CN112946415A - Power distribution network fault rapid direction identification method based on current phase after fault - Google Patents

Power distribution network fault rapid direction identification method based on current phase after fault Download PDF

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CN112946415A
CN112946415A CN202011617003.1A CN202011617003A CN112946415A CN 112946415 A CN112946415 A CN 112946415A CN 202011617003 A CN202011617003 A CN 202011617003A CN 112946415 A CN112946415 A CN 112946415A
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fault
current
phase
distribution network
power distribution
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赵建光
范建伦
康立欣
王兴根
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Huanyu Group Nanjing Co ltd
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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
    • 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
    • G01R31/088—Aspects of digital computing

Abstract

The invention discloses a method for rapidly identifying the fault direction of a power distribution network containing a distributed power supply based on a current phase after the fault, which comprises the following steps: 1) defining a protection direction, 2) analyzing a forward fault and a reverse fault, 3) calculating a fault current phasor and a reference phasor by using the forward fault or the reverse fault, setting a fault direction criterion, 4) calculating the reference phasor
Figure DDA0002875148770000011
Phase of (2) and fault current phasor
Figure DDA0002875148770000012
The phase difference of (1) judging the final fault direction, and 5) when the fault is an asymmetric fault, separating the positive sequence component in the fault current through discrete Fourier transform to identify the fault direction, compared with the traditional three-section type directional current protection scheme, the improved method avoids using a large number of directional elements, only needs to acquire the current signal after the fault, and greatly improves the fault directionThe economical efficiency and the reliability of fault identification of the power distribution network with the distributed power supply are improved.

