CN203630263U - Fault detector for power supply line - Google Patents

Abstract

The utility model relates to a power supply line fault detector, which belongs to an AC transmission line fault monitoring device. This instrument adopts field effect tube to take out the voltage signal indirectly from the transmission cable. The voltage signal is amplified by the voltage amplifying circuit composed of integrated op-amp block, and then amplified by the composite triode power amplifying circuit to drive the light-emitting diode to emit light and the music integrated block to sound an alarm. . When the normal section has electricity, there will be induction to send out sound and light signals; when the wire is disconnected, there will be no induction without live wire, so no sound and light signals will be sent out. The detector finds the line breakpoint according to the sound and light signal from start to stop. The instrument has the characteristics of low production cost and convenient fault detection.

Description

Power supply line fault detector

technical field

The utility model relates to a fault detection device for an AC transmission line, in particular to a disconnection fault detection device for a power supply line.

Background technique

The three-phase power supply represented by 380V is widely used in electric power, machinery, mines, etc., and the main objects of use are electric motors. Figure 1 and Figure 2 show the motor knife switch connection type and the air switch cable respectively. Connected circuit diagram. The two pictures are similar, in Figure 1, 1 is the power line, 2 is the knife switch, 3 is the load line, 4. is the crimping screw for the power line in and out of the knife gate, 5 is the crimping screw for the motor power line, and 6 is the motor; Similar to Fig. 1 in Fig. 2, just 2 is an air switch, 3 is a cable, and others are all the same.

The above motor structures, especially the gantry cranes at the station wharf, and the cranes in the production and maintenance workshops, etc., the cables are dragged and moved. During long-term stretching, bending, and folding, they often fail, produce abnormal noises, slow down the speed, and heat the coils. Wait, it can’t work normally, this is a phase failure phenomenon, and it needs to be shut down immediately for inspection and maintenance, otherwise, due to vibration and overheating, the insulation layer will be destroyed quickly, and even cause the motor to burn out.

However, checking with a meter for abnormal conditions can only be carried out at the wiring terminals or exposed places, and the middle is mostly wrapped and shielded by plastic rubber, so it is impossible to detect which section and where the problem is, and replace it completely. The workload is heavy and the investment is high, but relying on the existing labor, it is basically impossible to do anything, hindering production and delaying the construction period.

In order to solve the above problems, we conducted a test analysis. The power supply was connected to the first end, but there was no power at the end to work normally. In this way, it is usually disconnected or disconnected midway. However, instruments such as test pens and multimeters are contact measuring devices. After the insulating layer is isolated, it cannot be used directly. So, is there a way to detect the fault point without any exposed point and without damaging the insulation layer? In this regard, we decided to start with induction detection, design and manufacture the instrument circuit, and put it into use after success. It can detect quickly and accurately, find the breakpoint of the fault, and repair it so that it can resume work quickly.

Utility model content

The purpose of the utility model is to provide a power supply line fault detector which takes out the AC voltage signal in an inductive manner and quickly detects the disconnection fault.

The purpose of this utility model is achieved in this way: a power supply line fault detector, a metal probe is connected to the grid G of the field effect transistor VT1, the negative pole of the diode D1 is connected to the grid G of the field effect transistor VT1, and the positive pole of the diode D1 is connected to the grid G of the field effect transistor VT1. 9V battery EC negative pole, FET VT1 source S is connected in series with resistor R2 and then connected to 9V battery EC negative pole, field effect transistor VT1’s Class B series capacitor C1 is connected to 9V battery EC negative pole, FET VT1 drain D Connect resistor R1 in series to pin 7 of integrated operational amplifier block IC1, drain D of field effect transistor VT1 to the positive pole of electrolytic capacitor C2, and connect the negative pole of electrolytic capacitor C2 to the inverting input terminal of integrated operational amplifier block IC1 after series connection with resistor R3 , the positive phase input terminal of the integrated operational amplifier block IC1 is connected in series with the resistor R4 and then connected to the negative pole of the 9V battery. Resistor R5 is connected, pin 6 of the integrated op-amp block IC1 is connected to the base of the triode VT2, pin 7 of the integrated op-amp block IC1 is connected to one end of the switch K1, the other end of the switch K1 is connected to the positive pole of the 9V battery, and the emitter of the triode VT2 is connected to the The base of the triode VT3, the emitter of the triode VT3 are connected to the negative pole of the 9V battery, the collectors of the triodes VT2 and VT3 are connected to one end of the resistor R6, the other end of the resistor R6 is connected in series with the light-emitting diode Fg1 and then connected to the end of the switch K1, and the music integrated block IC2 and the piezoelectric ceramic chip are connected in parallel with the light-emitting diode Fg1; the model of the above-mentioned integrated op-amp block IC1 is LS741.

