The transformer winding core deformation directly or indirectly damages the transformer. This kind of fault hazard is generally unable to diagnose the vibration on-line monitoring method of transformers and similar structural power equipment. The earliest foreign application to shunt reactors reflects the winding vibration by online monitoring transformer body vibration. And the core condition is a matter of recent years. Compared with FRALVI and online or offline measurement of short-circuit reactance, the vibration method can not only detect the fault winding, but also detect the core condition, and the method has no electrical connection with the power system. Reliable, so we should study the vibration characteristics of the power transformer under no-load conditions and short-circuit conditions. The no-load vibration characteristics are the foundation 1 principle. When the power transformer is in stable operation, the silicon steel core and winding are generated under the action of electromagnetic field. The vibration and the transmission of the transformer oil cause the vibration of the surface of the transformer body to be closely related to the displacement and deformation state of the transformer winding and the core. Therefore, the condition of the winding and the core can be monitored by measuring the vibration of the body.
The main magnetic flux generated by the excitation current of the same tap position of the transformer in the core is basically unchanged when the no-load, load and load change, so the core vibration caused by magnetostriction remains basically unchanged to obtain different taps. The vibration characteristics of the position transformer core only need to measure the vibration of the body under the no-load condition of the transformer. The vibration of the transformer body under the load condition also includes the vibration of the winding under the load current. Therefore, the vibration signal of the winding can be measured under the condition of the transformer load. The vibration signal is compared with the vibration signal at no-load to obtain a higher frequency component of the vibration signal measured when the transformer core or winding is loose or deformed compared with the normal vibration signal, and the amplitude at the original frequency will also be Changes occur, and the larger the displacement deformation, the higher the high-frequency component and amplitude change. The vibration characteristics at each position of the transformer body are most closely related to the vibration source closest to the distance, and the vibration signal is changed according to the transformer body. The degree can easily determine which part of the winding or core has failed, that is, using the vibration method to monitor the power transformer online. Fault positioning can be realized. When the vibration method is used to monitor the power transformer online, the vibration signal of the body must be measured under no-load conditions to obtain the vibration state of the core, thereby determining whether the core is faulty; the winding vibration signal must be from the load The vibration signal of the core is removed from the vibration signal to determine whether the winding is faulty. 2 Test and result 2.1 Test object and test wiring Simulation experiments show that the transformer body vibration signal test system can correctly measure the acceleration signal of the transformer body vibration ( The voltage is converted to a voltage signal proportional thereto by the charge amplifier. Therefore, the test system is used to test the vibration of the surface of the body of the low-voltage side of the power transformer in a long-term no-load test. The transformer cooling system turns off the transformer. The parameters are as follows: Model: OSFPSZI 2.2 Test results and analysis The vibration sensor is attached to the lower and lower arms of the high and low pressure arms with double-sided tape. Since the test power supply is connected to the low-voltage side of the C-phase, the wiring phase of the vibration test of the transformer body is not measured. The spectrum of the vibration signals of the high and low voltage sides is shown in the analysis after 3 measurements. The fundamental frequency of the vibration of the transformer during the no-load test is 100 Hz, and there are other higher harmonic components. The harmonics after 1 000 Hz are basically attenuated to 0. This is consistent with the results of theoretical analysis.
The vibration characteristics of the high and low pressure sides are different. The highest amplitude in the frequency domain of the vibration signal at the same position on the three-phase high-voltage side appears at the same frequency position, that is, the high-voltage side is at 400 Hz; and the highest amplitude in the frequency domain of the low-voltage side vibration signal is at the same position on the high-low voltage side of the 100 Hz. The fundamental frequency of the vibration signal and the amplitude of each harmonic are on the order of magnitude, that is, the frequency domain characteristics are substantially the same. However, it can be seen from the slight difference of the amplitude-frequency characteristics of the high-voltage side. If the amplitude of the main frequency is relatively large, the no-load vibration characteristic of another 300MVA power transformer is found to be in addition to the high-frequency side main frequency. Outside of 300 Hz, the other vibration characteristics are the same as those of the above transformer. 3 Conclusion The vibration signal of the transformer body is based on 100 Hz and has other harmonic components. The harmonic amplitude after 1000Hz is basically attenuated to 0. For the same position on the high-voltage side or the low-voltage side, the vibration signals of the body have a common law, that is, the main frequency of the vibration is the same, and the amplitude-frequency characteristics of the vibration signals of each phase are basically similar but The main frequency of different types of transformers may be different due to the transformer structure, the phase of each phase and the winding compression and the structure of the transformer box. The amplitude of the vibration at the same frequency of the same side of the transformer has a certain difference, but the main frequency When the value is relatively large, the harmonic component amplitude is also slightly higher, and vice versa.
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