CN112526281A

CN112526281A - Double-end distance measurement method for T-connection line fault

Info

Publication number: CN112526281A
Application number: CN201910887993.1A
Authority: CN
Inventors: 余洪; 吴通华; 王小红; 郑玉平; 姚刚; 纪浩然; 梁臣; 戴魏; 孙良凯; 杨平怡; 洪丰
Original assignee: NARI Group Corp; Nari Technology Co Ltd; NARI Nanjing Control System Co Ltd
Current assignee: NARI Group Corp; Nari Technology Co Ltd; NARI Nanjing Control System Co Ltd
Priority date: 2019-09-19
Filing date: 2019-09-19
Publication date: 2021-03-19
Anticipated expiration: 2039-09-19
Also published as: CN112526281B

Abstract

The invention discloses a T-connection line fault double-end distance measurement method, which improves the fault branch line region selection capacity through a composite sequence component compensation voltage algorithm, and compared with the prior art, the region selection accuracy is improved by more than one time on average; when the elected area result is effective, a double-end distance measurement algorithm based on the virtual T-terminal voltage is preferentially used, accurate distance measurement can be carried out under various fault conditions, the distance measurement method is not influenced by a system operation mode, accurate distance measurement can be carried out under high-resistance faults, and compared with the prior art, the distance measurement error is lower than 2.5% on average. The method is suitable for occasions where relay protection of the power system can only carry out impedance distance measurement by using single-ended fault information, and can effectively solve the problem that the existing T-junction circuit is inaccurate in fault distance measurement.

Description

Double-end distance measurement method for T-connection line fault

Technical Field

The invention belongs to the field of relay protection of a power system, relates to a relay protection line ranging optimization algorithm, and particularly relates to a T-connection line fault double-end ranging method.

Background

At present, the fault location algorithm applied to the power transmission line mainly comprises: single-ended ranging algorithms and double-ended ranging algorithms. The traditional double-end ranging algorithm is only suitable for a double-end system, and for a T-connection line (a three-end system), the traditional double-end ranging algorithm principle is not suitable due to the existence of a shunt branch; for a single-end fault location algorithm, general metallic faults can be accurately located only by a line at one end, and fault location results are inaccurate due to the existence of shunt branches at the other two ends. For the T-connection line fault location algorithm, some traveling wave methods and wave impedance methods (wang, linson, cong jun build, traveling wave algorithm for T-connection transmission line fault location, electric automation, 2011, 33, 03) (guo anming, handsfree, wang forever flood, etc., transmission line traveling wave three-terminal location algorithm based on complex wavelet, protection and control of electric power system, 2012, 40, 07), which are currently researched, have large calculation amount or complex principle, and difficult engineering. The patent provides an easy-to-engineer distance measurement method suitable for T lines with voltage levels of 110kV and below.

In the prior art, yao liang, chenfu feng and chenqi propose a comprehensive fault location solution applicable to a three-terminal power transmission line (a self-adaptive fault location method applied to a T-junction line, protection and control of a power system, 2012, 40 (3): 26-30). When the circuit is in a three-end operation mode, the fault branch circuit is firstly identified, and the positive sequence voltage of a point T is respectively calculated along the lines of the MT branch circuit, the NT branch circuit and the PT branch circuit

Wherein:

for positive sequence voltage current on each side, Z_mt、Z_nt、Z_ptIs the positive sequence impedance value of each side branch.

The absolute value of the subtraction of every two positive sequence voltage quantities of the three T joints is shown as the voltage difference obtained by:

if MIN (Δ U)_mnt,ΔU_mpt,ΔU_npt)＝ΔU_mntIf the branch PT is a fault branch, the current injected into the fault branch at the point T is

If MIN (Δ U)_mnt,ΔU_mpt,ΔU_npt)＝ΔU_mptIf the branch NT is a fault branch, the current injected into the fault branch at the point T is

If MIN (Δ U)_mnt,ΔU_mpt,ΔU_npt)＝ΔU_nptIf the branch MT is a fault branch, the current injected into the fault branch at the point T is

If Δ U_mnt≈ΔU_mpt≈ΔU_nptIf yes, the fault is judged to be a T point fault.

