A) TECHNICAL FIELD

[0001] The present invention generally relates to energy meters and particularly to tamper detection device in energy meters. The present invention more particularly relates to a tamper detection device for high voltage-high frequency arcing in energy meter.

B) BACKGROUND OF THE INVENTION

[0002] An energy meter is a device that measures the amount of electrical energy produced in a power station or supplied to a residence, business establishment or machines. The most common type is known as a kilowatt hour meter or joule meter. When used in electricity retailing, the device records the values measured by these meters to generate a billing for the electrical power consumed. It also provides other parameters like maximum demand with date and time, kWh backups etc.

[0003] The meters may be manipulated so as to make them under-register or even run backwards, effectively allowing usage of power without paying for it. There are several forms of tampering that are effectively done on inductive meters. The magnets with a flux of more than 0.5 tesla can saturate the magnetic circuits, causing the loss of registration. Some industry traditionally inserts rectifiers in light-bulb sockets to induce DC loads. The grounded, disconnected or reversed terminals also cause misregistration. Some industries historically alternated the inductive motors and capacitive loads (such as arc-smelters) to alternately run the meters forward then backward.

[0004] The American Edison Institute estimates that the theft/tampering of electric power resulting from meter tampering are between 2 - 3% of power supplied. Utilities in South America and in South Africa estimate such losses at between 10 - 15%. As possibly billions of dollars are thus lost to the supply utilities yearly, there is economic justification for reducing such losses by taking appropriate counter measures.

[0005] The anti tamper techniques are well known in the industry. But they are not widely uses in developed countries as the tampering was rare in the developed countries. The owner of the meter normally secures the meter against such acts.

[0006] The meters are usually sealed so that the connections and mechanism cannot be tampered without breaking the seal. The meters may also measure VAR-hours (the reflected load), neutral and DC currents, ambient magnetic fields, etc. Even the simple mechanical meters can have mechanical flags that are dropped by magnetic tampering or large DC currents.

[0007] The latest computerized meters usually have counter-measures against tampering. The Automated Meter Reading (AMR) meters often have sensors that can report the opening of the meter cover, magnetic anomalies, extra clock setting, glued buttons, reversed or switched phases etc. These features are normally present in computerized meters, especially where tampering is culturally accepted. The regulatory agencies permit the meters because they are more accurate for honest subscribers.

[0008] Given the tamper resistance and sophistication of modern meters, some fraud perpetrators bypass the meter, wholly or in part, to use the power without it being recorded at their building's meter. This normally causes an increase in neutral current at the meter, which is detected and billed at normal rates by standard tamper-resistant meters.

[0009] Even if the meter's neutral connector is completely disconnected, and the building's neutral is grounded to the phantom loop, causing an unsafe house or building, metering at the substation can alert the operator to tampering. Substations normally have a high-accuracy meter for the area served. Power companies normally investigate discrepancies between the total billed and the total generated, to find and fix the power distribution problems. These investigations are an effective method of discovering the tampering events.

[0010] Thus many attempts have therefore been made to detect tampering of the metering equipment by an unauthorized user. These detection systems can be as simple as extended observation of the equipment concerned. In other cases tampering detection devices have been proposed as part of a high complex remote meter reading system.

[0011] None of the currently available detection systems sense the tampering of an energy meter due to high-voltage-high-frequency arcing using a simple circuit. Hence there is a need to develop a system and method for detecting the tampering of energy meter due to high-voltage-high-frequency (HV-HF) arcing in a non contact manner.

[0012] The abovementioned shortcomings, disadvantages and problems are addressed herein and which will be understood by reading and studying the following specification.

C) OBJECTS OF THE INVENTION

[0013] The primary object of the present invention is to develop a tamper detection system to sense the high-voltage-high-frequency (HV-HF) arcing in energy meter in a non contact manner using an inductive coupling technique.

[0014] Another object of the present invention is to develop a tamper detection system to detect the tamper due to weak electric field that may cause electrical discharge from source of electrical noise to an energy meter.

