CN102759682A - Judgment method of small current system one-phase ground circuit and one-phase ground indicator - Google Patents
Judgment method of small current system one-phase ground circuit and one-phase ground indicator Download PDFInfo
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- CN102759682A CN102759682A CN2012102730828A CN201210273082A CN102759682A CN 102759682 A CN102759682 A CN 102759682A CN 2012102730828 A CN2012102730828 A CN 2012102730828A CN 201210273082 A CN201210273082 A CN 201210273082A CN 102759682 A CN102759682 A CN 102759682A
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Abstract
The invention relates to a judgment method of a small current system one-phase ground circuit and a one-phase ground indicator. Three-phase current of each circuit of each circuit CT is respectively collected, and whether one-phase ground faults occur or not on corresponding circuit is judged. As for one circuit, steps comprise collecting data, conducting pretreatment, forecasting and judging and outputting. An AD collecting module for collecting CT three-phase current signals on one circuit is arranged on the one-phase ground indicator, the AD collecting module is connected with a central processing unit (CPU) which controls and is connected with a relay unit through a driving unit, and corresponding switch connectors in the relay unit are connected in a warning device return circuit. The judgment method can accurately judge whether a circuit below the CT has one-phase ground phenomena, only needs to collect three-phase CT signals, reduces investment and simplifies connection.
Description
Technical field
The present invention relates in a kind of small current system, differentiate a kind of single-phase earthing indicator of method with this method of use of the circuit that singlephase earth fault takes place.
Background technology
It is technological a kind of that present small current neutral grounding system is judged single-phase earthing is with the zero sequence current signal of all circuits at the same level put together comparison size and phase place, is suitable for being contained in the transformer station.Second kind is the indicator that is contained on each each phase line of bar outlet, gathers current signal separately, the current break signal before and after the more a certain moment.This method is only relatively big or small, and being hard to tell Chu's fault after-current variation is own capacitance current or fault current, and for the bigger circuit of imbalance, often wrong report.For city net that is mostly overhead transmission line and rural power grids power supply; The branch line of every circuit is with there being the shunting switch of automatic recloser function to cut-off, and zero sequence current signal and definite value that existing theory and technology is just gathered in the shunting switch have relatively judged whether single-phase earthing.It is bigger that this method is influenced by power system capacity, can not accurately judge it is which bar branch line.For the flame-proof switch of down-hole, first kind of technology is owing to need to concentrate all zero sequence signals of collection, and the signal wiring is too many, can not guarantee requirement of explosion proof.Be badly in need of on the market wanting wiring simple, be contained in the switch, can accurately differentiate still a kind of current protective device of outer circuit fault of this line fault.
Summary of the invention
The purpose of this invention is to provide in a kind of small current system, differentiate a kind of single-phase earthing indicator of method with this method of use of the circuit that singlephase earth fault takes place, in order to solve the problem that existing discriminant approach wiring is complicated, judging nicety rate is low.
Be to realize above-mentioned purpose, method scheme of the present invention is: the determination methods of small current system single-phase earthing circuit, gather the three-phase current of each bar circuit CT respectively, and judge whether corresponding line singlephase earth fault takes place; For a circuit, determining step is following:
1) image data: gather three-phase current, calculate the absolute value Y of three-phase current algebraic sum at every turn when gathering; Set the first setting value C1, the second setting value C2, the 3rd setting value C3, the 4th setting value C4, the 5th setting value C5, set COEFFICIENT K, setting-up time interval T;
If Y is greater than C1, be designated as the trigger point, continue step 1), and write down from then on 5ms 35ms after the trigger point before the trigger point, the sampled data of common 40ms; 20ms is the reference data before remembering among this 40ms, and back 20ms data are sample data; The data of 10ms are judgment data behind the trigger point;
2) pre-service: in the 10ms data, three-phase current absolute value maximal value is respectively F1, F2, F3, F1 < F2 < F3 before the note reference data;
In the 10ms data, three-phase current absolute value maximal value is respectively R1, R2, R3, R1 < R2 < R3 after the note reference data;
In the 10ms data, the maximal value of the absolute value Y of three-phase current algebraic sum is M after the note sample data;
If F1, F2, F3 all >=C3; Then the reference data are handled,, F1 is belonged to the current value addition that belongs to corresponding sampled point with F2 if (F2-F1)<(F3-F2); Take absolute value after the addition; Its maximal value is designated as E4, and note F3 is E5, E5 corresponding sampled point and E4 SI of corresponding sampled point be S45; If (a2-a1)>(a3-a2), F3 place and F2 are belonged to the current value addition of corresponding sampled point, take absolute value after the addition, its maximal value is designated as E4, note F1 is E5, E5 corresponding sampled point and E4 SI of corresponding sampled point be S45;
3) pre-alarm:
Judge A: if R1≤C2, R2>=C3, R3>=C3, output pre-alarm A;
Judge B: if like F1≤C2, F2≤C2, F3≤C2, and M equate with D1 (the permission error in judgement+/-K) and apart from the output time≤5S that reported to the police last time, export pre-alarm B;
Judge C: if E5-E4>=C4, S45≤T, E4 and E5 opposite in sign, output pre-alarm C;
4) judge output:
When at least one pre-alarm exists, open again and gather 20ms, if in the three-phase, every phase data absolute value maximal value≤C2 judges that circuit does not have singlephase earth fault, otherwise, judge line single phase grounding failure.
