WO1999031519A1

WO1999031519A1 - Device for detecting illicit tapping of current from a mains electricity supply

Info

Publication number: WO1999031519A1
Application number: PCT/NL1998/000667
Authority: WO
Inventors: Maarten Baardman
Original assignee: Maarten Baardman
Priority date: 1997-12-17
Filing date: 1998-11-19
Publication date: 1999-06-24
Also published as: PE20000201A1; AU1264399A; BR9813821A; ID26276A; NL1008606C1; AR017836A1

Abstract

The invention relates to a device for detecting current tapped illicitly from a mains electricity supply, which device comprises: detecting means for detecting a difference between a first current through a first core respectively the sum of the first currents through a number of first cores and the second current through a second core respectively the sum of the second currents through a number of second cores, which first current respectively the sum of which first currents is the same under normal operating conditions as the second current respectively the sum of the second currents, which cores form part of a power consumption circuit which forms part of or is connected to a branch cable, in which circuit a supply meter is incorporated which registers the amount of consumed electrical energy; and switching means for generating a detection signal under the control of the detecting means when a certain difference between said currents is detected, which signal controls the coil of a relay, which relay comprises a switch contact which is arranged in one of said cores such that the switch contact is opened and the current flow is interrupted.

Description

DEVICE FOR DETECTING ILLICIT TAPPING OF CURRENT FROM A MAINS ELECTRICITY SUPPLY

For electricity producers who supply consumers with electrical energy via a mains electricity supply it may be a problem that it is often relatively easy to extract electrical current from the mains supply in a manner such that the electricity supply meter is bypassed and payment is therefore not made for the thus obtained energy.

It is an object of the invention to furnish provisions which detect the illicit and unpaid removal of electrical energy from a mains supply and which effec- tively switch off the current supply immediately on such a detection.

The stated objective is realized according to the invention with a device for detecting current tapped illicitly from a mains electricity supply, which device comprises : detecting means for detecting a difference between a first current through a first core respectively the sum of the first currents through a number of first cores and the second current through a second core respectively the sum of the second currents through a number of second cores, which first current respectively the sum of which first currents is the same under normal operating conditions as the second current respectively the sum of the second currents, which cores form part of a power con- sumption circuit which forms part of or is connected to a branch cable, in which circuit a supply meter is incorporated which registers the amount of consumed electrical energy; and switching means for generating a detection signal under the control of the detecting means when a certain difference between said currents is detected, which signal controls the coil of a relay, which relay comprises a switch contact which is arranged in one of said cores such that the switch contact is opened and the current flow is interrupted.

Since the neutral conductor in some mains supplies (three-phase supplies in star configuration) is connected to earth, the device can have the special feature that the switch contact is incorporated in a phase conductor. It will otherwise be apparent that the switch contact must be incorporated in each circuit for safeguarding. In the case of more than one phase conductor a switch con- tact will thus have to be incorporated in each phase conductor in the latter described case.

The currents in question can be measured in any suitable manner. An embodiment is however recommended which detects the relevant differences in currents and controls the relay correspondingly without contact with the conductors and as far as possible in completely passive manner. In this respect a device can be applied in which the detecting means comprise a number of ferromagnetic rings which each extend round a respective conductor and round which a detection coil is arranged, which two coils are arranged in differential configuration in series with each other, wherein the free terminals can generate the detection signal.

Inasfar as conditions allow, a device can also be used in which the detecting means comprise a ferromagnetic ring which extends round the relevant conductors and round which a detection coil is arranged, the terminals of which can generate the detection signal. A prerequisite herefor is that the relevant conductors are situated relatively close together such that it is possible to suffice with a reasonably small ferromagnetic ring. This embodiment is simpler than the above described embodiment with a plurality of rings. This latter embodiment is moreover not subject to any imbalance in the case of inequality between the diverse rings involved as according to the first described embodiment.

A very low detection threshold can be realized with an embodiment in which an amplifier, optionally in combi- nation with a rectifier, is connected between said terminals and the relay.

In an embodiment in which the detecting means comprise a ferromagnetic ring with detection coil, the device can advantageously have the special feature that the ferromagnetic ring can be divided into two segments such that it can be arranged round a conductor or a group of conductors without interrupting this conductor. With such an embodiment the device according to the invention can be placed without intruding into the electricity lines and even without any electrical contact with these lines .

A preferred embodiment has the special feature that the device is closable and/or lockable such that the switch contact can only be re-closed by authorized personnel after opening thereof.

The device is preferably designed such that the detecting means comprise a current transformer such that the cores are electrically separated from the switching means.

