CN114498558B - Generator stator grounding resistance segmentation algorithm based on 20Hz current-voltage phase difference - Google Patents
Generator stator grounding resistance segmentation algorithm based on 20Hz current-voltage phase difference Download PDFInfo
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- CN114498558B CN114498558B CN202210033683.5A CN202210033683A CN114498558B CN 114498558 B CN114498558 B CN 114498558B CN 202210033683 A CN202210033683 A CN 202210033683A CN 114498558 B CN114498558 B CN 114498558B
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- 230000011218 segmentation Effects 0.000 title claims abstract description 15
- 238000004364 calculation method Methods 0.000 claims abstract description 16
- 238000000034 method Methods 0.000 claims abstract description 16
- 238000002347 injection Methods 0.000 claims description 14
- 239000007924 injection Substances 0.000 claims description 14
- 238000005259 measurement Methods 0.000 claims description 12
- 230000009466 transformation Effects 0.000 claims description 5
- 238000004804 winding Methods 0.000 claims description 3
- 238000012937 correction Methods 0.000 abstract description 2
- 238000007689 inspection Methods 0.000 abstract description 2
- 238000012360 testing method Methods 0.000 description 6
- 238000010586 diagram Methods 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 230000000295 complement effect Effects 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
Classifications
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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
- H02H7/06—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 dynamo-electric generators; for synchronous capacitors
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
- G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
- G01R27/20—Measuring earth resistance; Measuring contact resistance, e.g. of earth connections, e.g. plates
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H1/00—Details of emergency protective circuit arrangements
- H02H1/0007—Details of emergency protective circuit arrangements concerning the detecting means
Abstract
The generator stator grounding resistance segmentation algorithm based on the 20Hz current-voltage phase difference comprises the following steps of: step one, drawing an equivalent circuit for measuring the grounding resistance of the grounding protection; calculating the resistance and reactance of the generator stator to the ground by utilizing a admittance method; and thirdly, calculating the phase difference and comparing the calculated phase with the set phase value according to the set phase value, so as to determine whether to adopt the calculated value of the admittance method or the calculated value of the phase difference. The accuracy of the calculation of the grounding resistance is improved by carrying out supplementary correction on the admittance algorithm, the measured resistance value is still stable when the high resistance is grounded, the error is basically controlled within 10%, the protection and daily inspection requirements are met, and the protection reliability is improved.
Description
Technical Field
The invention relates to the technical field of hydraulic generator protection measurement, in particular to a generator stator grounding resistance segmentation algorithm based on a 20Hz current-voltage phase difference.
Background
The large-scale generator set generally adopts a high-resistance grounding mode to limit the grounding current and overvoltage of the generator. Injection generator stator ground protection the generator stator ground resistance was measured by injecting 20Hz voltage into the stator. Generally, the method alarms when the grounding resistance is smaller than 5.0kΩ, and the method protects tripping when the grounding resistance is smaller than 0.5kΩ, and meanwhile, the running state of the generator stator is judged through the value of the grounding resistance when equipment is patrolled and examined. At present, the protection equipment manufacturer basically adopts a admittance method to calculate the grounding resistance, adopts a compensation mode through experiments to strive for more accurate calculation, and sets sectional compensation for more accurate measurement, namely adopts different compensation parameters in no-load and grid-connected states.
The ground resistance value measured according to the admittance algorithm is in a jump phenomenon, and as the ground resistance is increased, the 20Hz current is reduced, the smaller 20Hz voltage current value participates in admittance calculation, and small fluctuation can cause the great change of the measured resistance and even can be larger than a set value in the program. Variations in the mode of operation can also lead to small variations in system parameters and can also lead to measured resistance fluctuations. In the three gorges power station southward and Xu Jifa transformer group protection, the measured value fluctuation phenomenon exists in operation. Therefore, the simple admittance algorithm cannot accurately reflect the state of high-resistance grounding, and the numerical value is unfavorable for judging the actual state of the insulation of the stator of the generator.
