IEEE C37.20.7-2001

This guide establishes a method by which medium-voltage metal-enclosed switchgear, as defined by IEEE Standards C37.20.2 and C37.20.3, may be tested for resistance to the effects of arcing due to an internal fault. This guide applies only to equipment utilizing air as the primary insulating medium and rated above 1000VAC. It applies to both indoor and outdoor equipment, however special consideration must be given to the building size and construction for indoor applications ( not addressed by this document). The tests and assessments described in this guide are only applicable to arcing faults occurring entirely in air within the enclosure when all doors and covers are properly secured. This guide does not apply to arcing faults which occur within a component of the switchgear assembly, such as instrument transformers, sealed interrupting devices, fuses, etc. Switchgear designs which meet the requirements of this guide will be referred to as arc resistant metal-enclosed interrupter switchgear or arc resistant metal-clad switchgear as applicable, or generally, as arc resistant switchgear. This project is intended to continue the work of the original project, P1405, with the correct document designation from C37. The original purpose is as follows: There are presently no U.S. testing methods for evaluating metal-enclosed switchgear under the effects of internal arcing. There are, however, specific references to this phenomenon in the national electric code and in OSHA safety documents. The current testing methods come from IEC 298 appendix AA, EEMAC G14-1, and SAA 1136.1 appendix D. These document are similar but there is no effort to unify the procedure or evaluation results. Therefore, there is inconsistency in the testing methods used in the U.S. This guide would consolidate the desirable aspects of all existing documents and provide an evaluation and rating structure that is compatible with U.S. standards. This revision to PC37.20.7 is to add the term "Medium-Voltage" to the title and throughout the document as the more correct term for describing the equipment concerned. New IEEE Standard - Superseded. Superseded by IEEE Std C37.20.7-2007. A procedure for testing and evaluating the performance of metal-enclosed switchgear for internal arcing faults is covered. A method of identifying the capabilities of this equipment is given. Service conditions, installation, and application of equipment are also discussed.