A fast transformer protection method and system using sampled values

Abstract

The application discloses a kind of quick transformer protection method and system using sampling value, wherein the method comprises: according to the sudden change variable sampling value of each side current of transformer, the sudden change variable differential current and sudden change variable virtual differential current of transformer are calculated;Based on the sudden change variable differential current and sudden change variable virtual differential current, constitute sudden change variable sampling value inrush blocking criterion;Based on the sudden change variable differential current, constitute sudden change variable sampling value differential protection;Differential current is determined, and based on the differential current, constitute developing fault release inrush blocking criterion;Based on the sudden change variable sampling value inrush blocking criterion and inrush blocking criterion, transformer sampling value differential protection timing.

Description

Technical Field

[0001] This invention relates to the field of electrical technology, and more specifically, to a fast transformer protection method and system utilizing sampled values. Background Technology

[0002] As crucial equipment in power plants and substations, the safe operation of power transformers directly impacts the continuous and stable operation of the entire power system. Inrush current, a unique electromagnetic phenomenon in transformers, can reach 4 to 8 times the normal operating current and is a major source of maloperation in transformer differential protection. Therefore, transformer differential protection typically requires inrush current blocking as a criterion for operation. Currently, transformer differential protection suffers from problems such as maloperation due to inrush current when operating on fault-free transformers and insufficient sensitivity to short circuits between small turns. Summary of the Invention

[0003] According to the present invention, a fast transformer protection method and system utilizing sampled values ​​are provided to solve the technical problems of current transformer differential protection, such as false tripping due to inrush current in fault-free transformers and insufficient sensitivity for short circuits between small turns of the transformer.

[0004] According to a first aspect of the present invention, a fast transformer protection method utilizing sampled values ​​is provided, comprising:

[0005] Based on the sampled values ​​of the sudden change in current on each side of the transformer, calculate the sudden change differential current and the sudden change virtual differential current of the transformer.

[0006] Based on the aforementioned differential current and virtual differential current of the sudden change, a surge current blocking criterion for the sampled value of the sudden change is constructed;

[0007] Based on the aforementioned abrupt change differential current, a differential protection system based on the abrupt change sample value is constructed.

[0008] Determine the differential current, and construct a criterion for releasing inrush current blocking in the event of a progressive fault based on the differential current;

[0009] Based on the inrush current blocking criterion and the inrush current blocking criterion of the aforementioned mutation value sampling value, the timing sequence of the transformer sampling value differential speed protection is determined.

[0010] Optionally, based on the sampled values ​​of the abrupt changes in current on each side of the transformer, the abrupt change differential current and the abrupt change virtual differential current of the transformer are calculated, including:

[0011] Calculate the three-phase differential current of the transformer using the following formula:

[0012]

[0013] Calculate the virtual differential current of the three-phase sudden change in the transformer using the following formula:

[0014]

[0015] In the formula, , , This refers to the differential current, which is a sudden change in the three-phase flow of the transformer. , , This represents the virtual differential current for the three-phase sudden changes in the transformer. , , These are sampled values ​​of the sudden changes in three-phase current on the Y0 side of the transformer. , , The sampled values ​​of the sudden changes in three-phase current on the Δ side of the transformer after transformation ratio adjustment.

[0016] Optionally, based on the abrupt differential current and the abrupt virtual differential current, an inrush current blocking criterion for the abrupt sample value is constructed, including:

[0017] The following formula constitutes the surge blockage criterion for the sampled value of the mutation amount:

[0018]

[0019] In the formula, Startup time up to the current moment interval The maximum value; Startup time up to the current moment interval The maximum value; n is the number of integration points at the current time; This is the transformer's rated current. ; Set a threshold value.

[0020] Optionally, based on the abrupt change differential current, a differential protection system for the abrupt change sample value is constructed, including:

[0021] Convert multi-sided differential into two-sided differential;

[0022] If the transformer is a multi-sided transformer , , These are the sampled current values ​​of the sudden change in voltage on the high-voltage side, medium-voltage side, and low-voltage side, after transformation ratio adjustment and Δ / Y0 adjustment, respectively. For each sampling point, the maximum current is... for Based on the corresponding sampled values, the remaining currents are determined according to the abrupt change in differential current and the maximum current. ;

[0023] If the transformer is a two-sided transformer. , If the sampled values ​​of the sudden change in current on the high-voltage side and the low-voltage side are respectively converted by the transformer ratio and Δ / Y0, then no conversion is required, and the current on either side can be set to the maximum value current;

[0024] The differential protection plane for sudden change sampling values ​​is composed of the maximum current and the remaining currents;

[0025] like ,but , ;otherwise , ;

[0026] The differential protection plane of the sudden change sampling value is divided into three zones: Zone I for internal faults, Zone II for external faults, and Zone III for external saturation. The division of the three zones is determined by two straight lines.

[0027]

[0028]

[0029] In the formula, , Integrals for x and y, respectively;

[0030] Integrate point by point over x and y, and determine In a planar position, if it enters Zone I, the differential protection will activate; if it enters Zone II, it will continue to integrate until one power frequency cycle T; if it enters Zone III, it will stop integrating and lock out the differential protection.