It should be appreciated that the term current transformer must be interpreted in the broad sense. Two conductors which are present in the vicinity of each other and which have at least one common directional component can for instance already be seen as a current transformer. More practical however is an embodiment in which for instance a conductor extends in the form of a coil round another conductor. An embodiment can also be envisaged in which the current transformer comprises a ferromagnetic core, for instance a ferrite core. In this case a considerably improved detection sensitivity can be realized due to the ferromagnetic properties of the core.

A very practical embodiment is that in which two cores or groups of cores are collectively coupled magnet- ically to a detection coil incorporated in a circuit which includes the relay coil.

According to yet another aspect of the invention, the device has the feature that the switch configuration is such that the device also fulfils the function of earth leakage switch.

The invention generally aims at detecting an imbalance or inequality between two currents or sums of cur- rents which in normal operating conditions are the same. In the case a difference is detected, this difference can only be interpreted as an impermissible outside intrusion, whereby correct registering of the amount of energy used is in danger of being prevented. Immediate closing of the energy take-off option takes place in this case.

The invention thus acts to detect an illegal intrusion by third parties as well as in preventive manner. In accordance with the last described aspect according to the invention, the device can also fulfil the function of earth leakage switch, in which cases it enhances safety.

The embodiment will now be elucidated with reference to the annexed drawings. Herein: figure 1 shows a block diagram of an embodiment; figure 2 is a perspective view of detecting means in a first embodiment; figure 3 shows a view corresponding with figure 2 of detecting means in a second embodiment; figure 4 shows a block diagram of a second embodiment ; figure 5A shows a block diagram of a third embodiment ; figure 5B shows a -variant which also fulfils the function of earth leakage switch; figure 6 shows yet another embodiment which can detect bypassing of the supply meter; figure 7 shows yet another embodiment in schematic manner; figures 8-19 show respectively a circuit diagram and a number of switching options which illustrate illicit tapping of electrical current as well as the manner in which the device according to the invention intervenes on the basis thereof; and figure 20 shows an application diagram of the device according to the invention in a three-phase mains electricity supply.

Figure 1 shows a mains electricity supply which is designated symbolically with a phase conductor 1 and a neutral conductor 2. A branch phase conductor 3 is connected to phase conductor 1, while a branch neutral conductor 4 is connected to neutral conductor 2. A current detection device 5 is incorporated in conductor 3, while a current detection device 6 is incorporated in conductor 4. The output of devices 5 and 6 are connected in differential circuit via respective terminals 7 and 8 to the coil 9 of relay 10 which comprises a switch contact 11. In normal conditions switch contact 11 is to be found in the drawn situation in which it connects onto the circuit via a contact 12. Branch phase conductor 3 is hereby connected to consuming station 13, for instance a housing. When as a result of manipulations inside consuming station 13 an inequality or imbalance occurs between the currents through conductors 3 and 4, a voltage will occur between terminals 7 and 8 which activates relay 10, whereby switch contact 11 disengages from contact 12 and comes to rest against fixed contact 14 which is not connected. The whole circuit is hereby interrupted imme- diately. Since the whole device consisting of devices 5 and 6 and relay 10 is accommodated in a closable and optionally lockable housing, the active position of contact 11 shown in figure 1 can only be restored by authorized personnel, i.e. personnel of the provider of the mains electricity supply.

Switch contact 11 has two stable positions corresponding respectively with contact 12 and contact 14. Contact 12 corresponds with the operational mode shown in figure 1. When coil 19 of relay 10 is activated, a force is exerted on switch contact 11 such that it moves from the active stable position (12) to the passive position (14) . After gaining access to relay 10, authorized personnel can restore the current flow by resetting relay 10, for which purpose switch contact 11 is re-placed to make contact with the fixed active contact 12.

Alternatively a relay with hold circuit can also be used. In this case the relay comprises two make-and-break contacts, wherein the one closes a hold circuit when the relay is activated. When the hold circuit is interrupted, resetting to the situation shown in figure 1 takes place. Figure 2 shows a practical implementation of devices 5 and β. These each comprise a ferromagnetic ring 44, 45 respectively which can be divided via plane sections, all designated with 16, and comprise respective detection coils 17 and 18. These are connected in differential configuration in series with each other.

Figure 3 shows a very simple and elegant embodiment in which both conductors 3 and 4 are jointly enclosed by ring 44, of which the free terminals 7 and 8 are connected to the coil 9 of relay 10.

It will be apparent that the device according to the invention is placed between the branch zone of main conductor 1, 2 of the mains supply and the supply meter in consuming station 13. The device according to the invention can be arranged at any suitable location, for instance in the region from the branch zone of mains supply 1, 2 to branch conductors 3 , 4 on the outside of consuming station 13 or inside this station 13, depending on local conditions.

