Zero-sequence inverse time limit over-current protection optimization method and system for power transmission line

Abstract

The invention discloses a zero-sequence inverse time limit overcurrent protection optimization method and system for a power transmission line, and the method comprises the steps: collecting and calculating the zero-sequence voltage and zero-sequence current of a local side and an opposite side of the line, and reversely deducing the zero-sequence voltage of the opposite side in combination with the zero-sequence impedance of the line. Zero-sequence inverse-time-limit acceleration is realized when a backstepping and actually-measured opposite-side zero-sequence voltage difference is relatively large, and acceleration is not performed when backstepping and actually-measured opposite-side zero-sequence voltages are consistent. And in zero-sequence inverse time limit acceleration, the maximum branch coefficients of other branches outside the fault line are considered to improve the acceleration speed. And after the zero-sequence inverse time limit is subjected to acceleration triggering, the minimum action time in zero-sequence inverse time limit logic is shortened, and meanwhile, the zero-sequence inverse time limit calculation time and the matching time are changed into OR, so that override action caused by relatively large zero-sequence current of other branches is avoided. According to the invention, the action speed of zero-sequence inverse time-lag protection during grounding and disconnection faults in the area can be accelerated, the self selectivity is improved, other branches are prevented from surpassing maloperation, and the action performance of zero-sequence inverse time-lag protection is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of relay protection, and relates to a method and system for optimizing zero-sequence inverse time overcurrent protection of a transmission line. Background Art

[0002] The action time of inverse-time current protection is inversely proportional to the current size. It has a natural coordination ability between the upper and lower levels in the power grid. It is a consensus in the relay protection industry to use inverse-time zero-sequence current protection to replace the current definite-time zero-sequence protection and effectively cooperate with other protections to build a new backup protection system. Research and promotion of zero-sequence current inverse-time protection is the key development direction of relay protection, and the use of inverse-time zero-sequence current curves with the same characteristics throughout the network is promoted. By moving the action curve horizontally, the coordination of zero-sequence current protection of lines at all levels of the power grid can be well achieved, which can effectively improve the overall performance of backup protection. Therefore, systematic research on inverse-time zero-sequence current and its widespread application in power grids above 220kV will greatly improve the backup protection performance of large power grids, which is of great significance to ensuring the safe and stable operation of new power systems.

[0003] At present, there are some theoretical studies and explorations on the application of inverse time zero-sequence current protection in large power grids, and some applications have been realized in 500kV power grids. However, the zero-sequence current distribution characteristics across voltage levels after a ground fault in a large power grid are affected by the complex topology of the power grid, complex fault scenarios, and the successive actions of protection, making the existing zero-sequence protection principle and coordination strategy still insufficiently adaptable.

[0004] Prior patent application CN201611061205.6 discloses a method for optimizing zero-sequence inverse time overcurrent protection, which is characterized by comprising the following steps: Step 1, collecting the voltages of phase A, phase B, and phase C at the protection installation location, and calculating the zero-sequence voltage and current. Step 2, judging according to the following criteria one, two, three, and four; Step 3, determining the acceleration coefficient A according to the judgment results of criteria one, two, three, and four; Step 4, adding the acceleration coefficient A to the zero-sequence inverse time characteristic equation time, and optimizing the zero-sequence inverse time action time t(3I0). The algorithm is simple, has good selectivity, and improves the protection action speed, which can ensure and improve the reliability and selectivity of the zero-sequence inverse time overcurrent protection.

[0005] However, the above patent solution is for the application scenario of connecting a single-circuit line to a double-circuit line. When the fault line needs to be accelerated, the adjacent line at the previous level also needs to be accelerated to change the calculation time of the inverse time zero-sequence curve for acceleration. The acceleration factor is determined based on the action range of the high-resistance distance, that is, the zero-sequence current at the determined fault point location, rather than the concept of the maximum branch coefficient of the power system. In this patent solution, the acceleration is determined in combination with the high-resistance distance, which can only adapt to the double-circuit transmission mode, and it may cause the zero-sequence inverse time calculation time to be less than the coordination time.

