CN115144686A - Generator neutral grounding system parameter simulation test method with enlarged unit wiring - Google Patents
Generator neutral grounding system parameter simulation test method with enlarged unit wiring Download PDFInfo
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- G—PHYSICS
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- 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
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Abstract
The application discloses a parameter simulation test method for a generator neutral point grounding system with enlarged unit wiring, which comprises an actual generator system and a simulation generator system which are operated in parallel, wherein the simulation generator system comprises a low zero sequence impedance transformer, a three-phase capacitor bank and a simulation generator neutral point grounding device; the parameter simulation test comprises the following steps: s1, configuring relay protection; s2, testing the asymmetric voltage of the neutral point of the generator grounding system connected with the wiring of the expansion unit; s3, testing the displacement voltage of the neutral point of the generator neutral point grounding system connected with the amplifying unit; s4, testing the single-phase grounding maximum capacitance current of the generator neutral point grounding system connected with the expansion unit; s5, testing the single-phase grounding maximum fault current of the generator neutral point grounding system of the expanded unit wiring; the grounding system performance of the unit wiring generator with different grounding modes can be effectively verified, and whether the grounding mode of the neutral point of the generator meets the technical requirements or not is determined.
Description
Technical Field
The application belongs to the technical field of power systems, and particularly relates to a generator neutral point grounding system parameter simulation test method for enlarging unit wiring.
Background
The enlarged unit wiring is a unit formed by connecting two generators and a transformer. When the single-phase grounding occurs at the outlet of the generator, the single-phase grounding fault current is the vector sum of the single-phase grounding capacitance current generated when the two generators operate and the neutral point current of the two generators, and the single-phase grounding capacitance current is the sum of the grounding capacitance currents of all equipment from the outlet of the two generators to the low-voltage side of the transformer, including a generator stator winding, a main transformer low-voltage winding, an excitation transformer, a service transformer, a cable, a bus and the like. The parameter test of the generator neutral point grounding system relates to a generator, a neutral point grounding device, a main transformer and all connecting equipment between the generator and the main transformer, such as an excitation transformer, a station transformer, a cable, a bus and the like. The parameters of the grounding devices of the enlarged unit wiring and the unit wiring are different in design value, and the isolated network double-machine parallel operation cannot be adopted for testing.
Therefore, it is necessary to develop a simulation test method for the parameters of the generator neutral grounding system with enlarged unit wiring.
Disclosure of Invention
In view of the above problems, an embodiment of the present application provides a method for testing parameter simulation of a generator neutral grounding system of an enlarged unit wiring, which can effectively evaluate the parameter performance of a generator neutral grounding device of the enlarged unit wiring, and verify whether a grounding mode meets technical requirements, and the technical scheme is as follows:
the parameter simulation test method of the generator neutral point grounding system of the enlarged unit wiring comprises an actual generator system and a simulation generator system, wherein the actual generator system and the simulation generator system are connected in parallel to run for parameter simulation test, and the simulation generator system comprises a low zero sequence impedance transformer, a three-phase capacitor bank and a simulation generator neutral point grounding device; the parameter simulation test comprises the following steps:
s1, configuring relay protection;
s2, testing the asymmetric voltage of the neutral point of the generator grounding system connected with the wiring of the expansion unit;
s3, testing the displacement voltage of the neutral point of the generator neutral point grounding system connected with the amplifying unit;
s4, testing the single-phase grounding maximum capacitance current of the generator neutral point grounding system connected with the expansion unit;
s5, testing the single-phase grounding maximum fault current of the generator neutral point grounding system of the expanded unit wiring;
the sequence between steps S2 to S5 can be arbitrarily adjusted.
For example, in one embodiment, the method for simulating generator neutral grounding system parameters by expanding unit wiring includes, in step S1, configuring a relay protection including a single-phase grounding maximum capacitance current test and a single-phase grounding maximum fault current test setting of an expanding unit generator: modifying a protection constant value of fundamental wave zero sequence overvoltage protection or third harmonic voltage single-phase grounding protection, wherein the zero sequence voltage constant value is higher than a single-phase grounding zero sequence voltage value under the highest test voltage; properly reducing the fixed value of the injection stator grounding protection resistor, properly increasing the fixed value of the current or quitting the operation; and setting a protection constant value according to the current flowing through the generator when the secondary three-phase of the low zero sequence impedance transformer is short-circuited.
