16
2022
-
06
Do you know about the testing of transformer equipment winding deformation?
source：
Classification:
Industry News
【Summary Description】The issue of winding deformation in power transformers is considered a common problem, which may have multiple causes, the most significant of which is the impact of short-circuit current. The core content of this standard focuses on a testing method, represented by Frequency Response Analysis (SFRA).
1. Core Content of Concern
The issue of winding deformation in power transformers is considered a common problem, which may have multiple causes, the most significant being short-circuit current impact. The core content of this standard focuses on a testing method, represented by frequency response analysis SFRA.
2. Applicable Scope
The SFRA for winding deformation in power transformers is applicable to power transformers with voltage levels of 66KV and above, as well as other special-purpose transformers; for transformers with voltage levels of 35KV and below, the DL/T1093 low voltage short-circuit impedance method/reactance method is usually adopted.
3. Several Key Professional Terms
According to the differences between DL/T 911-2016 and DL/T 911-2004, the new version adds a term "three-phase frequency response fingerprint," which refers to the overall frequency response curve that characterizes the correlation and differences in the frequency response characteristics of the three-phase windings of transformers of the same model and voltage level.
Frequency response is divided into amplitude frequency response and phase frequency response, representing the variation of the magnitude or phase of the transfer function H(jw) with angular frequency w.
4. Basic Testing Principles
Under the action of high-frequency voltage, each winding of the transformer can be regarded as a passive linear two-port network composed of linear resistors, inductors (mutual inductance), capacitors, and other distributed parameters, whose internal characteristics can be described by the transfer function H(jw). If the winding deforms, the distributed inductance, capacitance, and other parameters inside the winding will inevitably change, leading to changes in the zeros and poles of its equivalent network transfer function, thus altering the frequency response characteristics of the network.
The figure shows the basic detection circuit of the frequency response analysis method, where:
(1) U1 and U2 are the excitation voltage and response voltage of the equivalent network, respectively. In frequency scanning mode, by continuously changing the external Us frequency f (angular frequency w=2Πf), the ratio of the signal amplitude of the response voltage U2 to the excitation voltage U1 can be measured at different frequencies, obtaining the amplitude frequency response curve of the winding under specified excitation and response conditions, usually expressed in logarithmic form;
(2) Us is the voltage of the sine wave excitation signal source, usually low voltage, Rs is the output impedance of the signal source, typically 50Ω;
(3) R is the matching resistor, which should be 50Ω, as uniformly specified in applications;
(4) L, K, and C are the distributed inductance, capacitance, and ground distributed capacitance per unit length of the winding. When the winding deforms, these characteristic values will change, thereby affecting the changes in the transfer function.
When calculating the transfer function H, the modulus of the transfer function is H(f)=20lg[U2(f)/U1(f)], and the usual range is between -80dB and 0dB, while the voltages at the excitation and response ends can be calculated using peak or effective values.
5. Important Requirements for Testing Instruments
In addition to some basic requirements for the transformer winding deformation testing instrument, there are several important requirements, including the following aspects. Overall, the performance requirements for the instrument are relatively high.
6. Detection Methods and Spectrum Waveform Analysis Methods
From an application perspective, the specific detection operation methods and spectrum waveform analysis are the essence of analyzing and judging transformer winding issues. This version of the standard specifically adds examples of winding deformation analysis, including longitudinal comparison method examples, transverse comparison method examples, comprehensive comparison method examples, common interference waveforms, etc.; in addition, the correlation coefficient R is an auxiliary method for judging transformer winding deformation, which has also been revised.
What if you have more needs?
A set design, research and development, manufacturing and sales in one of the high-tech enterprises
Mobile two-dimensional code
Jiangxi Ganzhong Transformer Co., Ltd.
Address: No.2, Xingzhou Road, Xingan County, Ji'an City, Jiangxi Province
Telephone:0796-2805958
Email：2253761828@qq.com
SAF Coolest v1.3 设置面板 DOBSE-ZJNW-AAAWE-ASE
无数据提示
Sorry, the current column has no content for the time being.!
You can view other columns or returnHome Page