Differential protection method and device for single-core symmetrical phase-shifting transformer

Abstract

The invention provides a single-core symmetric phase-shifting transformer differential protection method and device, and belongs to the technical field of transformer differential protection. The method comprises the following steps: acquiring currents of the input side and the output side of each phase of voltage regulating winding of the single-core symmetrical phase-shifting transformer and currents of each phase of excitation winding of the single-core symmetrical phase-shifting transformer; determining the electric balance differential current of each phase based on the current balance relation of the single-core symmetrical phase-shifting transformer, and setting an electric balance differential protection setting value to obtain an electric balance differential protection criterion; determining the magnetic balance differential current of each phase based on the magnetic circuit coupling relationship of the single-core symmetrical phase-shifting transformer, and setting a magnetic balance differential protection setting value to obtain a magnetic balance differential protection criterion; and the electric balance differential protection criterion and the magnetic balance differential protection criterion jointly form a differential protection criterion of the single-core symmetric phase-shifting transformer, and differential protection is performed on the single-core symmetric phase-shifting transformer. According to the invention, differential protection can be carried out on the single-core symmetric phase-shifting transformer.

Description

Technical Field

[0001] The present invention relates to the technical field of transformer differential protection, and in particular to a single-core symmetrical phase-shifting transformer differential protection method and device. Background Art

[0002] With the development of the power system, the grid structure has become increasingly complex. It has become a huge system that includes multiple types of power sources, multiple types of loads, equipment of different voltage levels, and AC / DC hybrid. This has put forward higher requirements for the reliable and economical operation of the power grid. In the power system, if no control method is adopted, the power flow of the power system will be distributed inversely proportional to the impedance, that is, the natural distribution of power. The natural distribution of power may lead to unreasonable distribution of line flow, affecting the safety and economy of power supply of the power system. Therefore, it is necessary to use flow control to adjust the power transmitted by the line.

[0003] As a power flow regulating device, the single-core phase-shifting transformer can adjust the phase of the current and voltage of the transmission line, thereby regulating the power flow of the line. Based on its magnetic circuit structure, the single-core phase-shifting transformer is composed of a voltage regulating winding and an excitation winding connected by a circuit. The three-phase voltage regulating winding is connected in series to the system, and the three-phase excitation winding is connected in an angle shape. The two ends of the excitation winding of one phase are respectively connected to the lead-out terminals of the midpoints of the other two-phase voltage regulating windings. The phase-shifting transformer has two operating modes: leading and lagging. The operating mode can be switched by adjusting the polarity converter on the voltage regulating winding. The size of the phase shift angle can be changed by adjusting several gears on the voltage regulating winding (i.e., changing the number of turns of the voltage regulating winding connected to the system).

[0004] The differential protection configuration of a single-core phase-shifting transformer is closely related to its primary structure. Compared with conventional transformers, its structure is complex. Therefore, the installation position and number of current transformers are limited by the compact primary structure of the phase-shifting transformer, which affects the engineering configuration and implementation of differential protection. Summary of the invention

[0005] The embodiments of the present invention provide a single-core symmetrical phase-shifting transformer differential protection method and device to solve the problem of performing differential protection on the single-core symmetrical phase-shifting transformer.

[0006] In a first aspect, an embodiment of the present invention provides a single-core symmetrical phase-shifting transformer differential protection method, comprising:

[0007] Obtain the currents at the input and output sides of each phase voltage regulating winding of the single-core symmetrical phase-shifting transformer, as well as the currents of each phase excitation winding;

[0008] Based on the current balance relationship of the single-core symmetrical phase-shifting transformer, the electric balance differential current of each phase is determined, the setting value of the electric balance differential protection is set, and the electric balance differential protection criterion is obtained;

[0009] Based on the magnetic circuit coupling relationship of the single-core symmetrical phase-shifting transformer, the magnetic balance differential current of each phase is determined, the magnetic balance differential protection setting value is set, and the magnetic balance differential protection criterion is obtained;

[0010] The electric balance differential protection criterion and the magnetic balance differential protection criterion are combined to form the differential protection criterion of the single-core symmetrical phase-shifting transformer, and the single-core symmetrical phase-shifting transformer is differentially protected.

