Vacuum OLTC contact action time sequence discrimination method and system

Abstract

The invention relates to a vacuum OLTC contact action time sequence discrimination method and system. The method comprises the following steps: obtaining a line parameter and an initial action phase of a neutral point outlet of an on-load tap changing transformer; theoretical currents of the branches corresponding to the A contact disconnection moment, the K1 contact disconnection starting and complete disconnection moment, the K3 contact closing moment, the K2 contact disconnection starting and complete disconnection moment, the K4 contact closing moment and the B contact closing moment are calculated respectively, and actual current waveforms of the corresponding branches are obtained; calculating a current waveform abnormal index of the theoretical current waveform and the actual current waveform of the branch within a preset time interval after the contact acts; and when the current waveform abnormal index is greater than a preset abnormal threshold value, indicating that the time sequence action of the corresponding contact is abnormal. According to the invention, through comparison between the theoretical transient current waveform and the actual current waveform, accurate discrimination of the contact action time sequence is realized, so that the reliability of fault identification and the operation safety are improved.

Description

Technical Field

[0001] This invention belongs to the field of on-load tap changer technology, and relates to the analysis of on-load tap changer (OLTC) contact action, specifically to a method and system for determining the timing of vacuum OLTC contact action. Background Technology

[0002] Transformers, as crucial devices for regulating system voltage, rely on on-load tap changers (OLTCs) for voltage regulation. Compared to traditional power systems, the frequency of OLTC operations has significantly increased in the context of new power systems. Taking renewable energy collection stations as an example, the average daily number of OLTC operations has increased by 3-5 times. Under conditions of high harmonicity and DC bias, the probability of OLTC failure rises sharply; statistics show that OLTC failures account for over 20% of transformer failures.

[0003] Several methods have been proposed for determining the timing of contact actions in vacuum OLTC systems, but these methods all have certain limitations. Traditional mechanical measurement methods monitor the contact's movement by installing displacement sensors, limit switches, and other devices. However, this method requires direct contact with the contact, which not only interferes with the contact's normal movement but is also susceptible to mechanical wear and vibration, leading to decreased measurement accuracy and reduced reliability over long-term use. Electrical measurement methods mainly infer the timing of contact actions by detecting changes in current and voltage during contact action. While this method avoids direct contact with the contact, in practical applications, the complex electromagnetic interference in power systems can easily distort the detection signal, resulting in inaccurate judgments. Furthermore, the reliability of electrical measurement methods is severely affected when system faults or harmonics are present. Optical measurement methods utilize optical sensors to monitor contact action, offering advantages such as non-contact operation and fast response. However, optical measurement systems have high environmental requirements, are easily affected by dust, oil, and light, and are also expensive, difficult to install and maintain, limiting their widespread application in practical engineering.

[0004] Currently, existing research includes: Patent CN109946597A provides a method for evaluating the operating status of tap changers based on electromechanical signals. This method collects vibration and drive current signals from the tap changer, performs envelope analysis on the current signals to extract operation duration, impact current, and Delta current, and performs wavelet transform and wavelet packet analysis on the vibration signals to extract singularity index and wavelet packet energy entropy. This achieves mechanical operating status evaluation of tap changers based on fuzzy clustering (FCM) algorithm, providing technical support for online monitoring and fault diagnosis. Meanwhile, Chinese patent CN117783728A discloses a method for extracting electromagnetic pulses from the drive motor current of an on-load tap changer in a transformer. By synchronously recording the drive motor current and vibration signals during tap changer voltage regulation operations, the current signal of the action process is selected with the vibration signal as a reference. The mixed signals are separated using cross-correlation functions and independent component analysis (FastICA), enabling the extraction of electromagnetic pulses related to contact action from the drive motor current. This provides important support for tap changer switching procedure analysis and status evaluation.

