Is there an arc flash hazard when installing a remote racking device when the breaker is racked in?
Here is a question asked recently:
Is there an arc flash hazard when installing a remote racking device when the breaker is racked in? Right now we require FR suits. The employees want some relief from that.
Similar questions like this are asked in many of our classes. Hugh Hoagland, arc flash safety expert, responded to this particular one. He said interacting with equipment (or having to open doors or covers) is considered an at-risk situation. In this particular instance, the job will most likely require arc-rated (and possibly shock) PPE.
Looking at Remote Racking
During electrical safety training classes, our instructors are often asked whether arc-rated PPE (e.g., flash suit, daily work-wear) is required if remote racking takes place.
Racking is the process of mechanically separating (or connecting) an electrical switch (circuit breaker) from the electrical system. It establishes a physical gap between the energized part of the circuit and the load for the complete isolation from the energy source.
Racking also facilitates testing, replacement or repair of a breaker without the need to disassemble other components in the electrical system (such as a Motor Control Center or switchboard).
Racking is achieved through multiple methods. Vertical racking medium voltage breakers normally provide an “UP” / “DOWN” button located adjacent to the breaker. Most medium voltage breakers and low voltage air circuit breakers rack horizontally using a wheel wrench (spanner) type tool. With these older technologies (or baseline models) the operator must stand in front of the breaker to rack. This places the workers inside the arc flash boundary and shock boundary in most instances.
Earlier rudimentary design changes saw the operators welding extensions to these wrenches to increase their working distance. Soon afterwards, multiple solutions hot the market. Motor operated racking devices were provided with a receptacle (outlet or plug) that facilitated racking and switching from the end of a very long cable. Mechanical devices containing a racking motor “plugged” into horizontal racking breakers or “fitted” over a pistol grip switch soon became the mainstay in many plants.
If these devices allowed the workers to be outside of the arc flash and shock boundaries, what do the standards state about personal protective equipment?
If the worker is outside both the arc flash and shock boundaries, then no PPE for electrical hazards are required. The organization should be careful, however, as there have been problems while racking that required immediate action to prevent a serious incident. If the worker needs to encroach either boundary for any reason, the appropriate PPE must be used.
The second consideration is that while plugging/unplugging/installing/removing (etc.) the racking device, the operator is interacting with the breaker. NFPA 70E(R) Article 100 states that interacting with equipment increases the likelihood of an arc flash. If the worker is at risk of injury from an arc flash, then arc rated PPE must be used. Generally, shutters will cover energized parts from the worker, but if energized parts result in the worker entering the restricted approach boundary then shock protection will be mandatory.
Each situation is different, and a risk assessment should be performed with careful consideration to the “interaction” and “exposed to energized parts” of this operation.
Although we do not promote any particular product or brand, the following video demonstrates a preferred practice in terms of PPE (see time frame 1:45 to 2:00).
Best Practice Moving Forward
Remote racking and other remote operating solutions are definitely the way forward.
This article aims to emphasize the ideology of always assessing the risk; even when solutions appear to be perfect, there are always caveats or rules that should be considered.
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