CN115085163A - Differential protection method, system and device for low-frequency power transmission line and storage medium - Google Patents
Differential protection method, system and device for low-frequency power transmission line and storage medium Download PDFInfo
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- CN115085163A CN115085163A CN202210818059.6A CN202210818059A CN115085163A CN 115085163 A CN115085163 A CN 115085163A CN 202210818059 A CN202210818059 A CN 202210818059A CN 115085163 A CN115085163 A CN 115085163A
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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
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/0092—Arrangements for measuring currents or voltages or for indicating presence or sign thereof measuring current only
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/165—Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values
- G01R19/16533—Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values characterised by the application
- G01R19/16538—Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values characterised by the application in AC or DC supplies
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/26—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents
- H02H3/28—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents involving comparison of the voltage or current values at two spaced portions of a single system, e.g. at opposite ends of one line, at input and output of apparatus
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/26—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents
- H02H3/28—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents involving comparison of the voltage or current values at two spaced portions of a single system, e.g. at opposite ends of one line, at input and output of apparatus
- H02H3/30—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents involving comparison of the voltage or current values at two spaced portions of a single system, e.g. at opposite ends of one line, at input and output of apparatus using pilot wires or other signalling channel
- H02H3/305—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents involving comparison of the voltage or current values at two spaced portions of a single system, e.g. at opposite ends of one line, at input and output of apparatus using pilot wires or other signalling channel involving current comparison
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Abstract
The invention discloses a differential protection method, a system, a device and a storage medium of a low-frequency power transmission line, wherein the method comprises the following steps: collecting a line current; taking R at current 1 A sampling point, if R 1 S is accumulated in each sampling point 1 If the current value of each sampling point is larger than the first threshold value, a first criterion is established; respectively taking continuous sampling points on the positive and negative half cycles of the current, if S is continuously present in the sampling points 2 If the current value of each sampling point is larger than the second threshold value, a second criterion is satisfied; taking R between two zero crossings of the current 3 A sampling pointIf R is 3 In a sampling point, there is S continuously 3 If the current value of each sampling point is greater than the first threshold value, a third criterion is satisfied; sampling points are taken from the current, and if the current value of the sampling points is greater than the conventional steady-state quantity differential current and a low-ratio braking action threshold, the fourth criterion is satisfied; if at least one of the first criterion, the second criterion and the third criterion is true and the fourth criterion is true, differential protection is performed; the invention can realize the rapid and accurate action of differential protection.
Description
Technical Field
The invention relates to a differential protection method, a differential protection system, a differential protection device and a storage medium for a low-frequency power transmission line, and belongs to the technical field of relay protection.
Background
The traditional current phasor differential protection principle is simple, the sensitivity is high, the device is suitable for various complex working conditions of system oscillation and non-equality, the device is suitable for power networks with various grid structures, has natural phase selection capability, and is widely applied to power systems.
When the line has an internal fault, the regulating and controlling function of the power electronic devices (M3C) at two ends of the low-frequency transmission line enables the amplitude of the fault current at two ends of the line to be limited and to present certain ride-through characteristics, so that the sensitivity of the traditional differential protection is reduced, even the operation is rejected, and the normal operation of the low-frequency transmission system is seriously influenced; and the frequency of the low-frequency power transmission system is reduced, the calculation data window of the phasor differential protection is correspondingly lengthened, and the protection snap performance is reduced.
Disclosure of Invention
The invention aims to overcome the defects in the prior art, provides a differential protection method, a differential protection system, a differential protection device and a storage medium for a low-frequency power transmission line, aims at solving the problem of abnormal operation of the low-frequency power transmission line differential protection, and constructs a differential protection criterion based on a sampling value differential principle to realize rapid and accurate operation of differential protection.
