CN111736007B - High-resistance grounding-oriented line zero-sequence direction overcurrent protection method, system and medium - Google Patents
High-resistance grounding-oriented line zero-sequence direction overcurrent protection method, system and medium Download PDFInfo
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Abstract
The invention discloses a high-resistance grounding-oriented line zero sequence direction overcurrent protection method, a system and a medium, wherein the method comprises the steps of judging the power flow direction of a line, and judging whether the fault direction of a power transmission end is a positive direction or not if the judgment result is the positive power flow; if the judgment result is the reverse power flow, judging whether the fault direction of the power receiving end is the reverse direction; and selecting and outputting a zero-sequence overcurrent protection action by combining the first zero-sequence current monitoring result and the power transmission end fault direction judgment result or the power receiving end fault direction judgment result. The invention is oriented to the high-resistance grounding line, judges the power flow direction of the line, judges the fault direction of the power transmission/receiving end, and selects and outputs the zero-sequence overcurrent protection action by combining the first zero-sequence current monitoring result and the fault direction judgment result of the power transmission/receiving end, so that the action can be reliably completed under the high-resistance grounding fault, and the sensitivity and the reliability of the zero-sequence overcurrent protection action of the line can be effectively improved.
Description
Technical Field
The invention relates to the field of transformer substation relay protection, in particular to a high-resistance grounding-oriented line zero-sequence direction overcurrent protection method, a high-resistance grounding-oriented line zero-sequence direction overcurrent protection system and a high-resistance grounding-oriented line zero-sequence direction overcurrent protection medium.
Background
In recent years, several high-resistance grounding faults of 110kV lines occur in a Hunan power grid, so that a corresponding 220kV main transformer override trip accident is caused, and certain power load loss and negative effects are caused. Under the high-resistance grounding fault, the zero sequence voltage is smaller, and the line protection is refused to operate when the zero sequence voltage threshold value of the line protection in the zero sequence direction overcurrent protection is not reached, so that the corresponding main transformer protection override trip is caused.
In view of simplifying the protection setting coordination, the single-ended line protection generally only applies three-segment distance protection and one-segment zero-sequence overcurrent protection. The zero-sequence overcurrent protection mainly deals with the non-metallic ground fault because of strong transition resistance and load impedance resistance. To ensure the selectivity, when both sides of the line have grounding points, the zero sequence overcurrent protection should also be put into the direction locking. At present, zero sequence overcurrent protection adopts a zero sequence voltage and zero sequence current ratio to judge a fault direction, and when the direction of the zero sequence voltage to the zero sequence current is near-100 degrees, the fault occurs in a positive direction. However, due to the high resistance ground fault, the zero sequence voltage is small, and the directional element based on the ratio of the zero sequence voltage to the zero sequence current may not act. Therefore, how to improve the sensitivity of the zero sequence overcurrent protection action of the circuit becomes a key technical problem to be solved urgently.
Disclosure of Invention
The technical problems to be solved by the invention are as follows: the invention provides a zero sequence direction overcurrent protection method, a system and a medium for a high-resistance grounding-oriented circuit, which aim at the high-resistance grounding-oriented circuit, judge whether the fault direction of a power transmission end is a positive direction or not and judge whether the fault direction of a power receiving end is a negative direction or not by judging the power flow direction of the circuit, and select and output a zero sequence overcurrent protection action by combining a first zero sequence current monitoring result and the fault direction judgment result of the power transmission end or the fault direction judgment result of the power receiving end, so that the action can be reliably completed under the high-resistance grounding fault, and the sensitivity and the reliability of the zero sequence overcurrent protection action of the circuit can be effectively improved.
In order to solve the technical problems, the invention adopts the technical scheme that:
a high-resistance grounding-oriented line zero sequence direction overcurrent protection method comprises the following implementation steps:
1) Judging the line power flow direction, and if the judgment result is the forward power flow, skipping to execute the step 2); if the judgment result is the reverse power flow, skipping to execute the step 3);
2) Judging whether the fault direction of the power transmission end is a positive direction or not, and skipping to execute the step 4);
3) Judging whether the fault direction of the power receiving end is the reverse direction or not, and skipping to execute the step 4);
4) Combining the first zero sequence current monitoring result and the judgment result of the fault direction of the power transmission end or the fault direction of the power receiving end to select and output a zero sequence overcurrent protection action, wherein the first zero sequence current monitoring result is used for judging that the zero sequence current is larger than a preset zero sequence current action value I set1 Whether or not this is true.