Device scheme of the present invention is: the single-phase earthing indicator; This single-phase earthing indicator is provided with the AD acquisition module that is used to gather CT three-phase current signal on the circuit; The AD acquisition module connects CPU; CPU is through driver element control linkage relay unit, and the respective switch contact in the relay unit is connected in the warning device loop.
CPU also is connected with communication interface module.
Said single-phase earthing indicator also comprises power module, and power module comprises voltage regulation unit, and voltage regulation unit is connected with a rectification unit that is used to connect civil power, and voltage regulation unit also is provided with the direct-flow input end mouth that is used to connect the direct current input.
Said power module also comprises the detection of power loss unit that is used for the pick-up unit power down, the corresponding relay control linkage in detection of power loss unit and the said relay unit.
Said warning device is an acoustic-optic alarm.
Determination methods of the present invention can judge accurately whether the circuit of CT below has the single-phase earthing phenomenon, and in order to reduce investment and to simplify wiring, only needs to gather three-phase CT signal, does not need to install additional in addition zero sequence CT and residual voltage signal.Because the zero-sequence current phase place of the zero-sequence current of faulty line and all non-fault lines is opposite, the single-phase earthing indicator with three-phase CT signals collecting after, utilize wavelet algorithm to judge whether to break down, and current signal carried out wavelet analysis.Distinguish signal at the corresponding levels and external signal, export after the logic, promptly judge and export the result.
The present invention only needs three-phase current signal; Adopted double small ripple fault-signal algorithm; Can in 50ms behind the generation singlephase earth fault, judge automatically whether isolating switch or automatic circuit below circuit single-phase earthing and broken string occur, more than the rate of accuracy reached to 97%;, less than 50% accuracy rate the safe operation of the power supply-distribution system of city net and rural power grids is of great importance far above other zero-sequenceprotections.After this protection is installed in the flame-proof switch of down-hole, can select the singlephase earth fault circuit accurately, particularly important for the safe power supply of down-hole.
Description of drawings
Fig. 1 is to use the small current system synoptic diagram of single-phase earthing indicator of the present invention;
Fig. 2 is the earth detector structured flowchart;
Fig. 3 is earth detector input wires figure;
Fig. 4 is earth detector warning output and power supply wiring figure.
Embodiment
Below in conjunction with accompanying drawing the present invention is done further detailed explanation.
Single-phase earthing indicator embodiment
As shown in Figure 1, in the small current system, the circuit at the same level of all under the bus, each circuit CT secondary singal all inserts a single-phase earthing indicator, like figure, single-phase earthing indicator 1-single-phase earthing indicator n.The single-phase earthing indicator is gathered the CT three-phase current signal through the respective input mouth, and the single-phase earthing indicator is judged according to the collection situation, through corresponding output end mouth output judged result.
As shown in Figure 2; The single-phase earthing indicator is provided with the AD acquisition module that is used to gather CT three-phase current signal on the circuit; The AD acquisition module connects CPU, and CPU is through driver element control linkage relay unit, and the respective switch contact in the relay unit is connected in the warning device loop.CPU also is connected with communication interface module.The single-phase earthing indicator also comprises power module, and power module comprises voltage regulation unit, and voltage regulation unit is connected with a rectification unit that is used to connect civil power, and voltage regulation unit also is provided with the direct-flow input end mouth that is used to connect the direct current input.Warning device is an acoustic-optic alarm.The communication module support pattern comprises RS232, RS485 (apolegamy) CDT and MODBUS stipulations (apolegamy).
Fig. 3 is a single-phase earthing indicator input wires, and except essential three-phase CT secondary singal wiring, the interface that also is provided with connection residual voltage signal is with subsequent use.Fig. 4 is output and the power supply wiring of reporting to the police.Indicator itself uses DC12V, DC24V, AC220V optional.When indicator was charged, which kind of current protection action no matter power supply green light greening zero diopter had, and the fault red light is all by secretly become bright showing at present.During singlephase earth fault, relay unit control ground connection closure makes K1 and K6 conducting, and can pass to trip(ping) circuit and signal circuit.When indicator dead electricity, indicator deadlock, program mal, control ground connection makes K5 and K6 conducting.