[0031] Optionally, a differential current is determined, and a criterion for releasing inrush current blocking due to a progressive fault is constructed based on the differential current, including:

[0032] The current time is t, and the range for generating the unlocking current is: The differential protection start time is Generate a floating threshold range as .

[0033] The method for calculating the differential current is as follows:

[0034]

[0035] In the formula, This refers to the transformer differential current. , , These are the sampled current values ​​of the high-voltage side, medium-voltage side, and low-voltage side after transformation ratio conversion and Δ / Y0 conversion, respectively.

[0036] Based on the differential current, the criterion for releasing the inrush current blockade due to a developing transformer fault is determined as follows:

[0037]

[0038] In the formula, To unlock the current; A floating threshold; This is used to generate the integral result of the differential current sampling values ​​within the unlocking current range; n is the number of calculation points within the unlocking current range.

[0039] Optionally, based on the inrush current blocking criterion and the inrush current blocking criterion of the abrupt change sample value, the transformer sample value differential instantaneous overcurrent protection timing includes:

[0040] Within the first power frequency cycle T after the differential protection is started, the differential protection criterion for sudden change sample value and the inrush current blocking criterion for sudden change sample value are calculated. If the differential protection criterion for sudden change sample value meets the condition and the inrush current blocking criterion does not meet the condition, the transformer protection will operate.

[0041] Within the second power frequency cycle T after the differential protection is started, the criteria for releasing the inrush current blockade due to the developmental fault are calculated. If the criteria for releasing the inrush current blockade are met, the transformer differential protection is opened.

[0042] According to another aspect of the present invention, a fast transformer protection system utilizing sampled values ​​is also provided, comprising:

[0043] The differential current and virtual differential current calculation module is used to calculate the abrupt differential current and abrupt virtual differential current of the transformer based on the sampled values ​​of the abrupt changes in the current on each side of the transformer.

[0044] A surge current blocking criterion module is constructed to construct a surge current blocking criterion based on the surge current differential current and the surge current virtual differential current.

[0045] The differential protection module is used to construct differential protection based on the abrupt differential current.

[0046] The inrush current unlocking criterion module is used to determine the differential current and construct a progressive fault inrush current unlocking criterion based on the differential current.

[0047] The instantaneous overcurrent protection timing module is used to determine the transformer sample value differential instantaneous overcurrent protection timing based on the inrush current blocking criterion and the inrush current blocking criterion of the sudden change sample value.

[0048] Optionally, the module for calculating differential current and virtual differential current includes:

[0049] The differential current calculation submodule is used to calculate the three-phase differential current of the transformer according to the following formula:

[0050]

[0051] The virtual differential current calculation submodule is used to calculate the three-phase abrupt change in virtual differential current of the transformer according to the following formula:

[0052]

[0053] In the formula, , , This refers to the differential current, which is a sudden change in the three-phase flow of the transformer. , , This represents the virtual differential current for the three-phase sudden changes in the transformer. , , These are sampled values ​​of the sudden changes in three-phase current on the Y0 side of the transformer. , , The sampled values ​​of the sudden changes in three-phase current on the Δ side of the transformer after transformation ratio adjustment.

[0054] Optionally, the inrush blocking criterion module includes:

[0055] A surge blocking criterion submodule is constructed to generate a surge blocking criterion based on the abrupt change sample value according to the following formula:

[0056]

[0057] In the formula, Startup time up to the current moment interval The maximum value; Startup time up to the current moment interval The maximum value; n is the number of integration points at the current time; This is the transformer's rated current. ; Set a threshold value.

[0058] Optionally, the differential protection module includes:

[0059] The differential conversion submodule is used to convert multi-sided differential into two-sided differential;

[0060] Determine the remaining current submodules for use if the transformer is a multi-sided transformer. , , These are the sampled current values ​​of the sudden change in voltage on the high-voltage side, medium-voltage side, and low-voltage side, after transformation ratio adjustment and Δ / Y0 adjustment, respectively. For each sampling point, the maximum current is... for Based on the corresponding sampled values, the remaining currents are determined according to the abrupt change in differential current and the maximum current. ;

[0061] The maximum current determination submodule is used when the transformer is a two-sided transformer. , If the sampled values ​​of the sudden change in current on the high-voltage side and the low-voltage side are respectively converted by the transformer ratio and Δ / Y0, then no conversion is required, and the current on either side can be set to the maximum value current;

[0062] This constitutes a differential protection plane submodule, used to form a differential protection plane with a sudden change sampling value composed of the maximum current and the remaining currents;

[0063] like ,but , ;otherwise , ;

[0064] The region submodule is used to divide the differential protection plane of the sudden change sampling value into three regions: fault zone I, fault zone II, and saturation zone III. The division of the three regions is determined by two straight lines.

[0065]

[0066]

[0067] In the formula, , Integrals for x and y, respectively;

[0068] The interlocking differential protection submodule is used to perform point-by-point integration of x and y to determine... In a planar position, if it enters Zone I, the differential protection will activate; if it enters Zone II, it will continue to integrate until one power frequency cycle T; if it enters Zone III, it will stop integrating and lock out the differential protection.

[0069] Optionally, the inrush blockage release criterion module includes:

[0070] The differential current generation submodule is used to generate the unlocking current range at the current time t. The differential protection start time is Generate a floating threshold range as .

