RU153470U1 - MEASURING-COMPUTING COMPLEX FOR ACCOUNTING THE NATURAL GAS EXPENDITURE - Google Patents

Abstract

The measuring and computing complex for natural gas consumption accounting contains a central processor unit based on a single-chip microcomputer, a built-in analog-to-digital converter and a voltage reference source, inputs for connecting current sensors of 4–20 mA standard, a block of precision resistors, a real-time clock unit, and a read-only memory , data input-output terminal, power control unit, characterized in that the power control unit further comprises an external voltage control module and an emergency power supply, while the external power supply control module monitors external power supply voltages and, when the external power supply is switched off abnormally, it switches the device power supply from the emergency power supply and transmits to the central processor unit a signal to turn off the external power supply, according to which the software performs the procedure for saving current reports to read-only memory.

Description

The device relates to the gas industry, enterprises of transport and storage of products of the gas industry and can be used as a part of measuring systems for the quantity and quality indicators of gases for quantifying the volumetric consumption of natural gas under operating and standard conditions and the mass consumption of natural gas.

Known measuring and computing complex (IVK) "OKTOPUS-L" (RU 96954, publ. 08/20/2010). The principle of operation of this CPI is based on measuring and converting the input signals from the primary converters (sensors) into a digital code with the subsequent calculation of the volume, mass and physicochemical parameters of oil products and gases and the provision of summary reports on their quality and quantity. The device is made on the basis of an industrial computer and is designed for parallel servicing of several measuring lines at once.

The disadvantage of this device is that, if necessary, process information from a small number of sensors on a separate measuring line, its functionality is redundant, and the application becomes economically impractical.

Closest to the claimed technical solution (prototype) is a CPM device for automated metering of natural gas consumption on a separate measuring line consisting of a microcontroller with loaded software (software), a real-time clock chip, a flash memory chip, a data input / output terminal, block of precision resistors, connectors for connecting current sensors of 4-20 mA standard, power supply unit (AN Grachev, DS Kutuzov. Measuring and computing complex for automated metering natural gas consumption. / AN Grachev, DS Kutuzov. // Bulletin of the Tver State University. Series "Physics", - 2013. - No. 39. - P. 82-93.).

This device is designed to measure with the help of current sensors of the 4-20 mA standard the primary parameters of natural gas: temperature, pressure, volumetric flow rate under operating conditions, as well as atmospheric pressure; calculation of volumetric flow rate on them under standard conditions and mass flow rate of gas, the formation of operational, shift and daily reports on natural gas consumption.

The disadvantage of this device is that it does not provide protection against loss of information during an emergency shutdown of the supply voltage.

The purpose of this technical solution is to create a CPI designed for automated metering of natural gas consumption on a separate measuring line with protection against information loss during an emergency power outage.

This problem is solved due to the fact that the measuring and computing complex for accounting for natural gas consumption contains a central processor unit based on a single-chip microcomputer, a built-in analog-to-digital converter and a reference voltage source, inputs for connecting current sensors of the 4-20 mA standard, a block of precision resistors, real-time clock unit, read-only memory, data input-output terminal, power control unit. The power control unit may additionally contain an external power supply control module and an emergency power supply, while the external power supply control module monitors external power supply voltages and, when the external power supply is switched off abnormally, switches the device power supply from an emergency voltage source and transmits a signal to the central processor unit disconnecting the external supply voltage, according to which the software performs the procedure for saving current reports to read-only memory.

The technical result provided by the given set of features is to ensure that current reports on natural gas consumption are stored in a permanent memory (ROM) of the IVK during an emergency power off, which increases the efficiency of monitoring natural gas consumption.

The essence of the device is illustrated by drawings, which depict:

In FIG. 1. A functional diagram of the IVC implements the processing of signals from current sensors of the 4-20 mA standard on a separate measuring line is presented.

In FIG. 2. The electric circuit of the module for monitoring the external supply voltage and the emergency power source connected to it is presented.

The device includes a central processor unit (1), a built-in analog-to-digital converter (ADC) (2), a voltage reference source (3) for the ADC, inputs for connecting current sensors of the 4-20 mA standard (4), a block of precision resistors (5) , real-time clock unit (6), read-only memory (ROM) (7), data input-output terminal (8), power control unit (9), step-down converters (10), external power supply voltage monitoring module (11), emergency voltage source (12).

The external power supply control module (11) includes a connector for external power supply (13), a self-resetting fuse (14), a zener diode (15), resistors (16.17), a capacitor (18), a protective diode (19), a capacitor (20 )

The device includes a central processor unit (1) based on a single-chip microcomputer (microcontroller) with loaded software (software), built-in analog-to-digital converter (ADC) (2) and a voltage reference source (3) for the ADC. The external voltage control module (11) is connected to the emergency power source (12), which is a capacitor (20).

