CN104634442A - Method for indirectly measuring noise of transformer - Google Patents

Abstract

In the measurement of the transformer noise, the requirement for the peripheral background noise is very high, the noise value measured in a special noise measurement room is the noise of the transformer, in an operation field, the noise measured in a conventional method is the noise generated by all noise sources in the site due to the affection of the peripheral environment and the noise of other equipment and is not just the noise value independently generated by the transformer, so that the measurement value of the noise of the transformer is great in error. The noise of the transformer is produced by the vibration of an iron core due to the magnetostriction and the vibration of a transformer winding under the electromagnetic field effect in a leakage magnetic field, and the vibration of a transformer part is directly relates to the noise. If the noise generated by the transformer is indirectly calculated by virtue of a vibration signal on the surface of the transformer, the affection of the environmental noise and the noise of other equipment can be avoided, and the measurement result is the noise generated by the transformer.

Description

A Method of Indirect Measurement of Transformer Noise

technical field

The invention relates to a method for indirect measurement of noise generated during transformer operation.

Background technique

With the development of high-voltage direct current transmission, the noise generated by the operation of substations and converter stations has more and more serious impact on the surrounding environment, and the noise generated by transformer vibration is one of the important noise sources. Therefore, the problem of transformer operation noise has become Significant sources of noise affecting the surrounding environment. Especially when there is harmonic flux in the transformer core and harmonic current flows in the transformer winding, the vibration of the transformer core and winding is more complicated. When the excitation frequency is equal to the natural frequency of the structure, resonance will occur. Make the transformer emit more intense noise.

In the measurement of transformer noise, the requirements for the background noise of the surrounding environment are very strict. Only the noise value of the transformer measured in a special noise measurement laboratory is the noise emitted by the transformer itself. In the transformer operation site, it is affected by the surrounding environment noise The impact of noise, as well as the impact of noise from other electrical equipment. When there are multiple noises from different sources in the space, they may have different amplitudes and frequencies. The measured noise is the superposition of the noise generated by all equipment noise sources in the entire site. The measured noise value is not the noise value generated by the transformer alone, so there is a large error in the measured value of the transformer's own noise.

The noise of the transformer is caused by the vibration of the iron core generated by the magnetostriction of the transformer core and the vibration generated by the electromagnetic force of the transformer winding in the leakage magnetic field. The noise of the transformer is caused by the vibration transmission of its core and winding. Transformer components There is a direct relationship between the vibration of a vehicle and its noise level. Due to the limitations of many conditions mentioned above in the direct measurement of transformer noise, if the vibration signal on the surface of the transformer is used to indirectly calculate the noise radiated by it, the mutual influence of environmental noise and other power equipment noise can be avoided, so that the measurement result is the true value of the transformer itself. generated noise.

Contents of the invention

The invention provides a transformer vibration test and testing system, which can measure the real-time conditions of the vibration of each part of the transformer iron core and winding.

The transformer vibration experiment test system includes seven piezoelectric vibration acceleration sensors, which are attached to the transformer core and windings through magnetic poles, and are used to test the real-time vibration signals of the transformer core and windings.

Two signal conditioning modules, which receive the signal detected by the piezoelectric vibration acceleration sensor, and the transmitted vibration signal is filtered and amplified by the signal conditioning module.

A vibration signal display terminal accepts the vibration acceleration data filtered and amplified by the signal conditioning module.

The specific steps for indirect measurement of transformer noise through the transformer vibration test system are as follows:

(1) From the above-mentioned mechanism of transformer noise generation, it can be seen that since the noise radiated from the transformer casing is closely related to its vibration, when calculating the noise generated by the transformer, it can be calculated from the vibration response of the casing under the action of electromagnetic vibration force. out.

(2) The vibration signal of the corresponding point measured by the vibration acceleration sensor attached to the transformer core and winding surface is transmitted to the signal conditioning module, through which the vibration acceleration signal is filtered and amplified, and finally the conditioned acceleration signal is sent to The display terminal obtains the acceleration signals of each vibration measurement point.

(3) When performing vibration tests on transformers, piezoelectric vibration acceleration sensors are usually used to measure the vibration acceleration on its surface. Piezoelectric vibration acceleration sensors have the advantages of small size, light weight, and wide operating frequency, so they can be used in complex electromagnetic environments. Under the measurement, and then through the calculation of the transformer noise signal.

(4) In order to comprehensively collect the vibration signals on the surface of the transformer, set 7 measurement points on the surface of the transformer, and attach the vibration acceleration sensor to the surface of the transformer through the magnetic poles to measure the vibration acceleration signals of the points respectively.

(5) Calculate the radiated noise level according to the vibration signal of the transformer surface, establish a transformer vibration test system, measure the vibration signal of the transformer surface, and then calculate the sound power level of the noise.