The traditional double-end ranging algorithm is only suitable for a double-end system, and for a T-connection line (a three-end system), the principle of the double-end ranging algorithm is not suitable; and for general metallic faults, a single-end fault location algorithm only has one end of a line to accurately locate the fault, and the other two ends of the line have inaccurate fault location results due to the existence of a shunt branch, and the three ends of the line cannot accurately locate the fault or even cannot locate the fault when the high-resistance grounding fault occurs. According to relevant statistical data, the single-phase grounding fault accounts for the highest proportion of more than 85% in the grid system faults (see '2018 national grid company relay protection equipment analysis and evaluation report'), and the high-resistance grounding fault proportion is also high. Therefore, both the traditional single-ended ranging algorithm and the traditional double-ended ranging algorithm are not suitable for the existing T-line fault ranging.

For the T-connection line fault location algorithm, some traveling wave methods and wave impedance methods researched at present have large calculation amount of general algorithms or complex principle and are difficult to engineer, and the method for identifying a fault branch by using a T-point compensation voltage and then determining a fault point by using a single-end fault location algorithm, which is proposed by YaoLiang and the like, has the advantages of simple principle, small calculation amount and suitability for engineering, but the location result of the method is greatly influenced by transition resistance, only a positive sequence component is used in a fault location area, and the error of the location area is large, so that the fault branch is not beneficial to be confirmed.

Disclosure of Invention

The invention aims to solve the problems in the prior art and provides a T-connection line fault double-end ranging method which is easy to realize in the conventional line protection device, improves the fault branch line selection capacity through a composite sequence component compensation voltage algorithm, preferentially uses a double-end ranging algorithm based on virtual T-terminal voltage when a selection result is effective, and can accurately range under various fault conditions.

In order to achieve the purpose, the invention adopts the technical scheme that:

a double-end distance measurement method for a T-connection line fault comprises the following steps:

carrying out fault branch selection;

when the elected area result is effective, calculating a virtual T-terminal voltage based on the non-fault branch;

and based on the virtual T-terminal voltage obtained by calculation, when the fault occurs symmetrically, double-end distance measurement of the fault is carried out by using a double-end distance measurement algorithm of a positive sequence quantity.

Preferably, the fault branch selection is performed through a composite sequence component compensation voltage algorithm.

Preferably, when the electoral area result is valid, the non-fault branch with the shorter line is selected to calculate the virtual T-terminal voltage.

Preferably, when the selection result is invalid, double-end ranging is respectively carried out on the three branches.

Preferably, in the double-end ranging results of the three branches, the branch with the smallest per unit value and greater than 0 and less than 1.00 is a faulty branch.

Preferably, when the asymmetric fault occurs, double-end fault location is carried out by using a double-end fault location algorithm of a negative sequence quantity.

Compared with the prior art, the invention has the beneficial effects that:

(1) according to the invention, the fault branch region selection capability is improved through a composite sequence component compensation voltage algorithm (the composite sequence component is a positive sequence component, a negative sequence component and a zero sequence component which comprehensively use a fault state), and compared with the prior art, the region selection accuracy is averagely improved by more than one time; when the elected area result is effective, a double-end distance measurement algorithm based on the virtual T-terminal voltage is preferentially used, accurate distance measurement can be carried out under various fault conditions, the distance measurement method is not influenced by a system operation mode, accurate distance measurement can be carried out under high-resistance faults, and compared with the prior art, the distance measurement error is lower than 2.5% on average.

(2) The method is suitable for various operation modes of relay protection of the power system and occasions with over-resistance faults, and can effectively solve the problem that the existing T-junction circuit fault distance measurement is inaccurate.

Drawings

FIG. 1 is a schematic diagram of a T-lane partition according to an embodiment of the present invention;

FIG. 2 is a flow chart illustrating a fault double-ended ranging method according to an embodiment of the invention;

FIG. 3 is a schematic diagram of an RTDS system model according to an embodiment of the invention;

FIG. 4 is a schematic diagram of a virtual T-terminal compensation voltage according to an embodiment of the invention.

