THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE NATURE OF THE INVENTION

TAMPER DETECTION DEVICE FOR DETECTING THE TAMPERING OF NEURTRAL LINE IN ENERGY METER
A) TECHNICAL FIELD
[0001] The present invention generally relates to an energy meter such as watt- hour meter used for measuring the domestic and industrial electrical power consvimption and particularly to sensor devices used for detecting a tampering event in the energy meter. The present invention more particularly relates to a solid state device used for detecting the tampering of the neutral line in energy meter.
B) BACKGROUND OF THE INVENTION
[0002] An electric meter or energy meter is a device that measures the amount of electrical energy supplied to a residence or business. The most common type is more properly known as a (kilo) watt-hour meter or a joule meter. The most common unit of measurement on the electricity meter is the kilowatt-hour which is equal to the amount of energy used by a load of one kilowatt over a period of one hour, or 3,600,000 joules. The demand is normally measured in watts, but averaged over a period, most often a quarter or half hour.
[0003] The meters for measuring single phase energy are also available. It also provides capabilities like Maximum demand with date & time, a kWh Backups. The modem electricity meters operate by continuously measuring the instantaneous voltage (volts) and current (amperes) and finding the product of these to give instantaneous electrical

power (watts) which is then integrated against time to give the energy used (in joules, kilowatt-hours etc). The meters fall into two basic categories such as electromechanical meter and electronic meter.
[0004] The most common type of electricity meter is the electromechanical induction meter. The electromechanical induction meter operates by counting the revolutions of an aluminum disc which is made to rotate at a speed proportional to the power. The number of revolutions is thus proportional to the energy usage. It consumes a small amount of power, typically around 2 watts.
[0005] The metallic disc is acted upon by two coils. One coil is connected in such a way that it produces a magnetic flux in proportion to the voltage and the other produces a magnetic flux in proportion to the current. This produces eddy currents in the disc and the effect is such that a force is exerted on the disc in proportion to the product of the instantaneous current and voltage. A permanent magnet exerts an opposing force proportional to the speed of rotation of the disc so that the rotation of the disc is stopped, when power is not supplied. As a result, the disc is rotated at a speed proportional to the power being used. The type of meter described above is used on a single-phase AC supply. Different phase configurations use additional voltage and current coils.
[0006] Some of the electricity meters are solid state type and they display the power used on an LCD module, while the electronic meters can be read automatically. In addition to the measurement of the consumption of the electrical power, the solid state meters may also record other parameters of the load and supply such as the maximum demand, the power factor and the reactive power used, etc. They may also include the electronic real

time clock mechanisms to compute a value, rather than an amount, of the electricity consumed, with the pricing varying by the time of day, day of week, and seasonally.
[0007] The AMR (Automatic Meter Reading) and RMR (Remote Meter Reading) describe the various systems to check the meters without sending a meter reading personnel to meter spot. This may be effectively achieved by using the off-site metering technology. The electronic meter is placed at the junction point where all the connections originate, inaccessible to the end-user, and it relays the readings via the AMR technology to the utility.
[0008] The meters may be manipulated so as to make them under-register or even run backwards, effectively allowing the usage of power without paying for it. There are several forms of tampering that are effectively done on inductive meters. The magnets above 0.5 tesla can saturate the magnetic circuits, causing the loss of registration. Some industry traditionally inserts the 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 forwardly and then backwardly.
[0009] The neutral lines connecting the energy meter with the load and with the AC power supply may be disconnected and the load and the AC power supply main is directly connected to the load to supply the electrical power to the load directly thereby by passing the energy meter so that the actual consumption is not registered and hence a loss of revenue to the electricity supply and distribution company is generated.

[0010] So there is a need to develop a system to detect the tampering of the energy meters by disconnecting the incoming and the outgoing neutral lines from and to the electrical energy meter.
C) OBJECT OF THE INVENTION
[0011] The primary object of the present invention is to detect the tampering of the energy meter by the disconnection of neutral lines to the energy meter from the load and the mains supply.
[0012] Another object of the present invention is to indicate the tampering of the energy meter by the disconnection of the neutral lines by providing a visual display thereby preventing the energy theft.
[0013] Yet another object of the present invention is to measure the power consumption accurately even during the disconnection of the neutral line.
[0014] 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
[0015] The abovementioned shortcomings, disadvantages and problems are addressed herein and which will be understood by reading and studying the following specification.