[0011] In a possible implementation, the excitation winding of the single-core symmetrical phase-shifting transformer is delta-connected and has a direct circuit connection with the voltage regulating winding; the current balance relationship of the single-core symmetrical phase-shifting transformer includes:

[0012] The current relationship equation between the voltage regulating winding and the excitation winding is:

[0013]

[0014] in, is the input side current of the A-phase voltage regulating winding, is the output side current of the A-phase voltage regulating winding, is the input side current of the B-phase voltage regulating winding, is the output side current of the B-phase voltage regulating winding, is the input side current of the C-phase voltage regulating winding, is the output side current of the C-phase voltage regulating winding, is the current flowing into the same-name end of the A-phase excitation winding, is the current flowing into the same-name end of the B-phase excitation winding, is the current flowing into the same-name end of the C-phase excitation winding;

[0015] Electrically balanced differential current when an internal fault occurs The expression is:

[0016]

[0017] in, is the electrical balance differential current of phase A, is the electrical balance differential current of phase B, is the C phase electrical balance differential current.

[0018] In a possible implementation, the electric balance differential protection criterion is:

[0019]

[0020] Among them, I set1 It is the setting value of electric balance differential protection;

[0021] Differential protection for single-core symmetrical phase-shifting transformers, including:

[0022] If the electric balance differential protection criterion is met, the electric balance differential protection will operate, otherwise it will not operate.

[0023] In a possible implementation, the magnetic circuit coupling relationship of the single-core symmetrical phase-shifting transformer includes:

[0024] The flux balance equation of the excitation winding and the voltage regulating winding is:

[0025]

[0026] Among them, k S is the turns ratio of the voltage regulating winding, is the input side current of the A-phase voltage regulating winding, is the output side current of the A-phase voltage regulating winding, is the input side current of the B-phase voltage regulating winding, is the output side current of the B-phase voltage regulating winding, is the input side current of the C-phase voltage regulating winding, is the output side current of the C-phase voltage regulating winding, is the current flowing into the same-name end of the A-phase excitation winding, is the current flowing into the same-name end of the B-phase excitation winding, is the current flowing into the same-name end of the C-phase excitation winding;

[0027] The expression of magnetic balance differential current when an internal fault occurs is:

[0028]

[0029]

[0030] in, is the magnetic balance differential current of phase A, is the magnetic balance differential current of phase B, is the C-phase magnetic balance differential current.

[0031] In a possible implementation, differential protection is performed on a single-core symmetrical phase-shifting transformer, including:

[0032] Ratio brake differential protection is used for magnetic balance differential protection.

[0033] In a possible implementation, the action equation of the magnetic balance differential protection is:

[0034]

[0035] Among them, I opA is the A phase operating current, I opB is the B phase operating current, I opCis the C phase operating current, I resA is the braking current of phase A, I resV is the braking current of phase B, I resC is the braking current of phase C;

[0036] The magnetic balance differential protection criterion is:

[0037]

[0038] Among them, I op is the operating current of magnetic balance differential protection, I op.0 is the minimum operating current of magnetic balance differential protection, I res is the braking current, I res.g is the inflection point current of magnetic balance differential protection, K is the braking coefficient;

[0039] Differential protection for single-core symmetrical phase-shifting transformers, including:

[0040] If the magnetic balance differential protection criterion is met, the magnetic balance differential protection will operate, otherwise it will not operate.

[0041] In a possible implementation, the method further includes:

[0042] When adjusting the gear position, the number of turns of the voltage regulating winding is updated.

[0043] In a possible implementation, obtaining the currents at the input side and the output side of each phase voltage regulating winding of a single-core symmetrical phase-shifting transformer and the current of each phase excitation winding includes:

[0044] The currents at the input and output sides of the voltage regulating windings of each phase of the single-core symmetrical phase-shifting transformer and the currents of the excitation windings of each phase are obtained based on the current transformer.

[0045] In a second aspect, an embodiment of the present invention provides a single-core symmetrical phase-shifting transformer differential protection device, comprising:

[0046] A current measurement module is used to obtain the current on the input side and output side of each phase voltage regulating winding of the single-core symmetrical phase-shifting transformer, as well as the current of each phase excitation winding;

[0047] An electric balance criterion forming module is used to determine the electric balance differential current of each phase based on the current balance relationship of the single-core symmetrical phase-shifting transformer, set the electric balance differential protection setting value, and obtain the electric balance differential protection criterion;

[0048] A magnetic balance criterion forming module is used to determine the magnetic balance differential current of each phase based on the magnetic circuit coupling relationship of the single-core symmetrical phase-shifting transformer, set the magnetic balance differential protection setting value, and obtain the magnetic balance differential protection criterion;

[0049] The protection action module is used to combine the electric balance differential protection criterion and the magnetic balance differential protection criterion to form the differential protection criterion of the single-core symmetrical phase-shifting transformer, and perform differential protection on the single-core symmetrical phase-shifting transformer.

