CN104934930A - Differential protection speed-up method for unsymmetrical fault during oscillation - Google Patents
Differential protection speed-up method for unsymmetrical fault during oscillation Download PDFInfo
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- CN104934930A CN104934930A CN201410097788.2A CN201410097788A CN104934930A CN 104934930 A CN104934930 A CN 104934930A CN 201410097788 A CN201410097788 A CN 201410097788A CN 104934930 A CN104934930 A CN 104934930A
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- sequence current
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Abstract
The invention relates to a protection method in the field of power transmission and transformation, and specifically relates to a differential protection speed-up method for an unsymmetrical fault during oscillation. The method comprises the following steps: (1) connecting a determining element during the start of differential protection, and determining negative sequence currents of differential protection branch circuits; (2) enabling the differential protection branch circuit with the highest negative sequence current amplitude to be equivalent to a virtual branch K; (3) summing the negative sequence currents of other differential protection branch circuits except the differential protection branch circuit with the highest negative sequence current amplitude, and enabling the summed negative sequence current branch to be equivalent to a virtual branch T; (4) connecting negative sequence current direction elements of the two virtual branches K and T to judge a fault position, and judging whether the locking differential protection is carried out or not according to the fault position. The method can achieve the quick collection and calculation of the negative sequence currents of all branches, can effectively recognize whether a fault point is within a differential protection region or not, can carry out speed-up differential protection operation in needs, and brings favorable influences to a power transmission and transformation system. The method is accurate in determination, is easy to implement, and is good in application prospect.
Description
Technical field
The present invention relates to the guard method in power transmission and transformation field, be specifically related to unbalanced fault differential protection accelerated method in a kind of vibration.
Background technology
Differential protection is a kind of important short-circuit protection, and its structure, operation principle are simple, affect less, be therefore widely used in electric power system by load current.The ratio brake curve that current differential protection generally adopts difference stream to compare with stalling current is for differentiating internal fault external fault, and when system oscillation, stalling current becomes with sexual intercourse cycle of oscillation, and alternation amplitude is very large.There is unbalanced fault in period, differential protection easily can not quick acting by the locking of ratio brake curve.Under serious conditions, system oscillation is worsened, even cause the situations such as system splitting, bring very large harm to power system operation.How under reliable prerequisite, the operate time of accelerating differential protection is the focus of research always.Utilize self simple feature of periphery negative-sequence current direction, fault point; in conjunction with differential protection each associated branch negative-sequence current information; the change of total calculation analysis grounding point position and the relation of negative-sequence current sequence net changes in distribution; obtain a kind of method can accelerating differential protection action, bring favorable influence for power system safety and stability runs.
Summary of the invention
For the deficiencies in the prior art, the object of this invention is to provide unbalanced fault differential protection accelerated method in one vibration, when an error occurs by calculating the size of each branch road negative-sequence current, sorting virtual two branches of n branch road equivalence one-tenth.Then the direction of virtual two branch's negative-sequence currents, amplitude failure judgement point position is calculated.Accelerate differential protection element according to analysis result, excise fault rapidly, bring favorable influence to power transmission and transformation system.
The object of the invention is to adopt following technical proposals to realize:
The invention provides unbalanced fault differential protection accelerated method in a kind of vibration, its improvements are, described method comprises the steps:
(1), when differential protection starts, drop into discriminating element, determine the negative-sequence current of differential protection branch road;
(2) branch road of negative-sequence current amplitude maximum is equivalent to virtual branch K;
(3) by the summation of the negative-sequence current of other branch road except negative-sequence current amplitude maximum branch road, virtual branch T should be equivalent to negative-sequence current branch road;
(4) drop into virtual two branch K and T negative-sequence current direction component failure judgement point position, and judge whether Blocking Differential Protection according to position of failure point.
Further, in described step (1), determine the negative-sequence current I of differential protection n bar branch road
i, i=1,2 ... n.
Further, in described step (2), compare the amplitude of n bar branch road negative-sequence current, choose negative-sequence current amplitude maximum I
mx=max{I
1, I
2... I
n, work as I
mx> I
ywtime, be equivalent virtual branch K, described I by negative-sequence current amplitude maximum branch road
ywfor current threshold; The negative-sequence current of described virtual branch K is designated as I
mx.
