CN106684844A - Island recognition method of distribution network - Google Patents
Island recognition method of distribution network Download PDFInfo
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- CN106684844A CN106684844A CN201710093512.0A CN201710093512A CN106684844A CN 106684844 A CN106684844 A CN 106684844A CN 201710093512 A CN201710093512 A CN 201710093512A CN 106684844 A CN106684844 A CN 106684844A
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
- H02H7/28—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured for meshed systems
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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
- G01R31/08—Locating faults in cables, transmission lines, or networks
- G01R31/081—Locating faults in cables, transmission lines, or networks according to type of conductors
- G01R31/086—Locating faults in cables, transmission lines, or networks according to type of conductors in power transmission or distribution networks, i.e. with interconnected conductors
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Abstract
The invention provides an island recognition method of distribution network, which is mainly suitable for the active distribution network adopting the main network with small grounding resistance and using the earth-free distributed power resource. Then the island detection is processed through testing the zero-sequence voltage changes of the grid entry points, also named PPC points, of the distributed power resource. The island recognition method of distribution network has the advantages that the blind zone becomes smaller and the position with the single-phase-to-ground fault can be determined quickly by the island recognition method of distribution network, according to the zero-sequence voltage changes of the PPC points, whether the voltage amplitude of the PPC points is in the preset range or not.
Description
Technical field
The present invention relates to power distribution network isolated island detection technique field, more particularly to a kind of power distribution network isolated island recognition methodss.
Background technology
Isolated island refers to that grid-connected system is not when electrical network causes power failure due to reasons such as electric fault, maloperations
Power down mode can be detected and depart from electrical network, continue to be powered to electrical network, the load for making grid-connected system and surrounding constitutes one
The isolated generating system of individual uncontrolled self-energizing.Islet operation can be divided into plan isolated island and unplanned isolated island.Plan isolated island
The positive role of DG can be effectively played, the loss for bringing that has a power failure is reduced, power supply reliability is improved；And unplanned isolated island may
Cause casualties, serious harm is caused to electrical equipment and user, threaten the safe and stable operation of power system.Therefore,
Isolated island can fast and effeciently be detected, it is to avoid the generation of non-island phenomenon has very important significance to whole grid-connected system.
At present, domestic and international experts and scholars have been for distributed generation system isolated island detection made further investigation, it is proposed that
Various island detection methods.According to test position, these methods can be divided into two classes：The remote detection method of grid side and distributed electrical
The local detection method of source.Remote detection mainly detects isolated island using radio communication, and it needs to add equipment, economy
Low, complex operation.Because input cost is higher, this kind of method is not yet used widely in small-sized DG, and it is suitable for greatly
Power distribution formula power supply it is grid-connected.Local detection is to detect isolated island by monitoring DG terminal voltages current signal, and it can enter one again
Step is divided into two kinds, and one kind is passive type method, i.e., by the change of direct measurement DG output or PCC point voltages or frequency
Change to judge whether isolated island；Another kind is proactive, i.e., disturb to electrical network injection, and is by what disturbance caused
The respective change of voltage, frequency and impedance is detecting isolated island in system.Passive type method due to its need not increase hardware circuit, into
This is low, be easily achieved, therefore is widely used.
Conventional passive type isolated island detection technique mainly has：Cross/under-voltage detection method (OVP/UVP), mistake/under-frequency detection method,
Voltage harmonic detection method, voltage-phase abrupt climatic change method etc..Although proactive check frequency is less, accuracy of detection is higher,
But because the method introduces disturbance quantity, cause unnecessary transient response, decline distribution network electric energy quality；Its control algolithm
More complicated, practical application is difficult；Under different load characteristics, there is very big difference in Detection results, even fail when serious.Often
Active alone island detection technique mainly has：Impedance measurement, reactance insertion, output method of perturbation etc..
