The argument in favor of preventive maintenance programs is elementary. Scheduled outages are almost always less expensive than unscheduled outages, and the law of entropy states that all machines and all systems will eventually fail.
Nevertheless, preventive maintenance is not easy to sell to managers who have not experienced a catastrophic equipment failure, or who are not aware of the financial impact of unscheduled outages in their facility. More often than not the best you'll be able to do is to get the facility manager to allocate funds in "next year's" budget. It makes good sense to present a comprehensive program flexible enough to adapt to virtually any type of facility, and any type of budget.
Service entrance equipment, distribution panels, transformers, feeders, motor control centers, and branch panels are serviced best under preventive maintenance programs. UPS systems, standby generators, etc., usually maintained by factory trained technicians on service contracts, can also be included under a comprehensive program coordinated during the scheduled maintenance period. The cost of this coordination should be included in your preventive maintenance proposal. You can always offer a credit if no coordination is required, but it's difficult to recoup those costs after the fact.
Let's assume your maintenance program involves working with commercial office space, whether single or multi-tenant. Prior to shutting down any facility, the manager must poll the tenants (or departments, in a single-tenant facility), to determine if any special measures are to be taken to avoid disconnecting a critical load during a scheduled outage. Industrial facilities will vary to a slight degree, and 7-day, 24-hour facilities (Data Centers) require more complex planning, but should have some level of redundancy that will allow the critical loads to function during any outage.
Although preventive maintenance programs are generally thought of as scheduled outages, they are better performed in two distinct phases: operational and shutdown.
Operational plan Perform a thermal scan of all equipment under normal load conditions. This service is generally contracted to companies specializing in thermal scanning and will point to specific areas within the distribution system that may require more attention than others. A thermal scan will also help determine specific repairs or replacements that can be accomplished during the maintenance outage.
Develop load profiles. Depending upon the amount of time and money available, each load (from service entrance through distribution panels and MCCs) should be monitored with a recording meter that will read voltage, current, and harmonic content. The record should contain at least a week's worth of information for each circuit monitored. The information gathered will be useful in pinpointing areas of potential problems, such as future overheating in non-k-rated transformers, and will assist in the decision-making process if additional loads are anticipated. It will also serve as a baseline measurement for power quality in the deregulated utility environment, which will eventually become a reality throughout the country. If time and money are not available, at least try to monitor the service entrance equipment.
At this point, the operational phase of the preventive maintenance program is complete. All the gathered information should be reviewed and utilized in creating a plan for the next stage.
The shutdown phase Obviously, the local utility will have to disconnect the facility from the grid at some point in this phase. To determine when shutdown should occur, we must know what portions of the system will be worked on and at what levels. The following items are usually within the scope of an electrical maintenance program:
Circuit breakers. Most manufacturers stipulate that circuit breaker operating mechanisms be exercised (turned off and on) at least once a year to insure they aren't fouled. This can be accomplished when the utility power is disconnected, but another possibility is to test the trip mechanisms while the opportunity is at hand. This function can be performed with a load bank while the utility power is still operational, and can easily be subcontracted to a local testing agency.
It is a good idea to note the manufacturer and catalog number of any circuit breakers critical to the operation of the facility or any important loads, particularly if preventive maintenance has not been performed for an extended time period. Frequently, older breakers will fail to close when they are re-energized, and having replacements on hand will go a long way to enhance customer relations. If the customer does not want (or can't afford) to maintain an inventory of spares, purchase the required circuit breakers from a distributor but agree in advance to a restocking charge, which will become part of the program cost if the parts aren't required.
Distribution switches and local disconnects. All switches, as well as the HOA mechanisms in motor control centers and local garters, should be operated through an open/close cycle. They should also be lubricated in accordance with the manu-facturer's guidelines (be certain to return the motor operator to its original position).
Feeders. While the power is disconnected, the feeders (both distribution and mechanical) can be tested with a megohmmeter to determine their insulation effectiveness. Although this may not be included in all maintenance programs, it is particularly necessary in facilities that experience voltage spikes (insulation damaging) and have high harmonic content. (The higher order harmonics generate considerable heat, which will accelerate the insulation degradation process). Check that all lugs are properly tightened, and look for heat damage at the termination points.
Switchboards and distribution panels. Vacuum interiors, and wipe all bus clean with appropriate solvent. Torque all-bus connection points. Look for bus that might have eroded from arcing between loose connections, or pitting on contact surfaces. The contact surfaces can always be refaced with a mild abrasive, but eroded bus should be replaced at the earliest opportunity. As a precautionary measure, have some spare copper bus bar and additional bolts on the site. Occasionally, bolts will become brittle over time and will amp when torque is applied. Once again, be prepared.
Distribution transformers. Clean and torque all connections and vacuum the interior. If time and finances permit, perform insulation resistance testing on the windings.
The aforementioned items are not always completed. Time and money are always the determining factors in how comprehensive the maintenance program will be. Use this as a shopping list; if time and money allow, expand it to include some or all branch breakers and wiring.
Pricing these tasks can be challenging. In my experience, the safest way to estimate the cost of a program is to first determine the maximum time available for an outage (there never seems to be enough time to do a thorough job in one visit). Secondly, determine the number of areas that can be worked on at one time to determine the crew size. Consider the cost of materials you have to purchase (and the restocking charge for materials on hand but not used), add in your coordination and subcontract costs, sum it up, add your profit margin, and you're ready to make a presentation.
Our recent affiliation with Group Maintenance America Corp. (GroupMac) is exciting in the sense that we will have a menu of maintenance procedures that will available to all of our affiliated companies, as well as the National Accounts that are procured by the main office. [Editor's note: GroupMac, a national contracting corporation, bought Continental in October 1998. See January CEE News cover story]. It is GroupMac's goal to develop and maintain a level of expertise and training among all of their affiliated companies, so that any customer of a GroupMac company can expect and receive the same level of technical ability and service that is available in other parts of the country.