CN203894344U - Power cable line load and temperature monitoring device based on CT - Google Patents

Abstract

A CT-based power cable line load and temperature monitoring device, characterized in that it includes cables, zero-sequence current transformers, phase current transformers, I/V conversion protection circuits, filter circuits, amplifier circuits, voltage boost circuits, processing A temperature sensor, a sending and receiving unit, wherein, the cable is integrated with a three-phase power line and a grounding line, the three-phase power line is connected with a phase current transformer for collecting load current, and the grounding line is connected with a measuring The zero-sequence current transformer of the ground current, the temperature sensor is in contact with the skin of the cable, the zero-sequence current transformer and the phase current transformer convert the current signal to the I/V conversion protection circuit, and the I/V The conversion protection circuit converts the current signal into a voltage signal and performs clamp protection, and then is filtered by the filter circuit and connected to the processor by the voltage boost circuit.

Description

CT-Based Power Cable Line Load and Temperature Monitoring Device

technical field

The utility model relates to the monitoring of grounding line faults, line loads, and cable skin temperature of cables in electric power industry cable systems, so as to realize early warning before line failures and ensure rapid troubleshooting of faults. Device) power cable line load and temperature monitoring device. the

Background technique

Power systems usually use fault indicators to realize cable line grounding and short-circuit fault detection. However, this kind of monitoring is generally carried out independently of load current monitoring and fault temperature monitoring, resulting in redundancy of the monitoring system. At the same time, there are the following problems: 1) , The measurement accuracy is not high, and the accuracy of fault detection is low; 2) The fault indicator is affected by power consumption, so it cannot use a higher sampling frequency, and can only be used by an analog circuit to judge the fault. The limit value and time limit of the fault alarm cannot Set according to the actual situation on site; 3) Since the fault detection circuit and the load current monitoring circuit are separated, the magnitude of the fault current cannot be monitored, and the fault current cannot be sent when a fault occurs; 4), limited by power consumption, The fault indicator cannot frequently upload the load current, and the real-time performance of load monitoring is poor. These problems have seriously affected the field application effect of the fault indicator, limiting the further development of this product, and the fault indicator will only give an alarm when a fault occurs, and the field equipment may have been damaged. Temperature, line temperature, you can achieve early warning, early elimination of hidden dangers. At the same time, when a fault occurs, the accuracy of the fault alarm will be greatly improved by referring to the fault current and temperature of the fault phase. the

The utility model has carried out beneficial improvement in order to overcome above-mentioned defect. the

Utility model content

The purpose of the utility model is to solve the above-mentioned deficiencies in the prior art, and provide a CT-based power cable line load and temperature monitoring device that combines the two functions of temperature measurement and current measurement into one. the

In order to achieve the above object, the utility model adopts the following technical solutions:

A CT-based power cable line load and temperature monitoring device, which is special in that it includes cables, zero-sequence current transformers, phase current transformers, I/V conversion protection circuits, filter circuits, amplifier circuits, and voltage boost circuits , a processor, a temperature sensor, and a sending and receiving unit, wherein the cable is integrated with a three-phase power line and a grounding line, the three-phase power line is connected to a phase current transformer for collecting load current, and the grounding line is connected to There is a zero-sequence current transformer for measuring the ground current, the temperature sensor is in contact with the skin of the cable for measuring the skin temperature of the cable, the temperature sensor transmits the measured signal to the processor, the zero-sequence current transformer and The phase current transformer converts the current signal into a ratio and connects it to the I/V conversion protection circuit. The I/V conversion protection circuit converts the current signal into a voltage signal and performs clamping protection, and then is filtered by the filter circuit, amplified by the amplifier circuit, and the voltage The boost circuit boosts the voltage signal and connects it to the processor, the zero-sequence current transformer, phase current transformer, I/V conversion protection circuit, filter circuit, amplifier circuit, voltage boost circuit, processor, temperature sensor, and sending and receiving unit Installed in the control box next to the cable;

Further, the secondary side of the zero-sequence current transformer and/or phase current transformer is connected to the small current transformer CT1 of the I/V conversion protection circuit, and is converted into a voltage signal through the sampling resistor R1, and the I/V The rear end of the V conversion protection circuit is provided with double diodes for voltage clamping and protection, and the sampling resistor R1 is 300 ohms;

Further, the filter circuit adopts a second-order voltage-controlled low-pass active filter circuit, and the filter circuit includes a double operational amplifier circuit LM2904M chip, and the 2-pin of the LM2904M chip is connected to a 1K ohm R1, and the 3-pin is connected to There is a 1K ohm resistor R3 and a capacitor C5, the capacitor C5 is 0.022 μF, the resistor R3 is connected in series with a resistor R2, and the resistor R2 is 10K ohm;

