CN111948467B - Capacitor bank internal fault detection method and capacitor protection device - Google Patents
Capacitor bank internal fault detection method and capacitor protection device Download PDFInfo
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- CN111948467B CN111948467B CN201910400287.XA CN201910400287A CN111948467B CN 111948467 B CN111948467 B CN 111948467B CN 201910400287 A CN201910400287 A CN 201910400287A CN 111948467 B CN111948467 B CN 111948467B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
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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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- 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
- H02H7/16—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 capacitors
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
- Y02E40/30—Reactive power compensation
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Abstract
The invention discloses a capacitor bank internal fault detection method, which is used for detecting an internal fault of a Y-shaped capacitor bank with a neutral point grounded through PT, wherein the capacitor bank is a three-phase Y-shaped wiring. The method comprises the following steps: measuring three-phase current, measuring three-phase bus voltage, measuring neutral point voltage of a capacitor bank, calculating effective value of neutral point differential voltage, compensating neutral point differential voltage, judging state of neutral point differential voltage, judging fault location and input of neutral point differential voltage, judging condition of bus zero sequence voltage, calculating effective angle difference between neutral point differential voltage and bus positive sequence voltage, determining whether the angle difference is in the characteristic range of 180 degrees, 60 degrees, 0 degrees, 120 degrees and 120 degrees, and judging a fault phase according to the effective angle difference and the angle difference characteristic. The invention correspondingly discloses a capacitor protection device. The technical scheme of the invention simplifies the fault positioning process, reduces the fault detection range and shortens the fault positioning time.
Description
Technical Field
The invention belongs to the field of relay protection of power systems. And more particularly, to a method of detecting an internal fault of a capacitor bank and a capacitor protection device.
Background
The power capacitor bank compensates the reactive shortage of the system by providing reactive power, so that the voltage stability of the system is improved. The capacitor bank can be used in a centralized way, and can be installed in a scattered way to provide local reactive power, so that the electric energy loss of a power network can be effectively reduced, and the system power factor can be improved. The capacitor has a wide capacity range, low investment cost, low operation loss, no rotating parts and convenient maintenance, and is widely used.
The capacitor bank is generally assembled by connecting a plurality of capacitor units in series and in parallel, and the series-parallel connection mode, the number and the capacity selection of the capacitor units are determined by the reactive compensation capacity of a system and the voltage of the system. The capacitor unit includes a plurality of elements therein, and the rated capacity and rated voltage of the capacitor unit are formed by connecting a large number of internal elements in series or in parallel. And a discharge resistor is integrated in each capacitor unit, so that when the capacitor is separated from a system bus, the capacitor can discharge through the resistor, and the external voltage of the capacitor bank is reduced to a safe level.
The capacitor body protection is realized by a fuse, and the method can be divided into the following steps according to the configuration condition of the fuse in a capacitor unit: external fuses, internal fuses, and no fuses. When a fault occurs in the capacitor, the fuse wire is fused on the occasion of the fuse wire, and a fault unit or element is isolated; when no fuse is present, the internal thin film of the element breaks down, and the failed element is short-circuited.
The capacitor unit or element is isolated or broken down by a fault, causing an imbalance in the three phase impedance of the capacitor bank, while the remaining part of the capacitor is subjected to high voltage. If the voltage of the remaining healthy capacitor units or elements does not exceed 1.1 times of the rated voltage, the capacitor can continue to operate, otherwise, the whole group of capacitors needs to be quitted, and the safety of each unit and element is ensured.
For a Y-type capacitor bank with a neutral point grounded through PT, internal fault warning or protection of the capacitor is generally realized by configuring neutral point differential pressure protection. When the capacitor alarm or protection action occurs, the fault part should be located and repaired in time.
The external fuse capacitor bank is provided with a fuse blowing indication occasion, and a fault unit can be determined quickly. For the non-fuse indication occasions or other fuse types, operators need to check all the units of the whole capacitor bank one by one, which is time-consuming and labor-consuming.
The Chinese invention provides a capacitor bank fault positioning method aiming at Y-Y type and H type connection modes, namely a method and a device for detecting internal faults in a Y-Y connection capacitor bank with the application number of 201180065014.6 and a method and a device for detecting internal faults in an H bridge connection capacitor bank with the application number of 201180064602.8, respectively, but the method cannot be applied to the fault positioning of the Y type capacitor bank with a neutral point grounded through PT.
The capacitor with the built-in fault output device of China invention application number 200910105940.6 adopts a fault indication device which is pre-embedded in the capacitor and can be used for a capacitor bank with a neutral point grounded through PT, but the method can only indicate that the capacitor has a fault and cannot accurately judge a fault phase, and devices are additionally arranged to increase the system cost.
Therefore, in order to improve the fault location efficiency of the Y-type capacitor bank with the neutral point grounded through PT and shorten the fault location time, a fault location method applicable to the Y-type capacitor bank with the neutral point grounded through PT, which can be integrated in the capacitor protection device, is required, and can overcome system errors and dynamic errors and accurately and reliably locate a fault phase.
Disclosure of Invention
The invention mainly aims to provide a method for detecting internal faults of a Y-shaped capacitor bank with a neutral point grounded through PT, which is integrated in a capacitor protection device, simplifies a fault positioning process, reduces a fault detection range and shortens fault positioning time. The invention also provides a corresponding capacitor protection device.
In order to achieve the purpose, the invention adopts the technical scheme that:
a capacitor bank internal fault detection method is used for detecting an internal fault of a Y-shaped capacitor bank with a neutral point grounded through PT, the capacitor bank is in three-phase Y-shaped connection, the neutral point is grounded through PT, the capacitor bank is formed by connecting a plurality of capacitor units in series or in parallel, parameters and configuration modes of the capacitor units are the same, and the internal fault of the capacitor bank occurs in internal elements of the capacitor units or among the capacitor units, and the method comprises the following steps:
step 110, measuring the three-phase voltage of the bus connected with the capacitor bank and calculating the positive sequence voltage
Zero sequence voltage
150, initiating an alarm signal or a protection trip signal when the differential pressure of the neutral point exceeds an alarm threshold or a protection threshold;
Further, after the step 130 and before the step 150, the method further includes:
140, compensating the differential pressure of the neutral point by adopting a static compensation method and/or a dynamic compensation method;
in step 150, an alarm signal or a protection trip signal is initiated when the compensated neutral point differential pressure exceeds an alarm threshold or a protection threshold.
