RU2569178C1 - Device for testing of inductive electric meters - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: invention claims the device for testing inductive electric meters designed with bridge circuit and consisting of the first and second circuits comprised of in-series storage capacitor and power transistor and coupled in parallel to phase and neutral lead downwards electric meters, at that in the first circuit storage capacitor is connected to the phase lead, while in the second circuit power transistor is connected to the phase lead, and in the second circuit power transistor is connected to the phase lead, between midpoints of both circuits there is thyristor, and the above device is differentiated by in-series connection of choke to the thyristor, and inductance of this choke together with storage capacitors of the above circuits switched on at open thyristor forms in-series resonant circuit adjusted to double frequency of the mains.

EFFECT: simplification of the device designed with bridge circuit without high-frequency current splitting for charge of storage capacitors.

2 cl, 3 dwg

Description

The claimed technical solution was created with the aim of instructing the energy supplying organizations to completely replace the fleet of induction metering devices without a backstop for rotating aluminum disks of the СО-2М type, which are still widespread throughout the country, since they allow theft of electricity by the so-called rewinding of readings by reversing disk rotation.

It is known that the inclusion of a capacitor with a capacity of C on the network does not change the readings of the active energy electric meter, since in this case the electricity circulates in the network with a double frequency. In the first quarter of the period of the mains voltage, such a capacitor is charged to the amplitude value U (for a 220 V network, the amplitude is U = 310 V), and in the second quarter of the period it transfers its charge back to the network. In the third quarter of the period, the capacitor is recharged to an amplitude value of U = -310 V, and in the fourth quarter it again discharges completely back to the network. The capacitor charge current in the first quarter of the period (or overcharge in the third quarter of the period) changes from zero at t = 0 to the maximum at t = Τ / 8, where Τ is the period of fluctuation of the mains voltage, and then towards the end of the first quarter of the period at t = Τ / 4 becomes zero again. This significantly distinguishes the current when charging the capacitor to the amplitude value U at the end of the first quarter of the period from the current in the active load, in which the current, on the contrary, increases with increasing voltage and is maximum at t = Τ / 4, and is equal to I _MAX = U / R, where R is the resistance value of the active load.

An electric meter calculates energy by multiplying the instantaneous values of current and voltage and integrating the result of such multiplication for any arbitrary period of time. If we consider the energy for the first quarter of the period 0≤t≤Τ / 4, which is actually spent for the charge of the capacitor C and for heating the resistor R the same, then taking into account the difference in the change in currents during the charge of the capacitor C and when passing through the resistor R as a function of the harmonic law of the mains voltage can be shown that the meter responds differently to these loads, underestimating the readings of the energy it takes into account for a quarter of the period when the capacitor is charged in comparison with the case of connecting an active load, which is clearly visible and h comparing the following integrals

Consequently, for the same consumed is actually power a quarter of a period of counting it turns out to be different: electric meter under reads energy consumed by connecting the condenser to the 0.785 / 0.667 = 1.18 times as CU ^2/2 = ΤU ² / 8R, ie ensured equality consumed energies in C and R.

The author has proposed various versions of the devices with which it is possible to violate the correct metering of electricity in induction meters [1-8], which are designed to verify the meters in the process of their development, which provides insensitivity to high-frequency interruption of the current passing through the current coil of the meter.

The closest known technical solution to the violation of the correct metering of electricity can be considered a bridge device for checking active energy electric meters, considered in [2], and containing transistors switched by a charge current of capacitors controlled from a modulated high-frequency pulse generator, characterized in that it is made according to a bridge circuit, the first and the second branch of which, parallel to the mains, includes a series-mounted and bi-directional transistor switch of two of the same type of parallel-counter-connected transistors, with the first branch of the bridge circuit connected to the phase conductor of the network by a bi-directional transistor switch, and the second branch by a capacitor, and a controlled triac (bi-directional thyristor) is included in the diagonal of the bridge circuit, the operation of four transistors and a triac is carried out from the control unit synchronized by mains voltage. In this case, the most complex node of such a circuit is the power transistor control unit and the triac.

The aim of the invention is to simplify a device made according to a bridge circuit without high-frequency fragmentation of the charge current of the storage capacitors.

This goal is achieved in a device for calibrating induction electric meters, made according to a bridge circuit and containing first and second identical circuits connected in parallel to the phase and neutral conductors after the metering meter for electricity, with a storage capacitor and a power transistor connected in series, and a storage capacitor connected to the phase conductor in the first circuit , and in the second circuit a power transistor is connected to the phase conductor, a thyristor is connected between the midpoints of both circuits (or torus), characterized in that the inductor is connected in series to the thyristor, the inductance of which together with the storage capacitors of the indicated circuits connected in series with the thyristor open, forms a series resonant circuit tuned to the double frequency of the network, and the power transistors of the first and second circuits open in the first quarter of each network period voltage and close in the rest of the period, and the thyristor opens at the end of the first quarter of each period using the power control unit with transistors and thyristor.

