CN104934930B - Unbalanced fault differential protection accelerated method in a kind of vibration - Google Patents
Unbalanced fault differential protection accelerated method in a kind of vibration Download PDFInfo
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Abstract
The present invention relates to the guard methods in power transmission and transformation field, and in particular to unbalanced fault differential protection accelerated method in a kind of vibration.This method comprises the following steps：（1）When differential protection starts, discriminating element is put into, determines the negative-sequence current of differential protection branch；（2）The branch of negative-sequence current amplitude maximum is equivalent to virtual branch K；（3）It will sum except the negative-sequence current of other branches of negative-sequence current amplitude maximum branch, virtual branch T should be equivalent to negative-sequence current branch；（4）Virtual two branches K and T negative-sequence current directional element failure judgement point position is put into, and according to position of failure point to determine whether Blocking Differential Protection.Can calculating quickly be acquired to differential each branch negative-sequence current, can effectively identify whether trouble point is located in differential protection area, accelerated differential protection action if necessary, favorable influence is brought to power transmission and transformation system.The present invention differentiates accurate, it is easy to accomplish, possess good prospect of the application.
Description
Technical field
The present invention relates to the guard methods in power transmission and transformation field, and in particular to unbalanced fault differential protection adds in a kind of vibration
Fast method.
Background technology
Differential protection is a kind of important short-circuit protection, and structure, operation principle are simple, influenced by load current it is smaller,
Therefore it is widely used in electric system.Differential protection generally flows the ratiometric compared with stalling current using difference at present
Moving curve is for differentiating internal fault external fault, and when system oscillation, stalling current becomes with cycle of oscillation sexual intercourse, and alternation amplitude is very big.
Unbalanced fault occurs for period, and differential protection is easily unable to quick acting by the locking of ratio brake curve.Make system under serious conditions
Situations such as vibration deteriorates or even causes system sectionalizing, very big harm is brought to Operation of Electric Systems.How in reliable premise
Under, the actuation time for accelerating differential protection is always the focus studied.Utilize trouble point periphery negative-sequence current direction itself letter
The characteristics of single, with reference to each associated branch negative-sequence current information of differential protection, the variation of total calculation analysis grounding point position is with bearing
The relation of sequence electric current sequence net changes in distribution obtains a kind of method that can speed up differential protection action, is that power system security is steady
Fixed operation brings favorable influence.
The content of the invention
In view of the deficiencies of the prior art, the object of the present invention is to provide unbalanced fault differential protections in a kind of vibration to accelerate
Method when an error occurs by calculating the size of each branch negative-sequence current, sorts n branches is equivalent into virtual two branch.So
Direction, the amplitude failure judgement point position of virtual two branch negative-sequence current are calculated afterwards.Differential protection member is accelerated according to analysis result
Part cuts off rapidly failure, and favorable influence is brought to power transmission and transformation system.
The purpose of the present invention is what is realized using following technical proposals：
The present invention provides unbalanced fault differential protection accelerated method in a kind of vibration, it is improved in that the side
Method comprises the following steps：
（1）When differential protection starts, discriminating element is put into, determines the negative-sequence current of differential protection branch；
（2）The branch of negative-sequence current amplitude maximum is equivalent to virtual branch K；
（3）It will sum except the negative-sequence current of other branches of negative-sequence current amplitude maximum branch, it should be with negative-sequence current branch
It is equivalent to virtual branch T；
（4）Virtual two branches K and T negative-sequence current directional element failure judgement point position is put into, and according to position of failure point
To determine whether Blocking Differential Protection.
Further, the step（1）In, determine the negative-sequence current I of n branch of differential protectioni, i=1,2 ... n.
Further, the step（2）In, compare the amplitude of n branch negative-sequence current, choose negative-sequence current amplitude maximum
Imx=max { I1,I2,...In, work as Imx＞ IywWhen, it is equivalent virtual branch K, the I by negative-sequence current amplitude maximum branchyw
For current threshold；The negative-sequence current of the virtual branch K is denoted as Imx。
Further, the step（3）In, calculate the other branch negative phase-sequences and electricity except negative-sequence current amplitude maximum branch
Stream, other branch negative phase-sequences and current branch are equivalent to virtual branch T, the negative-sequence current of the virtual branch T are denoted as Iot,Work as Iot＞ IywWhen, calculate negative-sequence current directional elementWherein：WithIt is band respectively
The negative-sequence current vector of the virtual branch T of negative-sequence current vector sum of directive virtual branch K.
