Transformer substation capacitive equipment dielectric loss monitoring method based on synchronizing signal
By adopting a relative dielectric loss monitoring method based on synchronization signals in the dielectric loss monitoring of capacitive equipment, and using capacitive equipment under the same phase as the phase reference source, the problems of data disturbance and insufficient accuracy in the traditional method are solved, and higher monitoring accuracy and stability are achieved.
Patent Information
- Application Number
- CN202311239367.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-09-25
- Publication Date
- 2025-03-25
AI Technical Summary
Traditional capacitive equipment media loss monitoring methods have problems of data disturbance and insufficient accuracy, especially in field applications, where detection accuracy and stability are obviously insufficient.
The relative dielectric loss monitoring method of substation complete station capacitive equipment based on synchronization signals is adopted. By using all capacitive equipment under the same phase as mutual phase reference sources, the data disturbance problem introduced by the voltage transformer is solved and the data stability is improved.
It improves the accuracy and stability of the dielectric loss monitoring of capacitive equipment, reduces the fluctuation of the dielectric loss value, enhances the credibility of the monitoring results, and meets the national standards for the monitoring accuracy of capacitive equipment.
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Figure CN119689094A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of dielectric loss monitoring of capacitive equipment, and in particular is a method for realizing stable measurement of dielectric loss value of capacitive equipment. Background Art
[0002] The online monitoring method of capacitive equipment has been proposed for many years, and there are many types of online monitoring equipment in operation. Most online monitoring equipment always has good accuracy in offline measurement tests, but after being applied to the field, the detection accuracy and stability are obviously insufficient. From the perspective of electromagnetic interference, the online monitoring equipment has made a metal shielding shell and used a shielded signal line, but the problem has not been eliminated. According to the dielectric loss measurement method, the dielectric loss value is mainly measured by the voltage phase of the system and the current phase of the end screen of the capacitive equipment. The dielectric loss angle can be obtained through the phase angle difference, and then the online dielectric loss can be detected. However, the voltage signal of the online dielectric loss is mostly taken from the voltage transformer. The voltage transformer has high accuracy in measuring steady-state voltage and phase, but the voltage signal output in the transient process has a certain phase lag with the actual position of the system voltage. For dielectric loss monitoring, a small angle fluctuation causes a large dielectric loss deviation, so the traditional method of taking the reference signal from the voltage transformer always has disturbances.
[0003] In view of this problem, in the prior art, the relative dielectric loss value of the capacitive device is calculated by adding the tangent value of the original dielectric loss angle to the tangent value of the change angle. Although this calculation method has the advantage of relative dielectric loss, the use of the tangent function in advance during the calculation process affects the error. Moreover, this relative value calculation is the result of comparison with each capacitive device, and does not take into account the error introduced by the voltage phase difference problem caused by the unbalanced load between different phases, which easily leads to fluctuations in the relative dielectric loss measurement results. Summary of the invention
[0004] The present invention takes the source of error into consideration and proposes a method for monitoring the relative dielectric loss of capacitive equipment in the entire substation based on synchronous signals. Based on all capacitive equipment under the same phase as a mutual phase reference source, it solves the data disturbance problem introduced by the voltage transformer and improves the stability of the data. The dielectric loss monitoring of capacitive equipment is a technical indicator used to characterize the degree of insulation aging of capacitor equipment. This indicator can accurately measure the dielectric loss value of the capacitive equipment under offline conditions through the Xilin bridge test. Generally, when the dielectric loss value of the capacitive equipment reaches a certain warning value set by the operating unit, the capacitive equipment needs to be repaired. Avoid causing larger accidents to the defective equipment during operation, affecting the reliability of power supply.
[0005] The technical solution adopted by the present invention to achieve the above-mentioned purpose is: a method for monitoring dielectric loss of capacitive equipment in a substation based on synchronous signals, comprising the following steps:
[0006] Set the factory dielectric loss value of capacitive devices
[0007] Sending synchronous acquisition instructions to the capacitive device;
[0008] Set the initial phase information of each capacitive device;
[0009] Read the end-screen current vector value of each capacitive device; set the initial phase information and factory dielectric loss value of each capacitive device;
[0010] Read the end-screen current vector value, initial phase information, and factory dielectric loss value of each capacitive device, calculate the dielectric loss value of the capacitive device under the current phase, and perform dielectric loss fault identification to realize dielectric loss monitoring of capacitive devices.
