CN212410745U - Excitation source of transformer substation grounding grid positioning device - Google Patents

Abstract

The utility model relates to a transformer substation grounding grid positioning device excitation source, which comprises a microcontroller, a signal conditioning module connected with the microcontroller, and a power amplification module connected with the signal conditioning module, wherein the power amplification module is connected with the microcontroller; the microcontroller is connected with the voltage reduction circuit module, the voltage reduction circuit module is respectively connected with the power amplification module and the signal conditioning module, and the voltage reduction circuit module is further connected with the power supply. The utility model discloses have the area that satisfies the site survey requirement and carry the ability, the amplitude of having guaranteed simultaneously through accurate power resistance is 1A's alternating current constant current source output. The utility model discloses satisfy the measurement requirement to have advantages such as the SNR is low, the wave form effect is better.

Description

Excitation source of transformer substation grounding grid positioning device

Technical Field

The utility model relates to an excitation source, especially a transformer substation's ground net positioner excitation source.

Background

The existing transformer substation has huge base number of reserved quantity and longer operation life, so the research on the grounding grid conductor corrosion diagnosis of the old transformer substation is very important. The traditional ground grid sampling excavation detection is heavy in workload, and meanwhile, the sampling detection result has great blindness and randomness. Therefore, accurate and lightweight diagnosis of corrosion of the ground net is not only efficient but also economical.

The method for diagnosing the grounding grid fault is basically based on the following principle: electric network principle, electromagnetic field principle, transient electromagnetic method principle, electrochemical analysis method, ultrasonic detection method and the like. The transformer substation fault positioning device produced based on the electromagnetic field principle method has direct diagnosis results, does not need power failure excavation, and has small normal operation to a power system, so the application is wide. But this method requires very high excitation sources.

SUMMERY OF THE UTILITY MODEL

In order to solve the technical problem, a set of sinusoidal alternating current system is designed as an excitation source of an induction magnetic field according to the requirement of measuring the position of a transformer substation grounding grid conductor by a magnetic field method.

The technical scheme of the utility model is specifically as follows:

a transformer substation grounding grid positioning device excitation source comprises a microcontroller, a signal conditioning module connected with the microcontroller, and a power amplification module connected with the signal conditioning module, wherein the power amplification module is connected with the microcontroller; the microcontroller is connected with the voltage reduction circuit module, the voltage reduction circuit module is respectively connected with the power amplification module and the signal conditioning module, and the voltage reduction circuit module is further connected with the power supply.

Further, the microcontroller is also connected with an upper computer.

Further, the microcontroller comprises an STM32F373RC micro-control chip, and generates an alternating current signal with the frequency of 1 kHz.

Furthermore, the signal conditioning module comprises an ADA4841-2YRZ operational amplifier chip, the DAC OUT end of the ADA4841-2YRZ operational amplifier chip is connected with the DAC pin of the STM32F373RC micro-control chip, and the VOUT end is connected with the power amplification module.

Further, the power amplification module comprises an OPA548T power amplification chip, the output end of the OPA548T power amplification chip is sequentially connected with a power resistor and a reference resistor, and a constant current source with amplitude of 1A and frequency of 1kHZ is output.

Furthermore, the reference resistor and the power resistor are 0.1 omega, and the reference resistor is connected with the output end of the power amplification module.

Further, the output constant current source of the power amplification module is input into the microcontroller through the A/D converter.

Compared with the prior art, the beneficial effects of the utility model are as follows:

the utility model discloses utilize power amplifier circuit to carry out power amplification output with 1kHZ sinusoidal signal of DAC, DMA and the timer cooperation output of STM32F373RC chip for output voltage has satisfied the impedance matching requirement of power amplifier with the ground net conductor load, has the area load ability that satisfies the field measurement requirement, and the amplitude of having guaranteed simultaneously through delicate power resistance is 1A's alternating current constant current source output. The utility model discloses satisfy the measurement requirement to have advantages such as the SNR is low, the wave form effect is better.

Drawings

Fig. 1 is a system block diagram of an excitation source of the present invention;

fig. 2 is a schematic circuit diagram of the signal conditioning module of the present invention;

fig. 3 is a schematic circuit diagram of the power amplification module of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some examples of the present invention, not all examples. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without any creative effort belong to the protection scope of the present invention.

As shown in fig. 1, the excitation source of the transformer substation grounding grid positioning device in this embodiment includes a microcontroller, a signal conditioning module connected to the microcontroller, and a power amplification module connected to the signal conditioning module, where the power amplification module is connected to the microcontroller; the microcontroller is connected with the voltage reduction circuit module, the voltage reduction circuit module is respectively connected with the power amplification module and the signal conditioning module, and the voltage reduction circuit module is further connected with the power supply. The microcontroller is also connected with an upper computer through RS 485. The output constant current source of the power amplification module is input into the microcontroller through the A/D converter.