Further, the static compensation method in step 140 is used to compensate the neutral point differential pressure in the initial stage of the capacitor operation based on the effective value of the phase current, the effective value of the bus zero-sequence voltage, and the effective value of the neutral point voltage, so as to compensate the inherent errors caused by the process error, the installation error, and the system error of the measurement element of the capacitor bank.
Further, the dynamic compensation method in step 140 is used to compensate the neutral point differential pressure according to a preset period value in the capacitor operation process based on the effective value of the phase current, the effective value of the bus zero-sequence voltage, and the effective value of the neutral point voltage, and periodically compensate for dynamic errors caused by temperature, humidity, and aging of internal elements in the capacitor bank operation process.
Further, the alarm threshold corresponds to a low differential pressure limit at which all remaining normal cells of the capacitor bank can remain operational to withstand overvoltage.
Further, the protection threshold corresponds to a high differential pressure limit at which all remaining normal cells of the capacitor bank cannot continue to operate and can withstand overvoltage.
Further, after step 150, the method further comprises:
Further, after step 150, the method further comprises:
and step 210, after setting a fixed value control alarm or a fault occurs, judging whether to execute a fault positioning function according to the condition of the zero sequence voltage of the bus.
The invention also provides a capacitor protection device, which is used for detecting the internal fault of a Y-shaped capacitor bank with a neutral point grounded through PT, wherein the capacitor bank is in three-phase Y-shaped connection, the neutral point of the Y-shaped connected capacitor bank is grounded through PT, the capacitor bank is formed by connecting a plurality of capacitor units in series or in parallel, the parameters and the configuration modes of the capacitor units are the same, and the internal fault of the capacitor bank is generated in the internal elements of the capacitor units or among the capacitor units; the capacitor bank is provided with a first current transformer for measuring the three-phase current of the capacitor bank; arranging a first voltage transformer for measuring the three-phase voltage of a bus connected with the capacitor bank; arranging a second voltage transformer for measuring the neutral point voltage of the capacitor bank; the capacitor protection device includes: the device comprises a computing unit, a protection unit and a fault positioning unit; wherein:
the calculating unit is used for receiving the voltage, the three-phase current of the capacitor bank measured by the current transformer, the three-phase voltage of a bus connected with the capacitor bank and the neutral point voltage of the capacitor bank; calculating effective values of three-phase currents of the capacitor bank; and calculating the effective value, the effective value and the phase of the three-phase voltage of the bus connected with the capacitor bank, and the effective value and the phase of the zero-sequence voltage of the bus connected with the capacitor bank.
And the protection unit is used for judging that an alarm signal is generated when the differential pressure value of the neutral point exceeds an alarm threshold value, and a protection tripping signal is generated when the differential pressure value of the neutral point exceeds a protection threshold value.
The fault positioning unit comprises an effective angular difference calculation module, an angular difference characteristic judgment module and a fault phase positioning module, wherein:
the effective angular difference calculation module is used for calculating the effective angular difference between the differential pressure of the neutral point and the positive sequence voltage of the bus;
the angular difference characteristic judging module judges whether the effective angular difference is within the characteristic ranges of 180 degrees, 60 degrees, -60 degrees, 0 degrees, -120 degrees and 120 degrees;
the fault phase positioning module is used for determining a fault phase according to the effective angular difference and the angular difference characteristics 。
Further, the capacitor protection device further comprises a compensation unit, wherein the compensation unit comprises a static compensation module and/or a dynamic compensation module.
And the static compensation module is used for compensating the differential pressure of the neutral point at the initial stage of the operation of the capacitor based on the effective value of the phase current, the effective value of the zero-sequence voltage of the bus and the effective value of the voltage of the neutral point, and making up the inherent errors caused by the process error, the installation error and the system error of the measuring element of the capacitor bank.
The dynamic compensation module is used for compensating the neutral point differential pressure according to a preset periodic value in the operation process of the capacitor based on the effective value of the phase current, the effective value of the bus zero-sequence voltage and the effective value of the neutral point voltage, and periodically compensating dynamic errors caused by the temperature, the humidity and the aging of internal elements in the operation process of the capacitor bank.
And the protection unit is used for generating an alarm signal when judging that the neutral point differential pressure value compensated by the compensation unit exceeds an alarm threshold value and generating a protection tripping signal when the neutral point differential pressure value exceeds a protection threshold value.
Furthermore, the fault positioning unit also comprises a fixed value module and an execution judgment module; wherein:
and the fixed value module is used for judging whether a fault positioning function is put into or not according to the neutral point differential pressure fault positioning input fixed value.
And the execution judgment module is used for judging whether the calculated bus zero-sequence voltage meets the fault positioning condition or not, and if so, executing the effective angular difference calculation module.
Compared with the prior art, the technical scheme of the invention has the following technical effects:
(1) The method for positioning the fault phase of the Y-type capacitor bank with the neutral point grounded through the PT judges the fault phase by comparing the angular difference characteristics of the neutral point differential pressure and the bus positive sequence voltage at the moment of fault, and can shorten the fault positioning time by 67%.
(2) The method for positioning the fault phase of the Y-type capacitor bank with the neutral point grounded through the PT eliminates system errors by adopting static compensation at the initial operation stage of the capacitor bank, eliminates dynamic errors by adopting dynamic compensation during the normal operation of the capacitor bank, tracks the normal state of the system in real time, avoids the misoperation or refusal of a protection device caused by the influence of the errors of the system, and improves the fault positioning effect.
(3) The method for positioning the fault phase of the Y-type capacitor bank with the neutral point grounded through the PT is integrated in the conventional capacitor protection device, does not increase any cost and configuration, and has good popularization and use values.
Drawings
FIG. 1 is a flow chart of an embodiment of a method of detecting an internal fault of a capacitor bank of the present invention;
FIG. 2 is a schematic configuration example illustrating a three-phase capacitor bank configuration and protecting the measurement transformer wiring;
fig. 3a and 3b illustrate the angular difference characteristic of a capacitor internal fault occurring in either phase in a fused, non-fused type configuration of the capacitor element, respectively.