The resistor R3 is 10KΩ, and the resistor R5 is 100KΩ.

The beneficial effect of this instrument is:

1. Use the induction method to take out the voltage signal from the transmission cable to detect the disconnection fault, without stripping the cable insulation layer, and then contacting with an electric pen or a multimeter for detection. It has the characteristics of convenient and fast sampling and detection.

2. The circuit design of this instrument is simple and the production cost is low.

3. Strong practicability, can be combined with existing electric pens, multimeters, etc. to quickly detect faulty phase lines and breakpoint positions.

When the normal section has electricity, there will be induction and send out sound and light signals; when the wire is disconnected, there will be no induction without live wire, so no sound and light signals will be sent out. The detector finds the line breakpoint according to the sound and light signal from start to stop.

The features and advantages of this instrument will be further described in the following specific usage methods.

Description of drawings

Figure 1 is a schematic diagram of the connection between the power line and the motor switch.

Figure 2 is a schematic diagram of the connection between the power line and the air switch of the motor.

Figure 3 is a circuit diagram of the instrument.

Fig. 4 is a schematic diagram of single-phase fault finding corresponding to Fig. 1 .

Fig. 5 is a schematic diagram corresponding to Fig. 2 for fault finding of cable breakpoints.

Fig. 6 is a schematic diagram of electromagnetic field distribution.

Fig. 7 is a schematic diagram of electromagnetic field limitation with a neutral line.

Detailed ways

Circuit design:

According to the fault finding requirements, we designed a practical circuit for the tester, see Figure 1.

In Figure 3, we choose the field effect transistor VT1 with a large input resistance and high sensitivity MOS structure as the sampler. The drain D and source S of VT1 are respectively connected to resistors R1 and R2, and the substrate B (ie The B pole) is connected to the capacitor C1, which is to determine the working point, enhance the stability, and generate nearly 10 times the amplification effect when the gate signal arrives. The grid G is drawn out as a signal probe, and it is brought close to the transmission line. In the alternating electric field, the induction can be obtained, that is, the electrical signal is collected; otherwise, if the electrical signal cannot be collected, it means that the power transmission is interrupted. Two or three comparisons in the test can determine the point of failure. This is the sampling principle of the test detector.

The middle part of Figure 2 is centered on the LS741 integrated operational amplifier circuit IC1 to form a voltage amplifier. This is because the sensed signal is very weak and cannot drive the rear alarm circuit, so this design is made. In order to increase the amount of input signal, the resistor R3 is taken as 10KΩ, and the feedback resistor R5 is taken as 100KΩ, so the amplification factor is:

A=R5/R3=100÷10=10;

The total amplification factor of FET and operational amplifier is: 10х10 =100.

It can be seen that the front and rear circuits increase the signal by about 100 times, so for the signal of only millivolt level sensed by the gate of the field effect transistor, it will also be amplified to hundreds of millivolts, which is enough to drive the subsequent circuit to work.

After the reversal of IC1, a high level is output from pin 6, which drives the composite power amplifier circuit VT2 and VT3 to be turned on. After VT2 and VT3 are turned on and turned on, the series resistance R6 divides the voltage. When the upper end gets 3V voltage, the light-emitting tube Fg1 is lit, and the music integrated block IC2 conducts electricity, (or use piezoelectric ceramic sheet HTD) to send out an alarm sound. It means that there is an alternating electric signal at this place, so you can continue to check along the line until the sound and light signal disappears, then it means that the line is broken.