The power transistor and thyristor control unit includes two comparators, the first of which is connected directly to the network through an adjustable voltage divider, and the second through an additional phase-shifting circuit on π / 2 with an adjustable voltage divider, the outputs of both comparators are connected to the coincidence circuit, the output of which is in the control circuit the thyristor is connected to a series-installed inverter, a differentiating circuit and an amplifier with a transformer output, and in a control circuit of power transistors it is connected with an amplifier with a transformer output having two separate secondary windings connected to the base-emitter junctions of the power transistors through grids from a parallel-connected limiting resistor and capacitor with a time constant exceeding the period of the mains voltage.

The simplification of the device is associated with the reorganization of the power transistor control unit by eliminating the circuits for high-frequency fragmentation of the charge current of the storage capacitors and the use of a choke. This became possible due to the fact that the maximums of instantaneous power during charging are less than the maximum of instantaneous power during discharge of storage capacitors.

In this case, the meter readings rewind despite the fact that the energy of the charge and discharge of the storage capacitors is the same as it follows by analogy with expressions (1) and (2).

The schematic diagram of the device is shown in Fig. 1, the circuit of the power transistor and thyristor control unit is shown in Fig. 2, illustrated by the graphs in Fig. 3.

The inventive device (Fig. 1), connected after the verified electric meter, consists of the following elements:

1 - the first storage capacitor with a capacity of C,

2 - the first power transistor n-p-n-type,

3 - second power transistor n-p-n-type,

4 - the second storage capacitor with a capacity of C,

5 - thyristor,

6 - throttle inductance L,

7 - control unit power transistors and thyristor.

The control unit 7 includes:

8 - the first adjustable AC voltage divider,

9 - intermediate voltage divider,

10 - phase-shifting circuit at π / 2,

11 is a second adjustable divider phase-shifted AC voltage,

12 is the first comparator,

13 - second comparator,

14 is a coincidence diagram,

15 - inverter on the chip "I-Not",

16 - differentiating circuit,

17 - amplifier positive pulses,

18 - transformer control circuit of the thyristor,

19 - limiting resistance

20 - pulse amplifier control circuit power transistors,

21 - transformer with two separate secondary windings,

22 - grid capacitors.

In fig. Figure 3 shows graphs of the alternating voltage of the network (acting in the counter voltage coil, without considering its change during the discharge of storage capacitors), the charge current of the storage capacitors in the first quarter of each period Τ the mains voltage and their discharge in the second quarter of each period (flowing in the current coil of the meter) as well as pulses opening the thyristor.

Consider the operation of the claimed device.

It is easy to understand that at the outputs of the first 12 and second 13 comparators a series of rectangular pulses of the meander type are formed, shifted in time by a quarter of the period of the sinusoidal voltage of the network, so that at the output of the matching circuit 14 there are rectangular pulses of positive polarity, tied in time to the interval from 0 to Τ / 4 in each of the sequence of periods of the mains voltage. After inverting these pulses at 15 and differentiating them at 16, as well as amplifying the positive differentiating pulses at 17, pulses are generated on the secondary winding of the transformer 18, starting the opening of the thyristor 5 at the end of the first quarter of each of the mains voltage periods. The pulses from the output of the matching circuit 14 also go to the input of the pulse amplifier 20, from two separate windings of the transformer 21 which are pulsed signals that open the power transistors 2 and 3 in the first quarter of each of the periods of the mains voltage. We emphasize that the opening of thyristor 5 occurs only after the power transistors 2 and 3 are completely closed at the end of the first quarter of each period of the mains voltage, in order to avoid self-discharge of the storage capacitors 1 and 4 through power transistors 2 and 3, and to direct the discharge current back to the network. The limiting resistors 19 reduce the control current of the thyristor and power transistors to an acceptable value, and the capacitors 22 of grids in the control circuits of the power transistors maintain the necessary level of negative voltage at the bases of the transistors for their reliable locking in time intervals Τ / 4≤t≤T. In this case, the thyristor 5 is turned on at t = Δt + Τ / 4, where Δt << Τ / 4, for example, Δt = 0.1 ms at Τ = 0.02 s.

