CN103135038B - Straight-flow system exchanges crosstalk and insulation fault monitoring selection method - Google Patents

Abstract

The present invention relates to straight-flow system and exchange crosstalk and insulation fault monitoring selection method, comprise host computer, monitoring device, sampling system and current sensor, by extracting AC compounent effective value, extract the ripple peak-to-peak value in straight-flow system, alternating current-direct current component is adopted to be separated digital filtering technique, direct current detection technology, RS485 isolated communication technology and quick FFT converter technique, real-time monitoring system bus combined-voltage over the ground, ripple voltage peak-to-peak value also can alarm, each loop current information that real-time reception data acquisition unit is uploaded, and carry out intellectual analysis by mode-matching technique, calculate impedance ground, the feature status information in every bar loop and the built-in characterization rules of system are carried out artificial intelligence pattern's coupling, to the interchange crosstalk fault that system exists, ripple peak-to-peak value Monitoring Data, earth fault and insulation fault loop state information, loop information etc. are shown on liquid crystal display, operation maintenance personnel is helped accurately to understand current state, fix a breakdown rapidly.

Description

Line Selection Method for AC Series and Insulation Fault Monitoring in DC System

technical field

The invention relates to a DC system detection method, in particular to a DC system AC series and insulation fault monitoring line selection method.

Background technique

The AC series fault in the DC system refers to the situation that the phase line in the AC power is directly or indirectly connected to the positive or negative pole of the DC system. AC series faults in DC systems are usually caused by the following two reasons: 1. Misoperation by maintenance personnel; 2. AC series faults caused by equipment with AC power supply in the DC system. AC series faults in DC systems are different from ordinary ground faults. When common ground faults occur in DC systems, single-point grounding usually does not cause harm, but only when two-point grounding faults occur can there be protective misoperations. Or refuse to operate, so after a small ground fault occurs, the maintenance personnel still have sufficient time to deal with it. However, once an AC series fault occurs in the DC system, it may cause a malfunction of the protection, and the probability of this hazard is far greater than that of a common ground fault. Therefore, once an AC series fault occurs in the system, it needs to be dealt with immediately. The sampling of DC voltage by traditional insulation monitoring devices is usually the voltage averaging method. There is no problem in sampling when there is no AC series current, but the DC sampling is not accurate after AC series current occurs.

In the existing detection equipment, there are problems such as the inaccurate positioning of the AC series circuit in the DC system, the inaccurate collection of the voltage of the DC system in the case of AC series, and the difficulty in selecting lines for AC series and insulation faults in the DC system.

Contents of the invention

The purpose of the present invention is to address the above existing problems and deficiencies, to provide a DC system AC series and insulation fault monitoring line selection method, effectively solve the AC series in the DC system can not be found and processed in time, the AC series circuit in the DC system Inaccurate positioning, inaccurate collection of DC system voltage in the case of AC series current, difficult line selection for AC series current and insulation faults in the DC system.

Technical scheme of the present invention is realized like this:

A DC system AC series and insulation fault monitoring line selection method, comprising:

Host computer, monitoring device, sampling system and DC sensor, the monitoring device includes a main controller, the main controller is provided with a liquid crystal screen, the main controller is the core control unit of the whole system, and is provided with a DA output module, a data storage module, LCD display module, keyboard input module, main interface for monitoring information display and setting information input; DC sensors are installed at each outlet circuit of each LCD screen (generally at the exit of each circuit insurance); the sampling system includes a data collector, The data collector is located between the main controller and the DC sensor, and the installation location can be selected according to the needs; the main controller and the data collector adopt two connection modes of star connection or chain connection, and each data collector can be connected with the main controller. The controller is directly connected through the RS485 bus, or indirectly connected with the main controller through the cascade port of another data collector, which is convenient for installation and wiring; the communication between the main controller and the data collector is controlled by the data collector. The unique address code is determined, which has nothing to do with the physical location of the data collector, which brings a high degree of flexibility to the on-site system configuration; the main controller and the data collector can be hot-swappable, and the main controller can automatically identify the data collector, no need Manual setting; each data collector can be connected with multiple (8) DC sensors. When the DC sensor is connected to the data collector through a dedicated interface, the data collector can automatically identify the DC sensor without manual settings;

