# Application Study of Adaptive Tracking Algorithm in Active Noise Control System of Transformer
## 4 Discussion
### Experimental Program  
The experiment was carried out in the 220 kV substation shown in Figure 1. After the discussion and analysis of Section 2, the noise level at the east, south, and north side of the substation has reached the environmental standard, but the noise level near the residential area in the west side was not up to standard. Noise in such areas needed to be reduced. In theory, the distance between the primary sensor and the secondary sound source is much better. In this way, the maximum effect of the interference source on the primary sensor can be avoided. The smaller the distance between the primary acoustic channel and the secondary acoustic channel of the primary sensor and the secondary acoustic channel to the secondary sound source, the smaller the transmission delay of the acoustic channel, so as not to consider the transfer function of the acoustic channel in the control algorithm. No phase compensation is required. However, in the actual substation environment, the secondary sound source and the primary sensor need to meet the substation safety distance requirements. In addition, if the secondary sound source is too close to the primary sensor, the acoustic feedback makes the secondary sound source a new source of interference, which can even lead to algorithm failure and system instability. The position of the error sensor should not be too  
Figure 9: Secondary source array structure. close or too far away from the secondary sound source. The farther the error sensor to the secondary sound source is, the greater the environmental noise will be. When the error sensor is too close to the secondary sound source, test results show that, due to the physical characteristics of the hardware equipment, the error sensor is greatly affected by the secondary sound and the spatial coupling noise of the secondary sound and the transformer noise cannot be collected accurately. Based on the above factors, this experiment will be the primary sensor layout to the safety permit required minimum distance, distance transformer 0.2 m; the distance between the error sensor to the secondary sound source is 2.5 m; the secondary sound source cloth from the primary sensor 1.7 m, for the 1.7 m secondary sound channel. It is necessary to make the corresponding phase compensation in the frequency output signal of the adaptive tracking algorithm. The layout of the electro-acoustic device and the distribution of the measuring points are shown in the Figure 10. A measuring point is arranged on the west side of No. 3 transformer to detect the effective noise reduction region of the ANC system prototype. The distance between each measuring point of A1 A10 is 3 m. The distance between each measuring point of B1 B10 is 1 m. The vertical distance between the B column and the secondary source is 3 m. The A column survey points are arranged at the station boundary, and the vertical distance from the secondary sound source is 6 m. The measuring point distribution is shown in Figure 11. The noise reduction experiment site is shown in Figure 12.  
Figure 11: Location diagram of measuring point. Figure 10: Schematic diagram of experimental site. Analyzing Table 2 and Figure 13 show that the noise pressure level is decreased by \(3\pm 0.8\) dB(A) compared to that without applying ANC system when the secondary source faces toward the 0.2 m, i.e., the C1 to C3 position. At the B4 to B6 position, the noise pressure is decreased by \(4\pm 0.8\) dB(A) when the ANC system is not applied. At the C4 to C6 position, the station boundary, the noise pressure ratio decreased by \(7\pm 0.3\) dB(A) without ANC system on. In the four positions of B3, B7, A3, and A7, it is observed that the noise ratio increases with the increase of 1 dB(A) to 1.5 dB(A) when the ANC system is not applied, and there is no obvious change at other measuring points after the application of ANC system.