Line 3 goes down far too often, and the cause is nearly always “fried electronics.”
The plant manager has personally taken control of this issue, due to the loss of revenue from lost production. But he tells you he’s confused. First, the solution was a bigger Surge Protection Device (SPD) on the branch circuit panel. That didn’t solve the problem. Now the recommended solution is a smaller SPD.
He wants you to sort this out. Where do you start?
The plant manager isn’t the only one who’s confused. It really isn’t possible to select the “correct” SPD for that panel to solve the problem. What you need to do is begin with these three steps:
1. Select and install the correct SPD at each energy level of power distribution, cascading downward as the distribution goes from the service entrance to the feeder panel, branch panel, and final load. You need coordinated SPDs at each of these levels.
2. Look at internal sources of energy spikes. For example, large motors that start across the line. A soft start or motor drive solves that problem.
3. Ensure you have the correct grounding, bonding, and return path configurations. See IEEE-142 and Art. 250 of the NEC.
