GB2123627A

GB2123627A - Electrical circuit interruption

Info

Publication number: GB2123627A
Application number: GB08210439A
Authority: GB
Inventors: David Alan Dolbey Jones
Original assignee: Individual
Current assignee: Individual
Priority date: 1982-04-08
Filing date: 1982-04-08
Publication date: 1984-02-01

Abstract

A single-pole electrical circuit interrupter 1a is tripped in response to an output from e.g. a microprocessor 2 designed to analyse the current flowing through the interrupter. The device may be a self-contained unit deriving its power from the circuit in which it is placed. It may be capable of being programmed to recognise specific types of fault by the nature of the harmonics of the power current, and may incorporate a learning technique whereby current overload to which the device responds is adjusted down to within closer limits over the normal running level. The device may be inter-connected with other devices to provide multi-phase interruption. It can be housed in a cartridge fuse type body so as to provide a direct replacement for a cartridge fuse. <IMAGE>

Description

SPECIFICATION Electrical circuit interruption and interrupter devices This invention relates to the interruption or switching of electrical circuits or supplies, particularly but not exclusively in applications where HRC (high rupturing capacity) fuses have hitherto been employed.

Basically, according to one aspect of the present invention, there is provided an interrupter device comprising a single-pole electrical circuit interrupter incorporating an electronic device designed to analyse the current flowing through the interrupter and to recognise those characteristics of the current which indicate a need to interrupt that current, the electronic device then producing an output which causes actuation of means, associated with the interrupter, to cause the interrupter to open the circuit.

This device may be designed to give overload or fault-current protection to electrical equipment (motors, cables, etc.) better than conventional melting fuses and electromagnetic or electrothermal overload devices give. Moreover the device could be programmed to recognise certain specific types of fault which are recognisable only by the nature of the harmonics of the power current: for example, arcing faults which under some circumstances may be otherwise indistinguishable from normal load current and which therefore would not be "seen" by conventional fuses.

Other features could be incorporated, in particular: (a) learning techniques, the overload being constantly adjusted down to within closer limits over the normal running level.

(b) re-closing facilities (the interrupter being suitably designed and associated with energy storage means for the re-closing action) and these may be such as to enable the device to be employed in sequencing i.e. opening and reclosing under external control or automatically on the occurrence of certain conditions In a particularly advantageous form of the invention the device is a self-contained unit deriving its power from the circuit in which it is placed as a "straight-through" or "one-pole" circuit interrupter. Moreover, it may be interconnected, by means of secondary wiring, with other devices if necessary to create, for example, multi-pole interruption of a multi-phase power circuit. Such a combined arrangement may be designed to employ a single microprocessor or other such electronic device.

Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Fig. 1 shows diagrammatically the main components of a single pole interrupter device; Fig. 2 illustrates a practical embodiment of such a device.

Referring first to Fig. 1, this embodiment of the invention comprises a "straight-through" power conductor 1 with a circuit interrupter or switching device 1 a which is controlled by an output from an electronic device shown as a microprocessor or miniature electronic digital computer 2 responsive to the output from a current transformer 3 which also provides the power supply to the microprocessor 2. The device boundary is indicated by the chain-dashed rectangle 4 and the drawing also indicates main circuit connections 5 and 6 to terminals 5a and 6a of the device.

The interrupter 1 a may be a conventional circuit current interrupter-electromechanical (such as a miniature circuit breaker, electromechanical trip or vacuum interrupter), exploding link, etc. Altematively or additionally to the current transformer 3 there may be provided a shunt power conductor arrangement comprising connections at different points along the power conductor 1 so that the microprocessor 2 is supplied with a voltage derived from the potential difference between those points owing to the resistance of the conductor 1: although this resistance and therefore the voltage will be small, the microprocessor 2 can be designed to operate from it.

Turning now to Fig. 2, this illustrates a practical embodiment of the device shown diagrammatically in Fig. 1. In this example the device is built into the body 7 of a cartridge fuse in place of the conventional melting fuse-link power conductor. The terminals 5a and 6a of Fig.

1 are constituted by end tag connections. The drawing shows the body broken away to make the internal parts visible: the main power connection 1 to the end tag 6a; the interrupter 1 a indicated as being a circuit breaker, for example a vacuum interrupter or bottle; the microprocessor 2 with a power pack 2a; and the current or shunt transformer 3 having output connections 3a and 3b to the power pack 2a. The main power conductor 1 is shown as being connected at 1 b to one end of the vacuum bottle 1 a whose other end is secured or otherwise connected to the adjacent end tag 5a.An indicator 8 is provided to show the state of the device when in use: with the indicator 8 having connections (not shown) to the microprocessor 2, the power pack 2a or the output connections 3a and 3b from the current or shunt transformer 3, the indicator will show, for example, that the circuit is intact or if there is current flowing through the device.

