CN106404190A - Novel line temperature transmission device - Google Patents

Abstract

The invention discloses a novel line temperature transmission device, which is used to lead the current of a CT secondary winding to a heating resistance circuit when measuring the line temperature of a power transformer, including a current acquisition module for collecting the current of the CT secondary winding, a control circuit and Lead the output current to the AC constant current source circuit of the heating resistance circuit, wherein the control circuit includes a central processing unit and a liquid crystal display module, the AC constant current source circuit is connected to the central processing unit through a serial port communication circuit, and the current acquisition module is connected to the central processing unit , the liquid crystal display module is connected with the central processing unit. The present invention adopts the current collection sensor to collect the current of the secondary winding, the central processing unit processes the collected current data, and communicates with the AC constant current source circuit, thereby controlling the output current to achieve the output current of the AC constant current source circuit and the collected current data. The synchronous and consistent effect of the input current can reduce the risk of CT secondary winding open circuit and improve the stability of the transformer system.

Description

A New Line Temperature Transmitting Device

technical field

The invention relates to a line temperature transmission device, in particular to a line temperature transmission device for measuring the temperature of a secondary winding current during line temperature measurement of a power transformer.

Background technique

At present, the method of measuring the line temperature of the power transformer is mainly that the current of the secondary winding of the CT flows through the heating resistor to compensate the oil temperature, and the line temperature of the transformer is obtained after conversion. Since this measurement method connects resistors in series in the CT secondary winding circuit, and the environment around the converter transformer is relatively harsh, there is a risk of resistor burnout in long-term operation, causing the CT secondary winding to open and threatening the safety of the transformer. run. At present, the temperature measurement principle of windings at home and abroad is basically calculated by superimposing the oil temperature plus the current calculation temperature of the CT secondary winding. The schematic diagram is shown in Figure 1. It is mainly based on an oil temperature gauge, equipped with a current matcher and a heating element. The sensor of the thermometer - the temperature package is inserted into the oil hole on the top of the transformer oil tank. When the transformer load is zero, the reading of the winding thermometer is the temperature of the oil surface on the top layer of the transformer oil tank. When the transformer is loaded, the current proportional to the load taken out by the transformer current transformer is adjusted by the current matching device and flows through the electric heating element embedded in the bellows, and the electric heating element generates heat to further expand the gas in the bellows , the displacement of the meter elastic element increases. Therefore, after the transformer is loaded, the displacement of the elastic element is determined by both the oil temperature on the top layer of the transformer and the load current of the transformer. There is no relevant research on protecting the secondary circuit of CT from opening due to the melting of the heating element or the resistance of the current matching device.

Contents of the invention

Aiming at the deficiencies of the prior art, the present invention provides a novel line temperature transmission device as an optimization measure to prevent the open circuit of the secondary winding of the CT, and at the same time reduce the risk of the open circuit of the secondary winding of the CT.

In order to achieve the above object, the technical scheme that the present invention takes is:

A new type of line temperature transmission device, which is used to lead the CT secondary winding current to the heating resistor circuit when measuring the line temperature of a power transformer. The new line temperature transmission device includes: a current acquisition module for collecting the current of the CT secondary winding , the control circuit and the AC constant current source circuit to lead the output current to the heating resistance loop, the control circuit includes a central processing unit and a liquid crystal display module,

Wherein, the AC constant current source circuit is connected to the central processor through a serial port communication circuit, so as to transmit the data that the central processor controls and adjusts the input current of the AC constant current source circuit and the output current of the AC constant current source circuit to the central processor;

The current collection module is connected with the central processing unit, so that the central processing unit processes the current data collected by the current collection module;

The liquid crystal display module is connected with the central processing unit, and the current data collected by the current collection module and the output current data of the AC constant source circuit are displayed by the liquid crystal display module.

The liquid crystal display module is a TFTLCD module.

