RU2474825C1 - Device to inspect operation of single-phase induction electric counters - Google Patents

Abstract

FIELD: electricity.SUBSTANCE: device to inspect operation of single-phase induction electric counters comprises a single-phase induction electric counter properly connected to a grid, and its outlet is connected via fuses to a controlled active load. At the same time phase and zero conductors are additionally connected to an accumulating capacitor accordingly via two circuits of parallel-connected power transistor and symistor, transitions "base-emitter" of power transistors are in a transformer manner connected to a high-frequency pulse generator with controlled repetition rate of pulses in the form of a meander, the output of which is also connected to an electronic frequency metre. Control transitions of symistors are connected with appropriate matching amplifiers, a phase conductor is also additionally connected with an inlet of a unit of symistors control, the first outlet of which is connected with the inlet of the matching amplifier of the phase circuit via a separating optron, and the second one - with the inlet of the matching amplifier of the zero circuit directly.EFFECT: provision of the possibility to assess accuracy of proper accounting of consumed energy by induction electric counters as a function of frequency of current interruptions in a load, and also selection of optimal value of a frequency of charging current interruptions in an accumulating capacitor, at which induction electric counters are most exposed to uncontrolled accounting of power.2 cl, 7 dwg

Description

The invention relates to measuring equipment and can be used in the development and study of single-phase induction electric meters, in particular, on sensitivity to high-frequency current components in loads.

In industrial production, at various private enterprises and in everyday life, induction single-phase and three-phase electric meters are widely used as electricity metering devices (СО-2М, СО-И646М and others).

It is known that the sensitivity and accuracy of their operation at the used industrial frequency of 50 Hz is quite high, however, these characteristics are significantly reduced if the load in the power grid fluctuates with an increased frequency (units and tens of kilohertz). This leads to the need to study the dependence of the correct metering of consumed electricity on the frequency of interruptions of electric current in loads. Until recently, this problem has not been given enough attention from the developers of induction energy metering devices, which allows for the theft of electricity, the scale of which has become menacing, and the fight against this often boils down to an increase in electricity tariffs to cover unaccounted for electricity, that is, to neutralize commercial losses in the hundreds of billions of rubles annually.

Methods of combating theft of electricity are diverse. The author of this application has proposed effective ways to reduce commercial losses associated with the theft of electricity by switching the phase and neutral conductors at the point of connection of the inputs with branches (jumps) from overhead lines of 0.4 kV overhead lines. In particular, a method for sealing phase or neutral conductors with corresponding branch conductors from OHL-0.4 kV was proposed [1, 2]. This allows, according to estimated estimates, to save several tens of billions of rubles annually at minimal and one-time costs by teams of energy supplying organizations in the order of current operation.

Attempts have been made to eliminate commercial losses by using induction metering devices with two current windings in electric meters (for example, in single-phase devices of the CE-200 type) located in phase and zero circuits, which, according to the developers of such devices, excludes theft of electricity by means of the aforementioned phase and zero conductors at the inputs. However, using the schemes developed by the author for checking the sensitivity of electric meters with two current windings, it is possible to carry out the theft of electricity using hidden grounding [3, 4].

There are known “exotic” methods of theft of electricity using special circuits that are neither related to transfer of phase and zero conductors at the inputs, nor using a hidden grounding device, nor are consumers rarely used to directly direct branch conductors from 0.4 kV OHL or on the conductors of the power line itself (for example, during electric welding). Such electronic circuits use high-frequency interruption of the current of the network charging the capacitive storage for the first and third quarters of the period, and the subsequent exponentially non-interruption discharge of the capacitive storage back to the network through the metering device in the second and fourth quarters of the period, the disk of which rotates in the opposite direction, or it remains stationary if the meter is equipped with a ratchet mechanism that excludes the counter disk’s reverse stroke, although a certain power is consumed by the load s. The value of electricity not taken into account in this case is determined by the capacitive storage parameters and the frequency of current interruptions in the first third quarters of the mains voltage period. The latter circumstance is the object of study in the claimed technical solution.

The aim of the invention is to assess the accuracy of the correct metering of consumed electricity by induction electric meters as a function of the frequency of current interruptions in the load.