[0050] The embodiment of the present invention provides a single-core symmetrical phase-shifting transformer differential protection method and device. On the basis of analyzing the magnetic circuit structure of the single-core symmetrical phase-shifting transformer, the protection scheme of the single-core symmetrical phase-shifting transformer is established according to Kirchhoff's current law, the law of electromagnetic induction, etc. By analyzing the normal operation of the phase-shifting transformer and the difference between the fault outside the occurrence zone and the fault inside the occurrence zone, an electric balance protection scheme and a magnetic balance protection scheme are constructed. The current on the input and output sides of the phase-shifting transformer and the current on the excitation winding are collected. When the phase-to-phase and turn-to-turn faults occur in the phase-shifting transformer, the protection can reliably operate to cut off the fault, thereby realizing the differential protection of the single-core symmetrical phase-shifting transformer. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0052] Figure 1 This is an application scenario diagram of a single-core symmetrical phase-shifting transformer differential protection method provided by an embodiment of the present invention;

[0053] Figure 2 It is a flow chart of the implementation of the single-core symmetrical phase-shifting transformer differential protection method provided by the embodiment of the present invention;

[0054] Figure 3 It is a structural schematic diagram of a single-core symmetrical phase-shifting transformer differential protection device provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0055] In the following description, specific details such as specific system structures, technologies, etc. are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present invention. However, it should be clear to those skilled in the art that the present invention may be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to prevent unnecessary details from obstructing the description of the present invention.

[0056] In order to make the purpose, technical solutions and advantages of the present invention more clear, specific embodiments will be described below in conjunction with the accompanying drawings.

[0057] Figure 1This is an application scenario diagram of the single-core symmetrical phase-shifting transformer differential protection method provided by the embodiment of the present invention. Figure 1 As shown, ports S and L are the input and output sides of the single-core phase-shifting transformer, and current transformers CT1A, CT2A, CT3A, CT1B, CT2B, CT3B, CT1C, CT2C and CT3C are used to collect the input and output currents of the voltage regulating winding respectively. in, and They are the input and output currents of the A-phase voltage regulating winding respectively; and They are the input and output currents of the B-phase voltage regulating winding respectively; and They are the input and output currents of the C-phase voltage regulating winding respectively; is the current flowing into the same-name end of the A-phase excitation winding; is the current flowing into the same-name end of the B-phase excitation winding; is the current flowing into the same-name end of the C-phase excitation winding.

[0058] The real-time gear information (the ratio of the number of turns of the phase-shifting transformer voltage regulating winding actually connected to the grid to the number of turns of the excitation winding during gear adjustment) and the collected current are input into the microcomputer differential protection device; the microcomputer differential protection device is divided into two parts: electric balance differential protection KD1 and magnetic balance differential protection KD2, which are used to construct and calculate the differential current respectively. and I opA ,I opB and I opC , to construct the single-core symmetrical phase-shifting transformer body protection action criterion, and finally output a signal command; the circuit breaker tripping coil is used to receive the command output by the microcomputer protection device and control the protection action according to the command.

[0059] Figure 2 The implementation flow chart of the single-core symmetrical phase-shifting transformer differential protection method provided by the embodiment of the present invention is described in detail as follows:

[0060] Step 201, obtaining the currents at the input side and the output side of the voltage regulating winding of each phase of the single-core symmetrical phase-shifting transformer, and the currents of the excitation winding of each phase.

[0061] In this embodiment, current transformers are respectively configured on the input side and output side of the three-phase voltage regulating winding of the single-core symmetrical phase-shifting transformer, which are denoted as CT1A, CT2A, CT1B, CT2B, CT1C, and CT2C, and current transformers are respectively configured on the three-phase excitation winding, which are denoted as CT3A, CT3B, and CT3C. There are 9 CTs in total.

[0062] The current transformer collects the current on the input side and the output side of each phase voltage regulating winding and the current of each phase excitation winding when the single-core symmetrical phase-shifting transformer is in normal operation, so as to perform differential protection.

[0063] Step 202, based on the current balance relationship of the single-core symmetrical phase-shifting transformer, determine the electric balance differential current of each phase, set the electric balance differential protection setting value, and obtain the electric balance differential protection criterion.

[0064] In this embodiment, the electric balance differential protection reflects the phase-to-phase faults of the voltage regulating winding and the excitation winding lead wires.

