RU2522706C1 - Bridge calibration device for induction-type electric meters of active energy - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: calibration device for induction-type electric meters of active energy includes transistors switching capacitor discharge current and controlled by modulated HF pulse generator. The device features bridge design, with first and second branches connected in parallel to electric network and switching a series of capacitor and bidirectional transistor switch out of two similar transistors connected in parallel opposition. The first branch of bridge circuit is connected to phase conductor of network by bidirectional transistor switch, the second branch is connected by capacitor, and diagonal of the bridge circuit includes controlled symistor (bidirectional thyristor), four transistors and symistor are controlled by control unit synchronised by network voltage.

EFFECT: enhanced precision of calibration.

20 dwg

Description

The invention relates to the field of electrical engineering and can be used in testing single-phase induction electric meters, in particular, when checking the accuracy of the calculation of the consumed electricity when the operating current is interrupted at an increased frequency that is many times higher than the frequency of the power supply network.

It is known that the sensitivity and accuracy of such metering devices 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 the theft of electricity, the scale of which has become threatening, and the fight against this is practically reduced 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.

It is known that a pure capacitive load (lossless capacitor) connected to an AC network does not take into account the active energy meter circulating in it with double frequency of the network. However, if in the first and third quarters of the period such a capacitive load is interrupted at a sufficiently high frequency (several kilohertz) during the charge of the capacitor, and in the second and fourth quarters of the period, these interruptions are stopped, providing a smooth discharge of the energy stored in the capacitor back to the network, then such induction-type electric meters with rotating disks (type СО-2М, СО-И646М and others) will decrease their current readings when the rotating disk is reversed, and digital meters (type CE-200 and the like) with induction nozhitelyami DC voltage will not take into account the energy connected in parallel to an active network load, if this energy is no longer the one that determines the reduction of the testimony in the induction electric meters with rotating disks.

The author has proposed effective ways to combat the theft of electricity by the so-called transfer of phase and zero conductors at the input to

branching from the overhead line VL-0.4 kV [1-2] when using a hidden grounding device, the introduction of which throughout the country as a whole is able to replenish the state treasury up to 50 billion rubles a year with minimal one-time expenses for sealing the specified input connection.

However, more sophisticated schemes of electricity theft based on autonomously operating compact devices that can be connected directly to a power outlet with a properly connected and sealed meter and without using a grounding device can be used [3-5], and the use of such devices by unscrupulous citizens or organizations can cause significant damage the economy of the country, which forces the companies developing electricity meters to check their products for insensitivity to connection eniyu of such devices to reduce the readings of electricity meters for active energy.

With the improvement of active electricity meters, the known countermeasures for correct metering of consumed electricity become less effective for verification of the developed electricity meters, which is related to the disadvantages of such verified devices.

These disadvantages are eliminated in the claimed technical solution.

The aim of the invention is to increase the energy efficiency of counteraction devices to the correct metering of electricity by induction electric meters in active loads to increase the accuracy of calibration.

This goal is achieved in a bridge device for checking electric meters of active energy of an induction type, containing transistors switching the charge current of the capacitors, controlled from a modulated high-frequency pulse generator, characterized in that it is made according to a bridge circuit, the first and second branches of which, connected in parallel to the mains, include a series-mounted capacitor and a bi-directional transistor switch of two of the same type of parallel-counter-connected transistors, p When in use, the first branch of the bridge circuit is connected to the network phase conductor bidirectional transistor switch, and the second branch - a condenser, and a diagonal of the bridge circuit including control triac (bidirectional thyristor), the control operation of four transistors and triac effected by the control unit, synchronized by the mains voltage.

The device includes a transistor control unit and a triac, which generates packets of high-frequency pulses for controlling the interruption of the charge current (overcharge) of the capacitors in the first and third quarters of the mains voltage period when the triac is closed and the transistors are closed in the second and fourth parts of the mains voltage period while opening the triac.

The achievement of the goal of the invention is explained by a significant increase in voltage (almost doubling the amplitude of the alternating voltage of the network) with a continuous discharge of capacitors back to the network in the second and fourth parts of the period of the mains voltage, which significantly increases the intensity of the reverse of the rotating disk of induction electric meters, or the stop of the digital electric meter with an increased active load, additionally connected to the network, because at these intervals the capacitors of both branches bridge circuits are connected in series to the network conductors. This increases the sensitivity when checking the developed electricity metering devices to counteract the correct metering of active electricity from the side of the claimed device.

The inventive device practically does not create during its operation overvoltages in the network for normal operation of all devices connected to the network for various purposes, since the voltage is almost double in amplitude, removed from the series

the connected capacitors of both branches of the bridge circuit (with the triac open) is partially compensated by the mains voltage opposite to it, which leads only to a certain distortion of the current and voltage shapes in the second and fourth parts of the mains voltage period, which differs from the sinusoidal, but without increasing the amplitude. The latter ensures the safety of electricity consumers connected to the network.

