CN114594403A - Transformer secondary side short circuit fault discrimination method based on short circuit voltage characteristics - Google Patents
Transformer secondary side short circuit fault discrimination method based on short circuit voltage characteristics Download PDFInfo
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- CN114594403A CN114594403A CN202210140619.7A CN202210140619A CN114594403A CN 114594403 A CN114594403 A CN 114594403A CN 202210140619 A CN202210140619 A CN 202210140619A CN 114594403 A CN114594403 A CN 114594403A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
- G01R31/52—Testing for short-circuits, leakage current or ground faults
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
- G01R31/62—Testing of transformers
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
- G01R31/72—Testing of electric windings
Abstract
The invention relates to a transformer secondary side short-circuit fault distinguishing method based on short-circuit voltage characteristics, and belongs to the technical field of power electronics. The method comprises the following steps: s1: sampling to obtain three-phase voltage of multiple secondary sides of the transformer; s2: comparing the effective difference value of the three-phase voltage with a preset theoretical value by using a comparison unit, and entering S3 if the effective difference value of the three-phase voltage is greater than the preset theoretical value of the voltage; s3: recalculating the three-phase voltage relationship by using a mathematical operation unit; s4: judging whether the three-phase voltage relation meets the voltage characteristic of the short-circuit fault; s5: and when the three-phase voltage is judged to meet the short-circuit voltage condition, prompting the type of the short-circuit fault and tripping the frequency converter in fault. The invention utilizes the comparison of the real-time voltage and the voltage characteristic during short-circuit fault, effectively judges the short-circuit state of the secondary side of the transformer in time and determines the fault type.
Description
Technical Field
The invention belongs to the technical field of power electronics, and relates to a method for judging a secondary short-circuit fault of a transformer based on short-circuit voltage characteristics.
Background
At present, a multi-secondary-side phase-shifting transformer is adopted for supplying power to a power unit, once a secondary side of the transformer is short-circuited, secondary side current is increased sharply, according to magnetic potential balance, secondary side current is in reverse phase with primary side current, and secondary side current has a demagnetization effect on primary side current main magnet.
Therefore, a necessary method is needed to judge the secondary side state of the transformer and timely judge the short-circuit fault state, but the traditional method has the problem that the short-circuit fault of the transformer cannot be found timely.
Disclosure of Invention
In view of the above, the present invention provides a method for determining a short-circuit fault on a secondary side of a transformer based on short-circuit voltage characteristics, which utilizes a comparison between a real-time voltage and a voltage characteristic during a short-circuit fault to determine a short-circuit state of the secondary side of the transformer in time and effectively, thereby defining a fault type.
In order to achieve the purpose, the invention provides the following technical scheme:
a transformer secondary side short-circuit fault distinguishing method based on short-circuit voltage characteristics specifically comprises the following steps:
s1: sampling to obtain three-phase voltage of multiple secondary sides of the transformer;
s2: comparing the effective difference value of the three-phase voltage with a preset theoretical value by using a comparison unit, and entering S3 if the effective difference value of the three-phase voltage is greater than the preset theoretical value of the voltage;
s3: recalculating the three-phase voltage relationship by using a mathematical operation unit, and calculating the mathematical operation relationship between each phase voltage after short circuit and the three-phase voltage average value (the difference value of the three-phase voltage effective values is less than the preset voltage theoretical value) of the satisfied condition in S1 on the basis of analysis and calculation of each phase voltage during short circuit;
s4: judging whether the three-phase voltage relation meets the voltage characteristic of the short-circuit fault;
s5: and when the three-phase voltage is judged to meet the short-circuit voltage condition, prompting the type of the short-circuit fault and tripping the frequency converter in fault.
Further, the step S4 of determining whether the three-phase voltage relationship satisfies the short-circuit fault voltage characteristic includes: and (4) comparing the three-phase voltage relation calculated in the step (S3) with preset voltage theoretical values under different fault types, and if the voltage deviation is within a preset threshold range, judging that the secondary side of the transformer is short-circuited and the frequency converter is tripped due to fault, so that the safety of equipment is ensured, the short-circuit type can be accurately judged, and the subsequent troubleshooting of the fault is facilitated.
Further, in step S4, the short-circuit fault voltage characteristic includes: when the two phases b and c are short-circuited, according to theory and simulation analysis, the amplitude of the fault phase voltage is reduced by about half, and the non-fault phase voltage is approximately equal to the two-phase voltage short-circuit fault characteristic of the voltage before the fault.
Further, in step S4, the short-circuit fault voltage characteristic further includes: based on the voltage change relation during short circuit, single-phase short circuit and three-phase short circuit fault characteristics, but in practical application, two-phase short circuit occurs more, so that two-phase short circuit fault is judged as the highest priority in the fault judgment stage.