Optionally, the detailed steps of step 1) include:
1.1 If the angle difference of the three-phase voltage and phase current of the lines A, B and C is between (-45 DEG and 135 DEG), and the zero-sequence current is smaller than the zero-sequence current threshold value I set2 Judging that the power flow is in a positive direction, wherein a positive power flow judgment result is 1; if the angle difference of the three-phase voltage and the phase current of the lines A, B and C is between 135 DEG and 315 DEG, and the zero sequence current is smaller than the preset zero sequence current threshold value I set2 Judging that the power flow is in the opposite direction, wherein the judgment result of the reverse power flow is 1;
1.2 Exclusive or operation is carried out on the forward power flow judgment result and the reverse power flow judgment result, when the forward power flow judgment result is 1 and the reverse power flow judgment result is 0, the judgment result is the forward power flow, the time is delayed for 30s, and the step 2 is executed by skipping); and when the forward power flow judgment result is 0 and the reverse power flow judgment result is 1, the judgment result is the reverse power flow and is delayed for 10s, and the step 3) is executed.
Optionally, the detailed steps of step 2) include:
2.1 Each phase of the line is respectively judged according to the current direction, and when the angle difference between the phase voltage and the phase current is (-45 degrees and 135 degrees), the current direction judgment result is 1; judging the anti-load current element of each phase of the line respectively, wherein when the phase angle difference between the positive sequence current and the zero sequence current is (-30 degrees and 30 degrees), the judgment result of the anti-load current element is 1;
2.2 The current direction discrimination result of each phase of the circuit and the discrimination result of the anti-load current element are ANDed, and the discrimination result of the fault direction of the phase is output;
2.3 Or) the fault direction judging results of the three phases of the line are obtained to obtain the fault direction judging result of the line at the power transmission end.
Optionally, the detailed steps of step 3) include:
3.1 Each phase of the line is respectively judged according to the current direction, and when the angle difference between the phase voltage and the phase current is (135 degrees and 315 degrees), the current direction judgment result is 1; comparing the positive sequence current and the zero sequence current of each phase of the circuit respectively, and outputting a result of 1 when the angle difference between the positive sequence current and the zero sequence current is (-30 degrees and 30 degrees);
3.2 Respectively comparing the current direction judging result with the positive sequence current and zero sequence current phase comparison result to obtain a reverse fault judging result of a certain phase;
3.3 The judgment result of the reverse fault of the three phases of the line is taken or'd' to obtain the judgment result of the fault direction of the line at the power receiving end.
Optionally, the detailed steps of step 4) include:
4.1 The power transmission end fault reverse judgment result, the first zero sequence current monitoring result and the power transmission end judgment result are summed, and a power transmission end circuit zero sequence overcurrent protection action signal is output; after the receiving end fault reversal judgment result is negated, the negation is carried out on the receiving end fault reversal judgment result, and a receiving end circuit zero sequence overcurrent protection action signal is output;
4.2 Or the zero sequence overcurrent protection action signal of the power transmission end circuit and the zero sequence overcurrent protection action signal of the power receiving end circuit are delayed, and then the zero sequence current protection action signal is output.
In addition, the invention also provides a high-resistance grounding-oriented line zero-sequence direction overcurrent protection system, which comprises computer equipment, wherein the computer equipment is programmed or configured to execute the steps of the high-resistance grounding-oriented line zero-sequence direction overcurrent protection method.
In addition, the invention also provides a high-resistance grounding-oriented line zero-sequence direction overcurrent protection system, which comprises a computer device, wherein a computer program which is programmed or configured to execute the high-resistance grounding-oriented line zero-sequence direction overcurrent protection method is stored in a memory of the computer device.
In addition, the present invention also provides a computer readable storage medium, which stores thereon a computer program programmed or configured to execute the high resistance grounding-oriented line zero sequence direction overcurrent protection method.