[0065] Step 203, determining the magnetic balance differential current of each phase based on the magnetic circuit coupling relationship of the single-core symmetrical phase-shifting transformer, setting the magnetic balance differential protection setting value, and obtaining the magnetic balance differential protection criterion.

[0066] In this embodiment, the magnetic balance differential protection can reflect the phase-to-phase and turn-to-turn faults of the voltage regulating winding and the excitation winding.

[0067] Step 204: The electric balance differential protection criterion and the magnetic balance differential protection criterion are used together to form a differential protection criterion for the single-core symmetrical phase-shifting transformer, and differential protection is performed on the single-core symmetrical phase-shifting transformer.

[0068] In this embodiment, the single-core symmetrical phase-shifting transformer fault is judged according to the electric balance differential protection and magnetic balance differential protection action criteria. When the action value is greater than the setting value, the protection action condition is met and the protection action module acts reliably. The circuit breaker tripping coil is used to receive the command output by the microcomputer protection device and control the protection action according to the command.

[0069] In a possible implementation, the excitation winding of the single-core symmetrical phase-shifting transformer is delta-connected and has a direct circuit connection with the voltage regulating winding; the current balance relationship of the single-core symmetrical phase-shifting transformer includes:

[0070] The current relationship equation between the voltage regulating winding and the excitation winding is:

[0071]

[0072] in, is the input side current of the A-phase voltage regulating winding, is the output side current of the A-phase voltage regulating winding, is the input side current of the B-phase voltage regulating winding, is the output side current of the B-phase voltage regulating winding, is the input side current of the C-phase voltage regulating winding, is the output side current of the C-phase voltage regulating winding, is the current flowing into the same-name end of the A-phase excitation winding, is the current flowing into the same-name end of the B-phase excitation winding, is the current flowing into the same-name end of the C-phase excitation winding;

[0073] Electrically balanced differential current when an internal fault occurs The expression is:

[0074]

[0075]

[0076] in, is the electrical balance differential current of phase A, is the electrical balance differential current of phase B, is the C phase electrical balance differential current.

[0077] In this embodiment, current transformers CT1A, CT2A, CT3A, CT1B, CT2B, CT3B, CT1C, CT2C and CT3C are used to collect the input and output currents of the voltage regulating windings, respectively. and They are the input and output currents of the A-phase voltage regulating winding respectively; and They are the input and output currents of the B-phase voltage regulating winding respectively; and They are the input and output currents of the C-phase voltage regulating winding respectively; is the current flowing into the same-name end of the A-phase excitation winding; is the current flowing into the same-name end of the B-phase excitation winding; is the current flowing into the same-name end of the C-phase excitation winding.

[0078] The excitation winding is connected in a delta connection and has a direct circuit connection with the voltage regulating winding. According to Kirchhoff's current law, the current relationship equation between the voltage regulating winding and the excitation winding is written at points a, b, and c to obtain equations (1) to (3).

[0079] When the phase-shifting transformer is operating normally or an external fault occurs, equations (1) to (3) are valid. When an internal fault occurs and the KCL equation no longer holds, the electric balance differential current As shown in formulas (4) to (6).

[0080] In a possible implementation, the electric balance differential protection criterion is:

[0081]

[0082] Among them, I set1 It is the setting value of electric balance differential protection;

[0083] Differential protection for single-core symmetrical phase-shifting transformers, including:

[0084] If the electric balance differential protection criterion is met, the electric balance differential protection will operate, otherwise it will not operate.

[0085] In this embodiment, if the above formula (7) is satisfied, that is, the differential current If one or more phases exceed the set value, the protection will be activated; otherwise, the protection will be locked and will not be activated.

[0086] In a possible implementation, the magnetic circuit coupling relationship of the single-core symmetrical phase-shifting transformer includes:

[0087] The flux balance equation of the excitation winding and the voltage regulating winding is:

[0088]

[0089]

[0090] Among them, k S is the turns ratio of the voltage regulating winding, is the input side current of the A-phase voltage regulating winding, is the output side current of the A-phase voltage regulating winding, is the input side current of the B-phase voltage regulating winding, is the output side current of the B-phase voltage regulating winding, is the input side current of the C-phase voltage regulating winding, is the output side current of the C-phase voltage regulating winding, is the current flowing into the same-name end of the A-phase excitation winding, is the current flowing into the same-name end of the B-phase excitation winding, is the current flowing into the same-name end of the C-phase excitation winding;

[0091] The expression of magnetic balance differential current when an internal fault occurs is:

[0092]

[0093] in, is the magnetic balance differential current of phase A, is the magnetic balance differential current of phase B, is the C-phase magnetic balance differential current.