Detailed Description
The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.
Method example 1:
a capacitor bank internal fault detection method is used for detecting an internal fault of a Y-shaped capacitor bank with a neutral point grounded through PT, the capacitor bank is in three-phase Y-shaped connection, the neutral point is grounded through PT, the capacitor bank is formed by connecting a plurality of capacitor units in series or in parallel, parameters and configuration modes of the capacitor units are the same, and the internal fault of the capacitor bank occurs in internal elements of the capacitor units or among the capacitor units, and the method comprises the following steps:
Step 110, measuring the three-phase voltage of the bus connected with the capacitor bank and calculating the positive sequence voltage
Zero sequence voltage
And 150, initiating an alarm signal or a protection trip signal when the neutral point differential pressure exceeds an alarm threshold or a protection threshold. Wherein the alarm threshold corresponds to a low differential pressure limit at which all remaining normal cells of the capacitor bank can remain operational to withstand overvoltage. Wherein the protection threshold corresponds to a high differential pressure limit at which all remaining normal cells of the capacitor bank cannot continue to operate and can withstand overvoltage.
In this embodiment, the capacitor unit is an internal fuse. Referring to fig. 3a, when phase a of the capacitor bank fails, the theoretical calculated angular difference should be 0 °; when the B phase of the capacitor bank fails, theoretically calculating the angular difference to be 120 degrees; when the capacitor bank phase C fails, the theoretical calculated angular difference should be-120 deg.. In particular, considering the measurement error and the influence of inductive and resistive components in the capacitor, the actual effective angular difference determination can be improved by increasing the angular offset range θ, which can be preset according to the actual condition of the capacitor, and can be generally set to the interval of [5 °,30 ° ]. According to the characteristic range determination method, the effective angular difference characteristic range of the A-phase fault is 0 degrees +/-theta, the effective angular difference characteristic range of the B-phase fault is 120 degrees +/-theta, and the effective angular difference characteristic range of the C-phase fault is-120 degrees +/-theta. Similarly, the outer fuse type capacitor effective angular difference characteristic range decision is the same as the inner fuse effective angular difference characteristic range decision.
Referring to fig. 3B, in the case of the fuse-less type capacitor, the effective angular difference characteristic range of the a-phase fault is 180 ° ± θ, the effective angular difference characteristic range of the B-phase fault is 60 ° ± θ, and the effective angular difference characteristic range of the C-phase fault is-60 ° ± θ.
Method example 2:
a capacitor bank internal fault detection method is used for detecting an internal fault of a Y-shaped capacitor bank with a neutral point grounded through PT, the capacitor bank is in three-phase Y-shaped connection, the neutral point is grounded through PT, the capacitor bank is formed by connecting a plurality of capacitor units in series or in parallel, parameters and configuration modes of the capacitor units are the same, and the internal fault of the capacitor bank occurs in internal elements of the capacitor units or among the capacitor units, and the method comprises the following steps:
Step 110, measuring the three-phase voltage of the bus connected with the capacitor bank and calculating the positive sequence voltage
Zero sequence voltage
And 140, compensating the differential pressure of the neutral point by adopting a static compensation method and/or a dynamic compensation method. The static compensation method is used for compensating the differential pressure of the neutral point at the initial stage of the operation of the capacitor based on the effective value of the phase current, the effective value of the zero sequence voltage of the bus and the effective value of the voltage of the neutral point, and makes up the inherent errors caused by the process error, the installation error and the system error of the measuring element of the capacitor bank. The dynamic compensation method is used for compensating the neutral point differential pressure according to a preset periodic value in the operation process of the capacitor based on the effective value of the phase current, the effective value of the bus zero-sequence voltage and the effective value of the neutral point voltage, and periodically compensating dynamic errors caused by temperature, humidity and internal element aging in the operation process of the capacitor bank.
And 150, initiating an alarm signal or a protection trip signal when the compensated neutral point differential pressure exceeds an alarm threshold or a protection threshold. Wherein the alarm threshold corresponds to a low differential pressure limit at which all remaining normal cells of the capacitor bank can remain operational to withstand overvoltage. Wherein the protection threshold corresponds to a high differential pressure limit at which all remaining normal cells of the capacitor bank cannot continue to operate and can withstand overvoltage.
And step 230, judging whether the effective angle difference is in the characteristic ranges of 180 degrees, 60 degrees, -60 degrees, 0 degrees, -120 degrees and 120 degrees.
In this embodiment, the capacitor unit is an internal fuse. Referring to fig. 3a, when phase a of the capacitor bank fails, the theoretical calculated angular difference should be 0 °; when the B phase of the capacitor bank fails, theoretically calculating the angular difference to be 120 degrees; when the capacitor bank phase C fails, the theoretical calculated angular difference should be-120 deg.. In particular, considering the measurement error and the influence of inductive and resistive components in the capacitor, the actual effective angular difference determination can be improved by increasing the angular offset range θ, which can be preset according to the actual condition of the capacitor, and can be generally set to the interval of [5 °,30 ° ]. According to the characteristic range determination method, the effective angular difference characteristic range of the A-phase fault is 0 degrees +/-theta, the effective angular difference characteristic range of the B-phase fault is 120 degrees +/-theta, and the effective angular difference characteristic range of the C-phase fault is-120 degrees +/-theta. Similarly, the outer fuse type capacitor effective angular difference characteristic range decision is the same as the inner fuse effective angular difference characteristic range decision.
Referring to fig. 3B, in the case of the fuse-less type capacitor, the effective angular difference characteristic range of the a-phase fault is 180 ° ± θ, the effective angular difference characteristic range of the B-phase fault is 60 ° ± θ, and the effective angular difference characteristic range of the C-phase fault is-60 ° ± θ.