For example, in one embodiment of the method for simulating and testing parameters of the extended-unit-wired generator neutral-point grounding system, in step S2, when the extended-unit-wired generator neutral-point grounding system neutral-point asymmetric voltage is tested, the generator in the simulated generator system operates with the main transformer, and the generator is accelerated to the rated rotation speed n N Stabilized at n N ±0.05％n N Then, reading the three-phase voltage and the neutral point voltage of the actual generator and the simulated stator winding, wherein the neutral point voltage measured by the voltage transformer TV is the neutral point asymmetric voltage, andthe neutral point asymmetric voltage is compared to the standard required value.
For example, in the parameter simulation test method for the generator neutral point grounding system connected with the line by the expansion unit provided in one embodiment, when the test voltage of the actual generator stator is the highest, that is, the voltage of the 100% rated stator, and potential safety hazard may exist due to the excessively high test voltage, the neutral point voltage measured by the voltage transformer TV is reduced to 30% of the rated voltage of the generator, and then the neutral point voltage measured by the voltage transformer TV at this time is reduced to 100% of the rated voltage, and the reduced generator neutral point voltage is the neutral point asymmetric voltage.
For example, in one embodiment of the method for simulating and testing parameters of the neutral point grounding system of the generator wired by the extension unit, in step S3, when the neutral point displacement voltage of the neutral point grounding system of the generator wired by the extension unit is tested, the generator in the simulated generator system operates with the main transformer, and the generator is accelerated to the rated rotation speed n N Stabilized at n N ±0.05％n N And then, gradually increasing the test voltage to 30% -100% of rated voltage, reading the three-phase voltage and the neutral point voltage of the stator windings of the actual generator and the simulated generator, wherein the neutral point voltage of the generator under the 100% of rated voltage is the neutral point displacement voltage, and comparing the neutral point asymmetric voltage with a standard required value.
For example, in an embodiment of the method for simulating and testing parameters of the generator neutral point grounding system connected with the amplifying unit, in step S4, when the single-phase grounding maximum capacitance current of the generator neutral point grounding system connected with the amplifying unit is tested, the generator neutral point is not grounded, the generator in the simulated generator system operates with the main transformer, the stator winding is grounded in a single phase, and the generator is accelerated to the rated rotation speed n N Stabilized at n N ±0.05％n N Then, the test voltage is gradually increased to 20% -50% of rated voltage and the single-phase earth fault current is controlled not to exceed the threshold current, the three-phase voltage of the actual generator and the simulated stator winding is read, the single-phase earth capacitance current is read and the waveform is recorded, the single-phase earth capacitance current is linearly reduced to 100% of the rated voltage, and the single-phase earth capacitance current is subjected to current linear reductionNamely the maximum capacitance current of the single-phase grounding of the generator.
For example, in the parameter simulation test method for the generator neutral point grounding system wired by the expansion unit, the single-phase grounding capacitor current is read by a recorder, and the waveform is recorded.
For example, in the parameter simulation test method for the generator neutral point grounding system of the expanded unit wiring, the test voltage is gradually increased to 20% -50% of the rated voltage, and the single-phase grounding fault current is controlled not to exceed 4A.
For example, in one embodiment of the method for simulating and testing parameters of the generator neutral point grounding system of the expanded unit wiring, in step S5, during the test of the maximum fault current of the single-phase grounding of the generator neutral point grounding system of the expanded unit wiring, the generator neutral point is connected to the grounding device, the generator in the simulated generator system operates with the main transformer, the outlet of the generator is grounded in a single-phase manner, and the generator is accelerated to the rated rotation speed n N Stabilized at n N ±0.05％n N And then, gradually increasing the test voltage to 20-50% of rated voltage, controlling the single-phase grounding fault current not to exceed threshold current, reading the three-phase voltage of stator windings of the actual generator and the simulated generator, reading the single-phase grounding fault current and the neutral point current of the actual generator and the simulated generator, recording waveforms, linearly reducing the single-phase grounding fault current to 100% of the rated voltage, and obtaining the single-phase grounding fault current which is the maximum single-phase grounding fault current of the generator.
