CN110364990B - Method for adjusting measurement precision of stator grounding insulation resistance of injection type generator of nuclear power station - Google Patents
Method for adjusting measurement precision of stator grounding insulation resistance of injection type generator of nuclear power station Download PDFInfo
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- CN110364990B CN110364990B CN201910481753.1A CN201910481753A CN110364990B CN 110364990 B CN110364990 B CN 110364990B CN 201910481753 A CN201910481753 A CN 201910481753A CN 110364990 B CN110364990 B CN 110364990B
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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
- G01R27/025—Measuring very high resistances, e.g. isolation resistances, i.e. megohm-meters
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/006—Calibration or setting of parameters
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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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Abstract
The invention belongs to the technical field of generators of nuclear power plants and auxiliary systems thereof, and particularly relates to a method for adjusting the measurement precision of a stator grounding insulation resistance of an injection generator of a nuclear power plant, which comprises the following steps: injecting a low-frequency signal source into the injection type generator stator grounding protection system; obtaining an equivalent circuit of the injection type generator stator ground protection system equivalently according to the injection mode of the low-frequency signal source in the injection type generator stator ground protection system and the electrical parameters of relevant components in the injection type generator stator ground protection system; carrying out modeling calculation according to the equivalent circuit to obtain a relational expression of measurement of the resistance value of the grounding insulation resistor of the injection type generator stator grounding protection system and precision adjustment of the resistance value; and adjusting related parameters in the protection device according to the relational expression so as to reduce the error between the theoretical calculation value of the insulation resistance and the measured value of the insulation resistance of the protection device.
Description
Technical Field
The invention belongs to the technical field of generators of nuclear power plants and auxiliary systems thereof, and particularly relates to a method for adjusting the ground protection measurement accuracy of an injection generator stator of a nuclear power plant.
Background
The single-phase grounding of the stator winding of the generator is the most common fault of the generator, is a premonitory sign of interphase or turn-to-turn short circuit, and plays an important role in the safe operation of the generator due to the perfect single-phase grounding protection of the stator. As generator capacity increases, the damage to stator winding ground faults is more severe and the likelihood of ground faults increases further due to the increased ground capacitance of the stator windings and the application of new cooling techniques. Therefore, it is necessary to install 100% stator ground protection without dead zone for large and medium sized generators.
The external 20Hz injection type stator ground protection is irrelevant to the ground fault position of the stator winding of the generator, can reflect the reduction condition of the stator winding insulation, and is widely applied to large-scale generator sets.
At present, when a protection device is put into operation for the first time and is tested at regular intervals, the situation that insulation resistance measurement is inaccurate or accuracy is not high is often met, various compensation parameters need to be adjusted repeatedly, no rule can be followed, and the situations always troubles maintenance technicians in the production line; and the measurement accuracy of the insulation resistance is low, and the parameter matching is not regular, so that false alarm or no alarm of the protection device can be caused, the real-time monitoring effect on the insulation of the stator of the generator is lost, and a great deal of work of maintenance technicians is increased.
Therefore, the traditional technical scheme has the problems of inaccurate insulation resistance measurement or low accuracy.
Disclosure of Invention
The invention aims to provide a method for adjusting the measurement precision of the stator grounding insulation resistance of an injection type generator of a nuclear power station, and aims to solve the problems of inaccurate or low precision of insulation resistance measurement in the traditional technical scheme.
The embodiment of the invention provides a method for adjusting the measurement precision of the stator grounding insulation resistance of an injection type generator of a nuclear power station, which comprises the following steps:
injecting a low-frequency signal source into the injection type generator stator grounding protection system;
obtaining an equivalent circuit of the injection type generator stator ground protection system equivalently according to the injection mode of the low-frequency signal source in the injection type generator stator ground protection system and the electrical parameters of relevant components in the injection type generator stator ground protection system;
carrying out modeling calculation according to the equivalent circuit to obtain a relational expression of measurement of the resistance value of the grounding insulation resistor of the injection type generator stator grounding protection system and precision adjustment of the resistance value;
and adjusting related parameters in the protection device according to the relational expression so as to reduce the error between the theoretical calculation value of the insulation resistance and the measured value of the insulation resistance of the protection device.