In order to achieve the purpose, the invention is realized by adopting the following technical scheme:
in a first aspect, the present invention provides a differential protection method for a low-frequency power transmission line, including:
collecting the current of a low-frequency power transmission line;
taking R at current 1 A current sampling point, if R 1 S is accumulated in each current sampling point 1 If the current value of each current sampling point is greater than a preset first threshold value, a first criterion is established;
respectively taking continuous current sampling points on the positive and negative half cycles of the current, and if S is continuously present in the current sampling points 2 If the current value of each current sampling point is larger than a preset second threshold value, a second criterion is established;
taking R between two zero crossings of the current 3 A current sampling point, if R 3 In each current sampling point, S is continuously present 3 The current value of each current sampling point is greater than the preset valueIf the first threshold value is reached, the third criterion is met;
obtaining a current sampling point on the current, and if the current value of the current sampling point is greater than the conventional steady-state quantity differential current and a low-ratio braking action threshold, determining that the fourth criterion is satisfied;
and if at least one of the first criterion, the second criterion and the third criterion is true and the fourth criterion is true, performing differential protection action.
Optionally, the number of current sampling points S 1 >N/4, wherein N is the number of sampling points of the next current cycle with rated low-frequency; the number of current sampling points R 1 ≥S 1 +2。
Optionally, the number of current sampling points S 3 N is more than or equal to N/10, wherein N is the number of sampling points of the next current cycle under the rated low-frequency; the number S of current sampling points 3 And R 3 Satisfies the following conditions: s 3 /R 3 ≥50％。
Optionally, the current values of the current sampling points in the first criterion, the second criterion, the third criterion and the fourth criterion are all i d ＝|i m +i n |，i m 、i n Current values of current sampling points on the side and the opposite side are respectively; the conventional steady-state quantity differential current is 0.15i r ，i r ＝|i m -i n |。
In a second aspect, the present invention provides a differential protection system for a low-frequency power transmission line, including:
the current acquisition module is used for acquiring the current of the low-frequency power transmission line;
criterion one module for taking R on current 1 A current sampling point, if R 1 S is accumulated in each current sampling point 1 If the current value of each current sampling point is greater than a preset first threshold value, a first criterion is established;
a second criterion module for respectively sampling continuous current sampling points on the positive and negative half cycles of the current, if there is S in the current sampling points continuously 2 If the current value of each current sampling point is larger than a preset second threshold value, a second criterion is established;
three criterion modules for two zero-crossing points of currentGet R between 3 A current sampling point, if R 3 In each current sampling point, S is continuously present 3 If the current value of each current sampling point is greater than a preset first threshold value, a third criterion is satisfied;
the fourth criterion module is used for obtaining a current sampling point on the current, and if the current value of the current sampling point is larger than the conventional steady-state quantity differential current and a low-ratio braking action threshold, the fourth criterion is established;
and the differential protection module is used for performing differential protection action if at least one of the first criterion, the second criterion and the third criterion is true and the fourth criterion is true.
Optionally, the number of current sampling points S 1 >N/4, wherein N is the number of sampling points of the next current cycle at the rated low-frequency; the number of current sampling points R 1 ≥S 1 +2。
Optionally, the number of current sampling points S 3 N is more than or equal to N/10, wherein N is the number of sampling points of the next current cycle under the rated low-frequency; the number S of current sampling points 3 And R 3 Satisfies the following conditions: s 3 /R 3 ≥50％。
Optionally, the current values of the current sampling points in the first criterion, the second criterion, the third criterion and the fourth criterion are all i d ＝|i m +i n |，i m 、i n Current values of current sampling points on the side and the opposite side are respectively; the conventional steady-state quantity differential current is 0.15i r ，i r ＝|i m -i n |。
In a third aspect, the present invention provides a differential protection device for a low-frequency power transmission line, including a processor and a storage medium;
the storage medium is used for storing instructions;
the processor is configured to operate in accordance with the instructions to perform the steps according to the above-described method.
In a fourth aspect, the invention provides a computer-readable storage medium having stored thereon a computer program which, when executed by a processor, performs the steps of the above-described method.