Cross/under-voltage isolated island detection method (OVP/UVP) referred to when PCC point voltages amplitude is not in normal working zone set in advance
Domain (U1, U2) when, make DG stop being incorporated into the power networks immediately by sending control signal, to reach one kind quilt that anti-islanding runs purpose
Dynamic formula isolated island detection method, U1、U2It is the voltage magnitude minimum that permission can be normally run by the system of the technical standard order that generates electricity by way of merging two or more grid systems
Value and maximum.Distributed grid-connected electricity generation system according to Fig. 1, when electrical network normally runs, i.e. circuit breaker Q F is closed, this
When exception will not occur because of the effect of clamping down on of electrical network, the voltage of PCC points.When isolated island occurs, circuit breaker Q F disconnects, if DG is supplied
There is Δ P ≠ 0 in the active power answered, PCC point voltages amplitude will be produced when unequal with the active power of local load consumption
Skew, if this skew is sufficiently large, it becomes possible to detect the generation of isolated island.This Method And Principle simply, is easily realized, economy
Property preferably, and on the quality of power supply without impact.Only need to be judged using existing detection parameter, be not required to additional any hardware electricity
Road.
But, when it is that system is operated in the normal voltage range of permission that PCC point voltage magnitude shifts are less, mistake/owe
Pressure isolated island detection method will fail.Though the method is easily realized but containing sizable check frequency.
Make a concrete analysis of with regard to check frequency as follows：When DG adopts power limitation control mode, DG is in the feelings that are normally incorporated into the power networks
Under condition, the active-power P of local load consumptionloadIt is with the ratio of the active-power P of distributed power generation unit offer：
UPCCPCC point voltage virtual values when representing that DG is normally incorporated into the power networks, U 'PCCRepresent DG PCC in the case of islet operation
Point voltage virtual value.
In the case of distributed generation system is normally incorporated into the power networks, electrical network to the active power that local load is provided can be expressed
Into：
Δ P=Pload-P
Distributed generation system active power mismatch degree is before island effect occurs：
When DG is operated in normal permission voltage range (U1、U2) when, the active power that electrical network and DG are provided to local load
Ratio range is：
According to the distributed power generation unit island effect detection time standard that China specifies, when DG grid-connected systems normally run
Voltage magnitude upper lower limit value be respectively U2=110%Un、U1=85%Un, substituting into formula can obtain DG in power limitation control mode
Under the isolated island check frequency (NDZ) of mistake/under-voltage method be：
In the same manner, when DG adopts constant current controlling mode, isolated island produces the scope of front system active power mismatch degree is：
That is the isolated island check frequency of mistake/under-voltage methods of the DG under constant current controlling mode is：
In sum, for traditional passive type isolated island detection technique has check frequency in prior art, still
Lack effective solution.
The content of the invention
In order to solve the deficiencies in the prior art, it is an object of the invention to improve the low resistance grounding system containing distributed power source
There is the problem of isolated island detection during singlephase earth fault in system, based on the analysis to traditional passive type island detection method, it is proposed that
The change of one kind DG grid entry points (PCC points) residual voltage before and after major network protection when occurring using failure is judging whether generation isolated island
Detection scheme.The present invention takes into account passive type detection method principle simple, good economy performance, on the quality of power supply without the advantage for affecting,
It is the supplement of traditional passive type isolated island detection technique.