The device operates as follows. When the device is turned on, the software initializes the hardware of the central processor unit (1), namely: setting the clock frequency of the microcontroller; setting up the basic input / output system; setting interfaces for data exchange with the real-time clock block (6), ROM (7) and data input-output terminal (8); tuning of the ADC integrated in the microcontroller (2) and the voltage reference source (3); setting up a comparator integrated in the microcontroller for interaction with the power control unit (9); loading the settings of the IVK from the ROM (7).

In the main operating cycle of the device, signals from sensors (4) are measured, gas consumption is calculated, data is exchanged with the data input-output terminal (8), and reports on natural gas consumption are generated and saved.

To measure the primary parameters of the gas (its temperature, pressure and volumetric flow rate under operating conditions, as well as atmospheric pressure), the IVK uses current sensors of the 4–20 mA standard. The IVK has 8 current inputs, for connecting current sensors of the 4-20 mA standard, the error in measuring the current strength does not exceed ± 6 μA. The current measurement from the sensors is carried out by the ADC built into the microcontroller (2). The current from the sensors on each of the ADC channels is determined by the voltage drop across the corresponding precision resistor (5). The software polls the ADC channels to obtain digital codes of signals from sensors for each channel and converts the received digital codes into units of measured physical quantities of the primary gas parameters.

The calculation of the volumetric flow rate of natural gas under standard conditions and the mass flow rate of natural gas is carried out in accordance with the calculation methods set forth in documents GOST 30319-96. Interstate standard. “Natural gas. Methods for calculating physical properties ”and GOST 8.586-2005. Interstate standard. "Measurement of the flow rate and amount of liquids and gases using standard constricting devices."

The natural gas consumption accounting program operates with the following parameters.

Measured values determined by signals from sensors:

- codes, voltages and currents on the ADC channels;

- primary gas parameters:

gas temperature, ° C;

gas pressure, Pa;

gas volumetric flow rate under operating conditions, m ³ / h;

- atmospheric pressure, Pa. Constants stored in the IVK settings:

- scales of sensors on ADC channels (the boundary values of the values X ₄ and X ₂₀ measured by the sensor corresponding to the boundaries of the current range of 4–20 mA);

- calibration corrections of ADC channels;

- constants of temperature, pressure and density of natural gas under standard conditions (s.u.): T _s = 293.15 K (20 ° C), P _s = 101325 Pa (1 atm.), ρ _s = 0.668-0, 7 kg / m ³ ;

- molar fractions of associated gases: N ₂ x _a and CO ₂ x _y .

Intermediate values calculated during the program:

- gas compressibility coefficient;

- compressibility factors under working and standard conditions;

- gas density under operating conditions.

Output used in generating reports:

- volumetric flow rate under standard conditions, m ³ / h;

- mass flow rate, t / h;

- average values of temperature (° C) and pressure (Pa) of gas for the reporting period.

GOST 30319.2 establishes four methods for determining the compressibility coefficient of natural gas, and also sets the preferred areas of application of each method for measured parameters (pressure, temperature, density of natural gas under standard conditions and component composition of natural gas), but does not prohibit the use of any of the methods in other areas.

To calculate the compressibility factor of natural gas when determining its flow rate, this modified CPI uses the modified NX19mod method. for natural gases with a density ρ _c = 0.668-0.70 kg / m ³ in the temperature range 250-290 K and pressures up to 3 MPa; the error in calculating the compressibility coefficient in these parameter ranges does not exceed 0.11%; The indicated ranges of parameters are characteristic for measuring the flow rate and quantity of gas during its distribution to consumers.

Calculated CPI quantitative indicators of gas:

- volumetric flow rate (m ³ / h) of natural gas under standard conditions;

- mass gas flow (t / h) under operating conditions;

- average values of temperature (° C) and pressure (Pa) of gas for the reporting period.

The correctness of the calculation program was verified using test cases of the ISO FLOW METER complex developed by STP LLC and certified by the All-Russian Research Institute of Flow Metering.

The CPI generates gas consumption reports having the following structure:

- type of report: operational / shift / daily;

- creation date and time: dd / mm / 20gg hh: mm: ss;

- Duration: 1/2/3/4/6/8/12/24 (h) for operational and shift reports, 24 (h) for per diem;

- quantitative indicators of natural gas during the report:

- gas volume under operating conditions, m ³ ;

- gas volume under standard conditions, m ³ ;

- mass of gas, t;

- average values of temperature (° C) and pressure (Pa) of gas.

The CPI supports the parallel generation of three types of reports: operational, shift and daily; with the ability to configure the duration of operational and shift reports.

The software implements the data exchange interface between the central processor unit (1) and the real-time clock unit (6) connected to it to obtain the date and time of reporting.

The software implements the data exchange interface between the central processor unit (1) and the ROM connected to it (7), saves new reports to the ROM at a specified time and provides access to the saved reports.