The current collection module includes a current collection sensor and a quantization module circuit, wherein the current collection sensor collects the secondary winding current and outputs it after being connected to the quantization module circuit.

The AC constant current source circuit includes a DC power supply module, a sine wave module, a waveform filter module, a constant current tracker, a power amplifier, a current sampling circuit and a microcontroller, wherein the DC power supply module is connected to the sine wave module, Output after waveform filter module, constant current tracker, power amplifier and current sampling circuit, the output terminal of described current sampling circuit is connected with described constant current tracker and microcontroller at the same time, and described microcontroller is connected with sine wave The module and the constant current tracker, the central processing unit are connected with the microcontroller through the serial port communication circuit.

The central processing unit is an STM32 chip, which is not expensive, has powerful performance, is easy to expand, and can improve the stability of the entire system, making the circuit simple, easy to integrate, and low maintenance cost.

The serial port communication circuit is an RS-232 serial port communication circuit.

The power supply DC power supply module is a switching power supply with multiple outputs. The finished switching power supply has multiple voltage outputs. The designed power utilization efficiency is high, the stability is good, and it has overvoltage and overcurrent protection. The switching power supply is used with a protective shell. More secure, easy to install applications, save development time and cost, and easy to use can greatly simplify the design complexity of hardware circuits.

Compared with prior art, the beneficial effect of the present invention is:

1. The present invention well solves the problem that the open circuit of the CT secondary winding of the power system threatens the safe operation of the transformer. When there is an open circuit of the CT secondary circuit, it will not cause harm, and the transformer continues to operate. Only the circuit of the novel line temperature transmission device of the present invention can be restored to the normal operation state only by separate maintenance. The failure consequences caused by a single component failure are greatly reduced, ensuring the stability of the system operation. When a single component fails, the component can be quickly replaced, reducing the maintenance work time and improving the maintenance work efficiency; because most of the circuit transformer line temperature measurement in the power grid uses the CT secondary winding current to flow through the heating resistor to compensate the oil temperature, the conversion Finally, the line temperature measurement mode of the transformer is obtained, so it can be widely promoted in the power grid to ensure the stability of the system operation.

2. The present invention adopts a non-contact current acquisition sensor to collect the current size of the CT secondary winding, uses the central processing unit to process the collected current data, and then communicates with the AC constant current source circuit through the serial port communication circuit, and the AC constant current source The circuit controls the size of the output current through the microcontroller, so as to achieve the effect that the output current of the AC constant current source circuit is synchronized with the collected input current, and the collected input current and the output of the AC constant current source circuit are displayed on the display The magnitude of the current is then used to lead the CT secondary winding current to the heating resistor circuit for temperature measurement, thereby reducing the risk of CT secondary winding open circuit and improving the stability of the transformer system. This system greatly reduces the accidents of the entire transformer system and reduces the burden on the maintenance team.

Description of drawings

Fig. 1 is the schematic diagram of the temperature measurement of the secondary winding of the prior art transformer;

Fig. 2 is a schematic diagram of the principle of the present invention;

Fig. 3 is a schematic diagram of the principle of the AC constant current source circuit of the present invention.

detailed description

The present invention will be further described below in combination with specific embodiments.

As shown in Figure 2, a new line temperature transmission device is used to draw the current of the CT secondary winding to the heating resistor circuit when measuring the line temperature of the power transformer. The new line temperature transmission device includes a current for collecting the CT secondary winding The data current collection module 1, the control circuit and the AC constant current source circuit 3, wherein the control circuit includes the current data outputted by the current collection module 1 for processing and controlling and adjusting the input current of the AC constant current source circuit through the serial port communication circuit The central processing unit 2 and the liquid crystal display module 4, the central processing unit 2 is connected with the liquid crystal display module 4, and the central processing unit 2 transmits the current data collected by the current acquisition module 1 and the output current of the AC constant source circuit 3 to the liquid crystal display module 4 , the liquid crystal display module 4 displays the current data collected by the current collection module 1 and the output current of the AC constant source circuit 3 .

