A fast and safe cable insulation tester and its detection method

Abstract

The present invention relates to a fast and safe cable insulation tester and a detection method thereof, comprising a plurality of multifunctional terminal hooks, an insulation connecting wire and an insulation tester, wherein the plurality of multifunctional terminal hooks are connected to the insulation tester through the insulation connecting wire, and the insulation tester comprises a housing and an internal circuit, wherein the internal circuit realizes one-key automatic detection of the insulation resistance to ground of all six-phase cables of a double cable by adding a plurality of groups of intelligent detection circuits, or detects the insulation resistance between phases one by one. After testing, it takes 4 minutes to install and remove the insulation connecting wire at one time, 4 minutes to detect the six-phase resistance to ground at the same time, and 6 minutes to detect the resistance between phases one by one, which is about 14 minutes in total. Compared with the current method, the detection time is shortened by 28 minutes, and the operation time of the climbers on the tower is shortened by 38 minutes.

Description

Technical Field

[0001] The invention belongs to the field of cable maintenance, and in particular to a fast and safe cable insulation detector and a detection method thereof. Background Art

[0002] High-voltage transmission lines are mostly hybrid lines connected by overhead lines and cables in sections. Once a line fault occurs, it needs to be checked section by section, and the insulation resistance of each cable section needs to be tested. Currently, insulation testing for one cable section of a hybrid line mainly involves climbing up the pole towers at both ends to ignite the wire. After the tower workers wrap copper wire around the cable terminals and connect them, the inspection personnel perform insulation testing at the bottom of the tower. After the test of one phase is completed, the tower workers use a discharge rod to discharge the wire before testing the next phase. Under normal circumstances, excluding climbing the tower to hang the ground wire and ignite the wire, a single-phase insulation test takes about 3 minutes, and an interphase insulation test takes about 4 minutes, for a total of 42 minutes for six phases. The workers responsible for hanging the connecting wires and discharging the wires need to stay on the tower throughout the process and move constantly.

[0003] Because faults often occur at night or in rainy or snowy weather, tower operators have poor visibility, making it difficult to observe the situation above the tower. This leads to communication difficulties with operators on the tower, which prolongs the time required to resolve cable faults. This is especially true for cable selection and testing on multi-segment towers. The complex inspection process consumes a significant amount of time and manpower. Furthermore, many faulty towers still have another line energized, creating significant risks of falling and electric shock.

[0004] Therefore, there is a need for an intelligent cable insulation tester that can quickly and safely detect cable insulation, reduce long-term high-altitude operations such as moving on towers, and shorten insulation detection time. Summary of the Invention

[0005] The purpose of the present invention is to overcome the shortcomings of the existing technology and propose a fast and safe cable insulation tester and a detection method thereof, which can reduce long-term high-altitude operations such as moving on the tower, shorten the insulation detection time, and can transplant the tower operation to the insulation tester under the tower, so that the detection items can be freely selected.

[0006] The present invention solves the technical problem by adopting the following technical solutions:

[0007] A fast and safe cable insulation tester includes multiple multifunctional terminal hooks, insulation connecting wires and an insulation tester. The multiple multifunctional terminal hooks are connected to the insulation tester via the insulation connecting wires. The insulation tester includes a shell and an internal circuit. The shell includes a 6-phase single-phase cable detection jack, a 6-phase interphase cable detection jack, a double ground wire jack, an intelligent detection circuit E-pole jack, an LED display, a shifter and a discharge switch. The LED display is placed at the right end of the shell surface, the shifter and the discharge switch are placed below the LED display, the double ground wire jack is placed at the left end of the LED display, the intelligent detection circuit E-pole jack is placed below the double ground wire jack, and the 6-phase single-phase cable detection jack and the 6-phase interphase cable detection jack are placed at the left end of the ground wire jack.

[0008] Moreover, the shifter is an eight-speed dual-control shifter.

