Broken line fault distinguishing and handling method for large oil-immersed power transformer

Abstract

The invention provides a broken line fault distinguishing and processing method for a large-scale oil-immersed power transformer, and relates to the technical field of transformer fault detection, and the method comprises the steps: for the high-voltage side of a main transformer, employing four distinguishing modes H1-H4 to distinguish whether the high-voltage side of the main transformer has a broken line fault; for the medium-voltage side of the main transformer, judging whether the medium-voltage side of the main transformer has a broken line fault or not by adopting two judgment modes of M1-M2; if at least one judgment mode judges that the high-voltage side of the main transformer has the disconnection fault, one-key sequential control is carried out by adopting a first operation sequence so as to trip off three-side circuit breakers of the main transformer; and if at least one judgment mode judges that the medium-voltage side of the main transformer has the broken line fault, one-key sequential control is carried out by adopting a second operation sequence so as to trip off three-side circuit breakers of the main transformer. According to the scheme, judgment and timely disposal of the broken line fault of the transformer can be realized, and a guarantee is provided for safe and stable operation of the large oil-immersed transformer.

Description

Technical Field

[0001] The present invention relates to the technical field of transformer fault detection, and particularly relates to a method for discriminating and disposing of broken wire faults of large oil-immersed power transformers. Background Art

[0002] Large oil-immersed power transformers are core equipment of the power grid. As a key component connecting the internal winding and the external transmission line, their bushings undertake multiple functions such as high-voltage insulation, mechanical fixation, and current transmission. Transformer bushings are usually made of porcelain or composite insulating materials, with a conductive rod running through the inside and filled with insulating oil. Being exposed to complex working conditions for a long time, their broken wire faults have become one of the main hidden dangers threatening the safe operation of transformers.

[0003] In recent years, the proportion of transformer faults caused by bushing broken wire faults has increased significantly. For example, at the end of 2021, a C-phase bushing fracture fault occurred in the high-voltage side of the No. 3 main transformer of a 750 kV substation, and the high-voltage side wiring method was two-thirds wiring. Since the existing main transformer protection does not have good sensitivity to broken wire faults under low load conditions, about 2 hours after the fault occurred, as the load gradually increased, the backup protection of the main transformer operated and tripped the circuit breakers on the three sides of the main transformer. And if the bushing is displaced and falls during the bushing fracture process, situations such as combustion and explosion will occur, which will seriously affect the safe and stable operation of substation equipment.

[0004] In addition, if the bushing broken wire fault is not disposed of in time, it may quickly evolve from partial discharge to insulation breakdown, which requires replacing the entire bushing during repair, with high costs and a time-consuming process of up to several weeks. Therefore, there is an urgent need to provide a discrimination and disposal solution for broken wire faults of oil-immersed power transformers. Summary of the Invention

[0005] In view of this, in view of the above deficiencies, it is necessary to propose a method for discriminating and disposing of broken wire faults of large oil-immersed power transformers to realize the discrimination and timely disposal of transformer broken wire faults and provide guarantee for the safe and stable operation of large oil-immersed transformers.

[0006] The present invention provides a method for discriminating and disposing of broken wire faults of large oil-immersed power transformers, including:

[0007] For the high-voltage side of the main transformer, four discrimination methods H1 to H4 are respectively used to discriminate whether a broken wire fault occurs on the high-voltage side of the main transformer; among them, H1 is discriminated through the power D5000 system, H2 is discriminated by comparing the measured value of the bushing current on the high-voltage side with the sum current, H3 is discriminated according to the zero-sequence current of the high-voltage side bushing, and H4 is discriminated through the main transformer fault recorder;

[0008] For the medium-voltage side of the main transformer, two discrimination methods, M1 to M2, are respectively used to determine whether a disconnection fault occurs on the medium-voltage side of the main transformer; among them, M1 is to determine through the fault recorder of the main transformer, and M2 is to determine according to the telemetered current value of the medium-voltage side of the main transformer;

[0009] If at least one discrimination method determines that there is a disconnection fault on the high-voltage side of the main transformer, the first operation sequence is used for one-key sequence control to trip the circuit breakers on the three sides of the main transformer;

[0010] If at least one discrimination method determines that there is a disconnection fault on the medium-voltage side of the main transformer, the second operation sequence is used for one-key sequence control to trip the circuit breakers on the three sides of the main transformer.