[0094] In this embodiment, Figure 1 Medium voltage regulating winding A S(1) The number of turns actually connected to the grid and the excitation winding A E The turns ratio is ks / 2, the voltage regulating winding A S(2) The number of turns actually connected to the grid and the excitation winding A E The turns ratio is also ks / 2.

[0095] When the operation is normal or an external fault occurs, equations (8) to (10) are valid. When an internal fault occurs and the magnetic flux balance is destroyed, equations (8) to (10) will no longer be valid.

[0096] In a possible implementation, differential protection is performed on a single-core symmetrical phase-shifting transformer, including:

[0097] Ratio brake differential protection is used for magnetic balance differential protection.

[0098] In this embodiment, the magnetic balance differential protection scheme adopts ratio braking differential protection as the criterion, thereby increasing the sensitivity of the differential protection during faults within the zone and ensuring reliable and non-false operation when faults outside the zone occur.

[0099] In a possible implementation, the action equation of the magnetic balance differential protection is:

[0100]

[0101]

[0102] Among them, I opA is the A phase operating current, I opB is the B phase operating current, I opC is the C phase operating current, I resA is the braking current of phase A, I resB is the braking current of phase B, I resC is the braking current of phase C;

[0103] The magnetic balance differential protection criterion is:

[0104]

[0105] in, is the operating current of magnetic balance differential protection, I op.0 is the minimum operating current of magnetic balance differential protection, is the braking current, I res.g is the inflection point current of magnetic balance differential protection, K is the braking coefficient;

[0106] Differential protection for single-core symmetrical phase-shifting transformers, including:

[0107] If the magnetic balance differential protection criterion is met, the magnetic balance differential protection will operate, otherwise it will not operate.

[0108] In this embodiment, the ratio-brake differential protection is designed to take into account that during normal operation, the parameter characteristics of the current transformers (CTs) on each side of the main transformer are inconsistent, the excitation currents of the CTs are different, and the error in the setting of the protection balance coefficient causes an unbalanced current to pass through the differential circuit, and the unbalanced current may exceed the starting current of the differential current. At the same time, when the differential protection is externally short-circuited (through fault), the short-circuit current on the primary side of the CT contains a large number of non-periodic components that decay with exponential decay. Its decay rate is much lower than that of the periodic component, so it is difficult to transfer to the secondary side of the CT, and it mainly serves as the excitation current of the CT, making the CT core more saturated and the secondary current error larger. This current is also called transient through current. The above two situations can increase the unbalanced current, especially the latter, which is very likely to cause the differential protection to malfunction in the event of a large current fault. Therefore, the braking current is introduced to overcome these shortcomings.

[0109] In a possible implementation, the method further includes:

[0110] When adjusting the gear position, the number of turns of the voltage regulating winding is updated.

[0111] In this embodiment, when the gear is adjusted, the number of turns of the voltage regulating winding connected to the system is updated online to identify the gear information, thereby ensuring that the amount of information in the input magnetic balance differential protection criterion is accurate, thereby ensuring that the protection action module operates reliably and correctly.

[0112] In a possible implementation, obtaining the currents at the input side and the output side of each phase voltage regulating winding of a single-core symmetrical phase-shifting transformer and the current of each phase excitation winding includes:

[0113] The currents at the input and output sides of the voltage regulating windings of each phase of the single-core symmetrical phase-shifting transformer and the currents of the excitation windings of each phase are obtained based on the current transformer.

[0114] In this embodiment, current transformers are respectively provided at the input side and output side of each phase voltage regulating winding and each phase excitation winding of the single-core symmetrical phase-shifting transformer to collect current and calculate differential current.

[0115] From the above, it can be seen that this scheme provides a technical method with engineering practical value for the protection of the body of single-core symmetrical phase-shifting transformers. It not only overcomes the problems of compact internal structure, complex fault characteristics, and difficulty in collecting internal current of single-core phase-shifting transformers, but also only requires one current transformer to be installed in each phase of the angular excitation winding, reducing the number of configured current transformers, which is of great significance to promoting the theoretical research and engineering application of the protection of the body of phase-shifting transformers. It lays a theoretical foundation for further analysis of the protection scheme of phase-shifting transformers with this structure, and has guiding significance in engineering application and promotion.

[0116] It should be understood that the order of execution of the steps in the above embodiment does not necessarily mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiment of the present invention.