[0009] Moreover, the internal circuit includes multiple groups of intelligent detection circuits, which include: detection circuit, disconnection circuit and LED display screen. The detection circuit includes: DC voltage converter, operational amplifier, resistor R1, resistor R2, resistor Rf, inverter and AD converter, and the disconnection circuit includes: relay, termination resistor, pull-down resistor, current limiting resistor, MOS tube and discharge diode and single-chip microcomputer. The wiring method of the intelligent detection circuit is: the DC voltage converter is connected to the relay, the other end of the relay is connected to one end of the resistor R1 and one end of the insulation resistance of the cable to be measured to the ground, the other end of the resistor R1 is respectively connected to the grounding resistor R2 and an input end of the AD converter, the other end of the insulation resistance of the cable to be measured to the ground is suspended and forms a measured resistance with the ground, one end of the resistor Rf and the second tube of the operational amplifier are connected. The pin is connected to the E-pole jack of the intelligent detection circuit, and forms a loop with the measured resistor through the ground wire. The third pin of the operational amplifier is grounded, the eighth pin of the operational amplifier is connected to the other end of the resistor Rf, and the first pin of the operational amplifier is respectively connected to the third end of the resistor Rf and the input end of the inverter. The output end of the inverter is connected to the other input end of the AD converter. The output end of the AD converter is connected to the microcontroller through the SPI bus, the microcontroller is connected to the LED display through the UART, and the microcontroller is connected to one end of the termination resistor through the IO interface. The other end of the termination resistor is respectively connected to the grounded pull-down resistor and the gate of the MOS tube. The source of the MOS tube is connected to the grounded current limiting resistor. The drain of the MOS tube is respectively connected to the positive electrode of the discharge diode and the control end of the relay, and the negative electrode of the discharge diode is connected to the other control end of the relay.

[0010] Moreover, the multifunctional terminal hook includes a metal hook, a nut with a gasket, a metal ring and a wiring groove. The nut with a gasket is fixed on the side wall of the metal ring, and the wiring groove is fixed on the side wall of the metal ring on the opposite side of the nut with a gasket. The metal hook and the nut with a gasket are connected by threads.

[0011] Moreover, the insulated connecting wire is a double-cable six-phase connecting wire wrapped with an insulating sheath, and the double-cable six-phase connecting wire includes a night-lighting layer and a phase color layer in sequence from the outside to the inside.

[0012] Moreover, one end of the insulating connecting wire is connected to a plurality of multifunctional terminal hooks through a wiring slot, and the other end of the insulating connecting wire is a plug for a double-cable six-phase connecting wire.

[0013] A fast and safe cable insulation tester detection method includes the following steps:

[0014] Step 1. Select different hanging points of the multi-function terminal hook according to the cable terminal type to hang the cable to be tested: If the cable to be tested has an open terminal, use a metal hook to hang it in the bolt hole of the copper busbar of the cable to be tested according to the corresponding phase color; If the cable to be tested has a plug-in terminal, use a metal ring to cover the tension cone of the plug-in terminal accessory according to the corresponding phase color;

[0015] Step 2. Connect the other end of the insulation connection wire to the 6-phase single-phase cable detection jack or 6-phase interphase cable detection jack of the insulation tester in sequence according to the phase color;

[0016] Step 3: Determine whether it is single-phase detection or inter-phase detection. If it is single-phase detection, proceed to step 4; if it is inter-phase detection, proceed to step 7;

[0017] Step 4: Determine whether it is single-phase to ground detection or multi-phase to ground detection. If it is single-phase to ground detection, proceed to step 5; otherwise, proceed to step 6.

[0018] Step 5. One of the dual ground wire jacks is grounded, and the other is connected to the E-pole jack of the insulation tester. The shifter is moved to the corresponding gear. The DC voltage converter outputs DC high voltage. The converter and analog-to-digital converter convert the analog current signal returned by the test into a digital voltage signal, which is input into the microcontroller through the SPI bus. After the test is completed, the MCU controls the DC voltage converter to step down the voltage, outputs a signal through the IO interface to cut off the detected phase detection voltage, discharges the phase through the discharge switch, and displays the test results on the LED display.

[0019] Step 6. One of the dual ground wire jacks is grounded, and the other is connected to the E-pole jack of the insulation tester. The shifter is turned to the ALL position, and the DC voltage converter outputs DC high voltage. The converter and the analog-to-digital converter convert the analog current signal returned by the detection into a digital voltage signal, which is input into the single-chip microcomputer through the SPI bus. If there is a defect in the insulation of a phase of the tested cable, the signal fed back to the MCU by this phase is abnormal. The MCU controls the DC voltage converter to reduce the voltage and outputs a signal through the IO interface to cut off the detection voltage of the tested phase. The other phases continue to perform the boost test. After the test is completed, the discharge is carried out through the discharge switch, and the LED display shows the test results.

