Theory is a wonderful thing. And countless articles of this type spend a fair amount of time on theory versus application of electrical reliability. So, we’ll be different. In this article, we will discuss, based on personal experience, the scope of a basic electrical-infrastructure review and how it can be performed. This real-world approach is based on how we have conducted industrial-energy-assessment walk-throughs.
Surprisingly, initial energy assessments can be quite fast, especially in older facilities. A full assessment takes longer. But because of how much attention electrical systems receive in most facilities from a reliability standpoint, low-hanging fruit findings can usually be identified with a one-to-two-day walk-through.
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The key to a successful walk-through is to ensure that the investigator sees the unseen. This is first accomplished by obtaining single-line diagrams of the electrical system. The facility arc-flash study is a good place to start. That said, the investigator needs to be prepared to verify that a valid (or, perhaps, invalid) arc- flash study has been performed.
For example, in one case, during evaluation of single lines for a facility, we started by looking at the PCC (Point of Common Connection/Coupling) and expected to see specific relays referenced in the official arc-flash study. Those relays, however, didn’t actually exist. That immediately invalidated the arc-flash study, as the purported relays would have been relied for a certain amount of protection.
Luckily, the one-lines in the same study, were relatively accurate, which is better than what we sometimes observe. In effect, one-lines are important for understanding the general layout and guide for a site’s distribution system but should not be relied upon for infrastructure analyses (let alone an arc-flash studies) until they have been “walked-down.”
Depending on the type of facility, I usually look at all meters and subs first, then start from each sub. In a few cases, I may start at each service, then move to each sub, then all the loads associated with the sub, but only when this approach is the more efficient. In either case, these investigations should be performed in a logical top-down manner from incoming power to the loads. A plant drawing and the single line should help the investigator(s) pre-plan the survey.
The performance of the electrical reliability survey starts with a walk-down of the site. This should always start at the PCC, or, when possible, from the local utility distribution center. Understanding the general condition of the equipment supplying the facility becomes more interesting when you also look at what and/or how many other facilities or loads are being fed by that local center.
Keep in mind that any power-quality issues put on that system are being shared among all users of it, depending on the stiffness of the system and any corrective devices the utility is using. At the end-user site, a determination of the incoming services and meter(s) should be completed first, followed by confirmation of how they are connected to the sub(s).
The types and estimated age of the cable to and from the subs should be noted, as should the transformer types and connections. The investigator also needs to verify how the internal metering/monitoring and any relays associated with the sub are connected and if they are accessible. Other questions should be answered: as well What is the condition of the switchgear and are there inspection stickers and arc-flash labels? What type of grounding system does the facility have? Is it grounded? High-resistance ground, low-resistance ground, or floating?
Next, look up. What type of lighting is in use? Has the site made improvements to or upgraded to energy- efficient lighting systems? If attention hasn’t been paid to the obvious, we can expect equipment that is less obvious (or unconsciously ignored) has not been addressed. Now, start looking at the cable trays leaving switchgear and servicing motor-control centers (MCCs) and panels. Are they bundled cables? Are they individual phases randomly set in the trays along with ground leads? Are the cable trays grounded?
Before hunting down individual panels, our preferred approach is to determine the general condition of the MCCs next. At this point, an investigator should also be able to observe a few lockout/tagout (LOTO) applications.
Are LOTO devices used and appropriate practices followed? Are buckets properly bolted in-place, or are they left ajar? With regard to switchgear and MCCs, are there test points for electrical equipment, such as Electrical Signature Analysis (ESA) devices or infrared windows?
Tracing some of the conduit and junction boxes (spot check) to power and lighting panels is the next part of the survey. What is the general condition, are circuit breakers intact or damaged, is everything properly labeled? Missing covers and doors, exposed conductors, and damaged conduit are all serious conditions.
A review of the clearance in front of and beside all electrical panels is also important. For most lower- voltage applications, the clearance is three feet for access and egress. Painting a box on the floor in front of the cabinet, MCC, or switchgear denoting the zone where items cannot be stored is a best-practice option. We have seen plenty of improper storage near electrical cabinets. That included, at one site, propane tanks and other compressed flammable storage placed directly in front of open cabinets.
A tour of the facility to look at loads including motors, lighting systems, and other electrical systems will often result in additional findings. Driven equipment, including air compressors, fans, pumps, etc., should also be reviewed, which, in in the process, can help identify wasteful leaks.
Following a review of a facility, we collect specific electrical data, including power-quality information and ground and neutral values and harmonics. Sample data points are also obtained in to determine opportunity impacts, such as potential energy savings from reliability improvements.
There are several distinct advantages in the investigation of electrical reliability and internal electrical infrastructure. 1) Most improvements can be made inexpensively. 2) Energy savings are directly measurable, not merely calculated or estimated. 3) A majority of improvements will show direct bottom-line simple paybacks measured in days or weeks, usually with minimal investments.
In our next article (Part IV), we will discuss the details related to the review and measurement of data at the PCC or substations and what they mean. This will be followed by details of each of the areas of interest discussed in this article as well as where to go to obtain the references for the studies.TRR
ABOUT THE AUTHOR
Howard Penrose, Ph.D., CMRP, is Founder and President of Motor Doc LLC, Lombard, IL and, among other things, a Past Chair of the Society for Maintenance and Reliability Professionals, Atlanta (smrp.org). Email him at firstname.lastname@example.org, or email@example.com, and/or visit motordoc.com.
Tags: reliability, availability, maintenance, RAM, electric motors, electrical-infrastructure review, energy efficiency, industrial-energy assessments