CN202522654U

CN202522654U - Low-current grounding fault line selection device

Info

Publication number: CN202522654U
Application number: CN2012200502678U
Authority: CN
Inventors: 李刚; 郑顾平; 齐郑; 杨以涵; 田永超
Original assignee: North China Electric Power University
Current assignee: North China Electric Power University
Priority date: 2012-02-16
Filing date: 2012-02-16
Publication date: 2012-11-07
Anticipated expiration: 2022-02-16

Abstract

The utility model discloses a low-current grounding fault line selection device which is composed of a secondary transformer, an amplitude limiting circuit, a zero-sequence adjusting circuit, an STM32 development board, a GPS module, a GPRS module and a liquid crystal display, wherein an input end of the secondary transformer is connected with zero-sequence current of a certain line or a bus zero-sequence voltage signal, and an output end of the secondary transformer is connected with a PB0 port of the STM32 development board by the amplitude limiting circuit and the zero-sequence adjusting circuit in sequence; the STM32 development board is connected with the GPS module and the GPRS module by a serial port, D0-D15 ends of the STM32 development board are connected with the liquid crystal display, a PB11 port of the STM32 development board is connected with a 1PPS port of the GPS module. A low-current grounding fault line can be determined rapidly and accurately without cutting the power off by adopting the device disclosed by the utility model, thereby facilitating maintenance personnel to remove the fault in time. The device is suitable for various fault conditions of metallic grounding, grounding through voltaic arcs, grounding through transition resistors and the like.

Description

Low-current ground fault line selection device

Technical field

The utility model relates to a kind of device that is used for detecting from many circuits that are connected the same bus of system with non-effectively earthed neutral the generation earth fault line, belongs to technical field of measurement and test.

Background technology

The 3kV-60kV power distribution network extensively adopts system with non-effectively earthed neutral, is called small current neutral grounding system again, and most faults of such electrical network are singlephase earth faults.During non-useful earthing electric network generation singlephase earth fault, other two phase-to-ground voltage raises to line voltage, and system insulation is on the hazard; In when, particularly intermittent arc grounding taking place; Because neutral point does not have the electric charge releasing pathway, can cause the arc grounding superpotential, and then cause phase fault.Therefore, must find out faulty line as early as possible and get rid of fault.

Because the medium voltage network wiring is complicated, branch is numerous, and artificial line walking efficient is low, and can prolong power off time, influences power supply safety, therefore needs to use line selection apparatus that fault section is positioned.The Fault Locating Method that existing line selection apparatus is adopted has two kinds, and a kind of is the signal injection method, comprises " S " injection method and power frequency amount injection method; The unfavorable failure message that provides with fault self of these class methods carries out the passive type route selection, but injects a line selection signal on one's own initiative, and the shortcoming of its existence mainly contains three; At first; Because it is big inadequately to inject the power of signal, it is very faint to transform on high-tension side injection signal, is difficult to accurately measure; Secondly, injecting signal can produce charging current at non-fault line, take the capacity that injects power supply, and when fault resstance was big, the signal difference on faulty line and the non-fault line was not obvious; The 3rd, need the additional signal device, operation is complicated, and reliability is lower.Second method is that the fault current through measuring circuit positions, but this method measures is phase current, because single-phase-to-ground current much smaller than load current, therefore can't accurately extract failure message, causes locating inaccurate.In a word, existing line selection apparatus can not detect the circuit that low current grounding takes place quickly and accurately from many circuits that are connected same bus, also need study the more superior line selection apparatus of performance.

The utility model content

The purpose of the utility model be to overcome prior art deficiency, provide a kind of and can from many circuits that are connected same bus, detect the line selection apparatus that the low current grounding circuit takes place quickly and accurately.

The said problem of the utility model realizes with following technical proposals:

A kind of low-current ground fault line selection device; Form by secondary mutual inductor, amplitude limiter circuit, zero sequence adjustment circuit, STM32 development board, GPS module, GPRS module and LCD; The input termination circuit zero-sequence current of said secondary mutual inductor or bus residual voltage signal, output terminal are adjusted the PB0 port that circuit connects the STM32 development board through amplitude limiter circuit and zero sequence successively; Said STM32 development board links to each other with the GPS module with the GPRS module through serial ports, its D0～D15 termination LCD, and the PB11 port of STM32 development board connects the 1PPS port of GPS module.