Further, in step S4, when determining whether the three-phase voltage relationship satisfies the short-circuit fault voltage characteristic, the strictness of the actual working condition and the logic determination is also considered, that is, the three-phase voltages are compared with the three-phase voltages of each fault type to obtain an average theoretical deviation value, and then the average theoretical deviation value is compared with a preset deviation theoretical value: when the average theoretical deviation value is larger than a preset deviation theoretical value, the fault type is considered to be inconsistent or no fault occurs; and when the average theoretical deviation is less than the preset deviation theoretical value, taking the fault type corresponding to the minimum theoretical deviation item of each fault type as a final result.
The invention has the beneficial effects that: the invention is mainly used for protecting the transformer of the unit cascade type high-voltage frequency converter. The method of the invention judges the two-phase short circuit fault of the secondary side of the transformer in time by detecting the voltage of the secondary side of the transformer and combining the direct current bus voltage and the primary side current of the frequency converter, thereby disconnecting the superior high-voltage switch. The invention mainly solves the problem of great loss of transformer burnout and frequency converter damage caused by untimely judgment when the secondary side of the frequency converter transformer is short-circuited.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the means of the instrumentalities and combinations particularly pointed out hereinafter.
Drawings
For the purposes of promoting a better understanding of the objects, aspects and advantages of the invention, reference will now be made to the following detailed description taken in conjunction with the accompanying drawings in which:
FIG. 1 is a flow chart of a method for judging a secondary side short circuit fault of a transformer based on short circuit voltage characteristics according to the present invention;
fig. 2 is a transformer short-circuit fault determination system in an embodiment.
Detailed Description
The following embodiments of the present invention are provided by way of specific examples, and other advantages and effects of the present invention will be readily apparent to those skilled in the art from the disclosure herein. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention. It should be noted that the drawings provided in the following embodiments are only for illustrating the basic idea of the present invention in a schematic way, and the features in the following embodiments and examples may be combined with each other without conflict.
Wherein the showings are for the purpose of illustrating the invention only and not for the purpose of limiting the same, and in which there is shown by way of illustration only and not in the drawings in which there is no intention to limit the invention thereto; to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of an actual product; it will be understood by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted.
The same or similar reference numerals in the drawings of the embodiments of the present invention correspond to the same or similar components; in the description of the present invention, it should be understood that if there is an orientation or positional relationship indicated by terms such as "upper", "lower", "left", "right", "front", "rear", etc., based on the orientation or positional relationship shown in the drawings, it is only for convenience of description and simplification of description, but it is not an indication or suggestion that the referred device or element must have a specific orientation, be constructed in a specific orientation, and be operated, and therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes, and are not to be construed as limiting the present invention, and the specific meaning of the terms may be understood by those skilled in the art according to specific situations.
Referring to fig. 1 to 2, fig. 1 is a flowchart of a method for determining a secondary short-circuit fault of a transformer according to the present invention, the method includes the following steps:
1) the frequency converter with motor load runs at full speed;
2) the system detects the voltage of each secondary winding of the transformer through a Hall circuit and uploads the voltage to a mathematical operation unit;
3) the mathematical operation unit calculates the actual difference value of the three-phase voltage effective values, obtains the deviation value of the actual difference value and the preset theoretical difference value, and enters a comparison program (namely a comparison unit) when the deviation value is larger than the preset deviation value;
4) the comparison program needs to obtain the comparison relation between the secondary three-phase voltage of the transformer and a preset theoretical value;
5) and comparing the proportional relation between the comprehensive three-phase voltage and a preset theoretical value with a fault judgment condition, and determining the most matched fault type according to the fault deviation.
Example 1:
in the system for judging the short-circuit fault of the transformer adopted in the embodiment, the input side of the frequency converter is connected with a 10kV adjustable power supply, the frequency converter is an 8-level H-bridge unit with 660V secondary side and is cascaded with a high-voltage frequency converter, and the secondary side of the transformer is a 24-winding side.
