CN116169638A - Auxiliary judging method for harmonic braking of differential protection of transformer - Google Patents
Auxiliary judging method for harmonic braking of differential protection of transformer Download PDFInfo
- Publication number
- CN116169638A CN116169638A CN202211413196.8A CN202211413196A CN116169638A CN 116169638 A CN116169638 A CN 116169638A CN 202211413196 A CN202211413196 A CN 202211413196A CN 116169638 A CN116169638 A CN 116169638A
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- transformer
- differential protection
- harmonic
- current
- braking
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/04—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for transformers
- H02H7/045—Differential protection of transformers
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
- Y02E40/40—Arrangements for reducing harmonics
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Protection Of Transformers (AREA)
Abstract
The invention discloses an auxiliary judging method for harmonic braking of transformer differential protection. Firstly, extracting the fundamental wave component and the second harmonic component phase of differential current after the differential protection harmonic braking criterion of a transformer is started, calculating the phase difference between the fundamental wave and the second harmonic component, and when the phase difference is 0 0 Or 180 degrees 0 And judging the differential protection of the inrush current locking when the area is exceeded, and judging that the fault unlocking braking criterion protects the outlet action when the area is exceeded. The method can accurately judge the faults occurring when the transformer and the surge current occur, and avoid differential protection refusing or action delay caused by harmonic braking.
Description
Technical field:
the invention belongs to the field of power systems, relates to the technical field of transformer differential protection, and particularly relates to an auxiliary judging method for harmonic braking of transformer differential protection.
The background technology is as follows:
the differential protection is the main protection of the transformer, and because the transformer is a nonlinear ferromagnetic element, no-load input causes abrupt change of terminal voltage, so that the magnetic flux of the iron core is saturated to generate inrush current with large amplitude, thereby meeting the fixed value of differential current operation and protecting misoperation. In order to eliminate the influence of the inrush current on the differential protection, the conventional transformer differential protection constructs a harmonic braking criterion according to the fact that the second harmonic content of the current is larger than the fault current according to the exciting inrush current time difference, and the differential protection is locked by the exciting inrush current when the second harmonic content is larger than a fixed value.
For two transformers of the same transformer substation, when one transformer is put into operation and one transformer is out of operation, when the dead load of the transformer is put into operation, the terminal voltage of the transformer is suddenly changed, so that the magnetic flux of the iron core is saturated, excitation surge current can be generated, and the main transformer which is parallel to the transformer is coupled with the system characteristics to generate the stress surge current with similar properties. The two types of inrush currents alternately appear along with time, and the sum inrush current is slower due to the self attenuation rate, and meanwhile, the excitation inrush current attenuation of the closing transformer is slower. When excitation surge and stress surge are generated, a harmonic braking criterion of the transformer differential protection starts locking differential protection, and the differential protection is ensured not to malfunction. If an internal fault occurs during the differential protection blocking period of the transformer and the emergency current, the second harmonic content is larger than a fixed value, so that the protection blocking cannot act fast, and the fault of the transformer is continuously caused to expand the accident.
The invention comprises the following steps:
in order to solve the problems in the prior art, the invention aims to provide a harmonic braking auxiliary judging method for transformer differential protection, which can accurately judge internal faults occurring during the generation and emergency surge of a transformer, ensure that the transformer differential protection quickly removes fault equipment and reduce the damage degree of the fault equipment.
To achieve the above object, in theory, the phase difference between the fundamental component and the second harmonic component of the differential current during the inrush is 0 ° or 180 °, and the phase difference is in the region of 0 ° ± β or 180 ° ± β, taking into account the effects of the inrush-attenuating direct current component and the sampling error. If the phase difference between the fundamental component and the second harmonic component of the differential current changes after the transformer fails during the inrush current, the phase difference leaves the 0 degree + -beta or 180 degree + -beta area, and according to the characteristics, the invention adopts the following technical scheme:
(1) after the harmonic braking of the transformer differential protection starts locking protection, the phase difference theta of the fundamental component and the second harmonic component of the differential current is calculated 12 ；
(2) If beta > theta 12 > -beta or 180 DEG +beta > theta 12 Judging that the current is more than 180-beta and returning after the current is equal to the surge current or the exciting surge current; if the fault is not judged to occur, unlocking the braking criterion and protecting the action of the outlet.