Further, the amplifying circuit is an addition proportional amplifying circuit with 8 times amplification, the signal access end of the amplifying circuit is provided with a 10K ohm resistor R6, the signal is amplified by the amplifying circuit and then connected to the voltage boosting circuit, and the voltage boosting The front end of the circuit is also connected with an adding circuit, which is used to convert the AC signal output by the amplifier circuit into a DC signal that can be directly received by the processor;

Further, the processor adopts a PIC16F887 single-chip microcomputer, and the single-chip microcomputer is also connected with a power conversion module and a sending and receiving unit, wherein the sending and receiving unit is an RS485 communication module of full-duplex general synchronous/asynchronous serial transceiver, The temperature sensor is an Intel MF52103F temperature sensor, and the processor uploads the collected signal to the upper-level device through the communication module. the

Beneficial effects of the utility model: the load and temperature monitoring system designed in the present invention adopts distributed sampling and distributed processing to judge line faults and monitor the load and temperature of the lines, which is an upgrade to existing fault indicator products , has the following beneficial effects: a control box is added to the CT, and the outgoing line of the CT is short-connected inside the control box, so that the CT will not open circuit; since the line fault is directly sampled by the hardware, it can be monitored in real time according to the site situation; traditional The impact threshold of the hardware analog circuit to judge the line fault has high requirements on the resistance capacitor device and the materials used in the circuit, and it cannot be calibrated and adjusted; the fault current in the design is measured by hardware sampling, which can only be calibrated, and the accuracy of fault judgment is high. ; Through the monitoring of temperature and load, the measurement of cable skin temperature can know the situation before the fault in advance, so as to realize the early warning before the accident; when judging the fault, the line temperature and current can be used as one of the effective criteria. Improve the accuracy of fault judgment. the

Description of drawings

Fig. 1 is the CT connection schematic diagram of the utility model embodiment;

Fig. 2 is the structural functional module schematic diagram of the utility model embodiment;

Fig. 3 is the schematic diagram of the I/V conversion protection circuit of the utility model embodiment;

Fig. 4 is the schematic diagram of the filter circuit of the utility model embodiment;

Fig. 5 is the schematic diagram of the amplification circuit of the utility model embodiment;

Fig. 6 is a schematic diagram of the voltage boosting circuit of the embodiment of the present invention. the

Detailed ways

Below in conjunction with accompanying drawing and embodiment the utility model is described further. the

The embodiment of the present utility model is shown in Fig. 1-6 with reference to, wherein, the whole of this measuring device is shown in Fig. 1, 2, comprises cable, zero-sequence current transformer, phase current transformer, I/V conversion protection circuit, filter circuit, amplifying circuit, voltage boosting circuit, processor, temperature sensor, and sending and receiving unit, wherein, a three-phase power line and a grounding line are integrated in the cable, and the three-phase power line is connected with a phase current collecting load current Transformer, the grounding line is connected with a zero-sequence current transformer for measuring the grounding current, the temperature sensor is in contact with the skin of the cable, and is used to measure the skin temperature of the cable, and the temperature sensor transmits the measured signal to the processing The zero-sequence current transformer and the phase current transformer transform the current signal and connect it to the I/V conversion protection circuit, and the I/V conversion protection circuit converts the current signal into a voltage signal and performs clamping protection, and then The zero-sequence current transformer, phase current transformer, I/V conversion protection circuit, filter circuit, amplifier circuit, and voltage boost circuit are connected to the processor after being filtered by the filter circuit, amplified by the amplifier circuit, and boosted by the voltage boost circuit. , processor, temperature sensor, and sending and receiving unit are installed in the control box next to the cable. Use high-precision openings to measure CT, and add functional modules to the CT. The functional modules include protective circuits for further rationing and I/V conversion after CT rationing, filtering circuits, amplifier circuits, voltage boosting circuits, and temperature acquisition circuits. , CPU calculation processing circuit, 485 communication circuit and other functional modules. After the collected line current is transformed, filtered, amplified and voltage boosted, it is AD sampled by the processor (sampling frequency is 10kHz), digital filtering and other operations are performed in the processor, and sent to the previous one through the 485 bus. At the same time, because the fault is sampled through hardware, the product can receive the situation of the upper-level device, and set the fault judgment according to the actual needs of the site. Among them, the temperature information of the cable is collected through the AD sampling temperature sensor. the

The I/V conversion protection circuit is shown in Figure 3. The main function is to sense the current (including normal load current and fault current) after the first large CT transformation ratio through the small CT on the circuit board, and convert it into Voltage signals, and signals that exceed the capacity of the subsequent circuit are clamped and protected. The detailed structure of the circuit components is shown in Figure 3. the

The detailed structure of the filter circuit is shown in Figure 4. The second-order voltage-controlled low-pass active filter circuit is used. The main function is to filter out the sensed high-order harmonic signals to ensure that the sampling of the subsequent stage will not be affected by high-order harmonics. The filter circuit includes a dual operational amplifier circuit LM2904M chip, the 2 pins of the LM2904M chip are connected to a 1K ohm R1, the 3 pins are connected to a 1K ohm resistor R3 and a capacitor C5, and the capacitor C5 is 0.022 μF, the resistor R3 is connected in series with a resistor R2, the resistor R2 is 10K ohms, and the resistor R5 connected to pin 1 is 1K ohms. the

