CN109546631B - Distance protection method suitable for cross-voltage grade cross-line fault of same-tower four-circuit line - Google Patents
Distance protection method suitable for cross-voltage grade cross-line fault of same-tower four-circuit line Download PDFInfo
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
- H02H7/267—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured for parallel lines and wires
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Abstract
the invention relates to a distance protection method suitable for a cross-voltage grade cross-line fault of four circuit lines on the same tower, which comprises the following steps: collecting each phase voltage and current of each circuit in the same-tower mixed-voltage four-circuit; determining a fault line and a fault phase in the same-tower mixed-voltage four-circuit line through a phase selection element; calculating the voltage-class cross-line impedance of fault inter-phase cross-voltage, and determining the positive sequence impedance adopted during protection setting; and determining a distance protection setting value, and comparing the calculated trans-voltage class trans-line impedance with the distance protection setting value to determine distance protection action logic.
Description
Technical Field
the invention relates to the field of protection and control of power systems, in particular to a distance protection method suitable for cross-voltage grade cross-line faults of four-circuit lines on the same tower.
background
In order to solve the problems of the tension situation of power supply, the gradual reduction of power transmission corridors and the like, the construction conditions of a power transmission network are more and more complex, and the same-tower power transmission line erection mode is continuously applied to an extra-high voltage system. The same-tower multi-circuit power transmission technology has the advantages that due to the fact that the towers are shared, the required outgoing line corridor is narrow, limited corridor resources can be fully utilized, the occupied area of the land is reduced, meanwhile, the construction speed is high, the transmission capacity is high, investment is saved, and the like, and the requirements of a modern power system on power supply reliability and large-capacity power transmission can be well met.
the popularization of the same-tower power transmission mode also brings huge challenges to the fault analysis and relay protection of the power system. The mutual inductance coupling between phases and lines, multiple fault types between phases and across lines, various arrangement modes of lines, complex operation modes and the like exist in the same-tower power transmission line, so that the difficulty of fault analysis is greatly increased, and the line selection, phase selection, configuration and setting work of relay protection is greatly difficult. The same-tower power transmission line is often used as a main power link of a power grid and plays a role in huge power transmission, and the influence of safe operation on the power grid is great, so that incorrect actions of same-tower power transmission line protection can threaten safe and stable operation of the power grid, and even influence the safe operation of a power system, and therefore the requirement on the safety of relay protection by the same-tower multi-circuit line is higher. A great deal of research has been carried out at home and abroad on the cross-line faults of the same-voltage-class same-tower circuit, and the existing relay protection technology can also be well adapted. However, the cross-line fault of the same tower line with different voltage grades is rarely studied at home and abroad.
for the same-tower double-circuit line with the same voltage grade, when impedance parameters of the two circuits are the same and the complete transposition is carried out, the following steps are carried out:
the traditional impedance measurement based on the electric quantity of a single-circuit line cannot effectively identify the cross-line fault of the same-tower power transmission line. For the crossover faults of the double-circuit line, the distance protection theory can judge through the crossover impedance between two circuit faults:
wherein, 3I0 and 3I' 0 are zero sequence currents of the line and an adjacent line erected on the same tower, respectively, are zero sequence current compensation coefficients of the line and zero sequence current compensation coefficients of the adjacent line to the line.
however, in the four-circuit line with the same cross-voltage level and the same tower, the cross-line impedance is not suitable for judging the cross-line fault with the cross-voltage level any more due to different impedance parameters of the lines with different voltage levels.
