A method, device and storage medium for detecting intermittent rotor grounding protection

Abstract

The present invention discloses a method, device and storage medium for detecting intermittent rotor grounding protection. The method includes: collecting rotor voltage U by using a DC single - end injection switching sampling circuit f and rotor leakage current I; processing the collected rotor voltage U f and rotor leakage current I to obtain the rotor voltage U fa (n) and rotor leakage current I a (n) at the current moment; judging whether the rotor has an intermittent grounding start according to the rotor leakage current I a (n). If it is an intermittent grounding start, judge whether warning, tripping or blocking protection is required. The present invention can measure the intermittent grounding fault of the rotor, and judge whether warning or tripping is required through the cumulative discrimination of the over - current of the grounding fault, solves the problem that the conventional rotor grounding protection cannot detect the intermittent grounding fault, expands the application range of the rotor grounding protection, and improves the reliability of the protection.

Description

Technical Field

[0001] The present invention relates to the technical field of generator relay protection, and in particular, to a method, device and storage medium for detecting intermittent rotor grounding protection. Background Art

[0002] Rotor grounding protection is the main protection for the rotor winding of a generator and an important part of generator relay protection. Existing rotor grounding protection is generally used to measure stable rotor grounding faults and usually cannot respond to intermittent rotor grounding faults. Summary of the Invention

[0003] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a method, device and storage medium for detecting intermittent rotor grounding protection, which can detect intermittent and unstable rotor grounding faults and issue an alarm or trip after the intermittence occurs, thereby expanding the application scope of rotor grounding protection.

[0004] To solve the above technical problems, the present invention is implemented by the following solutions:

[0005] The present invention provides a method for detecting intermittent rotor grounding protection, including:

[0006] Collecting rotor voltage U f and rotor leakage current I by using a DC single - end injection switching sampling circuit;

[0007] Processing the collected rotor voltage U f and rotor leakage current I to obtain the rotor voltage U fa (n) and rotor leakage current I a (n) at the current moment;

[0008] Judging whether the rotor is intermittently grounded and started according to the rotor leakage current I a (n). If it is intermittently grounded and started, then judge whether alarm, trip or protection blocking is required.

[0009] The present invention also provides an electronic device, including a memory, a processor and a computer program stored on the memory and executable on the processor. When the processor executes the program, the steps of the above method are implemented.

[0010] The present invention also provides a computer - readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the steps of the above method are implemented.

[0011] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: The present invention can measure the intermittent grounding fault of the rotor. By judging whether to alarm or trip through the cumulative overcurrent of the grounding fault, it solves the problem that the conventional rotor grounding protection cannot detect the intermittent grounding fault, expands the application scope of the rotor grounding protection, and improves the reliability of the protection. Description of the Drawings

[0012] Figure 1 is a diagram of a DC single - end injection switching sampling circuit provided by an embodiment of the present invention; Detailed Embodiments

[0013] The present invention will be further described below with reference to the drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and cannot be used to limit the protection scope of the present invention.

[0014] Embodiment 1:

[0015] This embodiment provides a method for detecting intermittent rotor grounding protection, including the following steps:

[0016] Step 1: Use a DC single - end injection switching sampling circuit to collect the rotor voltage U f and the rotor leakage current I, and process the collected rotor voltage U f and the rotor leakage current I to obtain the rotor voltage U fa (n) and the rotor leakage current I a (n)

[0017] As Figure 1 shown, the DC single - end injection switching sampling circuit includes a DC power supply, a resistor R1, a resistor R2, and an electronic switching switch S. Its structure is that the negative end of the superimposed DC power supply is connected to the rotor shaft, the positive end of the DC power supply is connected to the negative end of the rotor winding in series with the resistor R1 and the resistor R2, and an electronic switching switch S is connected in parallel with one of the resistor R1 and the resistor R2. The resistance values of the resistor R1 and the resistor R2 are the same, preferably 40 kΩ, and the voltage E of the DC power supply is preferably 50 V.