[0016] The various embodiments of the invention provide a system and a method to detect the tampering of the energy meter by disconnecting the neutral lines that connect the energy meter with the load and the AC mains supply.
[0017] According to the preferred embodiment of the present invention, a potential transformer and current transformer (PTCT) is connected to the metering circuit to detect the disconnection of the neutral line from and to the energy meter to detect the tampering of the energy meter and to provide a visual display to indicate the tampering of the energy meter. The PTCT transformer is used to detect the disconnection of neutral at the incoming and out going points and provides power supply to record the Cumulative KWh consumed by assuming 240Vac and one of the load current. The LED and LCD backlit indication display the disconnection of the neutral.
[0018] The PTCT transformer is operated normally in the saturation region. In the normal operating condition, the phase current and the neutral current are passed through the PTCT in opposite directions. Since the currents are passed in mutually opposite directions, the flux produced by the currents are equal in magnitude but opposite in direction so that the flux generated due to the phase and neutral currents cancels each other. And the resultant flux is zero.
[0019] In a fault condition where the neutral lines to the energy meter from the load and the mains are disconnected, the phase current and the neutral current passed through the

core do not cancel each other. Hence there is an imbalance in the current supplied to the core. As a result the core is energised by either the phase current or by the neutral current to indicate the disconnection of the neutral line at the incoming and the outgoing points. Either the phase current or the neutral current will be zero during the faulty condition.
[0020] Normally for the current transformer, the secondary load impedance should be low and for the voltage transformer the load impedance should be high. Thus the load is dynamically varied according to the load current. It has voltage and current transformer characteristics. The Current transformer is used as a voltage transformer by selecting suitable and appropriate core. The dimensions of the core and the secondary winding are adjusted to get optimum performance. The special custom made transformer is made up of rolls of silicon steel alloy. The core starts saturating at primary current of 2A and above. The Load current may be varied up to 75A. There is no more magnetic coupling on the PTCT transformer due to operation of PTCT transformer in saturation region. The magnetic coupled power is used for generating DC Voltage. Since neutral is disconnected, no reference voltage is available for measurement. A local reference voltage is generated and is used in common. The voltage and the current information are required for calculating the energy consumption.
[0021] In faulty wiring condition, no neutral connection is available at the incoming and out going point of the meter. A DC current equivalent to 240V AC is generated and fed for measuring the energy consumed during the faulty condition or during the disconnection of the neutral line. During the faulty condition of the energy meter, the

[0024] A LED or back lit LCD is provided to indicate the disconnection of the neutral line in the energy meter visibly. The LED or the back lit LCD is switched on during the normal operation. The LED or the back lit LCD is switched off during the faulty condition to indicate the disconnection of the neutral line.
[0025] Thus the tampering of the energy meter by disconnecting the neutral lines is detected reliably and the actual consumption is measured even after the disconnection of the neutral line. The disconnection of the neutral line is indicated visually to alert the authorities.
[0026] 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.
E) BRIEF DESCRIPTION OF THE DRAWINGS
[0027] 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:
[0028] FIGURE. 1 illustrates a block diagram of a neutral line tamper detection device for energy meter according to one embodiment of the present invention.

[0029] FIGURE. 2 illustrates the B-H curve due to the magnetic flux generated due to the passage of phase and neutral current in the energy meter according to one embodiment of the present invention.
[0030] FIGURE. 3 illustrates a schematic wiring diagram of the energy meter during normal operating condition according to one embodiment of the present invention.
[0031] FIGURE. 4 illustrates a schematic wiring diagram of the energy meter during tampered operating condition according to one embodiment of the present invention.
[0032] FIGURE. 5 illustrates a flow chart indicating the neutral line tamper detection method according to one embodiment of the present invention.
[0033] FIGURE. 6 illustrates a schematic wiring diagram of potential transformer current transformer (PTCI) connected to energy meter according to one embodiment of the present invention.
[0033] 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
[0034] In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which the specific embodiments which may be practiced is shown by way of illustration. These embodiments are described in sufficient detail to enable those sidlled 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.
[0035] The various embodiments of the present invention provide a system and method to detect the disconnection of the neutral line in the energy meter to detect the tampering of the energy meter.
[0036] According to the preferred embodiment of the present invention, a potential transformer and current transformer (PTCI) is connected to the metering circuit to detect the disconnection of the neutral line from and to the energy meter to detect the tampering of the energy meter and to provide a visual display to indicate the tampering of the energy meter. The PTCT transformer is used to detect the disconnection of neutral at the incoming and out going points and provides power supply to record the Cumulative KWh consumed by assuming 240Vac and one of the load current. The LED and LCD backlit indication display the disconnection of the neutral.

