GB2107140A

GB2107140A - Fault indicator for domestic electrical systems

Info

Publication number: GB2107140A
Application number: GB08208836A
Authority: GB
Inventors: Maria Pia Ferettini
Original assignee: Individual
Current assignee: Individual
Priority date: 1981-09-16
Filing date: 1982-03-25
Publication date: 1983-04-20
Also published as: FR2512993B3; DE8136957U1; GB2107140B; IT8122915V0; ES267124Y; ES267124U; FR2512993A3

Abstract

A domestic electrical system is provided with a unit 1 which monitors the system for a number of different possible fault conditions and provides an indication when a fault occurs, the indication identifying the nature of the fault. The unit 1 may be incorporated in a consumer's unit 8. The fault conditions detected may be: residual current (i.e. earth leakage); short- circuit, overcurrent (detected thermally); supply failure. <IMAGE>

Description

SPECIFICATION Fault indicating device for domestic electrical plant The present invention relates to a fault indicating device for domestic electrical plant and more particularly to an illuminated device for indicating a fault condition in electrical plant for domestic use.

Electrical plant requires protection devices (automatic, differential, fusable circuit breakers) which on activation open the circuit in the event of a further fault condition or electrical overloading. Such devices, in order to be easily accessible, are generally contained in an electrical panel board (switchboard).

When, for example, a circuit breaker operates that is, opens the circuit, the non-expert user often does not investigate the reason.

The user asks himself whether the power supply has been interrupted by reason of a power failure for whatever motive or if one or more circuit breakers of the domestic switchboard have operated as a result of too many domestic devices operating simultaneously (operation as a result of overloading), or if there has occurred a fault in the plant (short circuit or earth current fault) or other.

In each case the user attempts to re-instate the circuit by closing the operated circuit breaker.

This operation, if the cause which has resulted in opening of the circuit breaker has not been attended to, can be dangerous either for the user and/or for the environment; this happens since in general the devices contained in the switchboard do not give any indication as to what has happened, or give a partial indication which is not easily interpreted.

If further, there has occurred operation of the automatic or differential circuit breaker of the lighting circuit, the identification and resetting of the device (which is not illuminated) is difficult in the absence of ambient illumination.

Furthermore, conventional devices used to indicate faults in industrial electrical plant are too complex and burdensome to allow their convenient application in domesitc electrical plant. in particular, the individual components of systems adapted to indicate operation of protection devices of industrial electric plant are installed, in consideration of the high availability of space, separately at different points in the circuit of the electrical control panel.

This type of installation results in high costs, of large space requirements and operation complexities which do not allow convenient adoption of such systems in the indicating faults in domestic electrical plant.

A purpose of the present invention is to provide a fault detection and indicating device which is easily operable, has limited dimensions and is of reduced cost, such as to allow simple application of the device to electrical panel boards of domestic plant whilst obtaining at the same time the same effects and advantages of conventional systems applied to industrial plant.

According to the present invention there is provided a fault indicator for domestic electrical plant, comprising a compact modular body provided with means adapted to detect operation of protection and control devices of the plant and to indicate the cause of said operation.

The device which is the subject of the present invention is such as to be insertible into a conventional domestic electrical control panel or to be installable on a wall, or to be made integral with a protection device such as- a circuit breaker or other.

To facilitate identification of the indicating device and to render more immediate the identification of the causes which have resulted in the operation of the control apparatus, the device of the invention is provided with warning lamps and/or luminous indicators.

According to a further characteristic of the invention, the electronic circuits of the device are suitably designed to allow the combination of different functions of the device in a single compact unit of reduced dimensions.

The device according to the invention thus permits the non-expert user to detect the nature of the fault and to deal with it in the appropriate manner to re-activate the plant without damaging it or without danger to the user himself.

Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which Fig. 1 illustrates in perspective an electrical control panel for domestic use provided with a fault indicating device made in accordance with the present invention; Figs. 2 to 5 are side, top, front and bottom views respectively of one embodiment of the device of the invention; Fig. 6 is a view corresponding to Fig. 4 of a device provided with a supplementary indicator for indicating out of service; Fig. 7 shows the device of Fig. 5 incorporated in a protection device; and Figs. 8 and 8A show the operating circuits of the device of the invention.

Referring to the drawings, one embodiment of a fault indication device is substantially composed of a compact modular body constituted by a boxlike structure 1 provided with supply terminals 2, inputs 3 for plant cables adapted to detect differential faults and/or short circuits, and thermal probes 4 for detecting over current.

The device 1 further includes on one front face illuminated warning lamps 5 and/or an indicator 6 (see Fig. 6) for immediate detection of operation of breakdown. More specifically, the luminous warning lamps 5 are suitably numbered or coloured, each warning lamp 5 having a corresponding entry in a legend 7 on an electrical panel board 8.

In the rear part of the modular body 1 there are provided shoulders 9 which permit the insertion, in a modular manner, of the device on the control panel 8 by means of a corresponding support 9' which forms the mounting for conventional protection devices 10 for the plant.

The device according to the invention can also be incorporated in protection devices of the circuit such as automatic and differential circuit breakers in the version with luminous warning lamps and/or indicators (see Fig. 7).

In the box-like body 1 there are contained the electronic circuits of Figs. 8 and 8A, to terminals 2, 2t of which there is applied the supply voltage.

The transformer TR 1 serves to isolate from the supply network the electronic circuits and to supply the voltage ( 1 2v. ac) suitable for their operation.

The diode bridge K1-K2-K3-K4, the capacitors C, and C2 and the integrated stabilizer S, are arranged to provide the nine volt stabilized ac supply to maintain the nine volt nickel cadmium battery BA fully charged and to supply the necessary current, about 50mA, for operation of the electronic circuit of the fault indicating device.

In the event of a power failure it is foreseen that the battery BA will last at least two hours.

Further, in the event of prolonged power failure to avoid that the battery BA does not deteriorate, there is provided a comparator made up of illuminated amplifier SC2 and associated diodes Kr3 and Ka4; resistors Era8, Rrg, R20, R21 and R22 and zener diode Zn1 The comparator de-energises the micro-relay R-r disconnecting the battery BA from the circuit.

The circuit of the device includes operational amplifiers IC1/1, IC1/2, IC1/3 and IC1/4 contained in a single integrated circuit which take on the following functions respectively: detection of differential current; detection of short circuit current; detection of over current; detection of power supply failure.

The operation of the differential current detector and indicator is as follows:- Through a current transformer, TA1, and a filter C7 and C, the differential current signal is applied to the non-inverting input of It1/1, the inverting input of which is connected to earth through resistor R2 (negative terminal of the supply circuit). The signal which occurs in the case of a differential current fault in the electrical plant causes high level saturation at the output of the amplifier resulting in a signal A. A hysteresis and memory circuit constituted by resistor R1, capacitor C3 and diode K5 maintains high the noninverting input of IC1/1 thus memorising the fault.

The above event is indicated by lighting of the LED L1 by means of the amplifier constituted by resistors Ra5 and R23 and transistor TS 1.

The luminous indication is memorised until a push button P, is operated.

The operation of the detector and indicator of short circuit current is as follows:- Through a current transformerTA2, a diode K,8 and a filter R4, Cg, a voltage signal proportional to the short circuit current is applied to non-inverting input of IC1/2, the inverting input of which is connected to earth through resistor R5. The signal, which occurs in the case of a fault as a result of short circuit in the electrical plant causes high level saturation (signal B) of the output of it1/2, which through the hysteresis and memory circuit constituted by resistor R3, capacitor C4 and diode K6 maintains high the non-inverting input, thus memorising this event.

This event is indicated by lighting of the LED L2 by means of the amplifier constituted by resistors R.6 and R24 and transistor TS2. The indication remains memorised until the push button P, is operated.