Further, in described step (3), calculate other branch road negative phase-sequence and the electric current except negative-sequence current amplitude maximum branch road, other branch road negative phase-sequence and current branch are equivalent to virtual branch T, and the negative-sequence current of described virtual branch T is designated as I
ot,
work as I
ot> I
ywtime, calculate negative-sequence current direction component
wherein:
with
the negative-sequence current vector of the virtual branch T of negative-sequence current vector being with directive virtual branch K respectively.
Further, in described step (4), following situation is comprised:
1. when the negative-sequence current of virtual two branch K and T is in the other direction, and | I
mx| ≈ | I
ot|, meet
then failure judgement point is outside differential protection district, i.e. unbalanced fault outside generating region, now Blocking Differential Protection action; Described θ
1for the reverse threshold value of direction component;
2. the negative-sequence current angle homologous ray negative sequence impedance angle of virtual two branch K with T is relevant, and when each branch road negative sequence impedance angle is equal, the negative-sequence current of virtual two branch K and T is equidirectional, and meets
then failure judgement point is in differential protection district, i.e. unbalanced fault in generating region, now accelerates differential protection action; Described θ
2for direction component positive threshold.
Compared with the prior art, the beneficial effect that the present invention reaches is:
1, unbalanced fault differential protection accelerated method in vibration provided by the invention; collection can be carried out to differential each branch road negative-sequence current fast to calculate; effectively can identify whether fault point is positioned at differential protection district, accelerate differential protection action if desired, bring favorable influence to power transmission and transformation system.
2, the present invention adopts the amplitude of more each branch road negative-sequence current, chooses I
mx=max{I
1, I
2... I
n, and I
mx> I
yw, remember that this branch road is equivalent branch K.Calculate adjacent legs negative phase-sequence and electric current
and work as I
ot> I
ywtime calculate negative-sequence current direction
discriminating direction position of failure point accordingly, simple, accurate, quick.
3, the present invention calculates negative-sequence current direction component not by the impact of system oscillation, compares, significantly can improve differential protection responsiveness in vibration with conventional ratio brake curve.
4, computation model of the present invention (
) simplicity of design, Fault Identification realizes quick, can be widely used in all kinds of differential protection such as transformer differential protection, bus differential protecting.
5, the present invention differentiates accurately, is easy to realize, and possesses good prospect of the application.
6, troubles inside the sample space in vibration, action postpones relevant with cycle of oscillation obviously with delay operate time for conventional ratio brake differential protection, in electric current crest fault under extreme case, action delay even reach nearly half cycle of oscillation duration.Conventional ratio brake differential protection and the comparison of negative-sequence current direction component operating characteristics; sample frequency is 4000(point/second); conventional ratio brake differential protection 150ms action after earth fault in district (corresponding sampled point number 600 point), and there is i.e. opening in 10ms in fault in negative-sequence current direction component.
Accompanying drawing explanation
Fig. 1 is the flow chart of unbalanced fault differential protection accelerated method in vibration provided by the invention;
Fig. 2 is the conventional ratio brake of earth fault and negative-sequence current direction component operating characteristics comparison chart in district in vibration provided by the invention;
Fig. 3 is the conventional ratio brake of three-phase fault and negative-sequence current direction component operating characteristics comparison chart in district in vibration provided by the invention.
Embodiment
Below in conjunction with accompanying drawing, the specific embodiment of the present invention is described in further detail.
When electrical network generation unbalanced fault, negative phase-sequence sequence diagrams shows that the change along with earth point position changes.According to negative phase-sequence electrical network, when fault occurs, negative-sequence current direction is for flow to system from fault point.When troubles inside the sample space, each branch road negative-sequence current outwards flows out centered by troubles inside the sample space point, and each branch road negative-sequence current direction is close, and concrete angular difference is relevant with branch roads system negative sequence impedance angle.When external area error, negative-sequence current outwards flows out centered by external area error point, and virtual two branch road negative-sequence current directions are contrary.Can failure judgement point position according to negative-sequence current direction, when confirming that position of failure point is in differential protection district, accelerate differential protection action, excision fault, safeguards power system stability.