[0037] The PTCT transformer is operated normally in the saturation region. In the normal operating condition, the phase current and the neutral current are passed through the PTCT in opposite directions. Since the currents are passed in mutually opposite directions, the flux produced by the currents are equal in magnitude but opposite in direction so that the flux generated due to the phase and neutral currents cancels each other. And the resultant flux is zero.
[0038] In a fault condition where the neutral lines to the energy meter from the load and the mains are disconnected, the phase current and the neutral current passed through the core do not cancel each other. Hence there is an imbalance in the current supplied to the core. As a result the core is energised by either the phase current or by the neutral current to indicate the disconnection of the neutral Une at the incoming and the outgoing points. Either the phase current or the neutral current will be zero during the faulty condition.
[0039] Normally for the current transformer, the secondary load impedance should be low and for the voltage transformer the load impedance should be high. Thus the load is dynamically varied according to the load current. It has voltage and current transformer characteristics. The Current transformer is used as a voltage transformer by selecting suitable and appropriate core. The dimensions of the core and the secondary winding are adjusted to get optimum performance. The special custom made transformer is made up of rolls of silicon steel alloy. The core starts saturating at primary current of 2A and above. The Load current may be varied up to 75A. There is no more magnetic coupling on the PTCT transformer due to operation of PTCT transformer in saturation region.

The magnetic coupled power is used for generating DC Voltage. Since neutral is disconnected, no reference voltage is available for measurement. A local reference voltage is generated and is used in common. The voltage and the current information are required for calculating the energy consumption.
[0040] In faulty wiring condition, no neutral connection is available at the incoming and out going point of the meter. A DC current equivalent to 240V AC is generated and fed for measuring the energy consumed during the faulty condition or during the disconnection of the neutral line. During the faulty condition of the energy meter, the 240V AC is assumed for calculating the voltage level, irrespective of the actual line voltage level. The recording of power consumption is continued even in the absence of neutral line.
[0041] The detection system of the present invention provides a visual indication to the user or the power supply distribution company regarding the tampering of the neutral line in the energy meter. A visual indicator such as LED or back-lit LCD is provided in the meter to indicate the disconnection of the neutral line. The LED and Back-lit LCD will be turned on in normal condition. In faulty situation the LED & Back-lit of LCD will be turned off thereby visually indicating the disconnection of neutral line so that the concerned authorities may take suitable action.
[0042] According to another embodiment of the present invention, a method is provided for detecting the disconnection of the neutral line from the energy meter. According to the embodiment, a specially designed transformer such as potential transformer current

transformer (PTCT) is connected to the incoming and outgoing phase and neutral line terminals of the energy meter. In the normal operating condition of the meter, the phase and the neutral current passed through PTCT are equal in magnitude but opposite in sign so that the resultant flux in the core due to the phase and neutral currents passed through the transformer is zero. The PTCT transformer is energised by the unbalanced phase or neutral current that is passed through the transformer during a faulty condition. The PTCT supplies the power required for calculating the actual power consumption during the faulty condition and for recording the power consumption level.
[0043] A LED or back lit LCD is provided to indicate the disconnection of the neutral line in the energy meter visibly. The LED ot the back lit LCD is switched on during the normal operation. The LED or the back lit LCD is switched off during the faulty condition to indicate the disconnection of the neutral line.
[0044] Thus the tampering of the energy meter by disconnecting the neutral lines is detected reliably and the actual consumption is measured even after the disconnection of the neutral line. The disconnection of the neutral line is indicated visually to alert the authorities.
[0045] The FIG. 1 shows the block diagram of the neutral line tamper detection system for energy meter according to one embodiment of the present invention.
[0046] A specially designed transformer such as potential transformer current transformer (PTCT) is connected to energy meter in such a manner that the incoming

