AU631978B2 - Electric line interference detector - Google Patents

Description

631978 S F Ref: 121672 FORM COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952 COMPLETE SPECIFICATION

(ORIGINAL)

FOR OFFICE USE: Class Int. Class Application Number: PJ9558 o Lodged: 9 April 1990 Accepted: Published: Priority: Related Art: Name and Address o of Applicant: The Prospect County Council Smith Street Parramatta New South Wales 2150

AUSTRALIA

Actual Inventor: Morris Klajman 0o Address for Service: Spruson Ferguson, Patent Attorneys, Level 33 St Martins Tower, 31 Market Street, o e Sydney, New South Wales, 2000, Australia Complete Specification for the invention entitled: Electric Line Interference Detector The following statement is a full description of this invention, including the best method of performing it known to me/us REPRINT OF RECEIPT *0207 1 22/03/91 5815/2 s -2- BACKGROUND OF THE INVENTION This invention relates to apparatus for detecting breaks in electrical signals in electrical lines, and more particularly for detecting interference with the electrlcdl lines. In one embodiment the appalratus can be used for detecting when an electricity supply line Is interfered with to try to bypass an electricity meter in order to avoid paying for the electricity consumed.

In many domestic or other general electricity supply systems, single phase electricity Is supplied via an active line and a neutral line. An electrIcity meter is connected between the active and the neutral lines along with a mains switch, a domestic fuse and the domestic load. In order to disconnect the meter, and so avoid paying for electricity which Is not metered, it is known for dishonest consumers to disconnect the neutral line from the meter which stops the meter from reglstering electricity 1 5 consumed. If the lines are later connected back to the meter in their correct positions, then It can be difficult to detect that any Interference with the electricity supply has taken place, especially if the meter is disconnected for only, perhaps, a few hours per day.

SUMMARY OF THE INVENTION Accordingly, the Invention provides apparatus for detecting a break in a substantially continuous electrical signal In a signal line coupled between a first terminal and a second terminal, the apparatus comprising a mono-directional electrically operable relay coupled across the signal line the relay having first contacts in the signal line and second contacts provided In a parallel line, the first contacts being opeit in their rest position, but being movable to a closed, activated position and the second contacts being closed in their rest position, but being movable to an opcn position when the first contacts are moved to their activated position, and indicating means provided in the parallel line in series with the second contacts, whereln the first contacts are moved to their closed, activated popiton to set the apparatus before the electrical signal passes through the signal line but are actuated by the relay to their open position when a signal present In the signal line is broken, the relay simultaneously actuating the second contacts to their closed position when opening the first contacts, whereby, when power is next present In the parallel line, the indicating means Is activated to Indicate that there was a break in the electrical signal in the signal line, csh/1034E 3 l -3- Since the relay only operates in one direction, once the second contacts are closed to activate the indicating means, they cannot be opened again to switch off the Indicating means until the relay is reset.

In a preferred embodiment of the present invention, the apparatus is coupled to a domestic power supply, the signal line being coupled between a domestic electricity meter and a supply terminal and the parallel line being coupled between two supply terminals. Preferably, the signal line is coupled between the meter and the neutral supply terminal, but could alternatively be coupled between the meter and the active supply terminal.

However, if the consumer breaks the supply to the meter, the relay actuates the two sets of contacts so that the Indicating means, for example a lamp, is activated. A drawback of this arrangement is that the relay will also be actuated if the supply to the supply terminal from the supplier is interrupted, as In a power cut. Therefore, in one embodiment of the invention ther is provided a second, similar apparatus to be coupled S to a domestic power supply wherein its supply line and the parallel line are connected between the supplier's active terminal and the supplier's neutral terminal so as to detect whether the supply between these two terminals has been interrupted. In such a case, the Indica':ing means on both apparatus will be activated, whereas if the consumer has been interfering with the supply without a power cut occurlng, then only one of the Indicating means will be activated.

In many domestic environments, there are provided two electricity meters. In such circumstances, a third apparatus could be provided with Its signal line coupled between the second meter and a supply terminal.

BRIEF DESCRIPTION OF THE DRANINGS The Invention will now be more clearly described, by way of example, with reference to the drawings, of which: Figure 1 shows one embodiment of a simple form of the Invention In schematic form, and Figure 2 shows a second embodiment of the present invention used In a domestic power supply system.

