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EDN ACCESS ARTICLE: DESIGNING A NEBS-COMPLIANT POWER SYSTEM
A complete power system guarantees the problem-free operation of telecommunications equipment and that equipment's compliance with applicable standards. Designing the complete power system requires expertise in areas beyond power conversion. [HTML]

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Designing a NEBS-compliant Power System - SMH4804

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NEBS: An Historical Overview (continued)

NEBS criteria are rigorous and formidable, but they are not monolithic. Designers have considerable latitude in how they meet certain criteria.

In addition, telephone companies in certain areas may place extra emphasis on certain aspects of NEBS, such as earthquake resistance in the western United States, humidity in the South, and airborne contaminants in the Midwest. Some telephone companies are even issuing their own extensions to the NEBS criteria. For example, to test for flame spread, one such company has established a more stringent requirement than NEBS requirement per RNSA-NEBS-95-0003, Revision 10. NEBS itself allows for three levels of conformance. Levels 1 and 2 exist essentially to facilitate the rapid deployment of new technologies and are defined thusly:

Level 1-"The minimum acceptable level of environmental compatibility needed to preclude hazards and degradation of the network facility and hazards to personnel".

Level 2-"The minimum acceptable level of environmental compatibility need to provide limited assurance of equipment interoperability within the network facility environment".

Level 3-"The minimum level of environmental compatibility needed to provide maximum assurance of equipment interoperability within the network facility environment. The Level 3 criteria provide the highest assurance of product interoperability. Level 3 criteria are suited for equipment applications which demand minimal service interruptions over the equipment's life". Achieving compliance to NEBS Level 3 or above criteria is a costly and time-consuming process.

NEBS categories Electromagnetic Compatibility - The Telcordia A2LA accredited EMC test facilities analyze product performance in the complex electromagnetic environments of telecommunications facilities. The facilities include an FCC-listed 10 meter OATS and 3 meter Semi-Anechoic Chamber, as well as a compact 3 meter Semi-Anechoic chamber which are used to test for EMI and ESD. Fire Resistance - Experts perform both small-scale and large-scale fire tests on telecom equipment and cabling. Our fully pollution-controlled facility features the latest technology in oxygen calorimetry and infrared video photography. Airborne Contaminants - Equipment is exposed to gaseous and particulate airborne contaminants found in such environments as densely populated areas.

Thermal Robustness - Equipment performance is evaluated under various temperature and humidity conditions. The facilities can also create environments that equipment may experience during transportation and/or storage. High Voltage - Capable of delivering 375,000 VA of AC power faults and 45,000 V of lightning surges, the facility is used for lightning, power cross, power induction, and grounding analyses. Earthquake and Vibration - To determine whether equipment will operate during and after earthquake and vibratory stresses, static and dynamic testing of network products, frameworks, cable racks, and battery stands is performed. Airborne Contaminants - Equipment is exposed to gaseous and particulate airborne contaminants found in such envronments a

Bibliography

The FaultZone Recipe for Reliability:
NEBS Testing and CompactPCI-based Equipment Design
June 2001 Copyright © FORCE COMPUTERS, Inc.