QDB-101DC Grounding Intelligent Quick Finder

I. Overview

DC system insulation fault, DC crossover fault, and AC crossover fault are types of faults that are prone to occur and pose a significant threat to the normal operation of the power system.

In order to better assist on-site maintenance personnel in quickly and accurately identifying DC faults, our company has worked hard for many years, summarized a large amount of on-site experience, and developedDC grounding fault locator.

DC grounding fault locatorBy using a high-precision current clamp meter and utilizing the difference in DC current in the fault circuit for fault detection and localization, the system can quickly identify and locate faultsFFTThe introduction of transformation technology into DC fault finding equipment can detectEach voltage level（24V，48V，110V，220V）Various insulation faults, DC crossover faults, and AC crossover faults in DC systems.

With the increasing demand for safe operation in the power system, the requirements for various types of DC fault detection in the power system will also become higher. Therefore, high-precision and insulation trend analysis will become the new generation of requirements for the power systemDC grounding fault locatorThe basic requirements.

A new type of DC fault based on frequency modulation and amplitude modulation technology baseYuPrinciple of DC current difference detectionnew-typeDC grounding fault locatorIntroducing FastFFTTransformation technology,By analyzingdetection volumeDetailed analysis of amplitude frequency characteristics balances DCgroundingRegarding the safety and sensitivity of fault diagnosisofContradiction, direct currentgroundingFault technology has reached a new heightIt has a wide range of application prospects.

2、 Device structure and principle

2.1 Device composition

DC grounding fault locatorIt consists of three parts: system analyzer, branch detector, and collector, as shown in the following diagram:

2.2 Device principle

2.2.1 Principle of insulation fault diagnosis

The system analyzer is connected to the tested DC bus and uses the ping-pong principle to calculate the balance bridge resistance and ground insulation resistance of the tested DC system. If there is an insulation fault in the tested DC system, the system analyzer inputs a detection bridge with a set frequency and amplitude to the DC system. The detector locates the ground fault point by detecting the current signal in each branch. The detection principle is shown in the following diagram:

The feeder line in the picture1For normal feeders, feedersnFor feeders with negative to ground insulation faults,For insulation fault resistance,RBalance the bridge for the system.

After the analyzer detects an insulation fault, it applies a detection bridge to the DC system, which is shown in the diagramETheFThe input of the detection bridge causes a known frequency periodic change in the DC system's ground voltage. Let the frequency of this change beThe amplitude of the change in ground voltage generated by the DC system is, then flow throughThe amplitude of the current change on top isChange frequency and detection bridge input frequencySame.

The detectors are located separatelyA，B，CConduct testing at the location. atAThe change in current signal cannot be detected at this location, indicating that the feeder line1There is no insulation fault, inBThe change in current signal can be detected at this location, indicating that the feeder linenThere is an insulation fault, butCThe change in current signal cannot be detected, thus it can be determined that the insulation fault point is locatedBTheCbetween.

2.2.2 DC Crossover Search for Originreason

The system analyzer is connected to the two DC busbars being tested, and a detection bridge is switched to one of the busbars. The voltage change waveforms of the two busbars are compared to determine whether there is a ring network fault or insulation fault in the system based on the voltage change relationship. If there is a ring network fault or insulation fault, the detection bridge is continuously started for the branch detector to locate the ring network fault point.

When there is a ring network fault in two branches, a detector and collector can be used to detect each branch that may have a ring network fault one by one. Based on the waveform and direction displayed by the detector, the final search for the ring network fault point can be achieved.

The schematic diagram of DC crosstalk detection is as follows:

2.2.3 Principle of AC surge detection

The system analyzer is connected to the tested DC bus and detects the AC voltage component in the DC system in real time. If the AC voltage component in the DC system exceeds the set value, it is determined that there is an AC surge fault in the DC system.

The process of finding the fault point of AC surge is the same as the process of finding the insulation fault point.