For example, in the generator neutral point grounding system parameter simulation test method of the expanded unit wiring provided by one embodiment, the single-phase grounding fault current and the actual generator and the simulated generator neutral point current are read by a wave recorder and the waveform is recorded.
For example, in the parameter simulation test method for the generator neutral point grounding system of the expanded unit wiring, the test voltage is gradually increased to 20% -50% of the rated voltage, and the single-phase grounding fault current is controlled not to exceed 4A.
For example, in one embodiment, the parameter simulation test method for the generator neutral grounding system with the enlarged unit wiring is provided, the rated voltage of the low zero sequence impedance transformer is higher than the highest test voltage, the rated current is higher than 1/3 of the current flowing through the neutral grounding device at the highest test voltage, and the zero sequence impedance of the transformer is not more than 3% -5% of the impedance of the actual generator neutral grounding device.
For example, in one embodiment, the parameter simulation test method for the generator neutral point grounding system of the expanded unit connection is provided, the three-phase capacitor bank is composed of three single-phase capacitors, the connection group is in a star shape, the rated voltage is higher than the highest test voltage, the rated current is higher than the current flowing through the capacitors under the highest test voltage, and the capacitance per phase ground is consistent with the capacitance per phase ground of the simulated generator set.
For example, in one embodiment, the method for simulating generator neutral grounding system parameters of the enlarged unit wiring is provided, wherein the simulated generator neutral grounding device and the grounding device in the simulated generator system are kept consistent in parameters.
The beneficial effects brought by the parameter simulation test method of the generator neutral point grounding system with enlarged unit wiring are as follows: the method comprises the steps of testing the parameters of the neutral point grounding system of the generator with the single-machine parallel capacitor and the external transformer to simulate the double-machine operation, effectively evaluating the parameter performance of the neutral point grounding device of the generator with the enlarged unit wiring, and verifying whether the grounding mode meets the technical requirements.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is an electrical schematic diagram of a two-machine simulation test;
fig. 2 is an equivalent circuit diagram of the enlarged element grounding system.
Detailed Description
The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
Unless otherwise defined, technical or scientific terms used herein shall have the ordinary meaning as understood by one of ordinary skill in the art to which this disclosure belongs. The use of "first," "second," and similar terms in this disclosure is not intended to indicate any order, quantity, or importance, but rather is used to distinguish one element from another. The word "comprising" or "comprises", and the like, means that the element or item listed before the word covers the element or item listed after the word and its equivalents, but does not exclude other elements or items. The terms "connected" or "coupled" and the like are not restricted to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "upper", "lower", "left", "right", and the like are used merely to indicate relative positional relationships, and when the absolute position of the object being described is changed, the relative positional relationships may also be changed accordingly.
The application provides a generator neutral point grounding system parameter simulation test method of enlarging unit wiring, including one set of actual generator system and one set of simulation generator system, just actual generator system with simulation generator system parallel operation carries out parameter simulation test, simulation generator system includes low zero sequence impedance transformer, three-phase capacitor group, simulation generator neutral point grounding device. The parameter simulation test method for the generator neutral point grounding system with the expanded unit wiring adopts a unit formed by connecting two generators and a transformer, and develops parameter tests of the generator neutral point grounding system with the expanded unit wiring for searching parameters and performances of grounding devices under different grounding modes of the generator neutral point with the expanded unit wiring, wherein the parameters comprise asymmetric voltage of the generator neutral point, displacement voltage, single-phase grounding capacitance current, single-phase grounding maximum fault current and the like. Aiming at the problem that the double generators cannot be operated in an isolated network parallel mode to directly test the parameters, the test method for testing the parameters of the neutral point grounding system of the generator by operating the actual generator and the simulation generator in parallel is provided. The parameter performance of the generator neutral point grounding device with the enlarged unit wiring can be effectively evaluated, and whether the grounding mode meets the technical requirements or not is verified.