Description

Power distribution network fault rapid direction identification method based on current phase after fault
Technical Field
The invention relates to a method for rapidly identifying the fault direction of a power distribution network containing a distributed power supply based on a current phase after the fault, and belongs to the technical field of fault location of sections of the power distribution network.
Background
In recent years, a large number of distributed power supplies are connected to a power distribution network, so that a traditional radial power distribution network is changed into a multi-terminal power supply network, load flow calculation, protection and the like in the traditional power distribution network are changed due to the connection of the distributed power supplies, and the traditional three-section type current protection scheme cannot meet the operation requirement of the traditional power distribution network. Therefore, the method has high research value for ensuring the safe operation of the system, improving the reliability of the operation of the system and reducing the influence of the interference caused by the access of the distributed power supply on the stability of the system.
According to the regulation of IEEE std.1547, after the distributed power supply is connected to the power distribution network, when a fault occurs, the distributed power supply must be cut off, and the purpose is to reduce the influence of the distributed power supply connection on the accuracy of fault information acquisition of the power distribution network automation system. Because the distributed power supply is connected into the power distribution network, the traditional power distribution network structure is changed into a multi-terminal power supply network with interconnected power supplies and users, and the fault direction identification method of the traditional power distribution network is applied to a novel structure, so that the accuracy is reduced, even the fault or the non-action can occur due to the invalid protection method, the unstable operation of the power distribution network is caused, but the utilization rate of the distributed power supply can be greatly reduced by cutting off the distributed power supply to process the generated fault. Therefore, in order to improve the utilization rate of the distributed power supply after being connected into the power distribution network and improve the efficiency of fault direction identification, the invention provides a method for quickly identifying the fault direction of the power distribution network containing the distributed power supply based on the current phase after the fault.
Disclosure of Invention
The invention provides a method for rapidly identifying the direction of a fault of a power distribution network containing a distributed power supply based on a current phase after the fault, which is used for overcoming the defect that a large number of direction elements are used in the traditional three-section type direction current protection scheme and improving the accuracy and efficiency of fault location of the power distribution network containing the distributed power supply.
In order to solve the technical problems, the invention provides the following technical scheme:
the invention discloses a method for rapidly identifying the fault direction of a power distribution network containing a distributed power supply based on a current phase after the fault, which comprises the following steps:
1) in fig. 1, the positive flow of the power flow means that the power direction coincides with the prescribed direction of the protection device. In the case of forward power flow, the voltage at the a node is first defined as vA(t)＝|VA|sin(ωt+α)，VAAnd alpha are the modulus and phase of the voltage at node a, respectively. Voltage of node C is vC(t)＝|VC|sin(ωt+β)，VCAnd beta are the modulus and phase, respectively, of the voltage at node C, and when a fault K1 occurs on line BC, the line impedance from node A to point K1 is | ZAk1|∠α1When a fault K2 occurs on line AB, the line impedance from node C to K2 is | ZCk2|∠α2。
2) Analyzing a forward fault: referring to fig. 1, a three-phase earth fault and a fault current occur at the point K1 on the BC line
Figure BDA0002875148750000021
The calculation is as follows:
Figure BDA0002875148750000022
to pair
Figure BDA0002875148750000023
Calculating a positive derivative:
Figure BDA0002875148750000024
to pair
Figure BDA0002875148750000025
And (3) obtaining a negative derivative:
Figure BDA0002875148750000026
establishing reference phasors
Figure BDA0002875148750000027
And detecting the fault direction, wherein the formula is as follows:
Figure BDA0002875148750000028
3) analyzing reverse faults: for example, a three-phase earth fault and a fault current occur at the point K2 on the AB line in the attached figure 1
Figure BDA0002875148750000031
The calculation is as follows:
Figure BDA0002875148750000032
to pair
Figure BDA0002875148750000033
Calculating positive derivative
Figure BDA0002875148750000034
To pair
Figure BDA0002875148750000035
Negative derivative of
Figure BDA0002875148750000036
Establishing reference vectors
Figure BDA0002875148750000037
And detecting the fault direction, wherein the formula is as follows:
Figure BDA0002875148750000038
4) calculating fault current phasor by using forward or reverse faultAnd referring to the phasor, setting a fault direction criterion. The direction of the fault can be determined by establishing a new phasor
Figure BDA0002875148750000039
By definition, the formula is as follows:
Figure BDA00028751487500000310
Figure BDA00028751487500000311
5) figures 2 and 3 show vector diagrams of the respective currents and their associated phase parameters when power is flowing in the forward direction, in a forward fault and in a reverse fault, respectively.
6) The lambda for finally judging the fault direction in the method is determined by referring to phasor
Figure BDA00028751487500000312
Phase of (2) and fault current phasor
Figure BDA00028751487500000313
The phase difference of (a) is calculated, so that the interval form generalization of the Λ phase is not needed.
7) When the fault that occurs is an asymmetric short-circuit fault, it is necessary to extract a positive sequence component in the fault current because the positive sequence component exists among the symmetric fault and the asymmetric fault, and the fault direction is identified by the positive sequence component extracted from the fault current.
Taking the phase A as an example, under the condition of forward power flow, when asymmetric faults occur, the phase A fault short-circuit current detected by the upstream protection of a fault feeder line is separated into a positive sequence component through a discrete Fourier transform template
Figure BDA0002875148750000041
The positive derivative is:
Figure BDA0002875148750000042
the negative derivative is:
Figure BDA0002875148750000043
establishing a reference phasor as follows:
Figure BDA0002875148750000044