In addition, the invention also provides a high-resistance grounding-oriented line zero sequence direction overcurrent protection system, which comprises:
the circuit power flow judging unit is used for judging whether the power flow in the circuit power flow direction is forward power flow, if the power flow is the forward power flow, 1 is output, and if not, 0 is output;
a power transmission end fault direction judging unit for judging whether the fault direction of the power transmission end is a positive direction, if so, outputting 1, otherwise, outputting 0;
the power receiving end fault direction judging unit is used for judging whether the fault direction of the power receiving end is the reverse direction or not, if the fault direction of the power receiving end is the reverse direction, 1 is output, and if the fault direction of the power receiving end is the reverse direction, 0 is output;
a first zero-sequence current monitoring unit for judging whether the zero-sequence current is larger than a first preset value I set1 Whether the result is true or not;
the forward power flow or logic is used for performing AND operation on the outputs of the circuit power flow judging unit, the first zero sequence current monitoring unit result and the power transmission end fault direction judging unit;
the reverse power flow or logic is used for negating the output of the line power flow judgment unit and then performing AND operation on the output of the first zero sequence current monitoring unit result and the output of the power transmission end fault direction judgment unit;
and the OR gate element is used for selecting whether to output the zero sequence overcurrent protection action or not according to the output of the forward power flow or logic and the reverse power flow or logic.
Compared with the prior art, the invention has the following advantages: the phase angle difference between the phase voltage and the phase current has obvious difference when the positive direction and the negative direction are failed: when a positive metallic single-phase earth fault occurs, the phase angle difference between the fault phase voltage and the phase current is (0 DEG, 90 DEG); when a reverse metallic fault single-phase earth fault occurs, the phase angle difference between the fault phase voltage and the phase current is (180 degrees and 270 degrees). Therefore, in the embodiment, a phase voltage and phase current ratio is adopted as a direction judging element of the zero-sequence overcurrent protection of the line, but some auxiliary criteria need to be added during specific implementation to improve the accuracy. For the power transmission end, the phase angle difference of phase voltage and phase current is between (0 degrees and 90 degrees) in normal operation and positive grounding fault. However, in a high-resistance ground fault, the phase angle difference between the phase voltage and the phase current may be (0 ° or 90 °) due to the influence of the load current in the reverse fault, which may interfere with the fault direction determination. Therefore, when a load-resisting current element is added and the condition that the direction element and the positive sequence current are in the same direction as the negative sequence current is simultaneously met, the positive direction fault of the power transmission end is judged. For the power receiving end, the phase angle difference of phase voltage and phase current is between (180 degrees and 270 degrees) in normal operation and reverse earth fault. But in reverse fault, the positive sequence current is in the same direction as the negative sequence current. Therefore, when the phase angle difference between the phase voltage and the phase current is (180 DEG, 270 DEG) and the positive sequence current and the negative sequence current are in the same direction, the fault is judged to be in the opposite direction. Of course, for a double ended power line, the line flow direction may change. Because the direction discrimination logics of the power transmission end and the power receiving end are different, the direction of the power flow needs to be discriminated in order to cope with the influence of the reverse power flow. On the basis, the zero sequence direction overcurrent protection method for the high-resistance grounding-oriented circuit is oriented to the high-resistance grounding-oriented circuit, judges whether the fault direction of a power transmission end is a positive direction or not and whether the fault direction of a power receiving end is a negative direction or not by judging the power flow direction of the circuit, and selects and outputs a zero sequence overcurrent protection action by combining a first zero sequence current monitoring result and a power transmission end fault direction judgment result or a power receiving end fault direction judgment result, so that the action can be reliably completed under the high-resistance grounding fault, and the sensitivity and the reliability of the zero sequence overcurrent protection action of the high-resistance grounding-oriented circuit can be effectively improved.
Drawings
FIG. 1 is a schematic diagram of a basic flow of a method according to an embodiment of the present invention.
FIG. 2 is a logic diagram of a method according to an embodiment of the present invention.
Detailed Description
As shown in fig. 1, the implementation steps of the high-resistance grounded line zero-sequence direction overcurrent protection method of this embodiment include:
1) Judging the line power flow direction, and if the judgment result is the forward power flow, skipping to execute the step 2); if the judgment result is the reverse power flow, skipping to execute the step 3);
2) Judging whether the fault direction of the power transmission end is a positive direction or not, and skipping to execute the step 4);
3) Judging whether the fault direction of the power receiving end is the reverse direction or not, and skipping to execute the step 4);
4) And selecting and outputting a zero sequence overcurrent protection action by combining the first zero sequence current monitoring result and the power transmission end fault direction judgment result or the power receiving end fault direction judgment result.