[0020] Step 7. One of the dual ground wire jacks is grounded and the other is disconnected. The interphase cable detection jack of one phase of the two-phase cable to be tested is connected to the E-pole jack of the insulation tester. The shifter is moved to the corresponding gear of the other phase of the two-phase cable to be tested. The DC voltage converter outputs DC high voltage. The converter and analog-to-digital converter convert the analog current signal returned by the test into a digital voltage signal, which is input into the microcontroller through the SPI bus. After the test is completed, the MCU controls the DC voltage converter to step down the voltage, outputs a signal through the IO interface to cut off the detection voltage of the cable to be tested, discharges through the discharge switch, and the LED display shows the test results.

[0021] The advantages and positive effects of the present invention are:

[0022] The present invention includes multiple multifunctional terminal hooks, insulation connecting wires, and an insulation tester. The multiple multifunctional terminal hooks are connected to the insulation tester via the insulation connecting wires. The insulation tester includes a housing and internal circuitry. The internal circuitry, by adding multiple sets of intelligent detection circuits, enables one-click automatic detection of the insulation resistance to ground of all six phases of a dual-cable system, or detection of the insulation resistance between phases one by one. Testing has shown that a single installation and removal of the insulation connecting wires takes four minutes, simultaneous six-phase resistance detection takes four minutes, and phase-to-phase resistance detection takes six minutes, for a total of approximately 14 minutes. This reduces detection time by 28 minutes compared to current standards and reduces tower climbing time by 38 minutes.

[0023] The multifunctional terminal hook of the present invention comprises a metal hook, a nut with a washer, a metal ring, and a wiring slot. The nut with a washer is fixed to the side wall of the metal ring, and the wiring slot is fixed to the side wall of the metal ring opposite the nut with a washer. The metal hook and the nut with a washer are connected by a thread. This allows for the one-time installation and removal of insulated connecting wires, eliminating the need to change wiring methods mid-process, and completely eliminating the risk of workers staying on the tower for extended periods of time and repeatedly moving around. The insulated connecting wire also features a nighttime display function, effectively improving wiring reliability. The terminal hook can also be freely replaced according to the cable terminal type. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 , is the internal intelligent detection circuit diagram of the insulation tester of the present invention;

[0025] Figure 2 , is a structural diagram of the housing of the insulation tester of the present invention;

[0026] Figure 3 , is a structural diagram of the insulated connecting wire of the present invention;

[0027] Figure 4 , is a structural diagram of the metal hook of the present invention. Description of the drawings:

[0029] 1-6-phase single-phase cable detection jack, 2-6-phase inter-phase cable detection jack, 3-double ground wire jack, 4-LED display, 5-shifter, 6-discharge switch, 7-intelligent detection circuit E-pole jack, 8-insulated connecting wire, 9-double cable six-phase connecting wire, 10-night display layer, 11-phase color layer, 12-metal hook, 13-nut with washer, 14-metal ring, 15-wiring slot. DETAILED DESCRIPTION

[0030] The present invention is further described below in conjunction with the accompanying drawings.

[0031] A fast and safe cable insulation tester includes multiple multifunctional terminal hooks, insulation connecting wires and insulation tester, wherein the multiple multifunctional terminal hooks are connected to the insulation tester through the insulation connecting wires, and the insulation tester includes a shell and an internal circuit. Figure 2 As shown, its shell includes 6-phase single-phase cable detection jacks, 6-phase interphase cable detection jacks, double ground wire jacks, intelligent detection circuit E-pole jack, LED display, shifter and discharge switch. The LED display is placed at the right end of the shell surface, the shifter and discharge switch are placed below the LED display, the double ground wire jacks are placed at the left end of the LED display, the intelligent detection circuit E-pole jack is placed below the double ground wire jacks, and the 6-phase single-phase cable detection jacks and the 6-phase interphase cable detection jacks are placed at the left end of the ground wire jack.

[0032] The shifter is an eight-speed dual-control shifter.