[0015] Yet another object of the invention is to develop a tamper detection system with a single transducer and associated circuit to sense tampering due to the high-voltage-high-frequency (HV-HF) arcing in energy meter.

[0016] These and other objects and advantages of the present invention will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings.

D) SUMMARY OF THE INVENTION

[0017] The above mentioned shortcomings, disadvantages and problems are addressed herein and which will be understood by reading and studying the following specification.

[0018] The various embodiments of the present invention provide a system and method to detect the tampering of energy meter due to high-voltage-high-frequency (HV-HF) arcing. The system uses the principle that the electrical energy is transferred from one circuit to another through the inductively coupled electrical conductors. According to one embodiment of the present invention, the system includes a transducer to detect HV-HF arcing. The transducer is an inductor core having 20 secondary turns. The inductor core is formed with T10 ferrite material and the inductance value of the core is approximately equal to lmH. The primary and the secondary coils are wrapped around a T10 ferrite core of very high magnetic permeability to ensure that most of the magnetic field lines produced by the primary current (high frequency electrical noise) are within the saturation region of ferrite core. Metal-noise-collector receives the signal which is channelised through primary which intern is coupled with the secondary.

[0019] The output of the transducer is applied to the signal conditioning and low pass filter (LPF) circuits. The signal conditioning is done using diodes. The LPF is used to block the noise frequencies, which lies on higher side of the frequency spectrum. The output signal of the LPF contains frequencies from the input signal in which the high frequencies attenuated but with little attenuation below the cutoff frequency of the filter. The output of the LPF is applied to two stage cascaded signal amplifier circuit having a total gain of 65. The output signal of the amplifier circuit is then compared with a reference signal at a signal comparator. The reference signal is generated by a threshold generator. The output of the comparator is fed to a signal hold circuit. The signal hold circuit is used as an interface for applying analog signals to a subsequent system such as analog to digital converter. It holds the analog signals steady for a short time when the converter performs some operation that takes little time. The final Digital output is applied to a micro-controller for time stamping of tamper detection events. The detected events along with the time stamps are recorded in permanent memory for future retrieval of the data. The detected tamper event is also displayed on a display unit.

[0020] Thus the various embodiments of the invention provide a system and method to detect the tampering of the energy meter due to HV-HF arcing in a non contact manner using an inductive coupling technique. The system provides complete electrical isolation between the source of noise and a sensing coil circuit. The system design is simplified by providing a single transducer and associated circuit to sense the HV-HF arc tampering at any place of the energy meter. The system also detects the tampering of the energy meter due to the weak electric field that may cause electrical discharge from the source of noise to the energy meter. It has an ability to withstand higher electrical discharge up to 90kV. The system stores the tamper detection event with time stamp in a permanent memory for the retrieval of data at any future date.

E) BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The other objects, features and advantages will occur to those skilled in the art from the following description of the preferred embodiment and the accompanying drawings in which:

[0022] FIG.1 illustrates a functional block diagram of the tamper detection system according to one embodiment of the present invention.

[0023] Although specific features of the present invention are shown in some drawings and not in others. This is done for convenience only as each feature may be combined with any or all of the other features in accordance with the present invention.

F) DETAILED DESCRIPTION OF THE INVENTION

[0024] In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which the specific embodiments that may be practiced is shown by way of illustration. These embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments and it is to be understood that the logical, mechanical and other changes may be made without departing from the scope of the embodiments. The following detailed description is therefore not to be taken in a limiting sense.

[0025] The various embodiments of the present invention provide a tamper detection system for high-voltage-high-frequency (HV-HF) arcing in energy meter. According to one embodiment of the present invention, the tamper detection system uses the principle that the electrical energy is transferred from one circuit to another through the inductively coupled electrical conductors. According to one embodiment of the present invention, a transducer is provided to detect a HV-HF arcing in an inductor provided in an energy meter. A signal conditioning circuit coupled with a low pass filter is connected to the transducer to remove the high frequency signal present in the output of the transducer. Two stage cascaded signal amplifiers are connected to the signal conditioning circuit to amplify the output of the signal conditioning circuit before being fed into a signal comparator.

