CN106684844B - A kind of power distribution network isolated island recognition methods - Google Patents
A kind of power distribution network isolated island recognition methods Download PDFInfo
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Classifications
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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
Abstract
The invention discloses a kind of power distribution network isolated island recognition methods, major network is primarily adapted for use in using low resistance grounding mode, distributed generation resource uses the active power distribution network of earth-free mode, carries out isolated island detection by detecting the variation of distributed generation resource grid entry point point, that is, PCC point residual voltage.No matter PCC dotted line voltage magnitude whether within the preset range, the present invention can quickly determine the position of singlephase earth fault according to the variation of PCC point residual voltage and carry out isolated island identification, and isolated island check frequency is smaller.
Description
Technical field
The present invention relates to power distribution network isolated island detection technique fields, more particularly to a kind of power distribution network isolated island recognition methods.
Background technique
Isolated island refers to that grid-connected system is not when power grid leads to power failure due to electric fault, maloperation etc.
It can detect power failure and be detached from power grid, continue to power to power grid, the load of grid-connected system and surrounding is made to constitute one
The isolated generating system of a uncontrolled self-energizing.Isolated operation can be divided into plan isolated island and unplanned isolated island.Plan isolated island
The positive effect of DG can be effectively played, the loss of power failure bring is reduced, improves power supply reliability；And unplanned isolated island may
It causes casualties, serious harm is caused to electrical equipment and user, threatens the safe and stable operation of electric system.Therefore,
It can fast and effeciently detect isolated island, the generation of non-island phenomenon is avoided to have very important significance entire grid-connected system.
Currently, the isolated island detection that experts and scholars have been directed to distributed generation system both at home and abroad is furtherd investigate, propose
A variety of island detection methods.According to detection position, these methods can be divided into two classes: the long-range detection method and distributed electrical of grid side
The local detection method of source.Long-range detection is main to detect isolated island using radio communication, needs to add equipment, economy
It is low, complicated for operation.Since input cost is higher, this kind of method is not yet used widely in small-sized DG, it is suitable for greatly
Power distributed generation resource it is grid-connected.Local detection is to detect isolated island by the monitoring end DG voltage and current signal, again can be into one
Step is divided into two kinds, and one is passive type methods, that is, passes through the directly variation of measurement DG output power or PCC point voltage or frequency
Variation is to determine whether occur isolated island；Another kind is proactive, i.e., injects and disturb to power grid, and passes through system caused by disturbance
Voltage, frequency and the corresponding change of impedance detect isolated island in system.Passive type method due to its without increase hardware circuit, at
Sheet is low, is easily achieved, therefore is widely used.
Common passive type isolated island detection technique mainly has: mistake/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 smaller, detection accuracy is higher,
But since this method introduces disturbance quantity, causes unnecessary transient response, decline distribution network electric energy quality；Its control algolithm
More complex, practical application is difficult；Under different load characteristics, there are great differences for detection effect, even fails when serious.Often
Active alone island detection technique mainly has: impedance measurement, reactance insertion, output power method of perturbation etc..
Cross/under-voltage isolated island detection method (OVP/UVP) refers to when PCC point voltage magnitude is not in preset normal working zone
Domain (U1, U2) when, make DG stop being incorporated into the power networks immediately by issuing control signal, to reach a kind of quilt of anti-islanding operation purpose
Dynamic formula isolated island detection method, U1、U2It is the voltage magnitude minimum that permission can be operated normally by the system for the technical standard order that generates electricity by way of merging two or more grid systems
Value and maximum value.Distributed grid-connected electricity generation system according to figure 1, when power grid operates normally, that is, circuit breaker Q F closure, this
When because power grid effect of clamping down on, the voltage of PCC point will not be abnormal.When isolated island occurs, circuit breaker Q F is disconnected, if DG is supplied
There is Δ P ≠ 0 in the active power of the active power and local load consumption answered, PCC point voltage magnitude will generate when unequal
Offset, if this offset is sufficiently large, it will be able to detect the generation of isolated island.This Method And Principle is simple, easy to accomplish, economical
Property is best, and on power quality without influence.It need to only be judged using existing detection parameters, be not required to additional any hardware electricity
Road.
