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Explosive Flammable Gases/Vapours
UK DNO’s detail safe working procedures and rules in their Document Manuals to be followed when working on alkaline or acid substation batteries and storage rooms located within primary network medium/high voltage substations (MV HV).
Lead-acid type batteries release potentially explosive hydrogen gas when charging – this is the primary explosive risk associated with medium/high voltage substations.
Consequently, these worksite locations are classified as hazardous area Zones according to the ATEX Directive – a “hazardous area” is defined as an area in which the atmosphere contains, or may contain in sufficient quantities, flammable or explosive gases, dusts or vapours. The Zone designation depends on the level of risk and likelihood of flammable gas, vapour or mist forming during normal operation.
ATEX is an abbreviation of “Atmospheres Explosibles” and is a set of European Union regulations that are designed to ensure the safety of electrical products being used in potentially explosive atmospheres.
Thorne & Derrick, Experts in Equipment for Explosive Atmospheres, provide Zone 1/Zone 2 (Flammable Gas) ATEX Compliant electrical equipment for installation in substations and battery rooms to provide heating, lighting and power distribution.
The main Dangers to Persons carrying out work or testing on batteries and chargers are electric shock, explosion or burns arising from the ignition of flammable gas which is emitted by cells during the charging process.
Flammable gas can be ignited by naked flames (eg “hot-working” by cable jointers), cigarettes or by sparks if cell terminals are accidentally earthed or shorted together.
This short-circuiting releases dangerous levels of heat, light and arc energy.
Consequently, electrical equipment installed in MV HV substation battery rooms should be Zone 1 or Zone 2 certified according to ATEX Directive for safe installation in such potentially explosive atmospheres.
♦ Primary Network Substation: a 132kV, 66kV, 33kV or 25kV substation including directly associated 66kV, 33kV, 25kV, 11kV and 6.6kV switchboards at transformer stations (Definition: WPD Engineering Specification EE Spec 25/5).
How We Can Help?
♦ Lighting – T&D can provide lighting designs to ensure lux levels are achieved in line with regulations, fittings are located correctly and meet certification requirements – we provide a comprehensive hazardous area lighting system design service.
♦ Heating – T&D can provide battery room heat loss calculations to ensure the correct heaters are specified and meet ATEX certification requirements to provide adequate comfort heating to the substation.
♦ Power – T&D can specify and supply from stocks Joints & Terminations for the connection and energisation of high voltage power cables to switchgear and transformers up to 66kV.
The ATEX PIR detector is a movement sensor that detects a moving body heat (infrared) signature and provides an alarm output signal to the alarm/monitoring system accordingly within the substation battery room.