In one embodiment, the adjusting the relevant parameters in the protection device includes:
when the generator outlet circuit breaker is in a brake-off state, the angle value of the protection device is close to the angle value of the current leading voltage of the low-frequency signal source by adjusting the angle compensation parameter of the protection device.
In one embodiment, the adjusting the relevant parameters in the protection device further includes:
and adjusting the series resistance compensation parameter of the protection device to be a generator stator single-phase earth fault transition resistance value so as to compensate the secondary resistance value of the protection device.
In one embodiment, the adjusting the relevant parameters in the protection device further includes:
the angle compensation parameter and the series resistance compensation parameter of the protection device are both measured data when the generator outlet circuit breaker is in a switching-off state, the parallel resistance compensation parameter is set to be infinite, then the generator outlet circuit breaker is closed, the secondary resistance value parameter of the protection device at the moment is read, and the reciprocal of the secondary resistance value parameter is taken as the parallel admittance parameter value of the protection device.
In one embodiment, the electrical parameters of the relevant components in the injection generator stator ground protection system include the short-circuit impedance and the leakage reactance of a generator neutral grounding transformer, the contact resistance and the cable resistance of a low-frequency voltage and current measurement loop, the equivalent impedance of a high-voltage service transformer neutral grounding transformer, and the generator stator winding to ground capacitance.
In one embodiment, the influence of the generator stator winding on the ground capacitive reactance on the relation is not counted in the modeling calculation process.
In one embodiment, the relationship is:
wherein, V64sA low frequency injection voltage; i is64sInjecting a current for low frequency; theta is an included angle between the voltage and the current before phase compensation; 1/Rp corresponds to a parallel resistance compensation parameter in the protection device; rs corresponds to a series resistance compensation parameter in the protection device; phi corresponds to an angle compensation parameter in the protection device; rf is a generator stator single-phase earth fault transition resistance, namely an earth insulation resistance of the injection type generator stator earth protection system.
In one embodiment, the injection type generator stator grounding protection system comprises an adjustable rheostat, a generator neutral point grounding secondary load resistor, a voltage divider, a generator neutral point grounding transformer, a current transformer for current measurement, a band-pass filter, a low-frequency signal injection source and a protection device; the generator neutral point grounding end is respectively connected with the first end of the adjustable rheostat and the first end of the primary winding of the generator neutral point grounding transformer; the second end of the adjustable rheostat and the second end of the primary winding of the generator neutral point grounding transformer are grounded; the first end of the secondary winding of the generator neutral point grounding transformer is respectively connected with the first end of the generator neutral point grounding secondary load variable resistor, the first end of the voltage divider and the second end of the band-pass filter; the first end of the band-pass filter is connected with the first end of the low-frequency signal injection source; the second end of the low-frequency signal injection source is respectively connected with the second end of the generator neutral point grounding secondary load resistance, the second end of the voltage divider and the second end of the secondary winding of the generator neutral point grounding transformer and is grounded; the second end and the sliding end of the voltage divider are used as low-frequency voltage acquisition input ends of the protection device; the current transformer is used for collecting low-frequency current and transmitting the low-frequency current to the low-frequency current collecting input end of the protection device.
In one embodiment, the equivalent circuit comprises a generator stator single-phase earth fault transition resistor, a high-plant transformer neutral point earth transformer loop equivalent parallel resistor, a generator neutral point earth transformer loop equivalent series resistor, a generator stator winding earth equivalent capacitive reactance and a phase compensation module; the first end of the low-frequency injection voltage is respectively connected with the generator stator single-phase earth fault transition resistor, the first end of the high-plant transformer neutral point earth transformer loop equivalent parallel resistor and the first end of the generator stator winding earth equivalent capacitive reactance; the second end of the low-frequency injection voltage is connected with the input end of the phase compensation module; the output end of the phase compensation module is respectively connected with the second end of the equivalent series resistor of the generator neutral point grounding variable circuit and the second end of the equivalent capacitive reactance of the generator stator winding to the ground; the first end of the generator neutral point grounding variable loop equivalent series resistor is respectively connected with the generator stator single-phase grounding fault transition resistor and the second end of the high plant neutral point grounding variable loop equivalent parallel resistor.
