Secondary Network Arc Flash Case Study

Arcflash

Aug 18, 2019

By Tony Oruga

Network crews were working in an electrical room tasked to install an 800 A disconnect for a temporary service on the network secondary. The 3-spot network was energized at 480 V on the secondary (34.5 kV on the primary) and all three network protectors were closed and serving load. Each network protector installed was a 3000 A, 480 V Eaton CM52 unit equipped with an Arcflash Reduction Maintenance SystemE (ARMS). Prior to performing their work, crews enabled the ARMS function on all three units in the spot. This put all three network protectors in a “hair-trigger” mode, ready to clear any current condition that exceeded 2.5x the nameplate rating.

As part of standard utility work, all procedures were followed in accordance with their specific utility standard practices. The workers had the specified PPE for those specific work conditions. However, as in any work environment, unforeseen events still occur and crews are trained to deal with less than ideal circumstances. During this particular install, the worker lost positive control of the wrench he was using to install 500 kcmil cable to an energized copper bus. This resulted in the wrench hitting the unistrut, which created a path to ground between the unistrut and the live network secondary. The calculated available fault current at the collector bus is 101.2 kA assuming 25 kA symmetrical available fault current on the 34.5 kV primary bus with balanced contribution.

Because the ARMS protection system was enabled as a part of standard working procedure, each CM52 unit interrupted in approximately 1.9 cycles once the 7500 A threshold was met. According to crew reports, the ARMS device activated and cleared the fault before the worker noticed they had made contact with the energized bus. See Figure 1 for a depiction of the network arrangement.

[PLEASE INSERT EIN-34-WhitePaper-2.jpg HERE]

This technology has been proven with substantial test data to support its capability; however, this is the first report of the ARMS system being called to action during a network arc flash event involving real world circumstances that prevented severe injury or possible death to the worker. The purpose of this white paper is to share this event with others and help create a safer environment through technology for those working in these applications.

System characteristics

• Utility: Austin Energy
• Location: Austin, TX
• Network size: 3-spot network
• Transformer size: 2000 kVA delta-wye; 7% impedance
• Primary system voltage: 34.5 kV
• Secondary voltage: 480 V
• Network protector size: 3000 A; 480 V
• Network protector type: Eaton CM52
• Available incident energy: approximately 200 cal/cm2 (without ARMS considered) based on system analysis
• Available fault current on 480 V secondary: 101.2 kA (3 x 33.7 kA for parallel contribution)
• CM52 ARMS total clear: 1.9 cycles on average
• CM52 ARMS activation: at 2.5 x 3000 A (nameplate rating) = 7500 A

Go here for additional network protector ARMS technical information.

Tony Oruga is a product and sales manager for Eaton. This article was first published online: https://www.eaton.com/content/dam/eaton/products/utility-and-grid-solutions/network-protector-solutions/secondary-network-arc-flash-case-study-wp024002en.pdf

 

Related Articles


Latest Articles

  • Ontario EV ChargeON Program Accepting Applications until January 31, 2024

    Ontario EV ChargeON Program Accepting Applications until January 31, 2024

    November 29, 2023 The province is accepting applications for the EV ChargeON program to build publicly accessible charging stations in communities with less than 170,000 people, as well as in any Indigenous community in Ontario. Eligible applicants include businesses, not-for-profit corporations, municipalities, Indigenous businesses, organizations and communities, and broader public sector organizations like hospitals and… Read More…

  • A Closer Look at ESA’s EV Charger Installation Blitz & EV Charger Considerations

    A Closer Look at ESA’s EV Charger Installation Blitz & EV Charger Considerations

    Earlier this year, the Electrical Safety Authority (ESA) conducted an EV charger installation ‘blitz’ as part of their campaign to educate homeowners and consumers, in an effort to improve EV charger installation safety in Ontario. Read More…

  • I Have Two Questions for You

    I Have Two Questions for You

    November 24, 2023 By Keith Sones, Valard EVP Strategy & Business Development I have two questions for you. First, how many people do you think you’ll meet in your life? It’s not that hard to determine, quite frankly. Yes, it requires a lot of assumptions to represent the “average” person, but it is possible. Before… Read More…

  • Sonepar Partners with Design de Plume on Land Acknowledgement

    Sonepar Partners with Design de Plume on Land Acknowledgement

    November 24, 2023 Sonepar Canada announced on its LinkedIn page that it has partnered with a women-led, indigenous-owned design team,  Design de Plume Inc. to create a four-piece art collection to acknowledge the land that their head offices are built upon. “At Sonepar, we are committed to fostering a trusted partnership with Indigenous communities across Canada…. Read More…


Changing Scene

  • Rexel Announces Changes to Group Executive Committee

    Rexel Announces Changes to Group Executive Committee

    December 1, 2023 Rexel today announced the appointment of Roger Little as Chief Executive Officer (CEO) for the USA and leader of the USA-Canada cluster, effective December 18, 2023. Roger Little has been CEO of Rexel Canada since March 2014 and will succeed Brad Paulsen as CEO of Rexel USA as Mr. Paulsen leaves the… Read More…

  • EFC Welcomes New Distributor Member: Electromart Inc.

    EFC Welcomes New Distributor Member: Electromart Inc.

    November 30, 2023 For over 40 years, Electromart has been going the extra distance to ensure their customers purchases are easy and fun! Primarily geared to serve tradesmen, contractors, commercial, industrial, and retail clients, the company offers knowledge and experience to its customers. The EFC-Official Representative for Electromart is Joan Orgel, Operations Manager. More information… Read More…

  • Graybar Ontario Team Contributes Greatly to the Purse Project

    Graybar Ontario Team Contributes Greatly to the Purse Project

    November 30, 2023 Team lead, Stefanie Cosentino, Graybar Canada, Women’s Network-Ontario Region committee member, and Andrew Fitzpatrick, Graybar Canada, gathered their teams and really did an incredible job with purse donations. The team donated over $500 in cash, which was matched by Graybar, and filled 27 purses, with the top 10 items needed and more…. Read More…

  • Adriano Occhialini joins AEMC® Instruments as the New District Sales Engineer in Canada

    Adriano Occhialini joins AEMC® Instruments as the New District Sales Engineer in Canada

    November 30, 2023 AEMC Instruments, part of the Chauvin Arnoux® Group announces the appointment of Adriano Occhialini as District Sales Engineer in Canada.  As AEMC® Instruments continues its expansion into Canada, Adriano will help bring his expertise and innovative solutions to more customers and businesses across the entire Canadian country. Prior to joining AEMC® Instruments, Mr. Occhialini worked over 20… Read More…