This goal is achieved in a device for checking the operation of single-phase induction electric meters, containing a correctly connected single-phase induction electric meter, the output of which is connected via fuses to an adjustable active load, characterized in that the phase and neutral conductors are additionally connected to the storage capacitor, respectively, through two circuits connected in parallel power transistor and triac, base-emitter transitions of power transistors transformer conn They are connected to a high-frequency pulse generator with an adjustable pulse repetition rate in the form of a meander, the output of which is also connected to an electronic frequency meter, the control transistors of the triacs are connected to the corresponding matching amplifiers, the phase conductor is also additionally connected to the input of the triac control unit, the first output of which is connected to the input of the matching amplifier phase circuit through a separating optocoupler, and the second with the input of the matching amplifier of the zero circuit directly.

The device is characterized in that the triac control unit includes phase-shifting RC circuits, first and second comparators, first and second inverters and first and second coincidence circuits, a phase conductor is connected to the input of the first comparator and the beginning of phase-shifting RC circuits, the end of which is connected to the input of the second comparator, the inputs of the first match circuit are connected to the output of the first comparator and to the output of the second inverter, the input of which is connected to the output of the second comparator, the inputs of the second match circuit are connected to the outputs of the second computer Ator and the output of the first inverter having an input connected to the output of the first comparator, wherein the RC-circuit phase shifters shift is performed on the mains voltage phase π / 2, and the inverting outputs of the first and second coincidence circuits respectively form first and second outputs of the control unit triacs.

Achieving this goal is explained by the inequality of the energy taken into account by a single-phase inductive electric meter when charging the storage capacitor with a discontinuous current in the first quarter of the positive half-cycle, as well as in the third quarter of the negative half-cycle of the mains voltage, and the smooth discharge energy of this storage capacitor during the second and fourth quarters of the period, respectively, at which according to the readings of the electric meter, it seems that the AC source is not power network, and the inventive device connected to it. The indicated difference in these energies is proportional to the capacitance of the storage capacitor used and is the investigated function of the frequency of interruptions of the charging current in the storage capacitor.

The inventive device is illustrated by its diagram and graphs.

Figure 1 shows a diagram of the claimed technical solution, consisting of:

1 - investigated single-phase induction electric meter,

2 - input, the phase conductor of which is connected to terminal No. 1 of the meter, and zero - to terminal No. 3 when counting the terminals from left to right,

3 - overhead power transmission line VL-0.4 kV, to which input 2 is connected,

4 - fuses in the phase and zero circuits from the outputs of the meter (respectively, with its terminals No. 2 and No. 4),

5 - adjustable active load R _H (the current in the load and the voltage on it are measured respectively by an ammeter and an alternating current voltmeter),

6 - the first power transistor of the phase circuit (T ₁ ),

7 - the first triac phase circuit (D ₁ ),

8 - storage capacitor (C _H ),

9 - the second power transistor of the zero circuit (T ₂ ),

10 - the second triac of the zero circuit (D ₂ ),

11 - the first matching amplifier phase circuit (SU-1),

12 - second matching amplifier zero circuit (SU-2),

13 - high-frequency pulse transformer with separate secondary windings for the separation of phase and zero control circuits,

14 - high-frequency pulse generator with an adjustable pulse repetition rate in the form of a meander (that is, with a duty cycle equal to two),

15 - electronic frequency meter,

16 - control unit triacs,

17 - separation optocoupler.

Figure 2 shows a block diagram of a triac control unit, including the following elements and blocks:

18 is the first comparator,

19 is a second comparator,

C ₁ and C ₂ are phase-shifting capacitors,

R ₁ , R ₂ - active resistance phase-shifting circuits (R ₁ - adjustable resistance to fine-tune phase shift),

20 is a first coincidence scheme of type 2I-He,

21 is a second coincidence scheme of type 2I-He,

22 - the first inverter (circuit He),

23 - second inverter (circuit He).

Figure 3 shows the timing diagrams of the control unit triac D ₁ and D ₂ . The first and second graphs show the pulsed signals U ₁ and U ₂ generated at the outputs of the first and second comparators. The third and fourth graphs show the generated control signals acting on the first and second outputs of the triac control unit.

Figure 4 shows one complete period of the mains voltage U _≈ (t) with period T. Figure 5 shows a continuous sequence of pulse voltages U _Г (t) generated by a high-frequency pulse generator with an adjustable pulse repetition rate in the form of a meander and used to control the operation of the first and second power transistors 6 and 9 (Fig. 1) in the key mode.