[0011] Preferably, the discrimination method of H1 includes:

[0012] Using the monitoring function of the power D5000 system, the alarm function for the over-limit of the zero-sequence current on the high-voltage side of the 750kV main transformer and the alarm function for the single-phase operation on the high-voltage side of the 750kV main transformer are added;

[0013] Among them, the discrimination logic for the over-limit of the zero-sequence current on the high-voltage side of the 750kV main transformer is: according to the three-phase telemetered current on the high-voltage side of the main transformer uploaded by the substation side, the zero-sequence current is calculated on the main station side; and when n times of the calculated zero-sequence current is greater than the first preset current value, it is determined that there is a disconnection fault, and an alarm is issued after a delay of the first preset duration;

[0014] The discrimination logic for the single-phase operation on the high-voltage side of the 750kV main transformer is: when the current of each phase on the high-voltage side is greater than the first preset current value and the power on the high-voltage side is greater than the first preset power value, the operating state of the main transformer is judged; if the current of any phase on the high-voltage side of the main transformer suddenly becomes 0, it is determined that a disconnection fault occurs on the high-voltage side of the main transformer.

[0015] Preferably, the discrimination method of H2 includes:

[0016] Compare the current of the bushing on the high-voltage side of the main transformer with the telemetered value of the sum current; if the current of a certain phase of the bushing current on the high-voltage side and the sum current becomes 0, it is determined that a disconnection fault occurs in that phase.

[0017] Preferably, the discrimination method of H3 includes:

[0018] The three-phase currents of the high-voltage side bushing form a self-generated zero-sequence current through the series connection of the main transformer body measurement and control circuit, and the self-generated zero-sequence current is sent to the background monitoring, and the zero-sequence current threshold is set as the second preset current value; when the background monitoring shows that the zero-sequence current is greater than the second preset current value, it is determined that a disconnection fault occurs, and an over-limit alarm of the current is issued.

[0019] Preferably, the discrimination method of H4 includes:

[0020] Collect the current of the high-voltage side bushing using the main station fault recorder; if the current of a certain phase drops to 0 and the currents of the other two phases are normal, then check the current of the medium-voltage side bushing; if the zero-sequence current component exists in the current of the medium-voltage side bushing, it is determined that a primary disconnection fault occurs on the high-voltage side, and if the zero-sequence current component does not exist in the current of the medium-voltage side bushing, it is determined that a secondary disconnection fault occurs on the high-voltage side.

[0021] Preferably, the discrimination method of M1 includes:

[0022] Monitor the current of the medium-voltage side bushing using the main transformer fault recorder; if the current of a certain phase of the medium-voltage side bushing drops to 0 while the currents of the other two phases are normal, then further check the current of the high-voltage side bushing; if the zero-sequence current component exists in the current of the high-voltage side bushing, it is determined that a primary disconnection fault occurs on the medium-voltage side; if the zero-sequence current component does not exist in the current of the high-voltage side bushing, it is determined that a secondary disconnection fault occurs on the medium-voltage side.

[0023] Preferably, the discrimination method of M2 includes:

[0024] Monitor the current of the medium-voltage side bushing through the main transformer fault recorder; if the current of a certain phase of the medium-voltage side bushing drops to 0 in the main transformer fault recorder, then view the remote measurement value of the main transformer medium-voltage side current sent by the medium-voltage side circuit breaker in the post-monitoring; if the phase current corresponding to the medium-voltage side circuit breaker also drops to 0, it is determined that a disconnection fault occurs on the medium-voltage side.

[0025] Preferably, the first operation sequence is: control the opening of the 750kV high-voltage side middle circuit breaker, control the opening of the 750kV high-voltage side edge circuit breaker, control the opening of the 220kV medium-voltage side circuit breaker, control the opening of the low-voltage side 1 branch circuit breaker, control the opening of the low-voltage side 2 branch circuit breaker;

[0026] The second operation sequence is: control the opening of the 220kV medium-voltage side circuit breaker, control the opening of the 750kV high-voltage side middle circuit breaker, control the opening of the 750kV high-voltage side edge circuit breaker, control the opening of the low-voltage side 1 branch circuit breaker, control the opening of the low-voltage side 2 branch circuit breaker.

[0027] Preferably, the discrimination method for determining whether there is a disconnection fault on the high-voltage side of the main transformer further includes H5, and the discrimination method for determining whether there is a disconnection fault on the medium-voltage side of the main transformer further includes M3; among them, both H5 and M3 are used to discriminate the disconnection fault through the disconnection monitoring device;

[0028] If at least one of the discrimination methods of H1 to H5 discriminates that there is a disconnection fault on the high-voltage side of the main transformer, then use the first operation sequence for one-key sequence control to trip the circuit breakers on the three sides of the main transformer;

[0029] If at least one of the discrimination methods of M1 to M3 discriminates that there is a disconnection fault on the medium-voltage side of the main transformer, then use the second operation sequence for one-key sequence control to trip the circuit breakers on the three sides of the main transformer.