Through field tests and engineering application verification, compared with the prior art, the embodiment of the invention has the following beneficial effects: according to the embodiment of the invention, a mathematical model is abstracted from the generator stator ground protection object wiring, and the mathematical model is analyzed and transformed to obtain a relational expression for improving the measurement precision of the insulation resistance, and the measurement precision of the protection ground resistance is effectively improved by adjusting corresponding parameters in the relational expression; meanwhile, the efficiency of measuring the protective grounding resistance is improved, so that parameter configuration and adjustment in the measuring process are more regular; the embodiment of the invention improves the measurement accuracy of the protective grounding resistance, and directly improves the sensitivity and reliability of the generator stator grounding fault alarm.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the embodiments or the prior art descriptions will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without inventive exercise.
FIG. 1 is a flow chart of a method for adjusting measurement accuracy of insulation resistance of a stator of an injection generator according to an embodiment of the present invention;
FIG. 2 is a schematic circuit diagram of an injection generator stator ground protection system in accordance with an embodiment of the present invention;
FIG. 3 is an equivalent circuit schematic of the injection generator stator ground protection system of FIG. 2;
FIG. 4 is a graph of measurement error curves for an embodiment of the present invention;
FIG. 5 is a comparison graph of theoretical values and actual values of insulation resistance in an open state according to an embodiment of the present invention;
fig. 6 is a comparison graph of theoretical values and actual values of the insulation resistance in a closing state according to the embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
In the embodiment of the invention, the method for adjusting the measurement accuracy of the ground protection of the injection type generator stator abstracts a mathematical model from the physical wiring of the ground protection of the generator stator, analyzes and transforms the mathematical model, and improves the measurement accuracy of the protection ground resistance by adjusting compensation parameters; meanwhile, the efficiency of measuring the protective grounding resistance is improved, so that parameter configuration and adjustment in the measuring process are more regular; the embodiment of the invention improves the measurement accuracy of the protective grounding resistance, and directly improves the sensitivity and reliability of the generator stator grounding fault alarm.
In order to explain the technical means of the present invention, the following detailed description will be given by way of specific examples.
Fig. 1 shows a method for adjusting measurement accuracy of stator ground insulation resistance of an injection generator according to an embodiment of the present invention, which is detailed as follows:
in one embodiment, the injection generator stator ground insulation resistance measurement accuracy adjustment method comprises the following steps:
and step S11, injecting a low-frequency signal source into the injection type generator stator grounding protection system. In the embodiment of the present invention, a 20Hz signal source is used as a low frequency signal source, which is exemplified and not limited to the 20Hz signal source.
And step S12, equivalently obtaining an equivalent circuit of the injection type generator stator ground protection system according to the injection mode of the low-frequency signal source in the injection type generator stator ground protection system and the electrical parameters of relevant components in the injection type generator stator ground protection system. The injection mode can be injected from an open delta winding of a generator terminal voltage transformer or can be injected from the secondary side of a neutral point grounding transformer, the embodiment of the invention adopts a mode that the neutral point of a generator set generator is grounded through a single-phase grounding transformer (a low-voltage side resistor), and 20Hz signals are injected from two ends of a secondary side load resistor of the grounding transformer, as shown in figure 2:
wherein V is shown in FIG. 264sInjection voltage for 20 Hz; i is64sIs 20Hz current; g1 is a generator stator winding; the GCB is a generator outlet circuit breaker; TS is a high-voltage station transformer; VT1 is a generator neutral grounding transformer; the VT2 is a neutral grounding transformer of the high-voltage station transformer; RL1 is the generator neutral point grounding to secondary load resistance; RL2 is secondary load resistor of neutral point grounding transformer of high-voltage station transformer; g2 is a 20Hz signal injection source; BP is a band-pass filter; CT is a current transformer for measuring 20Hz current; rd is a voltage divider; p345 is a protection device; rx is an adjustable rheostat.
