CN100365900C - High-voltage transmission circuitry null sequence directional element for power system - Google Patents
High-voltage transmission circuitry null sequence directional element for power system Download PDFInfo
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- 238000004088 simulation Methods 0.000 description 8
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- 235000019083 Osmanthus fragrans Nutrition 0.000 description 4
- 244000242564 Osmanthus fragrans Species 0.000 description 4
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- 230000009466 transformation Effects 0.000 description 4
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- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 2
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- 235000019082 Osmanthus Nutrition 0.000 description 1
- 241000333181 Osmanthus Species 0.000 description 1
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Abstract
The present invention relates to a zero-sequence directional element of a high-voltage electricity transmission line of a power system, which can be transformed into a phasor value according to sampled values of the A, B and C three-phase voltage and a current so that the zero-sequence voltage and the current can be obtained. An amplitude value of the zero-sequence voltage is compared with a threshold value, when |U0 |<|U0 dz | is not met, and a fault direction is judged by adopting Arg 3U0/3I0, for example, when the Arg 3U0/3I0 is at (-190 DEG C,-30 DEG C), a directional element acts; otherwise, the directional element is locked; when |U0 |<|U0 dz | is not met, for example, when a phase selecting element is judged into a phi phase grounding fault, a single phase alternative scheme Arg (-U phi) /I0 is adopted to judge a fault direction; when the Arg (-U phi) /I0 is at (-230 DEG C,-50 DEG C), the directional element acts; otherwise, the directional element is locked; when the phase selecting element is judged into a phi-phi double grounding fault, a two-phase alternative scheme is adopted to judge the fault direction; when a positive direction is judged, the action is carried out; otherwise, the directional element is locked. The present invention ensures the accuracy of the direction judge by the method that a fixed value of the zero sequence voltage is improved when the voltage is above the fixed value; when the zero sequence voltage is very little even is zero, the memory voltage at the protection-installation point is adopted and replaces the zero sequence voltage according to a fault type; the present invention has the explicit directivity by the method the corresponding maximal sensitive angle is adjusted.
Description
Technical Field
The invention relates to a relay protection method for an electric power system, in particular to a protection method for a high-voltage transmission line in a zero sequence direction of the electric power system.
Background
The zero sequence direction protection in the power system has the advantages of no influence of an operation mode and system oscillation and high sensitivity, and is widely applied to the protection of high-voltage and ultrahigh-voltage transmission lines. However, due to the high voltage, the extra-high voltage transmission line is generally long, and the line impedance is much larger than the system impedance. When the short circuit occurs at the far end inside and outside the line or through a transition resistor, the situation that zero-sequence current exists and the zero-sequence voltage is very small or even zero can occur, the directional element has the difficulty of insufficient voltage sensitivity, and the normal state or the short-circuit fault cannot be distinguished, so that the malfunction of directional protection is caused, and the problem cannot be solved by the conventional zero-sequence directional protection.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a protection method for the zero sequence direction of a high-voltage transmission line of an electric power system, which can solve the problem of a large power supply with insufficient voltage sensitivity and ensure the direction judgment accuracy.
In order to achieve the purpose, the invention adopts the technical scheme that: firstly, according to sampling values of three-phase voltages and currents A, B and C, converting the three-phase voltages and currents into phasor values to obtain zero-sequence electricityVoltage and current; comparing the zero sequence voltage amplitude value with a threshold value, wherein the threshold value is 2-3V, and selecting different criteria to perform direction judgment: if \\58360 0 |＜| 0dz L is not true, in the formula, | \58360 0 L is zero sequence voltage amplitude, | \58360 0dz I is a threshold value, adoptTo determine the direction of the fault, e.g.
At (-190 °, -30 °), the directional element is actuated, whereas the directional element is blocked; if \\58360 0 |＜| 0dz If the phase selection element judges that the phi phase is in ground fault, a single-phase alternative scheme is adopted
To determine the direction of failure, e.g.At (-230, -50) the directional element is actuated, whereas the directional element is blocked; if the phase selection element judges that the two-phase grounding fault occurs, a two-phase alternative scheme is adopted to judge thatAnd if the barrier direction is judged to be the positive direction, the direction element acts, and otherwise, the direction element is locked.
