CN101604838B - Method for optionally cutting off fault point of double branch circuits at low voltage side of transformer - Google Patents
Method for optionally cutting off fault point of double branch circuits at low voltage side of transformer Download PDFInfo
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- CN101604838B CN101604838B CN2009100698281A CN200910069828A CN101604838B CN 101604838 B CN101604838 B CN 101604838B CN 2009100698281 A CN2009100698281 A CN 2009100698281A CN 200910069828 A CN200910069828 A CN 200910069828A CN 101604838 B CN101604838 B CN 101604838B
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Abstract
The present invention belongs to a method for optionally cutting off a fault point of double branch circuits at the low voltage side of a transformer, which comprises the following steps of: (1) when earthed fault occurs, measuring instantaneous values of current I0 of an earthed neutral point and an triphase current of each branch at the low voltage side of the transformer; (2) calculating amplitude values of the I0 and zero-sequence current I01 and I02 of two branches at the lower voltage side of the transformer; (3) automatically analyzing the relation between the amplitude values of I0, I01 and I02; and (4) according to an analyzing result of the step (3), enabling a corresponding circuit breaker to actuate by sections and time delay to complete the cutoff of the failed branch. The method carries out discrimination by utilizing the distribution feature of zero-sequence fault current flowing through two branches at the low voltage side of the transformer when low-resistance earthed fault occurs and intelligently identifies the faulted branch circuit at the low voltage side of the transformer; and compared with the prior protection proposal, the method effectively shortens the load cutting range, improves the reliability of power supply for a user, reduces the blackout range caused when the earthed fault is earthed and changed into zero-sequence protecting action and protects the power load as large as possible.
Description
Technical field
The invention belongs to the grounding transformer zero-sequence current protection technical field of step down side, especially a kind of method of selecting to excise fault point in the step down side double branch circuits.
Background technology
Along with increasing rapidly of electric load; scale of power in the city is also constantly being carried out enlarging and is being extended; planned by the city; conditionality such as environmental protection and place; urban district electric substation adopts the cable feeder line more and more; so that the single-phase capacitive earth current of 10kV system increases considerably; the overvoltage amplitude that produces during for the inhibition single-phase earthing; increasing 10kV electrical network begins to adopt the low-impedance earthed system mode of connection; its earth fault current is about 400～600A; this mode of connection is when for the 10kV system ground connection being taken place; according to the earth point position; by corresponding zero-sequenceprotection earth fault is isolated; in case arc reignition causes overvoltage, guarantee to perfect in the electrical network safe power supply of equipment.The grounding transformer zero-sequenceprotection scheme of existing step down side is: protection is finished by the overcurrent relay of the current transformer that is connected to the ground connection change neutral line; its operation time limit is considered to match with the zero sequence overcurrent protection of 10kV feeder line; first time limit tripping 10kV section breaker and locking prepared auto restart; second time limit tripping main transformer low-side switch (can not establish this section time limit) according to actual conditions, each side switch of the 3rd time limit tripping main transformer.This method has formed good protection to step down side list branched line; can in time the fault point be excised with the protection miscellaneous equipment; but be that step down side has two branches than common structure at present; if still apply mechanically this moment when having grounding transformer zero-sequence current protection scheme now; the action in first time limit of zero-sequence current protection does not have selectivity; when breaking down; directly excise the section breaker of each branch of transformer; virtually the power consumption equipment in the non-fault branch is excised simultaneously; enlarged the power failure scope of earth fault; cause the unnecessary load of bus generation of the non-fault branch of step down side to lose phenomenon; reduced reliability, also caused user benefit impaired user's power supply.
Summary of the invention
The objective of the invention is to overcome the deficiencies in the prior art, provide easy and simple to handle, but intellectual analysis is judged step down side double branch circuits fault point, and automatic selectivity excision faulty line, avoids a kind of method of selecting to excise fault point in the step down side double branch circuits of unnecessary customer charge loss.