[0033] like Figure 1As shown, the internal circuit includes multiple groups of intelligent detection circuits, which include: a detection circuit, a disconnection circuit and an LED display screen. The detection circuit includes: a DC voltage converter, an operational amplifier, a resistor R1, a resistor R2, a resistor Rf, an inverter and an AD converter. The disconnection circuit includes: a relay, a terminating resistor, a pull-down resistor, a current limiting resistor, a MOS tube and a bleeder diode and a single-chip microcomputer. The wiring method of the intelligent detection circuit is: the DC voltage converter is connected to the relay, the other end of the relay is connected to one end of the resistor R1 and one end of the insulation resistance of the cable to be measured to the ground, the other end of the resistor R1 is respectively connected to the grounding resistor R2 and an input end of the AD converter, the other end of the insulation resistance of the cable to be measured to the ground is suspended and forms a measured resistance with the ground, one end of the resistor Rf and the second pin of the operational amplifier are connected. It is connected to the E-pole jack of the intelligent detection circuit, and forms a loop with the measured resistor through the ground wire. The third pin of the operational amplifier is grounded, the eighth pin of the operational amplifier is connected to the other end of the resistor Rf, the first pin of the operational amplifier is respectively connected to the third end of the resistor Rf and the input end of the inverter, the output end of the inverter is connected to the other input end of the AD converter, the output end of the AD converter is connected to the microcontroller through the SPI bus, the microcontroller is connected to the LED display through the UART, the microcontroller is connected to one end of the termination resistor through the IO interface, the other end of the termination resistor is respectively connected to the grounded pull-down resistor and the gate of the MOS tube, the source of the MOS tube is connected to the grounded current limiting resistor, the drain of the MOS tube is respectively connected to the positive electrode of the discharge diode and the control end of the relay, and the negative electrode of the discharge diode is connected to the other control end of the relay.

[0034] like Figure 4 As shown, the multifunctional terminal hook includes a metal hook, a nut with a gasket, a metal ring and a wiring slot. The nut with a gasket is fixed to the side wall of the metal ring, the wiring slot is fixed to the side wall of the metal ring on the opposite side of the nut with a gasket, and the metal hook and the nut with a gasket are connected by threads.

[0035] like Figure 3 As shown, the insulated connecting wire is a double-cable six-phase connecting conductor wrapped with an insulating sheath, and the double-cable six-phase connecting conductor includes a night-lighting layer and a phase color layer from the outside to the inside.

[0036] One end of the insulating connecting wire is connected to a plurality of multifunctional terminal hooks through a wiring slot, and the other end of the insulating connecting wire is a plug for a double-cable six-phase connecting wire.

[0037] A fast and safe cable insulation tester detection method includes the following steps:

[0038] Step 1. Select different hanging points of the multi-function terminal hook according to the cable terminal type to hang the cable to be tested: If the cable to be tested has an open terminal, use a metal hook to hang it in the bolt hole of the copper busbar of the cable to be tested according to the corresponding phase color; If the cable to be tested has a plug-in terminal, use a metal ring to cover the tension cone of the plug-in terminal accessory according to the corresponding phase color;

[0039] Step 2. Connect the other end of the insulation connection wire to the 6-phase single-phase cable detection jack or 6-phase interphase cable detection jack of the insulation tester in sequence according to the phase color;

[0040] Step 3: Determine whether it is single-phase detection or inter-phase detection. If it is single-phase detection, proceed to step 4; if it is inter-phase detection, proceed to step 7;

[0041] Step 4: Determine whether it is single-phase to ground detection or multi-phase to ground detection. If it is single-phase to ground detection, proceed to step 5; otherwise, proceed to step 6.

[0042] Step 5. One of the dual ground wire jacks is grounded, and the other is connected to the E-pole jack of the insulation tester. The shifter is moved to the corresponding gear. The DC voltage converter outputs DC high voltage. The converter and analog-to-digital converter convert the analog current signal returned by the test into a digital voltage signal, which is input into the microcontroller through the SPI bus. After the test is completed, the MCU controls the DC voltage converter to step down the voltage, outputs a signal through the IO interface to cut off the detected phase detection voltage, discharges the phase through the discharge switch, and displays the test results on the LED display.