Compared with the prior art, the invention has the following beneficial effects:
the invention provides a differential protection method, a differential protection system, a differential protection device and a storage medium of a low-frequency power transmission line, aiming at the problem of abnormal differential protection action of the low-frequency power transmission line, differential protection criteria are constructed based on the sampling value differential principle, wherein one criterion is a classic sampling point differential criterion and is suitable for a relatively standard low-frequency sine wave current waveform; the second criterion is that the characteristic setting of sampling points with larger continuous amplitude of fault current before the adjustment of the electronic device is utilized, and the sensitivity to the intra-area attribute fault is higher; the third criterion is that the problem of frequency offset can be solved by utilizing the condition that two zero-crossing points directly and continuously meet a threshold; the criterion is four, the conventional low-ratio differential action based on the amplitude is adopted as the condition for checking the three criteria, so that the malfunction is avoided when the outside fault occurs, and the sensitivity of the inside fault is also ensured; in conclusion, the present invention can ensure the rapid and correct operation of the differential protection.
Drawings
Fig. 1 is a flowchart of a differential protection method for a low-frequency power transmission line according to an embodiment of the present invention;
fig. 2 is a schematic diagram of a typical double-ended power transmission line according to a first embodiment of the present invention;
fig. 3 is a schematic diagram of a low-frequency power transmission system model based on an M3C frequency converter according to an embodiment of the present invention;
fig. 4 is a schematic diagram of current sampling and differential current at two ends of a three-phase short circuit in a circuit according to an embodiment of the present invention;
FIG. 5 is a schematic diagram illustrating an operation condition of a midpoint three-phase short circuit differential criterion of the line according to an embodiment of the present invention;
FIG. 6 is a schematic diagram of current sampling and difference current at two ends of a circuit midpoint A connected to ground according to an embodiment of the present invention;
FIG. 7 is a schematic diagram illustrating a differential criterion operation of a line midpoint A to ground according to an embodiment of the present invention;
fig. 8 is a schematic diagram of current sampling and differential current at two ends of a phase-to-ground outside a circuit area according to an embodiment of the present invention;
fig. 9 is a schematic diagram illustrating an operation of the out-of-line a-phase-to-ground differential criterion according to an embodiment of the present invention.
Detailed Description
The invention is further described below with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present invention is not limited thereby.
The first embodiment is as follows:
as shown in fig. 1, an embodiment of the present invention provides a differential protection method for a low-frequency power transmission line, including:
1. and collecting the current of the low-frequency power transmission line.
2. Taking R at current 1 A current sampling point, if R 1 S is accumulated in each current sampling point 1 If the current value of each current sampling point is greater than a preset first threshold value, a first criterion is established;
the judgment of each current sampling point is as follows:
i d >i set1
as shown in FIG. 2, i d Current value for current sample point:
i d ＝|i m +i n |
i m 、i n current values of current sampling points on the side and the opposite side are respectively; i.e. i set1 Is a preset first threshold value;
simultaneously, the requirements are satisfied:
number of current sampling points S 1 >N/4, wherein N is the number of sampling points of the next current cycle at the rated low-frequency; number of current sampling points R 1 ≥S 1 +2。
3. Respectively taking continuous current sampling points on the positive and negative half cycles of the current, and if S is continuously present in the current sampling points 2 If the current value of each current sampling point is larger than a preset second threshold value, a second criterion is established;
the judgment of each current sampling point is as follows:
i d >i set2
i set2 is a predetermined second threshold value.
4. At two zero crossings of the currentGet R between 3 A current sampling point, if R 3 In each current sampling point, S is continuously present 3 If the current value of each current sampling point is greater than a preset first threshold value, a third criterion is satisfied;
the judgment of each current sampling point is as follows:
i d >i set1
simultaneously, the requirements are satisfied:
number of current sampling points S 3 N is more than or equal to N/10, wherein N is the number of sampling points of the next current cycle under the rated low-frequency; number of current sampling points S 3 And R 3 Satisfies the following conditions: s 3 /R 3 ≥50％。
5. Obtaining a current sampling point on the current, and if the current value of the current sampling point is greater than the conventional steady-state quantity differential current and a low-ratio braking action threshold, determining that the fourth criterion is satisfied;
the judgment of each current sampling point is as follows:
i r for braking current, i r ＝|i m -i n |；i set3 Is a predetermined third threshold value.
