CN111244895B - Rotor grounding protection circuit, method and device suitable for working condition of rotor voltage fluctuation - Google Patents
Rotor grounding protection circuit, method and device suitable for working condition of rotor voltage fluctuation Download PDFInfo
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/06—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for dynamo-electric generators; for synchronous capacitors
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- 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
- H02H1/003—Fault detection by injection of an auxiliary voltage
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Abstract
The invention discloses a rotor ground protection circuit, a method and a device suitable for a rotor voltage fluctuation working condition, wherein the rotor ground protection circuit adopts a direct current double-end injection switching sampling loop to respectively measure rotor voltage, rotor positive leakage current and rotor negative leakage current, the method corrects and filters sampling data, solves the rotor voltage when S is switched on, the rotor ground resistance and the rotor ground position as unknown quantities according to the loop characteristics of the two states of the switch S which is switched on and off to obtain a rotor ground resistance, a rotor ground position and a rotor voltage calculated value, judges whether the measuring loop is normal or not by comparing whether the difference value of the rotor voltage calculated value and a rotor voltage measuring reference value in a corresponding time period is larger than a threshold value, and protects tripping if the rotor ground resistance is smaller than a fixed value under the condition that the measuring loop is normal. The invention can realize that the locking protection is not needed when the voltage of the rotor fluctuates, is suitable for the working condition of the voltage fluctuation of the rotor, has no influence of the grounding position of the rotor on the sensitivity and has higher measurement precision.
Description
Technical Field
The invention relates to the technical field of generator-transformer group relay protection, in particular to a rotor grounding protection circuit, a method and a device suitable for a rotor voltage fluctuation working condition.
Background
The rotor grounding protection is the main protection of the generator rotor winding and is an important component in the relay protection of the generator. The rotor ground protection is mainly divided into power supply injection type rotor ground protection and ping-pong switching type rotor ground protection at present. The injection power supply type rotor grounding protection can also detect the insulation of the rotor winding to the ground when the machine is stopped, and the application condition is wider. The presently disclosed injection type rotor ground protection mainly includes two modes, i.e., a direct current injection type and a square wave injection type. Direct current injection type rotor ground protection, square wave injection type rotor ground protection and ping-pong switching type rotor ground protection have poor measurement accuracy of rotor ground resistance when the voltage fluctuation of a rotor is large, even locking is required, and the applicable working condition is limited to a certain extent.
Disclosure of Invention
The invention aims to provide a rotor ground protection circuit, a method and a device suitable for the working condition of rotor voltage fluctuation, which can avoid frequent locking of protection when the rotor voltage fluctuates and improve the reliability of rotor ground protection by improving the measurement precision when the rotor voltage fluctuates.
The technical scheme adopted by the invention is as follows:
on one hand, the invention provides a rotor ground protection circuit suitable for the working condition of rotor voltage fluctuation, a rotor large shaft is connected with the negative end of a direct current power supply E, the positive end of the rotor is connected with the positive end of the direct current power supply E through at least one resistor R1, the negative end of the rotor is connected with the positive end of the direct current power supply E through at least one resistor R2 and a resistor R3, and two ends of the resistor R2 or the resistor R3 are connected with a controllable switch S in parallel;
the positive end and the negative end of the rotor are connected with a voltage measuring unit V1 in parallel, a current measuring unit A1 is arranged on a line connecting the positive end of the direct current power supply E and the positive end of the rotor through a resistor R1, and a current measuring unit A2 is arranged on a line connecting the negative end of the direct current power supply E and the negative end of the rotor through resistors R2 and R3.
Optionally, the positive end of the rotor is connected to the positive end of the dc power supply E through a high-power resistor R1, the negative end of the rotor is connected to the positive end of the dc power supply E through high-power resistors R2 and R3, and the two ends of the resistor R3 are connected in parallel to a controllable switch S.
Optionally, the resistances of the resistors R1, R2, and R3 are equal. And the calculation is more convenient. The controllable switch can adopt the existing electronic change-over switch.