Since in the embodiment of figure 2 or 3 the device operates in wholly contact-free manner and is based solely on magnetic transfer of electrical energy in the manner of a transformer, the device can be exceptionally simple, reliable and safe.

Figure 4 shows a second embodiment. In this embodiment use is made of a small kWh-meter 21 which serves to register the energy taken from the mains supply by con- suming station 13. The electricity producer bills the consumer on the basis thereof. Meter 21 comprises four terminals 22, 23, 24, 25. Terminals 22, 23 and terminals 24, 25 are connected to respective circuits. Meter 21 registers energy consumption only in the case where current flows through both circuits.

Figure 4 shows a detector 26 which is constructed in the same manner as the detector in the combination of figures 1 and 3.

In the case of attempted illicit tapping of current through a consuming station 31, the user will connect a pole 32 to conductor 33 which is connected to terminal 25. In the case the "free" terminal 34 is connected to any of the cores A, B, C or D, as shown in figure 4, the following events will take place:

A: A flux differential is detected by ring core 14 whereby relay 9, 11 is placed into the mode in which contact 11 is displaced from the active contact 12 to the inactive contact 14.

B: In this case a current differential is also induced through lines A and B, whereby switch-off takes place as a result of the occurring flux differential. C: In this case detector 26 measures no current differential and the kWh-meter 21 simply measures the consumed energy. This can of course be immediately understood from the fact that in this case the stations 13 and 31 are connected in parallel.

D: In this case there occurs no voltage differential between terminals 32 and 34 so that no illicit energy can be tapped either.

Figure 5A shows a configuration in which an additional detector 41 is arranged between lines B and C. The construction is identical to that of detector 26 in lines A, B. This detector provides additional security, particularly also in the case that terminal 32 is connected to a terminal and core other than those mentioned. This detector 41 monitors in particular direct connections between A and B and C and D. As stated, meter 21 operates solely on the basis of current flow through both circuits 22, 23; 24, 25. A user could therefore attempt to short- circuit the circuits in question, whereby meter 21 does not register the related use and current can therefore be tapped illicitly from the mains supply without payment. It will be apparent that each of the two detectors must be positioned at a location such that the secured part of the installation is as large as possible. In the case of countries with above-ground power lines, it is possible for instance to envisage placing of detector 5, 6 or 26 on the branch zone between main conductor 1, 2 and branch line 3, 4. Alternatively, this detector can be placed on the outside or the inside of the housing in question in the immediate vicinity of the infeed of line 3, 4. The second detector 41 can be placed for instance in the immediate vicinity of kWh-meter 21.

Figure 5B shows a circuit which corresponds in large part with a circuit as according to figure 5A. At variance with this circuit, cores A' and D', which in normal conditions correspond electrically with cores A and D of figure 5A, also extend through the ferrite core in detector 41. Thus, in addition to detecting and preventing illicit tapping of electric current, the device according to figure 5B can also contribute towards safety since in this configuration it also fulfils the function of earth leakage switch. Attention is drawn to the fact that in the case of a typical earth leakage switch, which serves only for safety purposes, the user himself is in a position to set the device into operation again. With a view to the function of prevention of illicit tapping of current, this is not possible in the case of the circuit according to figure 5B. Figure 6 shows an embodiment in which a supply meter 42 and a current transformer 43 are accommodated in a housing 41. Transformer 43 is connected in series to a current transformer 44 upstream of supply meter 42, wherein current transformers 43 and 44 are arranged in differential configuration in series with coil 45 of a relay of which switch contact 46 is connected in series to phase conductor 3. Components 44, 45, 46 are accommodated in a housing 47 and inaccessible to a consumer. In the case a consumer attempts to bypass supply meter 42 in one or other manner, he can only do this by mutually connecting points P and Q or P and R. As a result of the created imbalance the differential configuration will immediately respond, whereby switch contact 46 is opened. The configuration of figure 6 is embodied such that the cores 53, 54 together forming a detection circuit carry only very little current and therefore need only a small diameter, in contrast to the power-carrying cores 3, 4 and the consuming circuit connected thereto.

Figure 7 shows a differential configuration having only one ferrite core 48 with a detection coil 49 which is connected to coil 45 of a relay 50. It is shown that core 51, which is connected in series to a consuming station 52 designated as lamp, comprises a number of parts which pass through the plane of ring core 48 respectively in the one and in the other direction. This offers diverse security options depending on the desired configuration . Figures 8-19 relate to a detection device according to the invention in a single-phase configuration. Figures 8-19 show the configuration which corresponds almost fully with that of figure 5A.

