RU2520428C1 - Microprocessor data recorder for ermakov-gorobets energy audit - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: data recorder contains a current sensor, line voltage sensor, the first and second input converters, a microcontroller, an ambient temperature sensor, a conductor temperature sensor, a square-wave generator, the first and second comparator, the first, second and third receiver-transmitters, a digital data display, read-only memory, a computer.

EFFECT: expansion of functional capabilities due to continuous monitoring and registration of averaged values of power loss, line voltage and load current.

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Description

The present invention relates to the field of information measuring and computing, is intended to calculate and display the average values of power losses, argument f, network voltage and load current, and can also be used as a recorder of these values over a long period.

An analogue of the proposed recorder is an electricity loss counter [1], containing a computer, current sensor, analog-to-digital converter, functional converter, indicator, square-wave pulse generator, timer, timer-clock, accumulating adder, division unit, read-only memory, transceiver, first and second counters, first and second single vibrators.

The disadvantages of the analogue are low accuracy, due to not taking into account the dependence of the active resistance of current-carrying elements of electrical equipment on the heating temperature (the error for this reason can reach 40% [2]), as well as narrow functionality.

The closest technical solution to the proposed registrar is a power loss meter with indication of power losses (options) [3], containing a current sensor, a microcontroller, a register, a digital indicator, sensors of ambient temperature and electrical equipment, a rectangular pulse generator, the first and second transceivers, constant storage device, computer.

The disadvantage of the prototype is the narrow functionality.

The technical problem solved by the invention is the expansion of the registrar's functionality due to the possibility of continuous monitoring and recording of averaged values of power losses, argument f, network voltage and load current.

The specified technical problem is solved due to the fact that the energy loss counter with an indication of power losses (options) contains a current sensor, an ambient temperature sensor, a temperature sensor for a conductor, a rectangular pulse generator, a digital indicator, the first and second transceivers, read-only memory, a computer , a microcontroller whose port E is connected to the output of the ambient temperature sensor, port F is connected to the output of the conductor temperature sensor, and the clock input is connected to the output to the rectangular pulse generator, the outputs of the microcontroller ports are connected respectively H - through the first transceiver with the input of a read-only memory device, K - through the second transceiver with the input of a computer, an additional voltage sensor, the first and second input converters, the first and second comparators, the third transceiver, through which the output of port G of the microcontroller is connected to the input of a digital indicator, the outputs of the current and voltage sensors are connected respectively through the first and second input converters with ports A and C of the microcontroller, non-inverting inputs of the first and second comparators are connected respectively to the outputs of the current sensor and the voltage sensor of the network, the inverting inputs of the first and second comparators are connected to the common bus of the recorder, and the outputs are connected respectively to ports B and D of the microcontroller; the first and second input converters are identical, in particular, the first input converter contains a half-wave precision amplifier and a buffer scale amplifier, the input of which is connected to the input of the first input converter, and the output through a half-wave precision amplifier is connected to the output of the first input converter.

Significant differences of the proposed registrar are the introduction of additional elements (network voltage sensor, first and second input converters, first and second comparators, third transceiver), as well as the organization of its new structure and the introduction of new connections between the elements. The combination of elements and the relationships between them provide a positive effect - expanding the functionality of the device due to the possibility of continuous monitoring and recording the average values of power losses, argument φ, network voltage and load current.

The recorder circuit is shown in figure 1; figure 2 presents one of the possible options for implementing the input converter circuit.

The recorder circuit (Fig. 1) contains a current sensor (DT) 1, a network voltage sensor (DN) 2, the first 3 and second 4 input converters (VP), a microcontroller (MK) 5, an ambient temperature sensor (DTOS) 6, a sensor 7 conductor temperature (DTP), 8 rectangular pulse generator (GUI), first 9 and second 10 comparators, third 11, first 12 and second 13 transceivers, digital indicator 14, read-only memory (ROM) 15, computer 16. Current sensor outputs 1 and voltage 2 are connected respectively through the first 3 and second 4 input converters ports A and C of the microcontroller 5, port E of which is connected to the output of the ambient temperature sensor 6, port F is connected to the output of the conductor temperature sensor 7, and the clock input is connected to the output of the rectangular pulse generator 8, non-inverting inputs of the first 9 and second comparators 10 are connected, respectively to the outputs of the current sensor 1 and sensor 2 of the mains voltage, the inverting inputs of the first 9 and second 10 comparators are connected to the common bus of the recorder, and the outputs are connected respectively to ports B and D of the microcontroller 5, the outputs The microcontroller’s ports are connected, respectively, G — through the third transceiver 11 with the input of the digital indicator 14, H — through the first transceiver 12 with the input of the permanent storage device 15, K — through the second transceiver 13 with the input of the computer 16.