The liquid crystal display module 4 is a TFTLCD module. The TFTLCD module performs well in terms of brightness, contrast, strong layering, bright colors, etc., and has a faster speed when transmitting large data, which is conducive to achieving better display effects. The TFTLCD module displays the collected secondary winding current and the output current of the AC constant source circuit 3, monitors the operation of the system at any time, can detect faults early, reduces accidents, and focuses on reducing the probability of power system faults.

The current acquisition module 1 includes a current acquisition sensor and a quantization module circuit, wherein the current acquisition sensor collects the secondary winding current and then connects to the quantization module circuit for output. The current acquisition sensor is different from the traditional way of collecting current data, and adopts a non-contact The current acquisition sensor acquisition does not affect the work of the line that needs to be measured, has the function of electrical isolation, and has the characteristics of high precision and safety without direct contact with high voltage. The current data collected by the current acquisition sensor is converted into 0-5V voltage by the quantization module circuit. The quantization module circuit has high accuracy and response speed, and the stability is very good. The existing temperature drift can be controlled by the micropotentiometer. calibration. As an embodiment, the quantization module circuit can adopt the SX-AC-A series, which is an AC current precision quantization module, and there are 4 kinds of ranges to choose from, namely 5A, 10A, 20A, and 50A. In the present invention, the AC current precision quantization The module can choose the SX-AC-A05 module with a range of 5A.

As shown in Figure 3, the AC constant current source circuit 3 includes a DC power supply module, a sine wave module 6, a waveform filter module 7, a constant current tracker 8, a power amplifier 9, a current sampling circuit 10 and a microcontroller 11, Wherein the power supply DC power supply module is sequentially connected to the sine wave module 6, the waveform filter module 7, the constant current tracker 8, the power amplifier 9 and the current sampling circuit 10, and then output, the current sampling circuit 10 collects the output current, and the current sampling circuit The output terminal of 10 is connected to the constant current tracker 8 and microcontroller 11 at the same time, and the output current data collected by the current sampling circuit 10 is negatively fed back to the constant current tracker 8 to achieve the purpose of constant output current. The central processing unit 2 is connected to the microcontroller 11 through a serial port communication circuit, and the microcontroller 11 controls the output current through the sine wave module 6 and the constant current tracker 8, so as to achieve the output current of the AC constant current source circuit 3 and the collected two The secondary winding current is synchronized and consistent, and at the same time, the risk of CT secondary winding open circuit is reduced.

The described power supply DC power supply module is a switching power supply 5 with multiple outputs. The finished switching power supply 5 has multiple voltage outputs. The protective shell is safer to use, easy to install and save development time and cost, and simple to use can greatly simplify the design complexity of hardware circuits.

As an example, the switching power supply 5 is a constant voltage source that outputs a DC voltage of 14v, which is converted into a standard sine wave through the oscillating wave module 6. Since the generated sine wave will be mixed with harmonics, it needs to pass through the waveform filter module 7. Useless waveforms are removed, and the waveforms of the required frequency and amplitude are left, and then the signal is amplified by the power amplifier 9, so that the output can have a load capacity. The current sampling loop 10 collects the magnitude of the output current and transmits it to the constant current tracker 8. According to the principle of automatic control, the output current is adjusted in real time to achieve the effect of constant output current.

The central processing unit is an STM32 chip, which is not expensive, has powerful performance, is easy to expand, and can improve the stability of the entire system, making the circuit simple, easy to integrate, and low maintenance cost.

The serial port communication circuit is an RS-232 serial port communication circuit. The communication requirement of the present invention is full-duplex transmission, the amount of data is not large, the speed requirement is not high, and the distance between the two modules is also very close. RS-232 is adopted. 232 serial port communication circuit meets the requirements of the present invention and can facilitate future expansion.