The method of the invention needs to extract the phase of the fundamental wave component and the second harmonic wave component of the differential current of the transformer after the differential protection harmonic braking criterion is started, calculate the phase difference between the fundamental wave component and the second harmonic wave component, add an auxiliary judging method into the harmonic braking criterion, effectively judge the faults occurring during the inrush current according to the phase difference, prevent the harmonic braking criterion from causing the fault action rejection or the delay action, and effectively improve the differential protection action performance of the transformer.
Drawings
FIG. 1 is a flow chart of a method of implementing the invention
FIG. 2 is a schematic diagram of a transformer suitable for use in the method of the present invention
The specific embodiment is as follows:
the invention will be described in further detail with reference to the drawings and examples.
As shown in fig. 1, the invention relates to an auxiliary judging method for harmonic braking of transformer differential protection, which comprises the following steps:
step 1: after the differential protection harmonic braking is started, extracting the phase theta of the fundamental component of the differential current of the protected transformer 1 And second harmonic component phase theta 2 The method comprises the steps of carrying out a first treatment on the surface of the Since the angular frequency of the second harmonic wave is twice different from that of the fundamental wave, the phase difference theta between the fundamental wave and the second harmonic wave 12 It is necessary to calculate twice the fundamental phase and the second harmonic phase, i.e. θ 12 ＝2θ 1 -θ 2
Step 2: discriminating the phase difference region if beta > theta 12 > -beta or 180 DEG +beta > theta 12 Judging that the differential protection is equal to the sum surge current or the excitation surge current and returning to the locking differential protection; if the phase difference changes, the phase difference enters 180 DEG beta > theta 12 > beta or 360 DEG beta > theta 12 The area more than 180 degrees plus beta is judged to be a fault in the inrush current period, unlocking and braking are carried out, and the action of an outlet is protected;
step 3: the phase difference change is caused by the inrush current attenuation direct current component, meanwhile, the phase difference error is caused by the sampling calculation link, the threshold value beta is selected to comprehensively consider the phase difference change, the error and the sensitivity of the protection action, and the sensitivity is set to be 30 degrees.
Examples
As shown in fig. 2, the 110kV transformer substation has two transformers 1# and 2# which are both configured with current differential protection. The following describes the scheme of the present invention with reference to the transformer 1.
The differential protection device of the No. 1 transformer collects three-phase currents at two sides of 110kV and 35kV, and utilizesFourier algorithm for calculating three-phase differential current fundamental wave I 1 ∠θ 1 And second harmonic I 2 ∠θ 2 When differential protection and harmonic braking of the protection device are started, theta is calculated 12 ＝2θ 1 -θ 2 The method comprises the steps of carrying out a first treatment on the surface of the Discriminating theta 12 In the region where beta > theta 12 > -beta or 180 DEG +beta > theta 12 If 180-beta > theta, the differential protection is judged as surge blocking 12 > beta or 360 DEG beta > theta 12 The region > 180 DEG+beta is identified as the fault differential protection action outlet.
By adopting the auxiliary judging scheme for harmonic blocking of the transformer differential protection, the internal faults generated in the period of exciting inrush current/and stress inrush current of the transformer can be effectively judged, and the differential protection action performance of the transformer is improved.
Claims (2)
1. The auxiliary judgment method for the inrush current braking of the differential protection of the transformer is characterized by comprising the following steps of:
(1) after the harmonic braking of the transformer differential protection starts locking protection, the phase difference theta of the fundamental component and the second harmonic component of the differential current is calculated 12 ；
(2) If beta > theta 12 > -beta or 180 DEG +beta > theta 12 Judging that the current is more than 180-beta and returning after the current is equal to the surge current or the exciting surge current; if the fault is not judged to occur, unlocking the braking criterion and protecting the action of the outlet.
2. The method for braking unlocking criteria of differential protection inrush current of a transformer as claimed in claim 1, wherein: the threshold value β is set to 30 °.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211413196.8A CN116169638A (en) | 2022-11-11 | 2022-11-11 | Auxiliary judging method for harmonic braking of differential protection of transformer |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211413196.8A CN116169638A (en) | 2022-11-11 | 2022-11-11 | Auxiliary judging method for harmonic braking of differential protection of transformer |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN116169638A true CN116169638A (en) | 2023-05-26 |
Family
ID=86420728
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202211413196.8A Pending CN116169638A (en) | 2022-11-11 | 2022-11-11 | Auxiliary judging method for harmonic braking of differential protection of transformer |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN116169638A (en) |
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2022
- 2022-11-11 CN CN202211413196.8A patent/CN116169638A/en active Pending
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