Substation power supply residual current monitoring device and method

Abstract

The invention discloses a power supply residual current monitoring device and method for a transformer substation, and the device comprises a controller, and a line selection controller, a direct current generator and an alarm which are controlled by the controller. Controlling the direct current generator to emit a direct current detection signal, detecting whether a residual current fault loop is generated or not based on the direct current detection signal, and when the residual current fault loop is detected, obtaining direct current signal current of each branch in the circuit to be detected, which is detected by the line selection controller, and generating a trigger signal matched with the alarm based on the initial direct current and the direct current signal current. According to the substation power supply residual current monitoring device and method provided by the embodiment of the invention, the fault loop can be quickly positioned without power failure, so that the safe operation of the substation power supply is ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of power fault processing, and in particular to a power supply residual current monitoring device and method for a transformer substation. Background Art

[0002] With the increase of voltage level, capacity and area of ​​substation, insulation monitoring of AC power supply in substation has become one of the means to ensure safe operation.

[0003] However, in the residual current monitoring method of the low-voltage AC power supply used in substations, traditional maintenance methods such as bridge testing and insulation testing are all carried out under power outage conditions. The fault location is inaccurate during power outage monitoring, resulting in frequent power outage accidents.

[0004] It can be seen that how to achieve accurate fault location has become a technical problem that needs to be solved urgently by those skilled in the art. Summary of the invention

[0005] The present invention provides a substation power supply residual current monitoring device and method, so as to solve the technical problem of inaccurate fault location during power outage monitoring, and achieve the effect of residual current online monitoring.

[0006] In order to solve the above technical problems, an embodiment of the present invention provides a substation power supply residual current monitoring device, including a controller and a line selection controller controlled by the controller, a DC current generator and an alarm;

[0007] The line selection controller is connected to the DC current generator, and the line selection controller is also connected to the alarm, and the current output end of the DC current generator is connected to the neutral point of the transformer;

[0008] The controller is configured to:

[0009] After detecting the initial DC current detected by the line selection controller, controlling the DC current generator to send a DC detection signal, and detecting whether a residual current fault loop is generated based on the DC detection signal;

[0010] When the residual current fault loop is detected, obtaining the DC signal current of each branch in the circuit to be tested detected by the line selection controller;

[0011] Based on the initial DC current and the DC signal current, a trigger signal matching the alarm is generated.

[0012] As one of the preferred solutions, the substation power supply residual current monitoring device also includes a residual current transformer, and the residual current transformer is installed on the branch line.

[0013] As one of the preferred solutions, the residual current transformer includes an iron core, a coil and a housing, the coil is wound around the iron core, and the iron core and the coil are located inside the housing.

[0014] As one of the preferred solutions, the DC current generator includes a rectifying and transforming circuit, a rectifying circuit, a filtering circuit and a voltage stabilizing circuit;

[0015] The rectifying and transforming circuit is connected to the rectifying circuit, the rectifying circuit is connected to the filtering circuit, and the filtering circuit is connected to the voltage stabilizing circuit.

[0016] As one of the preferred solutions, the line selection controller includes a voltage conversion unit, a signal circuit and a microcontroller, and the voltage conversion unit is connected to the microcontroller through the signal circuit.

[0017] As one of the preferred solutions, the alarm includes an alarm controller and an alarm unit, and the alarm controller is connected to the alarm unit.

[0018] As one of the preferred solutions, the alarm includes a buzzer, an LED indicator light and a remote communication interaction interface, and the remote communication interaction interface is communicatively connected to the user operation and maintenance terminal.

[0019] As one of the preferred solutions, the DC detection signal is a detection current signal not less than 30 milliamperes.

[0020] As one of the preferred solutions, the line selection controller collects the current of the neutral point of the transformer and uses the neutral point current as the initial DC current.

[0021] Another embodiment of the present invention provides a method for monitoring the residual current of the substation station service power supply, which is characterized in that it is applied to the substation station service power supply residual current monitoring device as described in any one of the above.

