Optical sensors for power transformer monitoring: A review

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The invention relates to the technical field of power transformer winding deformation detection, in particular to a linear correlation coefficient calculation method for frequency response winding deformation analysis. The method includes according to the transformer frequency response data measured by the transformer to be diagnosed at different times twice, determining the winding deformation condition by calculating the phase-by-phase longitudinal linear correlation coefficient and calculating the transverse or inter-phase linear correlation coefficient; or calculating the transverse or inter-phase linear correlation coefficient according to the frequency response data measured by the transformer to be diagnosed at this time; converting the relevant coefficient required by the deformation determination, and evaluating the deformation degree of the winding according to the set determination standard. According to the curve data obtained by the frequency response method, the correlation coefficient for determining the deformation degree can be quickly and accurately calculated, the fault type and degree of the winding set can be determined according to the peak change in the curve, and a basis is provided for evaluating the health condition of the transformer.

Linear correlation coefficient calculation method for frequency response winding deformation analysis

Frequency response analysis is widely used as a method for the offline diagnosis of winding deformations in power transformers. To apply it to a working transformer, people need to determine how to inject the excitation signal and measure the response signal for windings that bear a rated voltage and current. In this study, a method to obtain the frequency response curve online is proposed. It uses the principle of magnetic field coupling to inject a frequency sweep signal into the windings through a Rogowski coil. Another Rogowski coil sensor placed at the root of a high-voltage bushing is used to measure the response current signal. Experiments on a 72.5 kV bushing show that metal accessories of the bushing have no influence on the injection or the measurement. The feasibility of this method was verified by experiments on charged 110/35/10 kV transformers at a factory and a working 35 kV transformer in a power station. The results show that it is safe to install the Rogowski coil at the root of the high-voltage bushing. The excitation signal can be injected into live windings and the response signal is measurable. Strong electromagnetic power frequency noise can be reduced and the frequency response curve can be measured online.

Proposed methodology for online frequency response analysis based on magnetic coupling to detect winding deformations in transformers

The present invention discloses a method and a system for on-line diagnosis of transformer winding deformation The method comprises: injecting a sweep signal from a high-voltage lead-out line of a transformer winding by way of magnetic field induction; acquiring an excitation current signal induced on the high-voltage lead-out line of the transformer winding; obtaining the response current signal on the neutral ground line of the transformer winding; obtaining the frequency response curve according to the transfer function relationship, which is constructed by using the excitation current signal and the response current signal, of the transformer winding; based on the diagnosis method in the DLT911-2004 standard, diagnosing the frequency response curve; and determining the deformation of the transformer winding According to the invention, the excitation signal injection and response signal measurement do not need direct electrical connection with the transformer winding, making the high-voltage transformer winding operate in a high-voltage and high-current condition and realizing the real-time detection of the transformer winding deformation online

Method and system for on-line diagnosis of transformer winding deformation

The invention discloses a device and a method for electrified monitoring of transformer winding deformation. The device comprises an excitation source, an excitation signal injection sensor, response signal measuring sensors and a main controller, wherein the excitation source is used for receiving a sweep frequency sinusoidal voltage signal output by the main controller, and outputting the sweep frequency sinusoidal voltage signal to the excitation signal injection sensor after carrying out power amplification; the excitation signal injection sensor is used for generating induced potential on a transformer winding in a magnetic field coupling manner according to the sweep frequency sinusoidal voltage signal; the response signal measuring sensors are used for measuring sweep frequency response current signals generated by means of the induced potential on two ends of the transformer winding, and outputting the sweep frequency response current signals to the main controller; and the main controller is used for acquiring a frequency response curve of the transformer winding according to the sweep frequency sinusoidal voltage signal and the sweep frequency response current signals. According to the method and the device, the injection of the excitation signal and the measurement of the response signals do not require direct connection with the transformer winding, and the real-time detection of the winding deformation condition of an online operating transformer is realized.

Device and method for electrified monitoring of transformer winding deformation

The invention discloses a transformer winding deformation on-line diagnosis method. The method comprises the following steps: injecting a sweep frequency signal to a neutral point grounding wire of atransformer winding, and obtaining a current signal I 1 sensed by the neutral point grounding wire of the transformer winding, obtaining a voltage signal V 1 sensed by the neutral point groundingwire of the transformer winding, and obtaining a current signal I 2 on a high-voltage lead-out wire of the transformer winding; constructing an equation based on the V 1, the I 1 and I 2, anddetermining the trajectory of each vector changing with the frequency f of the sweep frequency signal as a frequency response curve of the transformer winding; comparing the obtained frequency response curves through a longitudinal comparison method and a horizontal comparison approach provided in DL/T911, and determining a maximum canonical correlation coefficient between the vectors corresponding to the frequency response curves according to canonical correlation coefficients between existing mature random vectors; and determining deformation conditions of the transformer winding according to a diagnostic method based on correlation coefficient in the DL/T911.

Ma Xianwei

Papers

Proposed methodology for online frequency response analysis based on magnetic coupling to detect winding deformations in transformers

Method and system for on-line diagnosis of transformer winding deformation

Device and method for electrified monitoring of transformer winding deformation

Transformer winding deformation on-line diagnosis method and system