[0043] Step 6. One of the dual ground wire jacks is grounded, and the other is connected to the E-pole jack of the insulation tester. The shifter is turned to the ALL position, and the DC voltage converter outputs DC high voltage. The converter and the analog-to-digital converter convert the analog current signal returned by the detection into a digital voltage signal, which is input into the single-chip microcomputer through the SPI bus. If there is a defect in the insulation of a phase of the tested cable, the signal fed back to the MCU by this phase is abnormal. The MCU controls the DC voltage converter to reduce the voltage and outputs a signal through the IO interface to cut off the detection voltage of the tested phase. The other phases continue to perform the boost test. After the test is completed, the discharge is carried out through the discharge switch, and the LED display shows the test results.

[0044] Step 7. One of the dual ground wire jacks is grounded and the other is disconnected. The interphase cable detection jack of one phase of the two-phase cable to be tested is connected to the E-pole jack of the insulation tester. The shifter is moved to the corresponding gear of the other phase of the two-phase cable to be tested. The DC voltage converter outputs DC high voltage. The converter and analog-to-digital converter convert the analog current signal returned by the test into a digital voltage signal, which is input into the microcontroller through the SPI bus. After the test is completed, the MCU controls the DC voltage converter to step down the voltage, outputs a signal through the IO interface to cut off the detection voltage of the cable to be tested, discharges through the discharge switch, and the LED display shows the test results.

[0045] According to the above-mentioned fast and safe cable insulation tester and method, the performance of the present invention is verified by testing a certain cable terminal.

[0046] After testing, it takes 4 minutes to install and remove the insulated connecting wires, 4 minutes to test the six-phase-to-ground resistance, and 6 minutes to test each phase-to-phase resistance, for a total of approximately 14 minutes. This reduces the testing time by 28 minutes compared to the current time and reduces the tower climbing time by 38 minutes.

[0047] It should be emphasized that the embodiments described in the present invention are illustrative rather than restrictive. Therefore, the present invention includes but is not limited to the embodiments described in the specific embodiments. Any other embodiments derived by those skilled in the art based on the technical solutions of the present invention also fall within the scope of protection of the present invention.

Claims

1. A fast and safe cable insulation tester, characterized by: It includes a plurality of multifunctional terminal hooks, insulating connecting wires and an insulation tester. The plurality of multifunctional terminal hooks are connected to the insulation tester through the insulating connecting wires. The insulation tester includes a shell and an internal circuit. The shell includes a 6-phase single-phase cable detection socket, a 6-phase interphase cable detection socket, a double grounding socket, an intelligent detection circuit E-pole socket, an LED display, a shifter and a discharge switch. The LED display is placed on the right end of the shell surface, the shifter and the discharge switch are placed below the LED display, the double grounding socket is placed on the left end of the LED display, the intelligent detection circuit E-pole socket is placed below the double grounding socket, and the 6-phase single-phase cable detection socket and the 6-phase interphase cable detection socket are placed on the left end of the grounding socket; The internal circuit includes multiple groups of intelligent detection circuits, and the intelligent detection circuit includes: a detection circuit, a disconnection circuit and an LED display screen. The detection circuit includes: a DC voltage converter, an operational amplifier, a resistor R1, a resistor R2, a resistor Rf, an inverter and an AD converter. The disconnection circuit includes: a relay, a termination resistor, a pull-down resistor, a current limiting resistor, a MOS tube and a discharge diode and a single-chip computer. The wiring method of the intelligent detection circuit is: the DC voltage converter is connected to the relay, and the other end of the relay is connected to one end of the resistor R1 and one end of the insulation resistance of the measured cable to the ground. The other end of the resistor R1 is respectively connected to the grounding resistor R2 and an input end of the AD converter. The other end of the insulation resistance of the measured cable to the ground is suspended and constitutes a measured resistance with the ground. One end of the resistor Rf and the second pin of the operational amplifier are connected to the ground. The E-pole jack of the intelligent detection circuit is connected, and a loop is formed with the measured resistor through the grounding wire. The third pin of the operational amplifier is grounded, the eighth pin of the operational amplifier is connected to the other end of the resistor Rf, the first pin of the operational amplifier is respectively connected to the third end of the resistor Rf and the input end of the inverter, the output end of the inverter is connected to the other input end of the AD converter, the output end of the AD converter is connected to the single-chip microcomputer through the SPI bus, the single-chip microcomputer is connected to the LED display screen through the UART, the single-chip microcomputer is connected to one end of the termination resistor through the IO interface, the other end of the termination resistor is respectively connected to the grounded pull-down resistor and the gate of the MOS tube, the source of the MOS tube is connected to the grounded current limiting resistor, the drain of the MOS tube is respectively connected to the positive electrode of the discharge diode and the control end of the relay, and the negative electrode of the discharge diode is connected to the other control end of the relay.

