Changes in customers' needs require improvements in the reliability and quality of the electricity supply This paper describes how the concept of custom power is now becoming familiar The term describes the value-added power that electric utilities and other service providers will offer their customers in the future The improved level of reliability of this power, in terms of reduced interruptions and less variation, will stem from an integrated solution to present problems, of which a prominent feature will be the application of power electronic controllers to utility distribution systems and/or at the supply end of many industrial and commercial customers and industrial parks >

Introducing custom power

As power semiconductor devices are the key components of hybrid DC circuit breakers (HCBs), how to select suitable devices is critical for the whole HCB design. First, this paper compared the general characteristics of press pack insulated gate bipolar transistor (IGBT), injection-enhanced gate transistor (IEGT), and integrated gate commutated thyristor (IGCT). Then working conditions of devices were analyzed from the perspective of HCBs. According to these, vital features of devices including maximum turn-off current, on-state voltage, conduction ability, and robustness of power semiconductor devices were carefully analyzed and compared. Related experiments were implemented to compare maximum turn-off capability, and the 4.5 kV/3 kA IGBT/IEGT was able to turn off 19 and 22 kA respectively after 5-ms current conduction. Analysis and experiments indicated that IGCT was suitable for natural commutation low-voltage and low-current hybrid circuit breakers, due to its low on-state voltage and huge surge current conduction ability. Comparatively, IGBT and IEGT were more suitable for very high current interruption, and IEGT was the superior selection among available commercial devices. However, the interference should be considered in applications.

Analysis and Experiments for IGBT, IEGT, and IGCT in Hybrid DC Circuit Breaker

This paper describes the development of a solid-state fault current limiting and interrupting device (FCLID) suitable for low-voltage distribution networks. The main components of the FCLID are a bidirectional semiconductor switch that can disrupt the short-circuit current, and a voltage clamping element that helps to control the current and absorb the inductive energy stored in the network during current interruption. Using a hysteresis-type control algorithm, the short-circuit current can be constrained according to a predefined profile. Insulated-gate bipolar transistors and diodes are used to construct the semiconductor switch. Varistors are used as the voltage clamping element. An effective method is adopted to improve the current sharing between parallel varistors in order to provide the required capability of energy absorption. An overall protection scheme for the FCLID is described. A prototype FCLID for 230-V single-phase, or 400-V three-phase, applications is developed and tested. Analyses and experiments are carried out to define the stresses that the main components in the FCLID are subject to. The results show that the developed prototype is capable of limiting a 3-kA prospective short-circuit current to 120 A for a period of 0.8 s, without exceeding the thermal limits of the chosen switches and varistors

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Development of a prototype solid-state fault-current limiting and interrupting device for low-voltage distribution networks

The paper demonstrates, through the use of electromagnetic transient simulations, the key issues in the application of solid state devices for fault control and protection in the distribution systems. Three types of topologies have been considered, viz. a bus tie breaker, a transfer switch, a fault current limiter, but only two have been discussed in detail; the bus tie breaker is taken to be a special case of the fault current limiter. The control scheme for each topology has been designed and studied, with emphasis on the detection schemes and the responses to various system and load parameters. All simulations have been carried out using the PSCAD/EMTDC program.

On using the solid state breaker in distribution systems

The expansion of electric distribution system has resulted in an increasing need of fault current limiter in so as to limit fault currents to the downstream protection devices as a means of improving power quality Considerations in the use of fault current limiter are that it must be reliable in operation, compact and inexpensive This paper presents a comprehensive performance evaluation on the use of solid-state fault current limiters (FCL) in a distribution system The FCL simulation model has been developed using the electromagnetic transient program PSCAD/EMTDC and a new control strategy for the FCL has been proposed for instantaneous detection of over current The FCL is evaluated in terms of its performance in limiting fault current to the tolerable limit of the system, as well as the response of the FCL within a fraction of a cycle of about 2 ms The effects of varying circuit parameters such as R, L, and C as part of the FCL device has been investigated It has been noted that the inductive reactor, which is part of the FCL device, is suitable for limiting the fault current The impact of induction motor loads on the FCL has also been analyzed Simulation results show that the FCL is effective for reducing short circuit currents and also can be used to protect bus bars from voltage sag when the system is subjected to various types of faults

http://ieeexplore.ieee.org/iel5/9885/31418/01459700.pdf

Performance evaluation of solid state fault current limiters in electric distribution system

Advanced current interruption technology, utilizing high power solid-state circuit breakers, offers a viable solution to most of the distribution system problems that result in voltage sags, swells, and power outages. Solid-state, fast acting (sub-cycle) breakers can instantaneously transfer sensitive loads from a normal supply that experiences a disturbance to an alternate supply that is unaffected by the disturbance. Here, the authors describe the planning, development and demonstration of solid-state 13 kV distribution class circuit breakers.

M. Sarkozi

Papers

Solid-state 13-kV distribution class circuit breaker: planning, development and demonstration