To extract the effective value of the AC component, the monitoring device uses a high-pass filter circuit to extract the AC voltage to the ground in the DC system, and then converts the AC voltage into a DC voltage through the true effective value conversion chip, and sends it to the processor sampling system;

Extract the peak-to-peak ripple in the DC system. The monitoring device uses a high-pass filter circuit to extract the AC voltage to ground in the DC system. The peak-to-peak AC ripple is extracted through an independent high-speed sampling circuit and sent to the processor for analysis. High-speed sampling circuit The bandwidth is greater than 20MHz;

AC and DC component separation digital filtering technology is adopted, specifically, the AC and DC components are separated by high-pass and low-pass filter circuits inside the monitoring device, and the DC voltage is biased and sent to the processor sampling system;

Using DC leakage current detection technology, specifically, after an AC series fault occurs in the DC system, a large amount of power frequency AC voltage appears on the system, and the DC voltage drops from one pole to the ground of the series power; on the feeder, a DC current is generated through the series circuit. Leakage current, through the real-time monitoring of the leakage current, the line selection function of the AC series circuit can be realized; the line selection of the series circuit, when the AC series fault occurs in the DC system, the AC series circuit shows an obvious ground fault , The AC series fault monitoring system is equipped with a high-precision DC current sensor on each feeder to be tested, and the DC current sensor has a good filtering effect on AC signals;

Using RS485 isolation communication technology and fast FFT transformation technology, in the signal mode, the monitoring device applies a low-frequency small signal source to the DC system in the form of a constant current source through the DA conversion module and the constant current signal output module. The signal frequency is 0.125 Hz, 0.25 Hz, 0.5Hz, and 1Hz are optional, and the waveform is sine wave. The monitoring device collects the ground voltage and extracts the signal voltage amplitude at the signal frequency point through fast FFT transformation; the data collector performs FFT transformation on the leakage current of each feeder and extracts The signal current amplitude at the signal frequency point is isolated and uploaded to the monitoring device through RS485, and the voltage amplitude and current amplitude of the monitoring device calculate the insulation resistance of each monitoring circuit;

The main controller monitors the voltage of the system bus to ground in real time, including system voltage, positive to ground voltage, negative to ground voltage and AC series voltage and displays it in real time. When the DC system fails, the system voltage is too high or too low to exceed the preset setting value, or when the AC voltage exceeds the preset setting value, the main controller LCD will display alarm information, and the voltage over-limit indicator and buzzer will alarm at the same time. The alarm information can also be uploaded to the integrated automation system or through the YX switch and RS485 interface Scheduling automation system upper computer;

The main controller monitors the ground impedance of the system bus in real time, including the positive and negative ground resistances and displays them in real time. When the DC system fails and the positive and negative ground voltages are no longer balanced and exceed the preset setting value, the main controller The LCD screen displays the alarm information, the system grounding indicator and the buzzer alarm at the same time, and the alarm information can also be uploaded to the host computer of the integrated automation system or dispatching automation system through the YX switch and RS485 interface;

The main controller receives the characteristic state information of each loop uploaded by the data collector in real time, and conducts intelligent analysis through the pattern matching technology to distinguish different grounding states, and eliminates the influence of system charging pulse interference, fluctuation level interference and loops, Finally, accurately judge the grounding loop and calculate the grounding impedance. The grounding impedance value is displayed on the LCD screen and can be uploaded to the host computer of the integrated automation system or dispatching automation system through the RS485 interface;

The main controller matches the characteristic state information of each loop with the built-in characteristic rules of the system for artificial intelligence mode matching, and detects fault loops, abnormal loops, loops with dual power supplies for each other in the system, and loops with loops that exist in the system. The loop and the loop grounding loop provide complete loop status information and display it on the LCD screen, effectively helping the operation and maintenance personnel to accurately understand the current status of the DC system and quickly troubleshoot.

Further, the method for extracting the AC and DC components in the present invention: effectively proposing the AC components in the DC system is the focus of the present invention, and selecting the true effective value sampling circuit to extract the AC components in the DC. The flow chart of AC component extraction in DC is shown in Figure 2 of the manual. The true RMS extraction circuit can accurately convert AC voltage into DC level. After the sampling system completes 10,000 sampling averages per second, the sampling data is sent to the processor for analysis, and the processor displays the calculation results on the man-machine interface and gives an audible and visual alarm. In addition to the accurate acquisition of AC voltage, the accurate measurement of DC voltage is also very important for the AC series fault monitoring system. For insulation monitoring devices without AC series fault detection, the DC voltage acquisition is usually the average voltage method. Once the AC component is connected in series in the DC system, the DC voltage sampling deviation is large, resulting in inaccurate grounding impedance measurement, resulting in False positive or not.

