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FAST FAIL SAFE SOLID STATE POWER CONTROL

IP.com Disclosure Number: IPCOM000249643D
Publication Date: 2017-Mar-13
Document File: 5 page(s) / 358K

Publishing Venue

The IP.com Prior Art Database

Abstract

This paper relates to a protection system for a high voltage circuit. The protection system comprises a main switch that is aimed at cutting the power line supplying current to a load in case of overcurrent, and an alternative switch that is activated only if the main switch were to fail.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 52% of the total text.

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FAST FAIL SAFE SOLID STATE POWER CONTROL 

 

I) ABSTRACT: 

This paper relates to a protection system for a high voltage circuit. The protection system comprises a main switch that is aimed at cutting the power line supplying current to a load in case of overcurrent, and an alternative switch that is activated only if the main switch were to fail.

5  II) TECHNICAL PROBLEM TO BE SOLVED: 

A main switch is constituted by a SSPC system (Solid state power controllers) that provides electrical protection to a secondary circuit supplied in current from a primary circuit (See figure 1). The SSPC system comprises power electronics semiconductors switches such as MOS power transistors. In normal conditions (no overcurrent in the power line connecting the primary circuit 10  and the secondary circuit), the power transistors switches are closes. The electrical protection is calibrated to open the power transistors switches according to a fast trip curve command depending on the current measured the system and on the time.

To reduce electrical arc thermal impacts (so to avoid damage to environment, to other lines, and risk of high voltage propagation up to equipment), one solution is to minimize the trip time of the 15  main switch using a fast trip main SSPC system. A fast trip SSPC system has typically a trip time below 100 ms.

Figure 1: Single switch arranged on the power line to protect a secondary circuit.

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A problem encountered in a SSPC system is that its failure mode is generally a short circuit in its main switch components.

When this type of failure occurs, it is no longer possible to control the secondary line opening which will remove the overcurrent protection and may lead to destructive overheating of the secondary circuit lines in the event of problems with the equipment which might even result in damaging the 5  primary line.

The certification authorities request a backup to a single SSPC system. A well-known solution is to add a fuse in serial with the single SSPC system. This fuse is calibrated to cut-off when a threshold value higher than the safety cut-off value for the SSPC’s main switch is reached.

The cut-off of this fuse occurs only in the event of failure of the downstream circuit and, because 10  the characteristics of the fuses are normal trip time (I2t curves), it cannot be possible to reduce electrical arc thermal impacts with a fast trip as the main SSPC would have done.

Therefore, such a back-up solution does not make it possible to ensure with a very high probability (< 1.10-9 /h)) that the secondary circuit will be fast opened in case of short circuit.

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III) SPECIFICATION: 

The idea (See figure 2) is to arrange a back-up switch, hereinafter referred as to alternative switch, downstream the main switch. The alternative switch comprises a fuse in serial with the main SSPC on the power line, and another SSPC system, hereinafter referred to as alternative SSPC system, which is connected downstream the fuse be...