2. A fast and safe cable insulation tester according to claim 1, characterized in that: The shifter is an eight-speed dual-control shifter.

3. A fast and safe cable insulation tester according to claim 1, characterized in that: The multifunctional terminal hook comprises a metal hook, a nut with a gasket, a metal ring and a wiring groove. The nut with a gasket is fixedly mounted on the side wall of the metal ring, the wiring groove is fixedly mounted on the side wall of the metal ring on the opposite side of the nut with a gasket, and the metal hook is connected to the nut with a gasket through threads.

4. A fast and safe cable insulation tester according to claim 1, characterized in that: The insulated connecting wire is a double-cable six-phase connecting wire wrapped by an insulating sheath, and the double-cable six-phase connecting wire includes a night display layer and a phase color layer from the outside to the inside.

5. A fast and safe cable insulation tester according to claim 4, characterized in that: One end of the insulating connecting wire is connected to a plurality of multifunctional terminal hooks through a wiring slot, and the other end of the insulating connecting wire is a plug for connecting double-cable six-phase conductors.

6. A fast and safe cable insulation tester detection method according to any one of claims 1 to 5, characterized in that: The following steps are involved: Step 1. Select different hanging points of the multifunctional terminal hook according to the cable terminal form to hang the cable to be tested: if the cable to be tested is an open terminal, use a metal hook to hang it in the bolt hole of the copper bar of the cable to be tested according to the corresponding phase color; if the cable to be tested is a plug-in terminal, use a metal ring to cover the tension cone of the plug-in terminal accessory according to the corresponding phase color; Step 2: Connect the other end of the insulation connection wire to the 6-phase single-phase cable detection socket or the 6-phase interphase cable detection socket of the insulation tester in sequence according to the phase color; Step 3: Determine whether it is single-phase detection or phase-to-phase detection. If it is single-phase detection, proceed to step 4; if it is phase-to-phase detection, proceed to step 7; Step 4: Determine whether it is single-phase to ground detection or multi-phase to ground detection. If it is single-phase to ground detection, proceed to step 5; otherwise, proceed to step 6. Step 5, one of the dual ground wire jacks is grounded, and the other is connected to the E-pole jack of the insulation tester. The shifter is shifted to the corresponding gear, and the DC voltage converter outputs DC high voltage. The converter and the analog-to-digital converter convert the analog current signal returned by the detection into a digital voltage signal, which is input into the single-chip microcomputer through the SPI bus. After the test is completed, the MCU controls the DC voltage converter to step down the voltage, outputs a signal through the IO interface to cut off the detected phase detection voltage, discharges through the discharge switch, and the LED display screen displays the test results; Step 6, one of the dual ground wire jacks is grounded, and the other is connected to the E-pole jack of the insulation tester. The shifter is turned to the ALL position, and the DC voltage converter outputs DC high voltage. The converter and the analog-to-digital converter convert the analog current signal returned by the detection into a digital voltage signal, which is input into the single-chip microcomputer through the SPI bus. If there is a defect in the insulation of a phase of the tested cable, the signal fed back to the MCU by this phase is abnormal. After the MCU controls the DC voltage converter to reduce the voltage, it outputs a signal through the IO interface to cut off the detection voltage of the tested phase, and the remaining phases continue to perform the boost test. After the test is completed, discharge is performed through the discharge switch, and the LED display screen displays the test results; Step 7, one of the double ground wire sockets is grounded and the other is disconnected, the interphase cable detection socket of one phase of the two-phase cable to be tested is connected to the E-pole socket of the insulation tester, the shifter is shifted to the corresponding gear of the other phase of the two-phase cable to be tested, the DC voltage converter outputs DC high voltage, the converter and the analog-to-digital converter convert the analog current signal returned by the detection into a digital voltage signal, which is input into the microcontroller through the SPI bus. After the test is completed, the MCU controls the DC voltage converter to step down the voltage, outputs a signal through the IO interface to cut off the detection voltage of the cable to be tested, discharges through the discharge switch, and the LED display screen displays the test results.

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