The invention provides a kind of power distribution network isolated island recognition methodss, are primarily adapted for use in major network using low resistance grounding mode,
Distributed power source adopts the active power distribution network of earth-free mode, by detecting that distributed power source grid entry point point is the zero sequence of PCC points
The change of voltage carrying out isolated island detection, including：
If PCC point residual voltages are always zero, now system normally do not break down by operation；
If detecting PCC point residual voltage amplitudes at a time to be sported more than or equal to threshold value U by 0set3Value, then
At this there is singlephase earth fault in etching system；
After failure is continued for some time, if detect PCC point residual voltages persistently existing and more than or equal to threshold value
Uset1On the basis of sport bigger value again, the amplitude after mutation be more than or equal to threshold value Uset2, then now trouble point is located at
In isolated island region, and the system major network protection act after failure occurs, form isolated island；
If detect PCC point residual voltage amplitudes is more than or equal to U by higher value beforeset3Sport less than threshold value
Uset4Value, then now trouble point be located at the isolated island region outside, and failure occur after system major network protection act, excision therefore
Barrier, wherein, Uset2>Uset1>Uset3>Uset4。
Further, the active power distribution network is equipped with circuit breaker Q F in the outlet of every circuit, and PCC points are provided with voltage
Transformer, for detecting the residual voltage of PCC points.
Further, major network adopts low resistance grounding mode, DG to adopt earth-free mode, F in the active power distribution network1, F2
Represent 2 diverse location trouble points, wherein F1Between the bus and PCC point of circuit 1, F2Positioned at circuit 2, PCC points and bus
Distance be L；Trouble point to the distance of major network power supply is L1；Trouble point to the distance of PCC points is L2, R1Based on net side neutral point
Resistance to earth.
Further, when systems are functioning properly, circuit breaker Q F1, QF2 is failure to actuate, and PCC point residual voltages are always
Zero.
Further, when system occurs singlephase earth fault and trouble point is located in isolated island region, jump in circuit breaker Q F1
Before opening, PCC point residual voltages amplitude is more than or equal to Uset1；The QF1 trippings after a period of time, PCC points residual voltage continues
Exist and sport more than or equal to U on the basis of originalset2Numerical value, can determine that according to the present invention and now formed isolated island.
Further, when trouble point is located at outside isolated island region, before the tripping of circuit breaker Q F2, PCC point residual voltage width
Value is more than or equal to Uset3；The QF2 trippings after a period of time, PCC points residual voltage is less than Uset4, close in the range of zero,
Can determine that according to the present invention and now cut off failure.
Further, in F1There is singlephase earth fault in point, before obtaining major network protection act, containing rotary-type DG small resistors
Earthing mode distribution net work earthing fault compound sequence network figure, according to compound sequence network figure positive sequence, negative phase-sequence, the zero sequence impedance of major network side are obtained
And positive sequence, negative phase-sequence, the zero sequence impedance of DG sides, and DG and the current in the fault point under net state are calculated accordingly, and PCC is obtained accordingly
Point residual voltage, when there is singlephase earth fault, after major network protection act, chopper tripping, now, DG is together with surrounding
Load forms together isolated island.
Further, in the current in the fault point under calculating DG and net state, it is contemplated that access the DG capacity in power distribution network
It is less, grid-connected transformator and DG direct impedances it is generally large, and the zero sequence impedance Z ' of DG sidesa(0)For a larger value, therefore
Have：
Wherein, Za(1)、Za(2)、Za(0)The respectively positive sequence of major network side, negative phase-sequence, zero sequence impedance, Z 'a(1)、Z’a(2)、Z’a(0)Point
Not Wei DG sides positive sequence, negative phase-sequence, zero sequence impedance.
Further, when system F2When point occurs A phase earth faults, PCC points residual voltage is still before major network protection act
One larger numerical value, after major network protection act, circuit 1 recovers normal operating condition, does not contain zero sequence in circuit in theory
Voltage, it is considered to error affect, now PCC point residual voltages at one close within the scope of zero.
Further, power distribution network isolated island recognition methodss and existing mistake/under-voltage isolated island detection method content is complementary, when being
When there is singlephase earth fault and PCC dotted lines voltage magnitude and exceed normal operation range set in advance in system, no matter trouble point position
In the isolated island region or outside isolated island region, mistake/under-voltage detection method can quick detection go out isolated island；
When trouble point, DG capacity is matched well with load capacity in isolated island region and in isolated island region, mistake/under-voltage guarantor
During protection element tripping, because failure is not yet removed, PCC point residual voltages are persistently present, power distribution network isolated island recognition methodss of the present invention
Isolated island can be exactly detected in mistake/under-voltage detection method when failing.
