Telecommunications operations depend on electrical testing for uptime and profitability.
Testing is a critical part of building and operating a telecommunications facility. But who should perform the testing, especially prior to startup? Does it make sense to use an unbiased third party testing organization, or is a self-inspection philosophy adequate? That question has been answered in the telecommunications industry with the elimination of the self-inspection initiatives that would have made the electrical inspector obsolete. Smart people know they can’t catch all of their own mistakes.
The complexity of today’s high-availability power systems require “high nines” of reliability, such as 99.9999% uptime or 0.53 minutes of downtime per year. One answer to this is a strategy of component redundancy. The flaw in this approach is that today’s 24/7 telecommunications customer depends on integrated and aggregated systems, not components. A high level of power system reliability may require a high level of maintenance downtime (reducing the overall uptime), unless you integrate a well-designed redundancy with operation and maintenance in mind.
With these sophisticated requirements, you might expect every customer to require a comprehensive and rigorous commissioning, acceptance testing, and maintenance program for the electrical system. But InterNational Electrical Testing Association (NETA) members consistently find that testing is usually an afterthought for most facilities—and often inadequate. Most of the time, the impetus for even the bare minimum of testing is a catastrophic failure. Is such an approach adequate for telecommunication systems required to operate at 99.9999% availability?
Testing standards. The American National Standards Institute (ANSI) recently published standard ANSI/NETA ETT-2000, “Standard for Certification of Electrical Testing Technicians,” which defines the certification requirements for an electrical test technician. The standard requires an acceptance-testing program after installation and prior to energization. The acceptance tests verify the equipment operates to industry standards, within manufacturer’s tolerances, and per design specifications. The benefits of reduced start-up costs and improved safety for people and equipment justify the price of acceptance testing. And an additional benefit is the establishment of baseline data for the periodic testing that is an essential part of an effective maintenance program. That alone can pay for acceptance testing several times over just in prevented downtime and/or faster repair if you do go down.
So how do you ensure approval for an adequate acceptance-testing program? NETA publishes the “Acceptance Testing Specification Guidelines” (NETA ATS 1999). Using this as your guide for the testing program you’ve developed, you can make a strong case for its approval.
To use the standard, test each piece of equipment per the applicable testing specification section. The power system requires high component reliability, so include the optional tests. The grounding scheme may require some specialized testing to validate a high-frequency grounding system and a DC grounding system. Studies of maintenance logs and case histories repeatedly show 80% of computer problems are grounding-related.
Perform the commissioning test after you’ve completed the equipment acceptance. This requires an integrated approach combining utility in-feed, standby generation, backup power, distribution system, HVAC/mechanical systems, alarms, and communications. You’ll need to develop a method of procedure (MOP) that simulates every possible operating system configuration under normal and abnormal conditions, including total loss of utility power, simultaneous non-transfer of generator No. 1, loss of UPS No. 2, and so on. Timing of systems transfer, load monitoring and the power quality profile are some of the key commissioning measurements.
The following example illustrates the importance of the commissioning test. A telecommunications facility’s critical space power system depends on the HVAC/mechanical system. The loss of cooling capability could raise the temperature too high and thus trip the UPS. The integrated commissioning approach will evaluate for this possible scenario. As part of the generator test, load banks strategically located in the UPS room will use the heat rejection as a dynamic test of the HVAC system. Temperature sensors will measure the temperature rise. Since the rate of heat rise is enough to trigger the fire protection system, you’ll have to temporarily disable a sector of that system for your test.
Critical space maintenance. The traditional telecommunications facility maintenance program, based on time-directed (TD), failure-finding (FF) and run-to-failure (RF) techniques, is quite inadequate for today’s demands. How do you cure that inadequacy? A widely used document for maintenance testing is the NETA “Maintenance Testing Specifications Guidelines” (NETA MTS 1997). Many insurance underwriters refer to this document as part of good industry practices. The maintenance of a high-availability power system requires a combination of time-directed and condition-based maintenance.
Because of the redundancy built into the system, you can perform some maintenance testing while the load is online. Many people use a time-directed maintenance program. But the big question is, How often should you test the various components of my system?
A condition-based maintenance methodology is more cost-effective. This approach includes leveraging new diagnostic and testing technologies, data mining, and factoring in life cycle operating cost. An increasing amount of electrical power equipment is now available with smart sensors that provide key data on the equipment condition via remote sensing. For example, UPSs and variable-speed motor drives are now available with online and remote diagnostic systems, transfer switches have built-in monitoring and diagnostic logic, and circuit breakers have power profile monitoring capability and trip annunciation. A blend of these emerging technologies with proven techniques in maintenance testing will provide reliable results.
What about telecommunications facility maintenance and power quality? What is a reasonable or acceptable risk? And as far as power quality is concerned, how bad is bad? Power quality problems can vary with system complexities. Often, however, the answer to such questions requires you to go back to basics—the elimination of equipment misapplications and infrastructure problems. Any system in continuous use will have failures, regardless of its design. It’s isolating the failure and repair it quickly that truly determines system availability.
The successful operation of a high availability power system in the telecommunications environment depends on proper commissioning, acceptance, and maintenance testing. Management must have an accurate picture of the costs of an outage, whether planned or unplanned, and this picture must play a key part in the design and operation of a critical space.
Photo courtesy of AEMC, Foxborough, MA