The test wiring comprises an actual generator system, a simulation generator system and a main transformer, the unit wiring is enlarged, and a simulation test wiring schematic diagram is shown in figure 1, wherein in figure 1: c A 、C B 、C C The single-phase total capacitance is equivalent to all electrical primary equipment between the generator and the main transformer; c A1 、C B1 、C C1 The total capacitance of the generator system is simulated. According to the method, the parameter test of the neutral point grounding system of the unit wiring generator is enlarged by constructing the simulation generator, the technical parameters of related equipment of the simulation generator are designed, a test platform is built, and the parameter test of the grounding systems of different grounding devices is developed.
The parameter simulation test of the application comprises the following steps:
s1, configuring relay protection;
s2, testing the asymmetric voltage of the neutral point of the generator grounding system connected with the wiring of the expansion unit;
s3, testing the displacement voltage of the neutral point of the generator neutral point grounding system connected with the amplifying unit;
s4, testing the single-phase grounding maximum capacitance current of the generator neutral point grounding system connected with the expansion unit;
s5, testing the single-phase grounding maximum fault current of the generator neutral point grounding system of the expanded unit wiring;
wherein, the sequence between the steps S2 to S5 can be adjusted arbitrarily.
The theoretical parameters of a neutral grounding system can be calculated by:
1) Double-unit single-phase to ground total capacitance parameter
The double-machine single-phase earth capacitance C is calculated according to the formula (1):
C＝C 1 +C 2 (1)
in the formula (I);
C 1 -the actual generator single-phase-to-ground total capacitance comprises the equivalent single-phase-to-ground total capacitance of all electrical primary equipment between the generator and the main transformer;
C 2 -simulating a single-phase-to-ground total capacitance of the generator, including an equivalent single-phase-to-ground total capacitance of all electrical primary equipment between the generator and the main transformer.
2) Total inductance parameter of dual machine
The total inductance of the double machine is calculated according to the formula (2):
in the formula (I);
L 1 -the shunt inductance of the secondary side of the actual generator neutral point grounding transformer;
L 2 -simulating a shunt inductance of the secondary side of the generator neutral grounding transformer.
3) Double-machine single-phase-to-ground total capacitance current Ic
The total capacitance current Ic of the double-machine single-phase-to-ground is
In the formula (I);
U n the generator rated voltage, V.
4) Double-machine neutral point total resistive current I R
Double-machine neutral point total resistive current I R Comprises the following steps:
in the formula (I);
R 1 -a shunt resistance of the secondary side of the actual generator grounding transformer;
R 2 -simulating a parallel resistance of the secondary side of the generator grounding transformer.
5) Double-machine neutral point total inductive current I L
Double machine neutral point total inductive current I L Comprises the following steps:
6) Double-machine single-phase grounding current I d
Double-machine single-phase grounding current I d Comprises the following steps:
in the formula:
I d -single phase ground current, a, when the dual machines are running;
I R -the sum of the resistive currents of the neutral points of the two generators, a;
I L -the sum of the inductive currents at the neutral points of the two generators, a.
7) Degree of detuning v
The degree of detuning v is:
8) Damping rate d
The damping rate d is:
9) Coefficient of displacement voltage m
The displacement voltage coefficient m is:
from the above mathematical model, it can be known that: the double-machine single-phase grounding current is the sum of two single-machine grounding currents, and the parameters of a grounding device cannot be designed according to the single-machine single-phase grounding current.
For example, in an embodiment of the method for performing parameter simulation test on the generator neutral point grounding system connected by the extension unit, in step S1, the relay protection configuration includes a maximum capacitor current test of the single-phase grounding of the generator of the extension unit and a test protection setting of the maximum fault current of the single-phase grounding: modifying a protection constant value of fundamental wave zero sequence overvoltage protection or third harmonic voltage single-phase grounding protection, wherein the zero sequence voltage constant value is higher than a single-phase grounding zero sequence voltage value under the highest test voltage; properly reducing the fixed value of the injection stator grounding protection resistor, properly increasing the fixed value of the current or quitting the operation; and setting a protection constant value according to the current flowing through the generator when the secondary three-phase of the low zero sequence impedance transformer is short-circuited.