Compared with prior art, the invention has the beneficial effects as follows：
Compared with the remote detection method of grid side, the present invention need not increase extra hardware circuit or independent to the present invention
Protective relay, it is noiseless to electrical network, on the quality of power supply without impact；Compared with proactive, the present invention is without the need for introducing disturbance
Amount, will not cause unnecessary transient response, and control principle is simple, easily realizes.
It is of the invention complementary with existing mistake/under-voltage isolated island detection method content.When system occurs singlephase earth fault and PCC points
When line voltage amplitude exceeds normal operation range set in advance, no matter trouble point is located in isolated island region or isolated island region
Outward, mistake/under-voltage detection method all can quick detection go out isolated island.But when DG capacity matches good with load capacity in isolated island region,
PCC point voltages are varied less before and after major network protection, and this variable quantity is not enough to start/under-voltage protection element, and isolated island is detected just
Can fail；Additionally, in order to prevent line voltage normal fluctuation from causing the threshold value of misoperation, mistake/under-voltage protection protection to set
Put too low, caused/there is larger check frequency in under-voltage detection method.When trouble point is located in isolated island region and in isolated island region
DG capacity is matched well with load capacity, during mistake/under-voltage protection element tripping, because failure is not yet removed, and PCC point residual voltages
Persistently exist, the present invention can exactly detect isolated island in mistake/under-voltage detection method when failing.
In a word, no matter whether PCC dotted lines voltage magnitude is in the range of presetting, and the present invention can be according to PCC point zero sequences
The quick position for determining singlephase earth fault of change of voltage simultaneously carries out isolated island identification, and isolated island check frequency is less.The present invention
Major network is primarily adapted for use in using low resistance grounding mode, DG adopts the active power distribution network of earth-free mode.
Description of the drawings
The Figure of description for constituting the part of the application is used for providing further understanding of the present application, and the application's shows
Meaning property embodiment and its illustrated for explaining the application, does not constitute the improper restriction to the application.
Fig. 1 is distributed grid-connected electricity generation system schematic diagram；
Fig. 2 is the mode distribution net work earthing fault schematic diagram of low resistance grounding containing DG；
Fig. 3 is containing rotary-type DG low resistance groundings mode distribution net work earthing fault compound sequence network figure；
Fig. 4 is isolated island compound sequence network figure；
Fig. 5 is Rf=5 Ω F1Place's failure PCC point residual voltage change curve；
Fig. 6 is Rf=5 Ω F1Place's failure 2.15-2.4s PCC point residual voltage change curves；
Fig. 7 is Rf=5 Ω F1Place's failure 7.15-7.4s PCC point residual voltage change curves；
Fig. 8 is Rf=5 Ω F2Place's failure PCC point residual voltage change curve；
Fig. 9 is Rf=5 Ω F2Place's failure 2.15-2.4s PCC point residual voltage change curves；
Figure 10 is Rf=50 Ω F1Place's failure PCC point residual voltage change curve；
Figure 11 is Rf=50 Ω F1Place's failure 2.15-2.4s PCC point residual voltage change curves；
Figure 12 is Rf=50 Ω F1Place's failure 7.15-7.4s PCC point residual voltage change curves；
Figure 13 is Rf=50 Ω F2Place's failure PCC point residual voltage change curve；
Figure 14 is Rf=50 Ω F2Place's failure 2.15-2.4s PCC point residual voltage change curves；
Figure 15 is Rf=100 Ω F1Place's failure PCC point residual voltage change curve；
Figure 16 is Rf=100 Ω F1Place's failure 2.15-2.4s PCC point residual voltage change curves；
Figure 17 is Rf=100 Ω F1Place's failure 7.15-7.4s PCC point residual voltage change curves；
Figure 18 is Rf=100 Ω F2Place's failure PCC point residual voltage change curve；
Figure 19 is Rf=100 Ω F2Place's failure 2.15-2.4s PCC point residual voltage change curves；