But when the smaller i.e. system work of PCC point voltage magnitude offset is in the normal voltage range of permission, mistake/owe
Press isolated island detection method that will fail.Though this method is easy to accomplish but contains sizable check frequency.
Make a concrete analysis of about check frequency as follows: when DG uses 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 consumptionloadThe ratio between the active-power P provided with distributed power generation unit are as follows:
UPCCIndicate PCC point voltage effective value when DG is normally incorporated into the power networks, U 'PCCIndicate DG PCC in isolated operation
Point voltage effective value.
In the case of distributed generation system is normally incorporated into the power networks, power grid can be expressed to the active power that local load provides
At:
Δ P=Pload-P
The distributed generation system active power mismatch degree before island effect occurs are as follows:
When DG work is normally allowing voltage range (U1、U2) when, active power that power grid and DG are provided to local load
Ratio range is:
The distributed power generation unit island effect detection time standard according to as defined in China, when DG grid-connected system operates normally
Voltage magnitude upper lower limit value be U respectively2=110%Un、U1=85%Un, DG can be obtained in power limitation control mode by substituting into formula
Under mistake/under-voltage method isolated island check frequency (NDZ) are as follows:
Similarly, when DG uses constant current controlling mode, the range of system active power mismatch degree is before isolated island generates:
That is mistake/under-voltage method isolated island check frequency of the DG under constant current controlling mode are as follows:
In conclusion there is check frequency for traditional passive type isolated island detection technique in the prior art, still
Lack effective solution scheme.
Summary 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 generation resource
The problem of isolated island detects when singlephase earth fault, occurs for system, based on the analysis to traditional passive type island detection method, proposes
The variation of major network protection front and back DG grid entry point (PCC point) residual voltage is to determine whether occur isolated island when a kind of generation using failure
Detection scheme.The present invention takes into account passive type detection method principle simple, good economy performance, on power quality without influencing the advantages of,
It is the supplement of traditional passive type isolated island detection technique.
The present invention provides a kind of power distribution network isolated island recognition methods, are primarily adapted for use in major network and use low resistance grounding mode,
Distributed generation resource uses the active power distribution network of earth-free mode, by detecting distributed generation resource grid entry point point, that is, PCC point zero sequence
The variation of voltage carries out isolated island detection, comprising:
If PCC point residual voltage is always zero, system normal operation does not break down at this time；
If detecting, PCC point residual voltage amplitude is at a time sported by 0 more than or equal to threshold value Uset3Value, then
At this, singlephase earth fault occurs for etching system；
After failure continues for some time, if detecting, PCC point residual voltage continues to exist and is being 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 fault point is located at this time
In isolated island region, and system major network protection act after the failure occurred, form isolated island；
If detecting, PCC point residual voltage amplitude is more than or equal to U by the larger value beforeset3It sports and is less than threshold value
Uset4Value, then fault point is located at outside the isolated island region at this time, and system major network protection act after the failure occurred, 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 route, and PCC point is equipped with voltage
Mutual inductor, for detecting the residual voltage of PCC point.
Further, major network uses low resistance grounding mode in the active power distribution network, and DG uses earth-free mode, F1, F2
Indicate 2 different location fault points, wherein F1Between bus and the PCC point of route 1, F2Positioned at route 2, PCC point and bus
Distance be L；The distance of fault point to major network power supply is L1；The distance of fault point to PCC point is L2, R1For main net side neutral point
To ground resistance.
Further, when systems are functioning properly, circuit breaker Q F1, QF2 is failure to actuate, and PCC point residual voltage is always
Zero.
Further, it when singlephase earth fault occurs for system and fault point is located in isolated island region, is jumped in circuit breaker Q F1
Before opening, PCC point residual voltage amplitude is more than or equal to Uset1；QF1 tripping after a period of time, PCC point residual voltage continue
In the presence of and sport on the basis of the original more than or equal to Uset2Numerical value, can determine that form isolated island at this time according to the present invention.
