Handheld cable grounding fault detection device

Abstract

The utility model discloses a handheld cable grounding fault detection device, which relates to the technical field of cable detection and comprises a shell with a wiring hole, a control circuit board arranged in the shell, a liquid crystal display screen arranged on the shell and a touch button module with a lamp. A power supply module, an inverter, a residual current transformer, a control module and a relay are arranged on the control circuit board, the output end of the power supply module is electrically connected with the input end of the inverter, the relay is arranged on an output circuit of the inverter, and the residual current transformer and the relay are both connected with the control module. The residual current transformer is used for detecting residual current signals on an output circuit of the inverter, the liquid crystal display screen and the touch button module with the lamp are both electrically connected with the control module, the structure is simple, the cost is low, carrying is convenient, and rapid and accurate cable grounding fault detection can be achieved.

Description

Technical Field

[0001] The present application relates to the field of cable detection technology, and in particular to a handheld cable grounding fault detection device. Background Art

[0002] Ground faults in power cables are inevitable due to factors such as vandalism or aging cable insulation, often resulting in personal injury or death. However, measuring DC resistance with a multimeter is difficult to pinpoint. Locating the fault point by measuring cable insulation is also slow, and the insulation values ​​measured on rainy days are often very close, making it difficult to determine the exact location of the cable ground fault. Commercially available detectors for locating cable ground faults are bulky and complex to operate. Utility Model Content

[0003] In view of this, the present application provides a handheld cable ground fault detection device to address the existing method of using a multimeter to measure DC resistance, which is difficult to locate the line cable ground fault point. Locating the line cable ground fault point by measuring cable insulation is too slow, and the cable insulation values ​​measured on rainy days are very close, making it difficult to determine the specific location of the cable ground fault point. Current cable ground fault detectors on the market are large in size and relatively complex to operate.

[0004] To achieve the above-mentioned object, the present utility model provides the following technical solutions: a handheld cable grounding fault detection device, the device comprising: a housing having a wiring hole;

[0005] A control circuit board is provided in the housing, on which a power supply module, an inverter, a residual current transformer L1, a control module, and a relay are provided. The output end of the power supply module is electrically connected to the input end of the inverter. The output end of the inverter is connected to a three-core cable, which includes an L line, an N line, and a PE line. The coil of the residual current transformer L1 is sheathed on the L line and the N line, and the relay is connected to the L line. The residual current transformer L1 and the relay are both electrically connected to the control module.

[0006] LCD screen;

[0007] The illuminated touch button module, the liquid crystal display screen and the illuminated touch button module are all electrically connected to the control module.

[0008] Furthermore, the end of the three-core cable is connected to one end of the cable to be tested through the wiring hole, the N line end and the PE line end at the front end of the three-core cable are connected together, and different types of clips are connected to the end of the three-core cable to adapt to cables of different wire diameters and wiring forms.

[0009] Furthermore, the control module includes a controller chip and a memory chip, and the memory chip is electrically connected to the controller chip.

[0010] Furthermore, it also includes an input voltage detection circuit, an output voltage detection circuit and an output current detection circuit;

[0011] The input end of the input voltage detection circuit is electrically connected to the output end of the power supply module, and the output end of the input voltage detection circuit is electrically connected to the signal input end of the controller chip;

[0012] The input end of the output voltage detection circuit is electrically connected to the output end of the inverter, and the output end of the output voltage detection circuit is electrically connected to the signal input end of the controller chip;

[0013] The input end of the output current detection circuit is electrically connected to the output end of the inverter, and the output end of the output current detection circuit is electrically connected to the signal input end of the controller chip.

[0014] Furthermore, the illuminated touch button module includes a voltage control button and a confirmation button.

[0015] It can be seen from the above technical solution that the advantages of the utility model are:

[0016] This application can safely and quickly locate the grounding fault point of the line cable, ensuring the safe and reliable operation of electrical equipment, and has a simple structure, low cost and is easy to carry. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The drawings that constitute a part of this application are used to provide further understanding of this application. The illustrative embodiments of this application and their descriptions are used to explain this application and do not constitute improper limitations on this application.

[0018] Figure 1 The utility model is a structural schematic diagram of a handheld cable grounding fault detection device.