[0030] Preferably, the open-circuit monitoring device is a microcomputer transformer protection device of the WBH-800 series.

[0031] As can be seen from the above technical solutions, in the open-circuit fault discrimination and disposal method for a large oil-immersed power transformer provided by the present invention, for the high-voltage side of the main transformer, four discrimination methods, namely H1 to H4, can be respectively used to discriminate whether an open-circuit fault occurs on the high-voltage side of the main transformer. Among them, H1 is discriminated through the power D5000 system, H2 is discriminated by comparing the telemetry values of the bushing current and the sum current on the high-voltage side, H3 is discriminated according to the zero-sequence current of the high-voltage side bushing, and H4 is discriminated through the main transformer fault recorder. For the medium-voltage side of the main transformer, two discrimination methods, namely M1 to M2, can be respectively used to discriminate whether a line selection fault occurs on the medium-voltage side of the main transformer. Among them, M1 is discriminated through the main transformer fault recorder, and M2 is discriminated according to the telemetry value of the medium-voltage side current of the main transformer. If at least one discrimination method discriminates that there is an open-circuit fault on the high-voltage side of the main transformer, then the circuit breakers on the three sides of the main transformer are tripped by means of one-key sequence control operation in the first operation sequence. If at least one discrimination method discriminates that there is an open-circuit fault on the medium-voltage side of the main transformer, the circuit breakers on the three sides of the main transformer are tripped by means of one-key sequence control in the second operation sequence. As can be seen from the above technical solutions, in this solution, multiple discrimination methods are respectively used to discriminate the open-circuit faults on the high-voltage side and the medium-voltage side of the main transformer, ensuring the accuracy of the open-circuit fault discrimination and disposal and avoiding the occurrence of fault underreporting. At the same time, corresponding sequence control operations can be respectively adopted to trip the circuit breakers on the three sides of the main transformer, reducing the further deterioration and the probability of potential accident caused thereby, so as to provide a strong guarantee for the safe and stable operation of the large oil-immersed transformer. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a flowchart of a method for discriminating and disposing an open-circuit fault of a large oil-immersed power transformer provided by an embodiment of the present invention.

[0033] Figure 2 It is an application configuration schematic diagram of a transformer open-circuit monitoring device provided by an embodiment of the present invention.

[0034] Figure 3 It is a logic diagram of the low-value section for monitoring the open phase of phase A.

[0035] Figure 4 It is a logic diagram of the high-value section for monitoring the open phase of phase A. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0036] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required to be used in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained according to these drawings without creative efforts.

[0037] As Figure 1 shown, the present invention provides a method for discriminating and disposing of open - circuit faults of a large oil - immersed power transformer, and the method may include the following steps:

[0038] Step 101: For the high - voltage side of the main transformer, four discrimination methods H1 to H4 are respectively used to discriminate whether an open - circuit fault occurs on the high - voltage side of the main transformer; among them, H1 is discriminated through the power D5000 system, H2 is discriminated by comparing the measured values of the bushing current and the sum current on the high - voltage side, H3 is discriminated according to the zero - sequence current of the high - voltage side bushing, and H4 is discriminated through the main transformer fault recorder;

[0039] Step 102: For the medium - voltage side of the main transformer, two discrimination methods M1 to M2 are respectively used to discriminate whether an open - circuit fault occurs on the medium - voltage side of the main transformer; among them, M1 is discriminated through the main transformer fault recorder, and M2 is discriminated according to the measured value of the current on the medium - voltage side of the main transformer;

[0040] Step 103: If at least one discrimination method discriminates that there is an open - circuit fault on the high - voltage side of the main transformer, one - key sequence control is performed using the first operation sequence to trip the circuit breakers on the three sides of the main transformer;

[0041] Step 104: If at least one discrimination method discriminates that there is an open - circuit fault on the medium - voltage side of the main transformer, one - key sequence control is performed using the second operation sequence to trip the circuit breakers on the three sides of the main transformer.