Detailed Description

The technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The invention provides a double-end distance measurement method for a T-connection line fault, which comprises the following steps: the first step is as follows: the fault branch area selection capacity is improved through a composite sequence component compensation voltage algorithm; the second step is that: when the elected area result is valid, calculating the virtual T-terminal voltage through the non-fault branch, performing fault location by using double-terminal data of the fault branch, and when the elected area result is invalid, performing double-terminal location by using the three branches respectively. Wherein the double-ended data of the faulty branch comprises: voltage and current analog quantities of a line at one end (corresponding to the M end, the N end and the P end) and a virtual T end.

The fault area selection is to determine which line range the fault point is in, as shown in fig. 1, a line M-T is an area 1, a line N-T is an area 2, and a line P-T is an area 3.

As shown in fig. 2, the method for selecting a fault area includes: using voltage analog quantities of M terminal, N terminal and P terminal respectively

Current analog quantity

And the sequence impedance Z of each branch_1mt、Z_0mt、Z_1nt、Z_0nt、Z_1pt、Z_0ptCalculating the compensation voltage of the T point

Finding out the compensation voltage difference of three-terminal T point by combining the phase selection result of the fault

Minimum value of when

Determining the fault branch as a P-T branch (zone 3) for the minimum value of the three; when in use

Determining the fault branch as an N-T (2 area) branch for the minimum value of the three; when in use

Determining the fault branch as an M-T (1 region) branch for the minimum value of the three; when in use

And the fault point is a point T. Wherein, the fault phase selection result correspondingly generates single-phase fault (AG \ BG \ CG), interphase fault (AB \ BC \ CA) or three-phase fault (ABC).

When a fault of the area 1 is detected, virtual T end voltage and current analog quantity are calculated through P end voltage, N end voltage and current analog quantity which are synchronized with M end data, the virtual T end voltage and the current analog quantity are calculated by preferentially adopting a branch circuit with a short circuit in the circuit N-T and the circuit P-T in consideration of the influence of capacitance and current, and the calculated virtual T end voltage and current analog quantity are synchronized with the M end voltage and current analog quantity on the basis of the voltage analog quantity and the current analog quantity which are synchronized at the M end, the N end and the P end. Double-end distance measurement can be completed by using the voltages of the T end and the M end and current analog quantity; and when the fault branch selection area is invalid, performing double-end distance measurement on the branches M-T, N-T, P-T respectively, determining the branch with the smallest distance measurement result per unit value, more than 0 and less than 1.00 as the fault branch, and uploading the distance measurement result of the branch.

As an embodiment, there is provided a T-junction line fault double-end ranging method, including:

(1) a typical RTDS simulation model is built, as shown in FIG. 3, with model parameters as shown in Table 1.

Item	Parameter(s)	Unit of
			Positive sequence resistor	0.147	Ω/km
Positive sequence inductive reactance	0.430	Ω/km
			Positive sequence parallel capacitive reactance	0.530	MΩ*km
Zero sequence resistance	0.500	Ω/km
			Zero sequence inductive reactance	1.200	Ω/km
Zero sequence parallel capacitive reactance	0.786	MΩ*km
			Line length MT (zone 1)	20	km
Line length NT (zone 2)	30	km
			Line length PT (zone 3)	40	km

TABLE 1

Wherein: simulating a fault point K1 at a position 50% away from the M side, wherein the theoretical T point distance measurement result is 20 × 0.5-10 kM; simulating a fault point K2 at a position 50% away from the N side, wherein the theoretical T point distance measurement result is 30 × 0.5-15 kM; the simulated fault point K3 has a fault 30% away from the P side, and the theoretical T point measurement result is 40 × 0.3 — 12 kM.

(2) Under two typical system operating modes: the three ends are all power systems; and the three terminals are a power supply and load hybrid system, and the traditional impedance distance measurement result is compared with the impedance distance measurement result of the embodiment, and the comparison result is shown in tables 2 and 3.

Three ends are power supply systems (big power side, small power side)

TABLE 2

② three-terminal power supply and load hybrid system

TABLE 3

Therefore, under two typical system operation modes (three terminals are both power supply systems or three terminals are power supply and load hybrid systems), the double-terminal ranging method based on the T-point virtual voltage and current analog quantity provided by the embodiment can accurately range under various fault conditions, and the traditional ranging method has large ranging error or even can not range when high-resistance faults occur (K1-A-50 omega, K1-A-100 omega, K1-AB-10 omega and the like).

