Grounding and Lightning Workshop Draft Program Now Available

Ground grids play a number of crucial roles in safe operation of power systems, including safely conducting short circuit current, maintaining Ground Potential Rise (GPR) within acceptable limits, controlling and maintaining step and touch potentials within a safe range and providing low impedance path for passage of lightning current.

The overarching objective of this assignment is to identify and quantify the risks associated with ground grid designs and propose cost effective ways to mitigate those risks, so that safety of people and equipment through a properly functioning and cost efficient grounding system could be ensured.

In spite of their crucial role in safe, reliable and economic operation of power supply systems, grounding systems do not receive the same level of preventative maintenance as other assets. While utilities have generally adopted state-of-the-art risk based maintenance practices for other important assets, virtually no work has been undertaken in improving and modernizing maintenance practices for grounding systems.

The primary aim of this project is to develop optimal preventative maintenance strategies for grounding systems, providing the required balance between safety, reliability and power quality on one hand and the operating costs on the other.

The 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.

This project will:

• 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.

The 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 on the ground, analyzing testing techniques used by the instrument, and documenting problems encountered by utility staff when using the instrument through a survey.

The principal objective of this project is to reassess and update the surge arrester application manual to encompass current practices. The update will include sections on surge arresters for particular applications dealing with the distribution system of the future, along with the changing infrastructure and renewable generation. The work will consist of information gathering and engineering analysis to develop a modern and relevant tool for electric distribution engineers to use for selecting surge arresters for their systems.

Over recent years, it has become evident that even relatively low levels of stray voltage can adversely impact farm animals, reducing milk production or affect operation of sensitive electronic and medical equipment. Many regulatory jurisdictions are now mandating power distribution companies to investigate and mitigate stray voltage complaints, when they are received.

The 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.

• Ground Grid Corrosion (3030B)
• Guidelines for the Installation of Surge Arresters on Sub-Transmission and Transmission Lines Using Different Structure Designs at Voltages from 69 kV to 345 kV (3312A)
• Use of Lightning Arresters to Protect and Improve Outage Performance of Unshielded Lines (3106)
• Stray Voltages in Higher Load Density Environments-Causes, Effects, Measurement and Mitigation Techniques (5131B)
• Simplified Rules for Grounding Customer-Owned High Voltage Substations (249 D 541)
• Distribution System Grounding Practices (249 D 540)