In this embodiment, the first zero-sequence current monitoring result is obtained by determining that the zero-sequence current is greater than a preset zero-sequence current action value I set1 Whether it is true, in general, the zero sequence current action value I set1 The value is 0.9 times of the setting value of the zero sequence overcurrent protection IV section.
In this embodiment, the detailed steps of step 1) include:
1.1 If the angle differences of the three phase voltages and phase currents of the lines A, B and C are all (-45 DEG, 135 DEG), and the zero sequence current is smaller than the zero sequence current threshold value I set2 When the power flow is determined to be a positive direction, the result of the positive power flow determination is 1, referring to areas B and d in fig. 2, the angle differences of the phase voltages and the phase currents of the three phases of the lines a, B and C are respectively expressed as (45 degrees, 135 degrees): -45 °<Arg(U A /I A ) <135°、-45°<Arg(U B /I B ) <135°、-45°<Arg(U C /I C ) <135 degrees, the zero sequence current is less than the zero sequence current threshold value I set2 Respectively expressed as: 3I0< I set2 (ii) a If the angle difference of the three-phase voltage and the phase current of the lines A, B and C is between (135 DEG, 315 DEG), and the zero sequence is simultaneously carried outThe current is less than the preset zero sequence current threshold value I set2 When the current is judged to be the reverse direction, the judgment result of the reverse current is 1; referring to regions B and d of fig. 2, the angle differences of the phase voltages and phase currents of the three phases of lines a, B, C are all represented at (135 °,315 °) respectively as: 135 deg. C<Arg(U A /I A ) <315°、135°<Arg(U B /I B ) <315°、135°<Arg(U C /I C ) <315 degrees with zero sequence current less than zero sequence current threshold value I set2 Respectively expressed as: 3I0< I set2 ；I set2 The zero sequence current threshold value is mainly used for avoiding the adverse effect of the change of the power flow direction on the directional element in the fault, and the value can be taken as the action value of the CT broken line zero sequence current.
1.2 Exclusive or operation is carried out on the forward power flow judgment result and the reverse power flow judgment result, when the forward power flow judgment result is 1 and the reverse power flow judgment result is 0, the judgment result is the forward power flow, the time is delayed for 30s, and the step 2 is executed by skipping); when the forward power flow judgment result is 0 and the reverse power flow judgment result is 1, the judgment result is the reverse power flow and is delayed for 10s, and the step 3) is executed in a skipping mode, as shown in areas b and d in fig. 2. As can be seen from the foregoing, the judgment of the direction of the tidal current is delayed by 10s when the tidal current reverses, and enough time is reserved for the zero-sequence overcurrent protection action of the circuit.
In this embodiment, the detailed steps of step 2) include:
2.1 The current direction discrimination is performed for each phase of the line, when the angle difference between the phase voltage and the phase current is (-45 °,135 °), the current direction discrimination result is 1, and referring to area a of fig. 2, the angle difference between the phase voltage and the phase current of the three phases of the lines a, B, and C is (-45 °,135 °), which is expressed as: -45 °<Arg(U A /I A ) <135°、-45°<Arg(U B /I B ) <135°、-45°<Arg(U C /I C ) <135 degrees; and (3) judging the anti-load current element for each phase of the line respectively, wherein when the phase angle difference between the positive sequence current and the zero sequence current is (-30 degrees and 30 degrees), the judgment result of the anti-load current element is 1, referring to the area a in fig. 2, the phase angle difference between the three phases of the positive sequence current and the zero sequence current of the lines A, B and C is (-30 degrees and 30 degrees), which are respectively expressed as: -30°<Arg(I 1A /I 0A ) <30°、-30°<Arg(I 1B /I 0B ) <30°、-30°<Arg(I 1C /I 0C ) <30°；
2.2 The current direction discrimination result of each phase of the line and the discrimination result of the anti-load current element are anded, and the discrimination result of the fault direction of the phase is output, see area a of fig. 2;
2.3 Or) the line three-phase fault direction determination results are taken to obtain the fault direction determination results of the line at the power transmission end, see area a in fig. 2.
