Zero Energy
Objectives
This lesson walks you through a sample procedure for creating an electrically safe environment when dealing with Low Voltage Circuits (electrical bodies such as IEC and the IEEE differ on the definition of low voltage, but we will use 600V as the threshold).
If your workspace has its own zero energy procedures, you should follow those instead. Ensure that you are always wearing your jobsite personnal protective equipment (PPE).
These steps are divided into preparation (steps you can complete while the circuit is energized) and action (steps that can only be completed while the circuit is de-energized).
High voltage circuits (greater than 600 volts) are a unique topic, and you should receive specialized training to deal with them.
The information in this lesson may not be applicable or complete for a high voltage environment.
Scenario
You are an maintenance technician working for an amusement park.
The Fantastic Futures!!™ ride has a defective component that needs to be replaced, which will require shutting the entire ride down. Let's look at a plan to do so as quickly and efficiently as possible.
Preparation
De-energizing Fantastic Futures!!™ so that you can work safely impacts the day's sales, so minimize the disruption by being completely ready to go when the shutdown starts.
Step 1 - Consider The Circuit
Take a moment to consider the purpose of the circuit that you are about to de-energize.
Having to shut down a large operation (or in this case, a signature ride) for a relatively small amount of electrical work might cost a few ticket sales, but it's the correct procedure. If you try to take a shortcut by doing your work live, there absolutely WILL be a lengthy shutdown if you are injured or killed.
Survey the work environment. Identify all hazards (not just the electrical ones!) in the work area, and any applicable signage.
Verify the accuracy of the documentation that you will be relying on. If you are swapping a component, verify that that you have the correct component on hand and ready to go.
Gather all of the tools and task specific personnal protective equipment (PPE) that you will need, and put your PPE on.
Test your multimeter using a known voltage source to verify that it is working correctly. Because this is a low voltage AC circuit, you can simply use a nearby outlet (120V AC). This confirms that the meter is working as expected.
Action
Now that you have everything in place to work as efficiently as possible, you're ready to begin.
Step 6 - Notify Others
Notify anyone affected that the circuit is about to be de-energized.
Turn equipment off and disconnect all energy sources. Lock out and tag out (LOTO) the the energy source so that it cannot be reconnected, and verify that equipment does not operate.
Verification
In theory, there's no voltage in the circuit at this point. But what if you've overlooked something?
Step 8 - Verify Zero Energy
Use your multimeter to verify that all of the sources that could supply the component are at zero energy.
Refer to schematic - check all of the places where voltages may be present in normal operation. Don't assume that the circuit is de-energized - check and confirm.