In a second aspect, the present invention provides a rotor ground protection method based on the rotor ground protection circuit in the first aspect, including:
controlling the switching of the on-off state of the controllable switch at a set frequency;
sampling the rotor voltage, the rotor positive leakage current and the rotor negative leakage current at a set sampling rate to obtain a real-time sampling value;
according to the rotor voltage, the rotor positive leakage current and the rotor negative leakage current during the state maintenance period of each controllable switch, correcting and calculating to obtain the rotor voltage, the rotor positive leakage current and the rotor negative leakage current measurement reference values at corresponding time intervals;
according to the rotor positive leakage current and the rotor negative leakage current measurement reference values obtained through correction calculation, the rotor grounding protection loop equation under the two states of opening and closing of the controllable switch is utilized to solve the rotor voltage, the rotor grounding resistance and the rotor grounding position under the two states of opening and closing adjacent to the controllable switch, and real-time grounding resistance, rotor grounding position and real-time rotor voltage calculation values are obtained;
comparing real-time rotor voltage calculation values under two states of adjacent opening and closing of the controllable switches with rotor voltage measurement reference values at corresponding time intervals respectively;
in response to the two states of opening and closing before and after the switching of the controllable switch, the difference value between the real-time rotor voltage calculation value and the rotor voltage measurement reference value at the corresponding moment is larger than a preset threshold value, and the rotor is locked to be in ground protection for the duration of the switching period of at least one controllable switch;
and responding to the condition that the rotor grounding protection is not locked and the real-time rotor grounding resistance is smaller than the action setting value, and then the rotor grounding protection acts.
Optionally, the method further includes low-pass filtering the rotor voltage, the rotor positive leakage current, and the rotor negative leakage current. The cut-off frequency of the low-pass filtering is 4Hz, and the low-pass filtering can adopt the existing hardware filtering mode.
Optionally, the switching time of the controllable switch is defined as the current time, and the sampling points of the corresponding rotor voltage, the rotor positive leakage current and the rotor negative leakage current are respectively U f (n)、I p (n)、I n (n)；
The correction calculation is performed based on the rotor voltage, the rotor positive leakage current and the rotor negative leakage current after the low-pass filtering, and comprises the following steps: and calculating the average value of the rotor voltage, the rotor positive leakage current and the rotor negative leakage current in a set time interval before the switching of the controllable switch, and correcting. The obtained value is the measurement reference value of the set time period before the sampling point n.
Optionally, the correction calculation is performed according to the following formula:
wherein N is the number of sampling points per cycle, and the point number N-N represents the forward push N/f from the corresponding time of the sampling point N s Sampling point number of time corresponding to duration, f s For the sampling rate, U f0 、I p0 、I n0 For zero drift correction value, U fa 、I pa 、I na The measured reference values of the rotor voltage, the rotor positive leakage current and the rotor negative leakage current are respectively, namely N/f before the current moment (before the switch is switched) s And measuring reference values of the rotor voltage, the rotor positive leakage current and the rotor negative leakage current of the time interval.
Optionally, before and after one-time switch switching, when the switch S is in an open state, the measurement reference values of the rotor positive leakage current and the rotor negative leakage current are respectively I pa1 、I na1 When the switch S is closed, the reference values for measuring the positive leakage current and the negative leakage current of the rotor are respectively I pa2 、I na2 ；
Utilizing a rotor ground protection loop equation under two adjacent opening and closing states of the controllable switch:
s is opened:
s is closed:
the rotor voltage U in the S-open state f1 S rotor voltage U in closed state f2 Rotor grounding resistance R g Rotor grounding position alpha as unknownAnd (3) carrying out equation solution to obtain the real-time rotor grounding resistance and rotor grounding position as follows:
and rotor voltage U f1 、U f2 The real-time rotor voltage calculation value is:
optionally, the rotor voltage measurement reference values in the on-off state of the switch are defined as U respectively fa1 、U fa2 In response to:
the locked rotor ground protects the duration of the switching cycle of the at least one controllable switch.
Optionally, in response to that the rotor ground protection is not locked and the real-time rotor ground resistance calculated value is smaller than the action setting value, the rotor ground protection acts after the state lasts for the duration of the switching period of the at least one controllable switch. The protection reliability can be further improved.