disclosure of Invention
the invention aims to provide a distance protection method suitable for a cross-voltage grade cross-line fault of a same-tower four-circuit line, so as to solve the problem that the cross-voltage grade cross-line fault cannot be judged by a traditional distance protection method, and the cross-voltage grade cross-line fault of the same-tower mixed-voltage four-circuit line can be effectively judged. The technical scheme is as follows:
A distance protection method suitable for cross-voltage grade cross-line faults of four-circuit lines on the same tower is disclosed, wherein I is I, II, III and IV, and the method comprises the following steps:
(1) collecting each phase voltage and current of each circuit in same-tower mixed-voltage four-circuit
(2) determining a fault line and a fault phase in the same-tower mixed-voltage four-circuit line through a phase selection element;
(3) Calculating the fault inter-phase voltage-step trans-line impedance,
if the two faulty circuits are positioned on the same side of the tower, then:
If the two lines with faults are positioned on different sides of the tower, the method comprises the following steps:
wherein the content of the first and second substances,
the method is characterized in that the method comprises the following steps of (1) arranging lines with different voltage grades on the same side of a tower: the cross-voltage level cross-line impedance is expressed by the positive sequence impedance of the high-voltage level line between the phase of the line i and the phase psi of the line j;
the method is characterized in that the method comprises the following steps of (1) arranging lines with different voltage grades on the same side of a tower: the cross-voltage level cross-line impedance is expressed by the positive sequence impedance of the low-voltage level line between the phase of the line i and the phase psi of the line j;
The method is characterized in that the method comprises the following steps of (1) lines with different voltage grades positioned on different sides of a tower: the cross-voltage level cross-line impedance is expressed by the positive sequence impedance of the high-voltage level line between the phase of the line i and the phase psi of the line j;
the method is characterized in that the method comprises the following steps of (1) lines with different voltage grades positioned on different sides of a tower: the cross-voltage level cross-line impedance is expressed by the positive sequence impedance of the low-voltage level line between the phase of the line i and the phase psi of the line j;
is the voltage phasor of the phase of the failed high voltage class line i;
Is the voltage phasor of the psi phase of the failed low voltage class line j;
Is the current phasor of the phase of the failed high voltage class line i;
is the current phasor of the psi phase of the failed low voltage class line j;
ZU1 is the positive sequence impedance of the high voltage class line;
ZE1 is the positive sequence impedance of the low voltage class line;
ZMU is the phase-to-phase mutual impedance of the high voltage class line;
ZME is the phase-to-phase mutual impedance of the low voltage class lines;
z' MU is the line-to-line mutual impedance of the high voltage class lines;
z' ME is the line-to-line mutual impedance of the low voltage class line;
Z' Ms is the mutual impedance between the lines with different voltage grades on the same side of the tower;
z' Md is the mutual impedance between the lines with different voltage grades on different sides of the tower;
Is the zero sequence current of the faulted high voltage class line i;
is the zero sequence current of the faulted low voltage class line j;
Is the zero sequence current of the high voltage class line k without fault;
is the zero sequence current of the low voltage class line l without fault;
(4) determining positive sequence impedance adopted in distance protection setting;
when the cross-voltage level cross-line impedance is adopted or not, the positive sequence impedance adopted at the protection setting time is ZU1, and when the cross-voltage level cross-line impedance is adopted or not, the positive sequence impedance adopted at the protection setting time is ZE 1;
(5) And determining a distance protection setting value, and comparing the calculated trans-voltage class trans-line impedance with the distance protection setting value to determine distance protection action logic.
the invention considers the condition that the impedance parameters of the circuits with different voltage grades in the same tower mixed-voltage four-circuit are different, improves the calculation method of the cross-line impedance, overcomes the problem that the traditional distance protection method can not judge the cross-line fault of the cross-voltage grade, and can effectively judge the cross-line fault of the same tower mixed-voltage four-circuit of the cross-voltage grade.
drawings
FIG. 1 is a schematic diagram of a typical same-tower mixed-voltage four-circuit line
figure 2 is mutual inductance between mixed-voltage four-circuit lines of a typical same tower under ideal transposition
Detailed Description
typically, the same-tower mixed-voltage four-circuit power transmission line is formed by combining two groups of double-circuit lines with different voltage levels, and two ends of each group of double-circuit lines share a bus, as shown in fig. 1. When the lines are completely transposed, the impedance parameters of each group of double loops are the same, the self impedances of the high-voltage level line I, II and the low-voltage level lines III and IV are ZSU and ZSE respectively, the phase mutual impedances are ZMU and ZME respectively, and the positive sequence impedances are ZU 1-ZSU and ZE 1-ZSE-ZME respectively.
The mutual inductance between the four circuit lines of the mixed voltage of the same tower under ideal transposition is shown in figure 2. ZU1, ZE1 are positive sequence impedances for the high voltage class line and the low voltage class line, respectively. ZMU and ZME are interphase mutual impedance of the high-voltage-class line and the low-voltage-class line respectively, Z 'MU and Z' ME are line-to-line mutual impedance of the high-voltage-class line and the low-voltage-class line respectively, Z 'Ms is line-to-line mutual impedance of different voltage classes on the same side of the tower, and Z' Md is line-to-line mutual impedance of different voltage classes on the different side of the tower.
when the lines are completely transposed, only zero sequence components between the lines are coupled, and the coupling relationship is as follows:
wherein, the zero sequence voltage drop of each circuit is respectively; respectively, each circuit zero sequence current.
for the cross-voltage class cross-line faults on the same side of the tower, such as I and III, the fault phases meet the following relation:
wherein is the fault point voltage. This gives:
Therefore, the line-crossing impedance represented by the high-voltage class line positive sequence impedance ZU1 is:
the zero sequence currents of two fault lines are zero sequence currents of two healthy lines. The over-line impedance can also be represented by the low voltage level line positive sequence impedance ZE 1.