[0022] Compared with the prior art, the beneficial effects of the embodiments of the present invention are at least one of the following:

[0023] (1) When an insulation problem occurs, the line selection controller collects the current of the neutral point of the transformer and uses the neutral point current as the initial DC current. The line selection controller detects the DC signal current of each branch in the circuit to be tested. When the DC signal current is greater than the initial DC current, the device can quickly locate the fault circuit without power outage, thus ensuring the safe operation of the station service power supply;

[0024] (2) The device can effectively monitor the insulation status of the substation station service power supply and effectively monitor and alarm the leakage of the substation AC power supply due to insulation problems. Brief Description of the Drawings

[0025] Figure 1 is a schematic structural diagram of a residual current monitoring device for the substation service power supply in one embodiment of the present invention;

[0026] Reference Numerals:

[0027] Among them, 1, line selection controller; 2, DC current generator; 3, alarm; A, transformer; B, branch. Detailed Embodiments

[0028] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. The purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the scope of protection of the present invention.

[0029] In the description of the present application, the terms "first", "second", "third", etc. are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, the features defined with "first", "second", "third", etc. may explicitly or implicitly include one or more of such features. In the description of the present application, unless otherwise stated, the meaning of "a plurality" is two or more.

[0030] In the description of the present application, it should be noted that unless otherwise clearly defined and limited, the terms "installed", "connected", "connected" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected, or indirectly connected through an intermediate medium, and it may be the communication inside two elements. The terms "vertical", "horizontal", "left", "right", "up", "down" and similar expressions used herein are only for the purpose of illustration and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be understood as a limitation of the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0031] In the description of the present application, it should be noted that unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those skilled in the art to which this technology belongs. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0032] An embodiment of the present invention provides a monitoring device for the residual current of the substation station service power supply. Specifically, please refer to Figure 1 , Figure 1 which shows a schematic structural diagram of the monitoring device for the residual current of the substation station service power supply in one of the embodiments of the present invention, including a controller, a line selection controller controlled by the controller, a DC current generator, and an alarm. The line selection controller is connected to the DC current generator, and the line selection controller is also connected to the alarm. The current output terminal of the DC current generator is connected to the neutral point of the transformer.

[0033] After detecting the initial DC current detected by the line selection controller 1, control the DC current generator 2 to send out a DC detection signal, and detect whether a residual current fault loop is generated based on the DC detection signal; when detecting a residual current fault loop, obtain the DC signal currents of each branch in the circuit to be measured detected by the line selection controller 1; generate a trigger signal matching the alarm 3 based on the initial DC current and the DC signal current.

[0034] The line selection controller 1 collects the current of the neutral point of transformer A. When the neutral point current reaches a certain current value, it can be considered that the residual current is generated. The first current value can be used as a fixed value, that is, the initial DC current.

[0035] Specifically, the line selection controller 1 includes a voltage conversion unit, a signal circuit, and a microcontroller. The voltage conversion unit is connected to the microcontroller through the signal circuit.

[0036] The monitoring device for the residual current of the substation station service power supply further includes a residual current transformer. The residual current transformer is installed on the branch. There is a residual current transformer installed on each branch. If there is a signal for monitoring the residual current on the branch, the controller can automatically determine it as an insulation fault loop.

[0037] Specifically, the structure of the residual current transformer includes an iron core, a coil, and a housing. The coil is wound around the iron core, and the iron core and the coil are located inside the housing.

[0038] After the line selection controller 1 obtains the initial DC current, the controller controls the DC current generator 2 to emit a DC detection signal, which is a detection current signal not less than 30 mA. Based on the DC detection signal, it is detected whether a residual current fault loop is generated. Specifically, the DC current generator 2 includes a rectifier transformer circuit, a rectifier circuit, a filter circuit, and a voltage stabilizing circuit. The rectifier transformer circuit is connected to the rectifier circuit, the rectifier circuit is connected to the filter circuit, and the filter circuit is connected to the voltage stabilizing circuit.

[0039] One end of the DC current generator 2 is connected to the circuit to be measured. When an insulation fault occurs, the loop is equivalent to generating a fault resistance to the ground. The DC detection signal emitted by the DC current generator 2 will flow through the ground resistance of the insulation fault point through the power supply loop, return to the DC current generator 2 from the ground, and form a loop. The residual current transformer installed on the branch can measure the residual current signal.

