CN114498558A - 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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- 238000004364 calculation method Methods 0.000 claims abstract description 16
- 238000000034 method Methods 0.000 claims abstract description 12
- 238000005259 measurement Methods 0.000 claims description 19
- 238000002347 injection Methods 0.000 claims description 14
- 239000007924 injection Substances 0.000 claims description 14
- 230000009466 transformation Effects 0.000 claims description 7
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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
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- 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
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Abstract
The generator stator ground resistance segmentation algorithm based on the 20Hz current voltage phase difference comprises the following steps: step one, drawing an equivalent circuit for measuring the grounding resistance of the grounding protection; secondly, calculating the resistance and the reactance of the generator stator to the ground by using a admittance method; and step three, calculating the phase difference and comparing the phase difference with the calculated phase according to the set phase size so as to determine whether to adopt the calculated value of the admittance method or the calculated value of the phase difference. By supplementing and correcting the admittance algorithm, the accuracy of the calculation of the ground resistance is improved, the measured resistance value is still stable when the high-resistance ground is realized, the error is basically controlled within 10 percent, the requirements of protection and daily inspection tour are met, and the protection reliability is improved.
Description
Technical Field
The invention relates to the technical field of protection and measurement of hydraulic generators, in particular to a generator stator grounding resistance segmentation algorithm based on a 20Hz current voltage phase difference.
Background
Large generator sets generally use a high-resistance grounding mode to limit generator ground current and overvoltage. The injection type generator stator grounding protection is characterized in that the generator stator grounding resistance is measured by injecting 20Hz voltage into a stator. Generally, when the grounding resistance is less than 5.0k omega, an alarm is given, when the grounding resistance is less than 0.5k omega, the protection is tripped out, and meanwhile, the running state of the generator stator is judged according to the value of the grounding resistance when equipment is patrolled. At present, protection equipment manufacturers basically adopt a admittance method to calculate the grounding resistance, adopt a compensation mode through tests, strive to make the calculation more accurate, and set sectional compensation for making the measurement more accurate, namely adopt different compensation parameters in a no-load state and a grid-connected state.
The grounding resistance value measured according to the admittance algorithm has a jump phenomenon, the 20Hz current is reduced along with the increase of the grounding resistance, the smaller 20Hz voltage current value participates in the admittance calculation, and the small fluctuation can cause the large change of the measured resistance, even the small fluctuation is possibly larger than the set value in the program. Changes in the operating mode can also lead to minor changes in system parameters, which can also lead to fluctuations in the measured resistance. In the protection of the south rui and the allowable secondary transformation group of the three gorges power station, measurement value fluctuation occurs in the operation. Therefore, the state of grounding through high resistance cannot be accurately reflected by a simple admittance algorithm, and the numerical value of the admittance algorithm is not beneficial to judging the real state of the insulation of the generator stator.
Disclosure of Invention
The invention aims to solve the technical problem that when the generator ground resistance is calculated by an admittance method, the phenomenon that the measured resistance value is larger due to smaller fluctuation of the admittance real part when the ground resistance is larger can be avoided by providing the generator stator based on the 20Hz current voltage phase difference, and the measurement accuracy is improved.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows:
the generator stator ground resistance segmentation algorithm based on the 20Hz current voltage phase difference comprises the following steps:
step one, drawing a measurement equivalent circuit of the injection type stator grounding protection resistor, wherein the structure of the measurement equivalent circuit of the injection type stator grounding protection resistor is as follows:
injection power supply E20Injecting internal resistance R of power supply0And a ground load resistor RLA circuit is formed, the grounding resistor Rg and the three-phase stator winding which are connected in parallel are used for providing total capacitance resistance to the ground and changing the grounding leakage resistance RKAnd XKAnd a ground load resistor RLForm a loop, the above elements are converted into secondary side, U20、I2020H collected for protection deviceZVoltage, current, U2020H after compensating for leakage impedance of groundingZA voltage;
step two, calculating the primary side resistance and reactance by using a admittance method, wherein the calculation formula is as follows:
in the formula, XgIn order to measure the reactance of the electric machine,
for measuring the conversion coefficient of resistance and reactance, KTTo ground transformation ratio, KI20For intermediate CT transformation ratio, KU20The voltage dividing ratio of the divider resistor, Re is a real part, and Im is an imaginary part;
step three, 20HZCurrent lead 20HZThe phase difference of the voltages was calculated:
due to the fact that
The fluctuation of the real part of the measured admittance has little influence on the calculation of the phase difference, so the measurement of the phase difference is more stable, the resistance value reversely derived by utilizing the phase difference and the measured reactance is also more stable, and the calculation formula is as follows:
Rg＝Xg*tanθ
will be based on 20HZThe grounding resistance segmentation algorithm of the current-voltage phase difference is represented as:
in the formula, thetaZIs a phase difference setting value of a segment value when the phase difference theta is less than or equal to thetaZWhen the phase difference theta is larger than theta, the ground resistance value calculated by the admittance method is adoptedZIn the time, the grounding resistance value calculated by utilizing the phase difference and the measured reactance is slightly influenced by the fluctuation of the real part of the admittance, so that the measurement accuracy in high-resistance grounding can be improved.
