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P1683 - IEEE Draft Guide for Motor Control Centers Rated up to and Including 600 V AC or 1000 V DC with Recommendations Intended to Help Reduce Electrical Hazards

The purpose of this Standard is to: 1. Provide the functional design requirements for low-voltage motor control centers rated up to up to 600 Vac or 1000 Vdc with features intended to reduce the likelihood of exposure to electrical shock, and the likelihood of internal arcing faults from occurring while qualified persons are performing normal [2] activities on MCCs. 2. Provide guidance to the User for the preparation of specifications for MCCs with these features. 3. Provide high level requirements to the Manufacturers for design and testing of MCCs with these features. The development of detailed verification testing requirements is expected to be in the Base MCC Safety Standards. 4. Provide requirements for the manufacturer's interface relationships to the specifier, installer, and user."e; This Standard primarily focuses on shock and arc flash hazards and provides requirements aimed at reducing the probability that an incident will occur due to these hazards. As with any electrical power equipment, steps should be taken to address these (and other) hazards. Basic examples are: * Recognize that a hazard exists, e.g., electrical power presenting shock and arc-flash hazards * Warn that a hazard condition exists, define the hazard, recommend the steps that should be taken (if possible) to avoid the hazard, what type protection is needed if the hazard can not be avoided, e.g., follow the steps and direction as required by NFPA 70E Standard for Electrical Safety in the Workplace (NFPA 70E) The prudent step is always to remove the hazard. In the case of an energized MCC, the hazard is removed by turning the power off and 'locking out or tagging out' the equipment (Re. NFPA 70E 130.1). But, this de-energizing operation may not be appropriate for certain tasks such as some troubleshooting. Now, NFPA 70E Article 130 "e;Working On or Near Live Parts"e; recognizes such tasks and, in the case of MCCs, that the MCC's enclosure door can be open and qualified persons can be working 'on or near live parts (energized conductive components)'. Working on or near live parts should be a last resort in the workplace; after all other opportunities for establishing an electrically safe work condition have been exhausted. Work on live parts at 50V or more should only be performed if the employer can demonstrate that de-energizing will introduce additional hazards or is not feasible due to equipment design or operational limitations. (NFPA 70E 130.1) However, in contrast to the stated work situations recognized by NFPA 70E, the intent of the present Base MCC Standards is more restrictive: it is written with the expectation that qualified persons only perform limited inspection activities 'near' but in no case perform maintenance activities 'on' energized parts. This Standard is to augment the requirements of the Base MCC Standard and its purpose is to identify specific MCC design features and field practices to reduce the likelihood of shock or internal arcing faults when qualified persons are performing normal activities 'on and near live parts.' Thus, when an MCC is manufactured in accordance with the Base MCC Standards and augmented with design features proposed by this Standard, the MCC will be better equipped for a broader range of activities to be carried out under the requirements of NFPA 70E Article 130. It is not the intent of this Standard to enable users to perform all possible maintenance tasks 'on or near live parts,' but to enable users to perform the types of activities described in this Standard with less likelihood of incident or injury. It is the intent of this standard to reduce the likelihood of shock and arc-flash exposure as well as consequent equipment damage and service interruptions involving MCCs that are constructed in accordance with the requirements of the Base MCC Safety Standards, such as UL 845, and this Standard as compared to MCCs that do not meet or incorporate the features described herein. The ultimate goal of this Standard is the further development of MCC design for the continuous improvement of employee safety when working on energized MCCs. This must be supported by ongoing improvements in safety training and work practices.This Standard provides functional design and factory verification test requirements for Motor Control Centers (MCC) intended to reduce the likelihood of shock and arc-flash injuries. It applies to single and three phase 50 and 60 Hz and dc motor control centers rated not more than 600 V ac or 1000 V dc. These requirements are intended to facilitate performance of defined maintenance tasks on energized equipment [1].The requirements of this Standard are intended to augment the existing requirements of the applicable MCC safety standards for motor control centers, e.g. NEMA ICS 18-2001 "e;Motor Control Centers"e; and ANSI/UL 845-2005 "e;Motor Control Centers"e; which is a also known as NMX-J-353-ANCE-2006 and CSA C22.2 No. 254-05 (Base MCC Standards). This Standard also identifies field practices and interface relationships between the Specifier, Manufacturer, Installer and User for safety related concerns. The requirements in this standard compliment safety requirements and procedures as stipulated by workplace safety standards and site practices and site procedures, e.g., NFPA 70E Standard for Electrical Safety in the Workplace (NFPA 70E), site practice on Personal Protective Equipment, etc.
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