[0005] In summary, existing methods for determining the timing of vacuum OLTC contact actions primarily focus on other signals generated during the switching process, mainly vibration signals. These methods are easily affected by sensor positions and complex environments, while neglecting the most direct electrical quantity for determining the timing of actions—the transient current of the contacts during the OLTC switching process. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a method and system for determining the timing of contact action in a vacuum OLTC (On-Load Tap Changer) transformer. The method includes: acquiring the line parameters and initial operating phase at the neutral point outlet of the on-load tap changer; calculating the theoretical current of the corresponding branch at the times when contact A opens, contact K1 begins to open and fully opens, contact K3 closes, contact K2 begins to open and fully opens, contact K4 closes, and contact B closes, and acquiring the actual current waveform of the corresponding branch; calculating the current waveform anomaly index between the theoretical and actual current waveforms within a predetermined time interval after contact action; and indicating an abnormal contact timing when the current waveform anomaly index exceeds a predetermined anomaly threshold. This invention enables accurate determination of contact action timing by comparing theoretical transient current with actual current waveforms, thereby improving the reliability of fault identification and operational safety.

[0007] The present invention specifically adopts the following technical solution.

[0008] This invention provides a method for determining the timing of contact action of a vacuum OLTC. The vacuum OLTC includes multiple adjusting connectors. Odd-numbered connectors in two adjacent connectors are connected to the output terminal via contact A, and even-numbered connectors are connected via contact B. On the odd-numbered connector side, a first parallel branch is formed by a series connection of contact K1 and contact K2 and a second resistor R2. One end of the first parallel branch is connected to the odd-numbered connector, and the other end is connected to the output terminal via a switching switch. On the even-numbered connector side, a second parallel branch is formed by a series connection of contact K4 and contact K3 and a third resistor R3. One end of the second parallel branch is connected to the even-numbered connector, and the other end is connected to the output terminal via a switching switch. The method includes the following steps:

[0009] Obtain the line parameters and initial operating phase of the neutral point outlet of the on-load tap-changing transformer; calculate the theoretical current of the corresponding branch at the time when contact A opens, contact K1 begins to open and fully opens, contact K3 closes, contact K2 begins to open and fully opens, contact K4 closes, and contact B closes, and obtain the actual current waveform of the corresponding branch.

[0010] Calculate the current waveform anomaly index of the branch after the contact operates, comparing the theoretical current with the actual current waveform within a predetermined time interval; when the current waveform anomaly index is greater than a predetermined anomaly threshold, it indicates that the corresponding contact timing operation is abnormal.

[0011] Preferably, the process of obtaining the theoretical current and the actual current waveforms is as follows:

[0012] S1, obtain the time t0 when contact A opens, the current switches from the branch where contact A is located to the branch where K1 is located, calculate the theoretical current expression of the K1 branch; obtain the actual current waveform of the K1 branch when contact A opens;

[0013] S2, obtain the moment t1 when the K1 contact starts to open, enter the arc voltage process, calculate the theoretical current expressions for the K1 branch and the K2 branch, and obtain the actual current waveform of the corresponding branch;

[0014] S3, obtain the K1 contact current is less than the predetermined current-cutting value i set That is, the time t2 when the K1 contact is completely open; the current switches from the branch where the K1 contact is located to the branch where the K2 contact is located, calculate the theoretical current expression of the K2 branch and obtain the corresponding actual current waveform;

[0015] S4, obtain the closing time t3 of contact K3. At this time, a bridge is formed. Calculate the theoretical current expressions of branches K2 and K3 and obtain the corresponding actual current waveforms.

[0016] S5, obtain the time t4 when the K2 contact starts to open, calculate the theoretical current of the K2 branch and the K3 branch and obtain the actual current waveform of the corresponding branch;

[0017] S6, obtain the time t5 when K2 contact is completely open, i.e., when the K2 contact current is less than the predetermined current cut-off value i. set The theoretical current of the K3 branch is calculated and the actual current waveform is obtained when the K3 contact carries current alone.

[0018] S7, obtain the closing time t6 of contact K4. At this time, the branch where contact K3 is located is short-circuited. Calculate the theoretical current of branch K4 and obtain the actual current waveform.

[0019] S8, obtain the closing time t7 of contact B. At this time, the branch where K4 is located is short-circuited. Calculate the theoretical current of branch B and obtain the actual current waveform.