Further, the present invention adopts multi-stage filtering and voltage bias method in the DC sampling of the AC series fault monitoring system to ensure the accuracy of the DC voltage sampling during the AC series fault. The block diagram of the implementation principle is shown in Figure 3 of the manual. When there is AC power in series in the DC system, the second-order filter circuit filters most of the AC signals in stages, and the AC voltages that must be compared are all positive after passing through the DC bias circuit. After long-term averaging, the system filters the symmetrical AC signal, and finally subtracts the offset voltage to accurately restore the real DC voltage.

Furthermore, in the line selection of the series circuit of the present invention, when an AC series fault occurs in the DC system, the AC series circuit exhibits an obvious grounding fault. The AC series fault monitoring system is equipped with a high-precision DC current sensor on each feeder to be tested. The DC leakage current sensor has a good filtering effect on AC signals. As shown in Figure 4 of the manual, middle feeder 1 is a normal feeder, feeder n is an AC series fault circuit, Rx is the internal resistance of the series, and R is the system balance bridge. Assuming that the load current is I _l , the system positive-to-ground voltage is Vcc, and the negative-to-ground voltage is Vss, then in feeder 1, I ₁ =I ₂ =I _l , and the measured current at A is I ₁ -I ₂ = 0; in feeder n, I ₃ =I ₄ =I _l , , the measured current at B is I ₅ , and the internal resistance of the AC series can be calculated according to the system voltage and sensor current.

The system of the invention has the following functions: real-time monitoring of system voltage and alarming, real-time monitoring of system insulation and alarming, real-time grounding loop detection, system loop detection and diagnosis, loop insulation classification early warning and grounding history record analysis.

Voltage monitoring: The main controller (host) monitors the voltage of the system busbar to ground in real time, including system voltage, positive to ground voltage, negative to ground voltage and AC series voltage, and displays them in real time. When the DC system fails, the system voltage is too high or too low to exceed the preset setting value, or the AC voltage exceeds the preset setting value. The alarm information can also be uploaded to the upper computer of the integrated automation system or dispatching automation system through the YX switch and RS485 interface.

Insulation monitoring: The host monitors the impedance of the system bus bar to ground in real time, including the positive resistance to ground and the negative resistance to ground and displays them in real time. When the DC system fails and the positive and negative ground voltages are no longer balanced and exceed the preset setting value, the main controller (host) LCD will display an alarm message, and the system grounding indicator and buzzer will alarm at the same time. The alarm information can also be uploaded to the upper computer of the integrated automation system or dispatching automation system through the YX switch and RS485 interface.

Grounding detection: The main controller (host) receives the characteristic status information of each circuit uploaded by the data collector (slave machine) in real time, and conducts intelligent analysis through pattern matching technology to distinguish different grounding states, eliminate system charging pulse interference, and fluctuations The interference caused by leveling and the impact of the loop, and finally the ground loop can be accurately judged and the ground impedance can be calculated. The grounding impedance value is displayed on the LCD screen, and can be uploaded to the host computer of the integrated automation system or dispatching automation system through the RS485 interface.

Loop diagnosis: Power DC loops are ubiquitous and cause great interference to the location of ground fault points. The main controller (host) matches the characteristic status information of each loop with the built-in characteristic rules of the system for artificial intelligence mode matching, and introduces the concept of loop index for the first time, so as to analyze the fault loops, abnormal loops, and system dual loops existing in the system. The power supplies are mutually backup loops, loops with loops, and loop ground loops, providing complete loop status information and displaying it on the LCD screen. It can effectively help operation and maintenance personnel to accurately understand the current state of the DC system and quickly troubleshoot.

Insulation early warning: Since the detection accuracy of the main controller (host) is extremely high, it can reach more than 500K, so the long-term change trend can be judged by detecting the ground impedance of the ungrounded loop, and the early warning information of the loop ground can be provided. Insulation reduction warning and loop matching monitoring provide effective means for system diagnosis.