[0018] When the electronic switching switch S alternates between the open and closed states with a period of T (T = 1 s), continuously collect the rotor voltage U f and the rotor leakage current I; filter the rotor voltage U f and the rotor leakage current I (cut - off frequency is 20 Hz) to obtain the rotor voltage sampling point U f (n) and the rotor leakage current sampling point I(n); correct and perform short - window averaging on the rotor voltage sampling point U f (n) and the rotor leakage current sampling point I(n) to obtain the rotor voltage U fa (n) and the rotor leakage current I a(n), and the calculation formula is as follows:

[0019]

[0020] Wherein, 24 represents the number of sampling points within the set time, and the set time is preferably 20 ms. n - 23 + i represents the sampling point number at the previous (23 - i) / fs moment, i ∈ [1, 23], n is the current sampling point number, f s is the sampling rate, preferably 1200 Hz, U f0 is the voltage zero drift correction value, and I0 is the current zero drift correction value.

[0021] Step 2: Determine whether the rotor starts intermittent grounding according to the rotor leakage current I a (n)

[0022] Within the time of 0.6 s to 1 s (0.6T to T) after the electronic switch S is switched, every 0.833 ms (1 / f s ), the stability of the rotor leakage current I a (n) is calculated cyclically, and it is determined whether the rotor leakage current I a (n) is stable. The calculation steps include:

[0023] If the current time exceeds 0.6 s (0.6T) after the electronic switch S is switched, then the current rotor leakage current I a (n) and the rotor leakage current I a (n - 24) 20 ms ago are substituted into the following inequality:

[0024]

[0025] If the inequality holds, it is determined that the rotor leakage current I a is unstable after the current electronic switch S is switched;

[0026] If, in the state of the electronic switch S being continuously opened and closed once, the rotor leakage current I a (n) is unstable at least once, and the number of times that the rotor leakage current I a (n) is greater than the starting threshold of 0.45 mA (obtained by calculation, E is the voltage of the DC power supply, and R is the resistance value of resistor R1 and resistor R2) is greater than 192 (0.16Tf s , 0.16Tf s rounded down), then it is determined that the rotor starts intermittent grounding.

[0027] Step 3: If it is an intermittent grounding start, determine whether to alarm, trip, or block protection

[0028] 1) Block protection

[0029] Define the alarm current accumulation counter cnt1 and the alarm current status flag sequence FlagGj(k), where k represents an integer from 0 to 2400;

[0030] At initialization, both the alarm current accumulation counter cnt1 and the alarm current status flag sequence FlagGj(k) are cleared, and the grounding resistance alarm setting value is assigned as R g1 and the grounding resistance trip setting value is assigned as R g2 ;

[0031] If the rotor voltage is unstable, i.e., it satisfies

[0032] U fa (n) - U fa (n - N) > max{0.2U fa (n), 0.2U fa (n - N), 10}, then block for 5 s.

[0033] 2) Alarm

[0034] If the current time is within the time range of 0.6 s to 1 s (0.6T to T) after the electronic changeover switch S is opened and the rotor leakage current I a (n) is greater than (obtained by calculation, E is the voltage of the DC power supply, and R is the resistance value of resistor R1 and resistor R2) or if the current time is within the time range of 0.6 s to 1 s (0.6T to T) after the electronic changeover switch S is closed and the rotor leakage current I a (n) is greater than (obtained by calculation, E is the voltage of the DC power supply, and R is the resistance value of resistor R1 and resistor R2), then both the alarm current status flag sequence FlagGj(n) and FlagGj(n - 1200) are set to 1, otherwise both are set to 0, FlagGj(n) is the current alarm current status flag sequence, and FlagGj(n - 1200) is the alarm current status flag sequence before 1 s (1200 / f s );

[0035] The value of cnt1 is increased by FlagGj(n) - FlagGj(n - 900), FlagGj(n - 900) represents the alarm current status flag sequence before 0.75 s (900 / f s ), if cnt1 / 900 is greater than the alarm count ratio threshold K set1 = 0.1, and the protection is not blocked, then an intermittent rotor grounding alarm is issued.

[0036] 3) Trip

[0037] Define a tripping current accumulation counter cnt2 and a tripping current status flag sequence FlagTz(k), where k represents an integer from 0 to 2400;

[0038] During initialization, both the tripping current accumulation counter cnt2 and the tripping current status flag sequence FlagTz(k) are cleared, and the grounding resistance alarm setting value is assigned as R g1 and the grounding resistance tripping setting value is assigned as R g2 ;