and the outgoing phase and the neutral terminals of the energy meter are connected to the PTCT. In the normal operating condition of the meter, the phase and the neutral current passed through PTCT are equal in magnitude but opposite in sign so that the resultant flux in the core due to the phase and neutral currents passed through the transformer is zero. The PTCT transformer is energised by the unbalanced phase or neutral current that is passed through the transformer during a faulty condition. The PTCT supplies the power required for calculating the actual power consumption during the faulty condition and for recording the power consumption level.
[0047] The PTCT is connected to an automatic power supply which is in turn connected to the energy meter through an automatic power switching mechanism. The automatically selected power supply provides power supply to the energy meter during the disconnection of the neutral line to supply a DC power which is equivalent to 240 V AC to the energy meter to measure and record the actual power consumption during the disconnection of the neutral line.
[0048] The auxiliary power supply has an over voltage Hmiter to rectify the power supplied to the energy meter. The energy meter is connected to the mains power supply through the automatic switching mechanism to receive the 240 V AC supply. In normal operating condition, the energy meter receives the power from the mains power supply. The energy meter receives the power from the auxiliary power supply during the disconnection of the neutral line. The automatic switching mechanism is operated to supply power to the energy meter either from the mains during the normal operating condition or from the auxiliary power supply.

[0049] Normally the secondary load impedance should be low for the current transformer and the load impedance should be high for the voltage transformer. In the PTCT, the load is dynamically varied according to the load current. It has voltage and current transformer characteristics. The Current transformer is used as voltage transformer by selecting the core properly. The dimensions of the core and that of the secondary winding are selected accurately to get optimum performance. The special custom made transformer is made up of rolls of silicon steel alloy. The core starts saturating at a primary current of 2A and above. The Load current may vary up to 75A. By operating the PTCT on saturation region, the core is no more magnetically proportionately coupled on PTCT transformer. The coupled power is used for generating DC Voltage.
[0050] A FET based series pass regulated power supply may be used for pre-regulation of the DC power. The DC voltage powers the complete electronic circuit in the meter. Since the neutral is disconnected, no reference voltage is available for measuring the actual power consumption. The Local reference is generated and is supplied in common to all electronics. Actually the voltage and current information are required in the energy meter for calculating the energy consumption value.
[0051] In an intentional faulty wiring condition, no neutral connection is available at the incoming and out going points. A DC voltage equivalent to 240 Volt ac is generated and fed for measuring the power consumption. In the intentional faulty condition, 240Vac is always assumed for calculating the power consumption irrespective of the line voltage.

The recording of the power consumption is continued even in the absence of neutral line.
[0052] The FIG. 2 shows the B-H curve due to the magnetic flux generated due to the passage of phase and neutral current in the energy meter according to one embodiment of the present invention. The curve indicates the operating region of the transformer. The Normal transformer operates in non-saturation region. This PTCT transformer operates in saturation region as shown in FIG. 2.
[0053] Normally the secondary load impedance should be low for the current transformer and the load impedance should be high for the voltage transformer. In the PTCT, the load is dynamically varied according to the load current. It has voltage and current transformer characteristics.
[0054] The Current transformer is used as voltage transformer by selecting the core properly. The dimensions of the core and that of the secondary winding are selected accurately to get optimum performance. The special custom made transformer is made up of rolls of silicon steel alloy. The core starts saturating at a primary current of 2A and above. The Load ciarrent may vary up to 75A. By operating the PTCT on saturation region, the core is not more magnetically coupled on PTCT transformer. The coupled power is used for generating DC Voltage.
[0055] A FET based series pass regulated power supply may be used for pre-regulation of the DC power. The DC voltage powers the complete electronic circuit in the meter.