Further, when fault point is located at outside isolated island region, before circuit breaker Q F2 tripping, PCC point residual voltage width
Value is more than or equal to Uset3；QF2 tripping after a period of time, PCC point residual voltage are less than Uset4, in the range of close to zero,
It can determine that according to the present invention and cut off failure at this time.
Further, in F1Singlephase earth fault occurs for point, before obtaining major network protection act, the small resistance containing rotary-type DG
Earthing mode distribution net work earthing fault compound sequence network figure obtains the positive sequence, negative phase-sequence, zero sequence impedance of major network side according to compound sequence network figure
And the positive sequence of the side DG, negative phase-sequence, zero sequence impedance, and the current in the fault point under DG grid connection state is calculated accordingly, and obtains PCC accordingly
Point residual voltage, when singlephase earth fault occurs, after major network protection act, breaker tripping, at this point, DG is together with surrounding
Load is formed together isolated island.
Further, when calculating the current in the fault point under DG grid connection state, it is contemplated that the DG capacity in access power distribution network
Smaller, grid-connected transformer and DG direct impedance are generally large, and the zero sequence impedance Z ' of the side DGa(0)For a biggish value, therefore
Have:
Wherein, Za(1)、Za(2)、Za(0)The respectively positive sequence, negative phase-sequence of major network side, zero sequence impedance, Z 'a(1)、Z’a(2)、Z’a(0)Point
Not Wei the side DG positive sequence, negative phase-sequence, zero sequence impedance.
Further, as system F2When A phase ground fault occurs for point, PCC point residual voltage is still before major network protection act
One biggish numerical value, after major network protection act, route 1 restores normal operating condition, does not contain zero sequence in route theoretically
Voltage considers that error influences, and PCC point residual voltage is within the scope of one close to zero at this time.
Further, the power distribution network isolated island recognition methods is complementary with existing mistake/under-voltage isolated island detection method content, when being
When system occurs singlephase earth fault and PCC dotted line voltage magnitude and exceeds preset normal operation range, no matter failure point
In outside in isolated island region or isolated island region, mistake/under-voltage detection method can quickly detect isolated island；
When fault point is located in isolated island region and DG capacity matches well with load capacity in isolated island region, mistake/under-voltage guarantor
When protection element tripping, since failure is not yet removed, PCC point residual voltage persistently exists, power distribution network isolated island recognition methods of the present invention
Isolated island can be accurately detected in mistake/under-voltage detection method failure.
Compared with prior art, the beneficial effects of the present invention are:
The present invention is compared with the long-range detection method of grid side, and the present invention is without increasing additional hardware circuit or independent
Protective relay, it is noiseless to power grid, on power quality without influence；Compared with proactive, the present invention is without introducing disturbance
Amount, will not cause unnecessary transient response, control principle is simple, easy to accomplish.
The present invention is complementary with existing mistake/under-voltage isolated island detection method content.When singlephase earth fault and PCC point occur for system
When line voltage amplitude exceeds preset normal operation range, no matter fault point is located in isolated island region or isolated island region
Outside, mistake/under-voltage detection method can all quickly detect isolated island.But when DG capacity matches good with load capacity in isolated island region,
Major network protection front and back PCC point voltage change very little, this variable quantity are not enough to start/under-voltage protection element, and isolated island detects just
It can fail；In addition, network voltage normal fluctuation causes to malfunction in order to prevent, mistake/under-voltage protection protection threshold value cannot be set
Set too low, caused/there are biggish check frequencies for under-voltage detection method.When fault point is located in isolated island region and in isolated island region
DG capacity matches well with load capacity, when mistake/under-voltage protection element tripping, since failure is not yet removed, and PCC point residual voltage
Lasting to exist, the present invention can accurately detect isolated island in mistake/under-voltage detection method failure.
In short, no matter PCC dotted line voltage magnitude whether within the preset range, the present invention can be according to PCC point zero sequence
The variation of voltage quickly determines the position of singlephase earth fault and carries out isolated island identification, and isolated island check frequency is smaller.The present invention
Major network is primarily adapted for use in using low resistance grounding mode, DG uses the active power distribution network of earth-free mode.
