Often, safety experts get deep into deliberation about methods for keeping people safe. Policies, procedures, and requirements start getting thrown around the conversation like they are going out of style.
Eliminate the Hazard
When it comes to protecting employees from electrical hazards, the simplest and most effective way to do so is to get rid of the danger in the first place. In the electrical safety world, this means establishing an electrically safe work condition, or ESWC.
However, as with most aspects of safety, establishing an ESWC is a process. Qualified persons need to understand the ins and outs of this process from beginning to end.
Components of Establishing an Electrically Safe Work Condition
At a very basic level, there are three main components to an ESWC: Turn the power off, take action to ensure it can’t be turned back on, and verify zero voltage exists at the point of work. Of course, this is a bit of an over- simplification, but, in essence, an ESWC is not a complicated idea.
What gets folks wrapped around the axle is what goes into the process of establishing this safe work condition. Let’s take a look at each of the three main components and how to apply the complex processes and procedures that go into them.
First, let’s look at turning the power off. NFPA 70E® Standard for Electrical Safety in the Workplace contains the steps for establishing and verifying an ESWC in section 120.5. There are a total of eight steps in the process. Four of them deal with turning the power off.
In order to make sure we remove the power, we need to first verify where the power is coming from. Consulting up-to-date risers or one-line diagrams helps us determine all possible sources of power. Once we know where the power is coming from, we can isolate the equipment to be worked on.
Start by shutting down the load on the circuit by using the usual control methods. This is important, as not all isolation equipment is rated for opening the circuit under load. Once the isolation devices have been opened, the next step is to visually verify that the isolation blades have indeed opened up.
Important note: this is an “if possible” step in the process. We should not be trying to perform this step if doing so exposes employees to hazards unique to the process of visually verifying the open condition. For example, it IS possible to open a safety switch and remove all of the guarding to access the blades. However, doing this potentially exposes employees to additional hazards and is not a good idea. Besides, we are going to electrically verify zero volts in a little bit anyway.
The last part of removing the power from the circuit is to release any stored electrical energy by bleeding off any capacitive charge. This isn’t to say go and try to short out the building’s energy storage system, but often there is energy stored in capacitors or even just a built-up charge in the wiring materials themselves. This needs to be removed; otherwise, the employee can receive a significant shock depending on the system design.
First off, we need to relieve any stored mechanical energy that has the potential to re-energize the circuit. A lot of electrical equipment use springs to close contacts; we need to ensure the springs are not in the charged state that could close the contacts unexpectedly.
Then we can administer a lockout/tagout (LOTO) procedure in accordance with an established LOTO program. We won’t go into the specifics of what a LOTO program must entail, but keep in mind that an ESWC is not considered established until all requirements in Article 120 have been met as well, as the OSHA standards for control of hazardous energy.
The last step in ensuring the circuit stays off is applying temporary protective grounding equipment where there is the possibility of induced voltage or it is anticipated that the deenergized conductors might contact other energized conductors. However, temporary grounding is only applied after the verification of zero volts.
This leads us to, arguably, the most important component in establishing an ESWC: verifying the absence of voltage. Using an adequately rated test instrument based on the system being tested, we must verify zero volts phase-to-phase on all phases, and phase-to-ground between all phases. We must also verify proper operation of our test instrument before and after the verification of absence of voltage. An ESWC does not exist if we haven’t made this verification test!
Critical to Safety
Understanding exactly how to place electrical equipment in a safe state to work on is not only critical to safety, but also the priority of NFPA 70E® and OSHA. Part of being a qualified person is knowledge of this process and when it is required. In the next installment of this series, we’ll take a look at exactly what defines a qualified person and how employers can make this determination.
Until then, stay safe, and remember the priority must be to always establish an ESWC when working near exposed electrical hazards.