Reaching zero energy state for an electrician is a little more complex than a regular old lock-out. There are some very important steps that need to be added to the process in order to ensure you can safely touch the conductors with your bare hands.
But first, let me go through an example as to why we need those additional steps.
Imagine you have been assigned to change out motor 123 and the first thing you are going to do is lock it out. Following your lock-out procedure you bump the motor to prove that you have the right one, then you throw the disconnect, apply your lock and tag, and then go back to bump the motor again. This time, it doesn’t do anything so you are satisfied you have it properly locked out. And you do according to a basic lock-out.
But basic lock-out is not for electricians.
What you don’t know is that one phase of the disconnect is stuck in. There is still voltage present at the motor pecker head… the next step for changing out the motor is to remove the pecker head and cut the tape off of the motor leads, the same motor leads that are still energized… without any additional steps in your process, you will never figure this out, and... you can fill in the rest of the story.
In this case, the step that was missed was testing. Digging out your multimeter and testing each phase-to-phase and phase-to-ground to ensure there is no voltage present.
So that’s just one example of why lock-out procedures need to be enhanced when it comes to electricity and that’s where CSA has coined the term “establishing an electrically safe work condition”.
Let’s take a closer look at each step.
Step 1. Determine all sources
Sometimes the panel or junction box you are working in has multiple sources of energy. Maybe it’s a 600V motor control bucket that also has 120V control wiring. Maybe it’s a 4160V switchgear assembly that is fed from a transformer and a diesel generator (usually through a tie breaker).
Whatever it is you need to make sure that before you expose the conductors you have consulted single line diagrams, labels, signs, tags, and manufacturer prints to ensure you know what is inside the panel.
Step 2. Open the disconnect
Make sure to always interrupt the load first, failing to do so will put unnecessary stress on your disconnecting device and increase the risk of it failing during operation. Once you’ve got the load removed then simply open the disconnect (nothing you wouldn’t do during a basic lock-out yet).
Step 3. Visually verify
This isn’t always possible. But, if you are able to it’s a great idea (and may have prevented the incident in our example above). Take a look inside the viewing window of the equipment to check that that all blades of the disconnecting devices are fully open. If you are working with draw-out-type circuit breakers, then make sure they are withdrawn to the fully disconnected position.
Step 4. Lock-out
Put your locks on. Tag it and move to the next step.
Step 5. Test before touch
This is the most important step! And within this step, there are a few important considerations.
Make sure you choose the appropriate test instrument for the job. I can’t stress this enough. If you don’t believe me then watch this video.
Before you test the circuit you’ll want to make sure your tester is working properly on a known source, maybe the control circuit or a lighting panel.
Test each conductor both phase-to-phase and phase-to-ground.
Then verify your tester is still working by going back to your known source.
Step 6. Apply temporary protective grounds
Another very important step that often gets left out is applying temporary protective grounds.
There are a few reasons you will want to do this:
- induced voltages
- stored electrical energy
- accidental re-energization
- conductors may come in contact with other exposed energized conductors
If any of these possibilities exists, you will need to install temporary protective grounds before you can safely say the system is at zero energy state. Just make sure they are rated for the available fault duty.
Lock-out vs Establishing an electrically safe work condition
So now I hope you can see that just following a standard lock-out procedure is not enough when it comes to electricity. Take the necessary time you need and go through every step listed above in order to establish an electrically safe work condition before carrying out your task.
I hope you found this article useful and if you did please share it using the social media buttons at the bottom of the post!