K1 is respectively single-phase earthing, overcurrent, quick-break, specified time, plant failure, COM to K6; J1, J2 are producer's debugging.
Determination methods embodiment
When the single-phase earthing telltale reset, can carry out the parameter setting, set the first setting value C1, the second setting value C2, the 3rd setting value C3, the 4th setting value C4, the 5th setting value C5, set COEFFICIENT K, setting-up time interval T;
The single-phase earthing indicator was gathered according to the cycle of setting, and set the cycle of each 50Hz and gathered 200 points, and theoretical sample rate is 10KSPS.Single-phase earthing indicator MCU reads data converted from ADC, is saved among the RAM successively according to 3 phases and time order and function.RAM is a toroidal memory, preserves the sampled data of certain-length before the current time forever, only otherwise be in analysis state, gather carry out always and cycle and regeneration of mature RAM in data.This 3 number of phases border factually forms the matrix with Xiang Weihang, is called the transient data matrix, as follows:
Determining step is following:
1) data acquisition: calculate the absolute value Y of three-phase current algebraic sum when at every turn gathering, Y=|ai+bi+ci|, i=1,2 ... N, i are the sampled point sequence number; If Y greater than C1, is designated as the trigger point.After triggering, MCU carries out the collection of certain-length again, then, finishes to gather the entering data analysis process.At this moment, will forbid that image data continues to write among the RAM, whether also no longer carrying out transfinites to trigger is judged, is to judge the dead band during this period of time.
The time of gathering again is 35ms, writes down from then on 5ms 35ms after the trigger point before the trigger point, the sampled data of common 40ms; 20ms is the reference data before remembering among this 40ms, and back 20ms data are sample data; The data of 10ms are judgment data behind the trigger point;
2) pre-service: in the 10ms data, three-phase current absolute value maximal value is respectively F1, F2, F3, F1 < F2 < F3 before the note reference data;
In the 10ms data, three-phase current absolute value maximal value is respectively R1, R2, R3, R1 < R2 < R3 after the note reference data;
In the 10ms data, the maximal value of the absolute value Y of three-phase current algebraic sum is M after the note sample data;
If in the preceding 10ms data of reference data, the absolute value maximal value of every phase data, promptly F1, F2, F3 all >=C3, then the reference data form run time fault data---the ffault matrix of one 3 row, the behavior phase is classified sampling number as.Ffault matrix is identical with aforementioned transient data matrix representation method, like (1).
If F1, F2, F3 all >=C3, then the reference data are handled, if (F2-F1)<(F3-F2), the 4th capable with the capable pointwise addition formation run time fault matrix (2) at F1 and F2 place, h1=ai+bi, i=1,2 ... N.F3 place line data is as the 5th row of ffault matrix (2), gi=ci, i=1,2 ... N; If (F2F1)>(F3F2), the capable pointwise addition at F3 and F2 place is formed the 4th capable of run time fault matrix (2), h1=ci+bi, i=1,2 ... N.F1 place line data is as the 5th row of ffault matrix (2), gi=ai, i=1,2 ... N.
(2) fourth line absolute value maximal value is designated as E4, and fifth line absolute value maximal value is E5, E5 corresponding sampled point and E4 SI of corresponding sampled point be S45.
3) pre-alarm:
Judge A: if R1≤C2, R2>=C3, R3>=C3, output pre-alarm A;
Judge B: if like F1≤C2, F2≤C2, F3≤C2, and M equate with D1 (the permission error in judgement+/-K) and apart from the output time≤T1 that reported to the police last time, export pre-alarm B; T1 gets 5s.
Judge C: if | E5-E4|>=C4, S45≤T2, E4 and E5 opposite in sign, output pre-alarm C; In the present embodiment, S45 is with the sampling sequence number time interval SI, and T2 gets 5, equals 0.5mS during for the SI with 100uS.
4) judge output:
When at least one pre-alarm exists, open again and gather 20ms, if in the three-phase, every phase data absolute value maximal value≤C2 judges that circuit does not have singlephase earth fault, otherwise, judge line single phase grounding failure.
Being judged as fault then reports to the police.During normal output alarm, drive alarm relay and alarm lamp.It was 1 second that the shortest time of reporting to the police requires, above 1 second confirmed by following warning termination condition.
(1) output of warning has been arranged;
(2) report to the police output shortest time timer to then continuing, report to the police less than then continuing.
(3) restart to gather after, finish to report to the police during the absolute value maximal value of three-phase real time data algebraic sum≤C1, otherwise the output of reporting to the police is constant.