The software implements the data exchange interface between the central processor unit (1) and the data input-output terminal (8) connected to it, polls the keyboard of the terminal, saves the entered settings in ROM (7), displays the instrument readings on the terminal display and supports the following functions:

- View codes, voltages and currents on ADC channels;

- viewing sensor readings (temperature, pressure, gas flow and atmospheric pressure);

- View current gas mass and volume flow rates;

- View saved reports (operational, shift and daily);

- View and set the date and time;

- testing the work of the CPI calculation program using the built-in set of test cases;

- setting the duration of operational and shift reports;

- setting the binding of current sensors to specific ADC channels;

- manual input (using the keyboard) of the sensor scales: parameters X ₄ and X ₂₀ ;

- manual input of the density constant of natural gas under standard conditions ρ _s ;

- manual input of the molar fractions of associated gases (nitrogen and carbon).

Using the step-down voltage converters (10), the power control unit (9) converts the input power voltage into stabilized voltages of the corresponding ratings for powering the central processor unit (1), current sensors (4), real-time clock unit (6), ROM (7) and a data output input terminal (8).

The external power voltage is supplied from the connector (13) to the voltage divider from resistors (16) and (17). The divider lowers the supply voltage to the required level and transfers it to the “+” input of the analog comparator in the central processor unit (1), while the capacitor (18) smoothes the voltage ripple at the “+” input of the comparator, preventing its false positives.

The zener diode (15) and the fuse (14) serve to protect the IVC from a voltage exceeding its rated supply voltage.

When the device is powered from an external voltage source, a capacitor (20) is charged, while the fuse (14) limits the current flowing through the capacitor (20). The voltage from this capacitor is through a step-down converter in the power control unit (10). It goes to the input “-” of the comparator as a reference.

In the event of an emergency shutdown of the supply voltage at the input of the IVK, when the voltage at the “+” input of the comparator becomes lower than at the “-” input, the comparator is triggered in the central processor unit, by which the software in the central processor unit starts the emergency emergency and daily reports in ROM (7).

At this time, the power supply of the IVK units is carried out due to the charge accumulated on the capacitor (20), which serves as an emergency power source (12), while the diode (19) prevents the discharge of the capacitor (20) to the previous stage of the circuit.

The next time you turn on the device, the CPI software compares the current time with the time that each emergency report was generated. If the current time exceeds the planned time at which this report was to be saved in the normal mode (for example, if the report was to be saved at 14:00, but the device turned off at 13:30, and the next turn on at 14:30), then this the report is saved in the report archive as incomplete, and the new report begins to accumulate from scratch. Otherwise, the CPI restores this report, continues to accumulate it and saves it to the archive of reports “according to the schedule”.

Verification of the procedure for calculating natural gas consumption using test cases of the ISO RACHODOMER software package certified by the Federal State Unitary Enterprise All-Russian Scientific Research Institute of Flow Metering (FSUE VNIIR) shows that its algorithms for calculating the volumetric gas flow under standard conditions, the mass gas flow rate, gas compressibility factors under operating and standard conditions and gas compressibility factor are written strictly in accordance with the calculation methods set forth in normative documents GOST 30319-96 and 8.586-20 05.

Verification of the measurement of signals from current sensors over 8 ADC channels using an external equipment verification device (UPVA) that produces a reference current signal with an accuracy of 1 μA shows that the software algorithm for moving averaging with floating point in conjunction with linear calibration of ADC channels using the accuracy of the ADC code ± 1 low order ensures the boundaries of the current range of 4–20 mA, which in this device corresponds to an error of current measurement of ± 6 μA (with an acceptable error of ± 15 μA).

As a result of testing the operation of the power control unit in the maximum current consumption mode, it was found that the stability of the step-down voltage converters does not depend on the current consumed by the device.

Testing the IVC in the mode of switching off the supply voltage at a maximum current consumption of 200 mA shows that the capacitor with a capacity of 22000 μF in the power control unit provides the operation of the IVC for 1-2 seconds. During this time, the procedure for completing work and saving emergency operational, shift and daily reports, as well as the settings of the CPM in the ROM, is performed. The procedure is performed in 0.5 sec., I.e. there is a sufficient supply of operating time of the IVC from the capacitor.

During testing the operation of the CPM in the reporting mode for 7 days, there were no malfunctions in the operation of the device.

Claims (1)

The measuring and computing complex for natural gas consumption accounting contains a central processor unit based on a single-chip microcomputer, a built-in analog-to-digital converter and a voltage reference source, inputs for connecting current sensors of 4–20 mA standard, a block of precision resistors, a real-time clock unit, and a read-only memory , data input-output terminal, power control unit, characterized in that the power control unit further comprises an external voltage control module and an emergency power supply, while the external power supply control module monitors external power supply voltages and, when the external power supply is switched off abnormally, it switches the device power supply from the emergency power supply and transmits to the central processor unit a signal to turn off the external power supply, by which the software the procedure for saving current reports to read-only memory.

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