If you’ve worked on transformers in renewable energy circuits, as I have for the past six months, you’ve likely seen many—perhaps most—equipped with electrostatic shields, grounded copper or aluminum sheets wedged between the high- and low-side windings. The existence of these shields inside transformers is normally (but not always) readily identifiable via the unit data plates (Figure 1). Some affirm …
The days of low-voltage breakers being simple devices with basic overcurrent protection are long gone. Back then, the biggest challenge was to figure out how to defeat a ground fault or remember which jumper disabled thermal memory. Today, manufacturers are leveraging digital technology to add layers of protection and functionality. These advancements can quickly derail a routine day of testing …
Asset failures versus time are often non-linear. As assets degrade over time, the degree of degradation and the rate of degradation often increase. If asset degradation were linear, the rate of degradation would be constant. This implies that an asset, such as a circuit breaker, could function properly for approximately 30 years, develop a detectable defect at year 31, and …
No good electrical testing field story starts with “everything went perfectly.” Inevitably, things do not go according to plan. Breakers of all types, makes, and models are the source of great stories and hard lessons learned under pressure to get a circuit back in service. The purpose of this article is to share common issues that fall into a few …
Electrical insulation is designed to keep current from flowing where it shouldn’t. Insulation integrity is therefore critical and is assessed via a battery of tests. Many things can compromise the results of these tests, including temperature, humidity, erroneous test procedures, etc. Previously, I wrote about the effects of humidity on insulation integrity tests. This time I focus on erroneous test …
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Equipment underutilization is, by implication, an underdiscussed subject. I am all too familiar with this phenomenon, e.g., relays with useful but unprogrammed protective functions, calibrated test equipment that rarely sees the light of day, fully functional battery chargers next to pallets of long-deceased 12 V valve-regulated lead–acid batteries (VRLAs), etc. This negligence is no less true of rotating machines, where inexpensive …
In a previous article, I discussed the challenges and the importance of proper cable installation. Here, we turn our attention to the challenges of obtaining accurate test results. These best practices and processes come with a field technician’s ability to be efficient and confident in their test results. I have been around the industry long enough to be present for …
Relay testing has long been one of the more technically demanding and complicated aspects of the business of electrical acceptance and maintenance testing. The plethora of skills required to be an excellent relay technician includes (in no particular order) electrical theory, power system design, AC and DC control drawing interpretation, and the ability to simulate power system faults to name …
Numerous articles have been written about NFPA 70B in recent months following the recommended practice becoming a standard. All this chatter and renewed interest is coming from the perception — and rightfully so — that failure to perform minimum electrical maintenance could lead to OSHA fines. I’d like to believe that facilities that did not previously have an electrical maintenance …