Detailed description of the invention
The accompanying drawings constituting a part of this application is used to provide further understanding of the present application, and the application's shows
Meaning property embodiment and its explanation are not constituted an undue limitation on the present application for explaining the application.
Fig. 1 is distributed grid-connected electricity generation system schematic diagram；
Fig. 2 is the mode of low resistance grounding containing DG distribution net work earthing fault schematic diagram；
Fig. 3 is containing rotary-type DG low resistance grounding 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 F1Locate failure PCC point residual voltage change curve；
Fig. 6 is Rf=5 Ω F1Locate failure 2.15-2.4s PCC point residual voltage change curve；
Fig. 7 is Rf=5 Ω F1Locate failure 7.15-7.4s PCC point residual voltage change curve；
Fig. 8 is Rf=5 Ω F2Locate failure PCC point residual voltage change curve；
Fig. 9 is Rf=5 Ω F2Locate failure 2.15-2.4s PCC point residual voltage change curve；
Figure 10 is Rf=50 Ω F1Locate failure PCC point residual voltage change curve；
Figure 11 is Rf=50 Ω F1Locate failure 2.15-2.4s PCC point residual voltage change curve；
Figure 12 is Rf=50 Ω F1Locate failure 7.15-7.4s PCC point residual voltage change curve；
Figure 13 is Rf=50 Ω F2Locate failure PCC point residual voltage change curve；
Figure 14 is Rf=50 Ω F2Locate failure 2.15-2.4s PCC point residual voltage change curve；
Figure 15 is Rf=100 Ω F1Locate failure PCC point residual voltage change curve；
Figure 16 is Rf=100 Ω F1Locate failure 2.15-2.4s PCC point residual voltage change curve；
Figure 17 is Rf=100 Ω F1Locate failure 7.15-7.4s PCC point residual voltage change curve；
Figure 18 is Rf=100 Ω F2Locate failure PCC point residual voltage change curve；
Figure 19 is Rf=100 Ω F2Locate failure 2.15-2.4s PCC point residual voltage change curve；
Figure 20 is Rf=500 Ω F1Locate failure PCC point residual voltage change curve；
Figure 21 is Rf=500 Ω F1Locate failure 2.15-2.4s PCC point residual voltage change curve；
Figure 22 is Rf=500 Ω F1Locate failure 7.15-7.4s PCC point residual voltage change curve；
Figure 23 is Rf=500 Ω F2Locate failure PCC point residual voltage change curve；
Figure 24 is Rf=500 Ω F2Locate failure 2.15-2.4s PCC point residual voltage change curve；
Figure 25 is Rf=1000 Ω F1Locate failure PCC point residual voltage change curve；
Figure 26 is Rf=1000 Ω F1Locate failure 2.15-2.4s PCC point residual voltage change curve；
Figure 27 is Rf=1000 Ω F1Locate failure 7.15-7.4s PCC point residual voltage change curve；
Figure 28 is Rf=1000 Ω F2Locate failure PCC point residual voltage change curve；
Figure 29 is Rf=1000 Ω F2Locate failure 2.15-2.4s PCC point residual voltage change curve.
Specific embodiment
It is noted that following detailed description is all illustrative, it is intended to provide further instruction to the application.Unless another
It indicates, all technical and scientific terms used herein has 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 singular
Also it is intended to include plural form, additionally, it should be understood that, when in the present specification using term "comprising" and/or " packet
Include " when, indicate existing characteristics, step, operation, device, component and/or their combination.
As background technique is introduced, existing mistake/under-voltage isolated island detection method exists in the prior art when isolated island area
When DG capacity matches good with load capacity in domain, major network protection front and back PCC point voltage change very little, this variable quantity is not enough to
Started/under-voltage protection element, isolated island detects the deficiency that will be failed, and in order to solve technical problem as above, the application is proposed
A kind of power distribution network isolated island recognition methods.
In a kind of typical embodiment of the application, a kind of power distribution network isolated island recognition methods is provided, 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 uses low resistance grounding mode, and DG uses earth-free mode.F1, F2Indicate 2 different location failures
Point, wherein F1Between bus and the PCC point of route 1, F2Positioned at route 2.PCC point is L at a distance from bus；Fault point is arrived
The distance of major network power supply is L1；The distance of fault point to PCC point is L2。R1It is main net side neutral point to ground resistance, domestic power grid one
As be 10 Ω.