The first 3 and second 4 input converters have identical circuits, in particular, the first input converter 3 (Fig. 2) contains a half-wave precision amplifier (DPU) 17 and a buffer scale amplifier (BMU) 18, the input of which is connected to the input of the input converter 3, and the output through a half-wave precision amplifier 17 is connected to the output of the input Converter 4.

The schemes of the buffer scale amplifier 18 and the half-wave precision amplifier 17 are well known, in particular, the circuits described in [4, 5] and shown in Figures 1.3 and 2.49 [4], 13.7, and 52.15 [5] can be used as their implementations.

The registrar (figure 1) works as follows.

The output voltage of DT 1, proportional to the load current I (t), is fed through the first input converter 3 to the input of port A of the microcontroller 5.

The current sensor 1 may, in particular, be made on a measuring shunt included in the secondary circuit of the measuring current transformer; it provides a low level output signal (nominal value 75 mV). To match the signal level of DT 1 with the operating range of the analog-to-digital converter (ADC) built into MK 5, the VP 3 uses a buffer scale amplifier 18 (Fig. 2), which has a large input impedance and a large gain of 15-80 (selectable depending on modifications used MK 5). The VP 3 also uses a half-wave precision amplifier 17 to convert the bipolar sinusoidal signal DT 1 to unipolar.

The voltage sensor 2 can, in particular, be made on a measuring low-voltage step-down transformer (whose rated primary voltage is 100-220 V), connected to the secondary winding of a high-voltage measuring transformer (whose rated primary voltage is 6 -220 kV) or connected directly to 220 V network (when monitoring parameters in a low-voltage network); it provides an output signal of a level of several volts (the signal level depends on the standard parameters of the used low-voltage step-down transformer and the voltage level of the controlled network). To match the signal level DN 2 with the operating range of the built-in ADC in the MK 5 ADC in VP 4 is used BMU 18 (figure 2), having a large input impedance and a small gain of 0.5-5.

The control program with a sufficiently high speed alternately connects the output signals of the sensors 1 - 2 to the input of the ADC MK 5 in such a way as to obtain digital codes of the load current and network voltage 50-100 times per period. These codes are squared, and the sum of the squares accumulate in two cells for 1 min.

As you know, power losses in current-carrying elements (FC) are determined by the formula

$$\Delta \text{P}={\text{I}}^{\text{2}}\text{R}\text{,}\text{(one)}$$

where I (t) - time-varying load current flowing along the FC;

R is the active resistance of the fuel cell.

In simplified calculations, the resistance R is assumed to be constant over time and equal to the resistance R ₀ at an ambient temperature of Θ ₀ = 20 ° C or resistance at another fixed temperature.

The exact value of the resistance R as a function of temperature Θ _TE FC is determined by the formula

где α - температурный коэффициент сопротивления ТЭ; имеет значение для меди α_м=0,0041°C^-1, алюминия α_а=0,0044°C^-1, стали α_ст=0,006°C^-1.

where α is the temperature coefficient of resistance of TE; it matters for copper α _m = 0.0041 ° C ^-1 , aluminum α _a = 0.0044 ° C ^-1 , steel α _article = 0.006 ° C ^-1 .

If there is access to the fuel cell, its temperature Θ is determined using the temperature sensor 7 of the connection conductor, the resistance R of the conductor is calculated in MK 5 by the formula (2), and the loss value ΔР is determined by the formula (1).

The argument φ is calculated as follows.

When the zero level is crossed by a rising sinusoid of voltage, the comparator 10 is triggered at the output of DN 2 - a single voltage appears at its output, which affects the interrupt input of port D of the microcontroller 5.

At the same time, the MK 5 control program block starts working, resetting the contents of the T1 timer built into MK 5. After zeroing, timer T1 continues to count the input pulses that follow with a GUI frequency of 8 (for example, 1 MHz).

After the end of the time interval, the duration of which corresponds to the angle φ, the comparator 9 is triggered (at the moment of crossing the zero level with an increasing current sinusoid at the output of DT 1) - a unit voltage appears on its output, affecting the input of port B of the microcontroller 5, which is the input of the timer T1 capture. The content n (for example, 1000) of timer T1 is used to calculate the argument φ according to the formula

$$\varphi =\frac{360\cdot n}{n_T}=\frac{360\cdot 1000}{20000}={\mathrm{eighteen}}^{\circ },\left(3\right)$$

where m = 20000 is the number of pulses counted by the timer T1 during the period of the mains voltage at the frequency of the PTI 8f _T = 1 MHz. Management of the registrar is as follows.