Because the instrument is a hand-held mobile work, it is not suitable to use AC power. Therefore, we have designed a dry battery working method, as shown in Figure 1. Ec on the right side, Ec is a 9V square battery, which not only ensures the required working voltage of the integrated block, but also facilitates replacement.

In the figure, the diode D1 is connected in reverse, because the BG1 probe line collects the alternating signal, and the positive half wave of the alternating signal is required for the work of the composite tube and cannot be cut, so D1 is connected in reverse, just Block the passage of the positive half-wave; in the negative half-wave, the reverse diode D1 conducts, leading the negative half-wave signal to the negative pole of the power supply, so that the collected electrical signal and the power supply in the working circuit just form a common ground, so that it can reach The effect of integration, so it can work normally and stably.

How to use: This patent is aimed at the three-phase power supply. When a disconnection fault occurs, how to quickly find out which section and exact position the breakpoint is in, so as to facilitate rapid discharge; but the test requires a correct method. The first is to determine the faulty phase line, and the second is to test the breakpoint, and there are respective methods respectively.

3.1 Fault phase wire inspection method

3.1.1 Test pencil method

First, use the test pen to click the phases A, B, and C on the pressure screw on the power supply side. If they all emit light, it means that the power supply side is normal; then turn to the motor side and click the pressure screw. The light is normal, otherwise there is a problem. .

3.1.2 Multimeter method

Still first test the voltage between the lines on the power supply side, if both are 380V, it means that the input on the power supply side is normal; then turn to the motor side to test the voltage between the lines, if it is also 380V, it means that the two lines are normal, and then turn the two lines to the third line respectively With the test, whether the response is 0 volts or other data (such as tens of volts), it can be verified that there is a problem with the third line.

3.2 Fault Breakpoint Test Method

After determining the phase line, we will use the developed detector to further search for the break point that causes the phase loss. According to the measurement and analysis, the test method is not as simple as imagined, such as:

3.2.1 Single-phase energization method

After checking the phase sequence, for example, it is determined that the B phase is disconnected, so is it possible to find the break point only by connecting the live wire power supply to the B phase? Because in theory, after the power is turned on, there should be induction electricity before the breakpoint, but the power should be lost after the breakpoint, so as to confirm the fault point.

But this is not the case actually. As shown in Figure 4, when we walked along the line with a hand-held detector, walked back and forth across the entire line several times, the acousto-optic signals in the detector did not disappear, so we failed to find the broken line.

3.2.2 Two-wire power-on method

It has also been confirmed that the B phase is disconnected, and the pressure of the B phase alone is not enough, so what about using the A-B two-phase or C-B two-phase pressure test instead? The theory is that there is induction electricity before the breakpoint, and the power should be lost after the breakpoint, so as to find the breakpoint. However, it is not true! Similarly, I went through the whole line several times, but the acousto-optic signal of the detector did not disappear, so the breakpoint was still not found.

Why is this? Is the actual detection effect completely inconsistent with the theory?

After we finish the experiment, we will analyze and answer the questions comprehensively.

3.2.3 Single-phase test method

In the above-mentioned use of single-wire or double-wire plus live wire, the breakpoint cannot be tested. For this reason, we seek a new method, as shown in Figure 4. In the place where there is a neutral wire, take a single live wire, which is the problematic phase B. , For the neutral line, switch to 220V single-phase test. We also walk along the line with the hand-held detector as shown in Figure 4. The acousto-optic signal in the detector stops before the line is completed, and then goes back and forth two or three times, and the same result occurs at the same place. Therefore, it is determined that the acousto-optic disappearance is disconnection point.