The injection type generator stator grounding protection system comprises an adjustable resistor Rx, a generator neutral point grounding secondary load resistance RL1, a voltage divider Rd, a generator neutral point grounding transformer VT1, a current transformer CT for measuring 20Hz current, a band-pass filter BP, a 20Hz signal injection source G2 and a protection device P345; the generator neutral grounding end is respectively connected with the first end of the adjustable resistor Rx and the first end of the primary winding of the generator neutral grounding transformer VT 1; the second end of the adjustable varistor Rx and the second end of the primary winding of the generator neutral grounding transformer VT1 are grounded; a first end of a secondary winding of the generator neutral grounding transformer VT1 is respectively connected with a first end of the generator neutral grounding secondary load resistance RL1, a first end of the voltage divider Rd and a second end of the band-pass filter BP; a first end of the band-pass filter BP is connected with a first end of the 20Hz signal injection source G2; a second end of the 20Hz signal injection source G2 is respectively connected with a second end of the generator neutral point grounding secondary load resistance RL1, a second end of the voltage divider Rd, and a second end of a secondary winding of the generator neutral point grounding transformer VT1, and is grounded; the second end and the sliding end of the voltage divider Rd are used as 20Hz voltage acquisition input ends of the protection device P345; the current transformer CT is used for collecting 20Hz current and transmitting the 20Hz current to the 20Hz current collecting input end of the protection device P345.
The working principle is as follows: the injection type stator grounding protection is that a low-frequency (such as 20 Hz) alternating-current voltage signal source is applied between a neutral point of a stator winding of the generator and the ground. In normal operation, no or very little capacitive current is generated. When the stator winding has ground fault, a closed loop is formed through the ground resistor, and 20Hz fault current is generated. This method of measuring ground faults is independent of the location of the stator winding fault point. The generator has protection function in the static and running processes, has high sensitivity and can continuously monitor the insulation change condition of the stator winding of the generator.
Step S13, carrying out modeling calculation according to the equivalent circuit to obtain a first relational expression of measurement of the resistance value of the grounding insulation resistor of the injection generator stator grounding protection system and adjustment of the precision thereof, which is as follows:
wherein, V64sA low frequency injection voltage; i is64sInjecting a current for low frequency; rs is the equivalent series resistance of the generator neutral point grounding transformer loop; rp is equivalent parallel resistance of the high-voltage substation neutral point grounding transformer loop; theta is an included angle between the voltage and the current before phase compensation; phi is the phase compensation angle.
In order to analyze the influence of insulation resistance measurement precision of each parameter in the formula (I), the formula (I) is transformed into a second relational expression, which is shown as follows:
wherein, 1/Rp corresponds to a parallel resistance compensation parameter in the protection device; rs corresponds to a series resistance compensation parameter in the protection device; phi corresponds to an angle compensation parameter in the protection device; rf is the generator stator single-phase earth fault transition resistance.
Based on the second relation, under the condition that the injection signal of 20Hz is not changed, the Rf value calculated by the protection device has direct proportional relation with the parameters Rp, Rs and phi. Therefore, Rp, Rs, Φ are the key parameters that determine the accuracy of the Rf protection device. By properly adjusting the parameters, more accurate measurement values of the ground resistance of the stator winding of the generator, namely the insulation resistance value, can be obtained, so that the protection is more sensitive and reliable.
In the formula (I) and the formula (II), 1/Rp corresponds to a Parallel resistance compensation parameter 64S Parallel G in a P345 protection device; rs corresponds to a Series resistance compensation parameter 64S Series R; phi corresponds to the Angle compensation parameter 64S Angle Comp.
The protection device obtains accurate grounding resistance value by actually measuring and adjusting compensation parameters such as 1/Rp, Rs, phi and the like.
Step S14, adjusting relevant parameters in the protection device according to the relational expression, so as to reduce an error between a theoretical calculation value of the insulation resistance and an actual measurement value of the insulation resistance by the protection device.