The present invention solves its technical problem and takes following technical scheme to realize:
A kind of method of selecting to excise fault point in the step down side double branch circuits, this method may further comprise the steps:
When (1) earth fault occurring, measure the grounded neutral electric current I
0, each branch's three-phase current of step down side instantaneous numerical value;
(2) calculate I
0, two branches of step down side zero-sequence current I
01And I
02Amplitude;
(3) analyze I automatically
0, I
01And I
02Amplitude between relation, criterion is as follows: the time
A. work as I
0＞I
0setThe time, if I
01＞I
0s1And I
01＞k * I
02The time, should excise a side branch;
B. work as I
0＞I
0setThe time, if I
02＞I
0s2And I
02＞k * I
01The time, should excise opposite side branch;
C. in the time can't satisfying step a and step b, should excise both sides branch;
Wherein,
I
0setBe zero sequence overcurrent protection definite value threshold, I
0s1Be a side branch earth fault minimum threshold electric current, I
0s2Be opposite side branch earth fault minimum threshold electric current, k is that two branch's zero-sequence currents are than width of cloth threshold coefficient.
(4) according to the analysis result fragment delay of step (3) and make the respective circuit breakers action to finish the excision of fault branch.
And, I
0setBe grounding transformer zero sequence overcurrent protection definite value, I
0s1Be the zero sequence overcurrent protection definite value in the side branch earth fault, I
0s2Be the zero sequence overcurrent protection definite value in the opposite side branch earth fault, k is that two branch's zero-sequence currents are than width of cloth threshold coefficient, k=1.5～2.
Advantage of the present invention and good effect are:
The distribution characteristics of the zero-sequence fault electric current that the present invention is flow through in two branches of step down side when utilizing the low-impedance earthed system fault to take place is differentiated; there is the branch road of fault in the Intelligent Recognition step down side; and then the section breaker of selectively preferential excision fault branch; if in the time of under certain malfunction, can't effectively identifying fault branch, keep and consistent processing of existing protection tripping operation scheme.Compare existing protection scheme, the present invention provides the Intelligence Selection of failure removal under the prerequisite that has guaranteed existing defencive function; effectively dwindled the load excision extension; improved user's power supply reliability, reduced the power failure scope that earth fault causes, the protection of maximum possible power load.
Description of drawings
Fig. 1 is two branches transformer connection schematic diagrames;
Fig. 2 is the decision logic figure of fault branch.
Embodiment
Embodiment of the present invention is illustrative; rather than it is determinate; therefore the present invention is not limited to the embodiment described in the embodiment, and every other execution modes that drawn by those skilled in the art's technical scheme according to the present invention belong to the scope of protection of the invention equally.
At present common step down side line construction as shown in Figure 1; low-pressure side has the A of branch and two branches of the B of branch; when the K1 among the figure～when K5 place anywhere broke down, existing protection scheme all can excise A of branch and the B of branch successively, can't intelligence judge the fault point.
The invention provides a kind of method of selecting to excise fault point in the step down side double branch circuits, its key step is: when earth fault occurring, at first measure grounding transformer Z
NThe zero-sequence current I of place branch road
0, and the instantaneous numerical value of three-phase current of A of branch and the B of branch, calculate I then
0, two branches zero-sequence current I
01And I
02Amplitude compare, when satisfying certain condition, which branch must be out of order occurs in, at last according to analysis and judgement fragment delay and make the respective circuit breakers action to finish the excision of fault branch as a result.
The concrete analysis deterministic process logical relation as shown in Figure 2,
A. work as I
0＞I
0setThe time, if I
01＞I
0s1And I
01＞k * I
02The time, should excise a side branch;
B. work as I
0＞I
0setThe time, if I
02＞I
0s2And I
02＞k * I
01The time, should excise opposite side branch;
C. in the time can't satisfying step a and step b, should excise both sides branch;
Wherein,
I
0setBe zero sequence overcurrent protection definite value, I
0s1Be the zero sequence overcurrent protection definite value (minimum threshold electric current) in the side branch earth fault, I
0s2Be the zero sequence overcurrent protection definite value (minimum threshold electric current) in the opposite side branch earth fault, k is that two branch's zero-sequence currents are than width of cloth threshold coefficient, k=1.5～2.