Disclosure of Invention
The invention aims to solve the technical problem that when the generator stator based on the 20Hz current-voltage phase difference can avoid the phenomenon that the measured resistance value is larger due to smaller fluctuation of the real part of the admittance when the grounding resistance is larger when the admittance method is used for calculating the grounding resistance of the generator, and the measuring accuracy is improved.
In order to solve the technical problems, the invention adopts the following technical scheme:
the generator stator grounding resistance segmentation algorithm based on the 20Hz current-voltage phase difference comprises the following steps of:
step one, drawing a measurement equivalent circuit of an injection type stator grounding protection resistor, wherein the measurement equivalent circuit structure of the injection type stator grounding protection resistor is as follows:
injection power supply E 20 Internal resistance R of injected power supply 0 Ground load resistor R L Form a loop, and the parallel ground resistance Rg and the three-phase stator winding have total capacitance to ground and variable leakage resistance R K And X K Ground load resistor R L The components are converted into a secondary side, U 20 、I 20 20H collected for protection device Z Voltage, current, U 20 ' 20H after compensating the drain impedance of the ground transformer Z A voltage;
calculating primary side resistance and reactance by using a admittance method, wherein a calculation formula is as follows:
wherein X is g In order to measure the reactance of the electric motor,to measure resistanceCoefficient of reactance calculation, K T K is the ground transformation ratio I20 For intermediate CT transformation ratio, K U20 The voltage dividing ratio is the voltage dividing resistance, re is the real part, and Im is the imaginary part;
step three, pair 20H Z Current lead 20H Z The phase difference of the voltages is calculated:
due toThe fluctuation of the real part of the measured admittance has small calculation influence on the phase difference, so the phase difference is measured more stably, the resistance value reversely deduced by using the phase difference and the measured reactance is also more stable, and the calculation formula is as follows:
R g ＝X g *tanθ
will be based on 20H Z The ground resistance segmentation algorithm of the current-voltage phase difference is expressed as:
in θ Z For the phase difference setting value of the segment value, when the phase difference theta is smaller than or equal to theta Z When the phase difference theta is larger than theta, the grounding resistance calculated by adopting the admittance method is adopted Z And when the phase difference and the measured reactance are used for calculating the grounding resistance value, the influence of fluctuation of the real part of the admittance is small, and the measurement accuracy in high-resistance grounding can be improved.
The above-mentioned segment value phase difference theta Z The range of the value of (2) is 85-87 degrees.
According to the generator stator grounding resistance segmentation algorithm based on the 20Hz current-voltage phase difference, the admittance algorithm is subjected to complementary correction, so that the accuracy of calculation of the grounding resistance is improved, the measured resistance value is still stable when the high resistance is grounded, the error is basically controlled within a range of 10%, the protection measurement and daily inspection requirements are met, and the protection reliability is improved.
Drawings
The invention is further illustrated by the following examples in conjunction with the accompanying drawings:
FIG. 1 is a schematic diagram of the injection generator stator protection of the present invention;
fig. 2 is a schematic diagram of an equivalent circuit of the injection type stator ground protection of the present invention.
Detailed Description
The technical scheme of the invention is described in detail below with reference to the accompanying drawings and examples.
Injection stator protection of three gorges power station right bank 23F, 24F, 25F electric south self DGT801U series device is used as an example for explanation,
as shown in fig. 1-2, a generator stator ground resistance segmentation algorithm based on a 20Hz current-voltage phase difference, comprising the steps of:
step one, drawing a measurement equivalent circuit of an injection type stator grounding protection resistor, wherein the measurement equivalent circuit structure of the injection type stator grounding protection resistor is as follows:
injection power supply E 20 Internal resistance R of injected power supply 0 Ground load resistor R L Form a loop, and the parallel ground resistance Rg and the three-phase stator winding have total capacitance to ground and variable leakage resistance R K And X K Ground load resistor R L Form a loop, U 20 、I 20 20H collected for protection device Z Voltage, current, U 20 ' 20H after compensating the drain impedance of the ground transformer Z A voltage;
calculating primary side resistance and reactance by using a admittance method, wherein a calculation formula is as follows:
wherein X is g In order to measure the reactance of the electric motor,to measure the calculation coefficient of resistance and reactance, K T K is the ground transformation ratio I20 For intermediate CT transformation ratio, K U20 The voltage dividing ratio is the voltage dividing resistance, re is the real part, and Im is the imaginary part;
from the test on the unit, the test data are shown in Table 1:
(1) When the small resistor is grounded, the measured value is stable, but when the high resistor is grounded, the measured value is not stable enough, especially when the 20k omega is grounded, the angle difference is close to 90 degrees, and the fluctuation range of the measured resistor display value is from 20.1k omega to the maximum value of 30k omega, so that the fluctuation is obvious;
(2) When the high resistance is grounded, the phase difference between the 20Hz current and the voltage has small fluctuation, and the fluctuation range is much smaller than that of the measuring resistance;
(3) The measured reactance value is stable all the time, especially when the high resistance is grounded, the measured reactance value is stable at 0.770-0.772 kΩ.