The inventive device is shown in Fig. 1, and its operation is illustrated by the following figures and time diagrams and diagrams.

Figure 1 shows a bridge circuit that includes the following components:

1 - charge transistor of the first branch of the bridge circuit,

2 - transistor recharging the first branch of the bridge circuit,

3 - storage capacitor of the first branch of the bridge circuit,

4 - charge transistor of the second branch of the bridge circuit,

5 - transistor recharging the second branch of the bridge circuit,

6 - storage capacitor of the second branch of the bridge circuit.

7 - triac,

8 - control unit transistors and triac (the operation of this unit is synchronized

mains voltage).

Fig. 2 shows a block diagram of a control unit 8, consisting of:

9 - the first adjustable voltage divider,

10 - the first comparator,

11 - the first phase-shifting RC-value connected to the phase conductor of the network,

12 - second adjustable phase-shifting RC circuit,

13 - second adjustable voltage divider,

14 - second comparator,

15 - the first inverter (circuit "NOT"),

16 - second inverter (circuit "NOT"),

17 - the first coincidence scheme (scheme "I"),

18 - the second coincidence scheme (scheme "And").

19 - the first modulator (circuit "And"),

20 - the first pulse power amplifier,

21 - the second modulator (circuit "And"),

22 - second pulse power amplifier,

23 - four output pulse transformers connected in pairs in series,

24 - four identical grids from a parallel connected resistor and electrolytic capacitor to obtain a negative bias at the bases of transistors 1, 2, 4 and 5 (Fig. 1) due to the base currents,

25 - frequency-controlled generator of high-frequency oscillations,

26 - amplifier-limiter, forming pulses of the type "meander",

27 - the first differentiating circuit,

28 - the second differentiating circuit,

29 - adder-shaper triggering triac impulses (circuit "OR" with one

vibrator)

30 - third pulse power amplifier,

31 - third pulse transformer start triac,

32 - secondary power source of the elements of the control unit (VIP).

In fig. 3 (a-p) the timing diagrams of signals at various points of the circuit are presented in detail:

3A - the initial alternating voltage at the input of the first comparator 10,

3b - alternating voltage, phase shifted by π / 2, at the input of the second comparator 14,

3B - voltage at the output of the first comparator 10,

3G - voltage at the output of the second comparator 14,

3d - the voltage at the output of the first inverter 15,

3e - voltage at the output of the second inverter 16,

3zh - voltage at the output of the first coincidence circuit 17.

3z - voltage at the output of the second coincidence circuit 18,

3i - the voltage at the output of the amplifier-limiter 26,

3k - voltage at the output of the first pulse power amplifier 20,

3L - voltage at the output of the second pulse power amplifier 22,

3m - voltage at the output of the first differentiating circuit 27,

3n - voltage at the output of the second differentiating circuit 28,

3o - the voltage at the output of the third pulse power amplifier,

3p - voltage at the base-emitter junctions of transistors 1 and 4,

3p - voltage at the base-emitter junctions of transistors 2 and 5,

Figure 4a shows a diagram of the processes of charge (recharge) and discharge of capacitors 3 and 6 during the period of the mains voltage, and Fig. 46 shows a diagram of the current in the phase conductor of the network (indicated as "a"), from which it is seen that the reverse current in the electric meter, reducing its readings when connected to an active load or without it (the disk just rotates in the opposite direction) is significantly more than the reverse current in the case of discharge of only one capacitor, as in the known devices [5], which increases the energy efficiency of the offer the desired circuit.

Consider the action of the claimed device.

At the beginning of the first quarter of the period (Fig. 3a), the mains voltage 7 is closed, and a packet of pulses from the output of the first pulse power amplifier 20 with a packet duration corresponding to a quarter of the period, that is 5, is supplied to the base-emitter control transitions of transistors 1 and 4 ms, and with the repetition rate of these pulses in a packet determined by the operation of a frequency-controlled generator of high-frequency oscillations 25, for example, in the form of a “meander”. With these pulses, the indicated transistors open, which creates an intermittent charge of the capacitors 3 and 6, respectively, each of which has time to charge up to the amplitude value of the mains voltage (about 300 V at a network voltage of 220 V 50 Hz) during the action of the package.