In the process of converting the injection type generator stator grounding protection system into the equivalent circuit, the equivalent circuit is equivalently simplified on the basis of considering the electrical parameters of related elements in the injection type generator stator grounding protection system, and the electrical parameters of the related elements comprise the short-circuit impedance and the leakage reactance of a generator neutral point grounding transformer VT1, the contact resistance and the cable resistance of a low-frequency voltage and current measurement loop, the equivalent impedance of a high-voltage station transformer neutral point grounding transformer VT2 and the ground capacitance of a generator stator winding.
The equivalent circuit comprises a generator stator single-phase earth fault transition resistor Rf, a high-plant transformer neutral point earth variable loop equivalent parallel resistor Rp, a generator neutral point earth variable loop equivalent series resistor Rs, a generator stator winding earth equivalent capacitive reactance Xcg and a phase compensation module; the first end of the 20Hz injection voltage is respectively connected with the generator stator single-phase earth fault transition resistor Rf, the first end of the high plant transformer neutral point earth variable loop equivalent parallel resistor Rp and the first end of the generator stator winding earth equivalent capacitive reactance Xcg; the second end of the 20Hz injection voltage is connected with the input end of the phase compensation module; the output end of the phase compensation module is respectively connected with the second end of the generator neutral point grounding variable circuit equivalent series resistance Rs and the second end of the generator stator winding pair grounding equivalent capacitive reactance Xcg; and the first end of the equivalent series resistor Rs of the generator neutral point grounding variable loop is respectively connected with the single-phase grounding fault transition resistor Rf of the generator stator and the second end of the equivalent parallel resistor Rp of the high plant neutral point grounding variable loop.
Wherein Xcg is the equivalent capacitive reactance of the generator stator winding to the ground; rs is the equivalent series resistance of the generator neutral point grounding transformer loop; rp is equivalent parallel resistance of the high-voltage substation neutral point grounding transformer loop; rf is the generator stator single-phase earth fault transition resistance (i.e. the measured resistance of the protection device).
Since the measurement resistance Rf is related to the square of the frequency of the injection signal, the lower the frequency of the injection signal, the less the influence of the ground capacitance Cg of the generator stator winding on Rf; therefore, generator stator winding versus ground capacitive reactance Xcg is not considered in the modeling calculations herein.
Next, according to the above method, an embodiment description will be given for parameter configuration and Rf accuracy adjustment when the generator outlet circuit breaker GCB is in different opening and closing states, and experimental data will be provided for verification, which are as follows:
1. and (4) setting and adjusting the compensation parameters during the opening of the GCB at the outlet of the generator.
The initial settings of the angle compensation parameter and the series resistance compensation parameter of the protection device are both zero, and the initial settings of the parallel resistance compensation parameter are infinite.
1.1, measuring and setting an angle compensation parameter phi.
As shown in fig. 2, an adjustable resistor Rx is connected to the primary side of the generator neutral point grounding transformer, the analog grounding resistance is infinite (disconnection Rx), and the Angle measured by the check protection device is 64S I Angle. Under the working condition, the impedance on the 20Hz measuring loop is the ground capacitance of the stator winding of the generator and is a capacitive load, and the 20Hz current is ideally advanced by +90 degrees. Due to the influence of other devices on the loop and the measurement error of the current transformer, 64SIAngle is not +90 degrees in general. Therefore, it is necessary to compensate 64SIAngle to be close to +90 ° by adjusting the parameter φ. For example, a measurement angle of +97 ° is set to-7 °; the measurement angle was 87 °, and set to +3 °.
In short, when the generator outlet circuit breaker is in the open brake state, the angle value of the protection device is made to approach the angle value of the current lead voltage of the low-frequency signal source by adjusting the angle compensation parameter of the protection device.
1.2, measuring and setting a series resistance compensation parameter Rs.
The simulated ground resistance was zero ohm (Rx resistance was adjusted to 0 Ω in fig. 2), and the Secondary resistance 64SR Secondary measured by the protection device was checked. Ideally, the secondary resistance measured by the protection device should be 0 Ω. However, under such a condition, the impedance of the 20Hz measurement loop actually includes resistances such as leakage reactance of the generator neutral point grounding transformer, short-circuit impedance, and loop cable connection, and the measured value is not 0 Ω. In order to enable the protection device to measure the ground resistance of the stator winding of the generator more accurately, the influence of the part of series impedance needs to be eliminated in calculation. Therefore, it is necessary to compensate the 64SR Secondary to be close to 0 by setting the parameter Rs. For example, if Rf is 10 Ω, Rs is set to 10 Ω.
