RU2088943C1 - Method and device for serviceability check of electronic meter - Google Patents

Abstract

FIELD: electric measurement technology; electricity meters. SUBSTANCE: meter serviceability is estimated by difference in reactive and active power and danger of phase shift between current and voltage in supply mains. Device has set of supply mains phase current and voltage transformers. active and reactive power sensors, unit for measuring phase shift between supply mains current and voltage, computer, main and read-only storage units, calendar clock, meter-to-regional-information-system communication system. EFFECT: provision for serviceability check of electricity meter. 3 cl, 1 dwg

Description

 The invention relates to electrical engineering and can be used in power equipment in power grids.

 A device is known for measuring the active and reactive powers of harmonics in an electric circuit [1] containing sensors of instantaneous values of current and voltage, multiplication blocks, summing and subtracting blocks, a sine-cosine generator and two blocks for determining the coordinates of harmonic vectors. The disadvantage of this device is the inability to control a complex electronic device.

 Closest to the proposed method and device are a method of measuring active and reactive energies in three-phase networks and an electronic meter that implements this method [2] The meter contains current and voltage transformers, energy sensors, a microprocessor with random and permanent memory, a display and a device for recording data in microprocessor.

 The disadvantage of this method and device is the inability to assess the health of current and voltage transformers, power sensors, etc. in the process of regular operation.

 The basis of the invention of the provisions is the task of providing the possibility of assessing the health of an electricity meter.

где Φ_n угол сдвига между напряжением и током n-й фазы;

число фаз электросети;
P_n активная мощность электросети;
Q_n реактивная мощность электросети;
ΔP_n абсолютная погрешность измерения активной мощности, определяемая классом точности счетчика;
ΔQ_n абсолютная погрешность измерения реактивной мощности, определяемая классом точности счетчика;
ΔΦ_n абсолютная погрешность измерения углов сдвига между напряжением и током фаз электросети;
ΔHП_n абсолютная погрешность вычислений микропроцессора по приведенному критерию работоспособности;
ΔHC_n абсолютная погрешность, вносимая нелинейностями напряжений и токов электросети;

количество импульсов частоты заполнения, пропорциональное углу сдвига между напряжением и током фазы;

количество импульсов частоты заполнения, пропорциональное частоте электросети.This is achieved by the fact that in the method of monitoring the operability of an electronic multiphase energy meter that measures active and reactive powers, the shear angles between the voltages and currents of each phase of the electrical network are additionally measured, and the performance criterion is calculated by the formulas

where Φ _{n is the} angle of shift between voltage and current of the nth phase;

number of phases of the power supply network;
P _n active power;
Q _n reactive power of the power grid;
ΔP _{n the} absolute error of the measurement of active power, determined by the accuracy class of the meter;
ΔQ _n absolute error of reactive power measurement, determined by the accuracy class of the counter;
ΔΦ _{n the} absolute error of the measurement of shear angles between the voltage and the current phases of the mains;
ΔHP _n absolute error of microprocessor calculations according to the given performance criterion;
ΔHC _{n is the} absolute error introduced by the nonlinearities of the voltage and currents of the power supply network;

the number of pulses of the filling frequency, proportional to the angle of shift between the voltage and the phase current;

the number of filling frequency pulses proportional to the frequency of the mains.

 The device for monitoring the health of an electronic meter, containing a block of current and voltage transformers, the outputs of which are connected to the inputs of active and reactive power sensors, a data highway, addresses and interrupts, read-only memory, electronic clock-calendar, control panel, display and communication device with the regional information system, an additional device for measuring the angle of shear between the voltage and the current of the phases of the power supply network, the inputs of which are connected to the outputs of the unit current and voltage transformers and electronic calendar clocks, as well as a meter for evaluating the health of the meter, which is connected to the outputs of active and reactive power sensors, a device for measuring the angle of shear between voltage and current of the phases of the power supply network, with an electronic calendar clock operational and permanent storage devices, control panel, display and communication device with the regional information system.

 A device for measuring the angle of shear between voltage and current of the phases of the mains is made in the form of a series-connected shaper of temporary strobe voltage and currents of three phases, the inputs of which are connected respectively to the output of the block of transformers of currents and voltages and a data line, address and interruptions and a block for measuring the angle of shear, the input of which connected to the output of the electronic clock-calendar, and the output to the highway data, addresses and interrupts.

