Transformer residual magnetism calculation method and device and computer program

Abstract

The invention discloses a transformer residual magnetism calculation method and device and a computer program, and the method comprises the steps: monitoring an opening starting input signal inputted from the outside of a transformer in real time, and recording a moment when the opening starting input signal is changed from a low level to a high level as a first moment; recording a moment when the voltage reaches a voltage stable point after opening as a second moment; calculating a first magnetic flux value by using voltage integration in first n complete cycles at a first moment, and then calculating a second magnetic flux value corresponding to a voltage stable point by taking the first moment as an integration lower limit and a second moment as an integration upper limit; and calculating a difference value between the second magnetic flux value and the first magnetic flux value, namely the residual magnetism. According to the scheme of the invention, the calculation precision of the residual magnetism of the iron core after the transformer is opened can be improved, and the method has a positive influence on the subsequent excitation inrush current suppression of the transformer.

Description

Technical Field

[0001] The present invention belongs to the technical field of power equipment protection, is applied to transformer excitation inrush current suppression, and specifically relates to a transformer residual magnetism calculation method, device and computer program. Background Art

[0002] During the random closing process of an unloaded transformer, an excitation surge current several times higher than the rated current will be generated. This electromagnetic transient phenomenon will endanger the safe and stable operation of the power system. The phase selection and switching technology selects the best closing phase to input the transformer according to the residual magnetism value after the opening of the switch, so that the magnetic flux does not mutate suddenly, which can fundamentally suppress the excitation surge current.

[0003] The voltage integration method is commonly used in the existing residual magnetism estimation methods. The accuracy of the voltage integration method depends on the accurate selection of the integration interval. The existing residual magnetism calculation methods based on the voltage integration method all use the peak value of the voltage waveform before the switch-off as the integration starting point. For example, CN111929626A discloses a transformer residual magnetism estimation device and method, with the moment when the effective value of the three-phase voltage is less than the set value as the upper limit; the lower limit and upper limit of the integration are the starting point and end point of the integration, and the voltage is integrated and calculated using the trapezoidal integration method to obtain the magnetic flux. In this method, the peak value of the voltage waveform before the switch-off is used as the integration starting point, and the end point of the integration is the moment when the effective value of the voltage is less than the set value. The premise for calculating the magnetic flux is that the peak voltage point before the switch-off must be found, and the end point of the integration depends on the size of the set value. If the set value is too large or too small, it may lead to inaccurate integration end point, resulting in deviation in the flux calculation, affecting the accuracy of the calculation result. Summary of the invention

[0004] The first purpose of the present invention is to overcome the defects of the above-mentioned prior art and provide a simple and accurate transformer residual magnetism calculation method, which can accurately locate the voltage integration interval, eliminate the influence of the flux deviation value, improve the residual magnetism measurement accuracy, and help improve the accuracy of calculating the circuit breaker opening angle, which has a positive effect on suppressing the main transformer excitation inrush current.

[0005] To achieve the above object, the present invention adopts the following technical solution:

[0006] A transformer residual magnetism calculation method, comprising:

[0007] Real-time monitoring of the opening start input signal of the transformer external input, and recording the moment when the opening start input signal changes from a low level to a high level as the first moment;

[0008] The moment when the voltage reaches the voltage stabilization point after the switch is opened is recorded as the second moment;

[0009] Take the first n complete cycles of the first moment and calculate the first magnetic flux value by voltage integration, then use the first moment as the lower limit of integration and the second moment as the upper limit of integration to calculate the second magnetic flux value corresponding to the voltage stabilization point;

[0010] The difference between the second magnetic flux value and the first magnetic flux value, ie, the residual magnetism, is calculated.

[0011] As a preferred implementation, the three-phase voltage real-time value and the three-phase voltage value used to calculate the voltage integral are derived from the three-phase voltage sampling value on the low-voltage side of the main transformer; the voltage transformer on the low-voltage side is an electromagnetic voltage transformer.

[0012] As a preferred implementation, the opening time is determined based on the real-time value of the three-phase voltage, and when the real-time values ​​of the three-phase voltage are all less than the preset threshold, the circuit breaker is determined to be opened. Since the effective value of the voltage is calculated based on the real-time value, there is a delay in using the effective value of the voltage to determine the opening, and there is no delay problem when using the real-time value, and the calculation amount of the program is reduced.

[0013] As a preferred implementation, the preset threshold is the maximum value of the zero-drift value of the three-phase voltage sampling values ​​after the switch is opened.

[0014] As a preferred implementation, the half-wave peak point before the gate opening is fitted using the least square method to determine the voltage stabilization point after the gate opening.

[0015] As a preferred implementation, the value of n is 1-3.