The detailed structure of the amplifying circuit is shown in Figure 5, and the detailed structure of the voltage boosting circuit is shown in Figure 6. The amplifying circuit is an additive proportional amplifying circuit with an 8-fold amplification. The signal access end of the amplifying circuit is provided with a 10K ohm resistor R6, the signal is amplified by the amplifying circuit and then connected to the voltage boosting circuit. The front end of the voltage boosting circuit is also connected to an adding circuit, which is used to convert the AC signal output by the amplifying circuit into a DC signal that can be directly received by the processor. The signal is amplified for single-chip microcomputer sampling. The amplified signal is still an AC signal, which is not suitable for single-chip microcomputer sampling. The amplified voltage signal is boosted by an adding circuit to become a DC signal suitable for single-chip microcomputer sampling. The processor adopts Microchip's PIC16F887 single-chip microcomputer, which has fewer pins, low cost, high immunity to interference, and its functions and performance are suitable for product design applications. The microcontroller has EEPROM, which can be used to store configuration parameters; the built-in 10-bit AD converter can fully meet the product's sampling accuracy requirements; at the same time, its built-in USART can be used for RS485 communication. the

The above-mentioned embodiment is only an embodiment of the present utility model, but should not be construed as limiting the scope of the present utility model. It should be pointed out that those skilled in the art can make several modifications and improvements without departing from the concept of the utility model, and these all belong to the protection scope of the utility model. the

Claims (5)

1. A CT-based power cable line load and temperature monitoring device, characterized in that it includes cables, zero-sequence current transformers, phase current transformers, I/V conversion protection circuits, filter circuits, amplifier circuits, and voltage boosting circuits , a processor, a temperature sensor, and a sending and receiving unit, wherein the cable is integrated with a three-phase power line and a grounding line, the three-phase power line is connected to a phase current transformer for collecting load current, and the grounding line is connected to There is a zero-sequence current transformer for measuring the ground current, the temperature sensor is in contact with the skin of the cable for measuring the skin temperature of the cable, the temperature sensor transmits the measured signal to the processor, the zero-sequence current transformer and The phase current transformer converts the current signal into a ratio and connects it to the I/V conversion protection circuit. The I/V conversion protection circuit converts the current signal into a voltage signal and performs clamping protection, and then is filtered by the filter circuit, amplified by the amplifier circuit, and the voltage The boost circuit boosts the voltage signal and connects it to the processor, the zero-sequence current transformer, phase current transformer, I/V conversion protection circuit, filter circuit, amplifier circuit, voltage boost circuit, processor, temperature sensor, and sending and receiving unit Installed in the control box next to the cable. the 2. A CT-based power cable line load and temperature monitoring device according to claim 1, characterized in that: the secondary side of the zero-sequence current transformer and/or phase current transformer is connected to I/V On the small current transformer CT1 of the conversion protection circuit, it is converted into a voltage signal through the sampling resistor R1, and the rear end of the I/V conversion protection circuit is provided with double diodes for voltage clamping and protection, and the sampling resistor R1 is 300 euros. the 3. A kind of CT-based power cable line load and temperature monitoring device according to claim 1, characterized in that: the filter circuit adopts a second-order voltage-controlled low-pass active filter circuit, and the filter circuit includes There is a dual operational amplifier circuit LM2904M chip, the 2 pins of the LM2904M chip are connected with a 1K ohm R1, and the 3 pins are connected with a 1K ohm resistor R3 and a capacitor C5, the capacitor C5 is 0.022μF, and the resistor R3 is connected in series with Resistor R2, resistance R2 is 10K ohms. the 4. A CT-based power cable line load and temperature monitoring device according to claim 1, characterized in that: the amplifying circuit is an addition proportional amplifying circuit with 8 times amplification, and the signal access terminal of the amplifying circuit A 10K ohm resistor R6 is set, and the signal is amplified by the amplifier circuit and then connected to the voltage boosting circuit. The front end of the voltage boosting circuit is also connected to an addition circuit, which is used to convert the AC signal output by the amplifier circuit into a signal that the processor can directly receive. DC signal. the 5. A CT-based power cable line load and temperature monitoring device according to claim 1, characterized in that: the processor adopts a PIC16F887 single-chip microcomputer, and the single-chip microcomputer is also connected with a power conversion module and a sending and receiving unit , wherein the sending and receiving unit is a full-duplex universal synchronous/asynchronous serial transceiver RS485 communication module, the temperature sensor is an Intel MF52103F temperature sensor, and the processor uploads the collected signal to the upper-level device through the communication module . the