At the same time intervals ΔT = 1 min, the transceiver 11 from the output of port G MK 5 in the DI 14 records the average current per minute of the load current I _1min , mains voltage U _1min , argument φ _1min and power losses ΔP _1min , which are subsequently displayed on a digital indicator 14, continuously updated every minute.

The transceiver 12 once per hour places in the next cells of the ROM 15: date; hour; values of load current I _{1 hour} , network voltage U _{1 hour} , argument φ _{1 hour} , power loss ΔP _{1 hour} (numerically coinciding with the loss of electricity for this hour), etc.

In the event that there is no access to the connection conductor, (for example, to the cable conductors on which the accident was not installed when laying the cable), the ambient temperature Θ _okr is measured once a minute by sensor 6, and the temperature of the conductor Θ is determined from the differential heating equation according to the following formula [6]

$$\tau \cdot \frac{d\Theta }{dt}+\Theta =K_R\cdot \left({\Theta }_{n\mathrm{about}m}-{\Theta }_0\right)\cdot \left[\frac{I_i^2}{I_{n\mathrm{about}m}^2}\right]+{\Theta }_{\mathrm{about}\mathrm{to}R},\left(\mathrm{four}\right)$$

- коэффициент изменения сопротивления проводника в функции от температуры;Where $$K_R\Theta =\frac{\mathrm{one}}{\mathrm{one}+\alpha \left({\Theta }_{n\mathrm{about}m}-{\Theta }_0\right)}[\mathrm{one}+\alpha \left(\Theta -{\Theta }_0\right)$$

- coefficient of variation of the resistance of the conductor as a function of temperature;

Θ _nom - nominal long-term permissible temperature of the conductor;

I _nom - rated current of the conductor;

I is the rms value of the load current.

The advantage of the invention in comparison with the known analogues is its wider functionality. The recorder circuit is focused on the use of a modern microelectronic basis - microcontrollers.

Information sources

1. RF patent 2380715, IPC G06F 17/18, 2008.

2. Osipov D.S. Accounting for heating of live parts in the calculations of power and electricity losses in non-sinusoidal modes of power supply systems: Abstract. dis ... cand. tech. sciences. - Omsk, 2005.

3. RF patent 2449356, IPC G06F 17/18, 2012, 5 independent claim (prototype).

4. The use of integrated circuits: a practical guide: V. 2 book: Per. from English / P. Bradshaw, S. Ghosh, X. Aldridge and others; Ed. A. Williams. - M.: Mir, 1987: Prince. 1 .-- 432 s.

5. Count R. Electronic circuits: 1300 examples: Per. from English - M .: Mir, 1989 .-- 688 p.

6. Gudzovskaya V.A., Ermakov V.F., Balykin E.S., Zaitseva I.V. A mathematical model of the process of changing the heating temperature of a conductor // Izv. universities. Electromechanics. - 2012. - No. 2. - S. 42 -43.

Claims (2)

1. A microprocessor data logger for conducting an energy audit, comprising a current sensor, an ambient temperature sensor, a conductor temperature sensor, a rectangular pulse generator, a digital indicator, the first and second transceivers, read-only memory, a computer, a microcontroller, port E of which is connected to the output of the temperature sensor environment, port F is connected to the output of the conductor temperature sensor, and the clock input is connected to the output of the rectangular pulse generator, the outputs of the micro the scooters are connected respectively H - through the first transceiver with the input of the read-only memory device, K - through the second transceiver with the input of the computer, characterized in that the mains voltage sensor, the first and second input converters, the first and second comparators, the third transceiver are additionally inserted into it which the output of port G of the microcontroller is connected to the input of a digital indicator, the outputs of the current and voltage sensors are connected respectively through the first and second input converters to the ports and A and C of the microcontroller, the non-inverting inputs of the first and second comparators are connected respectively to the outputs of the current sensor and the voltage sensor of the network, the inverting inputs of the first and second comparators are connected to the common bus of the recorder, and the outputs are connected respectively to the ports B and D of the microcontroller. 2. The registrar according to claim 1, characterized in that the first and second input converters are identical, in particular, the first input converter contains a half-wave precision amplifier and a buffer scale amplifier, the input of which is connected to the input of the first input converter, and the output is connected through a half-wave precision amplifier with the output of the first input converter.

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