Data Center Journal

Volume 28 | August 2013

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Standardized equipment is also recom- mended as part of the initial design and any expansions. For example, draw-out equipment can be exchanged between compatible switchgear. However, if multiple types and manufactures are utilized, the equipment will not be as versatile. The operating environment plays a key role in determining the reliability of a data center's power system. Equipment rooms should have clean, filtered air with very low levels of vibration. tionality. If an external source of power is required, the plan should detail the source of the temporary power. A vital outcome from inspection and testing should be accurate and complete records. Based upon the inspection and testing results, repairs should be prioritized and scheduled. Equipment that is either close to breaking down or vital to a critical load should receive top priority. All work should be performed by qualified personnel as defined by OSHA and NFPA 70E. Grouping equipment can maximize ef- TYPICAL DATA CENTER POWER DISTRIBUTION EQUIPMENT ELECTRICAL PREVENTIVE MAINTENANCE AND TESTING PROGRAM Medium-voltage transformers are some of the most critical components in a power system. They can cause drastic service interruptions and can take weeks or months to replace if they fail. In addition, they are also one of the most expensive components in a power system. ficiency during maintenance and reduce downtime. Stage all personnel and locate all test equipment in one part of the facility. The three parts of an effective preventive maintenance and testing program are inspection, testing, and repair. Each part is vital to the program's overall success and it is important to tailor each part around the operations and critical nature of the facility. Prior to the inspection phase, updated drawings and diagrams must be obtained, along with applicable manufacturers' operation and maintenance manuals for the equipment. Without this documentation, the inspection could be incomplete, inaccurate, or unsafe. Only after the energy sources have been locked-out/tagged-out, equipment has been verified de-energized and proper grounds have been applied (if applicable), can the inspection begin. Detailed inspection activities should be planned prior to the shut-down so time is not wasted. Both equipment age and the operating environment should be taken into account and maintenance should be performed by qualified personnel. Testing will also be unique for each type of equipment and it is important to refer to the manufacturers' operation and maintenance manuals. Detailed planning is also critical in this phase of the maintenance and testing program. Prior to the shutdown, testing equipment should be available and tested to ensure proper func- www.datacenterjournal.com Medium-Voltage Liquid-Filled Transformers Newer liquid-filled transformers can contain mineral oil, seed oil (less flammable), or silicone fluid. A visual inspection should be part of routine maintenance. This will consist of monitoring the load current, voltage, liquid level, liquid temperature, winding temperature, ambient temperature, and any fluid leaks. During a shut-down, insulation tests such as power-factor testing and insulation-resistance testing should be performed. Instrumentation and protection (gauges, sudden-pressure relays, etc.) should be checked as well. Diagnostic tests such as turns-ratio testing and excitingcurrent testing should also occur. Fans, relays, control power, control power wiring, etc. should be inspected along with the general condition of the enclosure. Bushing and surge arrestor should be cleaned and loose connections tightened. The transformer should also be checked for pressure and bushing leaks. Medium-Voltage Dry-Type Transformers Ventilated and cast-coil dry-type ANSI/IEEE C57.12.01 medium-voltage transformers are another option to liquidfilled. During the shut-down, dirt and debris should be removed from the core, coil, and insulators. Special care should be made to insure air flow is not impeded. Loose connections should be tightened. Insulation-resistance testing, turns-ratio testing, and core Megger tests should also take place. Medium-Voltage Metal-Clad Switchgear During a shut-down the busbars, supports, and insulating barriers should be inspected and cleaned. The busbars should be tightened to manufacturer's specifications. The interior should be thoroughly vacuumed and adequate ventilation verified. All parts should be inspected for signs of corona, tracking, or thermal damage. Cable terminations should be inspected for insulation deterioration. Space heaters should be tested, if present. Once the circuit breaker(s) have been withdrawn, the moving mechanisms in the compartment should be inspected. The shutters should also be inspected and tightened. Primary contacts should be inspected for signs of loose hardware or poor contact with the circuit breaker contacts. All contacts and joints should be lubricated per the manufacturer's specifications. Parts in the VT and CPT compartments should be inspected, cleaned, tightened and lubricated. Surge arrestors, interlocks, and battery systems should be checked and maintained per the manufacturer's specifications. Medium-Voltage Circuit Breakers Most new installations will have vacuum circuit breakers. Before being maintained, these circuit breakers should be completely withdrawn from their cubicles and inspected for signs of overheating, excessive dirt or moisture, and loose parts or connections. The operating mechanisms should be snug and friction free. Both the insulators and the vacuum interrupters should be cleaned. The draw-out primary contact clusters should be checked for signs of wear or damage. To check the vacuum interrupters against the manufacturer's specifications, the following tests should be performed: contact erosion, hi-pot (dielectric), and resistance measurement tests. It is highly recommended to have spares of each amperage size and manufacturer available, in case of equipment breakdown. Protective Relays Electronic relays are designed to be maintenance-free. However, like all other components in an electrical power system, harsh operating conditions could dra- THE DATA CENTER JOURNAL | 7

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