establishing a new phasor
Figure BDA0002875148750000045
When available line has forward fault
Figure BDA0002875148750000046
When reverse fault occurs in the line
Figure BDA0002875148750000047
In the same way, under the condition of reverse power flow, the fault direction can still be accurately identified through operations such as positive sequence fault components and the like, so that all types of short-circuit faults can be judged by using the fault direction quick identification algorithm provided by the invention.
8) The fault direction rapid identification algorithm provided by the invention only needs to collect current signals at the protection installation position, does not need to collect other information such as voltage signals and current signals before fault, does not need to transmit a protection judgment result to the other end of a line, and judges the fault by matching the results at the two ends. Disturbances or faults in the power system are triggered by the triggering element of the protection device. The starting element operating principle currently generally uses a starting method based on instantaneous value variables of phase current differences. A flow chart of the directional current protection procedure is shown in fig. 4.
The invention has the following beneficial effects: the fault direction is identified by only using the current signal after the fault through the phase comparison of the current, and the voltage signal and the current signal before the fault do not need to be collected. Compared with the traditional direction protection method based on voltage and current, the method has better economical efficiency and reliability. The method is not influenced by factors such as the current flow direction, the grounding resistance, the fault type, the capacity ratio and the position of the distributed power supply, harmonic waves and the like, and can reliably identify the fault direction in the full-length range of the line.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:
fig. 1 is a post-fault current phase analysis diagram of the present invention.
Fig. 2 is a forward tidal phase vector diagram.
Fig. 3 is a reverse tidal phase phasor diagram.
Fig. 4 is a flow chart of the fault direction identification algorithm.
Detailed Description
The preferred embodiments of the present invention will be described in conjunction with the accompanying drawings, and it will be understood that they are described herein for the purpose of illustration and explanation and not limitation.
A method for rapidly identifying the fault direction of a power distribution network containing a distributed power supply based on a current phase after the fault comprises the following steps:
step 1) in fig. 1, the forward flow of the power flow means that the power direction coincides with the direction specified by the protection device. In the case of forward power flow, the voltage at the a node is first defined as vA(t)＝|VA|sin(ωt+α)，VAAnd alpha are the modulus and phase of the voltage at node a, respectively. Voltage of node C is vC(t)＝|VC|sin(ωt+β)，VCAnd beta are the modulus and phase, respectively, of the voltage at node C, and when a fault K1 occurs on line BC, the line impedance from node A to point K1 is | ZAk1|∠α1When a fault K2 occurs on line AB, the line impedance from node C to K2 is | ZCk2|∠α2。
Step (ii) of2) Analyzing a forward fault: as shown in the figure, a three-phase earth fault and a fault current occur at the K1 point on the BC line
Figure BDA0002875148750000051
The calculation is as follows:
Figure BDA0002875148750000052
to pair
Figure BDA0002875148750000053
Calculating a positive derivative:
Figure BDA0002875148750000061
to pair
Figure BDA0002875148750000062
And (3) obtaining a negative derivative:
Figure BDA0002875148750000063
establishing reference phasors
Figure BDA0002875148750000064
And detecting the fault direction, wherein the formula is as follows:
Figure BDA0002875148750000065
step 3) analyzing reverse faults: for example, three-phase earth fault and fault current occur at point K2 on AB line in the figure
Figure BDA0002875148750000066
The calculation is as follows:
Figure BDA0002875148750000067
to pair
Figure BDA0002875148750000068
Calculating positive derivative
Figure BDA0002875148750000069
To pair
Figure BDA00028751487500000610
Negative derivative of
Figure BDA00028751487500000611
Establishing reference vectors
Figure BDA00028751487500000612
And detecting the fault direction, wherein the formula is as follows:
Figure BDA00028751487500000613
and 4) calculating a fault current phasor and a reference phasor by using the forward fault or the reverse fault, and setting a fault direction criterion. The direction of the fault can be determined by establishing a new phasor
Figure BDA00028751487500000614
By definition, the formula is as follows:
Figure BDA0002875148750000071
Figure BDA0002875148750000072
step 5) fig. 2 and fig. 3 show vector diagrams of the respective currents and their associated phase parameters, respectively, for a forward fault and a reverse fault when power is flowing in the forward direction.
Step 6) finally judging the lambda of the fault direction in the method through the reference phasor
Figure BDA0002875148750000073
Phase of (2) and fault current phasor
Figure BDA0002875148750000074
The phase difference of (a) is calculated, so that the interval form generalization of the Λ phase is not needed.
And 7) when the fault is an asymmetric short-circuit fault, extracting a positive sequence component from the fault current, wherein the positive sequence component exists in the symmetric fault and the asymmetric fault, and identifying the fault direction through the positive sequence component extracted from the fault current.
Taking the phase A as an example, under the condition of forward power flow, when asymmetric faults occur, the phase A fault short-circuit current detected by the upstream protection of a fault feeder line is separated into a positive sequence component through a discrete Fourier transform template
Figure BDA0002875148750000075
The positive derivative is:
Figure BDA0002875148750000076
the negative derivative is:
Figure BDA0002875148750000077
establishing a reference phasor as follows:
Figure BDA0002875148750000078
establishing a new phasor
Figure BDA0002875148750000079
When available line has forward fault
Figure BDA00028751487500000710
When reverse fault occurs in the line
Figure BDA00028751487500000711
In the same way, under the condition of reverse power flow, the fault direction can still be accurately identified through operations such as positive sequence fault components and the like, so that all types of short-circuit faults can be judged by using the fault direction quick identification algorithm provided by the invention.
Finally, it should be noted that: although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that changes may be made in the embodiments and/or equivalents thereof without departing from the spirit and scope of the invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (5)