For example, in the parameter simulation test method for the neutral point grounding system of the generator wired by the expansion unit, in step S2, when the neutral point asymmetric voltage of the neutral point grounding system of the generator wired by the expansion unit is tested, the generator in the simulation generator system operates with the main transformer, and the generator is accelerated to the rated rotation speed n N Stabilized at n N ±0.05％n N Then, reading the actual generator andand simulating three-phase voltage and neutral point voltage of the stator winding, wherein the neutral point voltage measured by the voltage transformer TV is the neutral point asymmetric voltage, and comparing the neutral point asymmetric voltage with a standard required value.
For example, in the parameter simulation test method for the generator neutral point grounding system connected by the extension unit in one embodiment, when the test voltage of the actual generator stator is the highest, that is, the voltage of the 100% rated stator, and potential safety hazards may exist due to the overhigh test voltage, the test voltage is reduced to 30% of the rated voltage of the generator, and then the neutral point voltage measured by the voltage transformer TV at this time is reduced to 100% of the rated voltage, and the reduced generator neutral point voltage is the neutral point asymmetric voltage.
For example, in one embodiment of the method for simulating and testing parameters of the neutral point grounding system of the generator wired by the extension unit, in step S3, when the neutral point displacement voltage of the neutral point grounding system of the generator wired by the extension unit is tested, the generator in the simulated generator system operates with the main transformer, and the generator is accelerated to the rated rotation speed n N Stabilized at n N ±0.05％n N And then, gradually increasing the test voltage to 30-100% of rated voltage, reading the three-phase voltage and the neutral point voltage of the stator windings of the actual generator and the simulated generator, wherein the neutral point voltage of the generator under the 100% of rated voltage is the neutral point displacement voltage, and comparing the neutral point asymmetric voltage with a standard required value.
For example, in an embodiment of the method for simulating and testing parameters of the generator neutral point grounding system connected with the amplifying unit, in step S4, when the single-phase grounding maximum capacitance current of the generator neutral point grounding system connected with the amplifying unit is tested, the generator neutral point is not grounded, the generator in the simulated generator system operates with the main transformer, the stator winding is grounded in a single phase, and the generator is accelerated to the rated rotation speed n N Stabilized at n N ±0.05％n N Then, the test voltage is gradually increased to 20% -50% of rated voltage, the single-phase earth fault current is controlled not to exceed the threshold current, the three-phase voltage of the actual generator and the simulated stator winding is read, and the three-phase voltage is readThe single-phase grounding capacitance current is linearly reduced to 100% of rated voltage, and is the maximum single-phase grounding capacitance current of the generator, wherein the single-phase grounding capacitance current is read by a wave recorder and is recorded, the test voltage is gradually increased to 20% -50% of rated voltage, and the single-phase grounding fault current is controlled not to exceed 4A.
For example, in one embodiment of the method for simulating and testing parameters of the generator neutral point grounding system of the expanded unit wiring, in step S5, during the test of the maximum fault current of the single-phase grounding of the generator neutral point grounding system of the expanded unit wiring, the generator neutral point is connected to the grounding device, the generator in the simulated generator system operates with the main transformer, the outlet of the generator is grounded in a single-phase manner, and the generator is accelerated to the rated rotation speed n N Stabilized at n N ±0.05％n N And then, gradually increasing the test voltage to 20-50% of rated voltage, controlling the single-phase earth fault current not to exceed a threshold current, reading the three-phase voltage of stator windings of the actual generator and the simulated generator, reading the single-phase earth fault current and the neutral point current of the actual generator and the simulated generator, recording waveforms, linearly reducing the single-phase earth fault current to 100% of the rated voltage, wherein the single-phase earth fault current is the maximum single-phase earth fault current of the generator, reading the single-phase earth fault current and the neutral point current of the actual generator and the simulated generator through a wave recorder, recording the waveforms, gradually increasing the test voltage to 20-50% of the rated voltage, and controlling the single-phase earth fault current not to exceed 4A.