When (four) finish reporting to the police, if the warning that pre-alarm C causes output, then end of record (EOR) is reported to the police constantly, and end of record (EOR) constantly before last three-phase algebraic sum absolute value maximal value (in the 10mS), and this maximal value absolute value assignment to D1.
C1, C2, C3, C4 and K parameter allow user or engineering technical personnel, are provided with as the case may be.Parameter is set for these and D1 supports the power down hold function.
As a kind of embodiment, C1 is decided to be 25mA, and C2 is decided to be 5mA, and C3 is decided to be 500mA, and C4 is decided to be 25mA, and K is decided to be 3, and D1 is defaulted as 0.The current unit that C1~C4 is involved: milliampere (mA) all calculates with secondary side full scale 5000mA.Because the precision and the linearity of sensor can only guarantee 0.1%, therefore, best relative accuracy is exactly secondary side 5mA, possibly be difficult to guarantee accurately less than the electric current of this numerical value.
Claims (6)
1. the determination methods of small current system single-phase earthing circuit is characterized in that, gathers the three-phase current of each bar circuit CT respectively, judges whether corresponding line singlephase earth fault takes place; For a circuit, determining step is following:
1) image data:Gather three-phase current, calculate the absolute value Y of three-phase current algebraic sum at every turn when gathering; Set the first setting value C1, the second setting value C2, the 3rd setting value C3, the 4th setting value C4, the 5th setting value C5, set COEFFICIENT K, setting-up time interval T;
If Y is greater than C1, be designated as the trigger point, continue step 1), and write down from then on 5ms 35ms after the trigger point before the trigger point, the sampled data of common 40ms; 20ms is the reference data before remembering among this 40ms, and back 20ms data are sample data; The data of 10ms are judgment data behind the trigger point;
2) pre-service:In the 10ms data, three-phase current absolute value maximal value is respectively F1, F2, F3, F1 before the note reference data<f2<f3;
In the 10ms data, three-phase current absolute value maximal value is respectively R1, R2, R3, R1 < R2 < R3 after the note reference data;
In the 10ms data, the maximal value of the absolute value Y of three-phase current algebraic sum is M after the note sample data;
If F1, F2, F3 all >=C3; Then the reference data are handled, if F2-F1<F3-F2 belongs to F1 the current value addition that belongs to corresponding sampled point with F2; Take absolute value after the addition; Its maximal value is designated as E4, and note F3 is E5, E5 corresponding sampled point and E4 SI of corresponding sampled point be S45; If a2-a1>a3-a2 belongs to the current value addition of corresponding sampled point with F3 place and F2, take absolute value after the addition, its maximal value is designated as E4, note F1 is E5, E5 corresponding sampled point and E4 SI of corresponding sampled point be S45;
3) pre-alarm:
Judge A: if R1≤C2, R2>=C3, R3>=C3, output pre-alarm A;
Judge B: if like F1≤C2, F2≤C2, F3≤C2, and M equates with D1 and apart from the output time≤5S that reported to the police last time, export pre-alarm B;
Judge C: if | E5-E4|>=C4, S45≤T, E4 and E5 opposite in sign, output pre-alarm C;
4) judge output:
When at least one pre-alarm exists, open again and gather 20ms, if in the three-phase, every phase data absolute value maximal value≤C2 judges that circuit does not have singlephase earth fault, otherwise, judge line single phase grounding failure.
2. adopt the single-phase earthing indicator of method according to claim 1; It is characterized in that; This single-phase earthing indicator is provided with the AD acquisition module that is used to gather CT three-phase current signal on the circuit; The AD acquisition module connects CPU, and CPU is through driver element control linkage relay unit, and the respective switch contact in the relay unit is connected in the warning device loop.
3. single-phase earthing indicator according to claim 2 is characterized in that CPU also is connected with communication interface module.
4. single-phase earthing indicator according to claim 2; It is characterized in that; Said single-phase earthing indicator also comprises power module; Power module comprises voltage regulation unit, and voltage regulation unit is connected with a rectification unit that is used to connect civil power, and voltage regulation unit also is provided with the direct-flow input end mouth that is used to connect the direct current input.
5. single-phase earthing indicator according to claim 4 is characterized in that, said power module also comprises the detection of power loss unit that is used for the pick-up unit power down, the corresponding relay control linkage in detection of power loss unit and the said relay unit.
6. single-phase earthing indicator according to claim 2 is characterized in that, said warning device is an acoustic-optic alarm.
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CN110707670A (en) * | 2019-10-24 | 2020-01-17 | 南方电网科学研究院有限责任公司 | Transformer substation small-resistance grounding device and control method thereof |
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