History record: The system grounding record will be automatically saved in EEPROM for reference. The record includes the date and time of grounding, grounding impedance, grounding loop and other information and can be saved after power failure. The historical record also includes the date and time of the AC series power, the voltage of the series power and other information, which can be saved after power failure.

The DC system AC series fault monitoring and line selection device of the present invention not only detects the common grounding fault of the DC system, but also monitors the AC voltage component in the DC system in real time. The line selection function of the series circuit helps the maintenance personnel to quickly solve the fault and greatly improves the safety and stability of the DC system.

The invention can effectively solve the problem that the AC series current in the DC system cannot be detected and processed in time, solve the problem that the AC series circuit in the DC system cannot be accurately positioned; solve the problem of inaccurate collection of the voltage of the DC system under the condition of the AC series current; solve The problems of AC series current and insulation fault line selection in the DC system are solved.

The present invention will be further described below in conjunction with the accompanying drawings.

Description of drawings

Fig. 1 is a schematic diagram of the system structure of the present invention;

Fig. 2 is the flow chart of extracting the AC component in the direct current of the present invention;

Fig. 3 is the block diagram of the implementation of the multi-stage filtering and voltage bias method adopted in the DC sampling of the AC series fault monitoring system of the present invention;

Fig. 4 is a schematic diagram of line selection of the series circuit of the present invention.

Detailed ways

As shown in Figures 1-4, the present invention is a DC system AC series and insulation fault monitoring line selection method, including:

Host computer, monitoring device, sampling system and DC sensor, the monitoring device includes a main controller, the main controller is equipped with an LCD screen, the main controller is the core control unit of the whole system, and has a main interface for monitoring information display and setting information input ;The DC sensor is installed at each outlet circuit of each feeder panel (generally at the exit of each circuit breaker); the sampling system includes a data collector, and the data collector is located between the main controller and the DC sensor, and the installation location is selected according to the needs; The main controller and the data collector adopt two connection modes of star connection or chain connection, and each data collector can be directly connected with the main controller through the RS485 bus, or through the stage of another data collector. The connection port is indirectly connected to the main controller, which is convenient for installation and wiring; the communication between the main controller and the data collector is determined by the unique address code of the data collector, which has nothing to do with the physical location of the data collector, which brings great convenience to the field system configuration. Comes with a high degree of flexibility; the main controller and data collector can be hot-swappable, the main controller can automatically identify the data collector, without manual settings; each data collector can be connected to 8 DC sensors, when the DC sensor After connecting to the data collector through a dedicated interface, the data collector can automatically identify the DC sensor without manual settings;

To extract the effective value of the AC component in the DC system, a high-pass filter circuit is used inside the monitoring device to extract the AC voltage to the ground in the DC system, and then the AC voltage is converted into a DC voltage by the true effective value conversion chip, and sent to the processor sampling system ;

To extract the peak-to-peak value of the AC component ripple in the DC system, a high-pass filter circuit is used inside the monitoring device to extract the AC voltage to ground in the DC system, and then the peak-to-peak value of the ripple in the DC system is extracted through an independent high-speed sampling module;

AC and DC component separation digital filtering technology is adopted, specifically, the AC and DC components are separated by high-pass and low-pass filter circuits inside the monitoring device, and the DC voltage is biased and sent to the processor sampling system;

Using DC leakage current detection technology, specifically, after an AC series fault occurs in the DC system, a large amount of power frequency AC voltage appears on the system, and the DC voltage drops from one pole to the ground of the series power; on the feeder, a DC current is generated through the series circuit. Leakage current, through the real-time monitoring of the leakage current, the line selection function of the AC series circuit can be realized; the line selection of the series circuit, when the AC series fault occurs in the DC system, the AC series circuit shows an obvious ground fault , The AC series fault monitoring system is equipped with a high-precision DC current sensor on each feeder to be tested, and the DC current sensor has a good filtering effect on AC signals;

RS485 isolation communication technology and fast FFT transformation technology are adopted. In the signal mode, the monitoring device applies a low-frequency small signal source to the DC system in the form of a constant current source through the DA conversion module and the constant current signal output module. The signal frequency is 0.125Hz, 0.25 Hz, 0.5Hz, and 1Hz are optional, and the waveform is sine wave. The monitoring device collects the ground voltage and extracts the signal voltage amplitude at the signal frequency point through fast FFT transformation; the data collector performs FFT transformation on the leakage current of each feeder and extracts The signal current amplitude at the signal frequency point is isolated and uploaded to the monitoring device through RS485, and the voltage amplitude and current amplitude of the monitoring device calculate the insulation resistance of each monitoring circuit;