In this embodiment, the detailed steps of step 3) include:
3.1 The current direction discrimination is performed for each phase of the line, when the angle difference between the phase voltage and the phase current is (135 °,315 °), the current direction discrimination result is 1, and referring to the area C of fig. 2, the angle difference between the phase voltage and the phase current of the three phases of the lines a, B, and C is (135 °,315 °), respectively, as follows: 135 degree<Arg(U A /I A ) <315°、135°<Arg(U B /I B ) <315°、135°<Arg(U C /I C ) <315 degrees; for each phase of the line, the positive sequence current and the zero sequence current are respectively compared, when the angle difference between the positive sequence current and the zero sequence current is (-30 degrees and 30 degrees), the output result is 1, referring to the region C in fig. 2, the angle difference between the three-phase positive sequence current and the zero sequence current of the lines a, B and C is (-30 degrees and 30 degrees), which is respectively expressed as: -30 °<Arg(I 1A /I 0A ) <30°、-30°<Arg(I 1B /I 0B ) <30°、-30°<Arg(I 1C /I 0C ) <30°；
3.2 Respectively comparing the current direction discrimination result with the positive sequence current and zero sequence current phase comparison result for each phase of the line to obtain a reverse fault discrimination result for a certain phase, see region c of fig. 2;
3.3 Or) the reverse fault determination results of the three phases of the line are taken to obtain the fault direction determination result of the line at the power receiving end, see the area c in fig. 2.
In this embodiment, the detailed steps of step 4) include:
4.1 The power transmission end fault reverse judgment result, the first zero sequence current monitoring result and the power transmission end judgment result are summed, and a power transmission end circuit zero sequence overcurrent protection action signal is output, see a component e in fig. 2; after the receiving end fault reversal judgment result is negated, the negation is carried out on the receiving end fault reversal judgment result, the first zero sequence current monitoring result and the receiving end judgment result are negated, and a receiving end circuit zero sequence overcurrent protection action signal is output, which is shown as a component f in fig. 2;
4.2 Or the zero sequence overcurrent protection action signal of the power transmission end circuit and the zero sequence overcurrent protection action signal of the power receiving end circuit are delayed, and then a zero sequence current protection action signal is output, which is shown as a component g in fig. 2.
In order to overcome the defect that a zero-sequence power directional element cannot be reliably opened due to small zero-sequence voltage when a high-resistance grounding fault occurs, the zero-sequence directional overcurrent protection method for the high-resistance grounding line of the embodiment adopts a phase voltage and phase current phase comparison result as a directional element of zero-sequence overcurrent protection, and simultaneously increases a positive-sequence current and zero-sequence current homodromous criterion as a locking condition of the directional element in order to avoid phase voltage and phase current phase comparison error caused by load current under the high-resistance grounding fault.
In addition, the present embodiment also provides a high-resistance grounding-oriented line zero-sequence direction overcurrent protection system, which includes a computer device programmed or configured to execute the steps of the aforementioned high-resistance grounding-oriented line zero-sequence direction overcurrent protection method.
In addition, the present embodiment also provides a high-resistance grounding-oriented line zero-sequence direction overcurrent protection system, which includes a computer device, where a memory of the computer device stores a computer program programmed or configured to execute the foregoing high-resistance grounding-oriented line zero-sequence direction overcurrent protection method.
Furthermore, the present embodiment also provides a computer readable storage medium, on which a computer program programmed or configured to execute the aforementioned high-resistance grounding-oriented line zero-sequence direction overcurrent protection method is stored.
In addition, this embodiment still provides a high resistance grounding oriented line zero sequence direction overcurrent protection system, its characterized in that includes:
the line power flow judging units (b and d) are used for judging whether the power flow in the line power flow direction is forward power flow, if the power flow is the forward power flow, 1 is output, and if not, 0 is output;
the power transmission end fault direction judging unit a is used for judging whether the fault direction of the power transmission end is a positive direction or not, outputting 1 if the fault direction is the positive direction, and otherwise outputting 0;
the power receiving end fault direction judging unit c is used for judging whether the fault direction of the power receiving end is the reverse direction or not, if the fault direction of the power receiving end is the reverse direction, 1 is output, and if the fault direction of the power receiving end is the reverse direction, 0 is output;
first zero sequence current monitoring unit (3I 0)> I set1 ) For judging that the zero sequence current is greater than a first preset value I set1 Whether the result is true or not;
the forward power flow or logic e is used for performing AND operation on the outputs of the line power flow judging unit, the first zero sequence current monitoring unit result and the power transmission end fault direction judging unit;
the reverse power flow or logic f is used for negating the output of the line power flow judgment unit and then carrying out AND operation on the output of the first zero sequence current monitoring unit result and the output of the power transmission end fault direction judgment unit;
and the OR gate element g is used for selecting whether to output a zero sequence overcurrent protection action or not according to the output of the forward power flow or logic and the reverse power flow or logic.