6. And if at least one of the first criterion, the second criterion and the third criterion is established and the fourth criterion is established, performing differential protection action.
When the computer executes the differential protection method for the low-frequency transmission line provided by the embodiment, the process is as follows:
(1) collecting the current of a low-frequency power transmission line;
(2) judging whether a preset first type criterion and a preset second type criterion are both established, and if so, performing differential protection action;
the first type of criterion comprises a first criterion, a second criterion and/or a third criterion, and if any criterion in the first type of criterion is established, the first type of criterion is established; the conditions for establishment include:
taking R as a current 1 A current sampling point, if R 1 S is accumulated in each current sampling point 1 If the current value of each current sampling point is greater than a preset first threshold value, judging that the first criterion is satisfied;
respectively taking continuous current sampling points on the positive and negative half cycles of the current, and if S is continuously present in the current sampling points 2 If the current value of each current sampling point is larger than a preset second threshold value, a second criterion is established;
taking R between two zero crossings of the current 3 A current sampling point, if R 3 In each current sampling point, S is continuously present 3 If the current value of each current sampling point is larger than a preset first threshold value, a third criterion is satisfied;
the second type of criterion comprises a fourth criterion, and if the fourth criterion is satisfied, the second type of criterion is satisfied; the conditions for establishment include:
and taking a current sampling point on the current, and if the current value of the current sampling point is greater than the conventional steady-state quantity differential current and a low-ratio braking action threshold, determining that the fourth criterion is satisfied.
In combination with the contents of the above method, the following simulation examples are provided for a certain low frequency power transmission system model:
a low-frequency power transmission system model based on an M3C frequency converter and shown in figure 3 is built by utilizing RTDS, the length of a protected low-frequency line is 13.2km, the rated frequency is 20Hz, and element and line parameters are shown in tables 1 and 2.
TABLE 1 simulation System component parameters
TABLE 2 simulation System line parameters
Suppose the sampling rate of the electrical quantity at two ends of the low-frequency line is 1200Hz, N is 60; criterion one middle S 1 Is taken as value of 12, i set1 Is 686A; continuous current sampling point R in criterion two 2 Is 60, S 2 Is 30, i set2 Is 600A. And respectively setting a fault point at the head end, the middle point and the tail end of the low-frequency line of the simulation model, namely F1-F3 points in the graph 3, and respectively calculating the satisfied condition of the protection criterion when the ABC three-phase short circuit occurs at each fault point. Due to the similar characteristics, only the phase A at the F2 point fault is selected as the reference phase for analysis, the simulation result is shown in the figures 4-5, and the action time is shown in the table 3.
From fig. 5, it can be seen that the differential protection principle given herein in combination with sampled values can all function correctly. The first criterion is that the action characteristic is better because the amplitude of the fault current in the first half cycle is relatively larger; the second criterion is that the fault current shows a decreasing trend, and sampling points of the second half cycle which are larger than the threshold value are fewer and cannot be better satisfied; the third criterion can identify faults under different working conditions due to the self-adaptive characteristic of the third criterion, and has better action characteristic; the steady-state quantity difference flow threshold and the low-ratio braking equation are used as a gating condition, and the fault working condition can be correctly identified.
TABLE 3 Intra-zone symmetry failure behavior case
In order to research the application condition of a new differential protection criterion when an asymmetric fault occurs in a low-frequency line area, a fault point is respectively arranged at the head end, the middle point and the tail end of a low-frequency line of a simulation model, and the meeting condition of the protection criterion when an A-phase grounding fault occurs at each fault point is respectively calculated. The fault phase when the F2 point is in fault is selected for analysis, and simulation results are shown in figures 6-7.
As can be taken from fig. 6 and 7, the differential protection principle presented herein in combination with sampled values also works correctly after a fault has occurred. The action time is shown in table 4.