Method example 3:
a capacitor bank internal fault detection method is used for detecting an internal fault of a Y-shaped capacitor bank with a neutral point grounded through PT, the capacitor bank is in three-phase Y-shaped connection, the neutral point is grounded through PT, the capacitor bank is formed by connecting a plurality of capacitor units in series or in parallel, parameters and configuration modes of the capacitor units are the same, and the internal fault of the capacitor bank occurs in internal elements of the capacitor units or among the capacitor units, and the method comprises the following steps:
Step 110, measuring three-phase voltage of a bus connected with the capacitor bank and calculating positive sequence voltage
Zero sequence voltage
And 150, initiating an alarm signal or a protection trip signal when the neutral point differential pressure exceeds an alarm threshold or a protection threshold. Wherein the alarm threshold corresponds to a low differential pressure limit at which all remaining normal cells of the capacitor bank can sustain an overvoltage for continued operation. Wherein the protection threshold corresponds to a high differential pressure limit at which all remaining normal cells of the capacitor bank cannot continue to operate and can withstand overvoltage.
And step 210, after setting a fixed value control alarm or a fault occurs, judging whether to execute a fault positioning function according to the condition of the zero sequence voltage of the bus.
And step 230, judging whether the effective angle difference is in the characteristic ranges of 180 degrees, 60 degrees, -60 degrees, 0 degrees, -120 degrees and 120 degrees.
In this embodiment, the capacitor unit is an internal fuse. Referring to fig. 3a, when phase a of the capacitor bank fails, the theoretical calculated angular difference should be 0 °; when the B phase of the capacitor bank fails, theoretically calculating the angular difference to be 120 degrees; when the capacitor bank phase C fails, the theoretical calculated angular difference should be-120 deg.. In particular, considering the measurement error and the influence of inductive and resistive components in the capacitor, the actual effective angular difference determination can improve the characteristic determination by increasing the angular offset range θ, which can be preset according to the actual condition of the capacitor, and can be set to a range of [5 ° and 30 ° ]. According to the characteristic range determination method, the effective angular difference characteristic range of the A-phase fault is 0 degrees +/-theta, the effective angular difference characteristic range of the B-phase fault is 120 degrees +/-theta, and the effective angular difference characteristic range of the C-phase fault is-120 degrees +/-theta. Similarly, the outer fuse type capacitor effective angular difference characteristic range decision is the same as the inner fuse effective angular difference characteristic range decision.
Referring to fig. 3B, in the case of the fuse-less type capacitor, the effective angular difference characteristic range of the a-phase fault is 180 ° ± θ, the effective angular difference characteristic range of the B-phase fault is 60 ° ± θ, and the effective angular difference characteristic range of the C-phase fault is-60 ° ± θ.
Method example 4:
fig. 1 is a flow chart of an embodiment of a method for detecting an internal fault of a capacitor bank according to the present invention; as shown in the figure, the method comprises the following steps:
Step 110, measuring the three-phase voltage of the bus connected with the capacitor bank and calculating the positive sequence voltage
Zero sequence voltage
Wherein the content of the first and second substances,
for a calculated zero-sequence voltage of the busbar>
Is a measurement of the voltage at the neutral point of the capacitor,/>
the neutral point differential pressure value is obtained.
And 140, compensating the differential pressure of the neutral point by adopting a static compensation method and/or a dynamic compensation method.
The static compensation method is used for compensating the differential pressure of the neutral point at the initial stage of operation of the capacitor based on the effective value of the phase current, the effective value of the zero sequence voltage of the bus and the effective value of the voltage of the neutral point, and makes up for inherent errors caused by process errors, installation errors and system errors of measuring elements of the capacitor bank. And the capacitor bank is required to be in an operating state at the static compensation moment, and the measurement and calculation results of the three-phase voltage of the bus, the current of the capacitor bank and the neutral point voltage of the capacitor bank meet the static compensation condition. If the condition of triggering the static compensation is satisfied, a signal of successful static compensation is sent out, and if the condition of static compensation is not satisfied, a signal of failed static compensation is sent out. The static compensation condition can be preset, and further, the static compensation condition can include a single-phase current amplitude condition and a differential pressure amplitude condition, but is not limited to the conditions, and can also include other conditions such as an inter-phase current amplitude condition and a system voltage amplitude condition.
The dynamic compensation method is used for compensating the neutral point differential pressure according to a preset periodic value in the operation process of the capacitor based on the effective value of the phase current, the effective value of the bus zero-sequence voltage and the effective value of the neutral point voltage, and periodically compensating dynamic errors caused by temperature, humidity and internal element aging in the operation process of the capacitor bank. And performing dynamic compensation according to a preset dynamic compensation condition. If the dynamic compensation time condition is satisfied, a dynamic compensation success signal is sent out, and if the dynamic compensation condition is not satisfied, a dynamic compensation failure signal is sent out. The dynamic compensation condition can be preset, and further, the dynamic compensation condition can include a dynamic compensation period, a single-phase current amplitude condition, a differential pressure amplitude condition, but is not limited to this condition, and can also include other conditions such as an inter-phase current amplitude condition and a system voltage amplitude condition.
And 150, initiating an alarm signal or a protection trip signal when the compensated neutral point differential pressure exceeds an alarm threshold or a protection threshold. Wherein the alarm threshold corresponds to a low differential pressure limit at which all remaining normal cells of the capacitor bank can remain operational to withstand overvoltage. Wherein the protection threshold corresponds to a high differential pressure limit at which all remaining normal cells of the capacitor bank cannot continue to operate and can withstand overvoltage.
And step 210, after setting a fixed value control alarm or a fault occurs, judging whether to execute a fault positioning function according to the condition of the zero sequence voltage of the bus.
And step 230, judging whether the effective angle difference is in the characteristic ranges of 180 degrees, 60 degrees, -60 degrees, 0 degrees, -120 degrees and 120 degrees.
In this embodiment, the capacitor unit is an internal fuse. Referring to fig. 3a, when phase a of the capacitor bank fails, the theoretical calculated angular difference should be 0 °; when the B phase of the capacitor bank fails, theoretically calculating the angular difference to be 120 degrees; when the capacitor bank phase C fails, the theoretical calculated angular difference should be-120 °. In particular, considering the measurement error and the influence of inductive and resistive components in the capacitor, the actual effective angular difference determination can be improved by increasing the angular offset range θ, which can be preset according to the actual condition of the capacitor, and can be generally set to the interval of [5 °,30 ° ]. According to the characteristic range determination method, the effective angular difference characteristic range of the A-phase fault is 0 degrees +/-theta, the effective angular difference characteristic range of the B-phase fault is 120 degrees +/-theta, and the effective angular difference characteristic range of the C-phase fault is-120 degrees +/-theta. Similarly, the outer fuse type capacitor effective angular difference characteristic range decision is the same as the inner fuse effective angular difference characteristic range decision.