3、 Functional Features

3.1 Introduction to Main Functions

（1) The system has the function of measuring ground voltage. The instrument can measure the system's positive ground voltage, negative ground voltage, and system voltage, and can achieve a voltage monitoring range of 0-300V;

（2) System insulation impedance measurement function, the instrument can measure the system's positive to ground insulation impedance, negative to ground insulation impedance, and balance bridge size detection,measurement range0—999.9KΩ；

（3) The AC surge detection function allows the instrument to detect AC surge faults in the DC system and measure the AC voltage value entering the DC system, with a measurement range of 0-280V;

（4) System distributed capacitance measurement function, the instrument can measure the distributed capacitance of the system and display it in real time;

（5) Ring network detection and positioning function, the instrument can detect various ring network faults in two sections of the busbar, including positive pole ring, negative pole ring, two pole ring, and opposite pole ring, and can locate the ring network fault point through waveform display and direction display;

（6) The device has functions of amplitude modulation, reset, current waveform selection, and working mode selection, which can achieve the search and location of high resistance ring network faults.

（7) Branch insulation impedance measurement and insulation fault location function, the instrument measures the insulation impedance of each branch to ground, and can locate the insulation fault point through waveform display and direction display;

（8) Fault current spectrum analysis function, the device achieves frequency spectrum analysis of current changes through fast FFT transformation, effectively extracts the signal amplitude of the measured current frequency point, and improves detection accuracy;

（9) The ammeter function allows the device to be used as a high-precision ammeter, with a current measurement resolution of up to 0.01mA;

（10) The waveform curve display and direction display function, when using the detector to detect the measured branch, the display screen will display the current changes of the measured branch in the form of waveform curves, which is convenient for users to quickly and accurately find the fault point. When there are ring network faults and grounding faults, the direction of the fault point will be displayed.

3.2 Equipment Features

（1) High reliability design

The device is importedA 32-bit microcontroller is used as the main system, and the hardware design strictly follows the relevant standards of power and electromagnetic compatibility. Multiple redundant methods are adopted internally to ensure the reliability of the device and the tested equipment.

（2) Precision material selection

The device uses a high-precision collector as the signal acquisition unit, and the voltage sampling adopts a high-precision imported analog-to-digital conversion chip, ensuring accurate measurement of voltage and impedance;

（3) Humanized human-computer interaction interface

Both the "analyzer" and "detector" use TFT LCD displays for users to view information;

The operation is simple and fast, and when detecting different branches, only one press of the start button is needed to complete it;

The test results are displayed intuitively and clearly, and can be presented to users in various display forms, including grounding status, waveform curve, insulation level, insulation impedance, leakage current size, direction information, etc.

（4) Intelligent detection and recognition system

The analyzer can automatically identify the system voltage level;

The analyzer can determine the category of ring network faults;

After synchronizing the information of the "detector" and "analyzer" once, it is not affected by the detection distance;

When the "detector" is used for detection, the collector can clamp a single power cord or multiple power cords to improve detection efficiency;

After the "detector" completes the detection, if there is a ring network or insulation fault in the tested branch, it will determine the direction information of the fault point relative to the test point.

（5) Complete testing functions and fault handling capabilities

The "analyzer" and "detector" are equipped with wireless data transmission modules for communication, with complete testing functions and display information, and can handle various ring network and insulation fault situations in DC systems.

“analyzer”possessMultiple combination working mode selection functions of "amplitude modulation", "waveform", and "mode" can adapt to various complex application environments.

（6）高安全性

The device uses microampere level detection signals combined with high-resolution DC detection collectors to achieve fault detection and localization, without any impact on the DC system.