[0040] The alarm 3 includes an alarm controller and an alarm unit. The alarm controller is connected to the alarm unit. The alarm includes a buzzer and an LED indicator. The alarm also includes a remote communication interface, and the remote communication interface is communicatively connected to the user operation and maintenance terminal.

[0041] After the DC signal is injected into all the power-consuming branches of the power supply, when there is an insulation fault, this DC current signal will form a current loop through the power supply loop and the insulation fault point. The residual current generated on each branch should be detected by the residual current sensor. If the residual current is detected on multiple branches, it means that there are fault points on multiple branches. The sum of the residual currents monitored by each loop should be consistent with the residual current monitored at the neutral point of transformer A, indicating that there is only one insulation fault. The residual current monitored at the neutral point of transformer A is greater than the total residual current of all loops, indicating that there are other insulation faults, indicating that there are multiple fault points.

[0042] The present invention also provides an embodiment for effectively distinguishing the leakage current signal generated by the residual current from the load current or other frequency interference signal sources.

[0043] Specifically, the calculation of the residual current uses the Kirchhoff's law formula. In the three-phase four-wire substation station service power supply system, the phase currents are expressed as:

[0044] I A +I B +I C -I N -I d =0

[0045] Where I A 、I B 、I C are phase currents, and I Nis the neutral line current, I d is the residual current.

[0046] The residual current is affected by the load current, and the required characteristic signal needs to be obtained through the Fourier transform algorithm. When processing the current signal, the Fourier transform can convert the time-domain signal into a frequency-domain signal, which is convenient for analyzing the frequency components of the current signal. In residual current monitoring, the Fourier transform can be used to extract specific frequency components (such as fundamental current) in the current signal, thereby improving the accuracy and stability of the monitoring. The signal spectrum is established for the N sampled data through the decimation-in-time Fourier transform, and the amplitude of each frequency point is further calculated.

[0047] That is to say, the current on the residual current transformer needs to be collected in terms of frequency. The current passes through the signal processing circuit and only samples the signal sent by the device host. The leakage current signal collected by the residual current transformer each time is used to collect the current data for a period of time, denoted as

[0048] X N = 0, 1, 2, 3,......, N - 1

[0049] where X N represents the current collected N times.

[0050] A DC current generator is used to process the collected data, and the residual current signal is denoised through the filter circuit to remove the clutter in the signal.

[0051] The current sampled N times is weighted and calculated according to the following formula to obtain the signal value filtering out the DC leakage current component.

[0052]

[0053] where X ′ n is the DC leakage current signal value generated by the calculated filtered signal source, X n is the current signal value collected N times, X m is the value taken at any point in the N samplings from 0 to N - 1, that is, any value in the signal value, and m is any point in the N points.

[0054] The DC current generator can effectively isolate the signal value of the filtered DC component from the signal of the AC power supply.

[0055] The decimation-in-time (DIT) method is used to extract each measured point, and the discrete signals extracted from each point are subjected to Fourier transform to extract the time-domain region signal, perform time-domain region calculation, and convert the time-domain data into frequency-domain data. The calculation formula is as follows:

[0056]

[0057] Where X k is the frequency-domain data corresponding to the acquired signal; j is the index of each time point representing the sampling points in the original signal; k is the different frequency components in the entire measurement frequency domain, represents the conversion value used for the j-th sampling point in the original time-domain signal to achieve the conversion from the time domain to the frequency domain.

[0058] For the residual current signal generated due to insulation faults, directly collect the time points of the leakage current signal. Within the range where the frequency is the same as that of the DC signal source and the generated time signal is similar, set a different frequency range [f1, f2] within different time periods according to actual situations. Set a threshold W, and the formula for filtering and extracting all signals within a specific time and frequency range is as follows:

[0059]

[0060] Where f s is the sampling frequency. By calculation, all signals at a specific frequency within a specific time method are obtained. Y k is the value of the k-th frequency component in the entire frequency domain, and it is the signal obtained after converting back to the time domain. It represents the leakage current signal in the time domain generated by the residual current detected by the residual current transformer.

