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Minimize Fire-Producing Sparks from Utility Equipment

June 1, 2020
High voltage surge arresters and fire protection disconnectors minimize fire-producing sparks from utility equipment.

High voltage A.C. surge arresters protect vital utility equipment that is costly to replace and often has long lead times to acquire, such as pole top transformers, breakers, or other devices.

Under normal operating circumstance, arresters act as high impedance devices which allow a small amount of current to pass through the devices. When an arrester is exposed to an increase in current, due to lightning or a switching surge, the MOV blocks in the core of the arrester switch into an electrically conductive low impedance state. The surge current is diverted to ground and the arrester limits the voltage across the protected equipment. By limiting the voltage across the arrester and the protected device, the MOV blocks prevent damage from occurring. Following the surge, the arrester returns to a normal high impedance type state.

If a sustained voltage exceeds the capability of the surge arrester, the current that the device is conducting increases significantly. If the arrester short circuits, the system fault current flows through the arrester. When this occurs, hot particles may be expelled which may cause a fire.

Usually distribution surge arresters are equipped with a ground lead disconnector (GLD) which reacts to sudden current increases.

A blank 22 cartridge actuates and breaks the line to ground connection. This removes the shorted product from the system and allows the system to be re-energized. At the same time, arcing and stray particles may be emitted. These must be contained to mitigate the potential fire risk.

Countries and regions have taken different approaches to certifying high voltage surge arresters:

  • Australia has developed high voltage surge arrester standards. These are based on IEC standards.  Australian standards include a subsection with specific criteria to qualify the spark production class. One commonly used calibration test method to quantify the fire risk is called the “ground paper method.” Australian utilities often require products that meet Class A spark production (zero sparks) based on ground paper testing.
  • California relies on the California Power Line Fire Prevention Field Guide. This document outlines procedures to minimize the risk of catastrophic wildfires caused by electrical power lines and equipment. The guide details testing processes and qualified test equipment that meets requirements for CalFire exempt status for electrical equipment. The current edition of the guide was released in 2008, but an updated draft is expected later in 2020.

Hubbell has developed a surge arrester specifically to meet Australian test requirements for Class A. If incandescent particles are emitted from this arrester, they don’t have enough energy to ignite a fuel bed.  This product includes insulated line and ground sealing caps which limit the available energized surface area. In some regions of Australia, surge arresters aren’t installed with a GLD.

In response, Hubbell has also developed a fire protection disconnector (FPD) solution. This retrofit option for existing surge arresters is designed to reduce fire-producing sparks. Upon activation, the FPD disconnects the arrester from the line and provides a visual indicator. Additional protection against wildlife interference is provided through an optional wildlife guard.   

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