[0071] The differential current submodule is defined, and the calculation method for the differential current is as follows:

[0072]

[0073] In the formula, This refers to the transformer differential current. , , These are the sampled current values ​​of the high-voltage side, medium-voltage side, and low-voltage side after transformation ratio conversion and Δ / Y0 conversion, respectively.

[0074] The inrush current release criterion submodule is used to determine the inrush current release criterion for transformer progressive faults based on the differential current:

[0075]

[0076] In the formula, To unlock the current; A floating threshold; This is used to generate the integral result of the differential current sampling values ​​within the unlocking current range; n is the number of calculation points within the unlocking current range.

[0077] Optionally, based on the inrush current blocking criterion and the inrush current blocking criterion of the abrupt change sample value, the transformer sample value differential instantaneous overcurrent protection timing includes:

[0078] Within the first power frequency cycle T after the differential protection is started, the differential protection criterion for sudden change sample value and the inrush current blocking criterion for sudden change sample value are calculated. If the differential protection criterion for sudden change sample value meets the condition and the inrush current blocking criterion does not meet the condition, the transformer protection will operate.

[0079] Within the second power frequency cycle T after the differential protection is started, the criteria for releasing the inrush current blockade due to the developmental fault are calculated. If the criteria for releasing the inrush current blockade are met, the transformer differential protection is opened.

[0080] Therefore, by utilizing the sampled value of the sudden change in the first power frequency cycle after startup, a differential protection based on the sampled value of the sudden change in the short term is constructed, which is blocked by low-sensitivity inrush current. This allows for the rapid clearing of severe transformer faults. In the second power frequency cycle after startup, a criterion for releasing the inrush current blockage for transformer developmental faults is constructed, which accelerates the opening of transformer inter-turn developmental faults. This ensures the reliability of transformer protection while achieving rapid clearing of transformer faults. Attached Figure Description

[0081] Exemplary embodiments of the present invention can be more fully understood by referring to the following figures:

[0082] Figure 1 This is a flowchart illustrating a fast transformer protection method utilizing sampled values ​​as described in this embodiment.

[0083] Figure 2 This is a schematic diagram of the differential protection of the mutation amount sampling value described in this embodiment;

[0084] Figure 3 This is a timing diagram of the transformer inrush current blocking criterion and unlocking criterion described in this embodiment;

[0085] Figure 4 This is the timing diagram of the differential fast-acting overcurrent protection of the transformer sampling value described in this embodiment;

[0086] Figure 5 (A, B, C) is a schematic diagram of the fault protection operation results in the transformer area described in this embodiment, including... Figure 5A A schematic diagram of the differential protection action results for phase A sudden change. Figure 5B The sampling value of the A-phase mutation amount inrush flow blocking criterion action result, Figure 5C The action result of the criterion for releasing the inrush blockage due to the progressive fault in phase A;

[0087] Figure 6 (A, B, C) is a schematic diagram of the inrush current operation during transformer no-load charging as described in this embodiment, including... Figure 6A A schematic diagram of the differential protection action results for phase A sudden change. Figure 6B The sampling value of the A-phase mutation amount inrush flow blocking criterion action result, Figure 6C The action result of the criterion for releasing the inrush blockage due to the progressive fault in phase A;

[0088] Figure 7 (A, B, C) is a schematic diagram of the fault protection operation results in the transformer area described in this embodiment, including... Figure 7A A schematic diagram of the differential protection action results for phase B sudden change. Figure 7B The sampling value of the B-phase mutation amount inrush blockage criterion action result, Figure 7C The results of the action to resolve the inrush blockage criterion for the C-phase progressive fault;

[0089] Figure 8 This is a schematic diagram of a fast transformer protection system utilizing sampled values ​​as described in this embodiment. Detailed Implementation

[0090] Exemplary embodiments of the invention will now be described with reference to the accompanying drawings. However, the invention may be embodied in many different forms and is not limited to the embodiments described herein. These embodiments are provided to fully and completely disclose the invention and to fully convey its scope to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the drawings is not intended to limit the invention. In the drawings, the same units / elements are referred to by the same reference numerals.

[0091] Unless otherwise stated, the terms used herein (including technical terms) have their common meaning as understood by one of ordinary skill in the art. Furthermore, it is understood that terms defined in commonly used dictionaries should be understood to have a meaning consistent with the context of their relevant field, and not to be interpreted as having an idealized or overly formal meaning.

[0092] According to a first aspect of the present invention, a flowchart 100 of a fast transformer protection method utilizing sampled values ​​is provided, with reference to... Figure 1 As shown, the method 100 includes:

[0093] S101: Calculate the differential current and virtual differential current of the transformer based on the sampled values ​​of the sudden change in current on each side of the transformer.

[0094] S102: Based on the aforementioned differential current and virtual differential current of the sudden change, a surge current blocking criterion for the sampled value of the sudden change is constructed;

[0095] S103: Based on the aforementioned differential current of the sudden change, a differential protection based on the sampled value of the sudden change is constructed;

[0096] S104: Determine the differential current and construct a criterion for releasing inrush current blocking due to a progressive fault based on the differential current;

[0097] S105: Based on the inrush current blocking criterion and the inrush current blocking criterion of the aforementioned mutation value sampling value, the timing sequence of the transformer sampling value differential speed protection.

[0098] Specifically, the method consists of the following steps.