The maximum current of the simultaneous charge of the storage capacitors 1 and 4 is reached at times t = Τ / 8, when the mains voltage is U / 2 ^1/2 = 220 V, and the maximum discharge current of the series-connected storage capacitors 1 and 4 with their total voltage equal to 2 U = 620 V, is achieved at t = Τ / 4, when the mains voltage is equal to the amplitude value U = 310 V, and the discharge current flows in the opposite direction through the current winding of the meter. The highest value of the discharge current is limited by the use of a choke with an inductance L in the discharge circuit, as a result of which a serial circuit LС / 2 is formed. The inductance of the inductor is selected so that the equality (LС / 2) ^1/2 = Τ / 16π is fulfilled, in which the main part of the discharge energy is concentrated in the first half of the second quarter of each of the periods of the mains voltage, for which the mains voltage varies from 310 V to 220 V Moreover, the voltage in the counter voltage winding during the discharge of storage capacitors additionally increases due to the fact that the voltage of discharged and series-connected capacitors is 620 V at the beginning of the discharge, taking into account the final resistance of the electric line transmission to the counter, although in the network itself - at the installation site of the counter - this voltage is reduced due to the discharge-delaying action of the inductor 6. The indicated processes of charge and discharge of storage capacitors lead to the winding of the counter readings, instead of the latter not changing as it has place when connecting to the network only one capacitor.

The use of a half-wave circuit allows the use of electrolytic capacitors as more energy-intensive at given dimensions.

A more detailed numerical analysis of the effectiveness of such unwinding requires taking into account the resistance of the power line and the internal resistance of the transformer substation, which transfers electricity to the power line to the recording meter.

It is interesting to note that this scheme will exert the same effect on electric meters of other types, in which the procedure of multiplying the instantaneous voltage and current values in the multiplying element and the subsequent integration of the results of such multiplication are applied. Unwinding does not occur in meters with a backstop or digital meters that exclude a reverse stroke in the digital energy reading mechanism. However, if any consumer of electricity and this device are connected to the network at the same time, the metering of electricity will be underestimated by the value of the apparent unwinding.

This leads to the need to develop active energy electric meters that would not be sensitive to the effects of such kind of winding schemes.

Literature

1. Smaller OF, Device for checking the operation of single-phase induction electric meters, Patent No. 2474825, Publ. in the bull. No. 4 dated 02/10/2013;

2. Smaller OF, Bridge device for checking electric meters of active energy of induction type, Patent No. 2522706, publ. in No. 20 of 07.20.2014;

3. Smaller OF, Method of compensating for losses at the end of a long power line, Patent No. 2512706, publ. No. 10 dated 04/10/2014;

4. Smaller OF, The device volt-additive power supply, Patent No. 2517203, publ. No 15 on 05/27/2014;

5. Smaller OF, Device for monitoring electric meters, Patent No. 2521782, publ. No. 19 dated 07/10/2014;

6. Smaller OF, Voltage boosting device for a three-phase power line, Patent No. 2515049, publ. No 13 dated 05/10/2014;

7. Smaller OF, System for stabilizing the voltage on an extended power line, Patent No. 0252311, publ. No. 17 dated 06/20/2014;

8. Smaller OF, Device for researching the operation of induction electric meters, Patent No. 2523109, publ. in No. 20 of 07/20/2014.

Claims (2)

1. The verification device of induction electric meters, made according to the bridge circuit and containing connected in parallel after the metering device to the phase and neutral conductors, the first and second identical circuits with a storage capacitor and a power transistor connected in series, and in the first circuit a storage capacitor is connected, and in the second circuit, a power transistor is connected to the phase conductor, a thyristor is connected between the midpoints of both circuits, characterized in that A throttle is switched on with the thyristor, the inductance of which, together with the storage capacitors of the indicated circuits connected in series with the thyristor open, forms a series resonant circuit tuned to the double frequency of the network, and the power transistors of the first and second circuits open in the first quarter of each network voltage period and close in the rest of period, and the thyristor opens at the end of the first quarter of each period using the power transistor and thyristor control unit. 2. The device according to claim 1, characterized in that the power transistor and thyristor control unit includes two comparators, the first of which is connected directly to the network through an adjustable voltage divider, and the second through an additional phase-shifting circuit to π / 2 with an adjustable voltage divider, outputs both comparators are connected to the coincidence circuit, the output of which in the thyristor control circuit is connected to the inverter, a differentiating circuit and an amplifier with a transformer output, connected in series, and in the control circuit detecting the power transistors connected to the output of the amplifier with a transformer having two separate secondary windings connectable with transitions "base-emitter" through the power transistors of the parallel gridliki limiting resistor and capacitor with a time constant greater than the period of the mains voltage.

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