[0020] Preferably, the theoretical current expression for branch K1 in S1 is:

[0021]

[0022] In the formula, U is the theoretical current in branch K1 after contact A is opened; m Z is the power supply voltage; s ω is the total impedance of the line; ω is the angular velocity; α is the initial phase of the power supply; φ s This is the initial line impedance angle.

[0023] Preferably, the theoretical current expressions for branches K1 and K2 in S2 are as follows:

[0024]

[0025] In the formula, Theoretical current in branch K1 after contact K1 begins to open; E is the magnitude of arc voltage in the transition branch, corresponding to the magnitude of simulated arc voltage at the moment contact opens; R is the resistance of the branch where contact K2 is located. This is the theoretical current in branch K2 after contact K1 begins to open.

[0026] Preferably, the theoretical current expression for branch K2 in S3 is:

[0027]

[0028] In the formula, i is the theoretical current in branch K2 after contact K1 is completely open; Lp (t) represents the forced component of the theoretical current in branch K2; i Lα (t) represents the free component of the theoretical current in branch K2; Z′ s α is the line impedance when contact K2 or K3 carries current alone; α1 is the power supply phase at time t2; φ′ sThe line impedance angle when contact K2 or K3 carries current alone; E1 is the arc voltage when contact K1 is open; T′ a This is the time constant of the line impedance when contact K2 or K3 carries current alone.

[0029] Preferably, the theoretical current expressions for branches K2 and K3 in S4 are as follows:

[0030]

[0031] In the formula, This represents the theoretical current in branch K2 after contact K3 is closed. This represents the theoretical current in the K3 branch after the K3 contact is closed. This is the forced component after the K3 contact closes; i is the free component after the K3 contact is closed; c (t) represents the circulating current generated by the stage voltage acting on the two transition resistors.

[0032] Preferably, the theoretical current expressions for branches K2 and K3 in S5 are as follows:

[0033]

[0034] In the formula, This represents the theoretical current in branch K2 after contact K3 is closed. This represents the theoretical current in the K3 branch after the K3 contact is closed.

[0035] Preferably, the theoretical current expression for branch K3 in S6 is:

[0036]

[0037] In the formula, This represents the theoretical current in branch K3 after contact K2 is completely open. This is the forced component after contact K2 is completely disconnected; α2 is the free component after contact K2 is completely open; α3 is the power supply phase corresponding to t5; U step The voltage level is [level voltage].

[0038] Preferably, the process of calculating the current waveform anomaly index includes:

[0039] Calculate the deviation between the theoretical current and the actual current waveform of the branch after the contact operates within a predetermined time interval, and use the average value of the current value deviation within the predetermined time interval as the current waveform anomaly index between the theoretical current waveform and the actual current waveform of the branch.

[0040] Another aspect of the present invention provides a vacuum OLTC contact operation timing determination system, comprising:

[0041] The branch theoretical current calculation module obtains the line parameters and initial operating phase of the neutral point outlet of the on-load tap-changing transformer; calculates the theoretical current of the branch corresponding to the time when contact A opens, contact K1 begins to open and fully opens, contact K3 closes, contact K2 begins to open and fully opens, contact K4 closes, and contact B closes, and obtains the actual current waveform of the corresponding branch.

[0042] The contact action timing judgment module calculates the current waveform abnormality index of the branch after contact action and the actual current waveform within a predetermined time interval; when the current waveform abnormality index is greater than the predetermined abnormal threshold, it indicates that the corresponding contact action timing is abnormal.

[0043] Compared with the prior art, the beneficial effects of the present invention include at least the following:

[0044] This invention establishes a theoretical current model for each contact's action moment during the vacuum OLTC contact switching process, compares it with actual current waveforms, and calculates a current waveform anomaly index. This allows for precise identification of whether the contact action sequence is abnormal. Compared with existing methods, this invention can identify anomalies at different contact switching stages, offering strong localization capabilities. This helps to quickly identify potential faults in specific contacts, improves the operational safety and stability of on-load tap-changing transformers, and reduces equipment damage and power outages caused by contact anomalies. Attached Figure Description

[0045] Figure 1 This is a structural diagram of the vacuum OLTC in an embodiment of the present invention;

[0046] Figure 2 This is a schematic diagram of the first and last states of the single-to-dual switching of the vacuum OLTC in an embodiment of the present invention.