Referring to fig. 3B, in the case of the fuse-less type capacitor, the effective angular difference characteristic range of the a-phase fault is 180 ° ± θ, the effective angular difference characteristic range of the B-phase fault is 60 ° ± θ, and the effective angular difference characteristic range of the C-phase fault is-60 ° ± θ.
When a capacitor bank fails, a change in the neutral point voltage is caused. The fault may involve an internal or intercell fault of a single or multiple capacitor cells. The fault can be identified by detecting the neutral point differential pressure. If a fault occurs outside the capacitor resulting in a bus voltage, the capacitor bank neutral still develops a voltage even though the capacitor bank body is normal. In addition, due to the installation difference of the capacitors, the error of the measuring unit, the change of the environmental temperature, the aging of the capacitor devices and other reasons, the voltage of the neutral point of the capacitor bank is generated under the condition of unbalance of the system voltage. Normal capacitor neutral voltage may result in an alarm or protection trip signal due to the additive effects of such factors as external system imbalance, installation and operating condition differences, etc. In addition, once capacitor fault happens and capacitor protection action trips, the capacitor bank is disconnected with the system, the voltage of the capacitor end rapidly decays through an internal discharge loop, the voltage of a neutral point disappears, and at the moment, the fault position of the capacitor is located only through a one-by-one screening mode, so that operation and maintenance are complex, and a large amount of time is consumed. According to the invention, the problem of capacitor bank protection misoperation caused by external system unbalance is solved by adopting a neutral point differential pressure method.
In addition, by using static compensation and dynamic compensation methods, system errors and dynamic errors caused by capacitor installation and operation condition changes are solved.
The invention has the further advantage that the fault phase is determined according to the angular difference between the neutral point differential pressure and the bus positive sequence voltage at the moment of alarming or protecting action. Theoretically, after the fault phase is determined, the other two phases are eliminated, and only the capacitor unit in the fault phase needs to be further detected, so that the invention can save 66.7% of fault detection positioning time.
Apparatus example 1:
the embodiment 1 of the capacitor protection device is used for detecting internal faults of a Y-shaped capacitor bank with a neutral point grounded through PT, the capacitor bank is in three-phase Y-shaped connection, the neutral point of the Y-shaped connected capacitor bank is grounded through PT, the capacitor bank is formed by connecting a plurality of capacitor units in series or in parallel, parameters and configuration modes of the capacitor units are the same, and the internal faults of the capacitor bank occur in internal elements of the capacitor units or among the capacitor units; the capacitor bank is provided with a first current transformer for measuring the three-phase current of the capacitor bank; arranging a first voltage transformer for measuring the three-phase voltage of a bus connected with the capacitor bank; arranging a second voltage transformer for measuring the neutral point voltage of the capacitor bank; the capacitor protection device includes: the device comprises a computing unit, a protection unit and a fault positioning unit; wherein:
the calculating unit is used for receiving the voltage, the three-phase current of the capacitor bank measured by the current transformer, the three-phase voltage of a bus connected with the capacitor bank and the neutral point voltage of the capacitor bank; calculating effective values of three-phase currents of the capacitor bank; and calculating the effective value, the effective value and the phase of the three-phase voltage of the bus connected with the capacitor bank, and the effective value and the phase of the zero-sequence voltage of the bus connected with the capacitor bank.
And the protection unit is used for judging that an alarm signal is generated when the differential pressure value of the neutral point exceeds an alarm threshold value, and a protection tripping signal is generated when the differential pressure value of the neutral point exceeds a protection threshold value.
The fault positioning unit comprises an effective angular difference calculation module, an angular difference characteristic judgment module and a fault phase positioning module, wherein:
the effective angular difference calculation module is used for calculating the effective angular difference between the differential pressure of the neutral point and the positive sequence voltage of the bus;
the angular difference characteristic judging module judges whether the effective angular difference is within the characteristic ranges of 180 degrees, 60 degrees, -60 degrees, 0 degrees, -120 degrees and 120 degrees;
the fault phase positioning module is used for determining a fault phase according to the effective angular difference and the angular difference characteristics 。
Apparatus example 2:
an embodiment 2 of a capacitor protection device of the present invention is a capacitor protection device for detecting an internal fault of a Y-type capacitor bank having a neutral point grounded via PT, wherein the capacitor bank is connected in a three-phase Y-type manner, the neutral point of the Y-type capacitor bank is grounded via PT, the capacitor bank is formed by connecting a plurality of capacitor units in series or in parallel, parameters and configuration modes of the capacitor units are the same, and the internal fault of the capacitor bank occurs in an internal element of the capacitor unit or between the capacitor units; the capacitor bank is provided with a first current transformer for measuring the three-phase current of the capacitor bank; arranging a first voltage transformer for measuring the three-phase voltage of a bus connected with the capacitor bank; arranging a second voltage transformer for measuring the neutral point voltage of the capacitor bank; the capacitor protection device includes: the device comprises a calculation unit, a protection unit, a fault positioning unit and a compensation unit; wherein:
the calculating unit is used for receiving the voltage, the three-phase current of the capacitor bank measured by the current transformer, the three-phase voltage of a bus connected with the capacitor bank and the neutral point voltage of the capacitor bank; calculating effective values of three-phase currents of the capacitor bank; and calculating the effective value, the effective value and the phase of the three-phase voltage of the bus connected with the capacitor bank, and the effective value and the phase of the zero-sequence voltage of the bus connected with the capacitor bank.
The compensation unit comprises a static compensation module and/or a dynamic compensation module.
And the static compensation module is used for compensating the differential pressure of the neutral point at the initial stage of the operation of the capacitor based on the effective value of the phase current, the effective value of the zero sequence voltage of the bus and the effective value of the voltage of the neutral point, and making up inherent errors caused by process errors, installation errors and system errors of the measuring elements of the capacitor bank.