[0099] (1) Calculate the transformer differential current and the transformer virtual differential current by using the abrupt change of the current sampling values ​​on each side of the transformer.

[0100] Taking the transformer as an example, the calculation is performed from the Δ side to the Y0 side.

[0101] Method for calculating differential current with sudden changes:

[0102] (1)

[0103] Method for calculating the virtual differential flow of mutation:

[0104] (2)

[0105] In the formula: , , This refers to the differential current, which is a sudden change in the three-phase flow of the transformer. , , This represents the virtual differential current for the three-phase sudden changes in the transformer. , , These are sampled values ​​of the sudden changes in three-phase current on the Y0 side of the transformer. , , The sampled values ​​of the sudden changes in three-phase current on the Δ side of the transformer after transformation ratio adjustment.

[0106] (2) The surge current blocking criterion is composed of differential current and virtual differential current.

[0107] (3)

[0108] In the formula: Startup time up to the current moment interval The maximum value; Startup time up to the current moment interval The maximum value; n is the number of integration points at the current time; This is the transformer's rated current. ; Set a threshold value.

[0109] (3) The sampled current constitutes the differential protection of the sudden change sampled value.

[0110] Converting multi-sided differential to two-sided differential, if the transformer is a multi-sided transformer. , , These are the sampled current values ​​of the sudden changes on the high-voltage side, medium-voltage side, and low-voltage side, after transformation ratio adjustment and Δ / Y0 adjustment, respectively. For each sampling point, the maximum current is... for The corresponding sampled value, the remaining current If the transformer is a two-sided transformer, , If the sampled current values ​​of the sudden change are the high-voltage side and the low-voltage side after transformation ratio conversion and Δ / Y0 conversion respectively, then no conversion is required, and the current on either side can be set to the maximum value current.

[0111] The differential protection plane for sudden change sampling values ​​is composed of the maximum current and the remaining currents.

[0112] like ,but , ;otherwise , .

[0113] The differential protection plane of the sudden change sampling value is divided into three zones: Zone I for internal faults, Zone II for external faults, and Zone III for external saturation. The division of these three zones is determined by two straight lines.

[0114] (3)

[0115] (4)

[0116] In the formula: , The integrals are x and y, respectively.

[0117] refer to Figure 2 As shown, perform point-by-point integration on x and y, and determine... In a planar position, if it enters Zone I, the differential protection will activate; if it enters Zone II, it will continue to integrate until one power frequency cycle T; if it enters Zone III, it will stop integrating and lock out the differential protection.

[0118] (4) Criteria for releasing inrush current blockage due to differential current.

[0119] refer to Figure 3 As shown, the current time is t, and the range for generating the unlocking current is... The differential protection start time is Generate a floating threshold range as .

[0120] Differential current calculation method:

[0121]

[0122] In the formula: This refers to the transformer differential current. , , These are the sampled current values ​​after transformation ratio conversion and Δ / Y0 conversion for the high-voltage side, medium-voltage side, and low-voltage side, respectively.

[0123] The criterion for clearing inrush current blockade in transformers with progressive faults is as follows:

[0124] (5)

[0125] In the formula: To unlock the current; A floating threshold; This is used to generate the integral result of the differential current sampling values ​​within the unlocking current range; n is the number of calculation points within the unlocking current range.

[0126] (5) Timing sequence of differential overcurrent protection for transformer sampling values.

[0127] 1) Reference Figure 4As shown, within the first power frequency cycle T after the differential protection is started, the differential protection criterion for sudden change sample value and the inrush current blocking criterion for sudden change sample value are calculated. If the differential protection criterion for sudden change sample value meets the condition and the inrush current blocking criterion does not meet the condition, then the transformer protection will operate.

[0128] 2) Within the second power frequency cycle T after the differential protection is started, calculate the criteria for releasing the inrush current blockade due to the developmental fault. If the criteria for releasing the inrush current blockade are met, the transformer differential protection is immediately opened.

[0129] The specific implementations selected the following scenarios:

[0130] (1) Implementation example of applying it to faults in transformer areas

[0131] A single-phase ground fault occurred inside the transformer, and the faulty phase was phase A. The differential protection for the sudden change in phase A operated as follows: Figure 5A As shown, the fault zone I was entered 1.67ms after the fault was initiated. The inrush current blocking criterion action result of the A-phase sudden change sampling value is as follows: Figure 5B As shown, the criterion was met 15.83ms after the fault started, the sudden change differential protection was activated, and the transformer differential protection operated. The result of the inrush current blocking criterion action for the A-phase progressive fault is as follows. Figure 5C As shown, this fault had no development process. After the fault started, the inrush current blocking criterion for the developmental fault was never met. However, the inrush current blocking criterion for the sudden change value had already been judged as an intra-zone fault. Therefore, it did not affect the correct operation of the transformer protection.

[0132] (2) Example of applying the application to transformers with inrush current during no-load charging

[0133] When an inrush current occurs during transformer no-load charging, the differential protection operation result for phase A sudden change is as follows: Figure 6A As shown, after the fault is initiated, it remains in fault zone II outside the zone. The sampling value of the abrupt change in phase A and the result of the inrush blockage criterion are as follows: Figure 6B As shown, the surge blockade criterion for the sudden change in the sampled value is consistently not met after the fault is initiated. The result of the surge blockade criterion action for the phase A progressive fault is as follows: Figure 6C As shown, the criteria for resolving the inrush current blockade due to the developing fault were consistently not met after the fault was initiated. Therefore, the transformer differential protection did not operate.