[0047] Figure 3 This is a timing diagram of the single-to-dual theoretical switching in an embodiment of the present invention;

[0048] Figure 4 This is a flowchart of the current-contact action correspondence judgment in an embodiment of the present invention;

[0049] Figure 5 This is a schematic diagram illustrating the action judgment of the bridging disconnect contact in an embodiment of the present invention;

[0050] Figure 6 This is a flowchart illustrating the switching process after incorporating the arc voltage process in an embodiment of the present invention;

[0051] Figure 7 This is a schematic diagram showing the correspondence between switching instances and contact actions in an embodiment of the present invention;

[0052] Figure 8This is a schematic diagram of the vacuum OLTC model structure in an embodiment of the present invention. Detailed Implementation

[0053] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of this invention. The embodiments described in this application are merely some embodiments of this invention, and not all embodiments. Based on the spirit of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this invention.

[0054] Vacuum OLTCs regulate output voltage by changing the effective number of turns of the transformer. The relationship between transformer port voltage and winding turns is shown in the equation, where U1 and U1 and n2 represent the effective values ​​of the primary and secondary voltages of the transformer, respectively, and n1 and n2 are the effective number of turns in the primary and secondary windings of the transformer, respectively. During voltage regulation, U1 and n2 remain constant, and the OLTC achieves voltage regulation by adjusting n1.

[0055] Vacuum OLTC composition structure diagram as follows Figure 1 As shown, it mainly consists of a polarity switch, a tap selector, and a switching switch. During the switching process, the load voltage is switched from the A / B contact to the B / A contact through the opening / closing of the transition branch contacts, thereby realizing the on-load tap regulation function. The switching core circuit of the OLTC is as follows: Figure 2 As shown in the figure, A and B are the main contacts of the switching circuit, K1, K2, K3 and K4 are four vacuum tubes, of which K1 and K4 are the main on and off contacts, K2 and K3 are the transition contacts, and R is the transition resistor used to suppress the circulating current of the bridging circuit.

[0056] Embodiment 1 of the present invention provides a method for determining the timing of vacuum OLTC contact action; such as Figure 2 As shown, the vacuum OLTC includes multiple adjustment joints. Odd-numbered joints in two adjacent joints are connected to the output terminal via contact A, and even-numbered joints are connected via contact B. On the odd-numbered joint side, a first parallel branch is formed by the series connection of contact K1 and contact K2 and the second resistor R2. One end of the first parallel branch is connected to the odd-numbered joint, and the other end is connected to the output terminal via a switch. On the even-numbered joint side, a second parallel branch is formed by the series connection of contact K4 and contact K3 and the third resistor R3. One end of the second parallel branch is connected to the even-numbered joint, and the other end is connected to the output terminal via a switch. Taking switching from the odd-numbered side to the even-numbered side as an example, as... Figure 3 , Figure 4 , Figure 5 , Figure 6 and Figure 7As shown, the timing of each contact is determined based on the current occurrence in the four branches; the method includes the following steps:

[0057] Obtain the line parameters and initial operating phase at the neutral point outlet of the on-load tap-changing transformer.

[0058] The initial operating phase is the initial phase of the power supply, that is, the initial phase angle of the power supply voltage when contact A is open; see reference. Figure 8 The line parameters include: angular velocity, total line resistance, total line inductance, arc voltage of the transition branch, resistances R2 and R3 of the branches where contacts K2 and K3 are located, power supply voltage, and current-cutting value I of the vacuum contact. set The total line resistance is equivalent to the resistance from the neutral point outlet to the external network; the total line inductance is equivalent to the inductance from the neutral point outlet to the external network; the arc voltage of the transition branch is the arc voltage generated between the contacts during switching, given by experiment or model parameters; the power supply voltage refers to the voltage level provided by the power grid side; in this embodiment, R2 = R3 = R.