Figure 8 shows the basic configuration wherein only the lamp 32, which is chosen as symbol of the electrical energy consumption, is connected in the normal manner, wherein the consumption^* is registered by supply meter 42. The separation 72 indicates the transition between "outside" and "inside". Arrow 73 designates the outside area; arrow 74 designates the inside area.

An arrow 75 shows the complete circuit in this normal, nominal configuration. It is apparent that the whole of the current through lamp 32 also flows through supply meter 42 so that correct registration of the consumption takes place. Because detection devices 26, 41 are subjected to the flow of two equal currents, the associated current transformers generate no current and relay 9 is not activated, so that the switch 11, which in this case takes a dual form, remains in its closed position.

Figure 9 shows the situation in which a lamp 31 is connected illicitly between terminals 61 and 64. The current is designated in this case with 76. It does not pass through supply meter 42. In this case the currents through detection device 26 are unequal. If the limit value, which amounts for instance to several hundred mA, is exceeded, relay 9 is activated and shut-off of the current supply takes place.

Figure 10 shows the situation in which lamp 31 is connected between points 62 and 64. The current 77 causes unequal flows through detection device 41, which once again results in activation of device 41 and switch-off of the effective current supply.

Figure 11 shows the connection of lamp 31 between points 63 and 64. Detection device 41 is also activated in this case and the current supply interrupted.

No further elucidation of figures 12 and 13 will be necessary after the above explanation. The currents are designated respectively 79 and 80 therein.

Figure 14 illustrates a method of illicit tapping of current, wherein terminals 61 and 63 are mutually connected and the lamp is connected between points 63 and 64. In this case the detection device 26 will come into operation and open switch 11 when sufficient current is being tapped.

The same applies for the embodiment according to figure 15 in which points 61, 62 and 63 are mutually interconnected in illicit manner and the lamp is connected between these points and point 64.

Figures 16, 17, 18 and 19 show further methods of illicit tapping of current. No matter what attempts are made to enable this illicit tapping either without caus- ing the supply meter to register consumption or without causing the system to switch itself off, these attempts will fail. It is self-evident that this is conditional on the detection devices being inaccessible to persons other than authorized personnel. Resetting of the disabled situation to a normal situation of use may also only be possible by an authorized official.

Figure 20 shows a three-phase configuration which consists essentially of three sections as according to figure 8. The phases are designated in accordance with accepted convention as R, SNT. For the sake of convenience the relevant currents, which in this configuration are removed quite legally and registered by supply meters 42, are designated with 75.

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Claims

1. Device for detecting current tapped illicitly from a mains electricity supply, which device comprises: detecting means for detecting a difference between a first current through a first core respectively the sum of the first currents through a number of first cores and the second current through a second core respectively the sum of the second currents through a number of second cores, which first current respectively the sum of which first currents is the same under normal operating condi- tions as the second current respectively the sum of the second currents, which cores form part of a power consumption circuit which forms part of or is connected to a branch cable, in which circuit a supply meter is incorporated which registers the amount of consumed electrical energy; and switching means for generating a detection signal under the control of the detecting means when a certain difference between said currents is detected, which signal controls the coil of a relay, which relay compris- es a switch contact which is arranged in one of said cores such that the switch contact is opened and the current flow is interrupted.

2. Device as claimed in claim 1, wherein the first core is a phase conductor and the second core a neutral conductor.

3. Device as claimed in claim 1, wherein the detecting means comprise a current transformer such that the cores are electrically separated from the switching means .

4. Device as claimed in claim 3, wherein two cores or groups of cores are collectively coupled magnetically to a detection coil incorporated in a circuit which includes the relay coil. _{1 3}

5. Device as claimed in claim 3 or 4 , wherein the current transformer comprises a ferromagnetic core, for instance a ferrite core.

6. Device as claimed in claim 3, wherein the detect- ing means comprise a number of ferromagnetic rings which each extend round a respective core and round which a detection coil is arranged, which two coils are arranged in differential configuration in series with each other, wherein the free terminals can generate the detection signal.

7. Device as claimed in claim 4, wherein the detecting means comprise a ferromagnetic ring which extends round the relevant cores and round which a detection coil is arranged, the terminals of which can generate the detection signal.

8. Device as claimed in claim 6 or 7, wherein an amplifier, optionally in combination with a rectifier, is connected between said terminals and the relay.

9. Device as claimed in claim 6 or 7, wherein the ferromagnetic ring can be divided into two segments such that it can be arranged round a core or a group of cores without interrupting this core.

10. Device as claimed in claim 1, wherein the device is closable and/or lockable such that the switch contact can only be re-closed by authorized personnel after opening thereof.

11. Device as claimed in any of the foregoing claims, wherein the switch configuration is such that the device also fulfils the function of earth leakage switch.