[0006] The prior patent application CN202211586027.4 discloses a method for setting a zero-sequence inverse time overcurrent protection setting for an ultra-ultra-high voltage AC line, comprising: determining a zero-sequence inverse time current setting while ensuring sensitivity during a high-resistance grounding fault in the line; determining a zero-sequence inverse time setting according to the line high-resistance grounding fault removal time requirement and the fault current change action time gradient requirement; calculating the minimum tolerable zero-sequence current for each line grounding distance III protection in the entire network, taking the maximum value of the minimum tolerable zero-sequence current for all lines in the entire network, and determining the minimum turning current of the zero-sequence inverse time protection; determining a coordination time setting according to the set zero-sequence inverse current setting, the zero-sequence inverse time setting, and the minimum turning current; determining the minimum time setting for the zero-sequence inverse time overcurrent protection according to the three-phase inconsistency protection action time, the reclosing time, the grounding distance protection last-stage action time, and the coordination time setting.

[0007] However, the patent is an application of the setting principle of the previous zero-sequence inverse time scheme, which is mainly a universal setting method, such as how to choose the coordination time and how to set the minimum action time. The above patent scheme lacks the determination of faults inside and outside the line area, and does not propose the acceleration and setting coordination scheme of the zero-sequence inverse time characteristic when a fault occurs.

[0008] In recent years, the problem of zero-sequence inverse time overcurrent protection without selective action and slow action has become increasingly prominent. Many of them are achieved by adjusting the fixed value, but this leads to the coordination and setting problems of other fixed values. This solution cannot fundamentally solve the problem of zero-sequence inverse time without selectivity and action satisfaction. Summary of the invention

[0009] In view of the above problems, the present invention provides a method for optimizing zero-sequence inverse time overcurrent protection for power transmission lines. The algorithm is simple, and the zero-sequence inverse time overcurrent protection can be accelerated, thereby ensuring and improving the selectivity and speed of the zero-sequence inverse time overcurrent protection.

[0010] In order to achieve the above technical objectives, the present invention is implemented through the following technical solutions:

[0011] The present invention discloses, on one hand, a method for optimizing zero-sequence inverse time overcurrent protection of a transmission line, which is characterized by comprising the following contents:

[0012] Collect the three-phase voltage and three-phase current at the line protection installation site to obtain the zero-sequence voltage on the local side of the line protection installation site and zero sequence current

[0013] Receive the three-phase voltage and three-phase current on the opposite side of the line through the line protection optical fiber channel to obtain the zero-sequence voltage on the opposite side of the line and zero sequence current

[0014] Combined with the zero-sequence reactance of the line and zero sequence current on this side Reverse the calculation to obtain the zero-sequence voltage on the opposite side.

[0015] Calculate the zero-sequence voltage on the opposite side The zero-sequence voltage on the opposite side reversed from the current side The difference dU0,

[0016] According to the size of dU0, adaptive zero-sequence inverse time acceleration and non-acceleration are realized. When dU0 is greater than the set deviation threshold U set When dU0 is not greater than the set deviation threshold U set When the zero-sequence inverse time protection meets the action criterion, the zero-sequence inverse time protection does not accelerate.

[0017] More preferably,

[0018] Opposite zero sequence voltage and zero sequence voltage on this side All are measured values ​​or actual values ​​calculated through the three-phase voltage on the corresponding side.

[0019] More preferably,

[0020] The reverse zero-sequence voltage on the opposite side is obtained by reverse calculation from the line side according to the following formula:

[0021]

[0022] in, is the zero-sequence reactance of the line.

[0023] More preferably,

[0024] Deviation threshold U set The sensitivity and related calculation errors during short circuit and line break faults need to be considered.

[0025] More preferably,

[0026] Deviation threshold U set The value is obtained by the following formula:

[0027]

[0028] Where, dU 0f is the fault deviation voltage value in the zone, is the zero-sequence voltage on the opposite side, It is the zero-sequence voltage on the opposite side inferred from this side.

[0029] More preferably,

[0030] When dU0 is greater than the set deviation threshold U set When the zero-sequence inverse time protection meets the action criterion, the zero-sequence inverse time protection is accelerated in the following manner:

[0031] After the zero-sequence inverse time is accelerated and triggered, the acceleration coefficient kb is calculated in combination with the maximum branch coefficient and reliability coefficient of the line. When kb is greater than 1, the fault zero-sequence current is amplified and accelerated, otherwise it is not amplified and accelerated;

[0032] When amplifying acceleration, adjust the zero-sequence inverse time acceleration calculation time to:

[0033]

[0034] 3I0 is the zero sequence current at the protection installation location, corresponding to the protection of the line side The modulus value of I set is the zero-sequence inverse time overcurrent protection starting setting, T P It is the zero-sequence inverse time constant setting, which is adjusted according to the overall zero-sequence inverse time action time requirements.

