Conformity Magazine - March 2009 - (Page 20) Emerging Issues in Standards © Les Cunliffe | Dreamstime.com Cunliff UL Outline of Investigation Subject 2564: A New Recognition Document for Telecommunications Overcurrent Protection This article on Subject 2564 has four parts, as follows: 1) document (Part 1) structure; 2) testing approach; 3) power fault testing; and 4) lightning impulse testing. Part 1 General Requirements It is important to understand Part 1 as the Technology Parts modify or provide additional information to Part 1. The main clauses of Part 1 are as follows: • General, Definitions and Symbols • Service Environment Conditions • Classification • Characteristics • Marking • Tests • Annex A (Protector Templates) • Annex B (UL 60950-1 Power line cross flow chart) • Annex C (Impulse Waveform Requirements) • Annex D (Background on System and Template Designations) Table 1 in General provides a summary of the current-time template applications and test values. The Environment Conditions clause contains the overcurrent protector temperature derating percentages for the different technologies. Using these values, the current-time template curve can be adjusted for other temperatures to allow testing at those temperatures (e.g., -40 °C). by Mick Maytum, formerly of Bourns Limited O vercurrent protector components used in telecommunications ports are essentially shown as “fit for purpose” during the equipment power fault and lightning surge qualification process. Existing UL component qualification documents for technologies like fuses, positive temperature coefficient (PTC) thermistors and line feed resistors (LFR) don’t cover the power fault and lightning surge conditions of equipment standards such as GR-1089-CORE, Issue 4 and UL 60950-1. The UL Outline of Investigation, Subject 2564, provides a recognition means for current limiter components used in wire line paired cable telecommunications ports of equipment compliant with common North American standards. Subject 2564 covers the GR-1089-CORE1, UL 609502, UL 14593, UL 497A4 and TIA 968-A5 equipment standards. The seed document for Subject 2564 was developed over three years by the Telecommunications Industry Association (TIA) TR41.7.5 Telecommunications Overcurrent Surge Withstand subcommittee. TR-41.7.5 membership included many wellknown manufacturers of overcurrent protection components and representatives from Underwriters Laboratories (UL). The starting point for TR-41.7.5 was to analyze the power line fault and lightning surge tests of equipment standards and select the most stressful tests. Covering five overcurrent protection technologies meant that any test that was highly stressful for one or more technologies was included. To cater for technology specifics, 2564 (Part 1: General Requirements) has additional Parts to cover fuses, polymer PTC thermistors, line feed resistors (LFRs) and electronic current limiters (ECL). The part for ceramic PTC thermistors was not completed in time to be included in the first issue. The various power line fault current-time operating values are defined as graphic templates (A through I) and plot-point tables. 20 Conformity marCh 2009 http://www.Dreamstime.com
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