Figure 6 shows a graph of the voltage across the storage capacitor 8 (C _H ) in charge and discharge modes. Dashed lines denote discontinuous charge-recharge cycles in the first and third quarters of the mains voltage period, respectively, and smooth curves indicate the cycles of a continuous continuous discharge of the storage capacitor in the second and fourth quarters of the period, respectively.

Fig. 7 shows the form of the function _{ΔР СP} (f) / P _H studied using this device for some constant value of the load resistance 5 (R _H ), the value of which can be adjusted, as a function of the frequency f of the pulse generator 14, measured by the electronic frequency meter fifteen.

Consider the work of the proposed scheme (Fig. 1).

, где U_O - действующее напряжение сети, t - время включения реактивной нагрузки. При этом однофазный индукционный счетчик активной энергии учет электроэнергии не производит (его счетный механизм неподвижен).It is known that the direct connection of a storage capacitor 8, which is an almost ideal reactive element, into the AC mains supply, leads to current circulation in the network with a double frequency of 2 F, where F is the frequency of the network. In this case, only reactive energy is consumed.

where U _O is the operating voltage of the network, t is the reactive load on time. At the same time, a single-phase induction active energy meter does not produce electricity metering (its counter mechanism is stationary).

, что дополнительно контролируется по показаниям встроенных в схему амперметра и вольтметра и с использованием хронометра (часов).When directly connected to the network of the active resistance of the load 5 (R _H ), such an electric meter will record with a sufficient degree of accuracy the energy spent in the active load, equal to

, which is additionally controlled by the readings of the ammeter and voltmeter built into the circuit and using the chronometer (hours).

It is known that induction meters have a significant drawback in accounting for electricity if the current flowing in the load is interrupted with a sufficiently high frequency f >> F. Moreover, with an increase in the frequency of current interruptions, the readings of the meter against the actually consumed energy are significantly underestimated. Therefore, the problem arises of evaluating the operation of induction electric meters (electricity meters) as a function of the frequency f of current interruptions in the load.

The indicated drawback of induction electricity metering devices is used by unscrupulous users for the purpose of uncontrolled theft of electricity by charging the storage capacitor 8 (Fig. 1) with an intermittent current in the first and third quarters of the mains voltage periods (Fig. 4) and its discharge with a continuously changing voltage (without current interruptions) respectively, in the second and fourth quarters of the periods. Moreover, in the first and third quarters of the periods the metering device underestimates the metering of consumed electricity, and in the second and fourth quarters of the periods when the storage capacitor 8 transfers the energy it consumed back to the network, the metering device works normally with its certified accuracy. If the metering devices of the old type (such as СО-2М, СО-И646М and others) have a disk structure without a backstop, then in such a scheme the disk of the metering device will rotate in the opposite direction, giving the impression that it is not the mains electricity supplier, but the device itself. In other words, readings on previously consumed electricity will decrease in such meters. If the meters have disk reverse stops (such as ratchet wheels), then the readings of the meter when the active load is actually switched on will either be clearly underestimated, or the counter can even be stopped if the actively consumed power is less than or equal to the difference average power ΔР _CP = U _O I - P _UCH , where P _UCH - the power taken into account by the electric meter, underestimated by the use of the circuit in question, I and U _O - current and current voltage according to the readings of the instruments (ammeter and voltmeter).

The degree of underestimation of the readings in such electric meters will substantially depend on the frequency f of current interruptions when the storage capacitor 8 is charged (Fig. 1), which is the subject of research using the inventive device. This is necessary when developing new induction electricity meters.

The interruption of the charging current in the storage capacitor is carried out using power transistors 6 and 9 (T ₁ and T ₂ ) operating in the key mode, at the base-emitter junctions of which high-frequency pulse signals are supplied from the output of the high-frequency pulse generator 14 with an adjustable frequency f through high-frequency pulse transformer 13 with two separate (isolated from each other) secondary windings. Parallel to these power transistors, triacs 7 and 10 (D ₁ and D ₂ ) are turned on, which, according to the outputs from the control unit of the triacs 16, are either fully open (Open) or completely closed (Close) (that is, they also work in key mode but at a frequency of 2 F << f). The operating procedure of the triacs is visible from the table below.