 In FIG. 1 shows a structural diagram of a counter that implements the proposed method; in FIG. 2 is a structural diagram of a device for measuring a phase shift between the voltage and current of each phase of the power supply network; FIG. 3 is a functional diagram of a voltage gate generator of voltages and currents of three phases; in FIG. 4 is a functional diagram of a unit for measuring shear angles between voltage and phase current of a power supply network; in FIG. 5 is a timing diagram of the operation of the shear angle measuring unit without phase switching from the microprocessor; in FIG. 6 is a timing diagram of the operation of the shear angle measurement unit when switching the phases of the microprocessor.

 The device for monitoring the health of an electronic meter contains a block 1 of current and voltage transformers, a sensor 2 for active power, a sensor 3 for reactive power, a device 4 for measuring the angle of shear between voltage and current of the phases of the mains, a calculator 5 for evaluating the performance of the meter (microprocessor), random access memory 6, permanent storage device 7, electronic clock-calendar 8, control panel 9, display 10 and communication device 11 with the regional information system, data highway 12, addresses and eryvany.

 The device 4 for measuring the angle of shear between the voltage and current of the phases of the mains contains a shaper 13 of the temporary strobe voltage and currents of the three phases and the unit 14 for measuring the angle of shear (Fig. 2).

 The generator 13 of the temporary strobe voltage and currents of three phases contains a voltage switch 15, a switch control unit 16 (decoder), an active analog bandpass filter 17 for the fundamental, a comparator 18 of the voltage level (Fig. 3).

 Block 14 measuring the angle of shear contains the element NOT 19, the first element And 20, the trigger 21 with a counting input, the element 22 of the selection of the trailing edge, the element 23 of the selection of the leading edge, the second element And 24, the register 25 of the angles of shift, the counter 25 of the angle of shift, counter 26 frequency (Fig. 4 )

 The proposed method for monitoring the health of an electronic meter is implemented by the device (Fig. 1) and consists in the following. Using sensors 2 and 3 measure the active and reactive power, device 4 measure the angle of shear between the voltages and currents of each phase of the mains. The measured values along the line 12 are sent to the calculator 5 evaluating the health of the counter (microprocessor), where the health criterion is calculated.

где P активная мощность;
Q реактивная мощность;
Φ угол сдвига между напряжением и током фазы;
C параметр, определяющий абсолютную погрешность метода.To assess the performance of the electricity meter, a ratio is introduced that allows you to check the electricity meter without disconnecting it from the mains

where P is the active power;
Q reactive power;
Φ is the shear angle between voltage and phase current;
C is a parameter that determines the absolute error of the method.

где K_p% класс точности датчиков активной мощности;
абсолютной погрешности измерения реактивной мощности

где K_Q% класс точности датчика реактивной мощности;
абсолютная погрешность измерения угла сдвига ΔΦ;
абсолютная погрешность вычисления микропроцессора DМП соотношения (1);
абсолютная погрешность, вносимая несинусоидальностями токов и напряжений электросети ΔHC.Parameter C includes the sum of:
absolute error of measurement of active power

where K _p % accuracy class of active power sensors;
absolute error of measurement of reactive power

where K _Q % accuracy class of the reactive power sensor;
absolute error of measurement of the angle of shift ΔΦ;
the absolute error in calculating the microprocessor DMP ratio (1);
absolute error introduced by non-sinusoidal currents and voltages of the power supply ΔHC.

где

число гармоник электросети;
U_n действующее значение напряжения n гармоники;
J_n действующее значение тока n гармоники;
U₁ действующее значение напряжения основной гармоники;
J₁ действующее значение тока основной гармоники.The absolute error introduced by the non-sinusoidal currents and voltages is derived from the following relationship:

Where

number of harmonics of the power supply network;
U _{n is the} effective value of the harmonic voltage n;
J _{n rms} current value n of the harmonic;
U _{1 the} effective value of the voltage of the fundamental;
J ₁ effective value of the fundamental current.