In a third aspect, the present invention provides a rotor ground protection device based on the rotor ground protection circuit in the first aspect, including:
the switch control module is configured to control the on-off state switching of the controllable switch at a set frequency;
the circuit sampling module is configured for sampling the rotor voltage, the rotor positive leakage current and the rotor negative leakage current at a set sampling rate to obtain a real-time sampling value;
the measurement reference value calculation module is configured for correcting and calculating to obtain measurement reference values of the rotor voltage, the rotor positive leakage current and the rotor negative leakage current in corresponding time periods according to the rotor voltage, the rotor positive leakage current and the rotor negative leakage current during the state maintenance period of each controllable switch;
the protection calculation module is configured for solving rotor voltage, rotor grounding resistance and rotor grounding position under two adjacent opening and closing states of the controllable switch by utilizing a rotor grounding protection loop equation under the two states of opening and closing of the controllable switch according to the rotor positive leakage current and the rotor negative leakage current measurement reference value obtained through correction calculation to obtain a real-time grounding resistance, a rotor grounding position and a real-time rotor voltage calculation value;
the voltage comparison module is configured for comparing real-time rotor voltage calculation values under two states of opening and closing adjacent to the controllable switch with rotor voltage measurement reference values in corresponding time periods respectively;
in response to the two states of opening and closing before and after the switching of the controllable switch, the difference value between the real-time rotor voltage calculation value and the rotor voltage measurement reference value at the corresponding moment is larger than a preset threshold value, and the rotor is locked to be in ground protection for the duration of the switching period of at least one controllable switch;
and the protection logic judgment module responds to the condition that the rotor grounding protection is not locked and the real-time rotor grounding resistance is smaller than the action setting value, so that the rotor grounding protection acts.
The invention provides a rotor grounding protection system suitable for the working condition of rotor voltage fluctuation, which comprises:
a rotor grounding protection circuit and a rotor grounding protection device;
the rotor ground protection circuit is the rotor ground protection circuit of the first aspect, and the rotor ground protection device is the rotor ground protection device of the third aspect.
Advantageous effects
The invention can measure the grounding resistance of the rotor and the grounding position of the rotor at the same time by improving the grounding protection circuit of the rotor and providing a rotor grounding protection method considering the measurement precision of the measurement loop adaptively, thereby protecting the rotor from dead zones and being not influenced by the shutdown of a generator; the measuring precision of the rotor grounding resistance under the working condition of rotor voltage fluctuation can be improved, the locking of protection under the working condition of rotor voltage fluctuation is avoided, and the application range of rotor grounding protection is enlarged; and the calculated value of the rotor voltage is compared with the measured value, and then the loop condition is judged, so that the reliability of protection is improved.
Drawings
FIG. 1 is a schematic diagram of a rotor ground protection circuit;
FIG. 2 is a schematic flow chart illustrating a rotor protection method according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of a protection calculation waveform when the rotor winding is being grounded;
fig. 4 is a schematic diagram showing a protection calculation waveform when the rotor winding is negatively grounded.
Detailed Description
The following further description is made in conjunction with the accompanying drawings and the specific embodiments.
The invention idea is as follows: in direct-current double-end injection type rotor ground protection, a direct-current double-end injection switching sampling circuit is designed, rotor voltage, rotor positive leakage current and rotor negative leakage current are measured respectively, then filtering and correction are carried out on the rotor voltage, the rotor positive leakage current and the rotor negative leakage current sampling values in the same mode through an algorithm, then according to circuit characteristics of an electronic switch S in the sampling circuit under two states of opening and closing, the rotor voltage when S is opened, the rotor voltage when S is closed, the rotor ground resistance and the rotor ground position are used as unknown quantities to solve, and the rotor ground resistance and the rotor ground position are obtained in real time. In order to improve the reliability of protection, the obtained rotor voltage is compared with the rotor voltage measured at the same time, whether a measuring loop is normal or not is judged, and if the measuring loop is normal and the rotor grounding resistance is smaller than a fixed value, tripping is protected. The method does not need locking protection when the voltage of the rotor fluctuates, is suitable for the working condition of the voltage fluctuation of the rotor, has high sensitivity and high measurement precision and is not influenced by the grounding position of the rotor.