[0134] (3) Implementation examples of application to transformer progressive faults

[0135] A single-phase ground fault occurred inside the transformer. The faulty phase was phase B. The differential protection for the sudden change in phase B operated as follows: Figure 7A As shown, after the fault is initiated, it enters fault zone I within the zone 9.375ms. The sampling value of the phase change in phase B and the result of the inrush blockage criterion are as follows: Figure 7BAs shown, the criteria for triggering the fault were consistently not met after the fault was initiated. The result of the triggering of the inrush blockage release criterion for the B-phase progressive fault is as follows: Figure 7C As shown, the inrush current blocking criterion for the developmental fault is satisfied 20ms after the fault starts. In summary, the transformer protection operates correctly within 20ms.

[0136] Therefore, by utilizing the sampled value of the sudden change in the first power frequency cycle after startup, a differential protection system with low-sensitivity inrush current blocking is constructed to quickly clear severe transformer faults. In the second power frequency cycle after startup, a criterion for releasing the inrush current blocking for developing transformer faults is established, accelerating the opening of inter-turn developing faults. This ensures the reliability of transformer protection while achieving rapid fault clearing.

[0137] Optionally, based on the sampled values ​​of the abrupt changes in current on each side of the transformer, the abrupt change differential current and the abrupt change virtual differential current of the transformer are calculated, including:

[0138] Calculate the three-phase differential current of the transformer using the following formula:

[0139]

[0140] Calculate the virtual differential current of the three-phase sudden change in the transformer using the following formula:

[0141]

[0142] In the formula, , , This refers to the differential current, which is a sudden change in the three-phase flow of the transformer. , , This represents the virtual differential current for the three-phase sudden changes in the transformer. , , These are sampled values ​​of the sudden changes in three-phase current on the Y0 side of the transformer. , , The sampled values ​​of the sudden changes in three-phase current on the Δ side of the transformer after transformation ratio adjustment.

[0143] Optionally, based on the abrupt differential current and the abrupt virtual differential current, an inrush current blocking criterion for the abrupt sample value is constructed, including:

[0144] The following formula constitutes the surge blockage criterion for the sampled value of the mutation amount:

[0145]

[0146] In the formula, Startup time up to the current moment interval The maximum value; Startup time up to the current moment interval The maximum value; n is the number of integration points at the current time; This is the transformer's rated current. ; Set a threshold value.

[0147] Optionally, based on the abrupt change differential current, a differential protection system for the abrupt change sample value is constructed, including:

[0148] Convert multi-sided differential into two-sided differential;

[0149] If the transformer is a multi-sided transformer , , These are the sampled current values ​​of the sudden change in voltage on the high-voltage side, medium-voltage side, and low-voltage side, after transformation ratio adjustment and Δ / Y0 adjustment, respectively. For each sampling point, the maximum current is... for Based on the corresponding sampled values, the remaining currents are determined according to the abrupt change in differential current and the maximum current. ;

[0150] If the transformer is a two-sided transformer. , If the sampled values ​​of the sudden change in current on the high-voltage side and the low-voltage side are respectively converted by the transformer ratio and Δ / Y0, then no conversion is required, and the current on either side can be set to the maximum value current;

[0151] The differential protection plane for sudden change sampling values ​​is composed of the maximum current and the remaining currents;

[0152] like ,but , ;otherwise , ;

[0153] The differential protection plane of the sudden change sampling value is divided into three zones: Zone I for internal faults, Zone II for external faults, and Zone III for external saturation. The division of the three zones is determined by two straight lines.

[0154]

[0155]

[0156] In the formula, , Integrals for x and y, respectively;

[0157] Integrate point by point over x and y, and determine In a planar position, if it enters Zone I, the differential protection will activate; if it enters Zone II, it will continue to integrate until one power frequency cycle T; if it enters Zone III, it will stop integrating and lock out the differential protection.

[0158] Optionally, a differential current is determined, and a criterion for releasing inrush current blocking due to a progressive fault is constructed based on the differential current, including:

[0159] The current time is t, and the range for generating the unlocking current is: The differential protection start time is Generate a floating threshold range as .

[0160] The method for calculating the differential current is as follows:

[0161]

[0162] In the formula, This refers to the transformer differential current. , , These are the sampled current values ​​of the high-voltage side, medium-voltage side, and low-voltage side after transformation ratio conversion and Δ / Y0 conversion, respectively.

[0163] Based on the differential current, the criterion for releasing the inrush current blockade due to a developing transformer fault is determined as follows:

[0164]

[0165] In the formula, To unlock the current; A floating threshold; This is used to generate the integral result of the differential current sampling values ​​within the unlocking current range; n is the number of calculation points within the unlocking current range.

[0166] Optionally, based on the inrush current blocking criterion and the inrush current blocking criterion of the abrupt change sample value, the transformer sample value differential instantaneous overcurrent protection timing includes:

[0167] Within the first power frequency cycle T after the differential protection is started, the differential protection criterion for sudden change sample value and the inrush current blocking criterion for sudden change sample value are calculated. If the differential protection criterion for sudden change sample value meets the condition and the inrush current blocking criterion does not meet the condition, the transformer protection will operate.