[0035] More preferably,

[0036] The value of the acceleration factor kb is determined by the following formula:

[0037]

[0038] More preferably,

[0039] When the voltage difference dU0 is not greater than the set deviation threshold, when the zero-sequence current If the zero-sequence inverse time protection meets the action criterion, it is considered that an out-of-zone positive direction fault has occurred. The zero-sequence inverse time protection cannot be accelerated and the zero-sequence inverse time protection needs to be used as a remote backup protection for the zero-sequence inverse time overcurrent protection of other adjacent lines.

[0040] More preferably,

[0041] The zero-sequence inverse time protection action criteria are as follows:

[0042]

[0043] In the formula, I set It is the zero-sequence current starting setting of zero-sequence inverse time protection.

[0044] More preferably,

[0045] When dU0 is greater than the set deviation threshold U set When the zero-sequence inverse time protection meets the action criterion, the zero-sequence inverse time protection is accelerated in the following manner:

[0046] After the zero-sequence inverse time limit is accelerated and triggered, the zero-sequence inverse time limit acceleration calculation time is shortened, and at the same time, the "AND" logical relationship between "zero-sequence inverse time limit calculation time" and "zero-sequence inverse time limit coordination time" is accelerated to the "OR" logical relationship between "shortening the zero-sequence inverse time limit acceleration calculation time" and "zero-sequence inverse time limit coordination time".

[0047] More preferably,

[0048] The reduced zero-sequence inverse time acceleration calculation time is calculated according to the following formula:

[0049]

[0050] 3I0 is the zero sequence current at the protection installation location, corresponding to the protection of the line side The modulus value of I set is the zero-sequence inverse time overcurrent protection starting setting, T P is the zero-sequence inverse time constant setting, which is adjusted according to the overall zero-sequence inverse time action time requirement. kb is the acceleration coefficient calculated by the maximum branch coefficient and reliability coefficient of this line.

[0051] On the other hand, the present invention discloses a transmission line zero-sequence inverse time overcurrent protection optimization system based on the zero-sequence inverse time overcurrent protection optimization method, comprising a signal acquisition module, an opposite side zero-sequence voltage reverse calculation module, a zero-sequence inverse time protection judgment module, a zero-sequence inverse time acceleration judgment module and a zero-sequence inverse time acceleration module; characterized in that:

[0052] The signal acquisition module includes a signal acquisition unit on the line side and a signal acquisition unit on the opposite side of the line, which respectively collect the three-phase voltage and three-phase current at the protection installation on the line side and the three-phase voltage and three-phase current on the opposite side of the line; obtain the zero-sequence voltage on the line side and zero sequence current Opposite zero sequence voltage and zero sequence current

[0053]

[0054] Opposite zero-sequence voltage reverse calculation module Line zero-sequence reactance and zero sequence current on this side Reverse the calculation to obtain the zero-sequence voltage on the opposite side.

[0055] The zero-sequence inverse time protection judgment module is based on the zero-sequence current on this side. Compare with the zero-sequence current starting setting of the inverse time protection to determine whether the zero-sequence inverse time protection action criterion is met;

[0056] The zero-sequence inverse time acceleration judgment module calculates the opposite zero-sequence voltage The zero-sequence voltage on the opposite side reversed from the current side The difference dU0 is realized according to the size of dU0, and adaptive zero-sequence inverse time acceleration and non-acceleration are realized. When dU0 is greater than the set deviation threshold U set When dU0 is not greater than the set deviation threshold U set When the zero-sequence inverse time protection meets the action criterion, the zero-sequence inverse time protection does not accelerate.

[0057] Compared with the prior art, the present invention has the following beneficial technical effects.

[0058] The present invention proposes to use the current zero-sequence voltage to infer the opposite zero-sequence voltage, and determine whether it is an internal or external fault of the line area through the difference, and can solve the application of line zero-sequence inverse time protection in the event of ground fault and longitudinal fault.