Similarly, for the overline fault of the overline voltage class at the different side of the tower, the overline impedance represented by ZU1 is:
The invention specifically adopts the following technical scheme.
According to the voltage and current information of each circuit in the same-tower mixed-voltage four-circuit, the cross-voltage level cross-circuit impedance of the fault circuit is calculated by using an improved cross-circuit impedance calculation method and is compared with a circuit distance protection impedance setting value, and therefore cross-voltage level cross-circuit faults are identified.
The invention is described in further detail below with reference to the following figures and examples:
step 1: collecting each phase voltage and current of each circuit in same-tower mixed-voltage four-circuit
The method comprises the steps of collecting each phase voltage of each circuit by using a voltage transformer, collecting each phase current of each circuit by using a current transformer, respectively connecting secondary windings of the voltage transformer and the current transformer into a microcomputer protection device, obtaining a sampling value of collected electrical quantity by AD conversion, and calculating the phasor value of the collected voltage and current by using a Fourier algorithm.
step 2: and determining a fault line and a fault phase in the same-tower mixed-voltage four-circuit line through a phase selection element.
and phase selection is carried out by calculating a phase current abrupt change amount, a phase current difference abrupt change amount, a fault sequence component and the like.
and step 3: calculating the fault inter-phase voltage-step trans-line impedance,
if the two faulty circuits are positioned on the same side of the tower, then:
if the two lines with faults are positioned on different sides of the tower, the method comprises the following steps:
wherein the sum is an expression in which the cross-voltage level cross-line impedance between the phase of line i and the phase ψ of line j is represented by ZU1 and ZE1, respectively; the zero sequence currents of the two circuits with faults are zero sequence currents of the two circuits without faults.
taking the cross-line fault occurring in the a phase of the line I and the B phase of the line III as an example, the cross-voltage level cross-line impedance represented by ZU1 calculated by the M-side protection device is:
the voltage of the I A phase and the III B phase of the line are respectively, the current of the IA phase and the III B phase of the line are respectively, and the zero sequence current of the I phase, the II phase, the III phase and the IV phase of the line are respectively.
And 4, step 4: the positive sequence impedance used for the distance protection settling timing is determined. When the voltage level is taken or taken across the line impedance, the positive sequence impedance taken for the protection timing should be ZU 1. When taken across voltage levels across line impedances or, the positive sequence impedance taken at the guard timings should be ZE 1.
since the above-mentioned ZIA IIIB (U) m is represented by ZU1, the positive sequence impedance used for the guard timing should be ZU 1.
(5) And judging whether the calculated voltage-level overline impedance meets the distance protection action condition. If the total length of the protection circuit is 80%, adopting or using the voltage-class overline impedance, and setting the distance protection value Zset to be 0.8ZU 1; when the voltage class is adopted or the line impedance is adopted, the distance protection setting value is Zset to be 0.8ZE 1.
if the total length of the protection line is 80%, the distance protection setting value is Zset to 0.8ZU 1. When the fault position is located in the distance protection setting range, the overline impedance calculated by the M-side protection device falls in the action area of the M-side protection device, the action condition is met, and the protection device sends a tripping command to a breaker of a fault line.
The working principle and the method of the invention are as follows:
in a typical same-tower mixed-voltage four-circuit line as shown in fig. 1, when the line is completely transposed, only zero-sequence components between the lines are coupled, and the coupling relationship is as follows:
wherein, the zero sequence voltage drop of each circuit is respectively; respectively, each circuit zero sequence current.
for the cross-voltage class cross-line faults on the same side of the tower, such as I and III, the fault phases meet the following relation:
Wherein is the fault point voltage. This gives:
therefore, the line-crossing impedance represented by the high-voltage class line positive sequence impedance ZU1 is:
The zero sequence currents of two fault lines are zero sequence currents of two healthy lines. The over-line impedance can also be represented by the low voltage level line positive sequence impedance ZE 1.
similarly, for the overline fault of the overline voltage class at the different side of the tower, the overline impedance represented by ZU1 is:
At this time, compared with the condition of the fault on the same side of the tower, only the positions of the inter-line mutual impedances Z 'Ms and Z' Md are exchanged.