[0039] If the current time is within the time range of 0.6 s to 1 s (0.6T to T) after the electronic changeover switch S is closed and the rotor leakage current I a (n) is greater than (obtained by calculation, where E is the voltage of the DC power supply and R is the resistance value of resistor R1 and resistor R2) or if the current time is within the time range of 0.6 s to 1 s (0.6T to T) after the electronic changeover switch S is closed and the rotor leakage current I a (n) is greater than (obtained by calculation, where E is the voltage of the DC power supply and R is the resistance value of resistor R1 and resistor R2), then both the tripping current status flag sequence FlagTz(n) and FlagTz(n - 1200) are set to 1, otherwise both are set to 0. FlagTz(n) is the current tripping current status flag sequence, and FlagTz(n - 1200) is the tripping current status flag sequence before 1 s (1200 / f s );

[0040] The value of cnt2 is increased by FlagTz(n) - FlagTz(n - 900). FlagTz(n - 900) represents the tripping current status flag sequence before 0.75 (900 / f s ). If cnt2 / 900 is greater than the tripping count ratio threshold K set2 = 0.2 and the protection is not blocked, then an intermittent rotor ground trip occurs.

[0041] In summary, this method can measure the intermittent rotor ground fault. By accumulating the overcurrent of the ground fault to determine whether to alarm or trip, it solves the problem that the conventional rotor ground protection cannot detect the intermittent ground fault, expands the application range of the rotor ground protection, and improves the reliability of the protection.

[0042] Embodiment 2:

[0043] This embodiment provides an electronic device, including a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the program, it implements the steps of the method in Embodiment 1.

[0044] Embodiment 3:

[0045] This embodiment provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the steps of the method described in Embodiment 1 are implemented.

[0046] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, a system, or a computer program product. Therefore, the present application can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0047] The present application is described with reference to the flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each flow and / or block in the flowchart and / or block diagram can be implemented by computer program instructions, and the combination of flows and / or blocks in the flowchart and / or block diagram can also be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, such that the instructions executed by the processor of the computer or other programmable data processing devices generate a device for implementing the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0048] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, such that the instructions stored in the computer-readable memory generate a manufactured article including an instruction device that implements the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0049] These computer program instructions can also be loaded onto a computer or other programmable data processing device, such that a series of operation steps are executed on the computer or other programmable device to generate a computer-implemented process. Thus, the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0050] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A method for detecting intermittent rotor grounding protection, characterized in that, Comprising: Adopt a DC single - end injection switching sampling circuit to collect the rotor voltage U f and the rotor leakage current I ; The collected rotor voltage U f and the rotor leakage current I are processed to obtain the rotor voltage U fa ( n ) and the rotor leakage current I a ( n ); According to the rotor leakage current I a ( n ) Determine whether the rotor starts with intermittent grounding. If it is an intermittent grounding start, then determine whether alarm, tripping, or protection blocking is required; The DC single - end injection switching sampling circuit includes a DC power supply, a resistor R1, a resistor R2, and an electronic switching switch S; the negative terminal of the superimposed DC power supply is connected to the rotor shaft, and the positive terminal of the DC power supply is connected to the negative terminal of the rotor winding after being connected in series with the resistor R1 and the resistor R2. An electronic switching switch S is connected in parallel with one of the resistor R1 and the resistor R2. The resistance values of the resistor R1 and the resistor R2 are the same. Assuming the resistance value of the resistor R1 is R; According to the rotor leakage current I a ( n ) Determine whether the rotor starts with intermittent grounding, including: Within the time range of 0.6T to T after the electronic switch S switches, every 1 / f s time, the rotor leakage current is calculated cyclically I a ( n ) for its stability level, and to determine whether the rotor leakage current I a ( n ) is stable. T is the period of the electronic switch S; If, in the state where the electronic changeover switch S is turned on and then closed continuously once, the rotor leakage current I a ( n ) is unstable at least once, and the rotor leakage current I a ( n ) is greater than the starting threshold and the number of times is greater than 0.16 Tf s , 0.16 Tf s is rounded down to an integer, and E is the voltage of the DC power supply, then it is determined that the rotor has an intermittent ground start; Within the time period from 0.6T to T after the electronic switch S is switched, the rotor leakage current is calculated cyclically every 1 / f s time I a ( n ) for its stability degree, and to determine whether the rotor leakage current I a ( n ) is stable, including: If the current time exceeds 0.6T during the switching of the electronic switch S, the current rotor leakage current I a ( n ) and the rotor leakage current I a ( n -N) are substituted into the inequality: ； If the inequality holds, it is determined as the rotor leakage current I a After the electronic changeover switch S is switched this time, it is unstable, N is the number of sampling points within the set time.