In short, the series resistance compensation parameter of the protection device is adjusted to a generator stator single-phase earth fault transition resistance value so as to compensate the secondary resistance value of the protection device.
1.3, testing the measurement accuracy of the grounding resistance of the protection device.
By changing the resistance value of Rx in figure 2, different grounding resistance conditions of the stator winding of the generator are simulated, and the accuracy of the measuring resistance Rf of the protection device is checked. When the generator outlet circuit breaker GCB is opened, the test has no influence of parallel conductance 1/Rp, and the second relation can be simplified into a third relation. If the error of the measured value does not meet the standard requirement in the test process, the accuracy of the measured resistance Rf of the protection device can be changed by adjusting the series resistance compensation parameter Rs and the angle compensation parameter phi according to the third relational expression. The third relationship is as follows:
from the third relationship, it can be seen that Rf is inversely proportional to Rs and directly proportional to φ, with other parameters being constant. Rs is adjusted when Rf has a small deviation from a standard value, and phi is adjusted when Rf has a large deviation, so that the adjustment efficiency can be improved. Taking the test situation of the machine set No. 2 of the nuclear power station of australia, lingering, as an example, multiple tests are performed according to the above ground resistance measurement accuracy adjustment method, and relatively accurate Rf data (table 1) are obtained, as follows:
TABLE 1100% stator ground protection test data (GCB open; φ = -7.0 °, Rs =6.5 Ω, 1/Rp = 0)
2. And (4) setting and adjusting the compensation parameters when the generator outlet circuit breaker GCB is switched on.
The angle compensation phi and the series resistance compensation Rs are unchanged, and the parallel admittance 1/Rp compensation is set to 0 (the parallel resistance compensation is set to ∞) using data actually measured by the generator outlet circuit breaker GCB at the opening position.
2.1, 1/Rp measurement and setting.
And switching on a generator outlet circuit breaker GCB, and connecting a neutral grounding transformer VT2 of the high-voltage station transformer into a measurement loop of the protection device. Similarly, test wiring is performed according to fig. 2, the analog ground resistance Rx is infinite, the Secondary resistance value 64SR Secondary of the resistance measured by the protection device at this time is read, the reciprocal of the resistance value is calculated to obtain the value of the parallel admittance, and then the admittance value 1/Rp is set in the fixed value column corresponding to the protection device.
In short, the angle compensation parameter and the series resistance compensation parameter of the protection device both adopt the measured data of the generator outlet circuit breaker in the opening state, the parallel resistance compensation parameter is set to infinity, then the generator outlet circuit breaker is closed, the secondary resistance value parameter of the protection device at the moment is read, and the reciprocal of the secondary resistance value parameter is taken as the parallel admittance parameter value of the protection device. 2.2, testing the measurement accuracy of the grounding resistance of the protection device.
By changing the resistance Rx in FIG. 2, different grounding resistance values are simulated, so that the accuracy of the protection device for measuring the grounding resistance of the stator winding of the generator is checked. From the second relationship, it can be seen that Rf is inversely proportional to Rs and directly proportional to φ and 1/Rp, with other parameters being constant. By adjusting these three compensation parameters, a more accurate resistance measurement can be obtained. Taking the test situation of the No. 2 machine set of the watershed australian nuclear power station as an example, multiple tests are performed according to the above ground resistance measurement accuracy adjustment method to obtain more accurate Rf data, and as shown in table 2, the details are as follows:
TABLE 2100% stator ground protection test data (GCB closing, = -7.0 °; Rs =6.5 Ω; 1/Rp =14.00 ms)
On the basis of the field experimental data listed in tables 1 and 2, a measurement precision error curve diagram shown in fig. 4 is made, and it can be known from the graph that by applying the injection type generator stator ground protection measurement precision adjusting method provided by the invention, after adjusting each compensation parameter, when the generator stator winding ground resistance is below 30k Ω, the precision errors of the measurement resistance Rf of the protection device are all within 15%, the measurement is relatively accurate, and the requirement of the field on the precision of the measurement resistance Rf is met.
