Ten Tips for Power Assurance

Clean, reliable power seems to be more evasive than ever. Are there guidelines to follow that can ease the problem? The following tips address only some important considerations for assuring power availability. However, they made our top 10 list because they're commonly ignored fundamentals you need for success. They may even cover an important idea you hadn't considered. Unless you apply them correctly,

Clean, reliable power seems to be more evasive than ever. Are there guidelines to follow that can ease the problem?

The following tips address only some important considerations for assuring power availability. However, they made our top 10 list because they're commonly ignored fundamentals you need for success. They may even cover an important idea you hadn't considered. Unless you apply them correctly, even your most high-tech solution is just a shot in the dark.

(1) Watch your documentation. Too often considered an expensive low-value add-on, documentation is the foundation for assuring your facility of clean reliable power. Documentation means far more than a one-line; that's like saying to build a Formula-One dragster, you need more than a sketch that shows a frame and four wheels. You can choose from any of dozens of excellent software packages. Whatever system you ultimately develop or whatever software you use, your documentation must have these features:

  • Is easy to access and update;

  • Accurately provides all necessary information for safely isolating power sources; and

  • Provides all necessary information for locating, identifying, operating, evaluating, maintaining, and replacing every electrical device in the system.

(2) Make your design and layout measure up. If you are starting from scratch, lay out your major runs with the various power levels as far apart as possible. Run the highest distribution voltage you can, for as long as you can. Locate major electrical gear near natural sources of light, but not so near as to be exposed to the elements. Have lights over one switchgear fed from a dedicated line run from another switchgear, so you can shut switchgear down for maintenance without needing to string 500 ft of 120V extension cords through the facility or run portable generators.

If you're looking at an existing facility, check for the number of extension cords and how people use them. Presence of a "permanent" extension cord indicates the need for a hard-wired receptacle. If you eliminate 50 extension cords, you eliminate 50 voltage drops. These cords work extremely well for portable equipment and temporary connections, but their manufacturers do not intend for them to serve as permanent wiring, and neither does the NEC.

Look at your infrastructure. How about mounting pads? If new, are they heavy enough and mounted on the right soil base? If pads already exist, do you see any cracks? Do you notice bent or rusted hangars or beams? If you are adding equipment, do you have the proper flooring or other structure to support it? You need to look at the physical support for your power system.

You also need to look at ingress, egress, and access in case you need to move heavy equipment to and from a location where you're doing repair or maintenance. For example, if you have an overhead door located only 20 ft (along a wide aisle) from a set of switchgear, you don't have to lug test equipment or switchgear enclosures through a crowded facility.

Here are some other ideas. Suppose you have a process cooling tower outside an overhead door. Where are you going to run bus? Keep in mind: A stiff breeze can blow that coolant mist right into the building. Locate bus away from such sources of trouble. Similarly, don't run bus directly over furnaces. If you are adding bus to an existing facility, have a thermographer show you the cooler areas (where process heat does not accumulate) in the building. Try not to run bus along major traffic routes: You'll be the "bad guy" when you block off a major traffic route to work on the bus. You know what happens then. You have to do the work over a holiday weekend or in spurts consisting of a series of half-hour lunch breaks. If you locate bus over equipment (like a large punch press) that requires tall lift trucks for in-place assembly/disassembly or removal, you have to shut the bus down every time maintenance needs to move that equipment. And it's a given that somebody will crush the bus sooner or later. Do not run bus over a storage cage or receiving area. If you do, you tempt people to stack boxes against it, and they invariably give in to temptation.

Finally, you should filter all design decisions through the NEC. While the NEC is not a design manual, following its recommendations is the first step in good design. It's also a good resource for learning the fundamentals of a given subject area before progressing much into the design phase. For example, you may not be familiar with surge arrestors. So turn to Art. 280 and begin reading. You find out you're supposed to use the shortest possible conductor to connect the surge arrestor. This means you must change your plans that locate all surge arrestors in a special room. It's always nice to know these things before you erect walls and run wires.

(3) Symphonize equipment and loads for harmony, not harmonics. This is where you really need to step back and ask yourself how seriously you're taking the idea of consistency and compatibility. How will, or do, the loads interact with each other? Do you have motors with different winding configurations on the same branch circuit (some configurations are incompatible with others: contact your vendor)? Do you have lights and computers coming off the same panel? Do you have production equipment and convenience receptacles on the same branch circuits? Do you have the power to your automated phone system coming off the machine shop transformer? If you answered yes to any of the last four questions or don't know the answer to the first one, your power quality and reliability are not what they should be. Have you looked at the existing loads for inconsistencies? Of course, we know you wouldn't put a bank of 300-hp air compressor motors and your computer room on the same service transformers. But did somebody else do that before you came into the picture? Do you have documentation that accurately shows the present configuration?