Further, the step（4）In, including following situations：
1. when the negative-sequence current of virtual two branches K and T is negative directions, and | Imx|≈|Iot|, meetThen failure judgement point is outside differential protection area, i.e. unbalanced fault outside generating region,
Blocking Differential Protection acts at this time；The θ1For the reversed threshold value of directional element；
2. the negative-sequence current angle homologous ray negative sequence impedance angle of virtual two branches K and T is related, when each branch negative sequence impedance angle
When equal, the negative-sequence current of virtual two branches K and T are equidirectional, and meetThen failure judgement point
For in differential protection area, i.e. unbalanced fault in generating region accelerates differential protection action at this time；The θ2It is positive for directional element
Threshold value.
Compared with the prior art, the advantageous effect that reaches of the present invention is：
1st, unbalanced fault differential protection accelerated method in vibration provided by the invention can quickly bear differential each branch
Sequence electric current is acquired calculating, can effectively identify whether trouble point is located in differential protection area, accelerates differential protection if necessary
Action, favorable influence is brought to power transmission and transformation system.
2nd, the present invention chooses I using the amplitude of more each branch negative-sequence currentmx=max { I1,I2,...In, and Imx＞
Iyw, it is equivalent branch K to remember the branch.Calculate adjacent legs negative phase-sequence and electric currentAnd work as Iot＞ IywWhen calculate negative phase-sequence
Current directionDiscriminating direction position of failure point accordingly, it is simple, accurate, quick.
3rd, the present invention calculates influence of the negative-sequence current directional element from system oscillation, with routine ratio brake curve phase
Than differential protection responsiveness in vibration can be greatly improved.
4th, computation model of the present invention（）Design is simple, and fault identification is realized fast, can be widely applied to
In all kinds of differential protections such as transformer differential protection, bus differential protecting.
5th, the present invention differentiates accurate, it is easy to accomplish, possess good prospect of the application.
6th, vibrate in troubles inside the sample space, conventional ratio brake differential protection actuation time substantially with delay, action delay with
Cycle of oscillation is related, and nearly half of cycle of oscillation duration is even up in electric current wave crest failure, action delay under extreme case.It is conventional
Ratio brake differential protection is compared with negative-sequence current directional element acting characteristic, sample frequency 4000（Point/second）, conventional ratio
150ms is acted after earth fault in area for retaining differential protection（Corresponding 600 points of sampled point number）, and negative-sequence current directional element
Occur to open in 10ms in failure.
Description of the drawings
Fig. 1 is the flow chart of unbalanced fault differential protection accelerated method in vibration provided by the invention；
Fig. 2 is that earth fault routine ratio brake is acted with negative-sequence current directional element in area in vibration provided by the invention
Characteristic comparison chart；
Fig. 3 is that three-phase fault routine ratio brake is acted with negative-sequence current directional element in area in vibration provided by the invention
Characteristic comparison chart.
Specific embodiment
The specific embodiment of the present invention is described in further detail below in conjunction with the accompanying drawings.
When unbalanced fault occurs for power grid, negative phase-sequence sequence diagrams show with the variation of earth point position and change.According to
Negative phase-sequence power grid, negative-sequence current direction is to flow to system from trouble point when failure occurs.When troubles inside the sample space, each branch negative-sequence current
It is flowed outwardly centered on troubles inside the sample space point, each branch negative-sequence current direction approaches, and specific angular difference is the same as branch roads system negative sequence impedance
Angle is related.When external area error, negative-sequence current is flowed outwardly centered on external area error point, virtual two branches negative-sequence current direction
On the contrary.Position of failure point can determine whether according to negative-sequence current direction, when confirming that position of failure point is in differential protection area, accelerate differential
Protection act cuts off failure, safeguards power system stability.
The present invention provides unbalanced fault differential protection accelerated method in a kind of vibration, flow chart as shown in Figure 1, including
Following step：
（1）When differential protection starts, discriminating element is put into, determines the negative-sequence current I of n branch of differential protectioni, i=1,
2,...n。
（2）Compare the amplitude of n branch negative-sequence current, choose negative-sequence current amplitude maximum Imx=max { I1,I2,...In,
Work as Imx＞ IywWhen, it is equivalent virtual branch K, the I by negative-sequence current amplitude maximum branchywFor current threshold；It will be described virtual
The negative-sequence current of branch K is denoted as Imx。
（3）Calculate the other branch negative phase-sequences and electric current except negative-sequence current amplitude maximum branch, other branch negative phase-sequences and electric current
Branch is equivalent to virtual branch T, and the negative-sequence current of the virtual branch T is denoted as Iot,Work as Iot＞ IywWhen, meter
Calculate negative-sequence current directional elementWherein：WithIt is the negative phase-sequence electricity with directive virtual branch K respectively
The negative-sequence current vector of flow vector and virtual branch T.