The current acquisition sensor accurately collects data on the secondary winding current, the STM32 chip processes the collected data and communicates with the microcontroller 11 in the AC constant current source circuit 3 through the serial port communication circuit, and adjusts the AC through the microcontroller 11 The magnitude of the output current of the constant current source circuit 3, the output current of the AC constant current source circuit 3 is taken as the temperature measurement of the CT secondary winding current of the power transformer, even when the secondary circuit is open, it is not affected.

The following methods can be used to verify the accuracy of the system results. Prepare an AC electrical appliance that can be fine-tuned such as a large light bulb. First, connect the circuit to be tested to the multimeter and set the gear to the measurement current gear. Connect the output terminal of 3 to the multimeter, and switch to the measurement voltage gear. After everything is ready, turn on the power, observe the values of the two multimeters, judge whether they meet the accuracy requirements, adjust the output size of the test circuit again, and then observe the values of the two multimeters again. Whether the reading meets the requirements, if the accuracy cannot meet the expected effect, adjust the resistance value of the quantization resistor to adjust the accuracy to meet the design requirements. The test accuracy comparison table after debugging is shown in Table 1.

Table 1: Test Accuracy Comparison Table

The above detailed description is a specific description of the feasible embodiment of the present invention. This embodiment is not used to limit the patent scope of the present invention. Any equivalent implementation or change that does not deviate from the present invention should be included in the patent scope of this case. middle.

Claims (7)

1. A new type of line temperature transmission device, which is used to draw the CT secondary winding current to the heating resistor circuit when measuring the line temperature of a power transformer. It is characterized in that the new line temperature transmission device includes: used to collect CT secondary winding current The current acquisition module (1) of the winding current, the control circuit and the AC constant current source circuit (3) to lead the output current to the heating resistance circuit, the control circuit includes a central processing unit (2) and a liquid crystal display module (4), wherein : The AC constant current source circuit (3) is connected with the central processing unit (2) through a serial port communication circuit, so that the central processing unit (2) controls and adjusts the input current of the AC constant current source circuit (3) and the AC constant current source circuit (3) ) data transmission of the output current to the central processing unit (2); The current acquisition module (1) is connected to the central processing unit (2), and the central processing unit (2) processes the current data collected by the current acquisition module (1); The liquid crystal display module (4) is connected with the central processing unit (2), and the current data collected by the current collection module (1) and the output current data of the AC constant source circuit (3) are displayed by the liquid crystal display module (4). 2. A novel line temperature transmitter according to claim 1, characterized in that said liquid crystal display module (4) is a TFTLCD module. 3. A novel line temperature transmitter according to claim 1, characterized in that, the current acquisition module (1) comprises a current acquisition sensor and a quantization module circuit, wherein the current acquisition sensor collects the secondary winding current Output after connecting the quantization module circuit. 4. A new type of line temperature transmitter according to claim 1, characterized in that the AC constant current source circuit (3) includes a DC power supply module, a sine wave module (6), and a waveform filter module (7), constant current tracker (8), power amplifier (9), current sampling circuit (10) and microcontroller (11), wherein the DC power supply module for power supply is connected with sine wave module (6), waveform filter module ( 7), the constant current tracker (8), the power amplifier (9) and the current sampling circuit (10) output current to the heating resistance loop, and the output terminal of the current sampling circuit (10) is connected to the constant current tracking Device (8) and microcontroller (11), described microcontroller (11) connects sine wave module (6) and constant current tracker (8), central processing unit (2) communicates with microcontroller through serial port Device (11) is connected. 5. A novel line temperature transmitter according to claim 1, characterized in that said central processing unit is an STM32 chip. 6. A novel line temperature transmitter according to claim 1, characterized in that the serial communication circuit is an RS-232 serial communication circuit. 7. A novel line temperature transmitter according to claim 4, characterized in that said DC power supply module is a switching power supply (5) with multiple outputs.