Table Time interval Triac D ₁ Triac D ₂ t = 0 ... T / 4 Close Revelation t = T / 4 ... T / 2 Revelation Revelation t = T / 2 ... 3T / 4 Revelation Close t = 3T / 4 ... T Revelation Revelation

Note that when the triacs 7 or 10 are open, the power transistors 6 or 9 connected in parallel with them do not have any effect on the resistance of the corresponding circuit (phase or zero), that is, they do not interrupt the current. On the contrary, when the triac is locked, the corresponding power transistor performs the function of interrupting current.

So, in the first quarter of the period (with a positive half-wave) the triac D _{1 is} closed, and the triac D _{2 is} open. Therefore, the storage capacitor 8 is charged with intermittent current, and the meter lowers its readings. In the second quarter of the period, the storage capacitor C _H returns the charge accumulated in it back to the network with open triacs D ₁ and D ₂ , that is, without current interruptions, and the meter takes back records of the energy supplied, underestimating the total readings of the meter. In the third quarter of the period (with a negative half-wave), the triac D _{1 is} closed, and the triac D _{2 is} open, and the storage capacitor is recharged (with the opposite polarity sign) with an intermittent current using a power transistor T ₂ , and in the fourth quarter it is discharged back to the network when open triac D ₁ and D ₂ , as follows from the above table and from Fig. 6.

The use of parallel switching of the triacs and the corresponding power transistors allows us to simplify the circuit of the triac control unit while continuously supplying control pulse signals to the base-emitter junctions of the power transistors.

Briefly consider the work of the flowchart shown in Fig. 2.

To obtain triac control signals according to the table above, it is necessary to form a sinusoidal signal of the frequency F of the network, phase shifted by π / 2. This is achieved using two phase-shifting RC circuits (R ₁ C ₁ and R ₂ C ₂ ) connected to the phase conductor through an isolation capacitor (not shown in the diagram) in series. Each of these chains carries out a phase shift by π / 4, and the fine tuning is carried out using a variable resistor R ₁ . Two sinusoidal voltages are then supplied to the first 18 and second 19 comparators - limiters, the shape of the output signals of which are shown in Fig. 3 - with the letters U ₁ and U _2, respectively. Based on the algebra of logic, it is easy to understand how, using the matching circuits 20 and 21 (type 2I-He) and inverters 22 and 23 (type He), the necessary control signals are generated at the first and second outputs of the triac control unit, shown in Fig. 3 with letters U ₃ and U _4, respectively.

Since the phase conductor has a high potential with respect to the zero, the first output of the triac control unit is connected to the first matching amplifier 11 (SU-1) through an optocoupler 17, and the second output of the block is connected directly to the second matching amplifier 12 (SU-2).

By adjusting the frequency f of the high-frequency pulse generator in the range f = 2 ... 30 kHz, the frequency of interruptions of the charging current in the storage capacitor 8 (C _H ) is changed and, for a given active load 5 (R _H ), the consumed electricity is taken into account according to the readings of the ammeter and voltmeter for some time ΔT _MF, and then compare these results with the readings of the induction electric meter, determining the difference average power ΔP _CP (f) as a function of the frequency of interruptions of the charging current. As practice has shown, the discrepancy between the energy values during and without current interruption can reach a ratio of 1: 4. This means that using the inventive device, on metering devices of the type СО-2М, СО-И646М and others, it is possible to either slow down the rotation of the disk, or stop it when the active load is on, or reverse the rotation of the disk (unwinding of indications) depending on the applied storage capacity capacitor C _AND when selecting the frequency of interruptions f of the charging current.

Легко понять, что при выборе сопротивления активной нагрузки R_H счетчик будет остановлен, если емкость накопительного конденсатора 8 выбрать из условия

, откуда получим: С_H=1/1,5R_HF=0,67/R_HF. Так, при неучитываемом потреблении электроэнергии мощностью P_H=2 кВт (диск счетчика не вращается) при действующем напряжении сети U_O=220 В и частоте сети F=50 Гц, сопротивление активной нагрузки равно

и емкость накопительного конденсатора должна быть выбрана равной С_H≈0,67/R_HF=0,67*/24,2*50=0,000554 Ф=554 мкФ.In the optimal case, that is, with the correct selection of the frequency of interruptions f * of the charging current in the storage capacitor C _N , the unaccounted power when connecting an active load can be

It is easy to understand that when choosing the resistance of the active load R _{H the} counter will be stopped if the capacity of the storage capacitor 8 is selected from the condition

, whence we get: С _H = 1 / 1,5R _H F = 0,67 / R _H F. So, with unaccounted for power consumption with a power of P _H = 2 kW (the meter’s disk does not rotate) with the mains voltage U _O = 220 V and network frequency F = 50 Hz, the resistance of the active load is

and the capacitance of the storage capacitor should be chosen equal to C _H ≈0.67 / R _H F = 0.67 * / 24.2 * 50 = 0.000554 F = 554 μF.