[0059] S1, obtain the moment t0 when contact A opens, the current switches from the branch containing contact A to the branch containing K1, calculate the theoretical current expression for branch K1; obtain the actual current waveform of branch K1 at the moment contact A opens; the theoretical real-time current is specifically expressed as follows:

[0060]

[0061] In the formula, U is the theoretical current in branch K1 after contact A is opened; m This refers to the power supply voltage, i.e., the voltage level provided by the power grid. R is the total impedance of the line. s L is the total resistance of the line. s ω is the total inductance of the line; ω is the angular velocity; α is the initial phase of the power supply; φ s =tan -1 (ωL s / R s ) represents the initial line impedance angle.

[0062] S2, obtain the moment t1 when contact K1 begins to open, and enter the arc voltage process. Calculate the theoretical current expressions for branches K1 and K2, and obtain the actual current waveforms for the corresponding branches. During this process, the theoretical current expressions for branches K1 and K2 are as follows:

[0063]

[0064] In the formula, Theoretical current in branch K1 after contact K1 begins to open; E is the magnitude of arc voltage in the transition branch, corresponding to the magnitude of simulated arc voltage at the moment contact opens; R is the resistance of the branch where contact K2 is located. This is the theoretical current in branch K2 after contact K1 begins to open.

[0065] S3, obtain the K1 contact current is less than the predetermined current-cutting value i set This corresponds to the moment t2 when contact K1 is completely open; the current switches from the branch containing contact K1 to the branch containing contact K2. The theoretical current expression for branch K2 is calculated, and the corresponding actual current waveform is obtained. At this time, the theoretical current expression for branch K2 is:

[0066]

[0067] In the formula, i is the theoretical current in branch K2 after contact K1 is completely open; Lp (t) represents the forced component of the theoretical current in branch K2; i Lα (t) represents the free component of the theoretical current in branch K2; α is the line impedance when contact K2 or K3 carries current alone; α1 is the power supply phase at time t2; φ′ s =tan -1 (ωL s / (R s +R)) is the line impedance angle when contact K2 or K3 carries current alone; E1 is the arc voltage when contact K1 is open; T′ a =L s / (R s +R) is the time constant of the line impedance when contact K2 or K3 carries current alone.

[0068] S4, obtain the closing time t3 of contact K3, at which point a bridging connection is formed. Calculate the theoretical current expressions for branches K2 and K3 and obtain the corresponding actual current waveforms; the specific theoretical current expressions for branches K2 and K3 are as follows:

[0069]

[0070] In the formula, This represents the theoretical current in branch K2 after contact K3 is closed. This represents the theoretical current in the K3 branch after the K3 contact is closed. This is the forced component after the K3 contact closes; This is the free component after contact K3 is closed; α2 is the line impedance when contacts K2 and K3 form a bridge; α2 is the power supply phase at time t3; φ s " = tan -1 (ωLs / (R s +R / 2)) is the line impedance angle when contacts K2 and K3 form a bridge; T a " = L s / (R s +R / 2) is the line impedance time constant when contacts K2 and K3 form a bridge; i c (t) represents the circulating current generated by the stage voltage acting on the two transition resistors; U step The voltage level is [level voltage].

[0071] S5, obtain the time t4 when the K2 contact begins to open, calculate the theoretical current of the K2 and K3 branches and obtain the actual current waveforms of the corresponding branches. The theoretical current expressions for the two branches at this time are as follows:

[0072]

[0073] In the formula, This represents the theoretical current in branch K2 after contact K3 is closed. This represents the theoretical current in the K3 branch after the K3 contact is closed.

[0074] S6, obtain the time t5 when K2 contact is completely open, i.e., when the K2 contact current is less than the predetermined current cut-off value i. set The theoretical current in branch K3 is calculated and the actual current waveform is obtained when contact K3 carries the current alone. The specific theoretical current expression is as follows:

[0075]

[0076]

[0077] In the formula, This represents the theoretical current in branch K3 after contact K2 is completely open. This is the forced component after contact K2 is completely disconnected; α is the free component after contact K2 is completely disconnected; α3 is the power supply phase corresponding to t5.

