CN107957528A - A kind of photovoltaic system earth-fault detecting method - Google Patents
A kind of photovoltaic system earth-fault detecting method Download PDFInfo
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- CN107957528A CN107957528A CN201810056839.5A CN201810056839A CN107957528A CN 107957528 A CN107957528 A CN 107957528A CN 201810056839 A CN201810056839 A CN 201810056839A CN 107957528 A CN107957528 A CN 107957528A
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- 238000000034 method Methods 0.000 title claims abstract description 19
- 238000001514 detection method Methods 0.000 claims abstract description 15
- 238000005259 measurement Methods 0.000 abstract description 3
- 230000032683 aging Effects 0.000 description 2
- 239000004020 conductor Substances 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 230000005611 electricity Effects 0.000 description 2
- 238000002310 reflectometry Methods 0.000 description 2
- 238000001228 spectrum Methods 0.000 description 2
- 230000004888 barrier function Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000003749 cleanliness Effects 0.000 description 1
- 238000010891 electric arc Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 1
- 239000010931 gold Substances 0.000 description 1
- 229910052737 gold Inorganic materials 0.000 description 1
- 238000007689 inspection Methods 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- 238000004321 preservation Methods 0.000 description 1
- 230000035882 stress Effects 0.000 description 1
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Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02S—GENERATION OF ELECTRIC POWER BY CONVERSION OF INFRARED RADIATION, VISIBLE LIGHT OR ULTRAVIOLET LIGHT, e.g. USING PHOTOVOLTAIC [PV] MODULES
- H02S50/00—Monitoring or testing of PV systems, e.g. load balancing or fault identification
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/50—Photovoltaic [PV] energy
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- General Physics & Mathematics (AREA)
- Testing Of Short-Circuits, Discontinuities, Leakage, Or Incorrect Line Connections (AREA)
- Photovoltaic Devices (AREA)
Abstract
The present invention provides a kind of photovoltaic system earth-fault detecting method, comprise the following steps：SSTDR detection devices are connected with after photovoltaic system, creating a reference value C under no ground failureb；Obtain the photovoltaic system error reference value N under no ground failureref;Photovoltaic system is continually scanned for, calculates photovoltaic system deviation value S；Judged whether that earth fault occurs according to photovoltaic system deviation value S and predetermined threshold value numerical values recited, alarm is sent if there are failure.The parameter such as voltage, electric current, irradiation level, temperature in additional sensors measurement photovoltaic system is not required in the present invention.According to the change of impedance value during photovoltaic system earth fault, by carrying out numerical analysis processing to the cross correlation value of incoming signal and reflected signal, photovoltaic system Earth Fault Detection is realized.
Description
Technical field：
The invention belongs to photovoltaic system field of fault detection, more particularly to photovoltaic system earth-fault detecting method.
Background technology：
The problem of photovoltaic generation is developed rapidly because of its cleanliness without any pollution, and some are serious also highlights, wherein
The electrical system safety problem that photovoltaic system aging is brought is especially prominent.Earth fault is considered most common in photovoltaic system
One of failure.There is complicated structure and substantial amounts of connection equipment in photovoltaic system, due to aging, thermal stress, mechanical stress, animal
The reason such as bait, cause the insulation damages such as photovoltaic module, terminal box, cable, apparatus interconnection line, cause current－carrying conductor and megarelief
Earth fault is formed during into a path passed through for electric current.Earth fault may produce electric arc, can draw when serious
Ignition calamity burns photovoltaic array.In addition, when earth fault occurs, there are failure electricity over the ground for the exposed current-carrying part of photovoltaic system
Pressure, to human body, there are great security risk.For such safety problem, National Electrical specification NEC (National
Electrical Code) No. 690.5 file regulation, photovoltaic system of any system voltage higher than 50V be required for ground connection therefore
Barrier protection.
According to photovoltaic DC busbar whether with being greatly connected, earthing type photovoltaic system and earth-free type photovoltaic system can be divided into
System.Earthing type photovoltaic system is illustrated in figure 2, dotted line represents not charged metallic conductor (such as photovoltaic module gold in photovoltaic system
Belong to frame, grounding rack, device housings etc.) reliably it is connected with the earth, inverter side dc bus is connected by fuse with the earth,
A in figure, B point are possible earth fault；Earth-free type photovoltaic system is in compared to what earthing type photovoltaic system was distinguished
It is not connected in dc bus with the earth.
At present, some Preservation tactics have been proposed for photovoltaic system earth fault in domestic and foreign scholars.It is grounded photovoltaic system
Come in system usually through Earth Fault Detection breaker (ground-fault detection and interruption, GFDI)
Photovoltaic system is monitored to earth-current, disconnecting circuit is to protect system after electric current exceedes predetermined threshold value.Such GFDI devices are basic
On be to carry out fault detect, such as fuse according to the amplitude of fault current.But when the earth fault electricity in photovoltaic system
Stream less than GFDI devices threshold value when, path will not be disconnected, will there is a situation where earth fault missing inspection.In addition, A in Fig. 1
The negative dc bus of point occurs also to can't detect during earth fault, this is a check frequency of GFDI.There is scholar's proposition in recent years
Photovoltaic Earth Fault Detection is carried out with the method that intelligent algorithm is combined based on parameter measurement, but usually these methods all need
Want extra sensor collection data and largely to be calculated.