When satisfying step a, at T
S1After the time-delay, jump the DL3 circuit breaker, at T
S2After the time-delay, jump the DL1 circuit breaker, at T
S3After the time-delay, transformer is jumped entirely.
When satisfying step b, at T
S1After the time-delay, jump the DL4 circuit breaker, at T
S2After the time-delay, jump the DL2 circuit breaker, at T
S3After the time-delay, transformer is jumped entirely.
When can't step a and during step b, at T
S1After the time-delay, jump DL3, DL4 circuit breaker, at T
S2After the time-delay, jump DL1, DL2 circuit breaker, at T
S3After the time-delay, transformer is jumped entirely.
Application Example;
All 110/35/10KV rated capacity 75MW in the following application examples with the transformer, its 10kV low-pressure side Δ wiring is by grounding transformer ground connection, step down side has A of branch and the B of branch, the A of branch is provided with branch circuit breaker DL1 and bus section breaker DL3, and the B of branch is provided with branch circuit breaker DL2 and bus section breaker DL4.According to system parameters calculating with according to backup protection coordinated scheme, I
0set=100A, I
0s1=50A, I
0s2=50A, time-delay T
S1=0.5S, T
S2=0.6S, T
S3=0.7S, K=2.0.
When the earth fault generation took place in A branch somewhere, concrete control procedure was as follows:
(1) measures the grounded neutral electric current I
0, each branch's three-phase current of step down side instantaneous numerical value;
(2) calculate I under the short-circuit condition
0The zero-sequence current I of amplitude and two branches of step down side
01And I
02Amplitude be respectively: I
0=300A, I
01=270A, I
02=30A;
(3) analyze I
0, I
01And I
02Amplitude between relation, this moment I
0＞I
0set, I
01＞I
0s1And I
01＞k * I
02, should excise the A of branch.
Tripping operation is in proper order: at T
S1After=0.5S the time-delay, send out and jump the order of DL3 circuit breaker, at T
S2After=0.6S the time-delay, send out and jump the order of DL1 circuit breaker, at T
S3After=0.7S the time-delay, send out transformer and jump order entirely.
When the earth fault generation took place in B branch somewhere, concrete control procedure was as follows:
(1) measures the grounded neutral electric current I
0, each branch's three-phase current of step down side instantaneous numerical value;
(2) calculate I under the short-circuit condition
0The zero-sequence current I of amplitude and two branches of step down side
01And I
02Amplitude be respectively: I
0=300A, I
01=80A, I
02=220A;
(3) analyze I
0, I
01And I
02Amplitude between relation, this moment I
0＞I
0set, I
01＞I
0s1And I
02＞k * I
01, should excise the B of branch.
Tripping operation is in proper order: at T
S1After=0.5S the time-delay, send out and jump the order of DL4 circuit breaker, at T
S2After=0.6S the time-delay, send out and jump the order of DL2 circuit breaker, at T
S3After=0.7S the time-delay, send out transformer and jump order entirely.
When A and B branch the impedance earth fault all takes place took place, concrete control procedure was as follows:
(1) measures the grounded neutral electric current I
0, each branch's three-phase current of step down side instantaneous numerical value;
(2) calculate I under the short-circuit condition
0The zero-sequence current I of amplitude and two branches of step down side
01And I
02Amplitude be respectively: I
0=180A, I
01=80A, I
02=100A;
(3) analyze I
0, I
01And I
02Amplitude between relation, promptly do not satisfy I this moment
0＞I
0set, while I
02＞I
0s2And I
02＞k * I
01Condition, do not satisfy I yet
0＞I
0set, while I
02＞I
0s2And I
02＞k * I
01Condition, should excise A of branch and the B of branch simultaneously.
Tripping operation is in proper order: at T
S1After=0.5S the time-delay, send out and jump DL3, the order of DL4 circuit breaker, at T
S2After=0.6S the time-delay, send out and jump DL1, the order of DL2 circuit breaker, at T
S3After=0.7S the time-delay, transformer is jumped entirely.