[0117] The following is an embodiment of the device of the present invention. For details not described in detail, reference may be made to the corresponding method embodiments described above.

[0118] Figure 3 The structure diagram of the single-core symmetrical phase-shifting transformer differential protection device provided by the embodiment of the present invention is shown. For the convenience of explanation, only the part related to the embodiment of the present invention is shown, which is described in detail as follows:

[0119] like Figure 3 As shown, the single-core symmetrical phase-shifting transformer differential protection device 3 includes:

[0120] The current measurement module 31 is used to obtain the current at the input side and the output side of each phase voltage regulating winding of the single-core symmetrical phase-shifting transformer, as well as the current of each phase excitation winding;

[0121] The electric balance criterion forming module 32 is used to determine the electric balance differential current of each phase based on the current balance relationship of the single-core symmetrical phase-shifting transformer, set the electric balance differential protection setting value, and obtain the electric balance differential protection criterion;

[0122] A magnetic balance criterion forming module 33 is used to determine the magnetic balance differential current of each phase based on the magnetic circuit coupling relationship of the single-core symmetrical phase-shifting transformer, set the magnetic balance differential protection setting value, and obtain the magnetic balance differential protection criterion;

[0123] The protection action module 34 is used to combine the electric balance differential protection criterion and the magnetic balance differential protection criterion to form a differential protection criterion for the single-core symmetrical phase-shifting transformer, and perform differential protection on the single-core symmetrical phase-shifting transformer.

[0124] In a possible implementation, the excitation winding of the single-core symmetrical phase-shifting transformer is delta-connected and has a direct circuit connection with the voltage regulating winding; the current balance relationship of the single-core symmetrical phase-shifting transformer includes:

[0125] The current relationship equation between the voltage regulating winding and the excitation winding is:

[0126]

[0127] in, is the input side current of the A-phase voltage regulating winding, is the output side current of the A-phase voltage regulating winding, is the input side current of the B-phase voltage regulating winding, is the output side current of the B-phase voltage regulating winding, is the input side current of the C-phase voltage regulating winding, is the output side current of the C-phase voltage regulating winding, is the current flowing into the same-name end of the A-phase excitation winding, is the current flowing into the same-name end of the B-phase excitation winding, is the current flowing into the same-name end of the C-phase excitation winding;

[0128] Electrically balanced differential current when an internal fault occurs The expression is:

[0129]

[0130]

[0131] in, is the electrical balance differential current of phase A, is the electrical balance differential current of phase B, is the C phase electrical balance differential current.

[0132] In a possible implementation, the electric balance differential protection criterion is:

[0133]

[0134] Among them, I set1 It is the setting value of electric balance differential protection;

[0135] The protection action module 34 is specifically used for:

[0136] If the electric balance differential protection criterion is met, the electric balance differential protection will operate, otherwise it will not operate.

[0137] In a possible implementation, the magnetic circuit coupling relationship of the single-core symmetrical phase-shifting transformer includes:

[0138] The flux balance equation of the excitation winding and the voltage regulating winding is:

[0139]

[0140] Among them, k S is the turns ratio of the voltage regulating winding, is the input side current of the A-phase voltage regulating winding, is the output side current of the A-phase voltage regulating winding, is the input side current of the B-phase voltage regulating winding, is the output side current of the B-phase voltage regulating winding, is the input side current of the C-phase voltage regulating winding, is the output side current of the C-phase voltage regulating winding, is the current flowing into the same-name end of the A-phase excitation winding, is the current flowing into the same-name end of the B-phase excitation winding, is the current flowing into the same-name end of the C-phase excitation winding;

[0141] The expression of magnetic balance differential current when an internal fault occurs is:

[0142]

[0143]

[0144] in, is the magnetic balance differential current of phase A, is the magnetic balance differential current of phase B, is the C-phase magnetic balance differential current.

[0145] In a possible implementation, the protection action module 34 is specifically configured to:

[0146] Ratio brake differential protection is used for magnetic balance differential protection.

[0147] In a possible implementation, the action equation of the magnetic balance differential protection is:

[0148]

[0149] Among them, I opA is the A phase operating current, I opB is the B phase operating current, I opC is the C phase operating current, I resA is the braking current of phase A, I resB is the braking current of phase B, I resC is the braking current of phase C;

[0150] The magnetic balance differential protection criterion is:

[0151]

[0152] Among them, I op is the operating current of magnetic balance differential protection, I op.0 is the minimum operating current of magnetic balance differential protection, I res is the braking current, I res.g is the inflection point current of magnetic balance differential protection, K is the braking coefficient;

[0153] The protection action module 34 is specifically used for:

[0154] If the magnetic balance differential protection criterion is met, the magnetic balance differential protection will operate, otherwise it will not operate.

