Deformation of transformer winding core directly or indirectly damages the transformer. This kind of fault potential can not be diagnosed by the conventional conventional electrical test on the vibration online monitoring method for transformers and similar structures. The earliest shunt reactors used in foreign countries reflect the vibration of transformer body through on-line monitoring to reflect the windings. The status of iron cores is a matter of recent years. Compared with FRALVI and methods for measuring short-circuit reactances such as on-line or off-line, the vibration method not only detects fault windings but also detects core conditions, and the method is not electrically connected to the power system. Safety Reliable, therefore should study to understand the power transformer in no-load conditions and body vibration characteristics suffered short-circuit, which is the basis of no-load vibration characteristics of the principle 1 power transformer in stable operation, the silicon steel core, winding generated under the action of electromagnetic fields Vibration and transmission of transformer oil caused by transmission of transformer body vibration The vibration of the transformer body surface is closely related to the state of displacement and deformation of the transformer windings and iron core clamping conditions. Therefore, the winding and core conditions can be monitored by on-line measurement of body vibration.
The main flux generated by the exciting current at the same tapping position of the transformer remains unchanged in size under no-load, load, and load changes, so the magnetostrictive vibration caused by the magnetostriction also remains basically unchanged at different taps. The vibration characteristics of the position transformer core, only need to measure the vibration of the transformer under no-load conditions of the transformer. Under the load condition, the vibration of the transformer body also includes the vibration of the winding under the load current, so the winding vibration signal can be measured under the load condition of the transformer. 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 loosened or deformed compared to the normal vibration signal, and the amplitude at the original frequency is also The change occurs, and the greater the displacement distortion, the greater the change in high-frequency components and amplitude. The relationship between the vibration characteristics at each position of the transformer body and the closest vibration source is the closest, and the vibration signal is changed according to the transformer body's various locations. The degree can easily determine which part of the winding or core has failed, that is, use the vibration method to monitor the power transformation online. The fault location can be realized. Therefore, 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 status of the core, so as to determine whether the core is in failure; the vibration signal of the winding must be from the load. The vibration signal of the core is removed from the body vibration signal to determine whether the winding is faulty. 2 Tests and results 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 vibration of the transformer body ( The voltage amplifier is converted into a voltage signal proportional to the voltage amplifier through the charge amplifier. Therefore, the test system is used to perform a vibration test on the low- and high-voltage side of a power transformer in a long-term no-load test when the transformer cooling system shuts down the transformer. The parameters are as follows: Model: OSFPSZI 2.2 Test Results and Analysis The vibration sensor is attached to the lower arm of the high and low pressure arms with a double-sided tape. Since the low-voltage side of phase C is connected to the test power supply, the wiring phase of the transformer body vibration test test is not measured. The frequency spectrum of each phase of the high and low voltage side signals is shown in Table 3, respectively. After analysis, the fundamental frequency of the vibration of the transformer during no-load test is 100 Hz, and there are other high-order harmonic components. After 1 000 Hz, the harmonics are basically attenuated to 0. This is consistent with the results of theoretical analysis.
The vibration characteristics of the body on both sides of the high and low pressure are different. The highest amplitude in the frequency domain of the vibration signal at the same position on the high voltage side of the three phases appears at the same frequency position, that is, the high voltage side is at 400 Hz; and the highest amplitude at the low frequency side of the vibration signal in the frequency domain is at the same position at the 100 Hz high and low voltage sides. The fundamental frequency of the vibration signal and the amplitude of each harmonic are in an order of magnitude, ie, the frequency domain characteristics are basically the same. However, it can be seen from the slight difference in the amplitude-frequency characteristics of each phase on the high-voltage side that, if the amplitude of the main frequency is relatively large, then the harmonic characteristics of the 300MVA power transformer with no-load vibration is found to be found except that the main frequency of the high-voltage side appears. Outside 300 Hz, other vibration characteristics are the same as those of the above-mentioned transformer. 3 Conclusions The vibration signal of the transformer body is based on 100 Hz and has other harmonic components. The amplitude of harmonics after 1000 Hz is basically attenuated to 0. For the same position on the high-pressure side or the low-pressure side, the vibration signal of the body has a common rule, 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. Different types of transformers may have different main frequencies due to transformer structure, core and winding state of each phase, and transformer box structure and other factors / there is a certain difference in the amplitude of vibration on the same frequency of the same side of the transformer, but the main frequency range When the value is relatively large, the harmonic component amplitude is also slightly higher, and vice versa
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