[0019] Figure 2 This is a wiring diagram of a cable C phase grounding fault in Example 1 of the present utility model.

[0020] Figure 3 This is a wiring diagram of a cable N-phase grounding fault in Example 1 of the present utility model.

[0021] Figure 4 This is a schematic diagram of the circuit structure of the utility model.

[0022] Reference numerals:

[0023] Housing-1, LCD display-2, illuminated touch button module-3. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solutions and advantages of this application more clear, the following further describes this application in detail in conjunction with the embodiments and drawings. Here, the illustrative embodiments of this application and their descriptions are used to explain this application, but are not intended to limit this application.

[0025] Due to factors such as human damage or cable insulation aging, power supply cables are inevitably prone to grounding faults, resulting in personal injury or death. In order to quickly and safely locate the grounding fault point of the power supply cable and ensure the safe and reliable operation of electrical equipment, this application provides a handheld cable grounding fault detection device for locating the grounding fault point of the power supply cable. Figures 1 to 3 This embodiment provides a handheld cable grounding fault detection device. The handheld cable grounding fault detection device comprises a housing 1 with a wiring hole. A control circuit board is disposed within the housing 1 and includes a power supply module, an inverter, a residual current transformer L1, a control module, and a relay. The output of the power supply module is electrically connected to the input of the inverter. The output of the inverter is connected to a three-core cable consisting of an L wire, a N wire, and a PE wire. The coil of the residual current transformer L1 is wrapped around the L and N wires, and the relay is connected to the L wire. Both the residual current transformer L1 and the relay are electrically connected to the control module. The inverter converts DC to a safe AC voltage of 36V or a lower 24V AC voltage. While ensuring test safety, a higher output voltage results in a higher measured residual current value, facilitating the identification of the cable fault point. The residual current transformer L1 detects the residual current signal between the L and N wires. The relay module controls the on / off state of the circuit. The LCD display 2 uses a brightly lit LCD for convenient nighttime use and displays test parameters. The illuminated touch button module 3, LCD display 2, and illuminated touch button module 3 are all electrically connected to a control module, which includes a controller chip. The illuminated touch button 3 includes a voltage control button and a confirmation button. The voltage control button controls the closure of the normally open contacts of the relay on the circuit. Pressing the voltage control button illuminates the indicator light on the illuminated touch button, and LCD display 2 displays 36V, indicating that the inverter output terminal can output 36V AC voltage.

[0026] like Figure 1 As shown, the end of the three-core cable passes through the wiring hole and is connected to one end of the cable to be tested. The N line end and the PE line end at the front end of the three-core cable are connected together. Different types of clips are connected to the end of the three-core cable to adapt to cables of different wire diameters and wiring forms.

[0027] like Figure 4As shown, in the present application, an input voltage detection circuit, an output voltage detection circuit and an output current detection circuit are also included; the input end of the input voltage detection circuit is electrically connected to the output end of the power supply module, and the output end of the input voltage detection circuit is electrically connected to the signal input end of the controller chip. The input voltage detection circuit includes a resistor R1 and a resistor R2, one end of the resistor R1 is electrically connected to the output end of the power supply module, the other end of the resistor R1 is connected in series with one end of the resistor R2 and is connected to the signal input end of the controller chip, and the other end of the resistor R2 is grounded. The input end of the output voltage detection circuit is electrically connected to the output end of the inverter, and the output end of the output voltage detection circuit is electrically connected to the signal input end of the controller chip. The output voltage detection circuit includes resistors R3, R4, R5, diode D1, and capacitor C1. The positive electrode of diode D1 is connected to the output live wire of the inverter, the negative electrode of diode D1 is connected to one end of resistor R3, one end of resistor R5, and one end of capacitor C1, the other end of resistor R5, the other end of capacitor C1, and one end of resistor R4 are all grounded, and the other end of resistor R4 is connected to one end of resistor R3 and then electrically connected to the signal input end of the controller chip. The input end of the output current detection circuit is electrically connected to the output end of the inverter, and the output end of the output current detection circuit is electrically connected to the signal input end of the controller chip. The output current detection circuit includes a current transformer L2 and an amplifier circuit.