TABLE 4 asymmetric Fault behavior in zone
In order to research the application condition of the new criterion of the dynamic protection when a fault occurs outside a low-frequency line area, a fault point is respectively arranged at a low-frequency line F4 of a simulation model, and the meeting condition of the protection criterion when a single-phase earth fault occurs at each fault point is respectively calculated. The fault phase is selected for analysis, and the simulation result is shown in figures 8 and 9.
As is clear from fig. 8 and 9, when a fault occurs outside the low-frequency line region, the differential protection is not reliably operated because there is no difference current in each phase.
Example two:
the invention provides a differential protection system of a low-frequency power transmission line, which comprises:
the current acquisition module is used for acquiring the current of the low-frequency power transmission line;
criterion one module for taking R on current 1 A current sampling point, if R 1 S is accumulated in each current sampling point 1 If the current value of each current sampling point is greater than a preset first threshold value, a first criterion is established;
a second criterion module for respectively sampling continuous current sampling points on the positive and negative half cycles of the current, if there is S in the current sampling points continuously 2 If the current value of each current sampling point is larger than a preset second threshold value, a second criterion is established;
a criterion three-module for taking R between two zero-crossing points of current 3 A current sampling point, if R 3 In each current sampling point, S is continuously present 3 If the current value of each current sampling point is larger than a preset first threshold value, a third criterion is satisfied;
the fourth criterion module is used for obtaining a current sampling point on the current, and if the current value of the current sampling point is larger than the conventional steady-state quantity differential current and a low-ratio braking action threshold, the fourth criterion is established;
and the differential protection module is used for performing differential protection action if at least one of the first criterion, the second criterion and the third criterion is true and the fourth criterion is true.
Specifically, the method comprises the following steps:
number of current sampling points S 1 >N/4, wherein N is the number of sampling points of the next current cycle with rated low-frequency; number of current sampling points R 1 ≥S 1 +2。
Number of current sampling points S 3 N is more than or equal to N/10, wherein N is the number of sampling points of the next current cycle under the rated low-frequency; number of current sampling points S 3 And R 3 Satisfies the following conditions: s 3 /R 3 ≥50％。
The current values of the current sampling points in the first criterion, the second criterion, the third criterion and the fourth criterion are all i d ＝|i m +i n |，i m 、i n Current values of current sampling points on the side and the opposite side are respectively; the conventional steady-state quantity differential current is 0.15i r ，i r ＝|i m -i n |。
Example three:
based on the first embodiment, the invention provides a differential protection device of a low-frequency power transmission line, which comprises a processor and a storage medium, wherein the processor is used for processing the low-frequency power transmission line;
a storage medium to store instructions;
the processor is configured to operate in accordance with instructions to perform steps in accordance with the above-described method.
Example four:
in accordance with an implementation, the invention provides a computer-readable storage medium, on which a computer program is stored which, when being executed by a processor, carries out the steps of the above-mentioned method.
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 described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows 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 it should be noted that, for those skilled in the art, several modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.
Claims (10)
1. A differential protection method of a low-frequency power transmission line is characterized by comprising the following steps:
collecting the current of a low-frequency power transmission line;
taking R at current 1 A current sampling point, if R 1 S is accumulated in each current sampling point 1 If the current value of each current sampling point is greater than a preset first threshold value, a first criterion is established;
respectively taking continuous current sampling points on the positive and negative half cycles of the current, and if S is continuously present in the current sampling points 2 If the current value of each current sampling point is greater than a preset second threshold value, a second criterion is established;
taking R between two zero crossings of the current 3 A current sampling point, if R 3 In each current sampling point, S is continuously present 3 If the current value of each current sampling point is larger than a preset first threshold value, a third criterion is satisfied;
obtaining a current sampling point on the current, and if the current value of the current sampling point is greater than the conventional steady-state quantity differential current and a low-ratio braking action threshold, determining that the fourth criterion is satisfied;
and if at least one of the first criterion, the second criterion and the third criterion is true and the fourth criterion is true, performing differential protection action.