The content of the invention
The present invention provides a kind of photovoltaic system earth-fault detecting method, it is therefore intended that solution occurs in photovoltaic system
The problem of earth fault is accurately detected during earth fault.
The technical solution adopted by the present invention, it is characterised in that：Comprise the following steps：
Step A：Create photovoltaic system SSTDR detection device a reference values；
Step B：Obtain photovoltaic system earth fault error reference value；
Step C：Photovoltaic system is scanned, calculates photovoltaic system earth fault deviation value；
Step D：Judged whether that earth fault occurs according to photovoltaic system earth fault deviation value and predetermined threshold value.
Preferably, the SSTDR detection devices in above-mentioned steps are connected with photovoltaic system dc bus and the earth respectively.
Preferably, the photovoltaic system SSTDR detection devices a reference value in above-mentioned steps A is incoming signal and reflected signal
Computing cross-correlation result average value, is expressed as：In formula, CiIt is ith measured value, N=10 is measurement time
Number, CbFor average value.
Preferably, the photovoltaic system error reference value in above-mentioned steps B is expressed as：In formula, T
For the cycle of incoming signal, CRFor the computing cross-correlation end value of incoming signal and reflected signal,CjIt is
Jth time measured value, M=10 are pendulous frequency, NrefFor CbWith CRThe area that the absolute value of difference is surrounded with time transverse axis.
Preferably, above-mentioned steps A, a reference value in step B, reference value are to pass through survey in the no ground failure of photovoltaic system
Examination obtains.
Preferably, the deviation value in above-mentioned steps C is expressed as,In formula, T is the week of incoming signal
Phase, CfFor computing cross-correlation result average value under current state,CkIt is kth time measured value, X=10 is
Pendulous frequency, deviation value S are CbWith CfThe area that the absolute value of difference is surrounded with time transverse axis.
Preferably, compared with the deviation value threshold value default with photovoltaic system in above-mentioned steps D, it is more than threshold value
Generation earth fault simultaneously sends alarm, and wherein threshold value takes 2 times of Nref。
Beneficial effects of the present invention are：
The parameter such as voltage, electric current, irradiation level, temperature in additional sensors measurement photovoltaic system is not required in the present invention.According to
The change of impedance value during photovoltaic system earth fault, by carrying out numerical analysis to the cross correlation value of incoming signal and reflected signal
Processing, realizes photovoltaic system Earth Fault Detection.
Brief description of the drawings
Fig. 1 is flow chart of the method for the present invention；
Fig. 2 is earthing type photovoltaic system；
The method that Fig. 3 is the present invention realizes block diagram；
Fig. 4 is the court verdict figure of the present invention.
Embodiment
In order to more specifically describe the present invention, hereby with preferred embodiment, and attached drawing is coordinated to be described in detail below：
Photovoltaic system earth-fault detecting method in the present invention is based on spread-spectrum time domain reflectometry (Spread
Spectrum Time Domain Reflectometry, SSTDR).Using the expansion with excellent correlation properties and broad spectrum
Incoming signal of the frequency signal as detection, photovoltaic system is connected to by coaxial cable.When cable termination impedance and cable feature
Incoming signal can reflect during impedance mismatch, and the amplitude and phase of reflected signal change with the change of terminal impedance.
Photovoltaic system earth impedance is considered as cable termination impedance in the present invention, according to impedance variations during photovoltaic system generation earth fault
Can make reflected signal change of properties, incoming signal and reflected signal are subjected to related operation, by correlation result value into
The processing of line number value is analyzed to detect failure.
As shown in Figure 1, an embodiment of the present invention provides a kind of photovoltaic system earth-fault detecting method, including following step
Suddenly：
Step A：Create photovoltaic system SSTDR detection device a reference values.
Be illustrated in figure 3 photovoltaic system earth-fault detecting method and realize block diagram, by SSTDR detection devices respectively with photovoltaic
System dc busbar is connected with the earth.
The a reference value C of SSTDR detection devices is established for the photovoltaic system of no ground failureb, i.e., incoming signal and reflection believe
Number computing cross-correlation result average value, be expressed as：
In formula, CiIt is ith measured value, N=10 is pendulous frequency, to reduce error, CbFor average value.
Step B：Obtain photovoltaic system earth fault error reference value.
Data difference during earth fault occurs to compare, obtains the photovoltaic system error reference value N of no ground failureref,
It is expressed as：
In formula, T be incoming signal cycle, CRFor the computing cross-correlation end value of incoming signal and reflected signal,CjIt is jth time measured value, M=10 is pendulous frequency.NrefFor CbWith CRThe absolute value of difference is horizontal with the time
The area that axis is surrounded.