[0016] A second object of the present invention is to provide a transformer residual magnetism calculation device, comprising:

[0017] The voltage acquisition and cache module collects the three-phase voltage value sampling data of the low-voltage side of the main transformer in real time and stores it in the cache;

[0018] The input quantity monitoring module monitors the high and low level changes of the opening start input signal of the transformer external input in real time;

[0019] The voltage integration interval calculation module is used to determine the starting point and end point of the voltage integration, including: recording the moment when the switch-off start input signal changes from a low level to a high level as the first moment; recording the moment when the voltage reaches the voltage stabilization point after the switch-off as the second moment;

[0020] The transformer flux calculation module calculates the residual magnetism of the core after the three-phase opening according to the cached three-phase voltage sampling value data, including: taking the first n complete cycles at the first moment and using voltage integration to calculate the first flux value, then taking the first moment as the lower limit of the integration and the second moment as the upper limit of the integration, calculating the second flux value corresponding to the voltage stabilization point; calculating the difference between the second flux value and the first flux value, that is, the residual magnetism.

[0021] As a preferred implementation, the cached three-phase voltage sampling value data time window is T seconds; the T satisfies: covering the time required for the transformer voltage drop process after the switch is opened.

[0022] A third object of the present invention is to provide a computer-readable storage medium having a computer program / instruction stored thereon, which implements the steps of the above method when the computer program / instruction is executed by a processor.

[0023] A fourth object of the present invention is to provide a computer program product, comprising a computer program / instruction, which implements the steps of the above method when executed by a processor.

[0024] The present invention has the following beneficial effects:

[0025] (1) The present invention does not need to find the voltage peak as the starting point of the integration, but takes the moment when the opening switch is started and turned into the change position (low level to high level) as the starting point, which is simpler in implementation; and the present invention uses one integration to calculate the magnetic flux (defined as the magnetic flux bias in this application) existing before the starting point, and uses the difference between the two integrations to calculate the residual magnetism, thereby eliminating the influence of the magnetic flux bias and making the calculation result closer to the true value;

[0026] (2) The present invention uses the time corresponding to the voltage stabilization point as the integral end point (upper limit) of the second integral. Compared with the integral end point determined by the set value, the calculated residual magnetism is more accurate.

[0027] (3) The solution of the present invention can realize the accurate calculation of residual magnetism and polarity after the transformer is opened, so as to calculate a more accurate opening angle, which can limit the magnitude of the excitation inrush current when the transformer is air-dropped to the greatest extent. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the relationship between the main functional modules of the transformer residual magnetism calculation device provided by the present invention.

[0029] Figure 2 It is a schematic diagram of a transformer residual magnetism calculation method / program flow provided by the present invention.

[0030] Figure 3 It is a schematic diagram of the voltage integration interval timing and voltage waveform fitting principle provided by the present invention. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described below in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0032] Example 1

[0033] This embodiment provides a transformer residual magnetism calculation device, such as Figure 1 As shown, the device mainly includes: a binary input monitoring module, a voltage acquisition and buffering module, a voltage integral interval calculation module and a transformer residual magnetism calculation module.

[0034] Among them, the input quantity monitoring module monitors the high and low level changes of the opening start signal and uses it as the input of the voltage integration interval calculation module. The voltage acquisition and cache module acquires the voltage waveform on the low-voltage side of the transformer and uses it as the input of the voltage integration interval calculation module. After the voltage integration interval calculation module calculates the upper and lower limits of the voltage integration, it is output to the transformer residual magnetism calculation module to obtain the final three-phase residual magnetism.

[0035] Specifically, the voltage integral interval calculation module records the moment when the switch-off start input signal changes from a low level to a high level as the first moment ( ); record the moment when the voltage reaches the voltage stable point after the gate is opened as the second moment ( );

[0036] The transformer flux calculation module calculates the residual magnetism of the core after the three-phase disconnection according to the cached three-phase voltage sampling value data, including: The first magnetic flux value is calculated by voltage integration based on the first n complete cycles (values ​​1 to 3) of , then as described is the lower limit of the integral, Integral upper limit, calculate the second magnetic flux value corresponding to the voltage stability point ; Calculate the second magnetic flux value and the first magnetic flux value The difference between ,Right now .

[0037] In this embodiment, the cache time window of the voltage acquisition and cache module is 5 seconds.

[0038] Example 2

[0039] like Figure 2 As shown, the present invention also provides a transformer residual magnetism calculation method, comprising the following steps:

[0040] (1) Real-time acquisition and caching of three-phase voltage sampling value data on the low-voltage side of the main transformer with a 5s time window , , , real-time monitoring of the external input of the opening start signal, when the real-time monitoring of the external input of the opening start signal changes from low level to high level, record the current time as ;

[0041] (2) If the three-phase voltage sampling value data collected in real time , , At the same time, if the value is less than the threshold, the circuit breaker is judged to be opened; the threshold is the maximum value of the zero drift value of the three-phase voltage sampling value after opening, which can be determined in advance by experiment.

