Manhole Explosions - Causes, Mechanisms, Mitigation

Talk Title:

Manhole Explosions – Causes, Mechanisms, Mitigation

Abstract:

Manhole explosions in underground electric utility systems are caused by the ignition of accumulated flammable gases. 

An explosion can release enormous amounts of energy, between 6 and 40 megajoules, which is equivalent to between 3 and 20 sticks of dynamite. A cast-iron manhole cover can weigh between 85 and 300 pounds (35 to 136 kg), and explosions have propelled these massive discs anywhere from 1 foot to 50 feet (0.3 to 15 m) into the air.

The gas accumulations can be ignited by various sources, including electrical sparks from damaged cables or faulty equipment. Research focuses on understanding the dynamics of these explosions through full-scale and simulated tests to develop and improve safety measures, such as vented or tethered manhole covers, to prevent damage and injuries.

Full-scale experiments, such as those conducted by the Electric Power Research Institute use controlled environments and various gas mixtures to study explosion parameters. 

Mitigation and prevention strategies include:

• Covers with vents to release pressure or tethers to restrain the cover
• Controlled Pressure Relief Systems
• Gas Volume Reduction: 

This talk describes research and full-scale testing conducted at the EPRI outdoor Lenox Laboratory over the past 30 or so years.

About the Speaker:

George Gela, PhD, PEng, is an internationally recognized electric utility expert with a PhD in electrical engineering and an extensive background in research, testing, and teaching.

After graduating with PhD degree from the University of Toronto, Canada, George joined the Research Department of Trench Electric, manufacturers of high- voltage air-core reactors.

Dr. Gela taught graduate and undergraduate courses in Power Systems, Power Electronics, and Renewable Energy at The Ohio State University in Columbus, OH, the Western New England University in Springfield, MA, and the Rensselaer Polytechnic Institute in Troy, NY.

In 1990, he joined the Electric Power Research Institute (EPRI), in Lenox, MA. At EPRI he managed a wide range of R&D projects in manhole events, live working, helicopters in line environment, arc flash, transmission systems, control room operations, EMF and other areas. He provided training and consultations to EPRI member utilities (representing more than 90% of electric utilities USA) and in 20+ other countries. He also delivered Workshops in Australia, Brazil, Canada, China, Costa Rica, Poland, Thailand, Venezuela, and Ukraine.

Dr. Gela has authored and co-authored 20+ technical peer-reviewed papers, 100+ major research reports, 30+ conference papers, 80+ technical seminars worldwide, participated in 80+ technical panel discussions, and prepared several EPRI reference books.

In 2014, he set up Berkshire Electric Transmission Consulting Company (BETC) which offers specialized services, training and workshops in Australia, Brazil, Canada, China, Costa Rica, Poland, Thailand, Venezuela, Ukraine, USA and others.

He is active in IEEE (Life Senior Member), ASTM, ANSI, ICOLiM (International Conference on Line Maintenance), the Live Working Association-Europe (LWA), CIGRE (Conseil International des Grands Réseaux Électriques), and IEC.

He served for 21 years as Chair of IEC TC 78 Live working, then as Vice Chair. He now serves as Technical Advisor of USNC (United States National Committee) of IEC TC 78 and IEC TC 129 and assists the CANC of IEC as a non-voting member.

George received numerous awards, medals and distinctions for his work, including the IEC 1906 Medal commemorating the establishment of IEC, the CIGRE Pin from USNC CIGRE for individual contributions, and various recognitions by other organizations.

Host or Publisher IEEE CT PELS Chapter