Note that the storage capacitor 5 must be able to operate on alternating current of increased frequency and have an operating voltage of about 400 V. Power transistors and triacs should be calculated for these reverse voltages.

With the current state of consumer (household) power grids, more than half of the country is equipped with single-phase induction meters for electricity metering, so the risk of theft of electricity is very high, expressed in enormous commercial losses. Therefore, the task is to assess the situation and develop new, more advanced metering devices that are less sensitive or completely insensitive to interruption of the charging current in capacitor circuits to reduce the readings of electricity meters during the theft of electricity.

The sensitivity of electricity metering devices is checked by installing a storage capacitor 8 with a capacity of, for example, 100 μF and selecting an active load 5 (powerful rheostat) until the disk completely stops in the induction meter and adjusts the frequency f in the high-frequency pulse generator 14, measured by the electronic frequency counter 15, at which the resistance of the resistor 5 cannot already be reduced if the disk of the meter remains stationary. Based on experimental data, a graph is constructed, an approximate view of which is given in Fig. 7.

In this case, the frequency range of interruptions of the charging current in the storage capacitor is determined, within which the meter is most vulnerable from the point of view of the possibility of theft of electricity.

Commercial losses of electricity associated with theft are so widespread that there is a need to develop effective measures to protect electricity meters from uncontrolled and unaccounted for its consumption. Measures to raise electricity tariffs cannot be deemed sufficient, but can only lead to excessive and dangerous social tension.

Literature

1. Smaller OF, Method of combating theft of electricity. RF patent No. 2208795, publ. in no.20 of 07.20.2003.

2. Smaller OF, the Method of combating theft of electricity (Method of Smaller), RF Patent No. 2308726, publ. No. 29 dated 10/20/2007.

3. Smaller OF, Device for checking the sensitivity of an electronic meter with two current circuits with active load and reactive compensation, Patent No. 2338217, publ. No. 31 dated November 10, 2008.

4. Smaller OF, Method for verifying the operability of an electronic electricity meter with two current measuring circuits and a scheme for its implementation, Patent No. 2344428, publ. No. 02 dated January 20, 2009.

Patent Search Data

DE 4235722 A, 04/14/1994

EP 0100694 A, 02.15.1984

Claims (2)

1. A device for checking the operation of single-phase induction electric meters, containing a correctly connected single-phase induction electric meter, the output of which is connected via fuses to an adjustable active load, characterized in that the phase and neutral conductors are additionally connected to the storage capacitor, respectively, through two circuits of parallel connected power transistor and triac, base-emitter junctions of power transistors are transformer connected to high-frequency an oscillator with an adjustable pulse repetition frequency in the form of a meander, the output of which is also connected to an electronic frequency meter, the control transitions of the triacs are connected to the corresponding matching amplifiers, the phase conductor is also additionally connected to the input of the control unit of the triacs, the first output of which is connected to the input of the matching amplifier of the phase circuit through a separating optocoupler, and the second with the input of the matching amplifier of the zero circuit directly. 2. The device according to claim 1, characterized in that the triac control unit includes phase-shifting RC circuits, first and second comparators, first and second inverters and first and second coincidence circuits, a phase conductor connected to the input of the first comparator and the beginning of phase-shifting RC circuits , the end of which is connected to the input of the second comparator, the inputs of the first match circuit are connected to the output of the first comparator and to the output of the second inverter, the input of which is connected to the output of the second comparator, the inputs of the second match circuit are connected to the outputs of the second the first comparator and the output of the first inverter, the input of which is connected to the output of the first comparator, the phase-shifting RC circuits shifting the phase of the mains voltage by π / 2, and the inverting outputs of the first and second coincidence circuits form the first and second outputs of the triac control unit, respectively.

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