[0042] (3) According to the cached three-phase voltage sampling value data, obtain The magnetic flux is calculated by integrating the voltage for the three complete cycles before the moment ;Right now: ;

[0043] in, The three-phase voltage sampling value data of the main transformer low-voltage side , , , for The time corresponding to 3 complete cycles before the moment.

[0044] (4) Use the least squares method to fit the half-wave peak point before the opening moment determined in step (2) to determine the voltage stability point after the opening moment, and record the time corresponding to this point. , using voltage integration, The time is the lower limit of the integral. The moment is the upper limit of integration, and the magnetic flux at the voltage stability point after the gate is opened is obtained. ;

[0045] (5) Residual magnetic flux is equal to the value obtained in step (4) And the value obtained in step (3) difference.

[0046] like Figure 3 As shown, the present invention provides a method for obtaining a voltage integral interval, comprising the following steps: when the real-time monitored external input switch start input signal changes from a low level to a high level, the current moment is recorded as ,remember The first three complete cycles of the time correspond to the time , to The interval is the magnetic flux The integral interval is: take the absolute value of the cached voltage waveform data, extract the half-wave peak value of the voltage absolute value waveform after the fitting start time (the fitting start time is the voltage peak point before the opening time), and use the least squares method to fit the extracted half-wave peak point, thereby determining the time corresponding to the voltage stable point. , to The interval is the voltage stable point and the magnetic flux The integral interval of the residual flux .

[0047] Furthermore, this embodiment also provides a computer-readable storage medium, on which a computer program / instruction is stored, and the steps of the above method are implemented when the computer program / instruction is executed by a processor.

[0048] Furthermore, this embodiment also provides a computer program product, which includes a computer program / instructions, and the computer program / instructions implement the steps of the above method when executed by a processor.

[0049] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A transformer residual magnetism calculation method, characterized in that: include: Real-time monitoring of the opening start input signal of the transformer external input, and recording the moment when the opening start input signal changes from a low level to a high level as the first moment; The moment when the voltage reaches the voltage stabilization point after the switch is opened is recorded as the second moment; Take the first moment before n A first magnetic flux value is calculated by voltage integration for a complete cycle, and then a second magnetic flux value corresponding to the voltage stabilization point is calculated with the first moment as the lower limit of integration and the second moment as the upper limit of integration; The difference between the second magnetic flux value and the first magnetic flux value, ie, the residual magnetism, is calculated.

2. The method according to claim 1, characterized in that The three-phase voltage real-time value and the three-phase voltage value used to calculate the voltage integral are derived from the three-phase voltage sampling value on the low-voltage side of the main transformer; the voltage transformer on the low-voltage side is an electromagnetic voltage transformer.

3. According to the method of claim 1, the time of opening the circuit breaker is determined based on the real-time values ​​of the three-phase voltages, and when the real-time values ​​of the three-phase voltages are all less than a preset threshold, it is determined that the circuit breaker is opened.

4. The method according to claim 3, characterized in that The preset threshold is the maximum value of the zero drift value of the three-phase voltage sampling value after the switch is opened.

5. The method according to claim 1, characterized in that The half-wave peak point before the opening of the gate is fitted using the least squares method to determine the voltage stability point after the opening of the gate.

6. The method according to claim 1, characterized in that Said n The value range is 1-3.

7. A transformer residual magnetism calculation device, characterized in that: include: The voltage acquisition and cache module collects the three-phase voltage value sampling data of the low-voltage side of the main transformer in real time and stores it in the cache; The input quantity monitoring module monitors the high and low level changes of the opening start input signal of the transformer external input in real time; The voltage integration interval calculation module is used to determine the starting point and end point of the voltage integration, including: recording the moment when the switch-off start input signal changes from a low level to a high level as the first moment; recording the moment when the voltage reaches the voltage stabilization point after the switch-off as the second moment; The transformer flux calculation module calculates the residual magnetism of the core after the three-phase disconnection according to the cached three-phase voltage sampling value data, including: taking the first moment before n A first magnetic flux value is calculated using voltage integration for a complete cycle, and then a second magnetic flux value corresponding to a voltage stabilization point is calculated using the first moment as the lower limit of integration and the second moment as the upper limit of integration; and a difference between the second magnetic flux value and the first magnetic flux value, i.e., the residual magnetism, is calculated.

8. The device according to claim 7, characterized in that The cached three-phase voltage sampling value data time window is T seconds; T satisfies: covering the time required for the transformer voltage drop process after the switch is opened.

9. A computer-readable storage medium having a computer program / instruction stored thereon, characterized in that: When the computer program / instructions are executed by a processor, the steps of the method described in any one of claims 1 to 6 are implemented.

10. A computer program product comprising a computer program / instructions, characterized in that When the computer program / instructions are executed by a processor, the steps of the method described in any one of claims 1 to 6 are implemented.

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