Electrical Troubleshooting Quiz — June 3, 2025

The plant has been suffering from an equipment failure epidemic. The plant manager fired the plant engineer for letting this happen, then tasked you with fixing the cause of it all. And he told you the cause is poor power quality. He said to buy some power conditioners and engage the services of a power quality consultant if that doesn’t work. How should you proceed?

Answer to Quiz

Sometimes when it’s determined that equipment failures and malfunctions are due to poor power quality, someone decides to “solve” the problem by installing some power conditioning devices. While such devices have their place, it is not appropriate to use them in lieu of identifying and addressing the underlying causes of poor power quality.

The first line of defense when it comes to preventing poor power quality is to perform the necessary maintenance on your bonding system, electronic motor drives, transformers, and motors. Having a qualified person or service respond to power monitor alerts and to routinely read power monitor reports is also part of proper power infrastructure maintenance.

If the correct maintenance is performed, you may still have poor power quality. Some issues to look for:

• Across the line starting of large motors, including any fire pumps. Large motors require a large inrush current to start, and that draw can inflict power quality problems onto every feeder on the same service. If you have fire pumps regularly starting, you can probably fix that with administrative controls. For example, in a Kentucky plastics plant, operators used the fire protection water for routine washing of large production areas. This caused enough pressure drop in the system that the jockey pump could not keep up and the fire pump would start across the line. This was a simple problem to fix (the plant manager said he’d fire the next person who misuses the fire protection system). A solution for other large motors is to install a soft starter or variable speed drive.
• Big power factor drains. Typically, these are large motors. Typically, the solution is to install power factor correction capacitors at the motor. But a power factor corrected, harmonics corrected variable speed drive may be a better solution.
• Voltage imbalance. Motors can wreak havoc on power quality for any number of reasons. Voltage imbalance is one of those reasons. The most common cause is that too much single-phase load is supplied by the same phase. Lighting is the largest single-phase load in almost any facility. This means that if you have voltage imbalance, you can probably move a few branch circuits around to get it to a reasonable level.
• Bonding system connections with high impedance. It’s doubtful you have enough current flowing through your bonding system for these connections to be amendable to detection via infra-red. So how do you find them? Start by looking at the ones that are near sources of undesired current. These would be things like big motors and the power supplies for LED lighting systems. Do you have an IT room? An office full of computers? Robotic equipment? Automatic welder equipment?

If all of these fail to correct the problem, you have a situation that is complex and probably requires a power quality consultant to solve. Before talking with a power quality consultant, do the following:

• Ensure you have a one-line diagram for the premises.
• Make a list of any changes or upgrades that have occurred over the past year. Your power quality problem sources are probably hiding in there. A power quality consultant would know what to look for.
• Use your CMMS to generate a report of all large inductive loads. You want to have a ready answer to the question, “How many large motors do you have?” Exactly what’s large varies, but you could use 100HP as a starting point.
• Make a list of the breakers, by size and type, in each panel at each service.
• Note the location of any power factor correction capacitors, their size, and their apparent condition.
• For each service, feeder panel, and MCC, determine the electric shock protection boundary per NFPA 70E 130.4(E). Your consultant will likely need this information to do things like conduct an infrared survey.
• For at least one of your services, fill out an electrical work permit per NFPA 70E 130.2. This permit process has many steps, and you need to understand each of them. Give yourself this practice run before making any arrangements with a consultant. In the course of working with the consultant, you will probably need to do it for several feeder circuits.

A power quality consultant may ask for additional information, but having the aforementioned already at hand will get things off to a good start.