The interrupter device which has been described may be termed a programmable circuit interrupter, the microprocessor 2 being programmed to provide the characteristics which the device is required to have. The programmable circuit interrupter can be designed to interrupt electric current flowing through it, at any predetermined moment following the detection of particular characteristics of the electric current. It can be designed to recognise the presence of overload and fault current in a circuit and be capable of responding to interrupt the current accordingly. It can be constructed to occupy no more than the physical space and dimensions occupied by certain conventional melting fuses so as to be capable of being inserted in place of and as a direct replacement for such fuses.It can be designed to be capable of recognising certain arcing faults in a circuit and acting to interrupt the current so as to remove the danger and/or minimise damage caused by the arcing fault.

The current characteristics are recognised and measured by means of the electronic device incorporated in the programmable circuit interrupter. More specifically, current magnitude and waveform are analysed by digital computational techniques by means of microelectronic circuits within the device. The parameters of the current are compared against the acceptable levels of magnitude and harmonic content, which are expressed in the programming of the microprocessor.

The programmable circuit interrupter may be designed to incorporate the features (a) and (b) mentioned above. Where re-closing facilities are required, the energy storage means may conveniently be pneumatic, for example a compressed air cylinder or bottle which could be disposable or associated with a small air compressor to recharge it or top it up after use.

In the case of the exploding link type of interrupter (not re-closable) this would be actuated by a small explosive charge, detonated electrically by the output from the microprocessor or other electronic device. Such output could also be amplified for the purposes of effecting the re-closure of a re-closeable interrupter by electromagnetic means instead of the pneumatic means previously mentioned.

There have thus been described means for interrupting and possibly also re-closing electrical circuits, employing self-contained units comprising means for analysing the current flowing in the circuit and causing interruption of the current when the analysis indicates a need to do so.

Claims (Filed on 10/3/83) 1. An interrupter device comprising a singlepole electrical circuit interrupter incorporating an electronic device designed to analyse the current flowing through the interrupter and to recognise those characteristics of the current which indicate a need to interrupt that current, the electronic device then producing an output which causes actuation of means, associated with the interrupter, to cause the interrupter to open the circuit.

2. An interrupter device as claimed in claim 1 being a self-contained unit deriving its power from the circuit in which it is placed as a "straight-through" or "one-pole" circuit interrupter.

3. An interrupter device as claimed in claim 1 or claim 2 capable of being programmed to recognise specific types of fault by the nature of the harmonics of the power current.

4. An interrupter device as claimed in claims 1 to 3 incorporating a learning technique whereby current overload to which the device responds is adjusted down to within closer limits over the normal running level.

5. An interrupter device as claimed in any one of claims 1 to 4 incorporating re-closing facilities.

6. An interrupter device as claimed in any one of claims 1 to 5 interconnected with other devices to form a composite device.

7. An interrupter device as claimed in claim 6 wherein the composite device is arranged to provide multi-pole interruption of a multi-phase power circuit.

8. An interrupter device as claimed in any one of claims 1 to 7 housed in a cartridge fuse type body.

9. An interrupter device substantially as herein described with reference to Fig. 1 of the accompanying drawings.

10. An interrupter device as claimed in claim 9 and substantially as herein described with reference to Fig. 2.

11. Any novel feature or combination of features herein described and/or illustrated in the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. accordingly. It can be constructed to occupy no more than the physical space and dimensions occupied by certain conventional melting fuses so as to be capable of being inserted in place of and as a direct replacement for such fuses. It can be designed to be capable of recognising certain arcing faults in a circuit and acting to interrupt the current so as to remove the danger and/or minimise damage caused by the arcing fault. The current characteristics are recognised and measured by means of the electronic device incorporated in the programmable circuit interrupter. More specifically, current magnitude and waveform are analysed by digital computational techniques by means of microelectronic circuits within the device. The parameters of the current are compared against the acceptable levels of magnitude and harmonic content, which are expressed in the programming of the microprocessor. The programmable circuit interrupter may be designed to incorporate the features (a) and (b) mentioned above. Where re-closing facilities are required, the energy storage means may conveniently be pneumatic, for example a compressed air cylinder or bottle which could be disposable or associated with a small air compressor to recharge it or top it up after use. In the case of the exploding link type of interrupter (not re-closable) this would be actuated by a small explosive charge, detonated electrically by the output from the microprocessor or other electronic device. Such output could also be amplified for the purposes of effecting the re-closure of a re-closeable interrupter by electromagnetic means instead of the pneumatic means previously mentioned. There have thus been described means for interrupting and possibly also re-closing electrical circuits, employing self-contained units comprising means for analysing the current flowing in the circuit and causing interruption of the current when the analysis indicates a need to do so. Claims (Filed on 10/3/83)

1. An interrupter device comprising a singlepole electrical circuit interrupter incorporating an electronic device designed to analyse the current flowing through the interrupter and to recognise those characteristics of the current which indicate a need to interrupt that current, the electronic device then producing an output which causes actuation of means, associated with the interrupter, to cause the interrupter to open the circuit.