[0011] A signal trigger edge signal is added after the synchronous acquisition instruction; the synchronous acquisition instruction is used to prompt the capacitive device to prepare to collect data; and the signal trigger edge signal is used to start sampling.
[0012] The signal acquisition speed of the capacitive device is greater than 512 points per cycle.
[0013] The capacitive device identifies the signal trigger edge signal after the synchronous acquisition instruction according to the synchronous acquisition instruction command, and uses the edge of the signal trigger edge signal as the synchronous signal to perform synchronous sampling with a synchronization error of no more than 100nS.
[0014] The capacitive device is a three-phase end-screen online monitoring device or a single-phase end-screen current online monitoring device, which is used to calculate the phase and amplitude of the end-screen current to obtain the end-screen current vector value including the phase and amplitude.
[0015] The end-screen current vector value is saved in a database, and a time stamp is added to all saved data, where the time stamp is the time when the synchronous acquisition instruction is issued.
[0016] The calculation of the dielectric loss value of the capacitive device under the current phase is achieved by the following formula:
[0017]
[0018] Among them, θ An0 is the initial phase angle value of the end screen current of the nth capacitive device under phase A, θ Ai0 is the initial phase angle value under synchronous sampling of the i-th device; θ Ant is the phase angle value of the current at the end screen of the nth device under the current A phase synchronous sampling, θ Ait is the phase angle value of the current at the end screen of the i-th device under the current A-phase synchronous sampling; δ Ant is the relative dielectric loss value of the nth device under the current A phase, δ An0It is the dielectric loss angle of the capacitive equipment when it leaves the factory, that is, the factory dielectric loss value, tanδ Ant is the dielectric loss value of the capacitive device, N is the total number of capacitive devices, i, n = 0...N and i≠n.
[0019] The dielectric loss fault identification comprises the following steps:
[0020] The dielectric loss fault judgment conditions are as follows: tan{max[(θ Ant -θ Ait )-(θ An0 -θ Ai0 )]+δ An0}≥Alarm value
[0021] Among them, θ An0 is the initial phase angle value of the end screen current of the nth capacitive device under phase A, θ Ai0 is the initial phase angle value under synchronous sampling of the i-th device; θ Ant is the phase angle value of the current at the end screen of the nth device under the current A phase synchronous sampling, θ Ait is the phase angle value of the current at the end screen of the i-th device under the current A-phase synchronous sampling; δ An0 It is the dielectric loss angle of the capacitive device when it leaves the factory, that is, the factory dielectric loss value, N is the total number of capacitive devices, i, n = 1...N and i≠n;
[0022] When the dielectric loss fault judgment condition is not met, the current capacitive device has no dielectric loss fault; otherwise, the current capacitive device has a dielectric loss fault.
[0023] A synchronous signal-based dielectric loss monitoring system for capacitive equipment in a substation, used for IED equipment, comprising:
[0024] A synchronous acquisition instruction sending module, used for sending a synchronous acquisition instruction to a capacitive device;
[0025] The information acquisition module is used to read the end-screen current vector value of each capacitive device; set the initial phase information and factory dielectric loss value of each capacitive device;
[0026] The dielectric loss monitoring module is used to read the end-screen current vector value, initial phase information, and factory dielectric loss value of each capacitive device, calculate the dielectric loss value of the capacitive device under the current phase, and perform dielectric loss fault judgment to realize dielectric loss monitoring of capacitive devices.
[0027] A computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, a synchronous signal-based dielectric loss monitoring method for substation capacitive equipment is implemented.