Since the neutral is disconnected, no reference voltage is available for measuring the actual power consumption. The Local reference is generated and is supplied in common to all electronic circuits in the energy meter. The voltage and current information are required for calculating the power consumption level.
[0056] In an intentional faulty wiring condition, no neutral connection is available at the incoming and out going points. A DC voltage equivalent to 240 Volt AC is generated and fed to the measuring unit to record the power consumption. In the intentional faulty condition, 240 V AC is always assumed for calculating the power consumption irrespective of the line voltage. The recording of the power consumption is continued even in the absence of neutral line.
[0057] The FIG. 3 shows a schematic wiring diagram of the energy meter during normal operating condition according to one embodiment of the present invention. The incoming phase line terminal and the outgoing neutral line terminal are connected respectively to the energy meter. The incoming neutral line terminal and the outgoing phase line terminal are connected respectively to the load such as equipment, etc. The PTCT is coupled to the energy meter in such a manner that the phase current and the neutral current are passed through the core of the PTCT in opposite directions. During the normal operating condition of the energy meter, the magnitude of the phase current and the neutral current are equal in magnitude but opposite in direction so that the resultant flux is zero.

[0058] The FIG.4 shows a schematic wiring diagram of the energy meter during tampered operating condition according to one embodiment of the present invention, in an intentional faulty condition the incoming and the outgoing phase line terminals of the energy meter are connected to the 240 V AC mains supply and to the load. The incoming and the outgoing neutral lines of the energy meter connected respectively to the 240 V AC mains supply and to the load are disconnected so that the neutral of the 240 V AC mains supply is directiy connected to the load bypassing the energy meter. The phase and the neutral current passed through the core of the PTCT during the disconnection of the neutral line in the energy meter do not cancel each other thereby generating an imbalance in the current passed through the core. As a result, the resultant flux is zero due to the phase current and the neutral current through the PTCT is not equal.. Either the phase current passed through the PTCT may be equal to zero or the neutral current passed through the PTCT may be zero.
[0059] The FIG. 5 shows a flow chart explaining the neutral line detection method in energy meter according to one embodiment of the present invention. The meter is started to carry out the regular metering operations to compute the electrical energy consumed by a user. During the regular metering operations, the energisation of PTCT transformer by the imbalance in the phase and the neutral current due to the disconnection of the neutral line in the energy meter is detected. When the disconnection of the incoming and the outgoing neutral line in the energy meter is detected, the consumption of the energy is calculated and recorded by supplying a DC power equivalent to 240 V AC to the metering unit. The energy level is recorded in a memory such as electrically erasable programmable memory like EEPROM.

[0060] When the disconnection of the neutral lines in the energy meter is not detected, the regular metering operations are continued and the results are recorded. On the contrary when the disconnection of the neutral line is detected by the PTCT, the energy calculated by assuming reference voltage of 240V and actual load current, is recorded in the memory such as EEPROM. Once the connection is restored, the energy meter records the energy with present load current and supply voltage.
[0061] The FIG. 6 shows a a schematic wiring diagram of potential transformer current transformer (PTCT) connected to energy meter according to one embodiment of the present invention. A specially designed transformer such as potential transformer current transformer (PTCT) is connected to energy meter in such a manner that the incoming and the outgoing phase and the neutral terminals of the energy meter are connected to the PTCT. In the normal operating condition of the meter, the phase and the neutral current passed through PTCT are equal in magnitude but opposite in sign so that the resultant flux in the core due to the phase and neutral currents passed through the transformer is 2ero. The PTCT transformer is energised by the unbalanced phase or neutral current that is passed through the transformer during a faulty condition. The PTCT supplies the power required for calculating the actual power consumption during the faulty condition and for recording the power consumption level.
[0061] Thus the present invention provides a detection system and method to prevent the tinkering of the energy meter by disconnecting the neutral lines reliably and cheaply. The system measures and records the power consumption even during the disconnection of the neutral lines efficiently and effectively. The system helps to stop