In summary, the embodiment of the invention forms the equivalent circuit diagram of the protection system by analyzing the 20Hz injection type 100% stator ground protection schematic diagram, and further obtains the theoretical calculation formula of the protection device for measuring the generator stator winding ground resistance. And carrying out equation transformation on the first relational expression according to different primary system structures to obtain a second relational expression and a third relational expression.
After the test data in table 1 and table 2 are compared and analyzed, the conclusion is reached that the actually measured resistance value of the protection device is basically consistent with the theoretical calculated value, the data comparison curve is shown in fig. 5 and fig. 6, and the figure fully illustrates that the relation formula obtained by equivalence is accurate in fitting the actual Rf value of the protection device.
From the second relation and the third relation, it can be known that: during GCB brake opening, Rf of the protection device is inversely proportional to Rs and directly proportional to Rs; during GCB closing, Rf of the protection device is inversely proportional to Rs and directly proportional to phi and 1/Rp. By properly adjusting the above 3 compensation parameters of the protection device, the accuracy of Rf can be improved.
Table 3 shows the experimental data for varying the 1/Rp values without changing the other parameters. As can be seen from Table 3, the Rf of the protection device shows an overall decreasing trend after the 1/Rp value is finely adjusted from 14.02ms to 14.00 ms. Other trends were consistent with theoretical analysis.
TABLE 3 test data of ground resistance Rf (GCB closing) of generator stator winding at different 1/Rp
The external 20Hz injection type stator ground protection is irrelevant to the ground fault position of the stator winding of the generator, can reflect the reduction condition of the stator winding insulation, and is widely applied to large-scale generator sets. When the protection device is put into operation for the first time and tested regularly, the situation that Rf is inaccurate is often encountered, and according to the method disclosed by the embodiment of the invention, the compensation parameters are properly adjusted, so that the measurement accuracy and the protection reliability of the grounding resistance can be improved.
The method for adjusting the ground protection measurement accuracy of the stator of the injection type generator disclosed by the embodiment of the invention is applied to the ground protection test of the stator of the injection type generator of 4 units of the nuclear power station in gulf and Australia of Ridges, and successfully solves the problem of inaccurate field protection measurement value; and by applying the method, the measurement accuracy of the stator ground protection of the injection type generator of the 4 machines in the nuclear power station in Bay and Australia of Ridges is improved, the reliability of protection operation is improved, the safe and stable operation of the generator is ensured, and the workload of maintenance technicians in the production line is greatly saved. The method can be popularized and applied to domestic power plants applying injection type generator stator ground protection.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.
Claims (9)
1. The method for adjusting the measurement precision of the ground insulation resistance of the injection generator stator of the nuclear power station is characterized by comprising the following steps of:
injecting a low-frequency signal source into the injection type generator stator grounding protection system;
obtaining an equivalent circuit of the injection type generator stator ground protection system equivalently according to the injection mode of the low-frequency signal source in the injection type generator stator ground protection system and the electrical parameters of relevant components in the injection type generator stator ground protection system;
carrying out modeling calculation according to the equivalent circuit to obtain a relational expression of measurement of the resistance value of the grounding insulation resistor of the injection type generator stator grounding protection system and precision adjustment of the resistance value;
according to the relational expression, relevant parameters in the protection device are adjusted, so that the error between a theoretical calculation value of the insulation resistance and an actually measured value of the insulation resistance by the protection device is reduced;
the relation is as follows:
wherein, V64sA low frequency injection voltage; i is64sInjecting a current for low frequency; theta is an included angle between the voltage and the current before phase compensation; 1/Rp corresponds to a parallel resistance compensation parameter in the protection device; rs corresponds to a series resistance compensation parameter in the protection device; phi corresponds to an angle compensation parameter in the protection device; rf is generator statorAnd the sub single-phase earth fault transition resistor is the earth insulation resistor of the injection generator stator earth protection system.