[0042] In this embodiment, the open - circuit faults of the high - voltage side and the medium - voltage side of the main transformer are discriminated by multiple discrimination methods respectively, ensuring the accuracy of the discrimination and disposal of the open - circuit faults and avoiding the occurrence of missed fault reports. At the same time, corresponding sequence control operations can be respectively taken to trip the circuit breakers on the three sides of the main transformer, reducing the probability of further deterioration and potential accident hazards, so as to provide a strong guarantee for the safe and stable operation of large oil - immersed transformers.

[0043] For step 101, it is used to discriminate the open - circuit fault on the high - voltage side, and the discrimination methods may include four discrimination methods H1 to H4.

[0044] For the H1 discrimination method, it is considered to be discriminated through the power D5000 system. Specifically, for the open - circuit fault on the high - voltage side of the 750kV main transformer, by using the monitoring function of the dispatching main station D5000 system, two alarm signals, namely "over - limit of zero - sequence current on the high - voltage side of the 750kV main transformer" and "single - phase operation on the high - voltage side of the 750kV main transformer", are added.

[0045] 1) Alarm discrimination logic for "Zero-sequence current limit exceeded on the high-voltage side of the 750kV main transformer". Based on the three-phase telemetered currents on the high-voltage side of the main transformer sent from the substation terminal, the zero-sequence current is calculated on the master station side. When the calculated value of 3I0 is greater than 10A, it is determined that there is a disconnection fault, and then an alarm is issued after a 30s delay. The alarm threshold of the main transformer, that is, the first preset current value, can be set according to the operating load curve of the main transformer. Of course, the sensitivity should be higher than the abnormal alarm of the current transformer TA of the main transformer protection.

[0046] 2) Alarm discrimination logic for "Single-phase operation of the 750kV main transformer". When the current of each phase on the high-voltage side is greater than 10A and the power on the high-voltage side is greater than 12MW, the operating state of the main transformer is judged. At this time, if the current of any one phase on the high-voltage side of the main transformer suddenly becomes 0, it is judged that a disconnection fault has occurred on the high-voltage side of the main transformer.

[0047] For the H2 discrimination method, it is considered to judge by comparing the telemetered values of the bushing current on the high-voltage side and the sum current. Specifically, it can be considered to transform the circuit so that the bushing current on the high-voltage side of the main transformer is connected to the main transformer body monitoring and control device and sent to the background monitoring. On the main transformer monitoring screen of the background monitoring, the telemetered values of the bushing current on the high-voltage side of the main transformer and the sum current are compared. When the current of a certain phase of the bushing current on the high-voltage side and the sum current becomes 0, it means that this phase is disconnected. In this way, by comparing the currents from two different sources, the disconnection on the high-voltage side can be indirectly judged.

[0048] For the H3 discrimination method, it is considered to judge according to the zero-sequence current of the bushing on the high-voltage side. Specifically, the three-phase currents of the bushing on the high-voltage side form a self-generated zero-sequence current through the series connection of the main transformer body monitoring and control circuit. The self-generated zero-sequence current is sent to the background monitoring. Under normal circumstances, this zero-sequence current is 0. Set the zero-sequence current threshold to 30A. When the zero-sequence current is greater than 30A, it can be determined that a disconnection fault has occurred. Further, an alarm soft message of "Zero-sequence current limit exceeded on the high-voltage side of the main transformer" can be sent through the background monitoring. The alarm sound of "Zero-sequence current limit exceeded on the high-voltage side of the main transformer" can also be set to a special sound to remind the operating personnel to check the relevant information in time.

[0049] For the H4 discrimination method, it is considered to judge through the main transformer fault recorder. For example, taking the No. 3 main transformer as an example, the high-voltage side bushing current is collected by the fault recorder of the No. 3 main transformer in this station. Under normal circumstances, the amplitudes of the three-phase currents of the high-voltage side bushing are equal, the angles differ by 120°, and the positive-sequence direction. If the current of a certain phase drops to 0 and the other two-phase currents are normal, it means that there is an open circuit in this phase circuit. Then check the bushing current on the medium-voltage side. If there is a zero-sequence current component in the bushing current on the medium-voltage side at this time, it can be judged that there is a primary disconnection on the high-voltage side. If it is a secondary disconnection, only zero-sequence current will be generated on the high-voltage side, and no zero-sequence current will be generated on the medium-voltage side.

[0050] In addition, the fault recorder of the No. 3 main transformer also has a steady-state recording function, generating a recording file every 1.5 minutes. If zero-sequence current occurs on the high-voltage side at a certain moment, the currents of all branches of the main transformer at that moment can be viewed. By comparing the zero-sequence currents of the bushings on the high-voltage and medium-voltage sides, it can be determined whether there is a break on the high-voltage side.