[0155] In a possible implementation, the current measurement module 31 is further used for:

[0156] When adjusting the gear position, the number of turns of the voltage regulating winding is updated.

[0157] In a possible implementation, the current measurement module 31 is specifically used for:

[0158] The currents at the input and output sides of the voltage regulating windings of each phase of the single-core symmetrical phase-shifting transformer and the currents of the excitation windings of each phase are obtained based on the current transformer.

[0159] Based on the analysis of the magnetic circuit structure of the single-core symmetrical phase-shifting transformer, the embodiment of the present invention establishes a protection scheme for the single-core symmetrical phase-shifting transformer according to Kirchhoff's current law, the law of electromagnetic induction, etc., and constructs an electric balance protection scheme and a magnetic balance protection scheme by analyzing the normal operation of the phase-shifting transformer and the difference between the fault outside the occurrence zone and the fault inside the occurrence zone. The current on the input and output sides of the phase-shifting transformer and the current on the excitation winding are collected. When the phase-to-phase and turn-to-turn faults occur in the phase-shifting transformer, the protection can reliably operate to remove the fault, thereby realizing differential protection for the single-core symmetrical phase-shifting transformer.

[0160] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0161] Those of ordinary skill in the art will appreciate that the templates, units, and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0162] If the module / unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the present invention implements all or part of the processes in the above-mentioned embodiment method, and can also be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium. When the computer program is executed by the processor, it can implement the steps of the above-mentioned single-core symmetrical phase-shifting transformer differential protection method embodiments. Among them, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form. The computer-readable medium may include: any entity or device that can carry the computer program code, recording medium, U disk, mobile hard disk, disk, optical disk, computer memory, read-only memory, random access memory, electrical carrier signal, telecommunication signal and software distribution medium.

[0163] The embodiments described above are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included in the protection scope of the present invention.

Claims

1. A single-core symmetrical phase-shifting transformer differential protection method, characterized in that: include: Obtain the currents at the input and output sides of each phase voltage regulating winding of the single-core symmetrical phase-shifting transformer, as well as the currents of each phase excitation winding; Based on the current balance relationship of the single-core symmetrical phase-shifting transformer, the electric balance differential current of each phase is determined, the electric balance differential protection setting value is set, and the electric balance differential protection criterion is obtained; Based on the magnetic circuit coupling relationship of the single-core symmetrical phase-shifting transformer, the magnetic balance differential current of each phase is determined, the magnetic balance differential protection setting value is set, and the magnetic balance differential protection criterion is obtained; The electric balance differential protection criterion and the magnetic balance differential protection criterion together constitute the differential protection criterion of the single-core symmetrical phase-shifting transformer, and differential protection is performed on the single-core symmetrical phase-shifting transformer.

2. The single-core symmetrical phase-shifting transformer differential protection method according to claim 1, characterized in that: The excitation winding of the single-core symmetrical phase-shifting transformer is a delta connection and has a direct circuit connection with the voltage regulating winding; the current balance relationship of the single-core symmetrical phase-shifting transformer includes: The current relationship equation between the voltage regulating winding and the excitation winding is: in, is the input side current of the A-phase voltage regulating winding, is the output side current of the A-phase voltage regulating winding, is the input side current of the B-phase voltage regulating winding, is the output side current of the B-phase voltage regulating winding, is the input side current of the C-phase voltage regulating winding, is the output side current of the C-phase voltage regulating winding, is the current flowing into the same-name end of the A-phase excitation winding, is the current flowing into the same-name end of the B-phase excitation winding, is the current flowing into the same-name end of the C-phase excitation winding; Electrically balanced differential current when an internal fault occurs The expression is: in, is the electrical balance differential current of phase A, is the electrical balance differential current of phase B, is the C phase electrical balance differential current.

3. The single-core symmetrical phase-shifting transformer differential protection method according to claim 2 is characterized in that: The electric balance differential protection criterion is: Among them, I set1 It is the setting value of electric balance differential protection; The differential protection of the single-core symmetrical phase-shifting transformer comprises: If the electric balance differential protection criterion is met, the electric balance differential protection will be activated, otherwise it will not be activated.

