Q: We have crews working under a clearance on a de-energized circuit jointly controlled by two different utilities (employers). The concern is that the other employer’s personnel, wishing to bundle maintenance opportunities during the outage, are taking protective relays out of service on their end of the circuit. If a switch were inadvertently closed on their end, taking their relays out means no tripping protection since the other end of the circuit is open, too. Such an action could delay if not eliminate relay protection and raise current on the grounds protecting our workers. Is there an obligation between utilities to manage an outage under common rules?
A: There is an OSHA-based solution that comes in two parts. And even though your question is about grounding and tripping during inadvertent re-energizing, the solution to the issue actually lies ahead of grounding.
As you are aware, OSHA 29 CFR 1910.269(m) contains the rules for de-energizing lines and equipment for the protection of employees. That rule section is the pre-eminent means of ensuring no switch is ever closed without the permission of the employee in charge of the equipment or lines that have been de-energized and placed under their control. As you noted in your inquiry, we ground a circuit after the clearance process to ensure against any possibility of re-energizing. The grounding is based on an evaluation of relay trip settings to assure effective tripping to protect the crew under the clearance. Any change to the values or trip settings puts the crew at risk.