[0051] For step 102, this step considers using two discrimination methods, M1 and M2, to determine whether there is a break fault on the medium-voltage side.

[0052] For the M1 discrimination method, it considers using the main transformer fault recorder for judgment. There is only one current transformer for the bushing on the medium-voltage side, which is used by the main transformer fault recorder. Therefore, only the main transformer fault recorder can be used to view the current situation of the bushing on the medium-voltage side. If the current of a certain phase of the bushing on the medium-voltage side drops to 0 while the currents of the other two phases are normal, it indicates that there is an open circuit in this phase circuit. Then, check the current situation of the bushing on the high-voltage side. If the zero-sequence current component exists in the current of the bushing on the high-voltage side at this time, it can be determined that there is a break in the primary side of the medium-voltage side. If it is a secondary break, only zero-sequence current will be generated on the medium-voltage side, and no zero-sequence current will be generated on the high-voltage side.

[0053] For the M2 discrimination method, it considers judging according to the telemetry value of the current of the medium-voltage side of the main transformer. Monitor the current of the bushing on the medium-voltage side through the main transformer fault recorder. If the current of a certain phase of the bushing on the medium-voltage side recorded by the main transformer fault recorder drops to 0, the telemetry value of the current of the medium-voltage side of the main transformer in the background monitoring can be viewed as an auxiliary. This current telemetry value is sent by the current transformer on the circuit breaker of the medium-voltage side. If the corresponding phase current of this current transformer also drops to 0, it can indirectly indicate that there is a break on the medium-voltage side.

[0054] In addition, for the break faults on the high-voltage side and medium-voltage side of the main transformer, the break discrimination can also be carried out through a break monitoring device. For example, a microcomputer transformer protection device of the WBH-8000 series can be used, such as the WBH-805T-DG-G microcomputer transformer protection device. Specifically, the discrimination method for determining whether there is a break fault on the high-voltage side of the main transformer also includes H5, and the discrimination method for determining whether there is a break fault on the medium-voltage side of the main transformer also includes M3; among them, both H5 and M3 are for break fault discrimination through the break monitoring device; thus, if at least one of the discrimination methods from H1 to H5 discriminates that there is a break fault on the high-voltage side of the main transformer, the first operation sequence is adopted for one-key sequence control to trip the circuit breakers on the three sides of the main transformer; if at least one of the discrimination methods from M1 to M3 discriminates that there is a break fault on the medium-voltage side of the main transformer, the second operation sequence is adopted for one-key sequence control to trip the circuit breakers on the three sides of the main transformer.

[0055] The break monitoring device can solve the problem that the protection device is not sensitive to break faults during the low-load operation of the main transformer in the breaker-and-a-half connection mode. The break monitoring device developed by Ultra High Voltage United with Xuji Electric, and the application configuration of this device is as Figure 2As shown. The transformer open-circuit monitoring device is mainly used to detect the open-phase operation of the transformer and avoid damage to the equipment caused by long-term open-phase operation. The transformer open-circuit monitoring is set with two segments of high and low values, which are designed according to the three phases of A, B, and C respectively. Taking phase A as an example, the logic of the low-value segment and the high-value segment of the open-circuit monitoring of phase A are respectively as Figure 3 and Figure 4 shown.

[0056] In the figure, I p is the lower limit value of the current that the current transformer can accurately detect, and I set1 is the fixed value of the maximum load current of the low value. When the actual load current is greater than I set1 , the low-value segment exits and the high-value segment is put into operation. I2 is the negative-sequence current, I1 is the positive-sequence current, I0 is the zero-sequence current, and I A(2T) , I B(2T) , I C(2T) are the currents in the previous 2 cycles before startup. K 0set is the ratio setting value of the zero-sequence current to the positive-sequence current, and K 2set is the ratio setting value of the negative-sequence current to the positive-sequence current. The setting value I 0set1 of the zero-sequence current of the low-voltage side bushing is set to avoid the maximum unbalanced zero-sequence current under the maximum load current I set1 of the low value.

[0057] U2 is the negative-sequence voltage, U1 is the positive-sequence voltage, 3U0 is the zero-sequence voltage, and U is the minimum line voltage. U 2set is the setting value of the negative-sequence voltage, 3U 0set is the setting value of the zero-sequence voltage, 3U 0(2T) is the voltage in the previous 2 cycles before startup, and U set is the setting value of the line voltage. Among them, the & symbol in the logic diagram represents the AND relationship, and the ≥ symbol represents the OR relationship.