Step C：Photovoltaic system is scanned, calculates photovoltaic system earth fault deviation value.
After a reference value and error reference value is established, constantly photovoltaic system is scanned and constantly injects incident letter
Number and calculate deviation value S, be expressed as：
In formula, T be incoming signal cycle, CfFor computing cross-correlation result average value under current state,CkIt is kth time measured value, X=10 is pendulous frequency, and deviation value S is CbWith CfThe absolute value of difference with
The area that time transverse axis is surrounded.
Step D：Judged whether that earth fault occurs according to photovoltaic system deviation value and predetermined threshold value.
A failure decision threshold is preset for photovoltaic system, takes 2 times of Nref, it is illustrated in figure 4 each position in Fig. 3 and occurs
Court verdict figure during earth fault, dotted line are threshold value.When deviation value is more than preset value, that is, it is judged to that earth fault occurs simultaneously
Send alarm.
Although the embodiment of the present invention is described in detail in the above process, but not to the limit of the scope of the present invention
System, the field technology personnel should be understood that on the basis of technical scheme those skilled in the art need not pay
Go out various modifications or deformation that creative work can make still within protection scope of the present invention.
Claims (7)
- A kind of 1. photovoltaic system earth-fault detecting method, it is characterised in that：Comprise the following steps：Step A：Create photovoltaic system SSTDR detection device a reference values；Step B：Obtain photovoltaic system earth fault error reference value；Step C：Photovoltaic system is scanned, calculates photovoltaic system earth fault deviation value；Step D：Judged whether that earth fault occurs according to photovoltaic system earth fault deviation value and predetermined threshold value.
- 2. a kind of photovoltaic system earth-fault detecting method according to claim 1, it is characterised in that in the step A SSTDR detection devices respectively with photovoltaic system dc bus and the earth be connected.
- 3. a kind of photovoltaic system earth-fault detecting method according to claim 1, it is characterised in that in the step A Photovoltaic system SSTDR detection devices a reference value be the computing cross-correlation result average value of incoming signal and reflected signal, represent For：In formula, CiIt is ith measured value, N=10 is pendulous frequency, CbFor average value.
- 4. a kind of photovoltaic system earth-fault detecting method according to claim 1, it is characterised in that in the step B Photovoltaic system error reference value be expressed as：In formula, T be incoming signal cycle, CRBelieve for incidence Number and reflected signal computing cross-correlation end value,CjIt is jth time measured value, M=10 is pendulous frequency, NrefFor CbWith CRThe area that the absolute value of difference is surrounded with time transverse axis.
- 5. a kind of photovoltaic system earth-fault detecting method according to claim 1, it is characterised in that the step A, step A reference value, reference value in rapid B are to be obtained in the no ground failure of photovoltaic system by testing.
- 6. a kind of photovoltaic system earth-fault detecting method according to claim 1, it is characterised in that in the step C Deviation value be expressed as,In formula, T be incoming signal cycle, CfFor computing cross-correlation under current state As a result average value,CkIt is kth time measured value, X=10 is pendulous frequency, and deviation value S is CbWith CfDifference The area that is surrounded of absolute value and time transverse axis.
- 7. a kind of photovoltaic system earth-fault detecting method according to claim 1, it is characterised in that in the step D A deviation value threshold value default with photovoltaic system compared with, be to occur earth fault and to send alarm more than threshold value, its Middle threshold value takes 2 times of Nref。
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| CN201810056839.5A CN107957528B (en) | 2018-01-19 | 2018-01-19 | Photovoltaic system ground fault detection method |
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| CN201810056839.5A CN107957528B (en) | 2018-01-19 | 2018-01-19 | Photovoltaic system ground fault detection method |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111610410A (en) * | 2020-05-27 | 2020-09-01 | 上海岩芯电子科技有限公司 | SSTDR technology-based photovoltaic cable sub-health detection and positioning method |
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| CN107340459A (en) * | 2016-11-24 | 2017-11-10 | 安徽江淮汽车集团股份有限公司 | A kind of DC Line Fault arc method for measuring and system |
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2018
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Patent Citations (6)
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| CN101387682A (en) * | 2008-10-27 | 2009-03-18 | 清华大学 | Single-phase earth fault detecting method based on residual current harmonic component |
| US20100188240A1 (en) * | 2009-01-29 | 2010-07-29 | Wells Charles H | Continuous condition monitoring of transformers |
| CN103499769A (en) * | 2013-09-23 | 2014-01-08 | 武汉大学 | Self-adaptive line selection method for single-phase earth fault of resonant earthed system |
| CN103913663A (en) * | 2014-04-21 | 2014-07-09 | 南京航空航天大学 | Online detection method and protection device for direct current system arc faults |
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| CN111610410A (en) * | 2020-05-27 | 2020-09-01 | 上海岩芯电子科技有限公司 | SSTDR technology-based photovoltaic cable sub-health detection and positioning method |
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