Search

Since the arc-fault circuit interrupter (AFCI) was commercially introduced in 1998, questions have arisen about how it detects arcs, whether it detects series and parallel arcs, and what types of AFCIs are available. Types other than the original branch/feeder AFCI are emerging. This paper is intended to provide an update regarding answers to those questions, following an earlier paper that introduced the basic functioning of the AFCI. Index Terms--Arc fault, arc-fault circuit interrupter (AFCI), arc-fault detection.

A series of previous papers has provided information regarding the arc flash hazard and methods of calculating its potential impact on persons working on or near the equipment. This paper extends that base of information by focusing on the arcing current level and duration in low-voltage circuits protected by circuit breakers (CBs). It describes a method of calculating incident energy and the flash protection boundary due to arcing occurrences in equipment protected by CBs. This method provides convenient procedures for determining these values for generic situations in which some details of the CB are not known. Further, it provides a process for determining these values in typical feeder and branch circuit applications involving common transformers and cable sizes and lengths. The values are needed to determine safe work practices and appropriate Personal Protective Equipment to comply with NFPA 70E, Standard for Electrical Safety Requirements for Employee Workplaces. Index Terms--Arc flash, circuit breaker (CB), flash protection boundary, incident energy.

Series-rated circuit breakers are commonplace, but not always well understood. This paper provides basic information on how a series rating is tested and relates that information to the interaction of the overcurrent protective devices involved. The paper also explores the question of whether calculations can be used to determine the series rating of an untested combination. Index Terms--Dynamic impedance, molded-case circuit breaker (MCCB), overcurrent protection, series rating.

A study was conducted to present user guidelines for system application on the correct selection and application of molded-case circuit breakers within the established system of product standards and safety codes. A system evaluation approach was utilized for the evaluation and testing of distribution equipment. Interrupting ratings were then expressed as rms symmetrical values. In addition, the importance of wires in characterizing the performance of circuit breakers was examined.

The arc-fault circuit interrupter is beginning to emerge as a new product in residential applications in the U.S. to protect against conditions that may cause fire. This paper provides some of the background regarding its emergence as a product and the function it is intended to provide. The evolving technology may also lend itself to industrial applications, as the potential applications become sufficiently well understood. Index Terms - Arc-fault circuit interrupter, arc-fault detection.

This paper addresses the application of instantaneous-trip molded-case circuit breakers (MCCB's) in combination motor starters. These circuit breakers have been widely used in many industries for motor circuit protection. If they are not properly applied, situations of false tripping on motor starting and contact welding of contactors under low-level faults may occur. Energy efficiency motors compound the issue of false tripping on motor starting. This paper discusses the components of combination starters, reviews testing requirements, and provides examples of coordination with analysis of application issues and solution options. Index Terms - Combination motor starter, instantaneous-trip molded-case circuit breaker, low-voltage protection.

Motor short-circuit contribution is a real consideration in low-voltage systems. It must be considered in deciding whether to apply series ratings of overcurrent protective devices. Virtually every electrical system has motors in it someplace. This paper confirms the existence of low-voltage motor short-circuit contribution by test, examines some of the relevant literature, explores typical installations, and recommends application guidelines.

Low-voltage, direct current equipment in utility control systems, uninterruptible power systems (UPS), telecommunication systems, and elsewhere has received increasing attention in recent years. Power conditioning needs are one reason. Closer attention by regulatory agencies is another. This paper is intended to help fill a gap in available material on ratings and application characteristics of low-voltage circuit breakers in dc systems. Some of this material is prepared for use by the IEEE Battery Protection Working Group in developing a Guide for Protection of Stationary Battery Systems under project P1375.

Calculation techniques used in designing low-voltage electrical distribution systems have advanced decidedly over the past two decades, as has the design of modern molded-case circuit breakers (MCCB's). There is a need for data and interfacing techniques that permit the system design engineer to calculate system response under short-circuit conditions with the MCCB as an active element of the circuit. This paper discussed the MCCB as a circuit element and describes one method of calculating system behavior with the MCCB as an element.

Short-circuit tests of individual poles of molded-case circuit breakers are required under North American industry standards. Test current is intentionally at a limited fault availability level rather than at the interrupting rating of the circuit breaker. This paper clarifies the single-pole test requirements. It then examines the potential fault conditions under a variety of systems and provides application guidelines considering the potential fault conditions.

Short-circuit tests of individual poles of molded-case circuit breakers are required under North American industry standards. Test current is intentionally at a limited fault availability level rather than at the interrupting rating of the circuit breaker. This paper clarifies the single-pole test requirements. It then examines the potential fault conditions under a variety of systems and provides application guidelines considering the potential fault conditions. Index Terms--Ground fault, molded-case circuit breaker, short-circuit interruption.

The arc-fault circuit interrupter is beginning to emerge as a new product in residential applications in the U.S. to protect against conditions that may cause fire. This paper provides some of the background regarding its emergence as a product and the function it is intended to provide. The evolving technology may also lend itself to industrial applications, as the potential applications become sufficiently well understood.