The sine alternating current excitation current source is one of core parts of the substation grounding grid fault positioning device. The interference intensity of the field electromagnetic environment is in a mu T level, the intensity of the magnetic field to be detected is only in an nT level, and the intensity difference between the two levels is an order of magnitude, which brings great difficulty to the detection of the target magnetic field. Therefore, in order to better detect the induced magnetic field signal, the frequency of the ac excitation source needs to maximally avoid the magnetic field noise of the substation, i.e. the power frequency and its odd harmonic interference, and therefore the frequency of the excitation source is required to be higher. Meanwhile, after the frequency of the excitation power supply with the same amplitude exceeds 1kHZ, the amplitude of the induction magnetic field of the excitation power supply is sharply reduced, so that the measurement difficulty is greatly increased. In view of the above analysis, in order to increase the signal-to-noise ratio and facilitate the implementation of the hardware circuit, the present embodiment uses 1kHZ as the frequency of the ac excitation source, and the amplitude is 1A.

As shown in fig. 2, in order to increase the endurance time of the ac excitation source and facilitate the design, the present embodiment adopts a dual power supply manner, and adopts two general-purpose lithium batteries with a voltage of 14.4V and a capacity of 3500mAh as a device power supply, and the two batteries are connected in parallel to operate, so as to respectively provide a positive voltage and a negative voltage for the device. Sinusoidal alternating voltage output by a chip pin is subjected to signal conditioning and then input to a power amplification circuit, alternating excitation current with specific frequency is output through a precision reference resistor, and output of the output current and data acquisition work are controlled in a mode of combining a software switch and a hardware switch.

The microcontroller of the present embodiment includes an STM32F373RC micro-control chip, which generates an ac signal with a frequency of 1 kHz. The sinusoidal signal source of the excitation source is from a DAC (Digital to analog converter) pin of an STM32F373RC micro-control chip, and STM32F373RC is a microcontroller manufactured by ARM company based on a Cortex-M4 core, the bus frequency of the chip is 72MHz, and the chip is provided with 3 DAC pins with 12 bits and 17 timers with different bit lengths. In the present embodiment, a DAC pin, a DMA (Direct Memory Access) and a timer are used to generate an ac signal with a frequency of 1 kHz. In the program, 526 pieces of data capable of forming sine waves are stored in a chip static memory, the content of the related memory can be rapidly read and used by utilizing a DMA channel on the premise of not occupying the core resource of the chip, then the data is directly transmitted to a module, and the sine wave signal with the appointed amplitude can be obtained at an output pin through digital-to-analog conversion. Since the transmission speed is very fast, the output analog quantity changes very fast and cannot be used normally, so that a Timer is required. The DAC is configured to be triggered by the timer when the DAC module is initialized, namely, when the timer overflows, the DAC is triggered to generate an analog signal, and the specified frequency signal can be generated by changing the setting of the timer. The conventional circuit module can generate an alternating current signal (containing impurities and harmonics) having a frequency of 1 kHz.

Each cycle of sine wave is composed of 526 data, the frequency of a synthesized signal is 1kHz, a DAC (digital-to-analog converter) is controlled by a timer to output, the frequency division is 8, the counting interval is 14, and the frequency of a corresponding chip bus is 72MHz, so that the timer is set as follows:

by directly changing the setting of the timer, the frequency of the required sinusoidal signal can be conveniently customized.

An ADC (Analog to digital converter) pin is configured to collect an output signal and a power supply voltage signal, 456 points are set for collecting one cycle, 2736 data are planned to be collected in 6 cycles, an effective value of a measurement signal is obtained by taking 1.25V as a central line, and positive and negative power supply voltages of a power amplifier and voltage signals of a lithium battery are collected at the same time.

As shown in fig. 2, the signal conditioning module includes an ADA4841-2YRZ operational amplifier chip, a DAC OUT terminal of the ADA4841-2YRZ operational amplifier chip is connected to a DAC pin of an STM32F373RC micro-control chip, and a VOUT terminal is connected to the power amplification module. A1 kHz sinusoidal voltage signal output through a DAC pin needs to be conditioned, and a band-pass filter circuit formed by an ADA4841-2YRZ operational amplifier chip is used for carrying out filtering processing on an original signal.

In fig. 2, the DAC OUT terminal is connected to the anode of the ADA4841-2YRZ op-amp chip through a resistor R2 and a capacitor C1, the cathode is grounded through a resistor R5, one end of the resistor R3 is grounded, the other end is connected between the capacitor C1 and the anode, one end of the resistor R4 is arranged between the resistor R5 and the cathode, the other end is connected to the resistor R1, and the other end of the resistor R1 is grounded through a capacitor C2. The output end of the ADA4841-2YRZ operational amplifier chip is a Vout end.