[0078] S7, obtain the closing time t6 of contact K4. At this time, the branch containing contact K3 is short-circuited. Calculate the theoretical current of branch K4 and obtain the actual current waveform; the specific expression is as follows:

[0079]

[0080] In the formula, This represents the theoretical current in the K4 branch after the K4 contact is closed. This is the forced component after the K4 contact closes; α4 is the free component after contact K4 is closed; α4 is the power supply phase at time t6.

[0081] S8, obtain the closing time t7 of contact B. At this time, the branch containing K4 is short-circuited. Calculate the theoretical current of branch B and obtain the actual current waveform; the specific expression is as follows:

[0082]

[0083] In the formula, i B (t) represents the theoretical current of branch B.

[0084] For each contact's action judgment, the deviation between the theoretical current and the actual current waveform of the branch after contact action is calculated within a predetermined time interval. The average value of the current value deviation within the predetermined time interval is used as the current waveform anomaly index of the theoretical current waveform and the actual current waveform of that branch. The specific calculation formula is as follows:

[0085]

[0086] In the formula, S is the current waveform anomaly index; T is the predetermined time interval; ||T|| is the total number of sampling moments within the predetermined time interval; i the,t i represents the theoretical current value at sampling time t; act,t This represents the actual current value at sampling time t.

[0087] When the current waveform abnormality index is greater than the predetermined abnormality threshold, it indicates that the timing action of the corresponding contact is abnormal; when the current waveform abnormality index is not greater than the predetermined abnormality threshold, it indicates that the timing action of the corresponding contact is normal.

[0088] In this embodiment, the predetermined time interval is the interval of a predetermined time period after the corresponding contact action and the interval of a predetermined time period before the next contact action, and the predetermined time period is a set value; for the judgment of the action of contacts S4 and S5, the current waveform abnormality index of the theoretical current and the corresponding actual current waveform of the K2 branch and K3 branch is calculated respectively. If the current waveform abnormality index of any branch is greater than the predetermined abnormal threshold, it indicates that the timing action of the corresponding contact is abnormal; the judgment of the action of contact S2 is also made in the same way, that is, the current waveform abnormality index of the theoretical current and the corresponding actual current waveform of the K1 branch and K2 branch is calculated respectively for judgment.

[0089] Embodiment 2 of the present invention provides a timing discrimination system for vacuum OLTC contact action; including:

[0090] The branch theoretical current calculation module obtains the line parameters and initial operating phase of the neutral point outlet of the on-load tap-changing transformer; calculates the theoretical current of the branch corresponding to the time when contact A opens, contact K1 begins to open and fully opens, contact K3 closes, contact K2 begins to open and fully opens, contact K4 closes, and contact B closes, and obtains the actual current waveform of the corresponding branch.

[0091] The contact action timing judgment module calculates the current waveform abnormality index of the branch after contact action and the actual current waveform within a predetermined time interval; when the current waveform abnormality index is greater than the predetermined abnormal threshold, it indicates that the corresponding contact action timing is abnormal.

[0092] This disclosure can be a system, method, and / or computer program product. A computer program product may include a computer-readable storage medium having computer-readable program instructions loaded thereon for causing a processor to implement various aspects of this disclosure.

[0093] Computer-readable storage media can be tangible devices capable of holding and storing instructions for use by an instruction execution device. Computer-readable storage media can be, for example—but not limited to—electrical storage devices, magnetic storage devices, optical storage devices, electromagnetic storage devices, semiconductor storage devices, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of computer-readable storage media include: portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), static random access memory (SRAM), portable compact disc read-only memory (CD-ROM), digital multifunction disc (DVD), memory sticks, floppy disks, mechanical encoding devices, such as punch cards or recessed protrusions storing instructions thereon, and any suitable combination of the foregoing. The computer-readable storage media used herein are not to be construed as transient signals themselves, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through waveguides or other transmission media (e.g., light pulses through fiber optic cables), or electrical signals transmitted through wires.