And the dynamic compensation module is used for compensating the differential pressure of the neutral point according to a preset periodic value in the operation process of the capacitor based on the effective value of the phase current, the effective value of the zero sequence voltage of the bus and the effective value of the voltage of the neutral point, and periodically compensating dynamic errors caused by the temperature, the humidity and the aging of internal elements in the operation process of the capacitor bank.
And the protection unit is used for generating an alarm signal when judging that the neutral point differential pressure value compensated by the compensation unit exceeds an alarm threshold value and generating a protection tripping signal when the neutral point differential pressure value exceeds a protection threshold value.
The fault positioning unit comprises an effective angular difference calculation module, an angular difference characteristic judgment module and a fault phase positioning module, wherein:
the effective angular difference calculation module is used for calculating the effective angular difference between the differential pressure of the neutral point and the positive sequence voltage of the bus;
the angular difference characteristic judging module judges whether the effective angular difference is within the characteristic ranges of 180 degrees, 60 degrees, -60 degrees, 0 degrees, -120 degrees and 120 degrees;
the fault phase positioning module is used for determining a fault phase according to the effective angular difference and the angular difference characteristics 。
Apparatus example 3:
an embodiment 3 of the capacitor protection device of the present invention is configured to detect an internal fault of a Y-type capacitor bank in which a neutral point is grounded via PT, where the capacitor bank is in a three-phase Y-type connection, the neutral point of the Y-type connected capacitor bank is grounded via PT, the capacitor bank is formed by connecting a plurality of capacitor units in series or in parallel, parameters and configuration modes of the capacitor units are the same, and the internal fault of the capacitor bank occurs in an internal element of the capacitor unit or between the capacitor units; the capacitor bank is provided with a first current transformer for measuring the three-phase current of the capacitor bank; arranging a first voltage transformer for measuring the three-phase voltage of a bus connected with the capacitor bank; arranging a second voltage transformer for measuring the neutral point voltage of the capacitor bank; the capacitor protection device includes: the device comprises a calculation unit, a protection unit, a fault positioning unit and a compensation unit; wherein:
the calculating unit is used for receiving the voltage, the three-phase current of the capacitor bank measured by the current transformer, the three-phase voltage of a bus connected with the capacitor bank and the neutral point voltage of the capacitor bank; calculating effective values of three-phase currents of the capacitor bank; and calculating the effective value, the effective value and the phase of the three-phase voltage of the bus connected with the capacitor bank, and the effective value and the phase of the zero-sequence voltage of the bus connected with the capacitor bank.
The compensation unit comprises a static compensation module and/or a dynamic compensation module.
And the static compensation module is used for compensating the differential pressure of the neutral point at the initial stage of the operation of the capacitor based on the effective value of the phase current, the effective value of the zero-sequence voltage of the bus and the effective value of the voltage of the neutral point, and making up the inherent errors caused by the process error, the installation error and the system error of the measuring element of the capacitor bank.
The dynamic compensation module is used for compensating the neutral point differential pressure according to a preset periodic value in the operation process of the capacitor based on the effective value of the phase current, the effective value of the bus zero-sequence voltage and the effective value of the neutral point voltage, and periodically compensating dynamic errors caused by the temperature, the humidity and the aging of internal elements in the operation process of the capacitor bank.
And the protection unit is used for generating an alarm signal when judging that the neutral point differential pressure value compensated by the compensation unit exceeds an alarm threshold value and generating a protection tripping signal when the neutral point differential pressure value exceeds a protection threshold value.
The fault positioning unit comprises a fixed value module, an effective angular difference calculation module, an angular difference characteristic judgment module and a fault phase positioning module, wherein:
and the fixed value module is used for judging whether a fault positioning function is put into or not according to the neutral point differential pressure fault positioning input fixed value.
And the effective angular difference calculation module is used for calculating the effective angular difference between the differential pressure of the neutral point and the positive sequence voltage of the bus.
The angular difference characteristic judging module judges whether the effective angular difference is within the characteristic ranges of 180 degrees, 60 degrees, -60 degrees, 0 degrees, -120 degrees and 120 degrees.
The fault phase positioning module is used for determining a fault phase according to the effective angular difference and the angular difference characteristics 。
Apparatus example 4:
an embodiment 4 of the capacitor protection device of the present invention is described with reference to fig. 2. The three phases of the capacitor bank are correspondingly connected with the A, B, C three phases of the power system respectively, and the neutral point of the capacitor bank is grounded through 1VT. The system comprises a first current transformer CT-A, CT-B, CT-C for measuring three-phase currents IA, IB and IC of a capacitor, a first voltage transformer 3VTs for measuring three-phase bus voltage, and a second voltage transformer 1VT for measuring neutral point voltage of a capacitor bank.
The capacitor protection device 1 for detecting an internal fault of a capacitor bank comprises: a calculation unit 2, a compensation unit 3, a protection unit 4 and a fault localization unit 5.
Each phase of the capacitor is composed of a plurality of capacitor units CU in series/parallel connection, and each phase is arranged in the same way. In this example, each phase capacitor is configured by capacitor cells in a 2-to-4 string manner.
However, it should be noted that the present invention is not limited to this specific configuration. It should be noted that the capacitor unit is selected as an internal fuse type in this example, but the present invention is also applicable to an external fuse and a fuse-less capacitor bank.
The calculation unit 2 is connected to a first current transformer CT-A, CT-B, CT-C of a capacitor three phase A, B, C, also to a first voltage transformer 3VTs of the three phase bus voltage and to a second voltage transformer 1VT of the capacitor bank neutral voltage. The calculation unit 2 receives measurement results from the first current transformer, the first voltage transformer, and the second voltage transformer and performs calculation. All measurements are based on equally spaced instantaneous samples of current, voltage. The sampled data is stored in an internal storage unit for effective value and phase calculations.
In addition, the calculating unit 2 calculates the neutral point differential pressure according to the zero sequence voltage and the neutral voltage of the system obtained by measurement and calculation:
wherein, the first and the second end of the pipe are connected with each other,
for a calculated zero-sequence voltage of the busbar>
Is a measured value of the neutral point voltage of the capacitor>
The neutral point differential pressure value is obtained.
The compensation unit 3 comprises a static compensation module and/or a dynamic compensation module.