The invention ensures the accuracy of direction discrimination when the zero sequence voltage is over the fixed value by improving the fixed value of the zero sequence voltage, and when the zero sequence voltage is very small or even zero, the memory voltage at the protective installation position is adopted to replace the zero sequence voltage according to the fault type, and the invention has definite directionality by adjusting the corresponding maximum sensitive angle.
Drawings
FIG. 1 is a logic block diagram of the present invention;
fig. 2 is a diagram of a single-phase short-circuit system of a far end of a double-end power line through a transition resistor, wherein M and N are two power supplies respectively, and for protection 1 installed on the side M, the single-phase ground fault of the far end of the line is shown;
FIG. 3 is a diagram of a composite sequence network of single-phase short-circuit faults of a double-end power supply, which is a zero sequence network, a negative sequence network and a positive sequence network from top to bottom respectively;
FIG. 4 is an equivalent diagram of a double-ended power supply single-phase short-circuit fault composite sequence network, wherein the zero sequence network is not moved, and the positive sequence network and the negative sequence network are equivalent to a power supply and an equivalent resistor through thevenin;
FIG. 5 is a diagram of the operation characteristics of the zero sequence directional element after the phase voltage is substituted, wherein the shaded portion is the boundary between the operation region and the non-operation region; the lower left is the action zone. The action zone is (-230 degrees, -50 degrees), -50 degrees, -130 degrees is the non-action zone;
fig. 6 is a wiring diagram of a volleyball wire fault system, wherein a short-circuit point is on a 110kV wire on the changed back side of the volleyball mountain, and the short-circuit point is a C-phase grounding fault.
FIG. 7 is a comparison graph of waveforms before and after the osmanthus fragrans transformation adopts the method of the present invention, wherein the abscissa is the number of sampling points (1 ms sampling is used in the present simulation, i.e. each sampling interval is 1 ms), and the ordinate is the phase angle in degrees (the angle of the ordinate before the method of the present invention is adopted is 1 ms)
After the invention is adopted, the angle of the vertical coordinate is
FIG. 8 is a comparison graph of waveforms before and after the present invention is applied to the clique-mountain transformation, wherein the abscissa is the number of sampling points (1 ms sampling is used in the present simulation, i.e., each sampling interval is 1 ms), and the ordinate is the phase angle in degrees (the angle of the ordinate is 1ms before the present invention is applied)The angle of the longitudinal coordinate is
FIG. 9 is a comparison graph of waveforms before and after the Jintang transform adopted the present invention, in which the abscissa is the number of sampling points (1 ms sampling is used in the present simulation, i.e., each sampling interval is 1 ms), and the ordinate is the phase angle in degrees (by adopting the present invention)The angle of the longitudinal axis of the front is
After the invention is adopted, the angle of the vertical coordinate is
FIG. 10 is a comparison graph of waveforms before and after Tandong change by using the present invention, in which the abscissa is the number of sampling points (1 ms sampling is used in the present simulation, i.e., each sampling interval is 1 ms), and the ordinate is the phase angle in degrees (the angle of the ordinate is 1ms before using the present invention)
After the invention is adopted, the angle of the vertical coordinate is
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings.
According to the sampling values of the three-phase voltages and currents A, B and C, the zero-sequence voltages and currents are obtained after the sampling values of the three-phase voltages and currents are converted into phasor values; and then comparing the zero sequence voltage amplitude with a threshold value, wherein the threshold value is 2-3V, and selecting different criteria to judge the direction. Referring to fig. 1, a logic block diagram of the present invention is shown. In the figure, "&" represents "and" + "represents" or ", and only if the logic condition shown in the logic block diagram is satisfied, the forward fault is judged, and a trip command is issued, otherwise, the direction element is locked. The specific judgment mode is expressed in the following characters:
a) If \\58360 0 |＜| 0dz L is not true, in the formula, | \58360 0 L is zero-sequence voltage amplitude, | \58360 0dz The | is a threshold value, which indicates that the zero sequence voltage meets the sensitivity requirement;
by using
To determine the direction of failure, e.g.