[0028] The present invention has the following beneficial effects and advantages:
[0029] 1. Compared with the prior art, the dielectric loss of each capacitive device is calculated by adding the original dielectric loss value to the tangent value of the phase angle change, which will affect the error; when calculating the relative dielectric loss, other capacitance values that are not in the same phase are referenced and are easily affected by the interphase interference caused by the three-phase imbalance. The present invention takes into account that the dielectric loss of capacitive devices is easily affected by the ambient temperature, and the temperature effects between multiple capacitive devices in the same environment can offset each other. It emphasizes that in order to shield the interphase interference, the capacitive devices between phases are not used to calculate the relative dielectric loss, thereby improving the monitoring accuracy.
[0030] 2. The present invention takes into account the installation of equipment and the distance between signal lines to avoid excessive disturbance in the collection results caused by too long signal lines, and adopts a high-precision digital synchronization design scheme. By sending a synchronous sampling pulse on the RS485 bus after the instruction is completed, the synchronization accuracy of the collection equipment receiving the synchronization instruction is controlled below 100nS, which fully meets the national standard requirements for the monitoring accuracy of capacitive equipment. BRIEF DESCRIPTION OF THE DRAWINGS
[0031] Figure 1 It is a schematic diagram of the installation and connection of each device of the present invention;
[0032] Among them, 1 is the intelligent electronic device for online monitoring of the capacitive equipment of the whole station, 2 is the transformer, 3 is the online monitoring device for the end screen of the transformer bushing, 4 is the end screen adapter sensor for measuring the end screen of the bushing, 5 is the transformer bushing, 6 is the lightning arrester, 7 is the current transformer, 8 is the online monitoring device for the current of the single-phase end screen, and 9 is the RS485 communication line;
[0033] Figure 2 is the end screen current vector diagram;
[0034] Figure 3 This is a schematic diagram of high-precision synchronous acquisition instructions. DETAILED DESCRIPTION
[0035] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.
[0036] The present invention relates to a dielectric loss collection and calculation method for solving high-precision synchronous sampling and using relative dielectric loss to characterize the dielectric loss change of capacitive equipment. The purpose is to provide a theoretical calculation basis for the distributed arrangement and high-precision collection of the capacitive equipment of the whole station, and solve the problem that the dielectric loss collection of the current capacitive equipment is often disturbed. The synchronous sampling command is mainly issued by the main station using RS485 communication, and the vector acquisition terminal performs synchronous acquisition according to the synchronization command of the main station and the clock edge of the synchronization signal. The information collected by the synchronized vector acquisition terminal is then averaged to calculate the first reference phase, and the difference between the current vector of the end screen of the measured device and this reference vector is recorded. The dielectric loss angle in the future can be obtained by subtracting the difference when recording from the new difference and adding the original dielectric loss angle of the device to form the dielectric loss angle of the current device. The relative dielectric loss can be calculated by calculating the tangent value of this dielectric loss angle. The advantage of using this method is that it is not necessary to lead the signal line from the voltage transformer, avoiding the influence of the voltage transformer accuracy due to the one-bit situation. On the other hand, it also avoids the measurement error caused by the slow dynamic response speed of the voltage transformer, which makes the dielectric loss value jump too large. This approach can make the results more stable and reliable.
[0037] The implementation of a method for monitoring dielectric loss of substation capacitive equipment based on synchronous signals needs to include: IED, transformer bushing end screen online monitoring device, end screen adapter sensor for measuring bushing end screen, and single-phase end screen current online monitoring device. The above three types of equipment need to be connected using RS485 bus, and all devices must be connected to the same RS485 bus to obtain synchronous signals.
[0038] The synchronization signal needs to use a unified instruction format and synchronization pulse edge as the basis for data synchronization collection. The key point of the synchronization instruction is that after receiving the synchronization instruction and verifying that it is correct, the next pulse edge is the synchronization time point. After all devices capture the pulse edge, the AD of each device starts synchronous collection. During this process, the response time difference of each device should be less than 100nS to ensure the error requirements of subsequent calculations.
[0039] After synchronous sampling is completed, the vector value of the end-screen current of each capacitive device under test is calculated at that moment. Then the IED will read the synchronous sampling data of the end-screen current monitoring devices of all capacitive devices this time and save it for subsequent analysis and calculation of dielectric loss functions.