The static compensation module is used for compensating the differential pressure of the neutral point at the initial stage of the operation of the capacitor based on the effective value of the phase current, the effective value of the zero-sequence voltage of the bus and the effective value of the voltage of the neutral point, and making up inherent errors caused by process errors, installation errors and system errors of a measuring element of the capacitor bank;
and the dynamic compensation module is used for compensating the neutral point differential pressure according to a preset periodic value in the operation process of the capacitor based on the effective value of the phase current, the effective value of the bus zero-sequence voltage and the effective value of the neutral point voltage, and periodically compensating dynamic errors caused by the temperature, the humidity and the aging of internal elements in the operation process of the capacitor bank.
The compensation unit 3 is configured to communicate with the calculation unit 2, and to trigger the static compensation manually based on the current, differential pressure measured and calculated by the calculation unit 2. And the capacitor bank needs to be in an operating state at the compensation moment, and the measurement and calculation results of the three-phase voltage of the bus, the current of the capacitor bank and the neutral point voltage of the capacitor bank meet the static compensation condition. If the condition of triggering the static compensation is satisfied, a signal of successful static compensation is sent out, and if the condition of static compensation is not satisfied, a signal of failed static compensation is sent out. The static compensation condition can be preset, and further, the static compensation condition can include a single-phase current amplitude condition and a differential pressure amplitude condition, but is not limited to the conditions, and can also include other conditions such as a phase-to-phase current amplitude condition and a system voltage amplitude condition.
In addition, a dynamic compensation function may be engaged during normal operation of the capacitor bank. And performing dynamic compensation according to a preset dynamic compensation condition. If the dynamic compensation time condition is satisfied, a dynamic compensation success signal is sent out, and if the dynamic compensation condition is not satisfied, a dynamic compensation failure signal is sent out. The dynamic compensation condition can be preset, and further, the dynamic compensation condition can include a dynamic compensation period, a single-phase current amplitude condition, a differential pressure amplitude condition, but is not limited to this condition, and can also include other conditions such as an inter-phase current amplitude condition and a system voltage amplitude condition.
The invention effectively eliminates the inherent error of the system for installing and measuring the loop and the dynamic error caused by operation and aging operation.
The protection unit 4 is configured to communicate with the compensation unit 3, calculating a resulting neutral point differential pressure based on the compensation unit 3. And when the calculated neutral point differential pressure after static compensation and dynamic compensation is compared with an alarm threshold value and a protection threshold value, an alarm signal or a protection trip signal is generated.
The fault positioning unit 5 comprises a constant value module, an execution judgment module, an effective angular difference calculation module, an angular difference characteristic judgment module and a fault phase positioning module, wherein:
the fault localization unit 5 is configured to communicate with the protection unit 4. And when an alarm signal or a protection trip signal is monitored, the fixed value module is used for inputting fixed value control according to the differential pressure fault positioning of the neutral point to enter a fault positioning processing logic. If the fault positioning function is not put into use, the subsequent functions are ignored and directly returned. And if the fault positioning function is put into operation, carrying out subsequent fault positioning detection.
Before entering the fault location detection and judgment, the execution judgment module can further judge whether the calculated bus zero-sequence voltage meets the fault location condition. The execution judgment module may not be provided.
And the effective angular difference calculation module calculates the compensated neutral point differential pressure and the calculated bus positive sequence voltage effective angular difference. It should be noted that the angular difference calculation is performed only at the moment when the differential pressure alarm signal or the protection trip signal is monitored.
And the angular difference characteristic judging module is used for judging whether the effective angular difference is in the characteristic ranges of 180 degrees, 60 degrees, -60 degrees, 0 degrees, -120 degrees and 120 degrees. In this embodiment, the capacitor unit is an internal fuse. Referring to fig. 3a, when phase a of the capacitor bank fails, the theoretical calculated angular difference should be 0 °; when the B phase of the capacitor bank fails, theoretically calculating the angular difference to be 120 degrees; when the capacitor bank phase C fails, the theoretical calculated angular difference should be-120 deg.. In particular, considering the measurement error and the influence of inductive and resistive components in the capacitor, the actual effective angular difference determination can improve the characteristic determination by increasing the angular offset range θ, which can be preset according to the actual condition of the capacitor, and can be set to a range of [5 ° and 30 ° ]. According to the characteristic range determination method, the effective angular difference characteristic range of the A-phase fault is 0 degrees +/-theta, the effective angular difference characteristic range of the B-phase fault is 120 degrees +/-theta, and the effective angular difference characteristic range of the C-phase fault is-120 degrees +/-theta. Similarly, the outer fuse type capacitor effective angular difference characteristic range decision is the same as the inner fuse effective angular difference characteristic range decision.
Referring to fig. 3B, in the case of the fuse-less type capacitor, the effective angular difference characteristic range of the a-phase fault is 180 ° ± θ, the effective angular difference characteristic range of the B-phase fault is 60 ° ± θ, and the effective angular difference characteristic range of the C-phase fault is-60 ° ± θ.
A fault phase positioning module for determining fault phase according to the effective angular difference and angular difference characteristics 。
The above embodiments are only for illustrating the technical idea of the present invention, and the technical idea of the present invention is not limited thereto, and any modifications made on the basis of the technical solution according to the technical idea of the present invention fall within the protective scope of the present invention.
Claims (11)
1. An internal fault detection method for a capacitor bank, which is used for detecting an internal fault of a Y-type capacitor bank with a neutral point grounded through PT, wherein the capacitor bank is in three-phase Y-type wiring, the neutral point is grounded through PT, the capacitor bank is formed by connecting a plurality of capacitor units in series or in parallel, parameters and configuration modes of the capacitor units are the same, and the internal fault of the capacitor bank occurs in internal elements of the capacitor units or among the capacitor units, the internal fault detection method is characterized by comprising the following steps:
step 100, measuring the three-phase current of the capacitor bank
Calculating an effective value of the phase current;
step 110, measuring the three-phase voltage of the bus connected with the capacitor bank and calculating the positive sequence voltage
Zero sequence voltage->
Step 120, measuring the neutral point voltage of the capacitor bank
Step 130, calculating a neutral point differential pressure according to the bus zero sequence voltage and the neutral point voltage of the capacitor bank
150, initiating an alarm signal or a protection trip signal when the differential pressure of the neutral point exceeds an alarm threshold or a protection threshold;
step 220, calculating an effective angular difference between the neutral point differential pressure and the bus positive sequence voltage
Step 230, judging whether the effective angle difference is in the characteristic ranges of 180 degrees, 60 degrees, -60 degrees, 0 degrees, -120 degrees and 120 degrees;
step 240, determining a fault phase according to the effective angular difference and the angular difference characteristics 。
2. The method of claim 1, further comprising, after step 130 and before step 150:
140, compensating the differential pressure of the neutral point by adopting a static compensation method and/or a dynamic compensation method;
in step 150, an alarm signal or a protection trip signal is initiated when the compensated neutral point differential pressure exceeds an alarm threshold or a protection threshold.
