Electromechanical Circuit Breakers Research Articles

A Review of Solid-State Circuit Breakers

Although conventional electromechanical circuit breakers have a proven record as effective and reliable devices for circuit protection, emerging power distribution technologies and architectures, such as dc microgrids, require improved interruption performance characteristics (e.g., faster switching speed). The need for faster switching operation, in combination with the latest developments of advanced power semiconductor technologies, has spurred an increase in the research and development in the area of solid-state circuit breakers. This article provides a comprehensive review of various solid-state circuit breaker technologies that have been reported in the literature during recent years. First, we categorize solid-state circuit breakers based on key features and subsystems, including power semiconductor devices, main circuit topologies, voltage clamping methods, gate drivers, fault detection methods, and commutation methods for power semiconductor devices. Second, we discuss the various challenges associated with the design of solid-state circuit breakers from the perspective of generic applications and provide a comparison of several solid-state breaker technologies based on key metrics. Finally, we provide a useful framework and point of reference for future development of solid-state circuit breakers for many emerging power distribution applications.

Arc Discharge–Induced Ignition of Combustibles Placed on a Damaged AC Power Supply Cord

One of the major causes of unintentional electrical fires is short circuit of an electrically and/or mechanically damaged alternating power supply cord. Detecting of such an event and interrupting the power supply may be beyond the capability of a conventional electro-mechanical circuit breaker. A lot of research papers have been published related to arc fault of wiring and its detection method. Furthermore, arc fault circuit interrupters have been put into practical use. The objective of the present paper is to understand fault of damaged power supply cord under two selected situations observed in practical use or considered suitable to understand fire ignition. Using two kinds of samples similar to but different from samples prescribed in UL1699 standard, the ignition mechanism of combustibles is discussed based on the results of laboratory experiments. The findings herein underscore the important role of the arc in the ignition of combustibles that are placed on the damaged part of a power supply cord, which is normally followed by a short circuit of broken element conductors or breakage of intact element conductors. Moreover, a possible arc detection feature in the two situations is discussed based on a distorted voltage waveform.

Developments in Pyrotechnic-Assisted Fuses [Happenings

Every electric power engineer has some familiarity with electrical faults and technologies for fault mitigation. The basic problem presented itself to the earliest workers in electric technology, and the basic solutions have been present essentially from the beginning, and many are used with great effect to this day. In some applications where essentially the same protections are required in millions of instances per year, very cost-effective solutions are common. Mainstream automobiles (i.e., setting aside for the moment battery-electric and hybrid-electric vehicles), for example, are largely protected by simple electrical fuses, which are technically effective at very low cost. Residential electrical systems at one time used fuses, too, but these have mostly been supplanted by resettable electromechanical circuit breakers.

An Advanced Protection Scheme for Enabling an LVDC Last Mile Distribution Network

Low voltage direct current (LVDC) distribution systems have the potential to support future realisation of smart grids and enabling of increased penetration of distributed renewables, electric vehicles, and heat pumps. They do however present significant protection challenges that existing schemes based on DC fuses and conventional electro-mechanical circuit breakers (EMCBs) cannot manage due to the nature of DC faults and slow device performance. Therefore, this paper presents an advanced protection scheme that addresses the outstanding challenges for protecting an LVDC last mile distribution network. The scheme takes advantage of advanced local measurements and communications that will be naturally integrated in smart grids, and the excellent level of controllability of solid state circuit breakers. It thus provides fast DC fault detection and interruption during DC transient periods in addition to achieving fault limitation and fast reliable restoration. The introductory part of the paper quantifies the potential benefits of LVDC last mile distribution networks, and discusses the potential LVDC architectures that best utilise the existing plant. Based on the new LVDC architectures, a typical UK LV network is energised using DC and modelled, and used as a case study for investigating the protection issues and evaluating the new protection scheme performance through simulation.

Microengineered Electrically Resettable Circuit Breaker

Electromechanical circuit breakers based on microelectromechanical systems (MEMS) structures are proposed, and initial prototypes are demonstrated. The devices use laterally moving thermal actuators to set and trip low resistance contacts. The actuators are fabricated from electroplated Ni, on Si substrates, with Au-Co contact layers. Trip currents of 300 mA are obtained, with contact resistances below 1 /spl Omega/. Rapid tripping (below 50 ms) is achieved, even for modest over-current levels, and sensitivity to ambient temperature is much less than for positive temperature coefficient (PTC) devices typically used for over-current protection in electronics applications. These MEMS devices offer an ultra-miniature, potentially low cost solution for circuit protection applications at low currents, where a high degree of system control is desired.