[0040] like Figure 1 , Figure 2 As shown, the present invention specifically comprises the following steps:
[0041] 1. The IED device sends a synchronous acquisition instruction, and after the instruction is completed, a synchronous sampling pulse is sent on the RS485 bus. Figure 3As shown, an IED (device 1) issues a synchronization command, followed by a signal trigger edge signal. The synchronization command of the signal is used to prompt all devices to prepare to collect data, and the synchronization trigger edge signal is used to start sampling immediately.
[0042] 2. All capacitive online monitoring devices (single-phase end screen current online monitoring device 8 and transformer three-phase bushing end screen online monitoring device 3) start sampling immediately after collecting the synchronization pulse. Therefore, the sampling time of each device is synchronized to the time when the trigger pulse edge is generated, so that the synchronization accuracy can reach the ns level.
[0043] 3. After sampling, calculate the phase and amplitude of the end screen current. The calculation uses the Fourier transform method to obtain the fundamental amplitude and phase information.
[0044] 4. After the IED device waits for the capacitive online monitoring device to complete the calculation, it reads the end-screen current vector value (including amplitude and phase) calculated on each capacitive device.
[0045] 5. The IED saves the read end-screen current vector value to the local database and adds a time stamp (the time when the trigger command is issued) to all saved data for future query and data analysis.
[0046] 6. Modify the initial phase information of each device in the IED record manually or through remote commands, and enter the factory dielectric loss value of the capacitive device for calculating the dielectric loss change.
[0047] 7. The method for calculating the dielectric loss value of the capacitive device in a certain phase (taking phase A as an example) is:
[0048]
[0049] θ An0 is the initial phase angle value of the current at the end screen of the nth device under phase A, θ Ai0 is the initial phase angle value under synchronous sampling of the i-th (i≠n) device; θ Ant is the phase angle value of the current at the end screen of the nth device under the current A phase synchronous sampling, θ Ait is the phase angle value of the current at the end screen of the i-th device under the current A-phase synchronous sampling; δ Ant is the current relative dielectric loss value of the nth device under the current A phase, δ An0 It is the dielectric loss angle of the capacitive device when it leaves the factory.
[0050] 8. The method for determining which capacitive device has dielectric loss failure is:
[0051] tan{max[(θ Ant -θ Ait )-(θAn0 -θ Ai0 )]+δ An0}≥alarm value (i=0~N, i≠n).
[0052] The present invention takes into account that the dielectric loss of capacitive devices is easily affected by the ambient temperature, and the temperature effects of multiple capacitive devices in the same environment can offset each other. Therefore, the leakage current vector angle of two capacitive devices in the same phase is subtracted, and the average phase angle is used to evaluate the phase angle change. This avoids the large change in the machine loss value of normal equipment due to a large change in a certain reference vector. This calculation formula can closely characterize the dielectric loss of capacitive devices. The more capacitive devices there are on the same phase, the more stable the relative value will be. This calculation formula is the phase angle subtraction between two capacitive devices, instead of using the phase angle subtraction between the signal and the voltage transformer signal. It can shield the dielectric loss deviation caused by the phase not being able to quickly and accurately follow the system voltage phase due to the hysteresis characteristics of the electromagnetic change of the voltage transformer. Based on the principle that the insulation characteristics are irreversible without human processing, and using tan{max[(θ Ant -θ Ait )-(θ rn0 -θ Ai0 )]+δ An0}≥alarm value (i=0~N, i≠n), this calculation method is used as a strict judgment, and the alarm result obtained is more accurate.
Claims
1. A method for monitoring dielectric loss of capacitive equipment in a substation based on synchronous signals, characterized in that: The following steps are involved: Set the factory dielectric loss value of capacitive equipment; Sending synchronous acquisition instructions to the capacitive device; Read the end-screen current vector value of each capacitive device; Set the initial phase information of each capacitive device; Read the end-screen current vector value, initial phase information, and factory dielectric loss value of each capacitive device, calculate the dielectric loss value of the capacitive device under the current phase, and perform dielectric loss fault identification to realize dielectric loss monitoring of capacitive devices.
2. A method for monitoring dielectric loss of capacitive equipment in a substation based on synchronous signals according to claim 1, characterized in that: A signal trigger edge signal is added after the synchronous acquisition instruction; the synchronous acquisition instruction is used to prompt the capacitive device to prepare to collect data; and the signal trigger edge signal is used to start sampling.