The processing modes of the units, logics and elements are all basic logical operations, and therefore, the units, logics and elements can be realized by hardware logic circuits or software.
As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein. The present application is directed to methods, apparatus (systems), and computer program products according to embodiments of the application wherein instructions, which execute via a flowchart and/or a processor of the computer program product, create means for implementing functions specified in the flowchart and/or block diagram block or blocks. These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks. These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
The above description is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments, and all technical solutions belonging to the idea of the present invention belong to the protection scope of the present invention. It should be noted that modifications and embellishments within the scope of the invention may occur to those skilled in the art without departing from the principle of the invention, and are considered to be within the scope of the invention.
Claims (8)
1. A high-resistance grounding-oriented line zero sequence direction overcurrent protection method is characterized by comprising the following implementation steps:
1) Judging the line power flow direction, and if the judgment result is the forward power flow, skipping to execute the step 2); if the judgment result is the reverse power flow, skipping to execute the step 3);
2) Judging whether the fault direction of the power transmission end is a positive direction or not, and skipping to execute the step 4);
3) Judging whether the fault direction of the power receiving end is the reverse direction or not, and skipping to execute the step 4);
4) Combining the first zero sequence current monitoring result and the judgment result of the fault direction of the power transmission end or the fault direction of the power receiving end to select and output a zero sequence overcurrent protection action, wherein the first zero sequence current monitoring result is used for judging that the zero sequence current is larger than a preset zero sequence current action value I set1 Whether the result is true;
the detailed steps of the step 1) comprise:
1.1 If the angle difference of the three-phase voltage and phase current of the lines A, B and C is between (-45 DEG and 135 DEG), and the zero-sequence current is smaller than the zero-sequence current threshold value I set2 Judging that the power flow is in the positive direction, wherein the judgment result of the positive power flow is 1; if the angle difference of the three-phase voltage and the phase current of the lines A, B and C is between 135 DEG and 315 DEG, and the zero sequence current is smaller than the preset zero sequence current threshold value I set2 Judging that the power flow is in the opposite direction, wherein the judgment result of the reverse power flow is 1;
1.2 Carrying out XOR operation on the forward power flow judgment result and the reverse power flow judgment result, when the forward power flow judgment result is 1 and the reverse power flow judgment result is 0, judging that the judgment result is the forward power flow and delaying for 30s, and skipping to execute the step 2); and when the forward power flow judgment result is 0 and the reverse power flow judgment result is 1, the judgment result is the reverse power flow and is delayed for 10s, and the step 3) is executed.
2. The high-resistance grounding-oriented line zero-sequence direction overcurrent protection method according to claim 1, wherein the detailed steps of step 2) comprise:
2.1 Respectively judging the current direction of each phase of the line, wherein when the angle difference between the phase voltage and the phase current is (-45 degrees and 135 degrees), the current direction judgment result is 1; respectively judging the anti-load current element of each phase of the circuit, wherein when the phase angle difference between the positive sequence current and the zero sequence current is (-30 degrees and 30 degrees), the judgment result of the anti-load current element is 1;
2.2 The current direction discrimination result of each phase of the circuit and the discrimination result of the anti-load current element are ANDed, and the discrimination result of the fault direction of the phase is output;
2.3 Or) the fault direction judging results of the three phases of the line are obtained to obtain the fault direction judging result of the line at the power transmission end.
3. The high-resistance grounding-oriented line zero-sequence direction overcurrent protection method according to claim 1, wherein the detailed steps of the step 3) include:
3.1 Respectively judging the current direction of each phase of the line, wherein when the angle difference between the phase voltage and the phase current is (135 degrees and 315 degrees), the current direction judgment result is 1; comparing each phase of the circuit with positive sequence current and zero sequence current respectively, and outputting a result of 1 when the angle difference between the positive sequence current and the zero sequence current is (-30 degrees and 30 degrees);
3.2 Respectively comparing the current direction judging result with the positive sequence current and zero sequence current phase comparison result to obtain a reverse fault judging result of a certain phase;
3.3 The judgment result of the reverse fault of the three phases of the line is taken or'd' to obtain the judgment result of the fault direction of the line at the power receiving end.