The above-mentioned segment-valued phase difference θZThe value range of (A) is 85-87 degrees.
According to the generator stator grounding resistance segmentation algorithm based on the 20Hz current voltage phase difference, the accuracy of the grounding resistance calculation is improved by supplementing and correcting the admittance algorithm, the measured resistance value is still stable when the grounding is conducted in a high-resistance grounding state, the error is basically controlled within a range of 10%, the requirements of protection measurement and daily inspection 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 protection schematic of injection generator stator protection according to the present invention;
fig. 2 is an equivalent circuit diagram of the injection stator ground protection of the present invention.
Detailed Description
The technical scheme of the invention is explained in detail in the following by combining the drawings and the embodiment.
The injection stator protection of the devices from DGT801U series in the south China electrical south of the three gorges power station right bank 23F, 24F and 25F is taken as an example for explanation,
as shown in fig. 1-2, the generator stator ground resistance segmentation algorithm based on 20Hz current voltage phase difference comprises the following steps:
step one, drawing a measurement equivalent circuit of the injection type stator grounding protection resistor, wherein the structure of the measurement equivalent circuit of the injection type stator grounding protection resistor is as follows:
injection power supply E20Injecting internal resistance R of power supply0And a ground load resistor RLA circuit is formed, the grounding resistor Rg and the three-phase stator winding which are connected in parallel are used for providing total capacitance resistance to the ground and changing the grounding leakage resistance RKAnd XKAnd a ground load resistor RLForm a loop, U20、I2020H collected for protection deviceZVoltage, current, U20' is compensation20H after the leakage impedance of groundingZA voltage;
step two, calculating the primary side resistance and reactance by using a admittance method, wherein the calculation formula is as follows:
in the formula, XgIn order to measure the reactance of the electric machine,
for measuring the conversion coefficient of resistance and reactance, KTTo ground transformation ratio, KI20For intermediate CT transformation ratio, KU20The voltage dividing ratio of the divider resistor, Re is a real part, and Im is an imaginary part;
as can be seen from the tests 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 resistance is grounded, the measured value is not stable enough, especially when 20k omega is grounded, the angle difference is close to 90 degrees, the fluctuation range of the measured resistor display value is from 20.1k omega to the maximum value of 30k omega, and the fluctuation is obvious;
(2) when the high resistance is grounded, the phase difference between the 20Hz current and the voltage fluctuates in a small range, and the fluctuation range is much smaller than that of the measured resistance;
(3) the measured reactance value is stable all the time, and particularly when the high resistance is grounded, the measured reactance value is stable at 0.770-0.772 kOmega.
TABLE 1 test results using the principle of the admittance method
Further analyzing the test result, when the grounding resistance is high-resistance grounded, the phase difference is close to 90 degrees, and the resistance measurement value after reciprocal according to the admittance method is greatly deviated from the actual resistance value, which is an error caused by the grounding resistance admittance algorithm. The real part calculation value of the measurement admittance is small, and after slight fluctuation, the measurement resistance value after reciprocal is large in deviation and even possibly larger than the set value in the program.
Analysis of experimental data shows that the calculated values of the measured reactance and the phase difference are relatively stable. Meanwhile, a mathematical relation exists among the measured resistance, the measured reactance and the phase difference, and in order to solve the problem of resistance jump, the patent provides a grounding resistance segmentation algorithm based on the 20Hz current-voltage phase difference. When the small resistance is grounded, the original algorithm is still adopted, and when the high resistance is grounded, the measured resistance value can be calculated by using the measured reactance and the phase difference which are more stable in calculation.