[0059] The present invention determines two acceleration modes when there is a fault in the area. Through the distribution of zero-sequence current in the station, when there is a branch zero-sequence current greater than the main line, the fault zero-sequence current is amplified in combination with the branch coefficient, and the zero-sequence inverse time calculation time is short, realizing the acceleration of the calculation time of the inverse time curve, which is suitable for multi-circuit transmission mode, and the adjacent upper-level lines do not need to be accelerated; after the calculation time is accelerated, the coordination time may be large and fail to achieve the purpose of acceleration, so the AND gate with the coordination time is changed to an OR gate; the minimum action time is shortened and then accelerated to avoid the zero-sequence inverse time calculation time being less than the coordination time. The present invention adjusts the zero-sequence inverse time action characteristic to coordination time + shortened minimum action time to ensure that the fault line acts in advance and achieves acceleration.

[0060] The present invention can avoid malfunction due to the influence of zero-sequence current distribution in the zone causing other branches to be greater than the zero-sequence current of the fault line. The algorithm is simple and can reliably operate and accelerate the removal when a positive direction zone grounding fault or zone disconnection fault occurs in a certain loop of the transmission line, thereby improving selectivity and speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 It is a schematic diagram of Embodiment 1 of a method for optimizing zero-sequence inverse time overcurrent protection for a power transmission line according to the present invention;

[0062] Figure 2 It is a schematic diagram of Embodiment 2 of a method for optimizing zero-sequence inverse time overcurrent protection for a transmission line according to the present invention;

[0063] Figure 3 It is a line fault diagram;

[0064] Figure 4 It is the zero-sequence component sequence network diagram of line fault. DETAILED DESCRIPTION

[0066] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The embodiments described in this application are only embodiments of a part of the present invention, rather than all embodiments. Based on the spirit of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the protection scope of the present invention.

[0067] A method for optimizing zero-sequence inverse time overcurrent protection of a transmission line comprises the following steps:

[0068] exist Figure 2 In the simulation of the ground fault of the transmission line, the percentage of the protection distance fault point in the total length is α.

[0069] Step 1: Collect the three-phase voltage and three-phase current at the line protection installation location, and calculate the zero-sequence voltage and zero-sequence current of the loop respectively.

[0070] The calculated protection zero-sequence voltage and zero-sequence current are:

[0071]

[0072] Step 2: Receive the three-phase voltage and three-phase current on the opposite side of the line through the line protection optical fiber channel, and calculate the zero-sequence voltage and zero-sequence current of the loop respectively.

[0073] The opposite side zero-sequence voltage and zero-sequence current are calculated based on the received opposite side data:

[0074]

[0075] Step 3: Combine the zero-sequence reactance of the line and zero sequence Reverse the zero-sequence voltage on the opposite side of the line.

[0076]

[0077] Step 4: Calculate the zero-sequence voltage on the opposite side Reverse push from this side The difference dU0,

[0078]

[0079] Combination Figure 2 , 3 For example, for protection 1, the zero-sequence voltage on the opposite side of the line is:

[0080]

[0081] The reverse zero-sequence voltage is

[0082]

[0083] The difference dU0 is:

[0084]

[0085] The difference is related to the fault point, fault line and the equivalent reactance of the systems on both sides. Theoretically, there is a difference when there is an internal fault, and it is theoretically 0 when there is an external fault. The same is true for line break faults.

[0086] Step 5: Adaptive zero-sequence inverse time acceleration and non-acceleration are realized according to the size of dU0. When dU0 is greater than the set deviation threshold U set When dU0 is not greater than the set deviation threshold U set When the zero-sequence inverse time protection meets the action criterion, the zero-sequence inverse time protection does not accelerate.

[0087] The present invention adopts two methods to perform zero-sequence inverse time acceleration, which are shown in Embodiment 1 and Embodiment 2 respectively.