4. The high-resistance grounding-oriented line zero-sequence direction overcurrent protection method according to claim 1, wherein the detailed step of the step 4) comprises the following steps:
4.1 The power transmission end fault reverse judgment result, the first zero sequence current monitoring result and the power transmission end judgment result are summed, and a power transmission end circuit zero sequence overcurrent protection action signal is output; after the receiving end fault reversal judgment result is negated, the negation is carried out on the receiving end fault reversal judgment result, and a receiving end circuit zero sequence overcurrent protection action signal is output;
4.2 Or the zero sequence overcurrent protection action signal of the power transmission end circuit and the zero sequence overcurrent protection action signal of the power receiving end circuit are delayed, and then the zero sequence current protection action signal is output.
5. A high resistance grounded facing line zero sequence direction overcurrent protection system comprising computer equipment, characterized in that the computer equipment is programmed or configured to perform the steps of the high resistance grounded facing line zero sequence direction overcurrent protection method of any one of claims 1 to 4.
6. A high-resistance grounding-oriented line zero-sequence direction overcurrent protection system comprises computer equipment, and is characterized in that a computer program which is programmed or configured to execute the high-resistance grounding-oriented line zero-sequence direction overcurrent protection method according to any one of claims 1 to 4 is stored in a memory of the computer equipment.
7. A computer readable storage medium, characterized in that the computer readable storage medium has stored thereon a computer program programmed or configured to execute the high resistance grounding-oriented line zero sequence direction overcurrent protection method of any one of claims 1 to 4.
8. The utility model provides a circuit zero sequence direction overcurrent protection system towards high resistance ground connection which characterized in that includes:
and the line power flow judging unit is used for judging whether the power flow in the line power flow direction is a forward power flow, if the power flow in the line power flow direction is the forward power flow, outputting 1, and otherwise, outputting 0: if the angle difference of the three-phase voltage and the phase current of the lines A, B and C is between (-45 degrees and 135 degrees), and the zero sequence current is smaller than the zero sequence current threshold value I set2 Judging that the power flow is in the positive direction, wherein the judgment result of the positive power flow is 1; if the angle difference of the three-phase voltage and the phase current of the lines A, B and C is between 135 DEG and 315 DEG, and the zero sequence current is smaller than the preset zero sequence current threshold value I set2 Judging that the power flow is in the opposite direction, wherein the judgment result of the reverse power flow is 1; performing exclusive-or operation on the forward power flow judgment result and the reverse power flow judgment result, when the forward power flow judgment result is 1 and the reverse power flow judgment result is 0, judging that the judgment result is forward power flow, delaying for 30s, and skipping to execute a power transmission end fault direction judgment unit; when the forward power flow judgment result is 0 and the reverse power flow judgment result is 1, the judgment result is reverse power flow, the time is delayed for 10s, and a power receiving end fault direction judgment unit is skipped to execute;
the power transmission end fault direction judging unit is used for judging whether the fault direction of the power transmission end is a positive direction or not, outputting 1 if the fault direction of the power transmission end is the positive direction, and otherwise outputting 0;
the power receiving end fault direction judging unit is used for judging whether the fault direction of the power receiving end is the reverse direction or not, if the fault direction of the power receiving end is the reverse direction, 1 is output, and if the fault direction of the power receiving end is the reverse direction, 0 is output;
a first zero-sequence current monitoring unit for judging whether the zero-sequence current is greater than a first preset value I set1 Whether the result is true or not;
the forward power flow or logic is used for performing AND operation on the outputs of the line power flow judgment unit, the first zero sequence current monitoring unit result and the power transmission end fault direction judgment unit;
the reverse power flow or logic is used for negating the output of the line power flow judgment unit and then performing AND operation on the output of the first zero sequence current monitoring unit result and the output of the power transmission end fault direction judgment unit;
and the OR gate element is used for selecting whether to output the zero sequence overcurrent protection action or not according to the output of the forward power flow or logic and the reverse power flow or logic.
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