Step three, 20HZCurrent lead 20HZThe phase difference of the voltages was calculated:
due to the fact that
The fluctuation of the real part of the measured admittance has little influence on the calculation of the phase difference, so the measurement of the phase difference is more stable, the resistance value reversely derived by utilizing the phase difference and the measured reactance is also more stable, and the calculation formula is as follows:
Rg＝Xg*tanθ
will be based on 20HZThe grounding resistance segmentation algorithm of the current-voltage phase difference is represented as:
in the formula, thetaZWhen the phase difference theta is less than or equal to thetaZWhen the phase difference theta is larger than theta, the ground resistance value calculated by the admittance method is adoptedZIn the time, the grounding resistance value calculated by utilizing the phase difference and the measured reactance is slightly influenced by the fluctuation of the real part of the admittance, so that the measurement accuracy in high-resistance grounding can be improved.
Theta as defined aboveZThe value range of (A) is 85-87 degrees.
And when the resistance value of the actual grounding resistor Rg is larger than 20k omega, a calculation method in the third step is adopted.
When theta isZWhen the value of (1) is close to 90 degrees and the grounding resistance is higher, the phase difference is utilized to reversely deduce the grounding resistance more accurately.
By analyzing the grounding principle of the injection type stator, combining equipment parameters and field test data, the calculated values of the measured reactance value and the phase difference are relatively stable, meanwhile, a mathematical relation exists among the measured resistance, the measured reactance and the phase difference, a new algorithm for segmenting the grounding resistance of the generator stator based on the 20Hz current voltage phase difference is provided, and when the grounding is carried out through a small resistor, an admittance algorithm is still adopted. And when the high-impedance grounding is carried out, the measuring resistance value is calculated by utilizing the measuring reactance and the phase difference which are relatively stable in calculation. By adopting the improved grounding resistance algorithm, the measured resistance value is still stable when the high-resistance grounding is carried out, the error is controlled within the range of 10 percent, the test data is shown in the table 2, and the actual engineering requirements are met.
TABLE 2 test data using the ground resistance segmentation algorithm of the present invention
Claims (2)
1. The generator stator ground 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 the injection type stator grounding protection resistor, wherein the structure of the measurement equivalent circuit of the injection type stator grounding protection resistor is as follows:
injection power supply E20Injecting internal resistance R of power supply0And a ground load resistor RLA circuit is formed, the grounding resistor Rg and the three-phase stator winding which are connected in parallel are used for providing total capacitance resistance to the ground and changing the grounding leakage resistance RKAnd XKAnd a ground load resistor RLForm a loop, U20、I2020H collected for protection deviceZVoltage, current, U2020H after compensating for leakage impedance of groundingZA voltage;
step two, calculating the primary side resistance and reactance by using a admittance method, wherein the calculation formula is as follows:
in the formula, XgIn order to measure the reactance of the electric machine,
for measuring the conversion coefficient of resistance and reactance, KTTo ground transformation ratio, KI20For intermediate CT transformation ratio, KU20The voltage dividing ratio of the divider resistor, Re is a real part, and Im is an imaginary part;
step three, 20HZCurrent lead 20HZThe phase difference of the voltages was calculated:
due to the fact that
Measuring the fluctuation of the real part of the admittance, and using the phase difference and the resistance value obtained by measuring reactance inversion, wherein the calculation formula is as follows:
Rg＝Xg*tanθ
will be based on 20HZThe grounding resistance segmentation algorithm of the current-voltage phase difference is represented as:
in the formula, thetaZIs a phase difference setting value of a segment value when the phase difference theta is less than or equal to thetaZWhen the phase difference theta is larger than theta, the ground resistance value calculated by the admittance method is adoptedZThe earth resistance calculated by using the phase difference and the measured reactance is little influenced by the fluctuation of the real part of the admittance, and the measurement accuracy in high-resistance earth can be improvedAnd (4) degree.
2. The generator stator ground resistance segmentation algorithm based on 20Hz current voltage phase difference as claimed in claim 1, wherein the segmentation value phase difference θZThe value range of (A) 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 |
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| 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 |
| 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 |
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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 |
| 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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Non-Patent Citations (1)
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| 陈佳胜;张琦雪;郭自刚;王光;陈俊;: "核电机组注入式定子接地保护若干问题探讨", 电力自动化设备, no. 10 * |
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