[0088] Embodiment 1:

[0089] As attached Figure 1 As shown, a method for optimizing zero-sequence inverse time overcurrent protection of a transmission line comprises the following steps:

[0090] Step 1: Collect the three-phase voltage and three-phase current at the line protection installation location, and calculate the zero-sequence voltage and zero-sequence current of the loop respectively. The calculated protection zero-sequence voltage and zero-sequence current are:

[0091]

[0092] The modulus value 3I 10 With zero sequence inverse time starting setting I set By comparison, if it is greater than the starting setting, it is considered that the zero-sequence inverse time protection meets the action criterion. Step 2: Receive the three-phase voltage and three-phase current on the opposite side of the line through the line protection optical fiber channel, and calculate the zero-sequence voltage of this loop as The opposite side zero sequence voltage is calculated based on the received opposite side data:

[0093]

[0094] Step 3: Combine the zero-sequence reactance of the line and zero sequence Reverse the zero-sequence voltage on the opposite side of the line

[0095] Step 4: Calculate the zero-sequence voltage on the opposite side Reverse push from this side The difference dU0,

[0096]

[0097] Step 5: Compare the difference dU0 with the deviation threshold U set Compare,

[0098] When dU0>U set And 3I 10 >I set If the zero-sequence inverse time calculation acceleration calculation time condition is met, the inverse time action time acceleration calculation is performed, such as Figure 1 As shown, the zero sequence inverse time calculation time curve is from

[0099] becomes:

[0100]

[0101] 3I0 is the zero sequence current at the protection installation location, corresponding to the protection of the line side The modulus value of I set is the zero-sequence inverse time overcurrent protection starting setting, T P It is the zero-sequence inverse time constant setting, which is adjusted according to the overall zero-sequence inverse time action time requirements.

[0102] When dU0<U set And 3I 10 >I set If the zero-sequence inverse time calculation acceleration conditions are not met, the calculation time will not be accelerated.

[0103] If one of them is satisfied, the zero-sequence inverse time calculation time is satisfied, and the subsequent zero-sequence inverse time action logic comparison is entered.

[0104] Combination Figure 3 , 4 For example, assuming that the deviation threshold is 0V, the fault dU0 in the zone is always greater than 0. For the sake of reliability, the deviation threshold has a certain reliability. It is selected in combination with the extreme value of the difference of the fault in the zone and the successive quick action of the near and far ends.

[0105] In this embodiment, the deviation threshold U set The value is obtained by the following formula:

[0106]

[0107] Where, dU 0f is the fault deviation voltage value in the zone, is the zero-sequence voltage on the opposite side, It is the zero-sequence voltage on the opposite side reversed from this side.

[0108] After the zero-sequence inverse time is accelerated and triggered, the acceleration coefficient kb is calculated in combination with the maximum branch coefficient and reliability coefficient of the line. When kb is greater than 1, the fault zero-sequence current is amplified and accelerated, otherwise it is not amplified and accelerated;

[0109] When amplifying acceleration, the zero-sequence inverse time overcurrent protection action time characteristic is adjusted to:

[0110]

[0111] 3I0 is the zero sequence current at the protection installation location, corresponding to the protection of the line side The modulus value of I set is the zero-sequence inverse time overcurrent protection starting setting, T P It is the zero-sequence inverse time constant setting, which is adjusted according to the overall zero-sequence inverse time action time requirements.

[0112] The value of the acceleration factor kb is determined by the following formula:

[0113]

[0114] It is preferred that kb is greater than 1. When kb is less than or equal to 1, there is no need for acceleration. Figure 2 and 3 When the zero-sequence current of other branches on the M side is greater than the fault line, the kb value is the maximum value of other branches / zero-sequence current of the fault line, so the zero-sequence calculation time of the fault line is The zero-sequence inverse time that is smaller than the calculated time of other branches realizes the accelerated action while avoiding the overtaking of the upper line fault.

[0115] Embodiment 2:

[0116] As attached Figure 2 As shown, another preferred embodiment of a method for optimizing zero-sequence inverse time overcurrent protection for a transmission line is shown, comprising the following steps:

[0117] Step 1: Collect the three-phase voltage and three-phase current at the line protection installation location, and calculate the zero-sequence voltage and zero-sequence current of the loop respectively. Calculate the protection zero-sequence voltage and zero-sequence current respectively

[0118]

[0119] The modulus value 3I 10 With zero sequence inverse time starting setting I set contrast.