(ГОСТ 13109-87, Требования к качеству электрической энергии, с. 11; РД 34715.501-88, Методические указания по контролю и анализу качества электрической энергии, с. 4, табл. 1.1, графа "дополнительные изменяемые величины"; Круг К.А. Теория переменных токов. Том 2. Гос. энергетическое изд-во, М. 1946, с. 263; Бессонов Л.А. Теоретические основы электротехники; М. Высшая школа. 1964, с. 250).The coefficient of non-sinusoidality of voltage and current is determined

(GOST 13109-87, Requirements for the quality of electric energy, p. 11; RD 34715.501-88, Guidelines for monitoring and analyzing the quality of electric energy, p. 4, table 1.1, column "additional variable values"; Circle K.A Theory of Alternating Currents, Volume 2. State Energy Publishing House, M. 1946, p. 263; Bessonov L.A. Theoretical Foundations of Electrical Engineering; M. Higher School. 1964, p. 250).

.Taking into account relations (3) and (4), relation (2) takes the form

.

.The ratio of reactive power to active in this case is determined

.

При этом известно, что практически значение угла сдвига Φ < 60^°. и, следовательно, tgΦ < 2.
Следует отметить, что угол сдвига в соответствии с функциональной схемой фиг. 4 вычисляется по формуле

где Φ угол сдвига между напряжением и током фазы в радианах;
N_Φ количество импульсов частоты заполнения, пропорциональное углу сдвига между напряжением и током фазы;
N_f количество импульсов частоты заполнения, пропорциональное частоте электросети.The absolute error introduced by the nonlinearities of the current and voltage of the mains will be determined in this case from the relation (1)

It is known that, in practice, the shear angle Φ <60 ^° . and therefore tgΦ <2.
It should be noted that the shear angle in accordance with the functional diagram of FIG. 4 is calculated by the formula

where Φ is the shear angle between the voltage and phase current in radians;
N _{Φ the} number of pulses of the filling frequency, proportional to the angle of shift between the voltage and the phase current;
N _{f the} number of pulses of the filling frequency, proportional to the frequency of the mains.

 The absolute error of the measurement of the angle of shear is determined by the frequency of filling the meter and the accuracy of determining the transition time of sinusoidal voltages from transformers of currents and voltages through zero.

 The absolute error of microprocessor calculations by relation (1) can be calculated with a predetermined accuracy.

где T время накопления энергии;
Δt период расчета по соотношению (7), равный 20,66. мс для трехфазного счетчика (фиг. 6);
Φ_nj углы сдвига между напряжениями и токами по n-й фазам в j период расчета;
Q_ij, P_ij реактивная мощность n-й фазы в j период расчета; сij-параметр, определяющий абсолютную погрешность метода по n-й фазе в j период расчета;

число фаз электросети;
j ∈ (1; T/Δt) число периодов расчета.Relation (1) for the M-phase counter for an integral assessment of performance over a long time of energy storage takes the form

where T is the energy storage time;
Δt is the calculation period by relation (7) equal to 20.66. ms for a three-phase counter (Fig. 6);
Φ _nj shear angles between voltages and currents along the n-th phases in the j period of the calculation;
Q _ij , P _ij reactive power of the nth phase in j calculation period; cij-parameter that determines the absolute error of the method for the nth phase in the j calculation period;

number of phases of the power supply network;
j ∈ (1; T / Δt) the number of calculation periods.

 The performance assessment of the electronic meter according to relation (7) is determined for a given maximum level of non-sinusoidality of the electric network (GOST 13109-87). In the case when it is impossible to determine the maximum level of non-sinusoidality in the network, and the reliability of the meter’s performance is confirmed, for example, by the balance of the energy of other meters, then relation (7) can serve to assess the non-sinusoidality of the network.

 Evaluation of the operability of the electronic meter without disconnecting from the mains allows service personnel or the central control center (regional information system) to have up-to-date information on the correct functioning of the meter, taking into account the non-sinusoidality of the mains.

 The proposed device operates as follows.