The operation of the detector and indicator for overcurrent is as follows:- Through thermal probes NTC, connected together in parallel and the device by terminals M6 and M7 and which monitor temperature variations at suitable points in the electrical plant, there is sent to the inverting input of It 1/3 a voltage signal inversely proportional to the variations of temperature of the probes. When said inverting input reaches a level less than that applied to the non-inverting input through the divider constituted by resistors R27 and Rg, the output of It 1/3 saturates at a high level (signal C) and through a hysteresis and memory circuit constituted by resistor R6, capacitor C5 and diode K7 memorises the event.

This event is indicated by lighting of the LED L3 through the amplifier constituted by resistors R26 and Ra7 and transistor TS3. The indication remains memorised until the push button P, is operated.

The operation of the detector and indicator for power supply failure is as follows:- A voltage signal VE is applied through the divider constituted by resistors Rao and R" to the inverting input of It1/4. On failure of the power supply the signal VE falls to zero which causes high level saturation of IC1/4 (signal 4). This results in lighting of LED 14 through amplifier constituted by resistors R,6 and transistor TS4.

The lighting of L4 does not require memorising since in the event of return of the power supply L4 is extinguished, whilst in the case of operation of a circuit breaker I.E. upstream of the control panel by virtue of a fault in the electrical plant, L4 is lit simultaneously with L2 or L3.

The push button P, carries out also the function, through diodes K9, K", K,5, Kie of a test button for the faults indicating device.

The fault indicating device can be supplied with alphabetic indicators K.A. for indicating the above described events. In this case signals A, B, C, D are fed through logic gates IC3--IC7 to a decoding/driving circuit D.P. which activates the six element indicator K.A. (see Fig. 8A).

The combination of signals B, C, D to the logic gates IC4 supplies at the input of the decoder the indication that the circuit breaker I.E. is open and simultaneously prevents simultaneous indication of B or C and D.

The device of the invention can alternatively be powered by a suitable power supply circuit (not shown), incorporated or not in the indicating device itself.

Clearly, the invention can be subject to modications or variations in execution on the form of device on the realisation of the electronic circuit, without thus departing from the ambit of protection of the invention.

Claims

1. A fault indicating device for domestic electrical plant, comprising a compact modular body provided with means adapted to detect operation of protection and control devices of the plant and to indicate the cause of said operation.

2. A device as claimed in claim 1, comprising a boxed device of reduced dimensions to be installed in an electrical control panel or in its immediate vicinity preferably accompanied by legends which explain its use to the non-expert user.

3. A device as claimed in either claim 1 or 2 wherein there is provided a plurality of luminous lamps or indicators which are easily visible and which give indication of the origin of the fault.

4. A device as claimed in any preceding claim wherein said compact modular body is formed of a box-like structure containing the electronic circuits for detection and indication, said structure being further provided with supply terminals for said circuits, with luminous indicators and with means for location of probes and cables of the plant.

5. A device as claimed in any preceding claim wherein said box-like structure is further provided with integral means for installation of said modular body in the control panel of the electrical plant or to a wall.

6. A device as claimed in any preceding claim wherein said integral means for installation of the device to the control panel of the electrical plant is constituted by shaped shoulders extending from said box-like structure.

7. A device as claimed in any preceding claim wherein it is incorporated in a conventional electrical apparatus, such as circuit breaker or other.

8. A device as claimed in any preceding claim wherein said means adapted to detect the operation of the protection and control devices of the electrical plant and to indicate the reason for said operation is made up of a single integrated linear electronic circuit.

9. A device as claimed in any preceding claim wherein said electronic circuits are provided with sensors for variations of the electrical parameters of the plant and with as many luminous indicators as there are causes for said operation.

10. A device as claimed in any preceding claim wherein the sensors are operated on variations on electrical field, temperature, electric circuit current or other.

11. A device as claimed in any preceding claim wherein said indicators are made up of luminous warning lamps.

12. A device as claimed in any preceding claim wherein said indicators are made up of visual indicators.

1 3. A fault indicating device for domestic electrical plant substantially as hereinbefore described with reference to the accompanying drawings.