[0120] Step 2: Calculate the zero-sequence voltage on the opposite side of the loop: . And combined with the zero-sequence reactance of the line and zero sequence Reverse the zero-sequence voltage on the opposite side of the line

[0121] Figure 3 Simulate the line L between station M and station N to have a fault at F1. Protection 1 is installed on the M side of the line and protection 2 is installed on the N side. After the fault occurs, the zero-sequence equivalent network is as follows: Figure 4 As shown. Combined Figure 4 Analyze the action flow and steps of protection 1.

[0122] Step 3: Calculate the zero-sequence voltage on the opposite side Reverse push from this side The difference,

[0123] With the deviation threshold U set Compare.

[0124] Step 4: When dU0>U set And 3I 10 >I set When the zero-sequence inverse time calculation acceleration calculation time condition is met, the inverse time action time acceleration calculation is performed, and the zero-sequence inverse time calculation time curve is from becomes Zero sequence inverse time action curve accelerates; when dU0<U set And 3I 10 >I set If the zero-sequence inverse time calculation acceleration conditions are not met, the calculation time will not be accelerated.

[0125] Step 5. When the acceleration condition is met, the inverse time curve calculation time and the coordination time in the zero-sequence inverse time action logic are "OR" logic. If one of them is met, the minimum action time is entered, and the minimum action time is compressed by a time difference. The time difference is generally 300-500ms. When the delay is met, the zero-sequence inverse time action exits.

[0126] Step 6. When the non-acceleration condition is met, the inverse time curve calculation time and the coordination time in the zero-sequence inverse time action logic are "AND" logic. If both conditions are met, the minimum action time delay is entered. The minimum action time is not compressed. When the delay is met, the zero-sequence inverse time action exits.

[0127] Compared with step 6, step 5 is faster and more selective.

[0128] The algorithm of the present invention is simple and can make parallel judgments, which can greatly improve the rapidity and selectivity of protection. Moreover, it can reliably and accelerate the action when a grounding fault occurs in the positive direction of the transmission line, and will not accelerate and ensure that it does not exceed false action when a fault occurs outside the zone, thereby improving the reliability and selectivity of the zero-sequence inverse time overcurrent protection.

[0129] The present invention also discloses a transmission line zero-sequence inverse time overcurrent protection optimization system based on the zero-sequence inverse time overcurrent protection optimization method, comprising a signal acquisition module, an opposite side zero-sequence voltage reverse calculation module, a zero-sequence inverse time protection judgment module, a zero-sequence inverse time acceleration judgment module and a zero-sequence inverse time acceleration module.

[0130] The signal acquisition module includes a signal acquisition unit on the line side and a signal acquisition unit on the opposite side of the line, which respectively collect the three-phase voltage and three-phase current at the protection installation on the line side and the three-phase voltage and three-phase current on the opposite side of the line; obtain the zero-sequence voltage on the line side and zero sequence current , Opposite zero sequence voltage and zero sequence current

[0131]

[0132] Opposite zero-sequence voltage reverse calculation module Line zero-sequence reactance and zero sequence current on this side Reverse the calculation to obtain the zero-sequence voltage on the opposite side.

[0133] The zero-sequence inverse time protection judgment module is based on the zero-sequence current on this side. Compare with the zero-sequence current starting setting of the inverse time protection to determine whether the zero-sequence inverse time protection action criterion is met;

[0134] The zero-sequence inverse time acceleration judgment module calculates the opposite zero-sequence voltage The zero-sequence voltage on the opposite side reversed from the current side The difference dU0 is realized according to the size of dU0, and adaptive zero-sequence inverse time acceleration and non-acceleration are realized. When dU0 is greater than the set deviation threshold U set When dU0 is not greater than the set deviation threshold U set When the zero-sequence inverse time protection meets the action criterion, the zero-sequence inverse time protection does not accelerate.

[0135] The present disclosure may be a system, a method and / or a computer program product. The computer program product may include a computer-readable storage medium carrying computer-readable program instructions for causing a processor to implement various aspects of the present disclosure.

[0136] A computer-readable storage medium may be a tangible device that can hold and store instructions used by an instruction execution device. A computer-readable storage medium may be, for example, but not limited to, an electrical storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the foregoing. More specific examples of computer-readable storage media (a non-exhaustive list) include: a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), a static random access memory (SRAM), a portable compact disk read-only memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanical encoding device, such as a punch card or a raised structure in a groove on which instructions are stored, and any suitable combination of the foregoing. As used herein, a computer-readable storage medium is not to be interpreted as a transient signal per se, such as a radio wave or other freely propagating electromagnetic wave, an electromagnetic wave propagating through a waveguide or other transmission medium (e.g., a light pulse through a fiber optic cable), or an electrical signal transmitted through a wire.