[0026] A signal comparator is connected to the second stage signal amplifier and connected to a threshold generator. The signal comparator compares the output of the cascaded two stage signal amplifiers with the reference signal received from the threshold generator to detect a tamper event due to the HV-HF arcing to output a tamper detection signal. A signal hold circuit is connected to the signal comparator to hold the tamper detection signal before being fed into a digitizing circuit. The digitizing circuit is connected to the signal hold circuit to convert the output of the comparator into a digital signal. A microcontroller is connected to the digitizing circuit to receive the digital tamper detection signal. The microcontroller time stamps the received digital tamper detection signal and stores the received tamper detection signal in a permanent memory along with the time stamp for future reference. A display unit is connected to the micro controller to display the received tamper detection signal.

[0027] According to one embodiment of the present invention, the system includes a transducer to detect HV-HF arcing. The transducer is an inductor core having 20 secondary turns. The inductor core is formed with T10 ferrite material and the inductance value of the core is approximately equal to 1mH. The change in the current in the first-primary circuit creates a change in the magnetic field. The change in the magnetic field induces a change in the voltage in the secondary circuit. The primary and secondary coils are wrapped around a T10 Ferrite core of very high magnetic permeability. It ensures that most of the magnetic field lines produced by the primary current are within the saturation region of the ferrite core. Metal-noise-collector receives the signal which is channelised through primary which intern is coupled with the secondary.

[0028] According to one embodiment of the present invention the output of the transducer is applied to the signal conditioning and low pass filter circuit. Signal conditioning is done using diodes and the low pass filter is used to block the noise frequencies which lie on higher side of the frequency spectrum. The LPF output signal contains the input signal, in which the high frequencies are attenuated, but with little attenuation below the cutoff frequency of the filter. The output of the LPF is applied to a two stage cascaded amplifier circuit having a total gain around 65. The output signal of the cascaded two stage amplifier is then compared using signal comparator with a reference signal which is generated by a threshold generator. The final digital output is connected to the micro-controller for time stamping of event and records in permanent memory for future retrieval of the data.

[0029] The tamper detection system in the present invention has the ability to withstand higher electrical discharge up to strength of 90kV. It prevents tinker with energy meter and provides permanent evidence for future investigation. It provides permanent recording of the tamper event, duration of event, count of events in EEPROM. Hence 100Years data retention is possible.

[0030] Thus the various embodiments of the invention provide a system and method to detect the tampering of the energy meter due to HV-HF arcing in a non contact manner using an inductive coupling technique. The system provides complete electrical isolation between the source of noise and a sensing coil circuit. The system design is simplified by proving a single transducer and associated circuit to sense the HV-HF arc tampering at any place of the energy meter. The system also detects the tampering of the energy meter due to the weak electric field that may cause electrical discharge from the source of noise to the energy meter. The system stores the tamper detection event with time stamp in a permanent memory for the retrieval of data at any future date.

[0031] FIG.1 illustrates a functional block diagram of the tamper detection system 10 according to one embodiment of the present invention. With respect to FIG.1, a transducer 11 detects HV-HF arcing in an energy meter. The transducer 11 is an inductor core having 20 secondary turns. The inductor core is made of T10 ferrite material and the inductance value of the core is approximately equal to 1mH. The primary and the secondary coils are wrapped around a T10 ferrite core of very high magnetic permeability. It ensures that most of the magnetic field lines produced by the primary current (High frequency Electrical Noise) are within the ferrite core and passes through the secondary coil as well as the primary coil.

[0032] The output of the transducer 11 is applied to the signal conditioning and low pass filter (LPF) circuits 12. The signal conditioning is formed by using diodes. The LPF is used to block the noise frequencies, which lies on higher side of the frequency spectrum. The output of the LPF is applied to two stage cascaded signal amplifier circuits 12 and 13 having a total gain of 65. The output signal of the amplifier circuit 14 is then compared with a reference signal at a signal comparator 15. The reference signal is generated by a threshold generator 16. The output of the comparator 15 is fed to a signal hold circuit 17. The signal hold circuit 17 is used as an interface for applying analog signals to a subsequent system such as analog to digital converter 18. It holds the analog signals steady for a short time when the converter 18 performs some operation that takes little time. The final Digital output is applied to a micro-controller 19 for time stamping of tamper detection events. The tamper events are displayed on LCD display 20. The detected events along with the time stamps are recorded in permanent memory 21 for future retrieval of the data.

