance and an opportunity to network.

The CEATI Grounding and Lightning Task Force (GLTF) provides clarity and understanding on grounding and lightning related issues. It provides an avenue for moving information from one technical area to another through networking, aswell as defining the direction for future research.

Topics and Issues

• Grounding Design and Testing
• Distribution Neutral Conductor Grounding
• Ground Potential Rise and Step/Touch Voltage in and near Substations
• Transmission Line Grounding
• Standards and Training Related to Grounding and Lightning

Current Projects

• Evaluation and Comparison of Grounding Test EquipmentThe objectives of this project include defining grounding measurement needs, presenting a variety of testing techniques and ranking instruments under each measurement technique. This will allow the user to choose the best method and tool for the task in hand. The scope of work will include indentifying grounding parameters that require testing at both transmission and distribution levels, defining proper test methods and comparing the grounding test sets under each test method by evaluating the instrument data sheet, performing bench tests on the instruments to simulate problems in the field, analyzing testing techniques used by the instrument, and documenting problems encountered by utility staff when using the instrument through a survey.
• Soil Resistivity TestingThe resistivity of native soil under stations or line towers strongly impacts the size of the grounding electrode required to limit the potential rise at a given fault level. The resistivity also controls the number of conductors needed to limit more local step and touch potentials and affects the resistance under the foot, which controls the safe body withstand. Due to the high cost of copper and the labour involved for its installation, it is prudent to avoid unnecessary overdesign of this important component of the station or line structure. Consultants who test resistivity tend to apply their favorite test methods routinely. Sometimes the approach is not comprehensive, nor does it provide the right data for the designers. Errors in this data will be difficult to uncover, and may become known only after tests upon completion of the project show that the input data was deficient. The project objectives are as follows: Review existing and new methods for testing the resistivity of soil needed for the grounding design of stations and line towers. Determine where different probe arrays are best applied and their proper range of probe spacing. Investigate new arrays that could expedite testing. Estimate errors due to the proximity of metallic objects and limitations of meters. Develop techniques for testing frozen soil. Recommend standardized test procedures.
• An Assessment of Distribution System Neutral Grounding AlternativesThe overarching objective of this project is to find the optimal solution(s) to block the transfer of undesirable stray voltages from electric utility MV neutrals to customers with low level tolerance to stray voltages.

Recently Completed Projects