[0094] The computer-readable program instructions described herein can be downloaded from computer-readable storage media to various computing / processing devices, or downloaded via a network, such as the Internet, local area network, wide area network, and / or wireless network, to an external computer or external storage device. The network may include copper transmission cables, fiber optic transmission, wireless transmission, routers, firewalls, switches, gateway computers, and / or edge servers. A network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards them to the computer-readable storage media in the respective computing / processing device.

[0095] Computer program instructions used to perform the operations of this disclosure may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, status 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 the "C" language or similar programming languages. The computer-readable program instructions may execute entirely on the user's computer, partially on the user's computer, as a standalone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In cases involving 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., via the Internet using an Internet service provider). In some embodiments, electronic circuitry, such as programmable logic circuitry, field-programmable gate arrays (FPGAs), or programmable logic arrays (PLAs), is personalized by utilizing the status information of the computer-readable program instructions to implement various aspects of this disclosure.

[0096] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention.

Claims

1. A method for determining the timing of contact operation of a vacuum OLTC, wherein the vacuum OLTC includes multiple adjusting connectors, and the odd-numbered connectors of two adjacent connectors are connected to the output terminal via contact A, and the even-numbered connectors are connected via contact B. On the odd-numbered connector side, a first parallel branch is formed by a series connection of contact K1 and contact K2 and a second resistor R2, one end of which is connected to the odd-numbered connector, and the other end is connected to the output terminal via a switching switch; on the even-numbered connector side, a second parallel branch is formed by a series connection of contact K4 and contact K3 and a third resistor R3, one end of which is connected to the even-numbered connector, and the other end is connected to the output terminal via a switching switch; characterized in that… The method includes the following steps: Obtain the line parameters and initial operating phase of the neutral point outlet of the on-load tap-changing transformer; calculate the theoretical current of the corresponding branch at the time when contact A opens, contact K1 begins to open and fully opens, contact K3 closes, contact K2 begins to open and fully opens, contact K4 closes, and contact B closes, and obtain the actual current waveform of the corresponding branch. Calculate the current waveform anomaly index of the branch after the contact operates, comparing the theoretical current with the actual current waveform within a predetermined time interval; when the current waveform anomaly index is greater than a predetermined anomaly threshold, it indicates that the corresponding contact timing operation is abnormal.

2. The method for determining the timing of vacuum OLTC contact operation according to claim 1, characterized in that, The process of obtaining the theoretical current and actual current waveforms is as follows: S1, obtain the time t0 when contact A opens, the current switches from the branch where contact A is located to the branch where K1 is located, calculate the theoretical current expression of the K1 branch; obtain the actual current waveform of the K1 branch when contact A opens; S2, obtain the moment t1 when the K1 contact starts to open, enter the arc voltage process, calculate the theoretical current expressions for the K1 branch and the K2 branch, and obtain the actual current waveform of the corresponding branch; S3, obtain the K1 contact current is less than the predetermined current-cutting value i set That is, the time t2 when the K1 contact is completely open; the current switches from the branch where the K1 contact is located to the branch where the K2 contact is located, calculate the theoretical current expression of the K2 branch and obtain the corresponding actual current waveform; S4, obtain the closing time t3 of contact K3. At this time, a bridge is formed. Calculate the theoretical current expressions of branches K2 and K3 and obtain the corresponding actual current waveforms. S5, obtain the time t4 when the K2 contact starts to open, calculate the theoretical current of the K2 branch and the K3 branch and obtain the actual current waveform of the corresponding branch; S6, obtain the time t5 when K2 contact is completely open, i.e., when the K2 contact current is less than the predetermined current-cutting value i. set The theoretical current of the K3 branch is calculated and the actual current waveform is obtained when the K3 contact carries current alone. S7, obtain the closing time t6 of contact K4. At this time, the branch where contact K3 is located is short-circuited. Calculate the theoretical current of branch K4 and obtain the actual current waveform. S8, obtain the closing time t7 of contact B. At this time, the branch where K4 is located is short-circuited. Calculate the theoretical current of branch B and obtain the actual current waveform.