[0058] The low-voltage blocking element is set to avoid the lowest operating voltage, can reliably return after the fault is removed, and ensure sufficient sensitivity during the fault. It can generally be set to 60% - 70% of the lowest operating voltage of the bus. The negative-sequence and zero-sequence voltage blocking elements are set to avoid the maximum unbalanced voltage during normal operation. The negative-sequence voltage blocking value can be set to 2 - 6V, and the zero-sequence voltage blocking value can be set to 4 - 8V.

[0059] By applying the open-circuit monitoring device to each phase of the high-voltage side or the medium-voltage side, it is possible to determine whether there is an open-circuit fault in the corresponding phase of the high-voltage side or the medium-voltage side by checking whether the device issues an open-phase alarm.

[0060] Steps 103 and 104 are used to perform fault handling for the high-voltage side open-circuit fault and the medium-voltage side open-circuit fault respectively.

[0061] When dealing with the open-circuit fault, it is possible to first report to the higher-level department. That is, when the operating personnel find that the main transformer has an open-circuit fault through comprehensive judgment or on-site inspection, they should first report to the network dispatching, provincial dispatching, and production dispatching departments of the ultra-high voltage company, report the operating conditions of the on-site main transformer, and clarify the judgment basis. Then, according to the dispatching instructions, perform the "one-key sequence control" operation for the open-circuit fault of the main transformer to trip the circuit breakers on the three sides of the main transformer.

[0062] Specifically, as Figure 2 shown, when an open-circuit fault occurs on the high-voltage side of the main transformer, the operation sequence of the "one-key sequence control" is: control the opening of circuit breaker QF2 in the middle of the 750 kV high-voltage side, control the opening of circuit breaker QF1 on the side of the 750 kV high-voltage side, control the opening of circuit breaker QF5 on the 220 kV medium-voltage side, control the opening of circuit breaker QF3 of the 1st branch on the low-voltage side, and control the opening of circuit breaker QF4 of the 2nd branch on the low-voltage side.

[0063] When an open-circuit fault occurs on the medium-voltage side of the main transformer, the operation sequence of the "one-key sequence control" is: control the opening of circuit breaker QF5 on the 220 kV medium-voltage side, control the opening of circuit breaker QF2 in the middle of the 750 kV high-voltage side, control the opening of circuit breaker QF1 on the side of the 750 kV high-voltage side, control the opening of circuit breaker QF3 of the 1st branch on the low-voltage side, and control the opening of circuit breaker QF4 of the 2nd branch on the low-voltage side.

[0064] Among them, TA1 is the current transformer of the circuit breaker on the side of the high-voltage side, TA2 is the current transformer of the circuit breaker in the middle of the high-voltage side, TA3 is the current transformer of the high-voltage side bushing, TA4 is the current transformer of the common winding, TA5 is the current transformer of the low-voltage side winding, TA6 is the current transformer of the circuit breaker of the 1st branch on the low-voltage side, TA7 is the current transformer of the circuit breaker of the 2nd branch on the low-voltage side, TA8 is the current transformer of the medium-voltage side, TV1 is the voltage transformer of the high-voltage side, TV2 is the voltage transformer of the medium-voltage side, TV3 is the voltage transformer of the 1st branch on the low-voltage side, and TV4 is the voltage transformer of the 2nd branch on the low-voltage side.

[0065] It should be noted that for steps 103 and 104, the fault confirmation mechanism can be specifically set according to the application scenario and requirements. For example, in order to improve the accuracy of open-circuit fault discrimination, it can be determined that there is an open-circuit fault only when at least two discrimination methods both discriminate that there is an open-circuit fault; for example, when both H1 and H3 discriminate that there is an open-circuit fault on the high-voltage side, it is determined that there is an open-circuit fault on the high-voltage side, and then the subsequent open-circuit fault handling operations are performed to avoid misjudgment caused by an error in a certain open-circuit fault discrimination method, resulting in incorrect handling. Of course, in some scenarios, if it is necessary to ensure that no fault is missed, it can be determined that there is an open-circuit fault as long as any one of the discrimination methods discriminates that there is an open-circuit fault, and then the corresponding open-circuit fault handling operations are performed.

[0066] Emergency trip buttons can also be separately provided on the high-voltage side and the medium-voltage side. After obtaining permission from the dispatcher, the corresponding emergency trip button can be quickly pressed to activate the high-power retrigger relay in the main transformer non-electrical protection cabinet. The normally open contacts of the high-power retrigger relay are connected to the main transformer non-electrical protection, enabling the main transformer non-electrical protection to trip, completing the emergency trip function, that is, tripping the circuit breakers on the three sides of the main transformer to cut off the main transformer open-circuit fault.