[0028] In this embodiment, the battery voltage is measured via the A / D converter port of the controller chip through the voltage divider of resistors R1 and R2. Based on the proportional relationship between battery voltage and capacity, the current battery charge is calculated and displayed on the LCD screen via the serial port of the controller chip. When the charge falls below 70% of the rated capacity, a charging prompt is displayed. The DC12V output of the lithium battery is converted to 50Hz, 36V AC power via a DC12V / AC36V inverter module. One end of the AC line serves as the neutral line N of the detection device, which is internally connected to the detection device ground line PE. The other end of the AC line serves as the live line L of the leakage detection device. The live line L passes through a rectifier and voltage divider circuit composed of D1, C1, R3, R4, and R5, and is connected to the A / D converter port on pin 1 of the controller chip to measure the output AC voltage.

[0029] The live wire L passes through the L2 current transformer. The voltage at the output end of the current transformer L2 is amplified and rectified by U2 and then sent to the A / D conversion port of the controller chip to measure the output AC current.

[0030] The live wire L and the neutral wire N pass through the L1 current transformer. The voltage at the output of the current transformer L1 is amplified and rectified by U3 and then sent to the A / D converter port of the controller chip to measure the output residual current. The controller chip used is model STC8H3K32S2-LQFP32.

[0031] A power switch is provided on the side of the device. When the switch is turned on, the battery power module power is displayed through the LCD 2. When the power is low, the device can be charged through the charging port of the battery power module.

[0032] like Figure 4 As shown, the live wire L is connected to the external cable under test via relay K1. When the controller chip detects that the voltage output control key V is pressed, it switches relay K1 on and off via Q1, thereby controlling the output AC voltage of the live wire L. The measured AC output voltage, output current, and residual current are transmitted via the controller chip's serial port to the LCD for display. The residual current value is locked and stored in the controller chip's internal RAM by pressing the data storage confirmation key OK.

[0033] like Figure 2 As shown, in this embodiment, when performing ground fault detection, the L line end, N line end and PE line end of the three-core cable are respectively connected to the A or B or C (live wire) phase line, N phase line and PE line of the line cable to be tested through clips.

[0034] During the test, confirm the fault first. When the line leakage protection device is activated, the leakage protection device still protects after power is supplied again, confirming that there is a ground fault in the line cable. Then press the voltage control button and apply 36V AC safety voltage between the A-phase cable and the N-phase cable that have been disconnected from the power supply. Connect the PE line end of the device to the PE line of the outgoing cable and to the ground terminal of the distribution cabinet (if the cable does not have a PE line, connect it directly to the ground terminal of the distribution cabinet). Figure 2As shown. The device houses a high-precision residual current transformer L1. After wiring is complete, it measures the residual current in the AN cable. Pressing the confirm button stores the measured data in memory and displays the residual current value on the display. Similarly, a 36V AC voltage is applied between the BN and CN cables (applying voltage between only one phase and the N phase at a time) to measure the residual current in each cable. The three residual current values ​​measured after applying voltage three times determine which phase has a ground fault. The phase with the highest residual current value is identified as the ground fault phase. If the residual current values ​​measured for all three phases are similar, the ground fault is in phase N. If the C phase cable is ground faulted, the residual current measured when the 36V AC voltage is applied to CN (PE) will be significantly higher than when the voltage is applied to AN (PE) or BN (PE). The device displays the test results on the LCD screen. Due to the varying insulation conditions of three-phase cables, a certain ground current exists in all three cables during three-phase power supply. When the vector sum of the residual currents in phases A, B, and C reaches the device's set value, the branch leakage protection device activates. Phases A, B, and C are connected together through a load, and the residual currents of each phase will affect each other. However, the difference in residual current values ​​between the phases is used to identify the phase with the highest residual current value. Absolute accuracy of the residual current values ​​for each phase is not required, thus avoiding influencing factors.

[0035] After determining which phase of the cable has a ground fault, a 36V voltage can be continuously applied to the faulty phase cable, and the corresponding residual current value can be measured at the same time. The dichotomy method can be used or the cable joints before and after the suspected cable ground fault point can be untied to determine which section of the cable has a ground fault based on whether the residual current value changes suddenly.