Example 1
The embodiment specifically describes a direct-current double-end injection switching sampling loop, that is, in the rotor ground protection circuit of the present invention, a rotor large shaft is connected to a negative end of a superimposed direct-current power supply E, a rotor positive end is connected to a positive end of the direct-current power supply E through at least a resistor R1, the rotor negative end is connected to the positive end of the direct-current power supply E through a resistor R2 and a resistor R3, and two ends of the resistor R3 are connected in parallel to a controllable switch S;
and the positive end and the negative end of the rotor are connected with a voltage measuring unit V1 in parallel, a current measuring unit A1 is arranged on a line connecting the positive end of the direct current power supply E and the positive end of the rotor through a resistor R1, and a current measuring unit A2 is arranged on a line connecting the negative end of the direct current power supply E and the negative end of the rotor through resistors R2 and R3.
The resistors R1, R2 and R3 are all high-power resistors, and the resistances of the resistors R1, R2 and R3 are equal, so that the calculation is more convenient at the time of correction calculation. The controllable switch can adopt the existing electronic change-over switch.
Example 2
Referring to fig. 2, the present embodiment is a rotor ground protection method based on the rotor ground protection circuit of embodiment 1, including:
controlling the switching state of a controllable switch (an electronic selector switch) S to be switched at a set frequency;
sampling the rotor voltage, the rotor positive leakage current and the rotor negative leakage current at a set sampling rate to obtain a real-time sampling value;
according to the rotor voltage, the rotor positive leakage current and the rotor negative leakage current during the state maintenance period of each controllable switch, correcting and calculating to obtain the rotor voltage, the rotor positive leakage current and the rotor negative leakage current measurement reference values at corresponding time intervals;
according to the rotor positive leakage current and the rotor negative leakage current measurement reference values obtained through correction calculation, the rotor grounding protection loop equation under the two states of opening and closing of the controllable switch is utilized to solve the rotor voltage, the rotor grounding resistance and the rotor grounding position under the two states of opening and closing adjacent to the controllable switch, and real-time grounding resistance, rotor grounding position and real-time rotor voltage calculation values are obtained;
comparing real-time rotor voltage calculation values under two states of adjacent opening and closing of the controllable switches with rotor voltage measurement reference values at corresponding time intervals respectively;
in response to the two states of opening and closing before and after the switching of the controllable switch, the difference value between the real-time rotor voltage calculation value and the rotor voltage measurement reference value at the corresponding moment is larger than a preset threshold value, and the rotor is locked to be in ground protection for the duration of the switching period of at least one controllable switch;
and responding to the condition that the rotor grounding protection is not locked and the real-time rotor grounding resistance is smaller than the action setting value, and then the rotor grounding protection acts.
The method further comprises low pass filtering the rotor voltage, the rotor positive leakage current, and the rotor negative leakage current. The cut-off frequency of the low-pass filtering is 4Hz, and the low-pass filtering can adopt the existing hardware filtering mode.
Defining the switching time of the controllable switch as the current time, and respectively setting the corresponding sampling points of the rotor voltage, the rotor positive leakage current and the rotor negative leakage current as U f (n)、I p (n)、I n (n)；
The correction calculation is performed based on the rotor voltage, the rotor positive leakage current and the rotor negative leakage current after the low-pass filtering, and comprises the following steps: and calculating the average value of the rotor voltage, the rotor positive leakage current and the rotor negative leakage current in the set time period before the switching of the controllable switch, and correcting to obtain the measurement reference value in the set time period before the sampling point n.
The correction calculation is performed according to the following formula:
wherein N is the number of sampling points per cycle, and the point number N-N represents the forward push N/f from the corresponding time of the sampling point N s Sampling point number of time corresponding to duration, f s For the sampling rate, U f0 、I p0 、I n0 For zero drift correction value, U fa 、I pa 、I na The measured reference values of the rotor voltage, the rotor positive leakage current and the rotor negative leakage current are respectively, namely N/f before the current moment (before the switch is switched) s And measuring reference values of the rotor voltage, the rotor positive leakage current and the rotor negative leakage current of the time interval.