[0061] Perform inverse Fourier transform on all signals within the filtered and extracted frequency range, and extract the frequency-domain data and convert it back to time-domain data. The formula is as follows:

[0062]

[0063] Where Y n is the leakage current signal generated by the residual current detected by the residual current transformer, represents the inverse transformation form of the complex unit root and is used to achieve the conversion from the frequency domain to the time domain.

[0064] Through the above steps, the leakage current signal generated by the residual current is effectively distinguished from the load current or interference signal sources of other frequencies.

[0065] Another embodiment of the present invention provides a method for monitoring the residual current of a substation service power supply, which is applied to the residual current monitoring device for the substation service power supply as described above.

[0066] Compared with the prior art, the beneficial effects of the embodiments of the present invention are at least one of the following:

[0067] (1) When an insulation problem occurs, the line selection controller collects the current of the neutral point of the transformer, uses the neutral point current as the initial DC current, and the line selection controller detects the DC signal current of each branch in the circuit to be measured. When the DC signal current is greater than the initial DC current, the device can quickly locate the faulty circuit without power outage, thus ensuring the safe operation of the station power supply;

[0068] (2) The device can effectively monitor the insulation status of the station power supply of the substation and effectively monitor and alarm the leakage of the AC power supply of the substation due to insulation problems.

[0069] The above embodiments only represent several implementation manners of the present invention, and the description thereof is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several deformations and improvements can be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the invention patent shall be subject to the appended claims.

Claims

1. A residual current monitoring device for power supply of a substation, characterized in that: It includes a controller and a line selection controller, a DC current generator and an alarm controlled by the controller; The line selection controller is connected to the DC current generator, and the line selection controller is also connected to the alarm, and the current output end of the DC current generator is connected to the neutral point of the transformer; The controller is configured to: After detecting the initial DC current detected by the line selection controller, controlling the DC current generator to send a DC detection signal, and detecting whether a residual current fault loop is generated based on the DC detection signal; When the residual current fault loop is detected, obtaining the DC signal current of each branch in the circuit to be tested detected by the line selection controller; Based on the initial DC current and the DC signal current, a trigger signal matching the alarm is generated.

2. The residual current monitoring device for power supply of a substation according to claim 1, characterized in that: The substation power supply residual current monitoring device further comprises a residual current transformer, and the residual current transformer is installed on the branch line.

3. The residual current monitoring device for power supply of a substation as claimed in claim 2, characterized in that: The residual current transformer comprises an iron core, a coil and a shell. The coil is wound on the iron core. The iron core and the coil are located inside the shell.

4. The residual current monitoring device for power supply of a substation according to claim 1, characterized in that: The DC current generator includes a rectifier and transformer circuit, a rectifier circuit, a filter circuit and a voltage stabilizing circuit; The rectifying and transforming circuit is connected to the rectifying circuit, the rectifying circuit is connected to the filtering circuit, and the filtering circuit is connected to the voltage stabilizing circuit.

5. The residual current monitoring device for power supply of a substation according to claim 1, characterized in that: The line selection controller includes a voltage conversion unit, a signal circuit and a microcontroller, and the voltage conversion unit is connected to the microcontroller through the signal circuit.

6. The residual current monitoring device for power supply of a substation according to claim 1, characterized in that: The alarm device comprises an alarm controller and an alarm unit, and the alarm controller is connected to the alarm unit.

7. The residual current monitoring device for power supply of a substation according to claim 6, characterized in that: The alarm includes a buzzer, an LED indicator light and a remote communication interaction interface, and the remote communication interaction interface is communicatively connected to a user operation and maintenance terminal.

8. The residual current monitoring device for power supply of a substation according to claim 1, characterized in that: The DC detection signal is a detection current signal of not less than 30 milliamperes.

9. The residual current monitoring device for power supply of a substation according to claim 1, characterized in that: The line selection controller collects the current of the neutral point of the transformer and uses the neutral point current as the initial DC current.

10. A method for monitoring residual current of a power supply for a substation, characterized in that: Applicable to the residual current monitoring device for power supply of a substation as described in any one of claims 1 to 9.

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