[0036] like Figure 2As shown, take a phase C ground fault in a streetlight cable as an example. If a phase C cable ground fault occurs, a 36V AC voltage is applied between phases C and N of the cable while measuring the residual current value of CN. When cable head 1 of phase C is untied, the measured residual current value decreases significantly, indicating that the cable ground fault point is behind cable head 1. When cable head 3 of phase C is untied, the measured residual current value does not change significantly, indicating that the cable ground fault point is in front of cable head 3. Continuing to untie cable head 2 of phase C toward cable head 1, the measured residual current value does not change significantly. Since there are no more cable heads to untie between cable heads 1 and 2, it is determined that the phase C cable ground fault occurs between sections 1 and 2. The method for finding the ground fault point of the A and B phase cables is similar. Although phases A, B, and C are connected together through the load, the residual current values ​​of each phase will affect each other, and each phase may have multiple points of poor insulation to ground. However, by removing the cable connectors and comparing the residual current values ​​at the measurement points before and after the line, the location with the largest change in residual current value can be identified, thereby confirming the location of the most serious ground fault in the cable. Absolute accuracy of the residual current values ​​measured at each point in the line cable is not required, as this avoids influencing factors. If multiple ground fault points exist, they can be eliminated one by one based on the points where the residual current value suddenly changes.

[0037] like Figure 3 As shown, a ground fault occurs in the N-phase cable. In order to obtain a higher residual current value and facilitate the judgment of the cable fault point, the output end of the portable 36V power supply is swapped with the previous connection method. The C phase of the cable (any live wire can be selected) is connected to the N phase end of the device, the PE end of the device is still connected to the PE line of the cable, and the N phase of the cable is connected to the L end of the device. In this way, there is a higher voltage on the N line cable, and the measured CN residual current value will be relatively high, which is helpful to determine which section the cable grounding fault point is between. The method for determining the grounding fault point is similar to the previous method for determining the location of the grounding fault point of the live phase cable. The present application is designed for the three-phase five-core cables commonly used on the market, but is also applicable to other types of cables such as single-phase cables and three-phase seven-core cables.

[0038] The above description is merely a preferred embodiment of the present application and is not intended to limit the present application. Those skilled in the art will appreciate that various modifications and variations of the present embodiment are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A handheld cable grounding fault detection device, characterized in that: include: A housing (1) having a wiring hole; A control circuit board is provided in the housing (1), the control circuit board being provided with a power supply module, an inverter, a residual current transformer L1, a control module and a relay, the output end of the power supply module being electrically connected to the input end of the inverter, the output end of the inverter being connected to a three-core cable, the three-core cable comprising an L line, an N line and a PE line, the coil of the residual current transformer L1 being sheathed on the L line and the N line, the relay being connected to the L line, and the residual current transformer L1 and the relay being electrically connected to the control module; LCD screen (2); A touch button module (3) with light, the liquid crystal display (2) and the touch button module (3) with light are both electrically connected to the control module.

2. The handheld cable grounding fault detection device according to claim 1, characterized in that: The end of the three-core cable passes through the wiring hole and is connected to one end of the cable to be tested. The N line end and the PE line end at the front end of the three-core cable are connected together. Different types of clips are connected to the end of the three-core cable to adapt to cables of different wire diameters and wiring forms.

3. The handheld cable grounding fault detection device according to claim 1, characterized in that: The control module includes a controller chip and a memory chip, and the memory chip is electrically connected to the controller chip.

4. The handheld cable grounding fault detection device according to claim 3, characterized in that: It also includes an input voltage detection circuit, an output voltage detection circuit and an output current detection circuit; The input end of the input voltage detection circuit is electrically connected to the output end of the power supply module, and the output end of the input voltage detection circuit is electrically connected to the signal input end of the controller chip; The input end of the output voltage detection circuit is electrically connected to the output end of the inverter, and the output end of the output voltage detection circuit is electrically connected to the signal input end of the controller chip; The input end of the output current detection circuit is electrically connected to the output end of the inverter, and the output end of the output current detection circuit is electrically connected to the signal input end of the controller chip.

5. The handheld cable grounding fault detection device according to claim 1, characterized in that: The illuminated touch button module (3) comprises a voltage control button and a confirmation button.

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