In most facilities, power quality doesn’t get attention until a high failure rate occurs that doesn’t seem to have any other cause. Then it becomes a matter of troubleshooting. By the time you fix the problem(s), transformers, conductors, and utilization equipment (most notably motors and lighting systems) have undergone significant stress and will fail prematurely.
Maintenance practices are generally set up around the idea of maintaining utilization equipment per the manufacturer’s recommendations or per published industry standards. But those tend to assume the equipment operates in a good power quality environment. And yet, maintenance practices are generally not inclusive of maintaining for power quality.
It could be argued that the maintenance department doesn’t have enough resources to engage in power quality-related maintenance. Equipment failures from poor power quality keep them busy, after all. And besides, they don’t possess the specialized test equipment to do this kind of work (even though the plant engineer has unsuccessfully made several purchase requests for it).
One way to start addressing this problem is to install a power monitor. However, it needs to do more than monitor the power at the service. It needs to be connected such that it monitors each feeder from each service panel, plus each large motor, plus each critical load. Those large motors are where you are going to see load-generated transient power events come from, so those also need to be alarmed rather than just logged.
A power monitor isn’t going to solve everything, though. Here are some power quality maintenance practices that seldom get implemented but you should consider:
- Temperature monitoring on dry-type transformers supplying critical equipment or large areas of the facility. A local indicator might be OK, but if it’s all you have, people will walk right past it without noticing something is wrong. You need an alarm function.
- Mechanical integrity inspections of equipment grounding conductors (EGCs). Nobody inspects their conduit or EMT, right? They should if the raceway is being used as an EGC (and it should be used as an EGC due to its large cross-sectional area and consequent ability to handle high frequencies). This can be done an area at a time over the course of a couple of years.
- Visual inspections of service and feeder conductors at the termination points. This can reveal things you would not otherwise be aware of. For example, if the insulation appears to be swollen, melting back, or discolored, further investigation is needed. Performing these inspections at the same time thermography is performed will reduce the number of times covers must be removed or doors opened. The thermographer’s job is already complicated enough; assigning a second person to perform this inspection (plus help with all those covers and doors) is a wise move.
- Analysis of motor overload replacement or reset records. If motors in a given area of the plant have had more overload strips (heaters) replaced or more thermal protection devices reset than in other areas, a power quality analysis should be performed. It’s not just load issues causing overload devices to open. You could have a voltage imbalance situation, and moving a couple of lighting circuits to different breakers might be all that’s needed (less lighting load on the overloaded phase, more on the underloaded phase). If your CMMS is robust enough, the analysis could be done by the CMMS automatically and a notification automatically generated.
- Put the analysis power of a power monitor onto important branch circuits. You can do this by scheduling preventive maintenance using a portable power analyzer to manually look at the condition of power on those circuits. Or tie them into the power monitor to eliminate yet another task that maintenance must shoehorn in.