The main controller monitors the voltage of the system bus to ground in real time, including system voltage, positive to ground voltage, negative to ground voltage and AC series voltage and displays it in real time. When the DC system fails, the system voltage is too high or too low to exceed the preset setting value, or when the AC voltage exceeds the preset setting value, the main controller LCD will display alarm information, and the voltage over-limit indicator and buzzer will alarm at the same time. The alarm information can also be uploaded to the integrated automation system or through the YX switch and RS485 interface Scheduling automation system upper computer;

The main controller monitors the ground impedance of the system bus in real time, including the positive and negative ground resistances and displays them in real time. When the DC system fails and the positive and negative ground voltages are no longer balanced and exceed the preset setting value, the main controller The LCD screen displays the alarm information, the system grounding indicator and the buzzer alarm at the same time, and the alarm information can also be uploaded to the host computer of the integrated automation system or dispatching automation system through the YX switch and RS485 interface;

The main controller receives the characteristic state information of each loop uploaded by the data collector in real time, and conducts intelligent analysis through the pattern matching technology to distinguish different grounding states, and eliminates the influence of system charging pulse interference, fluctuation level interference and loops, Finally, accurately judge the grounding loop and calculate the grounding impedance. The grounding impedance value is displayed on the LCD screen and can be uploaded to the host computer of the integrated automation system or dispatching automation system through the RS485 interface;

The main controller matches the characteristic state information of each loop with the built-in characteristic rules of the system for artificial intelligence mode matching, and detects fault loops, abnormal loops, loops with dual power supplies for each other in the system, and loops with loops that exist in the system. The loop and the loop grounding loop provide complete loop status information and display it on the LCD screen, effectively helping the operation and maintenance personnel to accurately understand the current status of the DC system and quickly troubleshoot.

The system of the invention has the following functions: real-time monitoring of system voltage and alarming, real-time monitoring of system insulation and alarming, real-time grounding loop detection, system loop detection and diagnosis, loop insulation classification early warning and grounding history record analysis.

Voltage monitoring: The main controller monitors the voltage of the system busbar to ground in real time, including system voltage, positive to ground voltage, negative to ground voltage and AC series voltage, and displays them in real time. When the DC system fails, the system voltage is too high or too low to exceed the preset setting value, or the AC voltage exceeds the preset setting value. The alarm information can also be uploaded to the upper computer of the integrated automation system or dispatching automation system through the YX switch and RS485 interface.

Insulation monitoring: The main controller monitors the impedance of the system busbar to ground in real time, including the positive resistance to ground and the negative resistance to ground and displays them in real time. When the DC system fails and the positive and negative ground voltages are no longer balanced and exceed the preset setting value, the main controller LCD will display an alarm message, and the system grounding indicator and buzzer will alarm at the same time. The alarm information can also be uploaded to the upper computer of the integrated automation system or dispatching automation system through the YX switch and RS485 interface.

Grounding detection: The main controller receives the characteristic state information of each loop uploaded by the data collector in real time, and conducts intelligent analysis through pattern matching technology to distinguish different grounding states, and eliminates system charging pulse interference, fluctuation level interference and loops. Finally, the grounding loop can be accurately judged and the grounding impedance can be calculated. The grounding impedance value is displayed on the LCD screen, and can be uploaded to the host computer of the integrated automation system or dispatching automation system through the RS485 interface.

Loop diagnosis: Power DC loops are ubiquitous and cause great interference to the location of ground fault points. The main controller matches the characteristic state information of each loop with the built-in characteristic rules of the system for artificial intelligence mode matching, introduces the concept of loop index for the first time, and analyzes the fault loops, abnormal loops, and system dual power supplies that exist in the system. Alternate loop, loop with loop, and loop ground loop provide comprehensive loop status information and display on the LCD screen. It can effectively help operation and maintenance personnel to accurately understand the current state of the DC system and quickly troubleshoot.

Insulation early warning: Since the detection accuracy of the main controller is extremely high, which can reach more than 500K, it can judge the long-term change trend of the ground impedance of the ungrounded loop and provide early warning information of the loop ground. Insulation reduction warning and loop matching monitoring provide effective means for system diagnosis.