Figure 20 is Rf=500 Ω F1Place's failure PCC point residual voltage change curve；
Figure 21 is Rf=500 Ω F1Place's failure 2.15-2.4s PCC point residual voltage change curves；
Figure 22 is Rf=500 Ω F1Place's failure 7.15-7.4s PCC point residual voltage change curves；
Figure 23 is Rf=500 Ω F2Place's failure PCC point residual voltage change curve；
Figure 24 is Rf=500 Ω F2Place's failure 2.15-2.4s PCC point residual voltage change curves；
Figure 25 is Rf=1000 Ω F1Place's failure PCC point residual voltage change curve；
Figure 26 is Rf=1000 Ω F1Place's failure 2.15-2.4s PCC point residual voltage change curves；
Figure 27 is Rf=1000 Ω F1Place's failure 7.15-7.4s PCC point residual voltage change curves；
Figure 28 is Rf=1000 Ω F2Place's failure PCC point residual voltage change curve；
Figure 29 is Rf=1000 Ω F2Place's failure 2.15-2.4s PCC point residual voltage change curves.
Specific embodiment
It is noted that described further below is all exemplary, it is intended to provide further instruction to the application.Unless another
Indicate, all technologies used herein and scientific terminology are with usual with the application person of an ordinary skill in the technical field
The identical meanings of understanding.
It should be noted that term used herein above is merely to describe specific embodiment, and be not intended to restricted root
According to the illustrative embodiments of the application.As used herein, unless the context clearly indicates otherwise, otherwise singulative
It is also intended to include plural form, additionally, it should be understood that, when in this manual using term "comprising" and/or " bag
Include " when, it indicates existing characteristics, step, operation, device, component and/or combinations thereof.
As background technology is introduced, there is existing mistake/under-voltage isolated island detection method in prior art when isolated island area
When DG capacity matches good with load capacity in domain, PCC point voltages are varied less before and after major network protection, and this variable quantity is not enough to
Started/under-voltage protection element, the deficiency that isolated island detection will fail, in order to solve technical problem as above, the application proposition
A kind of power distribution network isolated island recognition methodss.
In a kind of typical embodiment of the application, there is provided a kind of power distribution network isolated island recognition methodss, using the present invention
The mode active power distribution network schematic diagram of low resistance grounding containing DG of island detection method as shown in Fig. 2
Wherein major network adopts low resistance grounding mode, DG to adopt earth-free mode.F1, F2Represent 2 diverse location failures
Point, wherein F1Between the bus and PCC point of circuit 1, F2Positioned at circuit 2.PCC points are L with the distance of bus；Trouble point is arrived
The distance of major network power supply is L1；Trouble point to the distance of PCC points is L2。R1Based on net side neutral point resistance to earth, domestic electrical network one
As be 10 Ω.
Be equipped with chopper (QF) in the outlet of every circuit, it is mainly made up of 3 essential parts, i.e., contact, go out
Arc system and various electrical apparatus releases, including overcurrent trip, decompression (under-voltage) electrical apparatus release, thermal trip, shunt release and
Automatically jumping device.
PCC points are provided with voltage transformer, for detecting the residual voltage of PCC points.
Wherein, measurement voltage transformer is generally single phase two-line coil structures, its original edge voltage be tested voltage, Ke Yidan
Mutually use, it is also possible to be connected into V-V shapes with two and use as three-phase.Voltage transformer former limit is usually multitap, to adapt to survey
The needs of the different voltages of amount.A tertiary coil, referred to as three-winding mutual induction of voltage are also carried for protective grounding voltage transformer
Device.The tertiary coil of three-phase is connected into open-delta, two exits of open-delta and the pressure-wire of ground(preference) relay
Circle is connected.During normal operation, the three-phase voltage of power system is symmetrical, and the three-phase induction electromotive force sum on tertiary coil is zero.