（4）Virtual two branches K and T negative-sequence current directional element failure judgement point position is put into, and according to position of failure point
To determine whether Blocking Differential Protection, including following situations：
1. when the negative-sequence current of virtual two branches K and T is negative directions, and | Imx|≈|Iot|, meetThen failure judgement point is outside differential protection area, i.e. unbalanced fault outside generating region,
Blocking Differential Protection acts at this time；The θ1For the reversed threshold value of directional element；
2. the negative-sequence current angle homologous ray negative sequence impedance angle of virtual two branches K and T is related, when each branch negative sequence impedance angle
When equal, the negative-sequence current of virtual two branches K and T are equidirectional, and meetThen failure judgement
Point is in differential protection area, i.e. unbalanced fault in generating region can accelerate differential protection to act at this time；The θ2For directional element
Positive threshold.
Current threshold I thereinyw, the reversed threshold θ of directional element1With directional element positive threshold θ2It can be manually set.
Embodiment
Troubles inside the sample space in vibration, conventional ratio brake differential protection actuation time, action delay was with shaking substantially with delay
It is related to swing the cycle, and nearly half of cycle of oscillation duration is even up in electric current wave crest failure, action delay under extreme case.Fig. 2 institutes
Show that conventional ratio brake differential protection is compared with negative-sequence current directional element acting characteristic, sample frequency 4000（Point/second）, often
Advising ratio brake differential protection, 150ms is acted after earth fault in area（Corresponding 600 points of sampled point number）, and negative-sequence current side
Occur to open in 10ms in failure to element.
Conventional ratio brake differential protection is compared with negative-sequence current directional element acting characteristic shown in Fig. 3, and sample frequency is
4000（Point/second）, 170ms is acted conventional ratio brake differential protection after three-phase fault in area（Corresponding sampled point number 680
Point）, and non-synchronous failure phase in initial 20ms occurs in failure and opens for negative-sequence current directional element.
Finally it should be noted that：The above embodiments are merely illustrative of the technical scheme of the present invention and are not intended to be limiting thereof, to the greatest extent
Pipe is described in detail the present invention with reference to above-described embodiment, those of ordinary skills in the art should understand that：Still
The specific embodiment of the present invention can be modified or replaced equivalently, and without departing from any of spirit and scope of the invention
Modification or equivalent substitution, should be covered by the scope of the claims of the present invention.
Claims (1)
1. unbalanced fault differential protection accelerated method in a kind of vibration, which is characterized in that the described method includes following step：
(1) when differential protection starts, discriminating element is put into, determines the negative-sequence current I of n branch of differential protectioni, i=1,2,
...n；
(2) branch of negative-sequence current amplitude maximum is equivalent to virtual branch K；
(3) will sum except the negative-sequence current of other branches of negative-sequence current amplitude maximum branch, it should be equivalent with negative-sequence current branch
For virtual branch T；
(4) virtual two branches K and T negative-sequence current directional element failure judgement point position is put into, and is sentenced according to position of failure point
It is disconnected whether Blocking Differential Protection；
In the step (2), compare the amplitude of n branch negative-sequence current, choose negative-sequence current amplitude maximum Imx=max { I1,
I2,...In, work as Imx＞ IywWhen, it is equivalent virtual branch K, the I by negative-sequence current amplitude maximum branchywFor current threshold；
The negative-sequence current of the virtual branch K is denoted as Imx；
In the step (3), other branch negative phase-sequences and electric current except negative-sequence current amplitude maximum branch, other branch negative phase-sequences are calculated
Virtual branch T is equivalent to current branch, the negative-sequence current of the virtual branch T is denoted as Iot,Work as Iot＞
IywWhen, calculate negative-sequence current directional elementWherein：WithIt is with directive virtual branch K respectively
The negative-sequence current vector of the virtual branch T of negative-sequence current vector sum；
In the step (4), including following situations：
1. when the negative-sequence current of virtual two branches K and T is negative directions, and | Imx|≈|Iot|, meetThen failure judgement point is outside differential protection area, i.e. unbalanced fault outside generating region,
Blocking Differential Protection acts at this time；The θ1For the reversed threshold value of directional element；
2. the negative-sequence current angle homologous ray negative sequence impedance angle of virtual two branches K and T is related, when each branch negative sequence impedance angle is equal
When, the negative-sequence current of virtual two branches K and T are equidirectional, and meetThen failure judgement point is poor
It moves in protection zone, i.e. unbalanced fault in generating region, accelerates differential protection action at this time；The θ2For directional element forward direction threshold
Value.
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