History record: The system grounding record will be automatically saved in EEPROM for reference. The record includes the date and time of grounding, grounding impedance, grounding loop and other information and can be saved after power failure. The historical record also includes the date and time of the AC series power, the voltage of the series power and other information, which can be saved after power failure.

The product of the present invention has the following structural features: the maximum number of grounding records is 1000. Input and output interface. Cruise-style man-machine interface, building-block menu, simple operation and powerful functions. Multi-group LED system status display, communication status display. Built-in two-tone buzzer alarm. Multiple sets of YX switch output. RS485 communication interface.

The anti-interference processing method of the present invention: since the DC ground leakage current is a very small signal, in order to obtain accurate test results, anti-interference processing must be carried out during the test process.

Interference source analysis: The interference source may come from the outside, or it may be generated by the test circuit itself;

External: external interference sources include DC system distributed capacitance, large current interference generated by dual power supply circuits, high frequency switching power supply module interference, external magnetic field interference, etc.;

Internal: Sensor zero drift, linearity.

Manifestations of interference: Interference may appear in different forms, with dynamic loads in an online environment or occasional radio frequency (RF) interference, which may generate random transient noise;

Periodic noise may be caused by conductive AC ripple from the charging circuit or radiated AC noise from the wires.

The present invention handles interference:

a. The hardware design of double-layer anti-distributed capacitance interference and the software design of anti-communication noise theory can eliminate the interference of DC system distributed capacitance, electromagnetic pulse interference and other noise interference;

b. The internal sampling circuit of the system analyzer adopts a high-precision isolation operational amplifier to reduce the interference of the DC system to the main controller;

c. Use a high-resolution DC sensor as the signal input source. On the one hand, the DC sensor itself has a strong anti-interference ability, and on the other hand, the high resolution is conducive to improving the signal-to-noise ratio;

d. Adopt a single 16-bit CPU to preprocess and pre-analyze the output data of the 10-channel 16-bit high-speed AD converter. The front end of the AD converter is buffered and protected by a signal conditioning circuit composed of a high-precision operational amplifier.

Main technical index of the present invention:

It can monitor the range of insulation resistance to ground: ground resistance: 0-50K; insulation reduction: 51-500K.

Monitorable voltage range:

Positive ground voltage: 0-300V;

Negative voltage to ground: 0-300V;

Total system voltage: 0-300V;

AC series voltage: 0-300V;

Ripple peak-to-peak voltage: 0-20V.

Anti-DC system distributed capacitance interference: greater than 10000uF.

Applicable DC system voltage level: 220V, 110V, 48V, 24V or other voltages proposed by the user, etc.

class.

The number of DC circuits that can be monitored: 500 circuits.

The ground impedance value of the host connected to the DC system: greater than 1000 K.

Voltage monitoring error is less than 0.2%.

Earth insulation alarm, with YX output contacts.

System voltage low limit alarm, with YX output contact.

System voltage high limit alarm, with YX output contact.

Standard RS232/RS485/RS422 interface, interface with integrated automation system and dispatching automation system.

Working environment temperature: -30℃—+50℃.

Relative humidity: ≤96%.

The above-mentioned embodiment is a preferred embodiment of the present invention, but the embodiment of the present invention is not limited by the above-mentioned embodiment, and any other changes, modifications, substitutions, combinations, Simplifications should be equivalent replacement methods, and all are included in the protection scope of the present invention.

Claims (1)

1. straight-flow system exchanges a malfunction monitoring selection method for crosstalk and insulation fault monitoring line selection apparatus, it is characterized in that:

Device comprises host computer, monitoring device, sampling system and current sensor, described monitoring device comprises master controller, master controller is provided with liquid crystal display, master controller is the key control unit of whole system, is provided with the main interface that DA output module, data memory module, LCD display module, input through keyboard module, monitor message display and configuration information input; Current sensor is arranged on each transmission line circuit place of each feeder line screen; Described sampling system comprises data acquisition unit, and data acquisition unit, between master controller and current sensor, selects installation site as required; Star connection or chain is adopted to connect two kinds of link models between master controller and data acquisition unit, each data acquisition unit and master controller are directly connected by RS485 bus, or be indirectly connected by the cascade port of another data acquisition unit and master controller, be convenient to install and wiring; Communication between master controller and data acquisition unit is determined by the unique address code of data acquisition unit, and the automatic identification data collector of master controller, need not manually be arranged; Each data acquisition unit mounts multiple current sensor, and when current sensor is by after special purpose interface access data collector, data acquisition unit can identify current sensor automatically, need not manually arrange;