3. A method for monitoring dielectric loss of capacitive equipment in a substation based on synchronous signals according to claim 1, characterized in that: The signal acquisition speed of the capacitive device is greater than 512 points per cycle.
4. A method for monitoring dielectric loss of capacitive equipment in a substation based on synchronous signals according to claim 1, characterized in that: The capacitive device identifies the signal trigger edge signal after the synchronous acquisition instruction according to the synchronous acquisition instruction command, and uses the edge of the signal trigger edge signal as the synchronous signal to perform synchronous sampling with a synchronization error of no more than 100nS.
5. The method for monitoring dielectric loss of capacitive equipment in a substation based on synchronous signals according to claim 1, characterized in that: The capacitive device is a three-phase end-screen online monitoring device or a single-phase end-screen current online monitoring device, which is used to calculate the phase and amplitude of the end-screen current to obtain the end-screen current vector value including the phase and amplitude.
6. A method for monitoring dielectric loss of capacitive equipment in a substation based on synchronous signals according to claim 1, characterized in that: The end-screen current vector value is saved in a database, and a time stamp is added to all saved data, where the time stamp is the time when the synchronous acquisition instruction is issued.
7. A method for monitoring dielectric loss of capacitive equipment in a substation based on synchronous signals according to claim 1, characterized in that: The calculation of the dielectric loss value of the capacitive device under the current phase is achieved by the following formula: Among them, θ An0 is the initial phase angle value of the end screen current of the nth capacitive device under phase A, θ Ai0 is the initial phase angle value under synchronous sampling of the i-th device; θ Ant is the phase angle value of the current at the end screen of the nth device under the current A phase synchronous sampling, θ Ait is the phase angle value of the current at the end screen of the i-th device under the current A-phase synchronous sampling; δ Ant is the relative dielectric loss value of the nth device under the current A phase, δ An0 It is the dielectric loss angle of the capacitive equipment when it leaves the factory, that is, the factory dielectric loss value, tanδ Ant is the dielectric loss value of the capacitive device, N is the total number of capacitive devices, i, n = 0...N and i≠n.
8. A method for monitoring dielectric loss of capacitive equipment in a substation based on synchronous signals according to claim 1, characterized in that: The dielectric loss fault identification comprises the following steps: The dielectric loss fault judgment conditions are as follows: tan{max[(θ Ant -θ Ait )-(θ Am0 -θ Ai0 )]+δ An0 }≥Alarm value Among them, θ An0 is the initial phase angle value of the end screen current of the nth capacitive device under phase A, θ Ai0 is the initial phase angle value under synchronous sampling of the i-th device; θ Ant is the phase angle value of the current at the end screen of the nth device under the current A phase synchronous sampling, θ Ait is the phase angle value of the current at the end screen of the i-th device under the current A-phase synchronous sampling; δ An0 It is the dielectric loss angle of the capacitive device when it leaves the factory, that is, the factory dielectric loss value, N is the total number of capacitive devices, i, n = 1...N and i≠n; When the dielectric loss fault judgment condition is not met, the current capacitive device has no dielectric loss fault; otherwise, the current capacitive device has a dielectric loss fault.
9. A synchronous signal-based substation capacitive equipment dielectric loss monitoring system, characterized in that: For IED equipment, including: A synchronous acquisition instruction sending module, used for sending a synchronous acquisition instruction to a capacitive device; The information acquisition module is used to read the end-screen current vector value of each capacitive device; set the initial phase information and factory dielectric loss value of each capacitive device; The dielectric loss monitoring module is used to read the end-screen current vector value, initial phase information, and factory dielectric loss value of each capacitive device, calculate the dielectric loss value of the capacitive device under the current phase, and perform dielectric loss fault judgment to realize dielectric loss monitoring of capacitive devices.
10. A computer-readable storage medium, characterized in that: The storage medium stores a computer program, and when the computer program is executed by the processor, a method for monitoring dielectric loss of capacitive equipment in a substation based on a synchronization signal as described in any one of claims 1 to 8 is implemented.