2. The detection method of intermittent rotor grounding protection according to claim 1, wherein, Collect the rotor voltage using a DC single - end injection switching sampling circuit U f and the rotor leakage current I ; Process the collected rotor voltage U f and the rotor leakage current I to obtain the rotor voltage U fa ( n ) and the rotor leakage current I a ( n ), including: Continuously collect the rotor voltage in two states where the electronic switching switch S alternates between open and closed at a period of T U f and the rotor leakage current I ; The rotor voltage U f and the rotor leakage current I are filtered to obtain the rotor voltage sampling point at the current moment U f ( n ) and the rotor leakage current sampling point I ( n ); The rotor voltage sampling point U f ( n ) and the rotor leakage current sampling point I ( n ) are corrected and short-window averaged to obtain the rotor voltage U fa ( n ) and the rotor leakage current I a ( n ) at the current moment. The calculation formula is as follows: ； In the formula, n - N +1+ i represents the sampling point number at the previous ( N -1- i ) / f s moment, i ∈[1, N - 1], n is the current sampling point number, f s is the sampling rate, U f0 is the voltage zero drift correction value, I 0 is the current zero drift correction value.

3. The method for detecting intermittent rotor grounding protection according to claim 1, wherein If it is an intermittent grounding start, it is determined whether it is necessary to alarm, trip, or block protection, including: Define an alarm current accumulation counter cnt1 and an alarm current status flag sequence FlagGj(k), where k represents an integer from 0 to 2400; During initialization, the alarm current accumulation counter cnt1 and the alarm current status flag sequence FlagGj(k) are both cleared, and the ground resistance alarm setting value is assigned as R g1 and the ground resistance trip setting value is R g2 ; If the rotor voltage meets , the protection will be blocked for a certain period of time.

4. The method for detecting intermittent rotor grounding protection according to claim 3, wherein If it is an intermittent grounding start, it is determined whether it is necessary to alarm, trip, or block protection, and it also includes: If the current time is within the time range of 0.6T to T after the electronic switch S is turned on and the rotor leakage current I a (n) is greater than , or if the current time is within the time range of 0.6T to T after the electronic switch S is closed and the rotor leakage current I a (n) is greater than , then both the alarm current status flag sequence FlagGj(n) and FlagGj(n - 1200) are set to 1, otherwise both are set to 0. FlagGj(n) is the current alarm current status flag sequence, and FlagGj(n - 1200) is the alarm current status flag sequence before 1200 / f s ; The value of cnt1 is incremented by FlagGj(n) - FlagGj(n - 900), where FlagGj(n - 900) represents 900 / f s The previous alarm current status flag sequence. If cnt1 / 900 is greater than the alarm count ratio threshold K set1 and the protection is not blocked, an intermittent rotor ground alarm is issued.

5. The method for detecting intermittent rotor ground protection according to claim 1, wherein If it is an intermittent grounding start, it is determined whether it is necessary to alarm, trip, or block protection, and it also includes: Define a trip current accumulation counter cnt2 and a trip current status flag sequence FlagTz(k), where k represents an integer from 0 to 2400; At initialization, both the tripping current accumulation counter cnt2 and the tripping current status flag sequence FlagTz(k) are cleared, and the grounding resistance alarm setting value is assigned as R g1 and the grounding resistance tripping setting value is R g2 ; If the current time is within the time range of 0.6T to T after the electronic switching switch S is closed and the rotor leakage current I a (n) is greater than , or if the current time is within the time range of 0.6T to T after the electronic switching switch S is closed and the rotor leakage current I a (n) is greater than , then both the trip current status flag sequence FlagTz(n) and FlagTz(n - 1200) are set to 1, otherwise both are set to 0. FlagTz(n) is the current trip current status flag sequence, and FlagTz(n - 1200) is the trip current status flag sequence before 1200 / f s ; The value of cnt2 is incremented by FlagTz(n)-FlagTz(n - 900), where FlagTz(n - 900) represents 900 / f s The previous trip current status flag sequence. If cnt2 / 900 is greater than the trip count ratio threshold K set2 and the protection is not blocked, then an intermittent rotor ground fault trip occurs.

6. An electronic device, comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the steps of the method described in any one of claims 1 to 5.

7. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the steps of the method described in any one of claims 1 to 5.

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