 From block 1 of current and voltage transformers, signals proportional to currents and voltages of three phases are fed to active 2 and reactive 3 power sensors, as well as to device 4 for measuring the angle of shear between voltage and phase current of the power supply network. Information about the active, reactive power, shear angles along the line 12 is supplied to the calculator 5. Information about the current time from block 8 is also sent via the line 12 to the calculator 5, in which information on the program stored in the read-only memory 7 is processed with storage of intermediate results in random access memory 6. The results of the calculation of the calculator 5 on the highway 12 are either displayed on the display 10, or in the regional information system through the communication device 11 by command Remote control keypad input 9.

 Voltages proportional to the currents and voltages of the three phases are supplied to the former 13 (Fig. 2), along the line 12 from the calculator 5 to the former 13 also receive the command "Phase switching". At the output of the shaper 13, gates 27 and 28, respectively, of voltage and current are generated, which are supplied to the first and second inputs of the shear angle measuring unit 14, the third input of which receives the fill frequency signal from the quartz oscillator of the electronic calendar clock 8. Information on the phase angle block 14 measurement enters the highway 12 to the transmitter 5.

 Voltages proportional to the currents and voltages of the three phases from block 1 are supplied to the voltage switch 15 (Fig. 3), which is switched by the switch control unit 16 according to the "Phase switching" commands from the calculator 5 along the line 12 (Fig. 6). The first output of the switch in the form of a voltage proportional to the voltage of one of the three phases, and the second output in the form of a voltage proportional to the current of one of the three phases, is fed to the analog bandpass filters 17 of the main harmonic, from the output of which the signals are transmitted to the comparators 18 voltage levels. At the output of the comparators, temporary gates 27 and 28 are formed, respectively, of voltage and current.

 The temporary voltage gate 27 (Fig. 4) and the time current gate inverted on the element HE 19 pass through the element And 20, at the output of which a temporary gate 29 of the shift angle of the three phases is formed. A temporary voltage gate 27 is supplied to the counting input of the trigger 21, from the output of which the signal (divided by two network frequencies) 30 is supplied to the trailing edge selection element 22, to the leading edge selection element 23 and to the I element 24. A signal is generated at the output of the element 22 " Interruption of the microprocessor ", coming to the highway 12. At the output of element 23, a signal 31 for resetting the frequency counter 26 and the shift angle register 25 is generated. The frequency from the crystal oscillator of block 8 is fed to the input of the frequency counter 26. The rewriting of information about the angle of shear from the frequency counter 26 to the register 25 of the angle of shear is carried out by the trailing edge of the strobe 29 of the angle of shear of the three phases. Information about the angle of the electric grid shift is read by the calculator 5 along the line 12. Timing diagrams explaining the operation of the block 14 for measuring the shift angles and frequency are shown in FIG. 5 and 6.

Claims (3)

1. A method of monitoring the health of a multiphase electronic electricity meter, including measuring active and reactive powers, characterized in that they measure the angle of shear between the voltages and currents of each phase of the power grid, and the health criterion is calculated by the formulas

where P _{n is the} active power of the nth phase of the power grid;
Q _n reactive power of the nth phase of the power grid;
T period of voltage in the mains;
Δt _n is the time shift between voltage and current in the n-th phase of the power grid;
C is a parameter that determines the absolute error of the method.  2. A device for monitoring the operability of a multiphase electronic electric power meter, containing a block of current and voltage transformers, the outputs of which are connected to the inputs of active and reactive power sensors, a data highway, addresses and interrupts, read-only memory, electronic clock-calendar, control panel, display and a communication device with a regional information system, characterized in that it additionally includes a device for measuring shear angles between voltage and current from the mains, the inputs of which are connected to the outputs of the block of current and voltage transformers and the electronic calendar clock, as well as a calculator for evaluating the operability of a multiphase electronic electricity meter, which is connected to the outputs of the sensors of active and reactive powers, a device for measuring the angle of shift between voltage and current of the phases of the power supply network, with an electronic clock-calendar, operational and read-only memory devices, control panel, display and device ide with the regional information system.  3. The device according to claim 2, characterized in that the device for measuring the angle of shear between voltage and current of the phases of the mains is made in the form of series-connected shaper of temporary strobe voltages and currents of three phases, the inputs of which are connected respectively to the output of the transformer unit of currents and voltages and a data line , addresses and interrupts, and a unit for measuring shear angles, the input of which is connected to the output of the electronic clock-calendar, and the output to the data highway, addresses and interrupts.

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