During generation singlephase earth fault, there is displacement in neutral point, and residual voltage is just will detect that between the terminal of open delta, and makes relay
Device action, so as to shield to power system.There is residual voltage and then zero sequence magnetic just occurs in corresponding iron core in coil
It is logical.For this purpose, this threephase potential transformer is using return yoke formula unshakable in one's determination (10KV and following) or using three single-phase potential transformers.
In order that those skilled in the art can clearly understand the technical scheme of the application, below with reference to tool
The embodiment of body describes the technical scheme of the application in detail with comparative example.
F1There is singlephase earth fault in point：
With F1Point occurs as a example by A phase earth faults, it is considered to failure excessive resistance Rf.Before major network protection act, containing rotary-type
DG low resistance grounding mode distribution net work earthing fault compound sequence networks are as shown in Figure 3.In figure：ZS(1)And ZS(2)Respectively major network power supply
Positive sequence, negative sequence impedance sum with transformator, ZS(1)=ZS(2)；ZS(0)For major network Zero-sequence Impedance for Earthing Transformer；ZTFor DG sides simultaneously
Net transformer impedance；ZL1(1)And ZL1(2)Respectively trouble point to major network power supply circuit positive sequence, negative sequence impedance, ZL1(1)=ZL1(2)；
ZL2(1)And ZL2(2)Respectively trouble point to PCC circuit positive sequence, negative sequence impedance, ZL2(1)=ZL2(2)；ZL1(0)And ZL2(0)Respectively
Trouble point is to major network power supply, the circuit zero sequence impedance of PCC；ZDG(1)And ZDG(2)Positive sequence, the negative sequence impedance of respectively rotary-type DG；Respectively the positive sequence of major network side and DG sides, negative phase-sequence, zero-sequence fault are electric
Stream；For trouble point just (negative or zero) sequence electric current, equal to current in the fault point1/3；Arrow illustrates the reference side of each electric current
To；For trouble point additional voltage source；ZNFor DG sides neutral point zero sequence impedance over the ground, when DG is earth-free, | ZN|→∞；
For the equivalent capacity in isolated island.
The positive sequence of major network side, negative phase-sequence, zero sequence impedance Za(1)、Za(2)、Za(0)Respectively：
The positive sequence of DG sides, negative phase-sequence, zero sequence impedance Z 'a(1)、Z’a(2)、Z’a(0)Respectively：
Current in the fault point under DG and net stateFor：
It is less in view of the DG capacity accessed in power distribution network, grid-connected transformator and DG direct impedances it is generally large, and DG
The zero sequence impedance Z ' of sidea(0)For a larger value, therefore typically have：
Now current in the fault point：
Major network side, DG sides zero-sequence current Ia(0), I 'a(0)Be both the zero-sequence current on each side line road, be also each side neutral point over the ground
Zero-sequence current (neutral point to earth-current 1/3), can be expressed as：
Now, PCC points residual voltage is：
When there is singlephase earth fault in system, after major network protection act, the tripping of circuit breaker Q F1, the compound sequence of system
Net is as shown in Figure 4.Now, DG forms isolated island together with the load of surrounding.
Now, PCC points residual voltage is：
F2There is singlephase earth fault in point：
Can analyze in the same manner and draw, when system F2When there is A phase earth faults in point, PCC points zero sequence electricity before major network protection act
Pressure is still a larger numerical value.After major network protection act, circuit 1 recovers normal operating condition, does not contain in circuit in theory
Have residual voltage, it is considered to error affect, now PCC point residual voltages at one close within the scope of zero.