[0067] In one embodiment, the present invention also provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed in a computer, the computer is made to execute the data calculation and processing process in the above-mentioned embodiment, such as performing logical judgment processing, etc.

[0068] In one embodiment, the present invention also provides a computing device, including a memory and a processor. An executable code is stored in the memory. When the processor executes the executable code, the data calculation and processing process in the above-mentioned embodiment is implemented, such as logical judgment processing, etc.

[0069] In summary, the method for discriminating and disposing of open-circuit faults of large oil-immersed power transformers provided by the embodiments of the present invention has at least the following beneficial effects:

[0070] (1) Since the existing main transformer protection does not have good sensitivity to open-circuit faults under low-load conditions, such as during the displacement and fall of the bushing during the bushing fracture process, combustion, explosion, etc. will occur, seriously affecting the safe and stable operation of the substation equipment. The method of this patent can provide strong guarantee for the safe and stable operation of large oil-immersed transformers and avoid serious accidents of large transformer damage.

[0071] (2) In the event background involved in this patent, it takes about 3 hours from the signal reporting to the maintenance personnel discovering the fault point, and the fault disposal efficiency is very low. Through the implementation of this patent, the fault discovery time can be shortened to about 10 minutes, shortening the fault disposal time and improving the fault disposal efficiency.

[0072] (3) The implementation of this patent can greatly shorten the open-circuit fault disposal time of large oil-immersed power transformers, providing reliable support and guarantee for the safe and stable operation of large oil-immersed power transformers.

[0073] The modules or units in the device of the embodiments of the present invention can be combined, divided, and deleted according to actual needs. The above-disclosed is only the preferred embodiment of the present invention, and of course, it cannot be used to limit the scope of the rights of the present invention. Those of ordinary skill in the art can understand the implementation of all or part of the above processes and the equivalent changes made according to the claims of the present invention still fall within the scope covered by the invention.

Claims

1. A method for discriminating and disposing of open - circuit faults in a large oil - immersed power transformer, characterized in that, Including: For the high-voltage side of the main transformer, four discrimination methods H1 to H4 are respectively used to discriminate whether a disconnection fault occurs on the high-voltage side of the main transformer. Among them, H1 is discriminated through the power D5000 system, H2 is discriminated by comparing the measured values of the bushing current and the sum current on the high-voltage side, H3 is discriminated according to the zero-sequence current of the high-voltage side bushing, and H4 is discriminated through the main transformer fault recorder; For the medium-voltage side of the main transformer, two discrimination methods M1 to M2 are respectively used to discriminate whether a disconnection fault occurs on the medium-voltage side of the main transformer. Among them, M1 is discriminated through the main transformer fault recorder, and M2 is discriminated according to the measured value of the medium-voltage side current of the main transformer; If at least one discrimination method discriminates that there is a disconnection fault on the high-voltage side of the main transformer, a one-key sequence control is performed using the first operation sequence to trip the circuit breakers on the three sides of the main transformer; If at least one discrimination method discriminates that there is a disconnection fault on the medium-voltage side of the main transformer, a one-key sequence control is performed using the second operation sequence to trip the circuit breakers on the three sides of the main transformer.

2. The method for judging and disposing the broken wire fault of the large oil-immersed power transformer according to claim 1, characterized in that, The discrimination method of the above H1 includes: Using the monitoring function of the power D5000 system, an alarm function for the over-limit of the zero-sequence current on the high-voltage side of the 750 kV main transformer and an alarm function for the single-phase operation on the high-voltage side of the 750 kV main transformer are added; Among them, the discrimination logic for the over-limit of the zero-sequence current on the high-voltage side of the 750 kV main transformer is: according to the three-phase measured currents on the high-voltage side of the main transformer uploaded by the substation side, the zero-sequence current is calculated on the master station side; and when n times of the calculated zero-sequence current is greater than the first preset current value, it is determined that there is a disconnection fault, and an alarm is issued after a delay of the first preset duration; The discrimination logic for the single-phase operation on the high-voltage side of the 750 kV main transformer is: when the current of each phase on the high-voltage side is greater than the first preset current value and the power on the high-voltage side is greater than the first preset power value, the operating state of the main transformer is judged; if the current of any one phase on the high-voltage side suddenly becomes 0, it is determined that a disconnection fault occurs on the high-voltage side of the main transformer.