At (-190 °, -30 °) the directional element is actuated, whereas the directional element is blocked;
b) If \\58360 0 |＜| 0dz If the l is true, the zero sequence voltage does not meet the sensitivity requirement;
if the phase selection element judges that the phase is connected to the ground, a single-phase alternative scheme is adopted
Determining the direction of the fault, e.g.
At (-230, -50) the direction element is actuated, whereas the direction element is blocked;
if the phase selection element judges that the phase phi is grounded, a two-phase alternative scheme is adopted to judge the fault direction, if the phase phi is judged to be positive, the direction element is operated, otherwise, the direction element is locked.
Most of power system circuits are single-phase faults, and the insufficient sensitivity of zero-sequence voltage mainly occurs in the condition of single-phase high-resistance grounding. In the following, a solution is given by taking a single-phase ground fault as an example, and two phases are grounded similarly.
Referring to fig. 2, a double-end power system is shown, where M and N are two power sources, and 1 and 2 are protection devices installed at buses at two ends of a line, respectively. For the protection device 1 mounted on the M-side bus, the line has a ground short fault at the far end via the transition resistance Rg. For a fault, the composite sequence network is connected in series by positive sequence network, negative sequence network and zero sequence network according to the boundary conditions which the voltage and the current of the fault should meet.
As shown in fig. 3, the zero-order net, the negative-order net and the positive-order net are arranged from top to bottom in the figure. Wherein Z SM0 ，Z SM1 ， Z SM2 ，Z SN0 ，Z SN1 ，Z SN2 Zero sequence, positive sequence and negative sequence system impedances of the M end and the N end respectively; z is a linear or branched member l10 、Z l12 And Z l11 Zero, negative and positive sequence line impedances, Z, respectively, of the M-end busbar of the line to the short-circuit point l20 、Z l22 And Z l21 Zero sequence, negative sequence and positive sequence line impedances from a bus at the N end of the line to a short-circuit point respectively; e M And E N Electromotive force of the M-terminal power supply and the N-terminal power supply respectively; r is g Is the transition resistance. The series connection part of the positive sequence network and the negative sequence network can be equivalent to the series connection of a power supply and an equivalent impedance according to the Davining equivalent theorem, and the zero sequence network is fixed. FIG. 4 shows the equivalent complex sequence net (zero sequence net part in the figure, system impedance Z) SM 、Z SN And line impedance Z l1 、Z l2 All are zero sequence impedances, and subscript 0 has been omitted for simplicity of labeling). Wherein Z1 is a positive sequence net equivalent impedance, and Z2 is a negative sequence net equivalent impedance, \58360 A The equivalent power source electromotive force is the A-phase voltage before the fault point. Considering the ideal situation, the line is in an unloaded state before the fault, i.e. the current flowing through the line is zero, the a-phase voltage at the fault point and the a-phase voltage at the bus are equal. Therefore, the equivalent electromotive force of the composite sequence net is- \58360 A ( A Is the pre-fault a-phase voltage at the bus).
1) Considering the simple case first, assume the transition resistance R g ＝0
At the protection installation site, satisfy
Where k is the line branching coefficient.
Because of the system impedance A sm ，Z sn And line impedance Z L1 The impedance angles are approximately equal, so the equivalent impedance of the positive and negative sequence nets can also be approximated by the line impedance angle Z L Thus having
Thus, one can use- \58360 A Replacing \58360 0 Overcoming the defect of 58360 0 The fault direction can be judged correctly with very low defect.
2) Transition resistance R g Not equal to 0, i.e. taking into account the effect of transition resistance
Also taking into account the system impedance Z sm ，Z sn And line impedance Z L1 The impedance angles are approximately equal, and
because R is g E (0, infinity), so arg [ Z L +kR g ]∈(0，argZ L )
So that it can be set to-180 ° +0.5argZ L As the maximum sensitivity angle, the general line impedance angle is 80 °, and the maximum sensitivity angle is-140 °.
Fig. 5 is a diagram showing the operation characteristics of the directional element, in which the hatched portion is the boundary line between the operation region and the non-operation region, the lower left half of the plane is the operation region, and the other half of the plane is the non-operation region. \58388inthe figure ZL Is a line impedance angle, and the dotted line shows a half of the line impedance angle, namely 0.5 \58388 ZL The dotted line is at the maximum sensitivity angle of-180 ° +0.5argZ in the motion region L . The area of the maximum sensitivity angle plus or minus 90 degrees is the action area, the action area is (-230 degrees, -50 degrees), and the non-action area is (-50 degrees, -130 degrees).
