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Abstract
Due to the working condition of low-voltage cabling from the mining flameproof movable substation to the loads of the mining face being poor, it is easy to cause various external mechanical damages to the cable sheaths. Furthermore, a single-phase earth leakage fault or short-circuit fault can occur when the low-voltage cable sheaths are damaged, and electric sparks caused by these faults can lead to a gas explosion. As the gas detonation time caused by the above faults is usually more than 5 ms, the high-speed interruption solid-state switch which controls the cables must cut off the current within 3 ms. This requires the action time of the solid-state switch to be less than 1 ms, and at the same time, the sampling and calculation time of the relay protection must be less than 2 ms. Based on these problems, this paper proposes the use of a high-speed solid-state circuit breaker (SSCB) topology at the neutral point of transformer, and analyzes the conduction mechanism and shut-off mechanism of the current of the SSCB. It presents an ultra-high-speed algorithm based on pattern recognition of single-phase earth leakage fault protection, and an ultra-high-speed algorithm of short-circuit fault which is based on the rate-of-change of the current. Finally, through computer simulation experiments and semi-physical simulation experiments, the feasibility of the above three technologies is verified to ensure that when a single-phase earth leakage fault or short-circuit fault occurs in the low-voltage cable, the solid-state switch which is installed in the mining flameproof movable substation will cut off the current within 3 ms.
Highlights
The safety technology for high-speed interruption employs a variety of methods and techniques to prevent electrical fires which can occur when an earth leakage fault or short-circuit fault creates a breakdown or electric spark which ignites a surrounding explosive or flammable medium [1]
In order to achieve the technical target of T0 < 5 ms, this paper presents the topology for a interruption solid-state circuit breaker–neutral (SSCB–N) circuit
The neutral point of a three-phase transformer is controlled by a SSCB–N, which uses an insulated-gate secondary-side neutral point of a three-phase transformer is controlled by a SSCB–N, which uses an bipolar transistor (IGBT) to realize both the connection and interruption
Summary
The safety technology for high-speed interruption employs a variety of methods and techniques to prevent electrical fires which can occur when an earth leakage fault or short-circuit fault creates a breakdown or electric spark which ignites a surrounding explosive or flammable medium [1]. The total fault formation time requires more than 5 ms [5], and the guiding principle of “safety technology for high-speed interruption” can be expressed as: T0 < TF = 5ms (1). Where T0 = total power-off time; and TF = fault formation time. Energies 2020, 13, 934 where T0 = total power-off time; and TF = fault formation time. Two components, protection relay relay Safety technology and high-speed interruption switch technology. Total action time refers to the entire time from the moment when the electrical fault occurs to when electrical fault occurs to when the switch is commanded to interrupt the power.
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