4. The single-core symmetrical phase-shifting transformer differential protection method according to claim 1, characterized in that: The magnetic circuit coupling relationship of the single-core symmetrical phase-shifting transformer includes: The flux balance equation of the excitation winding and the voltage regulating winding is: Among them, k S is the turns ratio of the voltage regulating winding, is the input side current of the A-phase voltage regulating winding, is the output side current of the A-phase voltage regulating winding, is the input side current of the B-phase voltage regulating winding, is the output side current of the B-phase voltage regulating winding, is the input side current of the C-phase voltage regulating winding, is the output side current of the C-phase voltage regulating winding, is the current flowing into the same-name end of the A-phase excitation winding, is the current flowing into the same-name end of the B-phase excitation winding, is the current flowing into the same-name end of the C-phase excitation winding; The expression of magnetic balance differential current when an internal fault occurs is: in, is the magnetic balance differential current of phase A, is the magnetic balance differential current of phase B, is the C-phase magnetic balance differential current.

5. The single-core symmetrical phase-shifting transformer differential protection method according to claim 4, characterized in that: The differential protection of the single-core symmetrical phase-shifting transformer comprises: Ratio brake differential protection is used for magnetic balance differential protection.

6. The single-core symmetrical phase-shifting transformer differential protection method according to claim 5, characterized in that: The action equation of the magnetic balance differential protection is: Among them, I opA is the A phase operating current, I opB is the B phase operating current, I opC is the C phase operating current, I resA is the braking current of phase A, I resB is the braking current of phase B, I resC is the braking current of phase C; The magnetic balance differential protection criterion is: Among them, I op is the operating current of magnetic balance differential protection, I op.0 is the minimum operating current of magnetic balance differential protection, I res is the braking current, I res.g is the inflection point current of magnetic balance differential protection, K is the braking coefficient; The differential protection of the single-core symmetrical phase-shifting transformer comprises: If the magnetic balance differential protection criterion is met, the magnetic balance differential protection is activated, otherwise it is not activated.

7. The single-core symmetrical phase-shifting transformer differential protection method according to claim 4, characterized in that: Also includes: When adjusting the gear position, the number of turns of the voltage regulating winding is updated.

8. The single-core symmetrical phase-shifting transformer differential protection method according to any one of claims 1 to 7, characterized in that: The method of obtaining the currents at the input side and the output side of each phase voltage regulating winding of the single-core symmetrical phase-shifting transformer, as well as the currents of each phase excitation winding, includes: The currents at the input and output sides of the voltage regulating windings of each phase of the single-core symmetrical phase-shifting transformer and the currents of the excitation windings of each phase are obtained based on the current transformer.

9. A single-core symmetrical phase-shifting transformer differential protection device, characterized in that: include: A current measurement module is used to obtain the current on the input and output sides of each phase voltage regulating winding of the single-core symmetrical phase-shifting transformer, as well as the current of each phase excitation winding; An electric balance criterion forming module is used to determine the electric balance differential current of each phase based on the current balance relationship of the single-core symmetrical phase-shifting transformer, set the electric balance differential protection setting value, and obtain the electric balance differential protection criterion; A magnetic balance criterion forming module is used to determine the magnetic balance differential current of each phase based on the magnetic circuit coupling relationship of the single-core symmetrical phase-shifting transformer, set the magnetic balance differential protection setting value, and obtain the magnetic balance differential protection criterion; The protection action module is used to combine the electric balance differential protection criterion and the magnetic balance differential protection criterion to form a differential protection criterion for the single-core symmetrical phase-shifting transformer, and perform differential protection on the single-core symmetrical phase-shifting transformer.

10. The single-core symmetrical phase-shifting transformer differential protection device according to claim 9, characterized in that: The excitation winding of the single-core symmetrical phase-shifting transformer is a delta connection and has a direct circuit connection with the voltage regulating winding; the current balance relationship of the single-core symmetrical phase-shifting transformer includes: The current relationship equation between the voltage regulating winding and the excitation winding is: in, is the input side current of the A-phase voltage regulating winding, is the output side current of the A-phase voltage regulating winding, is the input side current of the B-phase voltage regulating winding, is the output side current of the B-phase voltage regulating winding, is the input side current of the C-phase voltage regulating winding, is the output side current of the C-phase voltage regulating winding, is the current flowing into the same-name end of the A-phase excitation winding, is the current flowing into the same-name end of the B-phase excitation winding, is the current flowing into the same-name end of the C-phase excitation winding; Electrically balanced differential current when an internal fault occurs The expression is: in, is the electrical balance differential current of phase A, is the electrical balance differential current of phase B, is the C phase electrical balance differential current.

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