[0137] The computer-readable program instructions described herein can be downloaded from a computer-readable storage medium to each computing / processing device, or downloaded to an external computer or external storage device via a network, such as the Internet, a local area network, a wide area network, and / or a wireless network. The network can include copper transmission cables, optical fiber transmissions, wireless transmissions, routers, firewalls, switches, gateway computers, and / or edge servers. The network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards the computer-readable program instructions for storage in the computer-readable storage medium in each computing / processing device.

[0138] The computer program instructions for performing the operation of the present disclosure may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-related instructions, microcode, firmware instructions, state setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages, such as Smalltalk, C++, etc., and conventional procedural programming languages, such as "C" language or similar programming languages. Computer-readable program instructions may be executed completely on a user's computer, partially on a user's computer, as an independent software package, partially on a user's computer, partially on a remote computer, or completely on a remote computer or server. In the case of a remote computer, the remote computer may be connected to the user's computer via any type of network, including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computer (e.g., using an Internet service provider to connect via the Internet). In some embodiments, an electronic circuit, such as a programmable logic circuit, a field programmable gate array (FPGA), or a programmable logic array (PLA), may be customized by utilizing the state information of the computer-readable program instructions, and the electronic circuit may execute the computer-readable program instructions, thereby realizing various aspects of the present disclosure.

[0139] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for optimizing zero-sequence inverse time overcurrent protection for a transmission line, characterized in that: It includes the following: Collect the three-phase voltage and three-phase current at the line protection installation site to obtain the zero-sequence voltage on the local side of the line protection installation site and zero sequence current Receive the three-phase voltage and three-phase current on the opposite side of the line through the line protection optical fiber channel to obtain the zero-sequence voltage on the opposite side of the line and zero sequence current Combined with the zero-sequence reactance of the line and zero sequence current on this side Reverse the calculation to obtain the zero-sequence voltage on the opposite side. Calculate the zero-sequence voltage on the opposite side The zero-sequence voltage on the opposite side reversed from the current side The difference dU0, According to the size of dU0, adaptive zero-sequence inverse time acceleration and non-acceleration are realized. When dU0 is greater than the set deviation threshold U set When the zero-sequence inverse time protection meets the action criterion, the zero-sequence inverse time protection is accelerated; When dU0 is not greater than the set deviation threshold U set When the zero-sequence inverse time protection meets the action criterion, the zero-sequence inverse time protection does not accelerate.

2. The zero-sequence inverse time overcurrent optimization protection method according to claim 1 is characterized in that: Opposite zero sequence voltage and zero sequence voltage on this side All are measured values ​​or actual values ​​calculated through the three-phase voltage on the corresponding side.

3. The zero-sequence inverse time overcurrent optimization protection method according to claim 1 is characterized in that: The reverse zero-sequence voltage on the opposite side is obtained by reverse calculation from the line side according to the following formula: in, is the zero-sequence reactance of the line.

4. The zero-sequence inverse time overcurrent optimization protection method according to claim 1 is characterized in that: Deviation threshold U set The sensitivity and related calculation errors during short circuit and line break faults need to be considered.

5. The zero-sequence inverse time overcurrent optimization protection method according to claim 4 is characterized in that: Deviation threshold U set The value is obtained by the following formula: Where, dU 0f is the fault deviation voltage value in the zone, is the zero-sequence voltage on the opposite side, It is the zero-sequence voltage on the opposite side reversed from this side.

6. The zero-sequence inverse time overcurrent optimization protection method according to claim 1 is characterized in that: When dU0 is greater than the set deviation threshold U set When the zero-sequence inverse time protection meets the action criterion, the zero-sequence inverse time protection is accelerated in the following manner: After the zero-sequence inverse time is accelerated and triggered, the acceleration coefficient kb is calculated in combination with the maximum branch coefficient and reliability coefficient of the line. When kb is greater than 1, the fault zero-sequence current is amplified and accelerated, otherwise it is not amplified and accelerated; When amplifying acceleration, adjust the zero-sequence inverse time acceleration calculation time to: 3I0 is the zero sequence current at the protection installation location, corresponding to the protection of the line side The modulus value of I set is the zero-sequence inverse time overcurrent protection start setting, T P It is the zero-sequence inverse time constant setting, which is adjusted according to the overall zero-sequence inverse time action time requirements.