For example, in the parameter simulation test method for the generator neutral grounding system with the enlarged unit wiring provided by one embodiment, the rated voltage of the low zero sequence impedance transformer is higher than the highest test voltage, the rated current is higher than 1/3 of the current flowing through the neutral grounding device under the highest test voltage, the zero sequence impedance of the transformer is not more than 3% -5% of the impedance of the actual generator neutral grounding device, and the transformer connection group is preferably YN, d or ZN.
For example, in one embodiment, the parameter simulation test method for the generator neutral point grounding system of the expanded unit connection is provided, the three-phase capacitor bank is composed of three single-phase capacitors, the connection group is in a star shape, the rated voltage is higher than the highest test voltage, the rated current is higher than the current flowing through the capacitors under the highest test voltage, and the capacitance per phase ground is consistent with the capacitance per phase ground of the simulated generator set.
For example, in one embodiment, the method for simulating generator neutral grounding system parameters of the enlarged unit wiring is provided, wherein the simulated generator neutral grounding device and the grounding device in the simulated generator system are kept consistent in parameters.
Examples of field tests
1) Generator neutral grounding system parameters
A. Basic overview of the unit
The generators of the hydraulic power plants #5 and #6 are connected in an expanding unit mode, the rated capacity is 110MW, the rated voltage is 15.75kV, the single-phase ground capacitance of a stator winding is 0.946 muF, capacitors are arranged at two ends of an outlet circuit breaker in a ground-to-ground mode, the single-phase ground capacitance of the generator side capacitor is 0.132 muF, and the single-phase ground capacitance of the main transformer low-voltage side capacitor is 0.260 muF. The neutral points of the #5 and #6 generators adopt high-impedance grounding devices, the parameters of the two devices are consistent, the designed value of primary side current flowing through the grounding devices is 7.36A, the rated capacity of a grounding transformer in the grounding devices is 50kVA, the rated voltage is 15.75kV/0.4kV, the transformation ratio is 52.5, the resistance value of a secondary side resistor of the grounding transformer is 0.66 omega, and the inductance value of a reactor is 1.52mH.
B. Analog generator system parameter selection
As shown in fig. 2, in the simulation test of the connection of the expansion unit, the maximum voltage is raised to 30% of the rated voltage, that is, 4.725kV, the rated voltage of the low zero sequence impedance transformer in the simulation generator system may be selected to be 10.5kV, and the rated current may be selected to be greater than (7.36 × 0.3)/3 = 0.736a. The secondary side resistance value and the reactance value of the grounding transformer are converted into equivalent impedance of 1066 omega on the primary side, the zero-sequence impedance of the generator is very small and ignored, the zero-sequence impedance of the transformer is smaller than 1066 multiplied by 0.03=31.98 omega, the low zero-sequence impedance transformer can select standard capacity of 160kVA, rated voltage of 10.5kV/0.4kV, the connection groups of YN and d, and the zero-sequence impedance of 8 omega.
The electric capacity of each phase of the three-phase capacitor bank is 0.946+0.132 +1.078 muF which is the sum of single-phase ground capacitance of a stator winding of the generator and single-phase parallel capacitance of a generator side of the circuit breaker, the electric capacity of the actually selected single-phase capacitor is 1.1 muF, the current flowing through the capacitor of each phase is 314 multiplied by 1.1 multiplied by 15.75/1.732 multiplied by 0.3=0.942A, the standard rated capacity of the capacitor of each phase is 50kvar, the rated voltage is 10.5kV, and the rated current is 4.76A.
2) Conclusion of the experiment
A. The asymmetric voltage of the neutral point of the #5 generator of the expanded unit junction is 302.61V, the displacement voltage is 314.35V, the asymmetric voltage does not exceed 10% rated phase voltage 909V specified by the standard, the displacement voltage coefficient is 1.039, and the asymmetric voltage does not exceed a reference value 1.5, and both the asymmetric voltage and the displacement voltage meet the requirements. After the high-impedance grounding device is connected, the voltage of the neutral point of the generator is increased, and the voltage of the neutral point of the generator can be limited within a controllable range by adjusting parameters of the grounding device.