DETAILED DESCRIPTION OF THE EMBODIMENTS OF THE INVENTION Thus, there is shown In Figure 1 a line 1 coupled between an active terminal 2 and a neutral terminal 3. An electric signal passes between the terminals via the line, If the line Is Interfered with in any way, then csh/1034E -4the signal is broken. When the line is reconnected, however, the signal passes between the terminals once more and there is no indication that it had ever been broken.

Therefore, the invention provides a relay 5 coupled in the line 1 between the active terminal 2 and the neutral terminal 3. The relay 5 is a mono-directional electrically operable relay which comprises first contacts 6 provided in the signal line 1 and second contacts 7 provided in a parallel line 8 coupled between the active and the neutral terminals 2,3.

The first contacts 6 have an open, rest position, as shown, and can be set to a closed activated position, to which they are manually set when the apparatus is connected in a circuit.

The second contacts have a rest, closed position, as shown, and an open position to which they are moved when the first contacts are set to their activated position.

Accordingly, once the apparatus is in place and the contacts have been set to their activated positions, i.e, the first contacts 6 are closed and the second contacts 7 are open, as long as a signal passes continuously through the signal line 1, the first contacts 6 remain closed and the second contacts 7 remain open. However, If the signal In the signal line Is broken, relay 5 actuates the first and second contacts 6 and 7 simultaneously. In this case, second contacts 7 are closed and electrical power passes through the parallel line 8. This activates an Indicating 0 device, such as a lamp 9, provided In the parallel line 8.

It will be appreciated that although the Indicating device has been described as a lamp, it could alternatively tu an alarm of some sort and could be a radio transmitter to produce an alarm at a receiver at a remote location, Furthermore, it will be appreciated also, that, since the relay 5 is mono-directional, it will not actuate the first and second contacts back again when the signal recommences. Thus, the lamp 9 will remain on until the relay is deliberately reset, The relay could be manually resettable or could be resettable remotely by, for example radio signals from a remote location, In Figure 2 there Is shown the circuit of Figure 1 coupled Into a domestic electricity supply circuit. The domestic supply circuit Is powered from supplier's active terminal 10 and supplier's neutral terminal 11. The active terminal 10 is coupled to a domestic line 12 via a supplier csh/1034E Y 1Slj/~i fuse 13 and the neutral terminal Is coupled to the domestic line via a supplier neutral link 14. The domestic electrical load Is shown schematically as two sub-circuits, each comprising a load 15 and 16, a sub-circuit fuse 17 and 18, and a main switch 19 and 20. Each sub-circuit is coupled to the supplier neutral link 14 via domestic neutral links 21 and 22. Furthermore, each sub-circuit Is provided with an electricity meter 23 and 24 coupled across the domestic line 12.

In order to detect interference with the domestic electricity supply, in this embodiment, there are prov'ded two circuits A and B of the type described above with reference to Figure 1. Since each of these circuits have the same components as the circuit of Figure 1, the components will be referred to by the same reference niumerals but with additional letters A and B to distinguish between the two circuits.

Circuit A is arranged such that its signal line 1A is coupled between the domestic line 12 and the neutral terminal on meter 23 and with its parallel line 8A coupled between the domestic line 12 and the supplier neutral link 14. Circuit B is arranged such that its signal line IB is coupled between the domestic line 12 and the neutral terminal on meter 24 and with its parallel line 8B coupled between the domestic line 12 and the supplier neutral link 14. Thus the two circuits A and B are generally identically coupled except for the signal lines 1A and IB which are coupled to respective meters 23 and 24.

In both circuits A and B, the first contacts 6A and 6B are set to the S° activated, closed position, as shown in circuit A, and second contact, 7A 1 25 and 7B are therefore set to their open position, as shown in circuit B. It will be apparent that when power passes through the loads 15 and 16, it is measured by meters 23 and 24. In this sltuation, relays 5A and 5B are not actuated and contacts 6A, 6B, 7A and 7B remain in their set positions.

j Thus the lamps 9A and 9B remain off, as shown in circuit A.

However, if the connections to the meter are Interfered with, for example, to try to disconnect the meter so as to obtain electricity without It being metered, as shown schematically In Figure 2 by switch 25 shown in an open position to Indicate interference with meter 24, then the relay, in this case relay 5B, will actuate contacts 6B and 7B. This causes the lamp 9B of circuit B to be activated as an Indication that the connections to meter 24 have been Interfered with, csh/1034E a L LLLL~Cll~t~LI~_ -6- It will be apparent, however, that the relays 5A and 5B will also be actuated if there is a power cut on the suppliers side since this will also cause a break in the power through the signal lines IA and 1B of circuits A and B causing both lamps 9A and 9B to be activated when power retu-ns.