2. The differential protection method for low-frequency transmission line according to claim 1, characterized in that the number of current sampling points S 1 >N/4, wherein N is the number of sampling points of the next current cycle with rated low-frequency; the number of current sampling points R 1 ≥S 1 +2。
3. The differential protection method for low-frequency transmission line according to claim 1, characterized in that the number of current sampling points S 3 N is more than or equal to N/10, wherein N is the number of sampling points of the next current cycle under the rated low-frequency; the number S of current sampling points 3 And R 3 Satisfies the following conditions: s 3 /R 3 ≥50％。
4. The differential protection method of the low-frequency transmission line according to claim 1, wherein current values of current sampling points in the first criterion, the second criterion, the third criterion and the fourth criterion are all i d ＝|i m +i n |，i m 、i n Current values of current sampling points on the side and the opposite side are respectively; the conventional steady-state quantity differential current is 0.15i r ，i r ＝|i m -i n |。
5. A differential protection system of a low-frequency power transmission line is characterized by comprising:
the current acquisition module is used for acquiring the current of the low-frequency power transmission line;
criterion one module for taking R on current 1 A current sampling point, if R 1 S is accumulated in each current sampling point 1 If the current value of each current sampling point is greater than a preset first threshold value, a first criterion is established;
a second criterion module for respectively sampling continuous current sampling points on the positive and negative half cycles of the current, if there is S in the current sampling points continuously 2 If the current value of each current sampling point is larger than a preset second threshold value, a second criterion is established;
a criterion three-module for taking R between two zero-crossing points of current 3 A current sampling point, if R 3 In each current sampling point, S is continuously present 3 If the current value of each current sampling point is larger than a preset first threshold value, a third criterion is satisfied;
the fourth criterion module is used for obtaining a current sampling point on the current, and if the current value of the current sampling point is larger than the conventional steady-state quantity differential current and a low-ratio braking action threshold, the fourth criterion is established;
and the differential protection module is used for performing differential protection action if at least one of the first criterion, the second criterion and the third criterion is true and the fourth criterion is true.
6. The differential protection system for low-frequency power transmission line according to claim 5, wherein the number of current sampling points S 1 >N/4, wherein N is the number of sampling points of the next current cycle with rated low-frequency; the number of current sampling points R 1 ≥S 1 +2。
7. The differential protection system for low-frequency power transmission line according to claim 5, wherein the number of current sampling points S 3 N is more than or equal to N/10, wherein N is the number of sampling points of the next current cycle under the rated low-frequency; the number S of current sampling points 3 And R 3 Satisfies the following conditions: s 3 /R 3 ≥50％。
8. The differential protection system of the low-frequency power transmission line according to claim 5, wherein current values of current sampling points in the first criterion, the second criterion, the third criterion and the fourth criterion are all i d ＝|i m +i n |，i m 、i n Current values of current sampling points on the side and the opposite side are respectively; the conventional steady-state quantity differential current is 0.15i r ，i r ＝|i m -i n |。
9. The differential protection device of the low-frequency transmission line is characterized by comprising a processor and a storage medium;
the storage medium is used for storing instructions;
the processor is configured to operate in accordance with the instructions to perform the steps of the method according to any one of claims 1 to 4.
10. Computer-readable storage medium, on which a computer program is stored which, when being executed by a processor, carries out the steps of the method according to any one of claims 1 to 4.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210818059.6A CN115085163A (en) | 2022-07-13 | 2022-07-13 | Differential protection method, system and device for low-frequency power transmission line and storage medium |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
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| CN202210818059.6A CN115085163A (en) | 2022-07-13 | 2022-07-13 | Differential protection method, system and device for low-frequency power transmission line and storage medium |
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| CN116683411A (en) * | 2023-08-01 | 2023-09-01 | 华北电力大学 | Alternating current line protection method and system and electronic equipment |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN116683411A (en) * | 2023-08-01 | 2023-09-01 | 华北电力大学 | Alternating current line protection method and system and electronic equipment |
| CN116683411B (en) * | 2023-08-01 | 2023-09-29 | 华北电力大学 | Alternating current line protection method and system and electronic equipment |
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