3. The method for determining the timing of vacuum OLTC contact operation according to claim 2, characterized in that: The theoretical current expression for branch K1 in S1 is: In the formula, U is the theoretical current in branch K1 after contact A is opened; m Z is the power supply voltage; s ω is the total impedance of the line; ω is the angular velocity; α is the initial phase of the power supply; φ s This is the initial line impedance angle.

4. The method for determining the timing of vacuum OLTC contact operation according to claim 2, characterized in that: The theoretical current expressions for branches K1 and K2 in S2 are as follows: In the formula, Theoretical current in branch K1 after contact K1 begins to open; E is the magnitude of arc voltage in the transition branch, corresponding to the magnitude of simulated arc voltage at the moment contact opens; R is the resistance of the branch where contact K2 is located. This is the theoretical current in branch K2 after contact K1 begins to open.

5. The method for determining the timing of vacuum OLTC contact operation according to claim 2, characterized in that: The theoretical current expression for branch K2 in S3 is: In the formula, i is the theoretical current in branch K2 after contact K1 is completely open; Lp (t) represents the forced component of the theoretical current in branch K2; i Lα (t) represents the free component of the theoretical current in branch K2; Z s ′ represents the line impedance when contact K2 or K3 carries current alone; α1 represents the power supply phase at time t2; φ s ′ is the line impedance angle when contact K2 or K3 carries current alone; E1 is the arc voltage when contact K1 is open; T a ′ is the time constant of the line impedance when contact K2 or K3 carries current alone.

6. The method for determining the timing of vacuum OLTC contact operation according to claim 2, characterized in that: The theoretical current expressions for branches K2 and K3 in S4 are: In the formula, This represents the theoretical current in branch K2 after contact K3 is closed. This represents the theoretical current in the K3 branch after the K3 contact is closed. This is the forced component after the K3 contact closes; i is the free component after the K3 contact is closed; c (t) represents the circulating current generated by the stage voltage acting on the two transition resistors.

7. The method for determining the timing of vacuum OLTC contact operation according to claim 2, characterized in that: The theoretical current expressions for branches K2 and K3 in S5 are: In the formula, This represents the theoretical current in branch K2 after contact K3 is closed. This represents the theoretical current in the K3 branch after the K3 contact is closed.

8. The method for determining the timing of vacuum OLTC contact operation according to claim 2, characterized in that: The theoretical current expression for branch K3 in S6 is: In the formula, This represents the theoretical current in branch K3 after contact K2 is completely open. This is the forced component after contact K2 is completely disconnected; α2 is the free component after contact K2 is completely open; α3 is the power supply phase corresponding to t5; U step The voltage level is [level voltage].

9. The method for determining the timing of vacuum OLTC contact operation according to claim 1, characterized in that: The process of calculating the current waveform anomaly index includes: Calculate the deviation between the theoretical current and the actual current waveform of the branch after the contact operates within a predetermined time interval, and use the average value of the current value deviation within the predetermined time interval as the current waveform anomaly index between the theoretical current waveform and the actual current waveform of the branch.

10. A vacuum OLTC contact action timing determination system, comprising the method described in any one of claims 1 to 9, characterized in that, include: The branch theoretical current calculation module obtains the line parameters and initial operating phase of the neutral point outlet of the on-load tap-changing transformer; Calculate the theoretical current of the branch corresponding to the time when contact A opens, the time when contact K1 begins to open and fully opens, the time when contact K3 closes, the time when contact K2 begins to open and fully opens, the time when contact K4 closes, and the time when contact B closes, and obtain the actual current waveform of the corresponding branch. The contact action timing judgment module calculates the current waveform abnormality index of the branch after contact action and the actual current waveform within a predetermined time interval; when the current waveform abnormality index is greater than the predetermined abnormal threshold, it indicates that the corresponding contact action timing is abnormal.

Images