As shown in fig. 3, the power amplification module of this embodiment includes an OPA548T power amplification chip, an output terminal of the OPA548T power amplification chip is sequentially connected to a power resistor R4 and a reference resistor R5, and a constant current source with an amplitude of 1A and a frequency of 1kHZ is output. The reference resistor and the power resistor are 0.1 omega, and the reference resistor is connected with the output end JP1 of the power amplification module.

The OPA548T power amplification chip is a voltage-controlled power amplification chip produced by Texas instruments and can be supplied with power by a single power supply of 8-60V or power by double power supplies of +/-4V- +/-60V, and can be flexibly selected, wherein the power supply is supplied with power by +/-7.4V after being reduced by a lithium battery. The switching speed of the OPA548T can reach 10V/mus, and the internal circuit thereof has a self-protection function, and can automatically disconnect the circuit and stop working under the condition of circuit overheating and current overload. Unlike the common power amplification chip which directly connects the power resistor in series with the output current channel, the OPA548T is indirectly connected with the output current channel, which makes the effective value of the output limiting current of the chip reach 5A at most and has strong loading capacity.

The OPA548T also has a pin enable control function, the input function of which can disconnect the output pole from the load, and can reduce the power consumption of the chip by reducing the quiescent current, and can also monitor the temperature of the chip through the output pin to determine whether the shutdown is needed.

OPA548T can operate in an environment of-40 ℃ to 85 ℃, with extremely low thermal resistance. Because the chip has larger current when in work and causes overlarge heat production, the chip adopts the industrial standard 7-pin staggered TO-220 package, radiating holes are reserved on the surface of the package, radiating fins can be installed TO assist in radiating, and the excitation source module can be ensured TO work stably and effectively for a long time when in field measurement of a transformer substation.

In fig. 3, pin 5 of OPA548T is connected to the first VCC, pins 3 and 4 are connected to VSS, pin 1 is connected to Vout terminal through resistor R3, pin 2 is connected to ground through resistor R6, pin 7 is connected to the second VCC through resistor R2, pin 6 is connected to power resistor R4 and reference resistor R5, reference resistor R5 is connected to one end of output terminal JP1, the other end of JP1 is connected to ground, resistor R7 is connected between resistor R6 and pin 2, and the other end is connected between pin 6 and resistor R4. The second VSS is provided between pin 6 and one end of R7 through diode D2, and then connected to the third VCC through diode D1. The diodes are each IN 4148W.

The power amplification module of this embodiment also includes an ADA4841-2YRZ operational amplifier chip, wherein the output terminal is disposed between the resistor R3 and the pin 1 through the resistor R1, the negative electrode is connected to the output terminal, the positive electrode is disposed between the power resistor R4 and the reference resistor R5, and the power source is terminated with a 5V power source.

The waveform of the excitation source is tested by using an MDO4034B-3 type mixed signal oscilloscope and taking a precision power resistor of 1 omega/10W as a load, and the excitation current output by the excitation source of the embodiment meets the requirement of load matching with a conductor of a grounding grid.

The above description is only a preferred embodiment of the present invention, and should not be taken as limiting the invention, and any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (7)

1. The utility model provides a transformer substation's ground net positioner excitation, its characterized in that: the device comprises a microcontroller, a signal conditioning module connected with the microcontroller, and a power amplification module connected with the signal conditioning module, wherein the power amplification module is connected with the microcontroller; the microcontroller is connected with the voltage reduction circuit module, the voltage reduction circuit module is respectively connected with the power amplification module and the signal conditioning module, and the voltage reduction circuit module is further connected with the power supply.

2. The substation grounding grid positioning device excitation source of claim 1, characterized in that: the microcontroller is also connected with an upper computer.

3. The substation grounding grid positioning device excitation source of claim 1, characterized in that: the microcontroller comprises an STM32F373RC micro-control chip and generates an alternating current signal with the frequency of 1 kHz.

4. The substation grounding grid positioning device excitation source of claim 3, characterized in that: the signal conditioning module comprises an ADA4841-2YRZ operational amplifier chip, the DAC OUT end of the ADA4841-2YRZ operational amplifier chip is connected with the DAC pin of the STM32F373RC micro-control chip, and the VOUT end is connected with the power amplification module.

5. The substation grounding grid positioning device excitation source of claim 1, characterized in that: the power amplification module comprises an OPA548T power amplification chip, the output end of the OPA548T power amplification chip is sequentially connected with a power resistor and a reference resistor, and a constant current source with the output amplitude of 1A and the frequency of 1kHZ is output.

6. The substation grounding grid positioning device excitation source of claim 5, characterized in that: the reference resistor and the power resistor are 0.1 omega, and the reference resistor is connected with the output end of the power amplification module.

7. The substation grounding grid positioning device excitation source of claim 5, characterized in that: the output constant current source of the power amplification module is input into the microcontroller through the A/D converter.

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