3. The method as claimed in claim 2, wherein the static compensation method in step 140 is used for compensating the neutral point differential pressure in the initial stage of the capacitor operation based on the effective value of the phase current, the effective value of the bus zero sequence voltage and the effective value of the neutral point voltage, so as to compensate the inherent errors caused by the process error, the installation error and the system error of the measuring element of the capacitor bank.
4. The method as claimed in claim 2, wherein the dynamic compensation method in step 140 is used for compensating the neutral point differential pressure according to a preset period value during the operation of the capacitor based on the effective value of the phase current, the effective value of the bus zero sequence voltage and the effective value of the neutral point voltage, so as to periodically compensate the dynamic errors caused by the temperature, humidity and aging of internal components during the operation of the capacitor bank.
5. A method for detecting faults within a capacitor bank as claimed in claim 1, wherein said alarm threshold corresponds to a low differential pressure limit at which all remaining normal cells of said capacitor bank can sustain overvoltage for continued operation.
6. A method for detecting faults within a capacitor bank as claimed in claim 1, wherein the protection threshold corresponds to a high differential pressure limit at which all remaining normal cells of the capacitor bank cannot continue to operate and can withstand overvoltage.
7. The method of claim 1, further comprising, after step 150:
step 200, setting a fixed value to control whether to trigger a fault positioning function after an alarm or a fault occurs.
8. A method of detecting faults within a capacitor bank as claimed in claim 1, further comprising, after step 150:
and step 210, after setting a fixed value control alarm or a fault occurs, judging whether to execute a fault positioning function according to the condition of the zero sequence voltage of the bus.
9. A capacitor protection device is used for detecting internal faults of a Y-shaped capacitor bank with a neutral point grounded through PT, the capacitor bank is in three-phase Y-shaped connection, the neutral point of the Y-shaped connected capacitor bank is grounded through PT, the capacitor bank is formed by connecting a plurality of capacitor units in series or in parallel, parameters and configuration modes of the capacitor units are the same, and the internal faults of the capacitor bank occur in internal elements of the capacitor units or among the capacitor units; the capacitor bank is provided with a first current transformer for measuring the three-phase current of the capacitor bank; arranging a first voltage transformer for measuring the three-phase voltage of a bus connected with the capacitor bank; arranging a second voltage transformer for measuring the neutral point voltage of the capacitor bank; characterized in that the capacitor protection device comprises: the device comprises a computing unit, a protection unit and a fault positioning unit; wherein:
the calculating unit is used for receiving the voltage, the three-phase current of the capacitor bank measured by the current transformer, the three-phase voltage of a bus connected with the capacitor bank and the neutral point voltage of the capacitor bank; calculating effective values of three-phase currents of the capacitor bank; calculating the effective value, the effective value and the phase of the three-phase voltage of the bus connected with the capacitor bank, and the effective value and the phase of the zero-sequence voltage of the bus connected with the capacitor bank, and calculating the effective value and the phase of the neutral point voltage of the capacitor bank; calculating a neutral point differential pressure according to the bus zero sequence voltage and the neutral point voltage of the capacitor bank;
the protection unit is used for judging that an alarm signal is generated when the differential pressure value of the neutral point exceeds an alarm threshold value, and a protection trip signal is generated when the differential pressure value of the neutral point exceeds a protection threshold value;
the fault positioning unit comprises an effective angular difference calculation module, an angular difference characteristic judgment module and a fault phase positioning module, wherein:
the effective angular difference calculation module is used for calculating the effective angular difference between the differential pressure of the neutral point and the positive sequence voltage of the bus;
the angular difference characteristic judging module judges whether the effective angular difference is within the characteristic ranges of 180 degrees, 60 degrees, -60 degrees, 0 degrees, -120 degrees and 120 degrees;
the fault phase positioning module is used for determining a fault phase according to the effective angular difference and the angular difference characteristics 。
10. The capacitor protection device of claim 9, further comprising a compensation unit comprising a static compensation module and/or a dynamic compensation module;
the static compensation module is used for compensating the differential pressure of the neutral point at the initial stage of the operation of the capacitor based on the effective value of the phase current, the effective value of the zero-sequence voltage of the bus and the effective value of the voltage of the neutral point, and making up inherent errors caused by process errors, installation errors and system errors of the measuring elements of the capacitor bank;
the dynamic compensation module is used for compensating the differential pressure of the neutral point according to a preset periodic value in the operation process of the capacitor based on the effective value of the phase current, the effective value of the zero sequence voltage of the bus and the effective value of the voltage of the neutral point, and periodically compensating dynamic errors caused by the temperature, the humidity and the aging of internal elements in the operation process of the capacitor bank;
and the protection unit is used for generating an alarm signal when judging that the neutral point differential pressure value compensated by the compensation unit exceeds an alarm threshold value and generating a protection tripping signal when the neutral point differential pressure value exceeds a protection threshold value.
11. The capacitor protection device of claim 9, wherein the fault location unit further comprises a valuing module, an execution determining module; wherein:
the fixed value module is used for judging whether a fault positioning function is put into or not according to the neutral point differential pressure fault positioning put-in fixed value;
and the execution judgment module is used for judging whether the calculated bus zero-sequence voltage meets the fault positioning condition or not, and if so, executing the effective angular difference calculation module.
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| CN112721641B (en) * | 2020-12-17 | 2023-05-12 | 联合汽车电子有限公司 | Fault diagnosis method and fault diagnosis device for automobile voltage converter |
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