Above-mentioned low-current ground fault line selection device; Said amplitude limiter circuit is made up of diode, resistance and electric capacity; Four diodes are connected into the bridge-type amplitude limiter circuit; Positive voltage warp first resistance of power supply output and second electric resistance partial pressure are after the 3rd resistance provides upper voltage limit for the bridge-type amplitude limiter circuit; The negative voltage of power supply output through the 4th resistance with the 5th electric resistance partial pressure after the 6th resistance provides lower voltage limit for the bridge-type amplitude limiter circuit, the signal output part of the input termination secondary mutual inductor of bridge-type amplitude limiter circuit, output signal through the 7th resistance and the 8th electric resistance partial pressure and by capacitor filtering after the connecting to neutral preface adjust the input end of circuit.

Above-mentioned low-current ground fault line selection device; Said zero sequence adjustment circuit is made up of operational amplifier, adjustable resistance and potentiometer; The in-phase input end of operational amplifier connects limit circuit output end, reverse inter-input-ing ending grounding, the PB0 port of output termination STM32 development board; The two ends of said adjustable resistance connect two RG ends of operational amplifier respectively; Two termination DC voltages of said potentiometer, the REF end of slip termination operational amplifier.

The utility model can be measured the zero-sequence current on bus residual voltage and each circuit easily, just can accurately judge the circuit that low current grounding takes place through the amplitude and the phase place of zero-sequence current on isolated-phase buses residual voltage and each circuit.This device has made full use of the effective information of system under failure condition; Not only greatly improve the accuracy of low current grounding location, and do not received the influence of earth fault type, also do not needed the additional signal device; Simple to operate, have very high reliability.

The utility model can be confirmed to help the low current grounding circuit maintenance personal and in time fix a breakdown under situation about not having a power failure quickly and accurately.This device is applicable to metallic earthing, through arcing ground, through various faults situation such as transition resistance eutral groundings.

Description of drawings

Below in conjunction with accompanying drawing the utility model is done further to detail.

Fig. 1 is the electrical schematic diagram of the utility model;

Fig. 2 is the current direction in the circuit when having singlephase earth fault;

Fig. 3 is the route selection principle schematic.

Each label is among the figure: T, secondary mutual inductor; U1, operational amplifier; U2, STM32 development board; LCD, LCD; R1～R9, resistance; D1～D4, diode; W, potentiometer; C, electric capacity.

Embodiment

Referring to Fig. 1; Residual voltage, zero sequence current signal change into after through secondary mutual inductor T-and 5V is to the low pressure analog signals the between+5V; Pass through the bridge-type amplitude limiter circuit of forming by diode D1～D4 and resistance R 1～R6 (amplitude limiter circuit can prevent the impact of surge voltage to system) then; Get into zero sequence adjustment circuit through the simulating signal behind the amplitude limit, this circuit is made up of high precision operating amplifier U1 (AD620), resistance R 9, potentiometer W and capacitor C.AD620 only needs a non-essential resistance that gain is set, and gain margin is 1 to 10,000; Resistance R 7 and the simulating signal dividing potential drop of R8 to the output of bridge-type amplitude limiter circuit; Capacitor C is to simulating signal filtering, and the gain size of adjustable resistance R9 control AD620 is adjusted to a suitable amplitude range with signal.The bias voltage of potentiometer W control AD620 can all be adjusted to the output simulating signal more than the 0V.The adjusted simulating signal of process is connected to the PB0 port of STM32F103ZE development board, and the PB0 port is connected to the ADC controller in the STM32F103ZE development board, and links to each other with processor A RM Cortex-M3.The STM32F103ZE development board links to each other with the GPS module with the GPRS module through serial ports, and the pps pulse per second signal of GPS module is connected directly to ARM Cortex-M3 processor through the PB11 port in addition.When GPS receives satellite-signal pulse per second (PPS) will be provided, at this moment NVIC interruptable controller respective interrupt makes ARM Cortex-M3 processor outage program.The interrupt routine control timer to the ADC controller regularly makes the ADC controller wait the digital signal after time difference collection simulating signal also will be changed to be sent to ARM Cortex-M3 processor continuously.ARM Cortex-M3 processor draws the zero sequence information constantly of gathering with all data process FFT computings after receiving information.And ARM Cortex-M3 processor reads the gps satellite time by serial ports 1, then zero sequence information is added the satellite time that reads, and sends the data to GPRS module and Internet by serial ports 2 again.Last ARM Cortex-M3 processor demonstrates zero sequence information and gps satellite time through the LCD liquid crystal display, and withdraws from interrupt routine.