G) ADVANTAGES OF THE INVENTION

[0033] The various embodiments of the invention provide a system and method to detect the tampering of the energy meter due to HV-HF arcing in a non-contact manner using an inductive coupling technique. The system provides a complete electrical isolation between the source of noise and a sensing coil circuit. The system design is simplified by providing a single transducer and associated circuit to sense the HV-HF arc tampering at any place of the energy meter. The system also detects the tampering of the energy meter due to the weak electric field that causes electrical discharge from the source of noise to the energy meter. The system stores the tamper detection event with time stamp in a permanent memory for the retrieval of data at any future date.

[0034] The tamper detection system in the present invention has the ability to withstand higher electrical discharge up to strength of 90kV. It prevents tinkering with energy meter and provides permanent evidence for future investigation. It provides permanent recording of the tamper event, duration of event, count of events in EEPROM. Hence 100Years data retention is possible.

[0035] Although the invention is described with various specific embodiments, it will be obvious for a person skilled in the art to practice the invention with modifications. However, all such modifications are deemed to be within the scope of the claims.
[0036] It is also to be understood that the following claims are intended to cover all of the generic and specific features of the present invention described herein and all the statements of the scope of the invention which as a matter of language might be said to fall there between.

CLAIMS
What is claimed is:

1. A tamper detection system for high voltage high frequency arcing in energy meter
comprising:

A transducer;

A signal conditioning circuit connected to the transducer; A first stage signal amplifier connected to the signal conditioning circuit; A second stage signal amplifier connected to the first stage signal amplifier; A signal comparator connected to the second stage signal amplifier; A threshold generator connected to the signal comparator; A signal hold circuit connected to the signal comparator; A digitizing circuit connected to the signal hold circuit; A microcontroller connected to the digitizing circuit; A display unit connected to the micro controller; A memory connected to the microcontroller;

Wherein the microcontroller detects a tamper detection event due to high voltage-high
frequency (HV-HF) arcing based on the output of the signal comparator circuit.

2. The system according to claim 1, wherein the transducer senses the HV-HF arcing in an inductor core provided in an energy meter.

3. The system according to claim 1, wherein the signal conditioning circuit includes diodes.

4. The system according to claim 1 further comprising a low pass filter connected to the signal conditioning circuit.

5. The system according to claim 1, wherein the signal conditioning circuit and the low pass filter receives the output of the transducer to remove the noise frequencies in the output of the transducer.

6. The system according to claim 1, wherein the first stage signal amplifier is a high impedance signal amplifier circuit.

7. The system according to claim 1, wherein the first stage signal amplifier and the second stage signal amplifier are two stage cascaded amplifier circuits.

8. The system according to claim 1, wherein the first stage signal amplifier and the second stage signal amplifier amplifies the output of the signal conditioning circuit before being fed into the signal comparator.

9. The system according to claim 1, wherein the signal comparator receives the output of the second stage signal amplifier for comparing the output of the second stage signal amplifier with a reference voltage signal to detect a HV-HF arcing in the energy meter.

10. The system according to claim 1, wherein the threshold generator produces the reference signal which is fed into the signal comparator.

11. The system according to claim 1, wherein the signal hold circuit holds and conditions the output of the signal comparator.

12. The system according to claim 1, wherein the digitizing circuit digitizes the output of the signal comparator before being fed into the microcontroller.

13. The system according to claim 1, wherein the microcontroller timestamps the HV-HF arcing detection event and stored the detection event in a permanent memory for future reference.

14. The system according to claim 1, wherein the microcontroller displays the detected HV-HF arcing event on a display unit.