[0168] Within the second power frequency cycle T after the differential protection is started, the criteria for releasing the inrush current blockade due to the developmental fault are calculated. If the criteria for releasing the inrush current blockade are met, the transformer differential protection is opened.

[0169] Therefore, by utilizing the sampled value of the sudden change in the first power frequency cycle after startup, a differential protection based on the sampled value of the sudden change in the short term is constructed, which is blocked by low-sensitivity inrush current. This allows for the rapid clearing of severe transformer faults. In the second power frequency cycle after startup, a criterion for releasing the inrush current blockage for transformer developmental faults is constructed, which accelerates the opening of transformer inter-turn developmental faults. This ensures the reliability of transformer protection while achieving rapid clearing of transformer faults.

[0170] According to another aspect of the invention, a fast transformer protection system 800 utilizing sampled values ​​is also provided, with reference to... Figure 8 As shown, the system 800 includes:

[0171] The differential current and virtual differential current calculation module 810 is used to calculate the differential current and virtual differential current of the transformer based on the sampled values ​​of the sudden change in current on each side of the transformer.

[0172] A surge current blocking criterion module 820 is configured to construct a surge current blocking criterion based on the surge current differential current and the surge current virtual differential current.

[0173] Differential protection module 830 is used to construct differential protection based on the sudden change differential current;

[0174] The inrush current blocking release criterion module 840 is used to determine the differential current and construct a progressive fault inrush current blocking release criterion based on the differential current.

[0175] The instantaneous overcurrent protection timing module 850 is used to determine the instantaneous overcurrent protection timing based on the inrush current blocking criterion and the inrush current blocking criterion of the transient quantity sampling value.

[0176] Optionally, the module for calculating differential current and virtual differential current includes:

[0177] The differential current calculation submodule is used to calculate the three-phase differential current of the transformer according to the following formula:

[0178]

[0179] The virtual differential current calculation submodule is used to calculate the three-phase abrupt change in virtual differential current of the transformer according to the following formula:

[0180]

[0181] In the formula, , , This refers to the differential current, which is a sudden change in the three-phase flow of the transformer. , , This represents the virtual differential current for the three-phase sudden changes in the transformer. , , These are sampled values ​​of the sudden changes in three-phase current on the Y0 side of the transformer. , , The sampled values ​​of the sudden changes in three-phase current on the Δ side of the transformer after transformation ratio adjustment.

[0182] Optionally, the inrush blocking criterion module includes:

[0183] A surge blocking criterion submodule is constructed to generate a surge blocking criterion based on the abrupt change sample value according to the following formula:

[0184]

[0185] In the formula, Startup time up to the current moment interval The maximum value; Startup time up to the current moment interval The maximum value; n is the number of integration points at the current time; This is the transformer's rated current. ; Set a threshold value.

[0186] Optionally, the differential protection module includes:

[0187] The differential conversion submodule is used to convert multi-sided differential into two-sided differential;

[0188] Determine the remaining current submodules for use if the transformer is a multi-sided transformer. , , These are the sampled current values ​​of the sudden change in voltage on the high-voltage side, medium-voltage side, and low-voltage side, after transformation ratio adjustment and Δ / Y0 adjustment, respectively. For each sampling point, the maximum current is... for Based on the corresponding sampled values, the remaining currents are determined according to the abrupt change in differential current and the maximum current. ;

[0189] The maximum current determination submodule is used when the transformer is a two-sided transformer. , If the sampled values ​​of the sudden change in current on the high-voltage side and the low-voltage side are respectively converted by the transformer ratio and Δ / Y0, then no conversion is required, and the current on either side can be set to the maximum value current;

[0190] This constitutes a differential protection plane submodule, used to form a differential protection plane with a sudden change sampling value composed of the maximum current and the remaining currents;

[0191] like ,but , ;otherwise , ;

[0192] The region submodule is used to divide the differential protection plane of the sudden change sampling value into three regions: fault zone I, fault zone II, and saturation zone III. The division of the three regions is determined by two straight lines.

[0193]

[0194]

[0195] In the formula, , Integrals for x and y, respectively;

[0196] The interlocking differential protection submodule is used to perform point-by-point integration of x and y to determine... In a planar position, if it enters Zone I, the differential protection will activate; if it enters Zone II, it will continue to integrate until one power frequency cycle T; if it enters Zone III, it will stop integrating and lock out the differential protection.

[0197] Optionally, the inrush blockage release criterion module includes:

[0198] The differential current generation submodule is used to generate the unlocking current range at the current time t. The differential protection start time is Generate a floating threshold range as .

[0199] The differential current submodule is defined, and the calculation method for the differential current is as follows:

[0200]

[0201] In the formula, This refers to the transformer differential current. , , These are the sampled current values ​​of the high-voltage side, medium-voltage side, and low-voltage side after transformation ratio conversion and Δ / Y0 conversion, respectively.

[0202] The inrush current release criterion submodule is used to determine the inrush current release criterion for transformer progressive faults based on the differential current:

[0203]

[0204] In the formula, To unlock the current; A floating threshold; This is used to generate the integral result of the differential current sampling values ​​within the unlocking current range; n is the number of calculation points within the unlocking current range.