QDB-101DC Grounding Intelligent Quick Finder

4、 Main technical indicators

4.1 Main technical indicators of the analyzer

Usage environment

l Working power supply:DC22V-300V,

l Ambient temperature-20℃—55℃

l relative humidity0—90%

DC voltage measurement

l DC voltage measurement range:22-300V

l Resolution of DC voltage measurement:0.1V

l Accuracy of DC voltage measurement:220V DC power supply system (180V~286V) 110V DC power supply system (90V~143V)±0.5%

AC voltage measurement

l Measure AC and DC surge voltage:10-280v

l AC voltage measurement resolution:0.1V

l Accuracy of AC voltage measurement:±5%

Insulation resistance measurement

l Measurement range of insulation resistance:0-999.9KΩ；Resolution of insulation resistance measurement:0.1KΩ

l Measurement accuracy of insulation resistance:Ri < 10KΩ Display specific numerical values

10KΩ≤Ri≤500KΩ ±5%

Detection bridge amplitude adjustment range:0mA，0.25mA，0.5mA ，1mA，2mA

l Range of resistance values for the detection ring network:Within 50K Ω

System distributed capacitance measurement

Measurement range of system distributed capacitance:0-999.9uF Accuracy C<10uF or C>200uF: Display specific values; 10uF≤C≤200uF:±10%or±3uF；

Selection of waveform types for detection: sine wave, square wave；

l beUnified ground capacitance measurement:0－1000kΩ

Selection of waveform types for detection: sine wave, square wave

Working mode: forced signal start, automatic signal start

Display medium and resolution:TFT,320x240

4.2 Main technical indicators of the detector

Insulation resistance measurement

l Measurement range of insulation resistance: 0-500KΩ

l Resolution of insulation resistance measurement:0.1KΩ

l Measurement accuracy of insulation resistance:Ri <10KΩ Display specific numerical values

10KΩ≤Ri≤500KΩ:±10%

Spectrum analysis scope

l Number of channels for spectrum analysis:1

l Spectrum analysis frequency range:0.125-12.5Hz

l frequency resolution: 0.125Hz

Current waveform display period:8s；

Detectable feeder current range:0—2A；

Current measurement range:-100—+100mA；

Current measurement resolution: 0.01 mA

Display medium and resolution:TFT,320x240

4.3 Wireless Communication Technology Indicators

l Speed:2Mbps， Due to the short transmission time in the air, the collision phenomenon in wireless transmission is greatly reduced

l Multi frequency points:125 frequency points, meeting the needs of multi-point communication and frequency hopping communication

l Ultra small: Built in2.4GHz antenna, compact size, 15x29mm

l Low power consumption: When operating in response mode communication, fast air transmission and startup time greatly reduce current consumption.

5、 Usage method

5.1 Wiring

5.1.1 Analyzer wiring

The analyzer is equipped with two connecting plugs, of whichSection I includes a red connecting line, a black connecting line, and a yellow connecting line; Section II includes a red connecting line and a black connecting line.

Insert one end of the red, yellow, and black connector sockets into the analyzer according to the color markings providedI-section plugLocation;

Disconnect the power switch and connect the other end of the red, yellow, and black wires as follows:

Connect the red clip of the red connecting wire to theAt the positive pole of section I busbar;

Connect the yellow clip of the yellow connecting wire to theGround of section I busbar;

Connect the black clip of the black connecting wire to theAt the negative pole of section I busbar;

If you want to detect DC crosstalk, you need to connect the equipped red and black wires to the device and system as follows:

Insert one end of the red and black connecting wires into the analyzer socket according to the color markingsAt the plug of section II;

Connect the red clip of the red connecting wire to theAt the positive pole of section II busbar;

Connect the black clip of the black connecting wire to theAt the negative pole of section II busbar;

As shown in the following diagram:

Do not connect the circuit when not conducting DC cross current detectionTwo connecting wires of the II section busbar.

5.1.2 Connection between detector and collector

Fully chargedInstall 4 No. 5 rechargeable batteries into the battery compartment of the detector;

Connect one end of the collector aviation plug to the detector socket.

5.1.3 Power on

After checking the wiring of each part, turn on the power switch of the analyzer. The power indicator light and LCD screen are both illuminated, and the device enters the working state. If there is no grounding in the system, the analyzer's normal indicator light is on. If there is a positive grounding, the positive grounding indicator light is on. If there is a negative grounding, the negative grounding indicator light is on.

