Providing safety at the presence of arc flash hazard risk in the high voltage equipment

Marinela Yordanova Yordanova

doi:10.29114/ajtuv.vol2.iss2.90

Abstract

The hazards of electric arcs in Bulgarian norms, as the Regulations on Health and Safety at work in electrical installations of electrical and thermal power stations and electric power lines and Ordinance №9 on the technical operation of power stations and electric power lines mainly govern the safety at work with high-voltage equipment, are not subject to a special section. NFPA 70E Standards for electrical safety in the Workplace requires to assess whether there are arc-dangers; to calculate the energy released by the arc; to define the permissible arc protection boundaries; to provide adequate personal protective equipment and to label the equipment. The aim of the paper is to summarize the Bulgarian requirements connected somehow with the flash hazard, to compares similarities can be found in approaches to ensuring electrical safety with those of international standards.

Highlights

One of the possible reasons for electrical accidents may be the development of open powerful electric arcs between the contacts of the switching devices, the short circuits or earth faults in the electrical switchboards, when replacing live fuses in the presence of current circuit breakdown, in unsafe testing of repaired equipment and products, etc. (Ушев & Йорданова, 2003), (Анев, 1987), (Иванов, 2011)
National Fire Protection Association 70E Standards for electrical safety in the workplace require to assess whether there are arc-dangers, to calculate the energy released by the arc, to define the permissible arc protection boundaries, to provide adequate personal protective equipment and to label the equipment
Prohibited Approach Boundary (PAB) – „Аn approach limit at a distance from exposed live parts within which work is considered the same as making contact with the live part.“. Those boundaries define the following spaces: - Limited space (LS) is the zone of the final access, which is between Limited Approach Boundary (LAB) and Restricted Approach Boundary (RAB). - Restricted space (RS) is a restraint zone between RAB и PAB. - Prohibited space (PS) is a forbidden zone between PAB and any point of the exposed live parts

Summary

Introduction

One of the possible reasons for electrical accidents may be the development of open powerful electric arcs between the contacts of the switching devices, the short circuits or earth faults in the electrical switchboards, when replacing live fuses in the presence of current circuit breakdown, in unsafe testing of repaired equipment and products, etc. (Ушев & Йорданова, 2003), (Анев, 1987), (Иванов, 2011). The pressure at a distance of 61 cm from an electric arc with a current of the order of 22 kA can cause a force of 225 kg over the given person;. Flash hazard is „a dangerous condition associated with the release of energy caused by an electric arc" (NFPA, 2004). One of the units used to measure the incident energy is calories per centimeter squared (cal/cm2) This energy is used to determine the level of the personal protective equipment (PPE) and the permissible boundaries of protection from the impact of the electric arc. An electric arc risk analysis defines procedures that limit the possible damage to the personnel and by measuring the incidental energy to define the risk areas and the appropriate PPE level (ABB, 2009). The aim of the paper is to summarize the Bulgarian requirements connected someway with the flash hazard, to compare the similarities in the approaches for ensuring the electrical safety with those from international standards

International and Bulgarian norms

Bulgarian norms

Conclusion