B. The maximum single-phase grounding total capacitance current of the stator windings of the two generators is 21.19A and exceeds the short-time allowable value of single-phase grounding fault current by 15A, and after the neutral point of the generator is connected into the high-impedance grounding device, the maximum single-phase grounding fault current of the generator is 12.37A and is smaller than the short-time allowable value of the single-phase grounding fault current by 15A, which shows that the high-impedance grounding device can effectively reduce the single-phase grounding fault current.
C. The asymmetric voltage of the generator neutral point, the displacement voltage, the single-phase grounding capacitance current and the single-phase grounding fault current intensively reflect the parameter performance of the generator neutral point grounding system, the parameters of the generator neutral point grounding system of the enlarged unit wiring and the generator neutral point grounding system of the unit wiring are different, and because the two machines can not be directly operated in parallel in an isolated network, the simulation test of the generator neutral point grounding system parameter of the enlarged unit wiring by adopting the parallel connection of 1 generator and an external transformer and a capacitor to simulate the double-machine operation has great engineering significance.
Although embodiments of the present application have been disclosed for illustrative purposes, those skilled in the art will recognize that: various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.
Claims (14)
1. A parameter simulation test method of a generator neutral point grounding system with enlarged unit wiring is characterized by comprising an actual generator system and a simulation generator system, wherein the actual generator system and the simulation generator system are connected in parallel to run for parameter simulation test, and the simulation generator system comprises a low zero sequence impedance transformer, a three-phase capacitor bank and a simulation generator neutral point grounding device; the parameter simulation test comprises the following steps:
s1, relay protection configuration;
s2, testing the asymmetric voltage of the neutral point of the generator grounding system connected with the line of the expansion unit;
s3, testing the displacement voltage of the neutral point of the generator neutral point grounding system connected with the amplifying unit;
s4, testing the single-phase grounding maximum capacitance current of the generator neutral point grounding system connected with the expansion unit;
s5, testing the single-phase grounding maximum fault current of the generator neutral point grounding system connected with the expansion unit;
the sequence between steps S2 to S5 can be arbitrarily adjusted.
2. The generator neutral point grounding system parameter applicability test verification method according to claim 1, wherein in step S1, the relay protection configuration includes expanding single-phase grounding maximum capacitance current test and single-phase grounding maximum fault current test protection setting of the unit generator: modifying a protection constant value of fundamental wave zero sequence overvoltage protection or third harmonic voltage single-phase grounding protection, wherein the zero sequence voltage constant value is higher than a single-phase grounding zero sequence voltage value under the highest test voltage; properly reducing the fixed value of the injection stator grounding protection resistor, properly increasing the fixed value of the current or quitting the operation; and setting a protection constant value according to the current flowing through the generator when the secondary three-phase of the low zero sequence impedance transformer is short-circuited.
3. Generator neutral point according to claim 1The grounding system parameter applicability test verification method is characterized in that in the step S2, when the neutral point of the generator connected with the line of the expansion unit is tested with the neutral point asymmetric voltage of the grounding system, the generator in the simulation generator system runs with the main transformer, and the generator is accelerated to the rated rotating speed n N Stabilized at n N ±0.05％n N And then, reading the three-phase voltage and the neutral point voltage of the actual generator and the simulated stator winding, wherein the neutral point voltage measured by the voltage transformer TV is the neutral point asymmetric voltage, and comparing the neutral point asymmetric voltage with a standard required value.
4. The generator neutral point grounding system parameter applicability test verification method according to claim 3, characterized in that when the test voltage of an actual generator stator is the highest, namely 100% rated stator voltage, potential safety hazards may exist due to too high test voltage, the neutral point voltage measured by the voltage transformer TV is reduced to 100% rated voltage by reducing the test voltage to 30% rated generator voltage, and the reduced generator neutral point voltage is the neutral point asymmetric voltage.