Excessive resistance R is taken respectivelyf=5 Ω, 50 Ω, 100 Ω, 500 Ω, 1000 Ω, L=20km, L1=10km, L2=
10km.R carries out earth fault modeling and simulating, F to the low resistance grounding mode power distribution network containing DG1And F2There is single-phase earthing event in place
PCC point residual voltage curve charts are as shown in Fig. 5-Figure 29 before and after barrier major network protection.
System concrete operating principle is as follows in above-mentioned Fig. 2：
When systems are functioning properly, circuit breaker Q F1, QF2 is failure to actuate, and PCC point residual voltages are always zero.
When there is singlephase earth fault in system and trouble point is located in isolated island region, before the tripping of circuit breaker Q F1,
PCC point residual voltages amplitude is more than or equal to Uset1；The QF1 trippings after a period of time, PCC point residual voltages persistently exist and
Sport more than or equal to U on the basis of originallyset2Numerical value, can determine that according to the present invention and now formed isolated island.
When trouble point is located at outside isolated island region, before the tripping of circuit breaker Q F2, PCC point residual voltages amplitude is more than etc.
In Uset3；The QF2 trippings after a period of time, PCC points residual voltage is less than Uset4, close in the range of zero, according to this
Bright can determine that now cut off failure.
To sum up, when system occurs singlephase earth fault and trouble point is located in isolated island region, PCC before major network protection act
The amplitude of the secondary side residual voltage that point voltage transformer is detected is more than or equal to threshold value Uset1(Uset1=105.7V)；Major network
Isolated island is formed after protection act, PCC point residual voltages persistently exist and sport bigger numerical value on the basis of original, are mutated
Amplitude afterwards is more than or equal to threshold value Uset2(Uset2=2559V).
When trouble point is located at outside isolated island region, the amplitude of PCC points residual voltage is more than or equal to door before major network protection act
Limit value Uset3(Uset3=75.84V)；The amplitude of PCC points residual voltage is sported less than threshold value U after major network protection actset4
(Uset4=15V) numerical value, close in the range of zero.
The preferred embodiment of the application is the foregoing is only, the application is not limited to, for the skill of this area
For art personnel, the application can have various modifications and variations.It is all within spirit herein and principle, made any repair
Change, equivalent, improvement etc., should be included within the protection domain of the application.
Claims (10)
1. a kind of power distribution network isolated island recognition methodss, is characterized in that, be primarily adapted for use in major network using low resistance grounding mode, distributed
Power supply adopts the active power distribution network of earth-free mode, by detecting that distributed power source grid entry point point is the residual voltage of PCC points
Change to carry out isolated island detection, including：
If PCC point residual voltages are always zero, now system normally do not break down by operation；
If detecting PCC point residual voltage amplitudes at a time to be sported more than or equal to threshold value U by 0set3Value, then at this
When etching system occur singlephase earth fault；
After failure is continued for some time, if detect PCC point residual voltages persistently existing and more than or equal to threshold value Uset1Base
Sport bigger value on plinth again, the amplitude after mutation is more than or equal to threshold value Uset2, then now trouble point is located at isolated island area
In domain, and the system major network protection act after failure occurs, form isolated island；
If detect PCC point residual voltage amplitudes is more than or equal to U by higher value beforeset3Sport less than threshold value Uset4's
Value, then now trouble point is located at outside the isolated island region, and the system major network protection act after failure occurs, and cuts off failure, its
In, Uset2>Uset1>Uset3>Uset4。
2. a kind of power distribution network isolated island recognition methodss as claimed in claim 1, is characterized in that, the active power distribution network is in every line
The outlet on road is equipped with circuit breaker Q F, and PCC points are provided with voltage transformer, for detecting the residual voltage of PCC points.