At the beginning of the second quarter of the mains voltage period, all transistors of the circuit turn out to be closed, a negative bias voltage acts between their bases and emitters due to grids 24 supporting this bias due to the charge of their capacitors by the currents of the transistor bases in the first quarter of the period (and then in the third quarter of the period ) The grid time constant should be comparable to a quarter of a period, i.e., about 5 ms, which allows us to calculate the capacitance of electrolytic (polar) grid capacitors at a given value of grid resistance, designed to limit the base current in transistors. Simultaneously with the closure of all transistors with a small delay (of the order of 0.1-0.3 ms), the triac 7 opens under the action of a triggering pulse from the output of the third pulse power amplifier 30, which is formed in block 8. In this case, both charged capacitors 3 and 6 turn on in series , the voltage at the ends "a" and "and" is equal to almost double the value of the amplitude of the mains voltage (about 600 V) with a polarity opposite to the polarity of the mains voltage (equal to about 310 V at the beginning of the second quarter of the period). This causes the flow of a significant reverse current through the current winding of the metering meter of electricity and thereby reduces its readings.

At the beginning of the third quarter of the mains voltage period, the triac turns out to be closed as a result of the discharge of capacitors 3 and 6, and at the base-emitter junction of transistors 2 and 5, a packet of positive pulses from the output of the second pulse power amplifier 22 operates. and 6 by the end of the third quarter of the period to a voltage of about 300 V, but with the opposite polarity. At the end of the third quarter of the period, all transistors turn out to be closed (by the action of negative bias), and the triac 7 with a short delay (of the order of 0.1-0.3 ms) opens, again turning on the series-connected capacitors 3 and 6, which are discharged into the network. At the same time, current flows in the opposite direction through the current winding of the electric meter, that is, the “unwinding” of the readings is again supported.

Subsequently, the entire described process is periodically repeated.

The control unit of 8 transistors and a triac in its ideology of operation is similar to the well-known control unit [5], therefore, its operation does not require special explanations and it is clear from the attached figures Fig. 3 and Fig. 4 together with its structure shown in Fig. 2.

When the charge current (recharge) of capacitors 3 and 6 is interrupted, the meter lowers its readings due to the high frequency factor of current interruptions, and when the series capacitors are smoothly discharged, the energy countdown increases significantly, including due to an almost doubled discharge voltage .

Evaluation calculations show that in induction meters, the active energy metering when the inventive device is turned on occurs in magnitude that does not exceed about 15% of the total energy consumed in the active load, which creates huge economic losses for the electricity supplier.

The energy of the claimed device is determined by the capacitance values of capacitors 3 and 6 with an appropriate choice of transistor and triac types according to the allowable values of currents and operating voltages, as well as power dissipated by these elements, requiring the use of cooling means (radiators). So, when you get the power taken into account in the used active load P = 2 kW, you can calculate the required value of capacities 3 and 6 according to the formula:

, $$P=1.7C{U}_o^{2}F,\mathrm{about}t\mathrm{to}\mathrm{at}d\mathrm{but}C=P/1.7U_o^{2}F$$

,

where U _o = 1.41 × 220 V = 310 V is the amplitude value of the mains voltage, F = 50 Hz is the frequency of the mains voltage. Then we have C = 2000 / (1.7 × 96 100 × 50) = 0.000245 F = 245 μF. It is necessary to choose capacitors 3 and 6 of 250 μF each, which allow a pulsed mode at a frequency of up to 10 kHz (for example, type K-75) with an operating voltage of about 600 V.

In this case, n-p-n transistors, for example, type KT 839 A, which allow pulsed currents up to 15 A with a reverse voltage of 1500 V, can be used as transistors. As a triac 7, TS-212-16 can be used.

When creating powerful devices operating at capacities of several tens of kilowatts in three-phase 380 V networks, transistors of the type TKD265-100-6-1, manufactured by Promtekhnologiya LLC (Voronezh), can be recommended as transistors, and use a small-sized transistor Triac TS242-80 is not lower than 10th grade. So, at P = 20 kW and U _o = 380 V in three-phase switching (with three operating devices) we have for the capacitance C the expression: C = 20,000 / (3 × 1.7 × 380 ² × 50) = 0.000543 Ф = 543 uF. Moreover, the device uses six capacitors with a capacity of 550 μF each for an operating voltage of at least 1000 V, three triacs and 12 transistors of the above types with control units separately for each phase pair of a three-phase network. Such a device can be used to check induction active energy meters (type ЦЭ6803 В, Г1СЧ-4А.05.2, etc.) equipped with current transformers.

By adjusting the frequency of interruptions of the charging (recharging) current in the generator 25, it is possible to establish the optimal mode of operation of the device at which the value of P turns out to be maximum for the selected parameters of the circuit elements (in particular, capacitors 3 and 6). This is included in the task of checking electric meters for their sensitivity to the frequency of current interruptions in the load.

We briefly consider the structure and recommendations for choosing the elements of a control unit of 8 transistors and a triac (Fig. 2).

Secondary power supply 32 includes rectifiers with filters for +5 V output voltages for powering transistor-transistor logic (TTL) of the K155 series, two bipolar sources for supplying integrated comparators 10 and 14 (for example, K521CA2) and power amplifiers 20, 22 and 30 with a voltage of +27 V.