TABLE 1 results of experiments using the principle of admittance method
Further analyzing the test result, when the high resistance is grounded, the phase difference is close to 90 degrees, and the resistance measured value after reciprocal taking according to the admittance method deviates from the actual resistance value greatly, which is the error caused by the grounded resistance admittance algorithm. The real part calculated value of the measured admittance is smaller, and after slight fluctuation, the deviation of the measured resistance value after taking the reciprocal is larger, and even the measured resistance value is possibly larger than the set value in the process.
From the analysis of the experimental data, the calculated values of the measured reactance and phase difference are relatively stable. Meanwhile, mathematical relations exist among the measured resistance, the measured reactance and the phase difference, and in order to solve the problem of jump of the measured resistance, the patent provides a grounding resistance segmentation algorithm based on the 20Hz current-voltage phase difference. When the small resistor is grounded, the original algorithm is still adopted, and when the high resistor is grounded, the measured resistance value can be calculated by calculating the stable measured reactance and phase difference.
Step three, pair 20H Z Current lead 20H Z The phase difference of the voltages is calculated:
due toThe fluctuation of the real part of the measured admittance has small calculation influence on the phase difference, so the phase difference is measured more stably, the resistance value reversely deduced by using the phase difference and the measured reactance is also more stable, and the calculation formula is as follows:
R g ＝X g *tanθ
will be based on 20H Z The ground resistance segmentation algorithm of the current-voltage phase difference is expressed as:
in θ Z When the phase difference theta is less than or equal to theta Z When the phase difference theta is larger than theta, the grounding resistance calculated by adopting the admittance method is adopted Z And when the phase difference and the measured reactance are used for calculating the grounding resistance value, the influence of fluctuation of the real part of the admittance is small, and the measurement accuracy in high-resistance grounding can be improved.
Theta as described above Z The range of the value of (2) is 85-87 degrees.
And when the resistance value of the actual grounding resistor Rg is larger than 20kΩ, adopting the calculation method in the step three.
When theta is as Z When the value of (2) is close to 90 degrees, the grounding resistance is higher, and the phase difference is utilized to reversely push the grounding resistance more accurately.
By analyzing the injection type stator grounding principle, combining equipment parameters and field test data, the calculated values of the measured reactance value and the phase difference are relatively stable, and meanwhile, mathematical relations exist among the measured resistance, the measured reactance and the phase difference, a novel segmentation algorithm of the stator grounding resistance of the generator based on the 20Hz current-voltage phase difference is provided, and an admittance algorithm is still adopted when the stator grounding is grounded through a small resistance. When the high-resistance is grounded, the measured resistance value is calculated by calculating the relatively stable measured reactance and phase difference. By adopting the improved grounding resistance algorithm, the measured resistance value is still stable when the high resistance is grounded, the error is controlled within 10%, the test data are shown in Table 2, and the engineering practical requirements are met.