7. The zero-sequence inverse time overcurrent optimization protection method according to claim 6 is characterized in that: The value of the acceleration factor kb is determined by the following formula:

8. The zero-sequence inverse time overcurrent optimization protection method according to claim 1 or 6, characterized in that: When the voltage difference dU0 is not greater than the set deviation threshold, when the zero-sequence current If the zero-sequence inverse time protection meets the action criterion, it is considered that an out-of-zone positive direction fault has occurred. The zero-sequence inverse time protection cannot be accelerated and the zero-sequence inverse time protection must be used as a remote backup protection for the zero-sequence inverse time overcurrent protection of other adjacent lines.

9. The zero-sequence inverse time overcurrent optimization protection method according to claim 1, characterized in that: The zero-sequence inverse time protection action criteria are as follows: In the formula, I set It is the zero-sequence current starting setting of zero-sequence inverse time protection.

10. The zero-sequence inverse time overcurrent optimization protection method according to claim 1, characterized in that: When dU0 is greater than the set deviation threshold U set When the zero-sequence inverse time protection meets the action criterion, the zero-sequence inverse time protection is accelerated in the following manner: After the zero-sequence inverse time limit is accelerated and triggered, the zero-sequence inverse time limit acceleration calculation time is shortened, and at the same time, the "AND" logical relationship between "zero-sequence inverse time limit calculation time" and "zero-sequence inverse time limit coordination time" is accelerated to the "OR" logical relationship between "shortening the zero-sequence inverse time limit acceleration calculation time" and "zero-sequence inverse time limit coordination time".

11. The zero-sequence inverse time overcurrent optimization protection method according to claim 10, characterized in that: The reduced zero-sequence inverse time acceleration calculation time is calculated according to the following formula: 3I0 is the zero sequence current at the protection installation location, corresponding to the protection of the line side The modulus value of I set is the zero-sequence inverse time overcurrent protection start setting, T P is the zero-sequence inverse time constant constant, which is adjusted according to the overall zero-sequence inverse time action time requirement. kb is the acceleration coefficient calculated by the maximum branch coefficient and reliability coefficient of this line.

12. A transmission line zero-sequence inverse time overcurrent protection optimization system based on the zero-sequence inverse time overcurrent protection optimization method according to any one of claims 1 to 11, comprising a signal acquisition module, an opposite side zero-sequence voltage reverse calculation module, a zero-sequence inverse time protection judgment module, a zero-sequence inverse time acceleration judgment module and a zero-sequence inverse time acceleration module; characterized in that: The signal acquisition module includes a signal acquisition unit on the line side and a signal acquisition unit on the opposite side of the line, which respectively collect the three-phase voltage and three-phase current at the protection installation on the line side and the three-phase voltage and three-phase current on the opposite side of the line; obtain the zero-sequence voltage on the line side and zero sequence current Opposite zero sequence voltage and zero sequence current Opposite zero-sequence voltage reverse calculation module Line zero-sequence reactance and zero sequence current on this side Reverse the calculation to obtain the zero-sequence voltage on the opposite side. The zero-sequence inverse time protection judgment module is based on the zero-sequence current on this side. Compare with the zero-sequence current starting setting of the inverse time protection to determine whether the zero-sequence inverse time protection action criterion is met; The zero-sequence inverse time acceleration judgment module calculates the opposite zero-sequence voltage The zero-sequence voltage on the opposite side reversed from the current side The difference dU0 is realized according to the size of dU0, and adaptive zero-sequence inverse time acceleration and non-acceleration are realized. When dU0 is greater than the set deviation threshold U set When the zero-sequence inverse time protection meets the action criterion, the zero-sequence inverse time acceleration module accelerates the zero-sequence inverse time protection; When dU0 is not greater than the set deviation threshold U set When the zero-sequence inverse time protection meets the action criterion, the zero-sequence inverse time protection does not accelerate.

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