Thus, lamps 9A and 9B will be activated whether the consumer has interfered with the meters 23 and 24 or whether there is a power cut. Accordingly, it is desirable to provide a means for distinguishing between these two situations.

Therefore, a third circuit C, similar to that described above with reference to Figure 1, is provided with its signal line 1C coupled between the active terminal 10 on the suppliers side of supplier fuse 13 and supplier neutral link 14. The signal line is also provided with a supplier fuse 26 to protect the circuit C from surges in power from the supplier.

The parallel line 8C is coupled between domestic line 12 and supplier neutral link 14.

Now, If there is a power cut on the suppliers side, then relay actuates contacts 6C and 7C. Thus, when power is returned lamp 9C will be activated, as we'l as lamps 9A and 9B. It will therefore be possible to distinguish between the situation where there has been a supplier's power cut when all three lamps 9A, 9P and 9C are activated, and the situation where the consumer has interfered with the two meters 23 and 24 but there has not been a power cut when only lamps 9A and 9B are activated.

Although this embodiment of the invention has been described with two domestic sub-circuits having two electricity meters, it will be apparent that the principle of the invention will apply to any number of separate circuits where unauthorised interference could take place. Furthermore, although the embodiment has been described with an extra circuit for detecting supplier's power cuts, It will also be apparent that such a circuit is not essential, particularly if the supplier has other methods for determining whether power cuts have occurred.

It will therefore be appreciated by persons skilled in the art that the basic principle of the invention can be utilised In a much wider range of cicumstances and situations than those described here and it will also be appreciated that all such uses and applications of the principle of the invention are Intended to be covered.

csh/1034E

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Claims (9)

1. An apparatus for detecting a break in a substantially continuous electrical signal in a signal line coupled between a first terminal and a second terminal, the apparatus comprising a mono-directional electrically operable relay coupled across the signal line the relay having first contacts in the signal line and second contacts provided in a parallel line, the first contacts being open in their rest position, but being movable to a closed, activated position and the second contacts being closed in their rest position, but being movable to an open position when the first contacts are moved to their activated position, and indicating means provided In the parallel line in series with the second contacts, wherein the first contacts are moved to their closed, activated position to S set the apparatus before the electrical signal passes through the signal line but are actuated by the relay to their open position when a signal present in the signal line is broken, the relay simultaneously actuating the second contacts to their closed position when opening the first contacts, whereby, when power is next present In the parallel line, the indicating means is activated to Indicate that there was a break In the electrical signal In the signal line.

2. An apparatus according to claim 1, whereln the apparatus Is coupled to a domestic power supply, the signal line being coupled between a domestic electricity meter and a supply terminal and the parallel line being coupled between two supply terminals.

S3, An apparatus according to claim 2, whereln the signal line Is coupled between the meter and a neutral supply terminal.

4. An apparatus according to claim 2, wherein the signal line is coupled between the meter and an active supply terminal.

An apparatus for detecting a break in a domestic power supply comprising an apparatus according to any one of claims 2 to 4, and a further second, similar apparatus coupled to the domestic power supply but having its supply line and parallel line connected between the supplier's active terminal and the supplier's neutral terminal so as to detect whether the supply between these two terminals has been interrupted.

6, An apparatus according to any preceding claim, whereln the Indlcatlng means comprises a light emitting means,

7. An apparatus according to any preceding claim, whereln the Indicating means comprises transmitting means for transmitting an alarm signal to a remote location. csh/1034E L 1 1111-'1~ -8-

8. An apparatus according to claim 7 wherein said transmitting means is a radio transmitter.

9. An apparatus for detecting a break in a substantially continuous electrical signal In a signal line substantially as hereinbefore described with reference to either Figure 1 or Figure 2 of the drawings. An apparatus for detecting a break in a domestic power supply substantially as hereinbefore described with reference to Figure 2 of the drawings. DATED this TNENTY-FIRST day of MARCH 1991 o The Prospect County Council f o S Patent Attorneys for the Applicant SPRUSON FERGUSON L I o 0 0 csh/1034E NM