The data channel that line selection apparatus measures the line zero sequence voltage is realized by open delta wiring circuit and two-stage PT.For isolated neutral system, the zero-sequence network impedance that the singlephase earth fault circuit takes place only is made up of the ground capacitance composition of circuit, and residual voltage produces zero sequence capacity current (referring to Fig. 2) on the line.

The existing direction that bus is pointed to loaded termination is defined as the positive dirction of this each branch of network.As shown in Figure 2, when singlephase earth fault appears in circuit 1,90 ° in circuit 1 zero-sequence current phase lag bus residual voltage phase place.And for circuit 2 and circuit 3, owing to there are not singlephase earth fault, 90 ° in the leading bus residual voltage of zero-sequence current phase place phase place.

Referring to Fig. 3; When from many circuits that are connected same bus, detecting the circuit that low current grounding takes place; Need a plurality of line selection apparatus of use to measure the zero-sequence current on bus residual voltage and each circuit simultaneously, the line selection apparatus of measuring the bus residual voltage is installed in transformer station, therefore can directly utilize the interior 220v voltage source in station to installing power supply; Inner 220V/ ± 12V the power transfer module that adopts of device is as the power supply of device.The backstage monitor server that each line selection apparatus sends measurement data, server just can accurately be judged the circuit that low current grounding takes place through the amplitude and the phase place of zero-sequence current on isolated-phase buses residual voltage and each circuit.

Claims

1. low-current ground fault line selection device; It is characterized in that; It is made up of secondary mutual inductor (T), amplitude limiter circuit, zero sequence adjustment circuit, STM32 development board (U2), GPS module, GPRS module and LCD (LCD); The input termination circuit zero-sequence current of said secondary mutual inductor (T) or bus residual voltage signal, output terminal are adjusted the PB0 port that circuit connects STM32 development board (U2) through amplitude limiter circuit and zero sequence successively; Said STM32 development board (U2) links to each other with the GPS module with the GPRS module through serial ports, its D0～D15 termination LCD (LCD), and the PB11 port of STM32 development board (U2) connects the 1PPS port of GPS module.

2. low-current ground fault line selection device according to claim 1; It is characterized in that; Said amplitude limiter circuit is made up of diode, resistance and electric capacity (C); Four diodes are connected into the bridge-type amplitude limiter circuit; Positive voltage warp first resistance (R1) of power supply output and second resistance (R2) dividing potential drop are after the 3rd resistance (R3) provides upper voltage limit for the bridge-type amplitude limiter circuit; The negative voltage of power supply output through the 4th resistance (R4) with the 5th resistance (R5) dividing potential drop after the 6th resistance (R6) provides lower voltage limit for the bridge-type amplitude limiter circuit, the signal output part of the input termination secondary mutual inductor (T) of bridge-type amplitude limiter circuit, output signal through the 7th resistance (R7) and the 8th resistance (R8) dividing potential drop and by electric capacity (C) filtering after the connecting to neutral preface adjust the input end of circuit.

3. low-current ground fault line selection device according to claim 1 and 2; It is characterized in that; Said zero sequence adjustment circuit is made up of operational amplifier (U1), adjustable resistance (R9) and potentiometer (W); The in-phase input end of operational amplifier (U1) connects limit circuit output end, reverse inter-input-ing ending grounding, the PB0 port of output termination STM32 development board (U2); The two ends of said adjustable resistance (R9) connect two RG ends of operational amplifier (U1) respectively; Two termination DC voltages of said potentiometer (W), the REF end of slip termination operational amplifier (U1).