Lockout/Tagout (LOTO), a safety process for electrical power systems, is mandated by many standards as a means to achieve a safe working condition. More technicians are familiar with the first part of the lockout process – the isolation of the sources. But while doing maintenance on a MV power system with Metal Clad switchgear, turning off the main power sources, racking out the breakers and even protecting from the reinsertion of the breakers with safety locks is not enough. NFPA 70E .120.4 states that temporary protective grounding equipment shall be placed at such locations and arranged in such a manner as to prevent each employee from being exposed to a shock hazard. NEC 70.490.47 states the use of temporary safety grounding on the service equipment. This would include all main breakers and could mean other breakers which have a possibly of backfeeding (even from downstream sources). While this is likely basic to many of you, it is still not always practiced. Actual deaths have brought about the practice of temporary grounding required by many standards such as OSHA 29 CFR 1910.269, IEEE 1246, FIST 5-1, and IEEE 3007.3.

Several years ago, I witnessed a spark from the corner of my eye as a technician, face first inside a 5KV main breaker cable compartment, backed away from the compartment. He had in his hand a short piece of wire he had used to discharge the 5KV shielded cables (quite a long cable run). It turned out that the spark was just stored cable charge. BUT his lack of voltage indication, PPE, safety grounds and discharge method were a serious violation of safety standards. There are several things that could have made this a fatality.

Some of the reasons these safety standards require temporary safety grounding are possible accidental re-energization, backfeed from other sources, stored charge in cables, induced current in the circuit from nearby magnetic fields, loss of vacuum in a breaker, or other switching device malfunctions. But the more common reason is operator error. While many LOTO safety procedures /policies do mandate the use of safety grounding through ground and test (G&T) devices or temporary protective grounds (cable clamps), a further risk comes when the operator installs the grounding cables or G&T device due to the available incident energy. Ground and Test device (nicknamed “the widow maker” for a reason) have their own risks if a mistake is made – grounding the wrong side of a breaker cell, for instance.

If this entire LOTO maintenance process, including grounding, could be done remotely from a safe distance through motor operated devices in a manner that is interlocked with the possible sources, virtually mistake proof, and built-in for readiness, wouldn’t this be a huge improvement to safety during LOTO? This would literally trim the LOTO process time to possibly 3 minutes!

Many switchgear manufacturers offer built-in motorized racking. Presently, remote racking is practiced in many companies. But the final step of the LOTO process – remote grounding – is uncommon. If temporary maintenance grounding could be applied through motor operated built-in ground switches, then the full LOTO process could be designed into the switchgear, interlocked with the draw-out circuit breakers (all sources) and operated outside the arc flash zone away from any risk! Yes, I know what some of you are thinking … In the past, ground switches have not been able to comply with the ANSI MC switchgear standards due to the fully insulated bus requirement. Switchgear Resources inc. has a patented, remotely operated ground switch called “Ground on Command” which is fully insulated during normal switchgear operation. This keeps the C37.20.2 insulation requirement. When a switchgear outage or power system maintenance is needed moving insulated covers open during the operation of the ground switch to allow for grounding circuit. This ground switch also has fault-making capability. Even if someone could make a mistake, all personnel are safe! Just look for the closed ground switch through the window before removing the switchgear cover. If it is grounded – it is safe.

If all the sources were interlocked for proper operation of the grounding devices, operated from a remote-control panel with key operated switches as shown on the picture above, LOTO would be easier, faster and safer for an electrical outage. You can see how pre-engineered maintenance safety built into the system could nearly eliminate the risk from LOTO mistakes. This process still maintains the checking for the presence of voltage through built-in voltage dividers (less than 50VAC at the ports. The visible break rule (circuit breaker racked out) and visible grounding give the assurance before removal of any MV compartment cover. See the link below for a typical process. Absence of voltage indication could also be used. The 15KV ground switch fits compactly in the cable compartment or other preferred locations.

Special thanks and acknowledgement to Jim White for his articles and activism that have advanced the safety of grounding.