Namely, it is
When the element is in the action area, the element acts; otherwise the direction element is blocked.
For pre-fault voltages, \58360 A + B + C =0, i.e., \58360 A ＝ B + C
Thus, the resistance can be used no matter how large the transition resistance isOr alternativelySubstitute for
As long as the maximum sensitivity angle to be protected is defined by-argZ L Adjusted to-0.5 argZ L And the correct action of the zero sequence directional element can be ensured. Therefore, the problem of insufficient sensitivity of very low or even zero sequence voltage is solved.
The above discussion is of an ideal no-load condition, and for a non-no-load state, the voltage drop along the line is generally 10%, and in addition, the angular offset of the voltage is not large, and considering that a certain margin angle exists in the direction protection, the discussion result of the no-load state is also applicable to the non-no-load state, which is verified in an actual field.
When the zero-sequence voltage is lower than the threshold value, the fault phase voltage at the protection installation position is used for replacing the zero-sequence voltage; when the fault phase voltage is very low, the zero sequence voltage is generally larger and still adopted
That is, the failure direction can still be correctly determined.
The simulation results of the invention for partial field wave recording data are given as follows:
the recording data come from Hunan Gui wire accident and a tan gold wire accident respectively, the zero sequence direction protection in the existing protection device cannot solve the difficulty of insufficient sensitivity of zero sequence voltage, and when the zero sequence voltage is very low, false operation occurs. To verify the effectiveness of the present invention, simulations were performed using the fault measurement data.
Simulation result one: accident of Hunan Tuiguan line
In 2004, CN ground fault occurs in the next 110kV line of the 220kV Gui group line in 4-month lake south. Fig. 6 shows the main wiring diagram of the system. Wherein S is a system power supply, and a 220kV line is arranged between the sweet osmanthus transformer and the Yuanshan transformer by 10 km. And a CN ground fault point on the 110kV line is positioned at the back side of the cluster mountain transformer substation, the cluster mountain transformer substation is judged to be a reverse fault, the osmanthus transformer substation is judged to be a forward fault, and the protection is not operated. But 3U is adopted due to the low zero sequence voltage of the cluster mountain 0 And the value is approximately equal to 2V, and the fault is judged as a positive fault. Fig. 7 and 8 are phase angle waveforms before and after the solution is adopted for osmanthus fragrans transformation and cliff transformation, respectively. Therefore, for the osmanthus fragrans, the front phase angle and the rear phase angle are both in the action area, so that the normal phase fault can be accurately judged. For the change of the clique mountain, before the invention is adopted, the fluctuation is large in the action area and the non-action area, the phase angle fluctuation enters (170 degrees and 330 degrees), namely (-190 degrees and-30 degrees) in the action area, the reverse fault is judged as the forward fault by mistake, and the false action occurs. After the invention is adopted, the phase angle is always in the non-action area, and the fault is reliably judged to be a reverse fault, so that the fault is reliably prevented from action.
And a second simulation result: accident of pool gold thread
In 2004, a next-level line BN ground fault occurs to a pool gold wire in 8 months, a fault point is outside a pool-east substation area and belongs to a reverse fault B, while a King-Tang substation is in a forward-direction-outside fault, but the zero-sequence voltage is very low, so that the pool-east substation misjudges that the fault is a forward fault, and the false operation is protected.
Fig. 9 and 10 are phase angle waveforms before and after the solution is adopted by the kindergarten substation and the puddle substation, respectively. Therefore, the front phase angle and the rear phase angle of the Kingtang transformer substation adopting the solution are both in the action area, and the fault direction can be accurately judged to be a forward fault. Before a solution is adopted by a Tandong substation,
is always in (-190 degrees, -30 degrees) motionMaking a zone, and judging the zone to be a forward direction by mistake; after the invention is adopted, the direction is in a non-action area of (-50 degrees and 130 degrees), and the fault is judged to be a reverse fault and is reliably not acted.