The invention provides unbalanced fault differential protection accelerated method in a kind of vibration, its flow chart as shown in Figure 1, comprises the steps:
(1), when differential protection starts, drop into discriminating element, determine the negative-sequence current I of differential protection n bar branch road
i, i=1,2 ... n.
(2) compare the amplitude of n bar branch road negative-sequence current, choose negative-sequence current amplitude maximum I
mx=max{I
1, I
2... I
n, work as I
mx> I
ywtime, be equivalent virtual branch K, described I by negative-sequence current amplitude maximum branch road
ywfor current threshold; The negative-sequence current of described virtual branch K is designated as I
mx.
(3) calculate other branch road negative phase-sequence and the electric current except negative-sequence current amplitude maximum branch road, other branch road negative phase-sequence and current branch are equivalent to virtual branch T, and the negative-sequence current of described virtual branch T is designated as I
ot,
work as I
ot> I
ywtime, calculate negative-sequence current direction component
wherein:
with
the negative-sequence current vector of the virtual branch T of negative-sequence current vector being with directive virtual branch K respectively.
(4) drop into virtual two branch K and T negative-sequence current direction component failure judgement point position, and judge whether Blocking Differential Protection according to position of failure point, comprise following situation:
1. when the negative-sequence current of virtual two branch K and T is in the other direction, and | I
mx| ≈ | I
ot|, meet
then failure judgement point is outside differential protection district, i.e. unbalanced fault outside generating region, now Blocking Differential Protection action; Described θ
1for the reverse threshold value of direction component;
2. the negative-sequence current angle homologous ray negative sequence impedance angle of virtual two branch K with T is relevant, and when each branch road negative sequence impedance angle is equal, the negative-sequence current of virtual two branch K and T is equidirectional, and meets
then failure judgement point is in differential protection district, i.e. unbalanced fault in generating region, now can accelerate differential protection action; Described θ
2for direction component positive threshold.
Current threshold I wherein
yw, the reverse threshold value θ of direction component
1with direction component positive threshold θ
2all can artificially set.
Embodiment
Troubles inside the sample space in vibration, action postpones relevant with cycle of oscillation obviously with delay operate time for conventional ratio brake differential protection, in electric current crest fault under extreme case, action delay even reach nearly half cycle of oscillation duration.Conventional ratio brake differential protection shown in Fig. 2 and the comparison of negative-sequence current direction component operating characteristics; sample frequency is 4000(point/second); conventional ratio brake differential protection 150ms action after earth fault in district (corresponding sampled point number 600 point), and there is i.e. opening in 10ms in fault in negative-sequence current direction component.
Conventional ratio brake differential protection shown in Fig. 3 and the comparison of negative-sequence current direction component operating characteristics; sample frequency is 4000(point/second); conventional ratio brake differential protection 170ms action after three-phase fault in district (corresponding sampled point number 680 point), and there is non-synchronous failure phase opening in initial 20ms in fault in negative-sequence current direction component.
Finally should be noted that: above embodiment is only in order to illustrate that technical scheme of the present invention is not intended to limit, although with reference to above-described embodiment to invention has been detailed description, those of ordinary skill in the field are to be understood that: still can modify to the specific embodiment of the present invention or equivalent replacement, and not departing from any amendment of spirit and scope of the invention or equivalent replacement, it all should be encompassed in the middle of right of the present invention.
Claims (5)
1. a unbalanced fault differential protection accelerated method in vibration, it is characterized in that, described method comprises the steps:
(1), when differential protection starts, drop into discriminating element, determine the negative-sequence current of differential protection branch road;
(2) branch road of negative-sequence current amplitude maximum is equivalent to virtual branch K;
(3) by the summation of the negative-sequence current of other branch road except negative-sequence current amplitude maximum branch road, virtual branch T should be equivalent to negative-sequence current branch road;
(4) drop into virtual two branch K and T negative-sequence current direction component failure judgement point position, and judge whether Blocking Differential Protection according to position of failure point.
2. unbalanced fault differential protection accelerated method as claimed in claim 1, is characterized in that, in described step (1), determine the negative-sequence current I of differential protection n bar branch road
i, i=1,2 ... n.