the energy theft. The system provides a visual indication regarding the disconnection of the neutral lines in the energy meter to the user to take suitable corrective operation.
G) ADVANTAGES OF THE INVENTION
[0062] The various embodiments of the present invention provide a system and method to detect the tampering of the energy meter by disconnecting the neutral Une reliably and accurately. The anti tamper system measures the power consumption level accurately even when the energy meter is tampered by disconnecting the neutral line. The system also provides a visual indication to alert the tampering of the neutral line in the energy meter.
[0063] 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.
[0064] 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 device for detecting the disconnection of neutral line in
energy meter, comprising:
Potential Transformer Current Transformer (PTCT) connected to energy meter to detect disconnection of incoming and outgoing neutral line points in said energy meter;
Wherein the core of said PTCT is energised by the unbalanced phase current or neutral current during the disconnection of the neutral line in the energy meter to indicate the disconnection of neutral line.
2. The tamper detection device according to claim 1, wherein the leads of the primary and the secondary windings of the PTCT transformer are respectively connected to the phase and neutral line terminals of the energy meter.
3. The tamper detection device according to claim 1, wherein the neutral current and the phase current are passed through the core of the PTCT in opposite directions so that the flux of the magnetic fields produced due to the passage of neutral and phase currents through the core of the PTCT are in equal in magnitude but opposite in direction to produce zero resultant flux.

4. The tamper detection device according to claim 1, wherein the phase current and the neutral current passed through the core of the PTCT are not equal in magnitude during the disconnection of the neutral line.
5. The tamper detection device according to claim 4, wherein phase current passed through the core of the PTCT may be zero and the core may be energised with the neutral current.
6. The tamper detection device according to claim 4, wherein the neutral current passed through the core of the PTCT may be zero and the core may be energised with the phase current.
7. The tamper detection device according to claim 1, wherein the PTCT is operated in the saturation region.
8. The tamper detection device according to claim 1, wherein the PTCT is made up of rolls of special grade silicon steel alloy.
9. The tamper detection device according to claim 1, the PTCT provides power supply to record the cumulative power level consumed during the disconnection period.

10. The tamper detection device according to claim 1, wherein the PTCT generates
and supplies 240 volt AC equivalent DC to measure power consumption during
the disconnection of the neutral Kne.
11. The tamper detection device according to claim 1, wherein energy meter has metering unit to calculate actual power consumption during the disconnection of the neutral lines by assuming 240 volt AC .
12. The tamper detection device according to claim 1, further comprises LED display so that the LED is always on during the normal operating condition of the energy meter.

13. The tamper detection device according to claim 12, wherein the LED display is switched off during the disconnection of the neutral line to indicate the disconnection condition.
14. A tamper detection method in energy meter for detecting the disconnection of the neutral line, the method comprising:
Connecting a potential transformer current transformer (PTCT) to auxiliary power supply in energy meter to detect disconnection of neutral line; Wherein core of said PTCT is energized due to imbalance in phase and neutral currents passed through disconnection of neutral lines to indicate disconnection of neutral line.

15. The tamper detection method according to claim 14, wherein the PTCT is operated in saturation region.
16. The tamper detection method according to claim 14, wherein the neutral current and the phase current are passed through the core of the PTCT in opposite directions so that the flux of the magnetic fields produced due to the passage of neutral and phase currents through the core of the PTCT are in equal in magnitude but opposite in direction to produce zero resultant flux.
17. The tamper detection method according to claim 14, wherein the phase current and the neutral current passed through the core of the PTCT are not equal in magnitude during the disconnection of the neutral line.
18. The tamper detection method according to claim 14, wherein phase current passed through the core of the PTCT may be zero and the core may be energised with the neutral current.
19. The tamper detection method according to claim 14, wherein the neutral current passed through the core of the PTCT may be zero and the core may be energised with the phase current.
20. The tamper detection method according to claim 14, wherein the PTCT is made up of rolls of special grade silicon steel alloy.

21. The tamper detection method according to claim 14, the power is supplied by
the PTCT to record the cumulative power level consumed during the
disconnection period.
22. The tamper detection method according to claim 14, wherein the 240 volt Ac
equivalent DC is generated and supplied by PTCT to measure power
consumption during the disconnection of the neutral line.
23. The tamper detection method according to claim 14, wherein actual power
consumption is calculated during the disconnection of the neutral lines by always
assuming 240 volt AC. .
24. The tamper detection method according to claim 14, wherein LED display is
provided so that the LED is always switched on during the normal operating
condition of the energy meter.