Be equipped with breaker (QF) in the outlet of every route, be mainly made of 3 essential parts, i.e., contact, go out
Arc system and various buckle releasers, including overcurrent trip, decompression (under-voltage) buckle releaser, thermal trip, shunt release and
Automatically jumping device.
PCC point is equipped with voltage transformer, for detecting the residual voltage of PCC point.
Wherein, measurement is generally single phase two-line coil structures with voltage transformer, and original edge voltage is measured voltage, Ke Yidan
It mutually uses, V-V shape can also be connected into two and make three-phase use.Voltage transformer primary side is usually multi-tap, to adapt to survey
Measure the needs of different voltages.A tertiary coil, referred to as three-winding mutual induction of voltage are also had 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.When normal operation, the three-phase voltage of electric system is symmetrical, and the sum of three-phase induction electromotive force on tertiary coil is zero.
When singlephase earth fault occurs, neutral point is displaced, and just will detect that residual voltage between the terminal of open delta, and make relay
Device movement, to shield to electric system.Residual voltage, which occurs, in coil then just will appear zero sequence magnetic in corresponding iron core
It is logical.For this purpose, this threephase potential transformer is using return yoke formula iron core (10KV and following) or uses three single-phase potential transformers.
In order to enable those skilled in the art can clearly understand the technical solution of the application, below with reference to tool
The technical solution of the application is described in detail in the embodiment and comparative example of body.
F1Singlephase earth fault occurs for point:
With F1For A phase ground fault occurs for point, failure excessive resistance R is consideredf.Before major network protection act, containing rotary-type
DG low resistance grounding mode distribution net work earthing fault compound sequence network is as shown in Figure 3.In figure: ZS(1)And ZS(2)Respectively major network power supply
With the sum of the positive sequence of transformer, negative sequence impedance, ZS(1)=ZS(2)；ZS(0)For major network Zero-sequence Impedance for Earthing Transformer；ZTSimultaneously for the side DG
Net transformer impedance；ZL1(1)And ZL1(2)Respectively fault point is to the route positive sequence of major network power supply, negative sequence impedance, ZL1(1)=ZL1(2)；
ZL2(1)And ZL2(2)Respectively fault point is to the route positive sequence of PCC, negative sequence impedance, ZL2(1)=ZL2(2)；ZL1(0)And ZL2(0)Respectively
Fault point is to major network power supply, the route zero sequence impedance of PCC；ZDG(1)And ZDG(2)The positive sequence of respectively rotary-type DG, negative sequence impedance；The respectively positive sequence of major network side and the side DG, negative phase-sequence, zero-sequence fault electricity
Stream；For positive (negative or zero) the sequence electric current in fault point, it is equal to current in the fault point1/3；Arrow illustrates the reference side of each electric current
To；For fault point additional voltage source；ZNFor the side DG 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)It is respectively as follows:
The positive sequence of the side DG, negative phase-sequence, zero sequence impedance Z 'a(1)、Z’a(2)、Z’a(0)It is respectively as follows:
Current in the fault point under DG grid connection stateAre as follows:
In view of the DG capacity in access power distribution network is smaller, grid-connected transformer and DG direct impedance are generally large, and DG
The zero sequence impedance Z ' of sidea(0)For a biggish value, therefore generally have:
Current in the fault point at this time:
Major network side, the side DG zero-sequence current Ia(0), I 'a(0)The zero-sequence current and each side neutral point for being both each side line road are over the ground
Zero-sequence current (neutral point to earth-current 1/3), can indicate are as follows:
At this point, PCC point residual voltage are as follows:
When singlephase earth fault occurs for system, after major network protection act, circuit breaker Q F1 tripping, the compound sequence of system
Net is as shown in Figure 4.At this point, DG is formed together isolated island together with the load of surrounding.