1. A power distribution network fault rapid direction identification method based on a current phase after a fault is characterized by comprising the following steps:
1) the positive flow of the tidal current means that the power direction is consistent with the specified direction of the protection device; in the case of forward power flow, the voltage at the a node is first defined as vA(t)＝|VA|sin(ωt+α)，VAAnd alpha is the modulus and phase of the A node voltage respectively; voltage of node C is vC(t)＝|VC|sin(ωt+β)，VCAnd beta are the modulus and phase, respectively, of the voltage at node C, and when a fault K1 occurs on line BC, the line impedance from node A to point K1 is | ZAk1|∠α1When a fault K2 occurs on line AB, the line impedance from node C to K2 is | ZCk2|∠α2；
2) Analyzing the forward fault and the reverse fault;
3) and calculating the fault current phasor and the reference phasor by using the forward fault or the reverse fault, and setting a fault direction criterion.
2. A power distribution network fault fast direction identification method based on post-fault current phase as claimed in claim 1 further comprising step 4): when the fault is an asymmetric fault, a positive sequence component in the fault current is separated through discrete Fourier transform to identify the fault direction.
3. The method for rapidly identifying the fault direction of the power distribution network with the distributed power sources based on the current phase after the fault according to claim 1, wherein the analysis of the forward fault and the reverse fault in the step 2) comprises the following steps:
21) and a three-phase earth fault and a fault current occur at the point K1 on the BC line
Figure RE-FDA0003058849450000011
The calculation is as follows:
Figure RE-FDA0003058849450000012
22) to, for
Figure RE-FDA0003058849450000013
Calculating a positive derivative:
Figure RE-FDA0003058849450000014
to pair
Figure RE-FDA0003058849450000021
And (3) obtaining a negative derivative:
Figure RE-FDA0003058849450000022
23) establishing a reference phasor
Figure RE-FDA0003058849450000023
And detecting the fault direction, wherein the formula is as follows:
Figure RE-FDA0003058849450000024
24) and a three-phase earth fault and a fault current occur at the K2 point on the AB line
Figure RE-FDA0003058849450000025
The calculation is as follows:
Figure RE-FDA0003058849450000026
25) to, for
Figure RE-FDA0003058849450000027
Calculating positive derivative
Figure RE-FDA0003058849450000028
To pair
Figure RE-FDA0003058849450000029
Negative derivative of
Figure RE-FDA00030588494500000210
26) Establishing a reference vector
Figure RE-FDA00030588494500000211
And detecting the fault direction, wherein the formula is as follows:
Figure RE-FDA00030588494500000212
4. a method for fast direction identification of power distribution network faults based on post-fault current phase according to claim 1, wherein in step 3), the method for setting the fault direction criterion is as follows:
31) the direction of the fault can be determined by establishing a new phasor
Figure RE-FDA00030588494500000213
By definition, the formula is as follows:
Figure RE-FDA00030588494500000214
Figure RE-FDA0003058849450000031
5. the method for rapidly identifying the fault direction of the power distribution network based on the current phase after the fault according to claim 2, wherein in the step 4), the specific steps of extracting the positive sequence component in the fault current are as follows:
41) under the condition of forward power flow, when asymmetric faults occur, the A-phase fault short-circuit current detected by the upstream protection of the fault feeder line is separated into a positive sequence component through a discrete Fourier transform template
Figure RE-FDA0003058849450000032
The positive derivative is:
Figure RE-FDA0003058849450000033
the negative derivative is:
Figure RE-FDA0003058849450000034
42) establishing a reference phasor as follows:
Figure RE-FDA0003058849450000035
43) establishing a new phasor
Figure RE-FDA0003058849450000036
When available line has forward fault
Figure RE-FDA0003058849450000037
When reverse fault occurs in the line
Figure RE-FDA0003058849450000038
CN202011617003.1A 2020-12-31 2020-12-31 Power distribution network fault rapid direction identification method based on current phase after fault Pending CN112946415A (en)

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Application publication date: 20210611