Before and after one-time switch switching, the measurement reference values of rotor positive leakage current and rotor negative leakage current are respectively defined as I pa1 、I na1 When the switch S is closed, the rotor is in positive leakage current,The measurement reference values of the negative leakage current of the rotor are respectively I pa2 、I na2 ；
Utilizing a rotor ground protection loop equation under two states of adjacent opening and closing of the controllable switch:
s is opened:
s is closed:
the rotor voltage U in the S-open state f1 S rotor voltage U in closed state f2 Rotor grounding resistance R g And the rotor grounding position alpha is used as an unknown quantity, equation solution is carried out, and the real-time rotor grounding resistance and the rotor grounding position are obtained as follows:
and rotor voltage U f1 、U f2 The real-time rotor voltage calculation value is:
defining the rotor voltage measurement reference values to be U respectively under the on-off state of the switch fa1 、U fa2 In response to:
the locked rotor ground protects the duration of the switching cycle of the at least one controllable switch.
And responding to the condition that the rotor grounding protection is not locked and the real-time rotor grounding resistance calculated value is smaller than the action setting value, and after the state lasts for the duration of at least one controllable switch switching period, the rotor grounding protection acts. The protection reliability can be further improved.
Example 3
The present embodiment is a rotor ground protection device based on the rotor ground protection circuit in embodiment 1, including:
the switch control module is configured to control the on-off state switching of the controllable switch at a set frequency;
the circuit sampling module is configured for sampling the rotor voltage, the rotor positive leakage current and the rotor negative leakage current at a set sampling rate to obtain a real-time sampling value;
the measurement reference value calculation module is configured for correcting and calculating to obtain measurement reference values of the rotor voltage, the rotor positive leakage current and the rotor negative leakage current in corresponding time periods according to the rotor voltage, the rotor positive leakage current and the rotor negative leakage current during the state maintenance period of each controllable switch;
the protection calculation module is configured for solving a rotor voltage, a rotor grounding resistance and a rotor grounding position under two adjacent opening and closing states of the controllable switch by using a rotor grounding protection loop equation under the two states of opening and closing of the controllable switch according to the rotor positive leakage current and the rotor negative leakage current measurement reference value obtained by correction calculation to obtain a real-time grounding resistance, a rotor grounding position and a real-time rotor voltage calculation value;
the voltage comparison module is configured for comparing real-time rotor voltage calculation values under two states of opening and closing adjacent to the controllable switch with rotor voltage measurement reference values in corresponding time periods respectively;
in response to the two states of opening and closing before and after the switching of the controllable switch, the difference value between the real-time rotor voltage calculation value and the rotor voltage measurement reference value at the corresponding moment is larger than a preset threshold value, and the rotor is locked to be in ground protection for the duration of the switching period of at least one controllable switch;
and the protection logic judgment module responds to the condition that the rotor grounding protection is not locked and the real-time rotor grounding resistance is smaller than the action setting value, so that the rotor grounding protection acts.
The function of each module in this embodiment is implemented with reference to the corresponding content of the method in embodiment 2.
Example 4
This embodiment describes in detail a rotor ground protection system based on embodiment 1, embodiment 2, and embodiment 3, and is suitable for a rotor ground protection system under a condition of rotor voltage fluctuation, and includes: a rotor grounding protection circuit and a rotor grounding protection device;
the rotor ground protection circuit is the rotor ground protection circuit of embodiment 1, and the rotor ground protection device is the rotor ground protection device of embodiment 3, and its method of application embodiment 2 realizes rotor ground protection to avoid the protection shutting under the rotor voltage fluctuation operating mode, improve the protection reliability.