5. The method for verifying the parameter applicability test of the generator neutral point grounding system according to claim 1, wherein in the step S3, when the neutral point displacement voltage of the generator neutral point grounding system connected with the enlarged unit is tested, the generator in the simulated generator system runs with a main transformer, and the generator is accelerated to the rated rotation speed n N Stabilized at n N ±0.05％n N And then, gradually increasing the test voltage to 30-100% of rated voltage, reading the three-phase voltage and the neutral point voltage of the stator windings of the actual generator and the simulated generator, wherein the neutral point voltage of the generator under the 100% of rated voltage is the neutral point displacement voltage, and comparing the neutral point asymmetric voltage with a standard required value.
6. The generator neutral point grounding system parameter applicability test verification method according to claim 1, characterized in that in step S4, expansion is performedWhen the single-phase grounding maximum capacitance current of the generator neutral point grounding system with unit wiring is tested, the generator neutral point is not grounded, a generator in the simulation generator system runs with a main transformer, a stator winding is in single-phase grounding, and the generator is accelerated to a rated rotating speed n N Stabilized at n N ±0.05％n N And then, gradually increasing the test voltage to 20-50% of rated voltage, controlling the single-phase grounding fault current not to exceed the threshold current, reading the three-phase voltage of the actual generator and the simulated stator winding, reading the single-phase grounding capacitance current and recording the waveform, and linearly normalizing the single-phase grounding capacitance current to 100% of the rated voltage, wherein the single-phase grounding capacitance current is the maximum single-phase grounding capacitance current of the generator.
7. The method for verifying the parameter applicability test of the generator neutral point grounding system according to claim 6, wherein the single-phase grounding capacitance current is read by a wave recorder and the waveform is recorded.
8. The generator neutral point grounding system parameter applicability test verification method according to claim 6, characterized in that the test voltage is gradually increased to 20% -50% of rated voltage and the single-phase grounding fault current is controlled not to exceed 4A.
9. The method for verifying the parameter applicability of the generator neutral grounding system according to claim 1, wherein in step S5, when the single-phase grounding maximum fault current of the generator neutral grounding system with enlarged unit wiring is tested, the generator neutral is connected to the grounding device, the generator in the simulated generator system operates with the main transformer, the generator outlet is grounded in a single-phase manner, and the generator is accelerated to the rated rotation speed n N Stabilized at n N ±0.05％n N Then, the test voltage is gradually increased to 20% -50% of rated voltage, the single-phase grounding fault current is controlled not to exceed the threshold current, the three-phase voltage of the stator windings of the actual generator and the simulated generator is read, the single-phase grounding fault current and the neutral point current of the actual generator and the simulated generator are read, the waveform is recorded, and the single-phase grounding fault current is recordedAnd the single-phase grounding fault current is the single-phase grounding maximum fault current of the generator when the current linearity is reduced to 100 percent of rated voltage.
10. The method for verifying the parameter applicability test of the generator neutral grounding system according to claim 9, wherein the single-phase grounding fault current and the actual generator and the simulated generator neutral point current are read by a recorder, and waveforms are recorded.
11. The generator neutral point grounding system parameter applicability test verification method according to claim 9, characterized in that the test voltage is gradually increased to 20% -50% of rated voltage and the single-phase grounding fault current is controlled not to exceed 4A.
12. The method for verifying the parameter applicability of the generator neutral grounding system according to claim 1, wherein the rated voltage of the transformer with low zero sequence impedance is higher than the highest test voltage, the rated current is higher than 1/3 of the current flowing through the neutral grounding device under the highest test voltage, and the zero sequence impedance of the transformer is not more than 3% -5% of the impedance of the actual generator neutral grounding device.
13. The generator neutral grounding system parameter applicability test verification method of claim 1, wherein the three-phase capacitor bank is composed of three single-phase capacitors, the connection bank is star-shaped, the rated voltage is higher than the highest test voltage, the rated current is higher than the current flowing through the capacitors under the highest test voltage, and the capacitance per phase to ground is consistent with the capacitance per phase to ground of the simulated generator set.
14. The generator neutral grounding system parameter applicability test validation method of claim 1, wherein the simulated generator neutral grounding device is consistent with grounding device parameters in the simulated generator system.
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