In sum; the distribution characteristics of the zero-sequence fault electric current that the present invention is flow through in two branches of step down side when utilizing the low-impedance earthed system fault to take place is differentiated; there is the branch road of fault in the Intelligent Recognition step down side; and then the section breaker of selectively preferential excision fault branch; if in the time of under certain malfunction, can't effectively identifying fault branch, keep and consistent processing of existing protection tripping operation scheme.Compare the zero sequence overcurrent protection scheme of existing grounding transformer; the present invention is under the prerequisite that has guaranteed existing defencive function; the Intelligence Selection of failure removal is provided; effectively dwindled the load excision extension; improved user's power supply reliability; reduced the power failure scope that earth fault causes, the protection of maximum possible power load.
Claims (2)
1. the method that can select to excise fault point in the step down side double branch circuits, it is characterized in that: this method may further comprise the steps:
When (1) earth fault occurring, measure the grounded neutral electric current I
0, each branch's three-phase current of step down side instantaneous numerical value;
(2) calculate I
0, two branches of step down side zero-sequence current I
01And I
02Amplitude;
(3) analyze I automatically
0, I
01And I
02Amplitude between relation, criterion is as follows: when
A. work as I
0＞I
0setThe time, if I
01＞I
0s1And I
01＞k * I
02The time, should excise a side branch;
B. work as I
0＞I
0setThe time, if I
02＞I
0s2And I
02＞k * I
01The time, should excise opposite side branch;
C. in the time can't satisfying step a and step b, should excise both sides branch;
Wherein,
I
0setBe zero sequence overcurrent protection definite value threshold, I
0s1Be a side branch earth fault minimum threshold electric current, I
0s2Be opposite side branch earth fault minimum threshold electric current, k is that two branch's zero-sequence currents are than width of cloth threshold coefficient, k=1.5～2.
(4) according to the analysis result fragment delay of step (3) and make the respective circuit breakers action to finish the excision of fault branch.
2. a kind of method of selecting to excise fault point in the step down side double branch circuits according to claim 1 is characterized in that: I
0setBe grounding transformer zero sequence overcurrent protection definite value, I
0s1Be the zero sequence overcurrent protection definite value in the side branch earth fault, I
0s2Be the zero sequence overcurrent protection definite value in the opposite side branch earth fault, k is that two branch's zero-sequence currents are than width of cloth threshold coefficient, k=1.5～2.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2009100698281A CN101604838B (en) | 2009-07-22 | 2009-07-22 | Method for optionally cutting off fault point of double branch circuits at low voltage side of transformer |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2009100698281A CN101604838B (en) | 2009-07-22 | 2009-07-22 | Method for optionally cutting off fault point of double branch circuits at low voltage side of transformer |
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| Publication Number | Publication Date |
|---|---|
| CN101604838A CN101604838A (en) | 2009-12-16 |
| CN101604838B true CN101604838B (en) | 2011-09-14 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN2009100698281A Active CN101604838B (en) | 2009-07-22 | 2009-07-22 | Method for optionally cutting off fault point of double branch circuits at low voltage side of transformer |
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| AU2011223559B2 (en) * | 2010-03-05 | 2016-01-14 | Ambient Corporation | Evaluating noise and excess current on a power line |
| CN105119253A (en) * | 2015-09-14 | 2015-12-02 | 国家电网公司 | Demarcation switching zero-sequence current protection setting value calculation method |
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Owner name: JIANGSU WISCOM TECHNOLOGY CO., LTD. STATE GRID COR Free format text: FORMER OWNER: JIANGSU WISCOM TECHNOLOGY CO., LTD. Effective date: 20121128 |
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Effective date of registration: 20121128 Address after: 300010 Tianjin city Hebei District Wujing Road No. 39 Patentee after: Tianjin Electric Power Corp. Patentee after: Jinzhi Science and Technology Co., Ltd., Jiangsu Patentee after: State Grid Corporation of China Address before: 300010 Tianjin city Hebei District Wujing Road No. 39 Patentee before: Tianjin Electric Power Corp. Patentee before: Jinzhi Science and Technology Co., Ltd., Jiangsu |