Specifically, the method comprises the following steps:
as shown in FIG. 1, in the DC double-end injection switching sampling loop, the negative end of the superimposed DC power supply E is connected with the B point of the rotor large axis, the positive end of the superimposed DC power supply E is connected with the high-power resistor R 1 Connected in series and then connected to the positive end of the rotor winding, and the positive end E is connected with a high-power resistor R 2 、R 3 Connected in series and then connected to the negative terminal of the rotor winding, R 2 Both ends are connected in parallel with an electronic change-over switch S. A current measuring unit and a voltage measuring unit are arranged in the circuit for measuring the rotor voltage U f Rotor positive leakage current I p And rotor negative leakage current I n 。
The two states of the electronic change-over switch S, namely opening and closing, are controlled by software through a rotor voltage protection device, and the switching period T is set to be 1S.
This embodiment provides a positive leakage current I to the rotor by hardware p Rotor negative leakage current I n The channel is low-pass filtered with a cut-off frequency of 4Hz.
Rotor voltage protection device is to rotor voltage U f Rotor positive leakage current I p And rotor negative leakage current I n Sampling is carried out to obtain a current sampling point U f (n)、I p (n) and I n (n) calculating the average value of the electronic change-over switch at the moment of 40ms before switching, and correcting to obtain the average value U of the rotor voltage fa Average value of positive leakage current of rotor pa Average value of negative leakage current of rotor I na The calculation formula is as follows:
wherein N is the number of sampling points per cycle, and the point number N-N represents the front N/f s Sampling point number of time, f s Is the device sampling rate, U f0 、I p0 、I n0 Is a zero drift correction value.
According to the measurement loop, aiming at the opening state and the closing state of S before and after one switching, the loop equation for listing the opening state of S is as follows:
in the formula I pa1 Rotor positive leakage current in S-on state, I na1 And the rotor negative leakage current is in an S opening state. U shape f1 Is the rotor voltage in the S-on state.
The S closed state loop equation is:
I pa2 rotor positive leakage current in S-closed state, I na2 Negative leakage current of rotor in S-closed state, U f2 Is the rotor voltage in the S-closed state. Let R 3 ＝R 2 ＝R 1 And (5) calculating the rotor grounding resistance R according to a loop equation under the two states of S opening and S closing g And rotor grounding position α:
rotor voltage U f1 、U f2 The real-time rotor voltage calculation value is:
to increase the reliability of the protection, the determined rotor voltage is compared with the rotor voltage measured at the same time, and whether the measurement loop is normal is determined, i.e.
In the formula of U fa1 Is the average value of the rotor voltage measurements at the moment 40ms before switching in the S-on state, U fa2 Is the average value of the rotor voltage measurements at the moment 40ms before switching in the S-closed state, U f1 Calculated value of rotor voltage at 40ms before switching in S-on state, U f2 And calculating the value of the rotor voltage at the moment of 40ms before switching in the S closed state, and if the conditions are met, immediately locking the protection, wherein the time for continuously locking the protection is at least 1S.
If the protection is not locked out and the measured resistance is less than the constant value (R) g <R set ，R set A constant value for actuation), which state is active for at least 1s of duration or more.
In order to display the test effect, a conventional rotor grounding resistance calculation formula R is provided g ＝-0.5R 1 +0.5I na1 R 1 /(I pa2 +I na2 -I pa1 -I na1 ) The formula is the rotor voltage U in the process of assuming S to open and close f And deducing on the basis of invariance. The rotor voltage is changed on the tester, and the calculation effect of the invention and the calculation effect of the conventional algorithm are obtained through calculation, as shown in fig. 3 to 4. Fig. 3 is a fault resistor of 5k Ω connected to the positive end of the rotor winding, and fig. 4 is a fault resistor of 10k Ω connected to the negative end of the rotor winding.