At this point, PCC point residual voltage are as follows:
F2Singlephase earth fault occurs for point:
It can similarly analyze and obtain, as system F2When A phase ground fault occurs for point, PCC point zero sequence electricity before major network protection act
Pressure is still a biggish numerical value.After major network protection act, route 1 restores normal operating condition, is theoretically free of in route
There is a residual voltage, consider that error influences, PCC point residual voltage is within the scope of one close to zero at this time.
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 ground fault modeling and simulating, F to the low resistance grounding mode power distribution network containing DG1And F2Single-phase earthing event occurs for place
Hinder major network protection front and back PCC point residual voltage curve graph as shown in Fig. 5-Figure 29.
The specific working principle is as follows for system in above-mentioned Fig. 2:
When systems are functioning properly, circuit breaker Q F1, QF2 is failure to actuate, and PCC point residual voltage is always zero.
When singlephase earth fault occurs for system and fault point is located in isolated island region, before circuit breaker Q F1 tripping,
PCC point residual voltage amplitude is more than or equal to Uset1；QF1 tripping after a period of time, PCC point residual voltage continue exist and
It sports on the basis of originally more than or equal to Uset2Numerical value, can determine that form isolated island at this time according to the present invention.
When fault point is located at outside isolated island region, before circuit breaker Q F2 tripping, PCC point residual voltage amplitude is greater than etc.
In Uset3；QF2 tripping after a period of time, PCC point residual voltage are less than Uset4, in the range of close to zero, according to this hair
Bright can determine that cuts off failure at this time.
To sum up, when singlephase earth fault occurs for system and fault point is located in isolated island region, PCC before major network protection act
The amplitude for the secondary side residual voltage that point voltage transformer detects is more than or equal to threshold value Uset1(Uset1=105.7V)；Major network
Isolated island is formed after protection act, PCC point residual voltage persistently has and sport on the basis of the original bigger numerical value, mutation
Amplitude afterwards is more than or equal to threshold value Uset2(Uset2=2559V).
When fault point is located at outside isolated island region, the amplitude of PCC point residual voltage is more than or equal to door before major network protection act
Limit value Uset3(Uset3=75.84V)；The amplitude of PCC point residual voltage is sported less than threshold value U after major network protection actset4
(Uset4=15V) numerical value, in the range of close to zero.
The foregoing is merely preferred embodiment of the present application, are not intended to limit this application, for the skill of this field
For art personnel, various changes and changes are possible in this application.Within the spirit and principles of this application, made any to repair
Change, equivalent replacement, improvement etc., should be included within the scope of protection of this application.
Claims (9)
1. a kind of power distribution network isolated island recognition methods, characterized in that be primarily adapted for use in major network using low resistance grounding mode, distribution
Power supply uses the active power distribution network of earth-free mode, by the change for detecting distributed generation resource grid entry point, that is, PCC point residual voltage
Change to carry out isolated island detection, comprising:
If PCC point residual voltage is always zero, system normal operation does not break down at this time；
If detecting, PCC point residual voltage amplitude is at a time sported by 0 more than or equal to threshold value Uset3Value, then at this
When etching system occur singlephase earth fault；
After failure continues for some time, if detecting, PCC point residual voltage continues to exist and is being more than or equal to threshold value Uset1Base
Bigger value is sported on plinth again, the amplitude after mutation is more than or equal to threshold value Uset2, then fault point is located at isolated island area at this time
In domain, and system major network protection act after the failure occurred, form isolated island；
If detecting, PCC point residual voltage amplitude is more than or equal to U by the larger value beforeset3It sports and is less than threshold value Uset4's
Value, then fault point is located at outside the isolated island region at this time, and system major network protection act after the failure occurred, cuts off failure,
In, Uset2>Uset1>Uset3>Uset4；
The power distribution network isolated island recognition methods is complementary with existing mistake/under-voltage isolated island detection method content, when single-phase connect occurs for system
When earth fault and PCC dotted line voltage magnitude exceed preset normal operation range, no matter fault point is located in isolated island region
Or outside isolated island region, mistake/under-voltage detection method can quickly detect isolated island；
When fault point is located in isolated island region and DG capacity matches well with load capacity in isolated island region, mistake/under-voltage protection member
When part tripping, since failure is not yet removed, PCC point residual voltage persistently exists, and accurately examines in mistake/under-voltage detection method failure
Isolated island is measured, DG is distributed generation resource.