3.2.4 Power frequency source test method

Since the three-phase motors work independently and the field application design is not well thought out, some places may not have a matching zero line installed, so it is not possible to make a single-phase conversion connection nearby. In this regard, a power frequency oscillator can be used to provide 220V AC power, and the same test as described in 3.2.3 can be used to find the breakpoint in the faulty line. the

3.3 Fault breakpoint repair method

After testing to the breakpoint, as shown in Figure 4, we peeled off the sheath of the transmission line in a targeted manner. Sure enough, as shown inside the anatomical line, the breakpoint was revealed.

With the breakpoint found, we can fix the connection without a doubt. After repairing, it is necessary to repack the external insulation layer and restore all connections at the same time. After ensuring safety and correctness, close the switch and connect the 380V power supply. The motor will run according to the rated value and resume normal work.

In the field, it is possible that after finding and troubleshooting a certain breakpoint, the fault is still not eliminated, indicating that there are more than two breakpoints. For this, we only need to repeat the above inspection methods and steps to find out more. point of failure. Until the solution is completed, resume work.

The above method is mainly introduced with the knife gate connection method in Figure 4, but it is still practical for the air switch and cable transmission in Figure 5, and the methods and steps are basically the same. Finally, as shown in the anatomical line in Figure 5, the breakpoint is also found.

The patented instrument and method can also be extended to load line breakpoint search of more voltage levels such as 220V, so the practical range is wide and there is good promotion prospect.

Analysis of the reasons why FireWire cannot test breakpoints

Finally, we want to reveal why the breakpoint cannot be detected when a single live wire or double live wires are connected to the faulty line.

After analysis and testing, it is known that the pure live wire, the electromagnetic field is not blocked by metal, as shown in Figure 6, its shielding is the earth with a certain distance, and the electromagnetic field is elliptical, so the electromagnetic field distribution is wide, that is, the electromagnetic field intensity is large, so it can be Covering or even connecting the breakpoint, thus, the situation that the sound and light signals are continuously blocked will occur.

And there is a neutral line phase configuration, as shown in Figure 6. The metal blocking distance is close, which can block the electromagnetic field of the live line, so the disconnection point of the line can play the role of power failure, so the detector can not sense the electric field, so that the sound and light signal can be terminated. We also find the disconnection point from this.

To sum up, we have found the answer that the breakpoint cannot be detected by pure live wire, but the single-phase power supply with neutral wire can test the breakpoint.

Claims (2)

1. an electrical source of power circuit fault locator, it is characterized in that, in field effect transistor VT1 grid G, be connected with a metal probe, diode D1 negative pole is connected to field effect transistor VT1 grid G, diode D1 positive pole is connected to 9V battery EC negative pole, after field effect transistor VT1 source S series resistor R2, be connected to 9V battery EC negative pole, after the B level serial connection capacitor C 1 of field effect transistor VT1, be connected to 9V battery EC negative pole, after field effect transistor VT1 drain D series resistor R1, be connected to 7 pin of operationa IC1, field effect transistor VT1 drain D is connected to electrochemical capacitor C2 positive pole, after electrochemical capacitor C2 negative pole series resistor R3, be connected to operationa IC1 inverting input, after the normal phase input end series resistor R4 of operationa IC1, be connected to 9V battery cathode, 4 pin of operationa IC1 are connected to 9V battery cathode, between 2 pin of operationa IC1 and 6 pin, be serially connected with resistance R 5, 6 pin of operationa IC1 are connected to triode VT2 base stage, 7 pin of operationa IC1 are connected to K switch 1 one end, K switch 1 other end is connected to 9V anode, triode VT2 emitter is connected to triode VT3 base stage, triode VT3 emitter is connected to 9V battery cathode, triode VT2, the two collector of VT3 is connected to resistance R 6 one end, after resistance R 6 other end serial connection light emitting diode Fg1, be connected to K switch 1 one end, and music integrated block IC 2 or piezoelectric ceramic piece are in parallel with light emitting diode Fg1, above-mentioned operationa IC1 model is LS741.

2. electrical source of power circuit fault locator according to claim 1, is characterized in that, described resistance R 3 is 10K Ω, and resistance R 5 is 100K Ω.

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