As shown in fig. 2, taking b and c two-phase short circuit as an example, the logic algorithm for analyzing the discrimination method of the present invention is as follows:
s1: the system detects the voltage of each secondary winding of the transformer through a Hall circuit and uploads the voltage to a mathematical operation unit, if two phases of the secondary side of the transformer are short-circuited, the three-phase voltage value fluctuates obviously, the three-phase voltage value is asymmetric, the deviation from a theoretical value is large and exceeds a preset deviation range, a frequency converter is controlled to enter an early warning state, a fault calculation prompt is sent out, a user side can carry out state detection in advance, and if the fault is judged to exist really, remedial measures can be taken in time;
s2: in order to eliminate the influence of complex factors such as a power grid, a load and the like, and obtain the comparison relation between the secondary three-phase voltage of the transformer and a normal operation theoretical value, at the moment, because of the short circuit of the two phases b and c, according to theory and simulation analysis, the requirement that the amplitude of the fault phase voltage is reduced by about a half is met, and the non-fault phase voltage is approximately equal to the short-circuit fault characteristic of the two-phase voltage of the voltage before the fault (other fault types correspond to different voltage characteristics and can be obtained by analyzing and calculating the short-circuit fault);
s3: considering the rigor of actual working conditions and logic judgment, three-phase voltages need to be compared comprehensively in the comparison process, the three-phase voltages are compared with the three-phase voltages of all fault types to obtain an average theoretical deviation, then the average theoretical deviation is compared with a preset deviation theoretical value, and when the average theoretical deviation is larger than the preset deviation theoretical value, the fault type is considered to be inconsistent or no fault occurs; and when the average theoretical deviation is less than the preset deviation theoretical value, taking the fault type corresponding to the minimum theoretical deviation item of each fault type as a final result (the theoretical deviation value and the preset deviation theoretical value are related to the transformer parameters and the load working condition, and the voltage data of the frequency converter control system needs to be referred).
S4: and prompting the fault type and the fault tripping of the frequency converter.
Finally, the above embodiments are only intended to illustrate the technical solutions of the present invention and not to limit the present invention, and although the present invention has been described in detail with reference to the preferred embodiments, it will be understood by those skilled in the art that modifications or equivalent substitutions may be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions, and all of them should be covered by the claims of the present invention.
Claims (5)
1. A transformer secondary side short-circuit fault distinguishing method based on short-circuit voltage characteristics is characterized by comprising the following steps:
s1: sampling to obtain three-phase voltage of multiple secondary sides of the transformer;
s2: comparing the effective difference value of the three-phase voltage with a preset theoretical value by using a comparison unit, and entering S3 if the effective difference value of the three-phase voltage is greater than the preset theoretical value of the voltage;
s3: recalculating the three-phase voltage relationship by using a mathematical operation unit;
s4: judging whether the three-phase voltage relation meets the voltage characteristic of the short-circuit fault or not;
s5: and when the three-phase voltage is judged to meet the short-circuit voltage condition, prompting the type of the short-circuit fault and tripping the frequency converter in fault.
2. The method for determining the secondary side short-circuit fault of the transformer according to claim 1, wherein the step S4 of determining whether the three-phase voltage relationship satisfies the short-circuit fault voltage characteristic includes: and (4) comparing the three-phase voltage relation calculated in the step (S3) with preset voltage theoretical values under different fault types, and if the voltage deviation is within a preset threshold range, judging that the secondary side of the transformer is short-circuited and the frequency converter is tripped due to fault.
3. The method according to claim 1, wherein the short-circuit fault voltage characteristic in step S4 includes: when the two phases b and c are short-circuited, according to theory and simulation analysis, the amplitude of the fault phase voltage is reduced by about half, and the non-fault phase voltage is approximately equal to the two-phase voltage short-circuit fault characteristic of the voltage before the fault.
4. The method according to claim 1, wherein the short-circuit fault voltage characteristic in step S4 further includes: based on the voltage change relation during short circuit, single-phase short circuit and three-phase short circuit fault characteristics, but in practical application, two-phase short circuit occurs more, so that two-phase short circuit fault is judged as the highest priority in the fault judgment stage.
5. The method for determining a secondary side short-circuit fault of a transformer according to claim 2, wherein in step S4, when determining whether the three-phase voltage relationship satisfies the short-circuit fault voltage characteristic, the method further considers rigor of actual conditions and logic determination, i.e. comprehensively compares the three-phase voltage with the three-phase voltage of each fault type to obtain an average theoretical deviation value, and then compares the average theoretical deviation value with a preset deviation theoretical value: when the average theoretical deviation value is larger than a preset deviation theoretical value, the fault type is considered to be inconsistent or no fault occurs; and when the average theoretical deviation is less than the preset deviation theoretical value, taking the fault type corresponding to the minimum theoretical deviation item of each fault type as a final result.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210140619.7A CN114594403A (en) | 2022-02-16 | 2022-02-16 | Transformer secondary side short circuit fault discrimination method based on short circuit voltage characteristics |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210140619.7A CN114594403A (en) | 2022-02-16 | 2022-02-16 | Transformer secondary side short circuit fault discrimination method based on short circuit voltage characteristics |
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| Publication Number | Publication Date |
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| CN114594403A true CN114594403A (en) | 2022-06-07 |
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| Application Number | Title | Priority Date | Filing Date |
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| CN202210140619.7A Pending CN114594403A (en) | 2022-02-16 | 2022-02-16 | Transformer secondary side short circuit fault discrimination method based on short circuit voltage characteristics |
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| CN (1) | CN114594403A (en) |
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- 2022-02-16 CN CN202210140619.7A patent/CN114594403A/en active Pending
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