2. The method of claim 1, wherein adjusting the relevant parameters in the protection device comprises:
when the generator outlet circuit breaker is in a brake-off state, the angle value of the protection device is close to the angle value of the current leading voltage of the low-frequency signal source by adjusting the angle compensation parameter of the protection device.
3. The method of claim 1 or 2, wherein adjusting the relevant parameters in the protection device further comprises:
and adjusting the series resistance compensation parameter of the protection device to be a generator stator single-phase earth fault transition resistance value so as to compensate the secondary resistance value of the protection device.
4. The method of claim 2, wherein adjusting the parameters associated with the protection device further comprises:
the angle compensation parameter and the series resistance compensation parameter of the protection device are both measured data when the generator outlet circuit breaker is in a switching-off state, the parallel resistance compensation parameter is set to be infinite, then the generator outlet circuit breaker is closed, the secondary resistance value parameter of the protection device at the moment is read, and the reciprocal of the secondary resistance value parameter is taken as the parallel admittance parameter value of the protection device.
5. The method of claim 2, wherein adjusting the parameters associated with the protection device further comprises:
the angle compensation parameter and the series resistance compensation parameter of the protection device are measured data when the generator outlet circuit breaker is in a switching-off state, the parallel resistance compensation parameter is set to be infinite, then the generator outlet circuit breaker is closed, the secondary resistance value parameter of the protection device at the moment is read, and the reciprocal of the secondary resistance value parameter is taken as the parallel admittance parameter value of the protection device.
6. The method of claim 1, wherein the electrical parameters of the relevant components in the injection generator stator ground protection system include short circuit impedance and leakage reactance of a generator neutral grounding transformer, contact resistance and cable resistance of a low frequency voltage current measurement loop, equivalent impedance of a high voltage service transformer neutral grounding transformer, and generator stator winding to ground capacitance.
7. The method of claim 6, wherein during the modeling calculations, the effect of ground capacitive reactance on the relationship is disregarded.
8. The method of claim 1, wherein the injection generator stator ground protection system comprises an adjustable varistor, a generator neutral grounding to secondary load resistor, a voltage divider, a generator neutral grounding transformer, a current transformer for current measurement, a band pass filter, a low frequency signal injection source, and a protection device; the generator neutral point grounding end is respectively connected with the first end of the adjustable rheostat and the first end of the primary winding of the generator neutral point grounding transformer; the second end of the adjustable rheostat and the second end of the primary winding of the generator neutral point grounding transformer are grounded; the first end of the secondary winding of the generator neutral point grounding transformer is respectively connected with the first end of the generator neutral point grounding secondary load variable resistor, the first end of the voltage divider and the second end of the band-pass filter; the first end of the band-pass filter is connected with the first end of the low-frequency signal injection source; the second end of the low-frequency signal injection source is respectively connected with the second end of the generator neutral point grounding secondary load resistance, the second end of the voltage divider and the second end of the secondary winding of the generator neutral point grounding transformer and is grounded; the second end and the sliding end of the voltage divider are used as low-frequency voltage acquisition input ends of the protection device; the current transformer is used for collecting low-frequency current and transmitting the low-frequency current to the low-frequency current collecting input end of the protection device.
9. The method of claim 1, wherein the equivalent circuit comprises a generator stator single-phase ground fault transition resistance, a high plant transformer neutral point grounding transformer loop equivalent parallel resistance, a generator neutral point grounding transformer loop equivalent series resistance, a generator stator winding grounding equivalent capacitive reactance, and a phase compensation module; the first end of the low-frequency injection voltage is respectively connected with the generator stator single-phase earth fault transition resistor, the first end of the high-plant transformer neutral point earth transformer loop equivalent parallel resistor and the first end of the generator stator winding earth equivalent capacitive reactance; the second end of the low-frequency injection voltage is connected with the input end of the phase compensation module; the output end of the phase compensation module is respectively connected with the second end of the equivalent series resistor of the generator neutral point grounding variable circuit and the second end of the equivalent capacitive reactance of the generator stator winding to the ground; the first end of the generator neutral point grounding variable loop equivalent series resistor is respectively connected with the generator stator single-phase grounding fault transition resistor and the second end of the high plant neutral point grounding variable loop equivalent parallel resistor.
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