As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
While the present invention has been described with reference to the embodiments shown in the drawings, the present invention is not limited to the embodiments, which are illustrative and not restrictive, and it will be apparent to those skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (7)
1. A rotor ground protection method is characterized in that the method is realized based on a rotor ground protection circuit, in the rotor ground protection circuit, a rotor large shaft is connected with a negative end of a direct current power supply E, a rotor positive end is connected with a positive end of the direct current power supply E through at least one resistor R1, the rotor negative end is connected with the positive end of the direct current power supply E through at least one resistor R2 and a resistor R3, and two ends of the resistor R2 or the resistor R3 are connected with a controllable switch S in parallel; a voltage measuring unit V1 is connected in parallel to the positive end and the negative end of the rotor, a current measuring unit A1 is arranged on a line connecting the positive end of a direct current power supply E and the positive end of the rotor through a resistor R1, and a current measuring unit A2 is arranged on a line connecting the negative end of the direct current power supply E and the negative end of the rotor through resistors R2 and R3;
the rotor grounding protection method comprises the following steps:
controlling the switching of the on-off state of the controllable switch at a set frequency;
sampling the rotor voltage, the rotor positive leakage current and the rotor negative leakage current at a set sampling rate to obtain a real-time sampling value;
according to the rotor voltage, the rotor positive leakage current and the rotor negative leakage current during the state maintenance period of each controllable switch, correcting and calculating to obtain the rotor voltage, the rotor positive leakage current and the rotor negative leakage current measurement reference values at corresponding time intervals;
according to the rotor positive leakage current and the rotor negative leakage current measurement reference values obtained through correction calculation, the rotor grounding protection loop equation under the two states of opening and closing of the controllable switch is utilized to solve the rotor voltage, the rotor grounding resistance and the rotor grounding position under the two states of opening and closing adjacent to the controllable switch, and real-time grounding resistance, rotor grounding position and real-time rotor voltage calculation values are obtained;
comparing real-time rotor voltage calculation values under two states of adjacent opening and closing of the controllable switches with rotor voltage measurement reference values at corresponding time intervals respectively;
in response to the two states of opening and closing before and after the switching of the controllable switch, the difference value between the real-time rotor voltage calculation value and the rotor voltage measurement reference value at the corresponding moment is larger than a preset threshold value, and the rotor is locked to be in ground protection for the duration of the switching period of at least one controllable switch;
responding to the fact that the rotor grounding protection is not locked and the real-time rotor grounding resistance is smaller than the action setting value, and then the rotor grounding protection acts;
the equations of the rotor ground protection loop under the two adjacent opening and closing states of the controllable switch are as follows:
s is opened:
s is closed:
in the formula, in two states of opening and closing before and after one switch switching, I pa1 、I na1 Respectively measuring reference values of rotor positive leakage current and rotor negative leakage current in the state that the switch S is opened pa2 、I na2 Respectively measuring reference values of rotor positive leakage current and rotor negative leakage current under the closed state of a switch S; r g Representing the rotor ground resistance;
the rotor voltage U in the S-open state f1 S rotor voltage U in closed state f2 Rotor grounding resistance R g Taking the rotor grounding position alpha as an unknown quantity, and carrying out equation solution to obtain real-time rotor grounding resistance R g The position alpha grounded with the rotor is as follows:
rotor voltage U f1 、U f2 The real-time rotor voltage calculation value is:
2. the method of claim 1, further comprising low pass filtering the acquired rotor voltage, rotor positive leakage current, and rotor negative leakage current.
3. The method as claimed in claim 2, wherein the controllable switch switching time is defined as the current time, and the sampling points of the corresponding rotor voltage, rotor positive leakage current and rotor negative leakage current are respectively U f (n)、I p (n)、I n (n)；
The correction calculation is performed based on the rotor voltage, the rotor positive leakage current and the rotor negative leakage current after the low-pass filtering: and calculating the average values of the rotor voltage, the rotor positive leakage current and the rotor negative leakage current in a set time period before the switching of the controllable switch, and correcting.
4. The method of claim 3, wherein the correction calculation is performed according to the following equation:
wherein N is the number of sampling points per cycle, and the point number N-N represents the forward push N/f from the corresponding time of the sampling point N s Sampling point number of time corresponding to duration, f s For the sampling rate, U f0 、I p0 、I n0 For zero drift correction value, U fa 、I pa 、I na And the measurement reference values are respectively the rotor voltage, the rotor positive leakage current and the rotor negative leakage current.
5. A method as claimed in claim 1, characterized in that the rotor voltage measurement reference values are each defined as U in the switched-on state of the switch fa1 、U fa2 In response to:
the locked rotor ground protects the duration of the switching cycle of the at least one controllable switch.