Have you analyzed your loads and decided to add power factor correction at each load? Good for you, but did you err on the side of too little correction or too much? If you overcompensated by "just a little," you now know where that smoke smell is coming from. Adding too much capacitance is a common error, and a common cure is to blame harmonics and add even more claptrap to the circuit!

What about starting sequences? Do you have large inductive loads and maybe some electric furnaces or melting pots running off the same service transformers? How do you stagger these loads? You must look carefully at your process. Typically, you'll need to stage-start the heaters first (heating systems normally draw less current as you approach the operating temperature). If you attempt to start the motors at the same time, you may seriously lower the available voltage and, thus, increase the required starting current. A solution is to automate starting, perhaps with PLC control. Exactly how you do this is process-dependent. If you'll need the motors right away and the heaters can wait, then you'd start the motors first.

(4) Defend your protection devices. Ever run a fault analysis? Do your branch circuits have protection that correctly matches that of your feeders, or are you allowing your feeder breakers to operate on a fault before your branch circuits? Did you coordinate your circuit protection? Do you even know what all your circuit loads are and what protection they need? Have you reviewed NEC Art. 240?

Do you perform routine inspections of major protection devices? For example, do you visually check the enclosures for foreign matter, insects, or rodents? Do you inspect gaskets, seals, and paint? When is the last time you checked electrical connections and terminals? What about predictive maintenance: items like thermography, infrared scans, and breaker testing? Do you check voltages at peak load times? Do you have any remote monitoring/alarming devices to warn you of impending failure?

Let's go a step further. Do you keep the correct spares in stock? If you don't, you run the risk of emergency substitutions with the wrong fuse or breaker. Such "rescues" have a bad habit of resulting in catastrophic damage to both upstream and downstream equipment. Protective devices aren't always cheap, but it's cheaper to keep three $85 fuses in stock for 10 years than it is to replace a factory ignited by melting copper wires or exploding transformers.

(5) Learn how to administer training. Do you have a training matrix? That is, have you assessed what critical skills your electricians (whether maintenance or construction) need? And then, have you identified what skills they have and what skills they need training for? Are you looking ahead to training on equipment that has not yet arrived on site (or do you wait until technicians prove, in a crisis situation, they need certain training)? All too often, training is a helter-skelter affair. Using a database, spreadsheet, or dedicated software package, you can track your team's training needs and fill in the holes. A common mistake is to send your star person to as much training as your budget allows. You should spread the training out among various individuals on various shifts. This way, you have more flexibility in case of multiple malfunctions or projects.

Another common mistake is to send the supervisor to training, and then have the supervisor train the workers. This is like washing only the trunk lid of your car and saying the runoff of soap and water makes the rest of it clean. Typically, what happens is the supervisor does not pass the knowledge on to the workers or passes it on incorrectly. You get much more bang for your buck when you leave training to trainers and supervising to supervisors.

When you build a training matrix, focus on the core skills first. Over time, your matrix should include training on related subjects. Those subjects should include welding, lubrication, supervisory skills, machinist basics, hydraulics, and pneumatics. If you offer periphery skill training on an "if you are interested" basis, you promote the development of those individuals who want to excel.

(6) Program a CMMS. A Computerized Maintenance Management System is the bedrock of an effective maintenance organization. The June 1997 issue of EC&M covered how to select a CMMS, on page 48. The March '98 issue article, on page 42, told you more about what a CMMS is and what it can do for you. If you're not familiar with a CMMS, then for now just understand this database-centric tool does the same tasks the paper method requires. The difference is: The paper method leaves the bulk of these tasks undone (or done poorly). If you don't have a CMMS or an enormous maintenance staff that doesn't mind inefficient assignment of work, then you can forget reliable power.

Why such a strong endorsement of a CMMS? It forces you into a mode of addressing the most important tasks first, rather than reacting to personalities or the whims of the uninformed. Given the vagaries of a paper-based system, it's likely that last category could embarrassingly include you if you rely on a low-tech approach like paper. The CMMS gives you the ability to track which failures are the most common or most costly, what causes them, and when they happened. It gives you the ability to assign a job once without sorting through reams of paper.

(7) Look forward to predictive maintenance. Thermography, vibration analysis, breaker-testing, and load monitoring are just some of the tools that prevent catastrophic losses. The more information-intensive and automated your predictive maintenance, the better. What happens when an air compressor motor's vibration level begins drifting outside its baseline profile? Are you going to know about it and be able to replace the motor in time? Or are you going to let the 200-hp motor seize up and drop out a branch circuit (or feeder, if you don't have your protection set properly)? You need to take actual wear and tear measurements, and you need to take them in real time.