3. unbalanced fault differential protection accelerated method as claimed in claim 1, is characterized in that, in described step (2), compare the amplitude of n bar branch road negative-sequence current, choose negative-sequence current amplitude maximum I
mx=max{I
1, I
2... I
n, work as I
mx> I
ywtime, be equivalent virtual branch K, described I by negative-sequence current amplitude maximum branch road
ywfor current threshold; The negative-sequence current of described virtual branch K is designated as I
mx.
4. unbalanced fault differential protection accelerated method as claimed in claim 1; it is characterized in that; in described step (3); calculate other branch road negative phase-sequence and the electric current except negative-sequence current amplitude maximum branch road; other branch road negative phase-sequence and current branch are equivalent to virtual branch T, and the negative-sequence current of described virtual branch T is designated as I
ot,
work as I
ot> I
ywtime, calculate negative-sequence current direction component
wherein:
with
the negative-sequence current vector of the virtual branch T of negative-sequence current vector being with directive virtual branch K respectively.
5. unbalanced fault differential protection accelerated method as claimed in claim 1, is characterized in that, in described step (4), comprise following situation:
1. when the negative-sequence current of virtual two branch K and T is in the other direction, and | I
mx| ≈ | I
ot|, meet
then failure judgement point is outside differential protection district, i.e. unbalanced fault outside generating region, now Blocking Differential Protection action; Described θ
1for the reverse threshold value of direction component;
2. the negative-sequence current angle homologous ray negative sequence impedance angle of virtual two branch K with T is relevant, and when each branch road negative sequence impedance angle is equal, the negative-sequence current of virtual two branch K and T is equidirectional, and meets
then failure judgement point is in differential protection district, i.e. unbalanced fault in generating region, now accelerates differential protection action; Described θ
2for direction component positive threshold.
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|---|---|---|---|
| CN201410097788.2A CN104934930B (en) | 2014-03-17 | 2014-03-17 | Unbalanced fault differential protection accelerated method in a kind of vibration |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201410097788.2A CN104934930B (en) | 2014-03-17 | 2014-03-17 | Unbalanced fault differential protection accelerated method in a kind of vibration |
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| CN104934930A true CN104934930A (en) | 2015-09-23 |
| CN104934930B CN104934930B (en) | 2018-05-29 |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106019155A (en) * | 2016-07-08 | 2016-10-12 | 清华大学 | Phase comparison type differential protection method and system based on generator branch current |
| CN107102192A (en) * | 2017-04-28 | 2017-08-29 | 许继集团有限公司 | A kind of full phase asynchronous oscillation method of discrimination and device |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20110163777A1 (en) * | 2008-07-17 | 2011-07-07 | Siemens Aktiengesellschaft | Method for production of a fault signal, and an electrical protective device |
| CN103323742A (en) * | 2013-05-31 | 2013-09-25 | 华北电力大学 | System and method for grid fault identification based on random point distribution PMU |
-
2014
- 2014-03-17 CN CN201410097788.2A patent/CN104934930B/en active Active
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20110163777A1 (en) * | 2008-07-17 | 2011-07-07 | Siemens Aktiengesellschaft | Method for production of a fault signal, and an electrical protective device |
| CN103323742A (en) * | 2013-05-31 | 2013-09-25 | 华北电力大学 | System and method for grid fault identification based on random point distribution PMU |
Non-Patent Citations (1)
| Title |
|---|
| 柳焕章等: "继电保护振荡闭锁的改进措施", 《中国电机工程学报》 * |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106019155A (en) * | 2016-07-08 | 2016-10-12 | 清华大学 | Phase comparison type differential protection method and system based on generator branch current |
| CN106019155B (en) * | 2016-07-08 | 2019-02-05 | 清华大学 | Phase comparison expression differential protecting method and system based on generator branch current |
| CN107102192A (en) * | 2017-04-28 | 2017-08-29 | 许继集团有限公司 | A kind of full phase asynchronous oscillation method of discrimination and device |
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| Publication number | Publication date |
|---|---|
| CN104934930B (en) | 2018-05-29 |
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