6. The method of claim 1, wherein in response to the rotor ground protection not being latched and the real-time rotor ground resistance calculation being less than the action setting, the rotor ground protection is actuated after such condition persists for the duration of at least one controllable switch switching cycle.
7. A rotor grounding protection device is characterized in that the rotor grounding protection device is realized based on a rotor grounding protection circuit, in the rotor grounding protection circuit, a rotor large shaft is connected with the negative end of a direct current power supply E, the positive end of a rotor is connected with the positive end of the direct current power supply E through at least one resistor R1, the negative end of the rotor is connected with the positive end of the direct current power supply E through at least one resistor R2 and a resistor R3, and two ends of the resistor R2 or the resistor R3 are connected with a controllable switch S in parallel; a voltage measuring unit V1 is connected in parallel to the positive end and the negative end of the rotor, a current measuring unit A1 is arranged on a line connecting the positive end of a direct current power supply E and the positive end of the rotor through a resistor R1, and a current measuring unit A2 is arranged on a line connecting the negative end of the direct current power supply E and the negative end of the rotor through resistors R2 and R3;
the rotor ground protection device includes:
the switch control module is configured to control the on-off state switching of the controllable switch at a set frequency;
the circuit sampling module is configured for sampling the rotor voltage, the rotor positive leakage current and the rotor negative leakage current at a set sampling rate to obtain a real-time sampling value;
the measurement reference value calculation module is configured for correcting and calculating to obtain measurement reference values of the rotor voltage, the rotor positive leakage current and the rotor negative leakage current in corresponding time periods according to the rotor voltage, the rotor positive leakage current and the rotor negative leakage current during the state maintenance period of each controllable switch;
the protection calculation module is configured for solving rotor voltage, rotor grounding resistance and rotor grounding position under two adjacent opening and closing states of the controllable switch by utilizing a rotor grounding protection loop equation under the two states of opening and closing of the controllable switch according to the rotor positive leakage current and the rotor negative leakage current measurement reference value obtained through correction calculation to obtain a real-time grounding resistance, a rotor grounding position and a real-time rotor voltage calculation value;
the voltage comparison module is configured for comparing real-time rotor voltage calculation values under two states of opening and closing adjacent to the controllable switch with rotor voltage measurement reference values in corresponding time periods respectively;
in response to the two states of opening and closing before and after the switching of the controllable switch, the difference value between the real-time rotor voltage calculation value and the rotor voltage measurement reference value at the corresponding moment is larger than a preset threshold value, and the rotor is locked to be in ground protection for the duration of the switching period of at least one controllable switch;
the protection logic judgment module responds to the fact that the rotor grounding protection is not locked and the real-time rotor grounding resistance is smaller than the action setting value, and then the rotor grounding protection acts;
the equations of the rotor ground protection loop under the two adjacent opening and closing states of the controllable switch are as follows:
s is opened:
s is closed:
in the formula, in two states of opening and closing before and after one switch switching, I pa1 、I na1 Respectively measuring reference values of rotor positive leakage current and rotor negative leakage current in the state that the switch S is opened pa2 、I na2 Respectively measuring reference values of rotor positive leakage current and rotor negative leakage current under the closed state of a switch S; r g Representing the rotor ground resistance;
the rotor voltage U in the S-open state f1 S rotor voltage U in closed state f2 Rotor grounding resistance R g Taking the rotor grounding position alpha as an unknown quantity, and carrying out equation solution to obtain real-time rotor grounding resistance R g The position alpha grounded with the rotor is as follows:
rotor voltage U f1 、U f2 The real-time rotor voltage calculation value is:
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| CN112731202B (en) * | 2020-12-03 | 2023-02-14 | 南京国电南自电网自动化有限公司 | Ping-pong rotor ground protection circuit abnormity discrimination method |
| CN112763937A (en) * | 2020-12-03 | 2021-05-07 | 国电南京自动化股份有限公司 | Method for judging abnormality of double-end direct current injection switching type rotor ground protection circuit |
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