Table 2 test data for the ground resistance segmentation algorithm employing the present invention
Claims (2)
1. The generator stator grounding resistance segmentation algorithm based on the 20Hz current-voltage phase difference is characterized by comprising the following steps of:
step one, drawing a measurement equivalent circuit of an injection type stator grounding protection resistor, wherein the measurement equivalent circuit structure of the injection type stator grounding protection resistor is as follows:
injection power supply E 20 Internal resistance R of injected power supply 0 Ground load resistor R L Form a loop, and the parallel ground resistance Rg and the three-phase stator winding have total capacitance to ground and variable leakage resistance R K And X K Ground load resistor R L Form a loop, U 20 、I 20 20H collected for protection device Z Voltage, current, U 20 ' 20H after compensating the drain impedance of the ground transformer Z A voltage;
calculating primary side resistance and reactance by using a admittance method, wherein a calculation formula is as follows:
wherein X is g In order to measure the reactance of the electric motor,to measure the calculation coefficient of resistance and reactance, K T K is the ground transformation ratio I20 For intermediate CT changesRatio, K U20 The voltage dividing ratio is the voltage dividing resistance, re is the real part, and Im is the imaginary part;
step three, pair 20H Z Current lead 20H Z The phase difference of the voltages is calculated:
due toThe fluctuation of the real part of the admittance is measured, and the resistance value deduced by the phase difference and the measured reactance is utilized, wherein the calculation formula is as follows:
R g ＝X g *tanθ
will be based on 20H Z The ground resistance segmentation algorithm of the current-voltage phase difference is expressed as:
in θ Z For the phase difference setting value of the segment value, when the phase difference theta is smaller than or equal to theta Z When the phase difference theta is larger than theta, the grounding resistance calculated by adopting the admittance method is adopted Z And when the phase difference and the measured reactance are used for calculating the grounding resistance value, the influence of fluctuation of the real part of the admittance is small, and the measurement accuracy in high-resistance grounding can be improved.
2. The method for segmenting the stator ground resistance of the generator based on the 20Hz current-voltage phase difference according to claim 1, wherein the segmentation value phase difference theta Z The range of the value of (2) is 85-87 degrees.
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| KR101061447B1 (en) * | 2010-07-28 | 2011-09-02 | 한국전력공사 | A neutral line synthetic reactance measurement method and apparatus at the electric distribution during the operation |
| CN104917148A (en) * | 2014-03-12 | 2015-09-16 | 南京南瑞继保电气有限公司 | Generator injection type stator grounding protection method and protection device |
| CN107947493A (en) * | 2017-11-23 | 2018-04-20 | 中国电建集团华东勘测设计研究院有限公司 | A kind of generator neutral point earthing or grounding means and parameter selection method |
| CN112234579A (en) * | 2020-10-28 | 2021-01-15 | 天生桥二级水力发电有限公司天生桥水力发电总厂 | Injection type stator grounding protection method and system of large hydraulic generator |
| CN112234578A (en) * | 2020-10-28 | 2021-01-15 | 天生桥二级水力发电有限公司天生桥水力发电总厂 | Stator grounding protection method and system by connecting resistors in series from arc suppression coil |
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Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR101061447B1 (en) * | 2010-07-28 | 2011-09-02 | 한국전력공사 | A neutral line synthetic reactance measurement method and apparatus at the electric distribution during the operation |
| CN104917148A (en) * | 2014-03-12 | 2015-09-16 | 南京南瑞继保电气有限公司 | Generator injection type stator grounding protection method and protection device |
| CN107947493A (en) * | 2017-11-23 | 2018-04-20 | 中国电建集团华东勘测设计研究院有限公司 | A kind of generator neutral point earthing or grounding means and parameter selection method |
| CN112234579A (en) * | 2020-10-28 | 2021-01-15 | 天生桥二级水力发电有限公司天生桥水力发电总厂 | Injection type stator grounding protection method and system of large hydraulic generator |
| CN112234578A (en) * | 2020-10-28 | 2021-01-15 | 天生桥二级水力发电有限公司天生桥水力发电总厂 | Stator grounding protection method and system by connecting resistors in series from arc suppression coil |
Non-Patent Citations (1)
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| 核电机组注入式定子接地保护若干问题探讨;陈佳胜;张琦雪;郭自刚;王光;陈俊;;电力自动化设备(第10期);全文 * |
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