Method comprises:

Extract AC compounent effective value, monitoring device inside adopts high-pass filtering circuit to be extracted by the alternating voltage over the ground in straight-flow system, then converts alternating voltage to DC voltage by RMS conversion chip, gives processor sampling system;

Extract the ripple peak-to-peak value in straight-flow system, monitoring device inside adopts high-pass filtering circuit to be extracted by the alternating voltage over the ground in straight-flow system, extract AC ripple peak-to-peak value through independently high speed sampling circuit, give processor analysis, the band of high speed sampling circuit is wider than 20MHz;

Adopt alternating current-direct current component to be separated digital filtering technique, specifically adopt high pass and low-pass filter circuit to be separated by alternating current-direct current component in monitoring device inside, DC voltage gives processor sampling system after biased;

Adopt DC leakage current detection technique, after specifically occurring to exchange crosstalk fault in straight-flow system, system shows as a large amount of power frequency ac voltages, crosstalk one pole over the ground DC voltage declines; Feeder line then creates DC leakage current by crosstalk loop, by can realize the route selection function exchanging crosstalk loop to the Real-Time Monitoring of this leakage current;

The route selection in crosstalk loop, after straight-flow system occurs to exchange crosstalk fault, exchange crosstalk loop and show obvious earth fault, exchange crosstalk fault monitoring system, on the tested feeder line of every bar, a High-accuracy direct current current sensor is housed, DC current sensor has good filtration to AC signal;

Adopt RS485 isolated communication technology and quick FFT converter technique, in the signal mode, monitoring device applies a low frequency small-signal source in the mode of constant current source to straight-flow system by DA conversion module and constant current signal output module, signal frequency 0.125 Hz, 0.25Hz, 0.5Hz, 1Hz is optional, waveform is sinusoidal wave, and monitoring device gathers voltage-to-ground, is extracted the signal voltage amplitude of signal frequency point by quick FFT conversion; Data acquisition unit extracts the marking current amplitude of signal frequency point after carrying out FFT conversion to the leakage current of each feeder line, upload to monitoring device by RS485 isolation, monitoring device utilizes voltage magnitude and current amplitude to calculate the insulation resistance of each monitoring circuit;

Master controller real-time monitoring system Bus Voltage, comprise system voltage, positive voltage-to-ground, negative voltage-to-ground, exchange crosstalk voltage and ripple peak-to-peak value voltage, and show in real time, when straight-flow system breaks down, system voltage is higher or on the low side when exceeding default setting valve, or when alternating voltage or ripple peak-to-peak value voltage exceed default setting valve, master controller liquid crystal display display alarm information, voltage out-of-limit pilot lamp and hummer alarm simultaneously, warning information also uploads to complex automatic system or dispatch automated system host computer by switching value and RS485 interface,

Master controller real-time monitoring system bus earth impedance, comprise positive resistance to earth, negative resistance to earth, and show in real time, when straight-flow system breaks down, when positive and negative voltage-to-ground no longer balances and exceedes default setting valve, master controller liquid crystal display display alarm information, system earth pilot lamp and hummer alarm simultaneously, warning information also uploads to complex automatic system or dispatch automated system host computer by switching value and RS485 interface;

Each loopback diagnostic status information that master controller real-time reception data acquisition unit is uploaded, and carry out intellectual analysis by mode-matching technique, distinguish different ground states, removal system charging pulse disturbs, the impact that the interference of fluctuating level and loop bring, finally accurately judges ground loop, and calculates impedance ground, impedance ground numerical value shows at liquid crystal display, and uploads to complex automatic system or dispatch automated system host computer by RS485 interface;

Master controller is by carrying out artificial intelligence pattern's coupling by the feature status information in every bar loop and the built-in characterization rules of system; the loop of the fault loop existed system, improper loop, system dual power supply loop for subsequent use each other, band loop and loop ground loop; perfect loop circuit state information is provided; and be shown on liquid crystal display; effective help operation maintenance personnel accurately understands the current state of straight-flow system, promptly fixes a breakdown.