A guide to managing ambiguous specifications
A guide to managing ambiguous specifications.
Electrical safety in low voltage switchgear is not a new topic, since the dangers associated with the manual operation of any electrical switchgear, particularly on-load switching, have always been present. Through personnel training and certification, all certified electrical technicians/engineers will be aware of the risks to both personal safety and operational assets during electrical switching.
However, without a defined international standard for LV products to provide arc-fault containment (IEC TR61641:2014 is still only a test report) the requirements defined by end-users or in specifications can be varied or ambiguous as the natural reaction is often to default to the most onerous possible requirement without fully understanding the options available. The result is often provision of a premium solution which may not give the end-user the best fit in terms of maintenance and/or operational safety. A good overview of Arc-Fault capability was provided back in 2017 by GAMBICA in their guide which is still available on-line for free.
For new projects Blackburn Starling & Co. Ltd are often asked to provide solutions which can include one or more of the following features:-
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LV switchboards/MCC specified to comply fully with IEC/TR61641:2014. These can be provided as a premium product to comply with arcing classes (A,B or C) as detailed within the test report. The GAMBICA guide is again recommended to select the relevant arc class for containment to provide purely personnel protection (Class A) through to containment within individual functional units or sections (Classes B or C) when related to Form 4 switchgear.
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Fully insulated busbar systems to preclude an arc-fault occurring within the low voltage panel, this is to provide compliance with section 6.1 of the test report.
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OEM products to incorporate safety features including:- Air-circuit breakers which include maintenance modes to limit the fault level of the circuits whilst an engineer is switching the ACB for maintenance.
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Arc-flash detection equipment where the protection relay has a fibre-optic cable installed throughout the length of the busbar chamber within an LV panel to provide a high-speed trip to the main circuit breaker upon detection of an arc-flash incident.
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The supply of remote operator panels or pendants to allow the switching of the circuit breakers to be carried out without the need to have an engineer standing in front of the panel thereby reducing the risk of any injury from arc-fault incidents.
Once installed on site the PPE category, incident energy and safe working distance for the switchgear should also be calculated to allow this information to be displayed on each section of the LV equipment. All manufacturers should be able to assist with these calculations, Blackburn Starling & Co. Ltd use a licensed software package for this purpose with data both from our own installed equipment and details of the external field cabling, transformers etc.
As with all bespoke equipment it is always recommended to have the conversation as early as possible in the design phase of a project to allow the LV switchgear supplier to advise on their recommendations and options. Following a review of the options available, the client can choose the most appropriate method for their site and operations teams to provide the optimum solution.
For more information visit: www.blackburn-starling.co.uk