5.2 Operation

5.2.1 Analyzer Operation

There are four buttons on the analyzer panel that can adjust the operating parameters of the analyzer. The button arrangement diagram is as follows:

amplitude modulationThis button can be used to adjust the amplitude of the current signal, which can be within the range ofCycle settings between 0mA, 0.25mA, 0.5mA, 1mA, and 2mA, with a default of 1mA when turned on(Default 2mA for 24V DC system).

resetThis button can be used to achieveProgram reinitializes and runs again.

waveformThis button allows you to select the current waveform, which can be either a square wave or a sine wave,When set to square wave, the waveform displayed in the analyzer status bar is“”When set to sine wave, the analyzer status bar displays as“”The default startup is“”.

patternThis button can be used to select the working mode of the analyzer. The analyzer can be set to automatic mode or forced mode. When set to automatic mode, the analyzer status bar displays the mode as“Auto”， When set to forced mode, the analyzer status bar mode displays "Force", and the default startup is“Auto”.

Explanation on Forced Mode and Automatic ModeWhen the analysis ceremony is working in automatic mode, only theAfter a certain deviation in ground voltage occurs in the I-section busbar system, the detection bridge is activated for fault diagnosis. When the system returns to normal, the operation of the detection bridge will be automatically stopped; When the analyzer operates in forced mode, it will actively start the detection bridge for fault detection. After the detection is completed, regardless of whether there is a grounding or ring network fault, the detection bridge will be put into the system ground.

5.2.2 Detector Operation

The detector panel has three buttons, namelyAll detection functions of the detector can be achieved through these three buttons: "Power", "Function", and "Test". The detector is compatible with both D-type and A-type collectors. Please pay attention to the type of collector connected and the corresponding analyzer for different collector types when using it“”And“”Waveform state.

power supplyPower switch button;

Function:Press the function key to select the desired test function item;

testAfter selecting the desired function, press this key to start testing.

5.3 Display

5.3.1 Analyzer Display

After booting up, the analyzer enters the main interface display, which has a display screen with the following content:

When the analyzer is turned on, it will test the system. After the test is completed, the main interface of the analyzer will display the current system voltage, positive and negative ground voltages, positive and negative ground insulation resistance, distributed capacitance, AC surge status, and whether there is a ring network fault.

If the analyzer detects a positive or negative insulation fault in the system, the correspondingThe "positive ground" or "negative ground" fault indicator light flashes.

If the analyzer detects a ring network fault in the system, thenThe "positive ground" and "negative ground" fault indicator lights flash simultaneously.

When the indicator light flashes, it indicates that the analyzer is switching the detection bridge to the ground of the tested system according to the set signal amplitude and frequency. When the indicator light is in a non flashing state, the analyzer has not switched the detection bridge.

After startup, the analyzer will actively start the detection bridge to test the system.

The main interface status bar displays the current working status of the system:

currentThe value indicates that the analyzer is operating in the current detection bridge input size mode, can be set through the "amplitude modulation" key;

frequency: System default display0.25HZ；

waveformDisplay the waveform type of the current detection bridge used by the analyzer, which can be accessed throughSet the "waveform" key;

patternDisplay the current working mode of the analyzer, which can be accessed throughSet the "Mode" button;

5.3.2 Detector Interface Operation and Display

Fully chargedAfter installing the 5th rechargeable battery into the detector battery compartment and connecting the collector to the detector, turn on the "power" switch of the detector to enter the detector function selection interface:

In this interface, users can access it throughThe "Function" button switches between three functions: "Fault location waveform analysis", "Fault signal spectrum analysis", and "DC leakage current testing". When the symbol "◇" is located before the function item, it indicates that the function item is in an active state.