[0205] Optionally, based on the inrush current blocking criterion and the inrush current blocking criterion of the abrupt change sample value, the transformer sample value differential instantaneous overcurrent protection timing includes:

[0206] Within the first power frequency cycle T after the differential protection is started, the differential protection criterion for sudden change sample value and the inrush current blocking criterion for sudden change sample value are calculated. If the differential protection criterion for sudden change sample value meets the condition and the inrush current blocking criterion does not meet the condition, the transformer protection will operate.

[0207] Within the second power frequency cycle T after the differential protection is started, the criteria for releasing the inrush current blockade due to the developmental fault are calculated. If the criteria for releasing the inrush current blockade are met, the transformer differential protection is opened.

[0208] The fast transformer protection system 800 utilizing sampled values ​​in one embodiment of the present invention corresponds to the fast transformer protection method 100 utilizing sampled values ​​in another embodiment of the present invention, and will not be described again here.

[0209] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code. The solutions in the embodiments of this application can be implemented in various computer languages, such as the object-oriented programming language Java and the interpreted scripting language JavaScript.

[0210] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0211] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0212] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0213] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0214] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A fast transformer protection method utilizing sampled values, characterized in that, include: Based on the sampled values ​​of the sudden change in current on each side of the transformer, calculate the sudden change differential current and the sudden change virtual differential current of the transformer. Based on the aforementioned differential current and virtual differential current of the sudden change, a surge current blocking criterion for the sampled value of the sudden change is constructed; Based on the aforementioned abrupt change differential current, a differential protection system based on the abrupt change sample value is constructed. Determine the differential current, and construct a criterion for releasing inrush current blocking in the event of a progressive fault based on the differential current; Based on the inrush current blocking criterion and the inrush current blocking criterion of the aforementioned mutation value sampling value, the timing judgment of the transformer sampling value differential speed protection is performed. Based on the aforementioned abrupt change differential current, a differential protection system with sampled abrupt change value is constructed, comprising: Convert multi-sided differential into two-sided differential; If the transformer is a multi-sided transformer , , These are the sampled current values ​​of the sudden change in voltage on the high-voltage side, medium-voltage side, and low-voltage side, after transformation ratio adjustment and Δ / Y0 adjustment, respectively. For each sampling point, the maximum current is... for Based on the corresponding sampled values, the remaining currents are determined according to the abrupt change in differential current and the maximum current. ; If the transformer is a two-sided transformer. , If the sampled values ​​of the sudden change in current on the high-voltage side and the low-voltage side are respectively converted by the transformer ratio and Δ / Y0, then no conversion is required, and the current on either side can be set to the maximum value current; The differential protection plane for sudden change sampling values ​​is composed of the maximum current and the remaining currents; like ,but , ;otherwise , ; The differential protection plane of the sudden change sampling value is divided into three zones: Zone I for internal faults, Zone II for external faults, and Zone III for external saturation. The division of the three zones is determined by two straight lines. In the formula, , Integrals for x and y, respectively; Integrate point by point over x and y, and determine In the plane position, if it enters zone I, the differential protection will activate; if it enters zone II, it will continue to integrate until one power frequency cycle T; if it enters zone III, it will stop integrating and lock out the differential protection. Based on the aforementioned surge current blocking criterion and surge current blocking criterion of the sampled value, the transformer sampled value differential instantaneous overcurrent protection timing sequence includes: Within the first power frequency cycle T after the differential protection is started, the differential protection criterion for sudden change sample value and the inrush current blocking criterion for sudden change sample value are calculated. If the differential protection criterion for sudden change sample value meets the condition and the inrush current blocking criterion does not meet the condition, the transformer protection will operate. Within the second power frequency cycle T after the differential protection is started, the criteria for releasing the inrush current blockade due to the developmental fault are calculated. If the criteria for releasing the inrush current blockade are met, the transformer differential protection is opened.

2. The method according to claim 1, characterized in that, Based on the sampled values ​​of the sudden changes in current on each side of the transformer, calculate the sudden change differential current and the sudden change virtual differential current of the transformer, including: Calculate the three-phase differential current of the transformer using the following formula: Calculate the virtual differential current of the three-phase sudden change in the transformer using the following formula: In the formula, , , This refers to the differential current, which is a sudden change in the three-phase flow of the transformer. , , This represents the virtual differential current for the three-phase sudden changes in the transformer. , , These are sampled values ​​of the sudden changes in three-phase current on the Y0 side of the transformer. , , The sampled values ​​of the sudden changes in three-phase current on the Δ side of the transformer after transformation ratio adjustment.

3. The method according to claim 1, characterized in that, Based on the aforementioned differential current and virtual differential current of the sudden change, a surge current blocking criterion for the sampled value of the sudden change is constructed, including: The following formula constitutes the surge blockage criterion for the sampled value of the mutation amount: In the formula, Startup time up to the current moment interval The maximum value; Startup time up to the current moment interval The maximum value; n is the number of integration points at the current time; This is the transformer's rated current. ; Set a threshold value.