Instead of four transformers 23 on a ferrite toroidal core, two transformers with two separate secondary windings in each can be used. Ferrite of the M2000HM-1 brand.

The first phase-shifting RC chain 11 carries out a phase shift of 45 °, the second 12 regulates the phase shift in the range of 40-50 °.

Adjustable voltage dividers 9 and 13 create at the input of the comparators 10 and 14 the voltage amplitudes required for their operation (not more than 5 V).

Modulators 19 and 21 can be performed on the basis of the TTL coincidence scheme, as well as elements 17 and 18 with the logic “2I” (K 155LI 1). Inverters 15 and 16 are executed on the logic "NOT" (K155LN1). The adder-shaper of triggering triac impulses 29 can be performed using the “2OR” logic (K155LL1) with the possible use of a single vibrator on TTL logic (K155AG1) to obtain triggering pulses that open the triac at the beginning of the second and fourth quarters of the mains voltage period of a certain duration (for example 0.5 ms).

The frequency-controlled oscillator 25 can be created using the “2I-NOT” logic with a pair of elements and resistive-capacitive couplings (K 155 L A3), and frequency adjustment in the range of 1 ... 5 kHz is carried out by a variable resistor. Moreover, as a limiter amplifier 26, a comparator (K521CA2) can be used, as in elements 10 and 14.

The operation of control unit 8 is fully explained by the time diagrams of voltages at various points of the circuit in Fig. 3 and diagrams in Fig. 4. In particular, it is important to indicate the need for accurate adjustment of the phase shift by 90 ° of the initial mains voltage with phase-shifting chains 11 and 12 in order to obtain the required pulse interruption (recharge) pulse packets of capacitors 3 and 6 in the first and third quarters of the mains voltage period. The accurate operation of the circuit requires that the triac 7 open only after all transistors 1, 2, 4, and 5 are completely closed, so that the charge of these capacitors does not drain through the open transistors, which can cause the latter to fail if the discharge current is unacceptably high . For this, there is a slight delay in the supply of triggers of the triac relative to the gates arising at the outputs of the differentiating circuits 27 and 28 and corresponding to the phases 90 ° and 270 ° in each period of the mains voltage, at which the pulse packets acting on the corresponding transistors cease, and the latter are closed negative bias occurring in grids 24.

The use of a heavy-duty system immediately after a three-phase induction-type active energy meter in a transformer substation (TP) supplying a plant, city, village, etc., leads to an underestimation of the readings of electricity supplied to consumers from such a substation, which should be taken into account by energy supplying organizations when calculating with by consumer. The possibility of uncontrolled use of such devices by the consumer determines the need to develop a new type of energy metering devices that are not sensitive to interruptions in the load current. Such metering devices should supplant the existing in the country fleet of metering devices for electricity, allowing its gigantic theft.

Literature

1. Smaller O.F. A way to combat theft of electricity. RF patent No. 2208795, publ. in No. 20 of 07.20.2003.

2. Smaller O.F. A way to combat the theft of electricity (Lesser Method). RF patent No. 2308726, publ. No 29 on 10.20.2007.

3. Smaller O.F. A device for checking the sensitivity of an electronic meter with two current circuits with active load and reactive compensation. Patent No. 2,338,217, publ. No. 31 dated November 10, 2008.

4. Smaller O.F. A method of verifying the operability of an electronic electricity meter with two current measuring circuits and a diagram of its implementation. Patent No. 2344428, publ. No. 02 dated January 20, 2009.

5. Smaller O.F. Device for checking electric meters of active energy. RF patent No. 2456623, publ. No. 20 dated July 20, 2012.

Patent Search Data

RU 2338217 C1, 11/10/2008

RU 2190859 C2, 10.10.2002

RU 2181894 C1, 04/27/2002

RU 2178892 C2, 01.27.2002

SU 1781628 A1, 12/15/1992

SU 1780022 A1, 12/07/1992

SU 1422199 A1, 09/07/1988

US 7692421 B2, 04/06/2010

US 6362745 B1, 03/26/2002

EP 1065508 A2 01/03/2001

Claims (1)

A bridge device for calibrating induction-type active energy electric meters, which contains transistors switching the charge current of the capacitors controlled from a modulated high-frequency pulse generator, characterized in that it is made according to a bridge circuit, the first and second branches of which, connected in parallel to the mains, include a capacitor in series and bidirectional transistor switch of two of the same type of parallel-counter-connected transistors, the first branch of the bridge with emy connected to the network phase conductor bidirectional transistor switch, and the second branch - a condenser, and a diagonal of the bridge circuit including control triac (bidirectional thyristor), the control operation of four transistors and triac effected by the control unit, synchronized by the mains voltage.

Images