3. a kind of power distribution network isolated island recognition methodss as claimed in claim 1, is characterized in that, major network is adopted in the active power distribution network
Low resistance grounding mode, DG is used to adopt earth-free mode, F1, F2Represent 2 diverse location trouble points, wherein F1Positioned at circuit 1
Between bus and PCC points, F2Positioned at circuit 2, PCC points are L with the distance of bus；Trouble point to the distance of major network power supply is L1；Therefore
Barrier point to the distance of PCC points is L2, R1Based on net side neutral point resistance to earth.
4. a kind of power distribution network isolated island recognition methodss as claimed in claim 3, is characterized in that, when systems are functioning properly, open circuit
Device QF1, QF2 are failure to actuate, and PCC point residual voltages are always zero.
5. a kind of power distribution network isolated island recognition methodss as claimed in claim 4, is characterized in that, when system occurs singlephase earth fault
And trouble point be located at isolated island region in when, before the tripping of circuit breaker Q F1, PCC point residual voltages amplitude be more than or equal to Uset1；Jing
QF1 trippings after a period of time, PCC point residual voltages persistently exist and sport more than or equal to U on the basis of originalset2's
Numerical value, can determine that according to the present invention and now formed isolated island.
6. a kind of power distribution network isolated island recognition methodss as claimed in claim 4, is characterized in that, when trouble point is located at outside isolated island region
When, before the tripping of circuit breaker Q F2, PCC point residual voltages amplitude is more than or equal to Uset3；The QF2 trippings after a period of time,
PCC points residual voltage is less than Uset4, close in the range of zero, can determine that according to the present invention and now cut off failure.
7. a kind of power distribution network isolated island recognition methodss as claimed in claim 4, is characterized in that, in F1There is singlephase earth fault in point,
Before obtaining major network protection act, containing rotary-type DG low resistance groundings mode distribution net work earthing fault compound sequence network figure, according to multiple
Positive sequence, negative phase-sequence, zero sequence impedance that sequence diagrams obtain positive sequence, negative phase-sequence, zero sequence impedance and the DG sides of major network side are closed, and is calculated accordingly
Current in the fault point under DG and net state, and PCC point residual voltages are obtained accordingly, when there is singlephase earth fault, major network is protected
After shield action, chopper tripping, now, DG forms isolated island together with the load of surrounding.
8. a kind of power distribution network isolated island recognition methodss as claimed in claim 3, is characterized in that, the event in the case where DG and net state is calculated
During barrier point electric current, it is contemplated that the DG capacity accessed in power distribution network is less, and grid-connected transformator and DG direct impedances are generally large, and
The zero sequence impedance Z ' of DG sidesa(0)For a larger value, therefore have：
Wherein, Za(1)、Za(2)、Za(0)The respectively positive sequence of major network side, negative phase-sequence, zero sequence impedance, Z 'a(1)、Z’a(2)、Z’a(0)Respectively
The positive sequence of DG sides, negative phase-sequence, zero sequence impedance.
9. a kind of power distribution network isolated island recognition methodss as claimed in claim 3, is characterized in that, when system F2Event be grounded and A phases in point there is
During barrier, PCC points residual voltage is still a larger numerical value before major network protection act, and after major network protection act, circuit 1 recovers
Normal operating condition, does not contain residual voltage in circuit in theory, it is considered to which error affects, and now PCC point residual voltages are at one
Close within the scope of zero.
10. a kind of power distribution network isolated island recognition methodss as claimed in claim 1, is characterized in that, the power distribution network isolated island identification side
Method and existing mistake/under-voltage isolated island detection method content is complementary, when system occurs singlephase earth fault and PCC dotted lines voltage magnitude is super
When going out normal operation range set in advance, no matter trouble point is located in isolated island region or outside isolated island region, mistake/under-voltage detection
Method can quick detection go out isolated island；
When trouble point, DG capacity is matched well with load capacity in isolated island region and in isolated island region, mistake/under-voltage protection unit
During part tripping, because failure is not yet removed, PCC point residual voltages are persistently present, and examine exactly when failing in mistake/under-voltage detection method
Measure isolated island.
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