4. The method according to claim 1, characterized in that, Determine the differential current, and based on the differential current, construct a criterion for releasing inrush current blocking in the event of a developing fault, including: The current time is t, and the range for generating the unlocking current is: The differential protection start time is Generate a floating threshold range as ; The method for calculating the differential current is as follows: In the formula, This refers to the transformer differential current. , , These are the sampled current values ​​of the high-voltage side, medium-voltage side, and low-voltage side after transformation ratio conversion and Δ / Y0 conversion, respectively. Based on the differential current, the criterion for releasing the inrush current blockade due to a developing transformer fault is determined as follows: In the formula, To unlock the current; A floating threshold; This is used to generate the integral result of the differential current sampling values ​​within the unlocking current range; n is the number of calculation points within the unlocking current range.

5. A fast transformer protection system utilizing sampled values, characterized in that, include: The differential current and virtual differential current calculation module is used to calculate the abrupt differential current and abrupt virtual differential current of the transformer based on the sampled values ​​of the abrupt changes in the current on each side of the transformer. A surge current blocking criterion module is constructed to construct a surge current blocking criterion based on the surge current differential current and the surge current virtual differential current. The differential protection module is used to construct differential protection based on the abrupt differential current. The inrush current unlocking criterion module is used to determine the differential current and construct a progressive fault inrush current unlocking criterion based on the differential current. The instantaneous overcurrent protection timing module is used to perform transformer sample value differential instantaneous overcurrent protection timing judgment based on the inrush current blocking criterion and the inrush current blocking criterion of the sudden change sample value. Differential protection module, including: The differential conversion submodule is used to convert multi-sided differential into two-sided differential; Determine the remaining current submodules for use if the transformer is a multi-sided transformer. , , These are the sampled current values ​​of the sudden change in voltage on the high-voltage side, medium-voltage side, and low-voltage side, after transformation ratio adjustment and Δ / Y0 adjustment, respectively. For each sampling point, the maximum current is... for Based on the corresponding sampled values, the remaining currents are determined according to the abrupt change in differential current and the maximum current. ; The maximum current determination submodule is used when the transformer is a two-sided transformer. , If the sampled values ​​of the sudden change in current on the high-voltage side and the low-voltage side are respectively converted by the transformer ratio and Δ / Y0, then no conversion is required, and the current on either side can be set to the maximum value current; This constitutes a differential protection plane submodule, used to form a differential protection plane with a sudden change sampling value composed of the maximum current and the remaining currents; like ,but , ;otherwise , ; The region submodule is used to divide the differential protection plane of the sudden change sampling value into three regions: fault zone I, fault zone II, and saturation zone III. The division of the three regions is determined by two straight lines. In the formula, , Integrals for x and y, respectively; The interlocking differential protection submodule is used to perform point-by-point integration of x and y to determine... In the plane position, if it enters zone I, the differential protection will activate; if it enters zone II, it will continue to integrate until one power frequency cycle T; if it enters zone III, it will stop integrating and lock out the differential protection. Based on the aforementioned surge current blocking criterion and surge current blocking criterion of the sampled value, the transformer sampled value differential instantaneous overcurrent protection timing sequence includes: Within the first power frequency cycle T after the differential protection is started, the differential protection criterion for sudden change sample value and the inrush current blocking criterion for sudden change sample value are calculated. If the differential protection criterion for sudden change sample value meets the condition and the inrush current blocking criterion does not meet the condition, the transformer protection will operate. Within the second power frequency cycle T after the differential protection is started, the criteria for releasing the inrush current blockade due to the developmental fault are calculated. If the criteria for releasing the inrush current blockade are met, the transformer differential protection is opened.

6. The system according to claim 5, characterized in that, The module for calculating differential current and virtual differential current includes: The differential current calculation submodule is used to calculate the three-phase differential current of the transformer according to the following formula: The virtual differential current calculation submodule is used to calculate the three-phase abrupt change in virtual differential current of the transformer according to the following formula: In the formula, , , This refers to the differential current, which is a sudden change in the three-phase flow of the transformer. , , This represents the virtual differential current for the three-phase sudden changes in the transformer. , , These are sampled values ​​of the sudden changes in three-phase current on the Y0 side of the transformer. , , The sampled values ​​of the sudden changes in three-phase current on the Δ side of the transformer after transformation ratio adjustment.

7. The system according to claim 5, characterized in that, The inrush blocking criterion module comprises: A surge blocking criterion submodule is constructed to generate a surge blocking criterion based on the abrupt change sample value according to the following formula: In the formula, Startup time up to the current moment interval The maximum value; Startup time up to the current moment interval The maximum value; n is the number of integration points at the current time; This is the transformer's rated current. ; Set a threshold value.

8. The system according to claim 5, characterized in that, The inrush release criterion module includes: The differential current generation submodule is used to generate the unlocking current range at the current time t. The differential protection start time is Generate a floating threshold range as ; The differential current submodule is defined, and the calculation method for the differential current is as follows: In the formula, This refers to the transformer differential current. , , These are the sampled current values ​​of the high-voltage side, medium-voltage side, and low-voltage side after transformation ratio conversion and Δ / Y0 conversion, respectively. The inrush current release criterion submodule is used to determine the inrush current release criterion for transformer progressive faults based on the differential current: In the formula, To unlock the current; A floating threshold; This is used to generate the integral result of the differential current sampling values ​​within the unlocking current range; n is the number of calculation points within the unlocking current range.

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