Arc Flash Incident – No Loss

Enform Canada recently reported on this arc flash incident which occurred when a technician touched two exposed lugs of a 480-volt main breaker. No injuries resulted.

 

Safety Alert # 13-2009
Arc Flash Incident - No Loss
Release Date: September 14, 2009

Summary:
An arc flash occurred when a technician touched two exposed lugs of a 480-volt main breaker in a Motor Control Center (MCC) while performing maintenance checks.
 
Description of Incident:
During the course of commissioning a new 480v MCC, a contact technician was required to perform phasing checks on the exposed lugs on the line side of the 480v main breaker. The technician was using a commercially available set of phase sticks with a shepherd-hook style end. When the technician attempted to check the phase C lug, the hooked end of the phase stick came in direct contact with both B and C phase lugs. Spacing between the lugs was approximately 1”. As per manufacturer’s specification for this voltage, there were no barriers between the lugs. The resulting contact cased an arc flash.
 
While the worker was not injured, there is potential for an arc flash to cause serious burns. Explosive arc blasts can also occur causing damaging sound levels and exposure to a high pressure blast which could cause eardrums to rupture and lung damage.
 
Important investigation results identified that:
• An arc flash hazard study had been conducted on the MCC. The equipment involved in the incident was rated and required Category 2 personal protective equipment.
• The technician was wearing the required arc flash rated PPE
• The technician thought that because the breaker was tripped, the lugs were de-energized.
• In an attempt to demonstrate what happened, the technician, placed the phase stick back into the breaker cabinet and caused a second arc flash. The technician thought that because the breaker had been tripped that the lugs were de-energized. 

Causal Analysis:
A detailed incident investigation was completed. The main causal factors were:
• The contactor’s safety management process did not identify the training standards and procedures required for contractors to perform critical work.
• The contractor’s standards did not address the hazards of working on exposed 480 volt terminals, barriers and breaker configuration for phase checking.
• The process of training electrical workers to become “qualified” and understand the hazards associated with arc flash were not well defined nor applied consistently with new workers.
• The ‘sheppards’ hook style phase stick was designed for overhead lines and was not the appropriate equipment/tool for checking this equipment.
• Hazard identification and controls were not implemented even though the work involved energized electrical parts.
• A Field-Level Hazard Assessment (FLHA) was not conducted prior to completing the phase checks to identify the hazards of performing this job.

We Can Prevent Similar Incidents:
This incident reinforces the importance of the fall protection requirements identified in occupational health and safety regulations. In this case, the employer identified the following corrective actions:
• Review and enhance contractor selection process to ensure that training standards and procedures have been established for electrical contractors performing
• Develop an Arc Flash Hazard Study standard consistent with industry standards. Ensure that all analysis are conducted in accordance with this standard and that the results are communicated to personnel performing maintenance work.
• Revise/enhance Company standards and training program to address arc flash and electrical shock hazards.
• Work on high-voltage electrical equipment is a critical task and requires that a Field-Level Hazard Assessment (FLHA) be completed before beginning work. Additional Information: In addition to the Canadian Electrical Code (CSA C22.1-09), other relevant references include:
• NFPA 70E-2000 Standard for Electrical Safety Requirements for Employee Workplaces.
• IEEE Standard 1584-2002 Guide for Performing Arc Flash Hazard Calculations
Contact:
safety@enform.ca  

DISCLAIMER:
This Safety Alert is designed to prevent similar incidents by communicating the information at the earliest possible opportunity. Accordingly, the information may change over time. It may be necessary to obtain updates from the source before relying upon the accuracy of the information contained herein. This material is presented for information purposes only. Managers and supervisors should evaluate this information to determine if it can be applied to their own situations and practices