3. The method for judging and disposing of the broken wire fault of the large oil-immersed power transformer according to claim 1, characterized in that, The discrimination method of the above H2 includes: Comparing the measured values of the bushing current and the sum current on the high-voltage side of the main transformer; if the current of a certain phase of the bushing current and the sum current on the high-voltage side becomes 0, it is determined that a disconnection fault occurs in this phase.

4. The method for judging and handling the broken wire fault of the large oil-immersed power transformer according to claim 1, characterized in that, The discrimination method of the above H3 includes: The three-phase currents of the high-voltage side bushing form a self-produced zero-sequence current through the main transformer body measurement and control loop in series, and the self-produced zero-sequence current is sent to the background monitoring, and the zero-sequence current threshold is set as the second preset current value; when the background monitors that the zero-sequence current is greater than the second preset current value, it is determined that a disconnection fault occurs, and an over-limit alarm of the current is issued.

5. The method for discriminating and disposing of open-circuit faults of a large oil-immersed power transformer according to claim 1, wherein, The discrimination method of the above H4 includes: Using the main station fault recorder to collect the bushing current on the high-voltage side; if the current of a certain phase drops to 0 and the currents of the other two phases are normal, then check the bushing current on the medium-voltage side; if the zero-sequence current component is contained in the bushing current on the medium-voltage side, it is determined that a primary disconnection fault occurs on the high-voltage side, and if there is no zero-sequence current component in the bushing current on the medium-voltage side, it is determined that a secondary disconnection fault occurs on the high-voltage side.

6. The method for judging and disposing of the open-circuit fault of the large oil-immersed power transformer according to claim 1, wherein, The discrimination method of the above M1 includes: Monitor the current of the medium-voltage side bushing using the main transformer fault recorder; if the current of a certain phase of the medium-voltage side bushing drops to 0 while the currents of the other two phases are normal, further check the current of the high-voltage side bushing; if the current of the high-voltage side bushing contains a zero-sequence current component, it is determined that a primary open-circuit fault has occurred on the medium-voltage side; if the current of the high-voltage side bushing does not contain a zero-sequence current component, it is determined that a secondary open-circuit fault has occurred on the medium-voltage side.

7. The method for judging and disposing the open-circuit fault of the large oil-immersed power transformer according to claim 1, wherein, The discrimination method of M2 includes: Monitor the current of the medium-voltage side bushing through the main transformer fault recorder; if the current of a certain phase of the medium-voltage side bushing recorded by the main transformer fault recorder drops to 0, check the remote measurement value of the main transformer medium-voltage side current sent by the medium-voltage side circuit breaker in the post-day monitoring; if the phase current corresponding to this medium-voltage side circuit breaker also drops to 0, it is determined that an open-circuit fault has occurred on the medium-voltage side.

8. The method for judging and disposing of the open-circuit fault of the large oil-immersed power transformer according to claim 1, wherein, The first operation sequence is: trip the 750 kV high-voltage side middle circuit breaker, trip the 750 kV high-voltage side side circuit breaker, trip the 220 kV medium-voltage side circuit breaker, trip the low-voltage side 1 branch circuit breaker, trip the low-voltage side 2 branch circuit breaker; The second operation sequence is: trip the 220 kV medium-voltage side circuit breaker, trip the 750 kV high-voltage side middle circuit breaker, trip the 750 kV high-voltage side side circuit breaker, trip the low-voltage side 1 branch circuit breaker, trip the low-voltage side 2 branch circuit breaker.

9. The method for judging and disposing the open-circuit fault of the large oil-immersed power transformer according to claim 1, characterized in that, The discrimination method for determining whether there is an open-circuit fault on the high-voltage side of the main transformer also includes H5, and the discrimination method for determining whether there is an open-circuit fault on the medium-voltage side of the main transformer also includes M3; among them, both H5 and M3 are used to discriminate open-circuit faults through the open-circuit monitoring device; If at least one of the discrimination methods of H1~H5 discriminates that there is an open-circuit fault on the high-voltage side of the main transformer, perform one-key sequence control using the first operation sequence to trip the circuit breakers on the three sides of the main transformer; If at least one of the discrimination methods of M1~M3 discriminates that there is an open-circuit fault on the medium-voltage side of the main transformer, perform one-key sequence control using the second operation sequence to trip the circuit breakers on the three sides of the main transformer.

10. The method for judging and disposing of the open-circuit fault of a large oil-immersed power transformer according to claim 9, wherein, The open-circuit monitoring device is a microcomputer transformer protection device of the WBH-800 series.

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