In the above-mentioned vibration test system, the main signal conditioning module is the vibration acceleration signal conditioning block, which is connected to the vibration acceleration sensor attached to the surface of the transformer through the connection line, collects the real-time vibration acceleration from the surface of the transformer, and performs vibration acceleration Amplify and filter.

The signal conditioning module is connected with the final acceleration signal display terminal through a transmission line.

The present invention uses vibration acceleration signals on the surfaces of transformers to indirectly measure its noise value, which can avoid the influence of noise from various sources in space on the measured value of other power equipment, and determine its noise value more accurately and scientifically.

Description of drawings

The following pictures are used to explain in detail the principle and process of indirectly measuring transformer noise through vibration acceleration testing;

Fig. 1 is the structural schematic diagram of the measured transformer of the present invention, Fig. 2 is the physical figure of the measured transformer and the installation location figure of vibration acceleration sensor, Fig. 3 is the structural representation of whole transformer vibration acceleration testing system of the present invention.

Detailed ways

The vibration acceleration of a single-phase four-column dry-type transformer is tested at various points.

Figure 1 shows the structural principle diagram of the test transformer; Figure 2 is the physical picture of the test transformer and the installation position of the vibration acceleration in the vibration test system. In the figure, the vibration acceleration sensor is closely attached to each surface of the transformer to detect each point in real time vibration signal; the signal measured by the vibration acceleration in Figure 3 is transmitted to the 482C05 signal conditioning module through the transmission line for signal filtering and amplification, and the display terminal of the MR8857 signal storage recorder is connected to the signal conditioning module to receive the vibration processed by the conditioning module acceleration signal.

The above-mentioned vibration test system that indirectly deduces the noise level of the transformer through the vibration acceleration signal of the transformer surface is measured according to the following steps:

(1) The physical quantities that characterize the vibration intensity include vibration acceleration level and vibration velocity level; (2) Vibration acceleration level is defined as:

;

in, Indicates the effective value of the vibration acceleration (unit: );

is the reference value of vibration acceleration, and its value is (unit: );

(3) Vibration speed level is defined as:

;

in, Indicates the effective value of the vibration velocity (unit: );

is the reference value of the vibration velocity, and its value is (unit: );

(4) There is the following derivative relationship between vibration acceleration and vibration velocity:

;

Therefore, it can be deduced that there is the following relationship between the vibration acceleration level and the vibration velocity level:

;

(5) When the transformer is running, the surface of each part of the transformer vibrates, and there is the following relationship between the surface vibration and the radiated sound power:

;

in, represents the air density value, represents the speed of sound in air, and in noise analysis, the two are combined as , called air acoustic impedance (unit: ); is the noise radiating surface area (unit: ); is the effective value of the vibration velocity of the vibrating surface (unit: ); is the radiation ratio.

(6) The sound power level can indicate the strength of the noise, the sound power level is defined as:

;

is the sound power value radiated by the vibrating surface (unit: );

is the reference sound power, ;

(7) There is the following relationship between sound power level and vibration acceleration level:

;

In the formula, It is called air acoustic impedance (unit: ), is the reference air acoustic impedance, its value ; is the noise radiating surface area (unit: ), is the base area, its value ; is the radiation ratio, is the reference radiation ratio, its value ; is the vibration acceleration frequency value (unit: );

(8) When measuring the noise of a certain surface of the transformer, the surface is divided into For parts with equal areas, since the vibration acceleration levels of each part are different, the vibration acceleration level of each part is calculated, and then the average value of the vibration acceleration level is calculated as the vibration acceleration level value in the above formula, namely:

;

is the average value of the vibration acceleration level, for the first Part of the vibration acceleration level.

(9) The final sound power level is:

.

Claims (4)

1. Vibration signals measured by piezoelectric vibration acceleration sensors attached to the surfaces of the transformer core and the winding are transmitted to the signal conditioning module, the vibration acceleration signals are filtered and amplified through the signal conditioning module, and finally the conditioned acceleration signals are transmitted to a display terminal to obtain acceleration signals of each vibration measuring point.

2. In the vibration testing system, the main signal conditioning module is a vibration acceleration signal conditioning module, is connected with the vibration acceleration sensor attached to the surface of the transformer through a connecting wire, collects the real-time vibration acceleration condition from the surface of the transformer, and amplifies and filters the vibration acceleration.

3. The invention adopts the vibration acceleration signals of the measured points of the measuring transformer to indirectly measure the noise value of the measuring transformer, and can avoid the influence of the noise of other power equipment with various sources in the space on the measured value, thereby more accurately and scientifically determining the noise value of the measuring transformer.

4. And calculating the level of the radiated noise according to the surface vibration signal of the transformer, establishing a transformer vibration test system, measuring the surface vibration signal of the transformer, and further calculating to obtain the level of the sound power level of the noise.