In a word, the direction element can accurately judge the fault direction when the zero sequence voltage is very low or even zero, and prevent misoperation. The existing direction protection only adopts a compensation method, and the problem of insufficient sensitivity of zero sequence voltage cannot be solved in principle.
Claims (1)
1. A method for protecting a high-voltage transmission line in a zero sequence direction of an electric power system is characterized by comprising the following steps:
1) Firstly, converting three-phase voltage and current values into phasor values according to sampling values of three-phase voltages and currents A, B and C to obtain zero-sequence voltages and currents;
2) Comparing the zero sequence voltage amplitude with a threshold value, wherein the threshold value is 2-3V, and selecting different criteria to judge the direction:
a) If \\58360 0 |＜| 0dz If the | is not true, in the formula, | \58360 0 L is zero sequence voltage amplitude, | \58360 0dz I is a threshold value, adopt
To determine the direction of failure, e.g.
At (-190 °, -30 °), the directional element is actuated, whereas the directional element is blocked;
b) If \\58360 0 |＜| 0dz I is true:
if the phase selection element judges that the phase is connected to the ground, a single-phase alternative scheme is adopted
Determining the direction of the fault, e.g.At (-230 °, -50 °), the directional element is actuated, whereas the directional element is blocked;
if the phase selection element judges that the two-phase earth fault occurs, the two-phase alternative scheme is adopted to judge the fault direction, if the phase selection element judges that the fault direction is positive, the direction element acts, otherwise, the direction element is locked.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102692571A (en) * | 2012-04-27 | 2012-09-26 | 国电南瑞科技股份有限公司 | Distinguishing method for directional element in phase overcurrent protection of transformer |
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| CN101699688B (en) * | 2009-08-20 | 2012-06-20 | 北京四方继保自动化股份有限公司 | Relay protection method and relay protection device |
| CN102637222A (en) * | 2012-03-13 | 2012-08-15 | 中国海洋石油总公司 | Method for simulating interconnection of turbine unit and grid system |
| CN102818973B (en) * | 2012-09-03 | 2014-11-19 | 武汉大学 | Phase sequence voltage amplitude comparison-based failure phase selection method and device |
| CN102879713A (en) * | 2012-11-01 | 2013-01-16 | 天津市电力公司 | Ground protection circuit selection method |
| CN103728537B (en) * | 2013-12-24 | 2016-03-02 | 海南电网公司 | A kind of fault direction judgement system of no-voltage dead band and method of discrimination |
| CN105207184B (en) * | 2015-10-12 | 2016-11-30 | 国家电网公司 | A kind of zero-sequence direction component for Neutral Grounding through Resistance in Electrical system |
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| CN1332506A (en) * | 1995-10-20 | 2002-01-23 | 斯维则工程实验室公司 | Zero-sequence voltage direction polarizing element for protecting relay |
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Address after: 710077, room 3, building 3, building 2, No. 85, No. 301, Zhang Lu, Xi'an hi tech Zone, Shaanxi, China Patentee after: XI'AN XIRUI CONTROL TECHNOLOGY CO., LTD. Address before: 710077, Shaanxi, Xi'an hi tech Zone, No. 85, No. 2 Road, modern enterprise Center East Patentee before: Xi'an Xirui Protection Control Equipment Co., Ltd. |
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Effective date of registration: 20190104 Address after: 710075 Room 901, Building 3, Innovative Business Apartment, 69 Jinye Road, Yanta District, Xi'an City, Shaanxi Province Patentee after: Xi'an Shengzhi Software Technology Co., Ltd. Address before: Room 301, Room 3, Building 3, No. 2, Zhangbawu Road, Xi'an High-tech Zone, Shaanxi Province, 710077 Patentee before: XI'AN XIRUI CONTROL TECHNOLOGY CO., LTD. |
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Effective date of registration: 20210624 Address after: Room 601, 102 office building, Xirui Industrial Park, 569 Jincheng Third Road, Xi'an Economic and Technological Development Zone, Shaanxi Province, 710018 Patentee after: Shaanxi jinchunteri Software Technology Co.,Ltd. Address before: 710075 Room 901, Building 3, Innovative Business Apartment, 69 Jinye Road, Yanta District, Xi'an City, Shaanxi Province Patentee before: Xi'an Shengzhi Software Technology Co.,Ltd. |