As an embodiment, a T-line fault double-ended ranging method is provided. The method performs zoning as shown in fig. 1 and performs fault zoning as shown in fig. 2. When detecting that the 1 region has a fault, calculating virtual T-end voltage analog quantity through P-end and N-end voltage and current analog quantities synchronized with M-end data

Current analog quantity

And considering the influence of capacitance current, calculating the virtual T end voltage by adopting the voltage and current analog quantity of the shorter branch circuit in the two lines of the N-T line and the P-T line, and synchronizing the calculated virtual T end voltage and current analog quantity with the M end voltage and current analog quantity based on the voltage analog quantity and current analog quantity synchronized with the M end voltage and current analog quantity. Double-end ranging can be realized by using the voltages of the T end, the M end and the current analog quantity, and different double-end ranging algorithms are adopted according to different fault types: double-end ranging is performed on the negative sequence component for the asymmetric fault (formula 3), and double-end ranging is performed on the positive sequence component for the symmetric fault (formula 4); and when the fault branch selection area is invalid, performing double-end distance measurement on the branches M-T, N-T, P-T respectively, determining the branch with the smallest distance measurement result per unit value, more than 0 and less than 1.00 as the fault branch, and uploading the distance measurement result of the branch (formula 3 and formula 4).

Specifically, the double-ended ranging algorithm comprises:

when the line length L_NT＜L_PTThe method comprises the following steps:

when the line length L_NT＞L_PTThe method comprises the following steps:

wherein:

virtualizing three-phase voltage for a T point on a line;

measuring three-phase voltages for a P end and an N end;

virtual A current, B current, C current and zero sequence current of a T point on a line are obtained;

measuring current A, current B, current C and zero sequence current for a P end and an N end; z_1ntAnd Z_1ptPositive sequence impedance, Z, for lines N-T and P-T_0ntAnd Z_0ptZero sequence impedance for line N-T and line P-T.

Taking the M-T branch as an example of a fault, the double-end ranging method adopted in this embodiment is as follows:

wherein:

the negative sequence voltages of a point T and a point M on the line are respectively;

negative sequence currents of a T point and an M point on the line respectively;

Z_2mt＝Z_1mtis the negative sequence impedance of line M-T;

and k is a fault distance measurement per unit value.

Specifically, as shown in fig. 4, the T-point compensation voltage difference includes:

take the M-T branch circuit to generate A phase fault (as shown in figure 2)

And (3) obtaining the compensated voltage difference of the T point of the fault branch by combining the formulas (5) to (7):

wherein:

the voltage of the end A of the M is the voltage,

for the M-terminal a-phase current,

is M-end zero sequence current;

for the phase a current at the T-terminal,

is T-end zero sequence current;

an a-phase voltage at fault point F;

other variable names are shown in formulas (1) to (4).

Due to the fact that

That is to say that the first and second electrodes,

it may be determined that lines N-T and P-T are non-faulty branches and that lines M-T are faulty branches.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.

Claims

1. A double-end distance measurement method for a T-connection line fault is characterized by comprising the following steps:

carrying out fault branch selection;

2. A T-connection line fault double-end ranging method as claimed in claim 1, characterized in that fault branch selection is performed through a composite sequence component compensation voltage algorithm.

3. A T-line fault double-ended ranging method as claimed in claim 1, wherein when the elected area result is valid, the non-faulted branch with shorter line is selected to calculate virtual T-terminal voltage.

4. The double-end distance measuring method for the T-connection line fault as claimed in claim 1, wherein when the elected area result is invalid, double-end distance measurement is performed on three branches respectively.

5. The T-connection line fault double-end ranging method according to claim 4, wherein in the double-end ranging results of the three branches, the branch with the smallest per unit value and larger than 0 and smaller than 1.00 is a fault branch.

6. The T-connection line fault double-end ranging method as claimed in claim 1, wherein in the case of an asymmetric fault, double-end ranging of the fault is carried out by using a double-end ranging algorithm of a negative sequence quantity.