The method is suitable for calculating the cross-voltage level cross-line impedance (including the same-name phase cross-line and the different-name phase cross-line) of the typical same-tower mixed-voltage four-circuit line.
an 1000/500kV same-tower mixed-voltage four-circuit simulation model is built by using EMTP, as shown in fig. 1, and the system power supply parameter is ZmU ═ ZnU ═ ZmE ═ ZnE ═ 0.1+ j30) Ω. The line adopts a phase domain frequency-dependent model, the total length l is 200km, the position is completely changed, and the impedance parameters are as follows.
under normal load, it is assumed that metallic overline faults (IA-IIIA, IA-IIIB overline ungrounded faults and IA-IIIA-G, IA-IIIB-G overline grounded faults) occur at different positions on the line from the end M of the busbar. The fault position is represented by the ratio alpha between the distance from the fault point to the bus M end and the total length of the line, the cross-line impedances of IA-IIIA and IA-IIIB represented by 1000kV line positive sequence impedance measured at the bus M end are represented by ZM.IA-IIIA (U) and ZM.IA-IIIB (U), respectively, the amplitude error of the cross-line impedance measured value is represented by delta Z (ZM.measured to be-Z1. lKM) to Z1. lKM, wherein Z1. lKM is a theoretical value of the cross-line impedance, and the angle error is represented by delta theta (argZM.measured to be-arg (Z1. lKM). The impedance of the flying lead measured at different locations of the fault is as follows.
therefore, the improved method for calculating the overline impedance aiming at the impedance parameter difference of the lines with different voltage grades can obtain that the error between the measurement value of the overline impedance and the theoretical value is not more than 2 percent under the condition of metallic short circuit.
Claims (1)
1. a distance protection method suitable for cross-voltage grade cross-line faults of four-circuit lines on the same tower is provided, wherein I is I, II, III and IV, and psi is A, B, C, and the method is characterized by comprising the following steps:
(1) collecting each phase voltage and current of each circuit in same-tower mixed-voltage four-circuit
(2) Determining a fault line and a fault phase in the same-tower mixed-voltage four-circuit line through a phase selection element;
(3) Calculating the fault inter-phase voltage-step trans-line impedance,
if the two faulty circuits are positioned on the same side of the tower, then:
If the two lines with faults are positioned on different sides of the tower, the method comprises the following steps:
Wherein the content of the first and second substances,
the method is characterized in that the method comprises the following steps of (1) arranging lines with different voltage grades on the same side of a tower: the cross-voltage level cross-line impedance is expressed by the positive sequence impedance of the high-voltage level line between the phase of the line i and the phase psi of the line j;
the method is characterized in that the method comprises the following steps of (1) arranging lines with different voltage grades on the same side of a tower: the cross-voltage level cross-line impedance is expressed by the positive sequence impedance of the low-voltage level line between the phase of the line i and the phase psi of the line j;
the method is characterized in that the method comprises the following steps of (1) lines with different voltage grades positioned on different sides of a tower: the cross-voltage level cross-line impedance is expressed by the positive sequence impedance of the high-voltage level line between the phase of the line i and the phase psi of the line j;
The method is characterized in that the method comprises the following steps of (1) lines with different voltage grades positioned on different sides of a tower: the cross-voltage level cross-line impedance is expressed by the positive sequence impedance of the low-voltage level line between the phase of the line i and the phase psi of the line j;
Is the voltage phasor of the phase of the failed high voltage class line i;
is the voltage phasor of the psi phase of the failed low voltage class line j;
is the current phasor of the phase of the failed high voltage class line i;
is the current phasor of the psi phase of the failed low voltage class line j;
ZU1 is the positive sequence impedance of the high voltage class line;
ZE1 is the positive sequence impedance of the low voltage class line;
ZMU is the phase-to-phase mutual impedance of the high voltage class line;
ZME is the phase-to-phase mutual impedance of the low voltage class lines;
Z' MU is the line-to-line mutual impedance of the high voltage class lines;
z' ME is the line-to-line mutual impedance of the low voltage class line;
Z' Ms is the mutual impedance between the lines with different voltage grades on the same side of the tower;
Z' Md is the mutual impedance between the lines with different voltage grades on different sides of the tower;
Is the zero sequence current of the faulted high voltage class line i;
is the zero sequence current of the faulted low voltage class line j;
is the zero sequence current of the high voltage class line k without fault;
Is the zero sequence current of the low voltage class line l without fault;
(4) Determining positive sequence impedance adopted in distance protection setting;
when the cross-voltage level cross-line impedance is adopted or not, the positive sequence impedance adopted at the protection setting time is ZU1, and when the cross-voltage level cross-line impedance is adopted or not, the positive sequence impedance adopted at the protection setting time is ZE 1;
(5) And determining a distance protection setting value, and comparing the calculated trans-voltage class trans-line impedance with the distance protection setting value to determine distance protection action logic.
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| CN111665415A (en) * | 2020-05-22 | 2020-09-15 | 南京国电南自新能源工程技术有限公司 | Cross-voltage-class same-tower four-circuit-line fault line selection method and device |
| CN112630588A (en) * | 2020-11-11 | 2021-04-09 | 大唐水电科学技术研究院有限公司 | Single-phase disconnection fault analysis method for four circuit lines on same pole |
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