You can feed the results of predictive maintenance measurements into a spreadsheet or database, and then plot trend lines. Add in control points, and you now have a quantified method of triggering preventive maintenance action. You can tie these trend line triggers into your CMMS, which can then spit out a preventive maintenance work order. You can add an algorithm to your spreadsheet formula, so you trigger on rate as well as magnitude. For example, let's assume you have a thermocouple sitting in a molded case breaker. Of course, you'd want to take a look at that breaker if it gets to, say, 140 degrees F. But wouldn't you also want to be alerted if that breaker sees a 30 degrees F temperature rise in 15 minutes? This sounds like a useful thing to have, but it's cumbersome to adapt a spreadsheet/database approach to this task. Certainly, not everyone has the time or knowledge to develop complex spreadsheets for this purpose. And you won't have someone constantly available to measure and then punch the data into a spreadsheet. The solution is to buy dedicated monitoring devices. When they send an alarm, you bypass the electronic scheduling altogether; instead of using a work order to issue work, you use a work order retroactively to account for work done. A key factor in your choice of technologies is the frequency of inspection. If you're looking for gradual deterioration, a spreadsheet/database approach is good. If you want monitoring in any mode approaching real time, you need dedicated monitoring devices.

(8) Repair your preventive maintenance program. Traditionally, this means doing invasive procedures on holiday weekends, so you can say you did them. Whether the equipment actually needs any maintenance is beside the point. A newer way of thinking, which has been catching on since it emerged in the late 1970s is Predictive maintenance measurements drive preventive maintenance activities.

A hybrid method combines the best of both of these methods, and the best CMMSs incorporate it. That is, you modify your calendar method based on trends or a Pareto analysis of actual performances in your facility. This assumes you can take the equipment out of service when necessary. For a task like annual breaker testing, you need to schedule all the breakers due that period (annual may mean several batches at various times throughout the year, instead of all at once). However, you also need to allow your predictive maintenance to drive additional testing on an as-needed basis. Let's say you are testing Equipment Group 7 over the Fourth of July. Your last thermographic scan showed hot spots on two phases of a breaker in Group 5, not due for testing until Christmas. Well, you'll just have to add those two breakers to the Fourth of July list. If money is tight, you can look at the thermographic records of Group 7 and swap the two best Group 7 breakers for the "sick puppies" in Group 5. Over Christmas, you do those two Group 7 breakers you didn't do over the Fourth.

Now let's back away from this picture for a moment. How do you decide which PM tasks to do to what equipment? First, make a master equipment list, preferably in a database format (which a CMMS does automatically). Then, rate the equipment in terms of its priority. Maintaining your fire pumps will come before maintaining auxiliary production equipment. Then you look at root causes of equipment failure, preferably by Pareto analysis. Those causes that cost the most are the ones you need to eliminate. Design your maintenance tasks accordingly.

(9) Calculate your additions and keep degradation out of your upgrades. "Nobody's going to miss a little juice off C-phase here. I think I'll just tap in here for that feed to the fan," said the maintenance worker. But when he opened the panel he exclaimed: "Oh, it looks like 16 other people had the same idea. I wonder why nobody put it on the drawing?" Sound familiar? This is one of the major causes of poor or unreliable power. You must orchestrate every change to the distribution system as though you were conducting the Boston Symphony. No sour notes or random playing allowed. How can you coordinate circuit protection, when you don't know what your circuits are?

B.J. VanCleave is a project manager for the same industrial service firm employing Webb Kee (a contributor to EC&M). VanCleave is based in Jackson, Tenn., but travels the nation and sees this problem of undocumented circuits everywhere. He calls it "creative engineering." By that, he means this type of engineering needlessly creates expensive and destructive problems! Upgrades often become degrades.

The main cause of this creative engineering is impatience. Second is lack of adequate drawings. People are typically impatient because "Plant Engineering is too busy fighting fires" to add in a receptacle. Those "fires" are there for a reason, and that reason is usually due to the kinds of preventable problems discussed in this article.

(10) Solidify your grounding. Here's something you may not have considered. Delta-wye transformers block the flow of zero-sequence current between systems. This means you must ground at each voltage level, or you're going to have circuit protection problems. You can ground each voltage level at the neutral lead of a generator, power transformer bank, or grounding transformer. Make sure you ground at the power source, as opposed to the load, and that the transformers or generators you ground to always connect to the system (or you'll have intermittent problems).

Whether you have sensitive loads or not, your system must conform to Art. 250 for safetyreasons. If it does not conform to Art. 250 and you have sensitive loads, it's quite likely you are exposing those loads to "bad power." You can go beyond the specifics of Art. 250 by, for example, running larger ground wires, more bonding conductors, or larger grounding electrodes than it calls for. Don't get carried away, though. You do have a budget to operate with, and if you spend all your resources blindly exceeding Art. 250, you will be unable to give other areas the necessary attention. Besides, it's easy to second-guess the physics in grounding and be wrong. For example, you might decide to double up on your ground rods. Guess what? Putting ground rods much closer together than the distance of the rods laid end-to-end (20 ft, if using 10-ft rods) actually increases resistance to earth ground (due to the shell effect).

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