2. a kind of power distribution network isolated island recognition methods as described in claim 1, characterized in that the active power distribution network is in every line
It is circuit breaker Q F1, QF2 that the outlet on road, which is equipped with circuit breaker Q F, and PCC point is equipped with voltage transformer, for detecting PCC point
Residual voltage, circuit breaker Q F1 are located at 1 outlet of route, and circuit breaker Q F2 is located at 2 outlet of route.
3. a kind of power distribution network isolated island recognition methods as claimed in claim 2, characterized in that major network is adopted in the active power distribution network
With low resistance grounding mode, DG uses earth-free mode, and route 1, route 2, major network power supply are connected to bus, and PCC point is located at
On route 1, F1, F2Indicate 2 different location fault points, wherein F1Between route 1 and PCC point, F2Positioned at route 2, PCC
Point is L at a distance from bus；Fault point F1Distance to bus is L1；Fault point F1Distance to PCC point is L2, R1For main net side
Neutral point is to ground resistance.
4. a kind of power distribution network isolated island recognition methods as claimed in claim 3, characterized in that when systems are functioning properly, open circuit
Device QF1, circuit breaker Q F2 are failure to actuate, and PCC point residual voltage is always zero.
5. a kind of power distribution network isolated island recognition methods as claimed in claim 4, characterized in that when singlephase earth fault occurs for system
And fault point, when being located in isolated island region, before circuit breaker Q F1 tripping, PCC point residual voltage amplitude is more than or equal to Uset1；Through
QF1 tripping after a period of time, PCC point residual voltage persistently exist and are sported on the basis of the original more than or equal to Uset2's
Numerical value can determine that and form isolated island at this time.
6. a kind of power distribution network isolated island recognition methods as claimed in claim 4, characterized in that when fault point is located at outside isolated island region
When, before circuit breaker Q F2 tripping, PCC point residual voltage amplitude is more than or equal to Uset3；QF2 tripping after a period of time,
PCC point residual voltage is less than Uset4, in the range of close to zero, can determine that and cut off failure at this time.
7. a kind of power distribution network isolated island recognition methods as claimed in claim 4, characterized in that in F1Singlephase earth fault occurs for point,
Before obtaining major network protection act, obtained according to the distribution net work earthing fault compound sequence network figure containing rotary-type DG low resistance grounding mode
To the positive sequence of major network side, negative phase-sequence, zero sequence impedance and the positive sequence of the side DG, negative phase-sequence, zero sequence impedance, and DG grid connection state is calculated accordingly
Under current in the fault point, and obtain PCC point residual voltage accordingly, when singlephase earth fault occurs, after major network protection act,
Circuit breaker Q F1 tripping, at this point, DG is formed together isolated island together with the load of surrounding.
8. a kind of power distribution network isolated island recognition methods as claimed in claim 7, characterized in that the event in the case where calculating DG grid connection state
When barrier point electric current, it is contemplated that the DG capacity in access power distribution network is smaller, and grid-connected transformer and DG direct impedance are generally large, and
The zero sequence impedance Z ' of the side DGa(0)For a biggish value, therefore have:
Wherein, Za(1)、Za(2)、Za(0)The respectively positive sequence, negative phase-sequence of major network side, zero sequence impedance, Z 'a(1)、Z’a(2)、Z’a(0)Respectively
The positive sequence of the side DG, negative phase-sequence, zero sequence impedance.
9. a kind of power distribution network isolated island recognition methods as claimed in claim 3, characterized in that as system F2Point occurs A phase and is grounded event
When barrier, PCC point residual voltage is still a biggish numerical value before major network protection act, and after major network protection act, route 1 restores
Normal operating condition does not contain residual voltage theoretically in route, consider that error influences, PCC point residual voltage is at one at this time
Close within the scope of zero.
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| CN107328981B (en) * | 2017-08-11 | 2020-01-10 | 华北电力大学 | Method for analyzing fault voltage of neutral point of transformer |
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