The status bar displays the type of collector currently connected, the waveform state formed when the analyzer is put into the detection bridge, the voltage amplitude, the frequency of the detection bridge, the communication status, the battery level, and other information. The types of collectors are'N' indicates that no collector is connected, 'D' indicates that a D-type collector is connected, and 'A' indicates that an A-type collector is connected; Waveform status display:“”The waveform formed when the current analyzer is put into the detection bridge is a square wave, “”The waveform formed when the current analyzer is put into the detection bridge is a sine wave.

Select the function item, clamp the detector collector into the tested branch, and pressThe "Test" button can be used to detect the tested branch by pressing the selected function.

Attention: When usingWhen the A-type collector is used for detection, the waveform state of the analyzer must be adjusted to“”When using a D-type collector for detection, the waveform state must be adjusted to“”.

The fault location screen is as follows:

This screen displays information such as the current waveform of the tested circuit, the magnitude of insulation impedance, and the direction of the fault point. The left image in the above picture is connectedThe display interface for detecting faulty branches in the A-type collector is shown on the right, which is connected to the display interface for detecting faulty branches in the D-type collector.

For the detection of faulty branches, it can be seen from the figure that the detector detected the same frequency signal as the analyzer and the current information of the same frequency as the input detection bridge, and displayed it in waveform form. After the detection is completed, the direction of the fault point is indicated. The direction of the fault point is displayed as'Same direction' or 'reverse direction' refers to the direction relative to the collector identification direction of the detection point. If in the same direction, it indicates that the direction of the fault point is the same as the direction identified by the collector; On the contrary, the opposite is true. For pure resistance circuits, the synchronous point arrow indicates the peak or valley position of the current waveform; For circuits with distributed capacitance, indicate between the peaks and valleys of the current waveform.

The fault current spectrum analysis consists of two images. The left image in the upper figure is the original current waveform of the fault current spectrum, and the right image is the waveform of the fault currentFFT transformed spectrogram.

This function first displays the original current signal as a waveform, and then performs fast processingFFT transform, display the frequency spectrum of the fault current, and calculate the frequency points of the current amplitude and the amplitude of the fault current.

The DC current test screen is as follows:

Press on this interfaceThe "Test" button can reset the current test current to zero.
The 'current measurement' function is only suitable for using DtypeCollector, if usedAtypecollector，The interface will prompt“Please answerD-typeClamp table”It is necessary to include AtypeReplace the collector withDtypePerform current measurement operation after the collector.

6、 Precautions

（1）Due to the fact that the device is a precision instrument, it should be handled with care during transportation, use, and storage. All components should be protected from strong vibrations such as dropping and falling to ensure high precision during use.

（2）Before conducting testing after each turn on of the detector, there should be a data synchronization between the detector and the analyzer. During synchronization, it is necessary to maintain a connection between the detector and the analyzer5Within a distance of meters, after data synchronization is completed, the detector can be kept away from the analyzer, but when in use, please keep the detector turned on after data synchronization.

（3）After each use, the battery of the detector should be removed from the battery compartment and fully charged for the next use. When the detector's battery is low, the battery should be replaced immediately to ensure smooth testing.

（4）The analyzer must be connected before the tested branch (according to the current flow direction), with the positive, negative, and ground wires respectively connected to the DC positive bus, negative bus, and ground wire to ensure good grounding of the ground wire.

（5）Due to the high sensitivity of the collector, it should be kept in a stationary state during detection to avoid affecting the accuracy of the detection.

（6）DetectoruseDtypeDuring collector detection,If it appearsPlease ensure that the current of the measured branch does not exceed the value of 'saturation of clamp meter'1AIf it exceeds this value, please clamp both positive and negative wires.

（7）Due toDtypeThe collector adopts a staggered process of teeth. When in use, the collector should be opened and the wire clamped. The collector should be closed naturally. If it cannot be closed naturally, it should be carefully observed and closed without external force. If it is forcibly closed, it will cause the teeth on the jaws to be misaligned and not tightly closed, damaging the collector.