Parametric Analysis of External Noise Regression for Reliability Optimization in Transformers

Parametric Analysis of External Noise Regression for Reliability Optimization in Transformers

Mahendra Singh

1. ech Student, Department of Electrical Engg.

   Lingayas University Faridabad,Haryana,India

   Avtar K. Nadir

   Professor & Dean

   Ms.Asha Chauhan

   Asstt.Professor, Department of Electrical Engg.

   Lingayas University

   Faridabad,Haryana,India

   Department of Electrical Engg.

   Lingayas University Faridabad,Haryana,India

   Abstract. In all the generation of Noise Core is the most Significant sources of Noise and generation of noise in this is having adopt different way of generation as per the rating of Transformer. Now a day the design are changed according to the land requirement and area to be minimized. Noise is the progression in the Transformer based on the rating of the Transformer. As the Capacity of the Transformer is increasing the level of the Noise in the Transformer is also increased and it should be adopted as per the recommended value.

   KeywordsNoise,dB,Noise Regression,CRGO.

   1. INTRODUCTION Transformer Noise

      New trends of Transformer [18] design to lead to change the design in such a way that noise to be reduced in such a level where its optimization [1] to be done not only in the Operational aspect but also Location. The new trend put noise [2] to be low for Power Transformer and Distribution Transformer [3]. Transformers located near a residential area are now adopted design for sound level as low as possible.

      Users are now looking for a Transformer having reduced noise [5] level so that their operability as well as reliability to increased. The design and manufacture of a transformer with a reduced sound level require in-depth understanding of different sources of noise. Power Quality will depend on the noise level [10][15]. Transformer is having main sources of noise is

      1. Core

      2. Windings

      3. Auxiliary Equipment

      . Windings is also sources of Noise [6] generation and contributed in the life span of the Transformer. The Third sources of Noise Generation are the Auxiliary Equipment associated with Transformer[17] i.e Cooling Equipment

      like Fans, they are also Huge Sources of Noise[4] generation for the small and medium and Large capacity of Power Transformer..

      Fig 1.Core Material Development with years

      1. Type of Transformer Noise

         The noise generated in Power Transformers is defined by the Three Basic Parameters

         1. Sound Pressure Level Method (Lp)

         2. Sound Power Level Method (Lw)

         3. Sound Intensity Method (Li)

      2. Impact of Transformer Noise on Reliability of Transformer

      External Noise: External noise is mainly contributed by Aerodynamic device and thus it is called Aerodynamic Noise [2]. The Aerodynamic noise is most contributed by the External Cooling Fan Device and a lot of The Noise are generated because of various number of Fans are connected in Series and Parallel Configuration [11]. The Noise generated by these fans mainly depends on the sweep Area of Fan and Speed of Fan and Blade configuration.

      Noise Level [8]is also depend on the cooling method and types of cooling arrangements used for the Transformer .In Transformer Noise level vary according to environmental aspect and Operating condition. [9].

      Transformer Core vibrates due to Magnetic Forces and Magnetostrictive Forces. Most of the Magnetic Forces developed due to non-linear Magnetic gaps at the corner joints of Limbs and yokes.

      In Power Transformer [16] Forces produced by the magnetostriction phenomenon are higher incomparision of magnetic forces in transformers. An alternating field sets the core [17] to vibration. This vibration is transmitted through the oil and tank structure to the surrounding air and creates hum and this coefficient of Magnetostriction is

      given by .

      Where L and L are length of lamination sheet and its change respectively.

      Where E is the modulus of elasticity in the direction of force and A is the cross sectional area of a lamination sheet.

      F=(t)EA

      Fig 2 Magnetostriction Curve

      The change in dimension is not linearly depending to the flux density. Magnetostriction can be positive or negative, depending on the type of the magnetic material, and the mechanical and thermal treatments.

      Magnetic Characteristics in quality of yoke clamping has a significant influence on the noise [14] level. Apart from the yoke flux density, other factors which decide the noise level are:

      1. Limb flux density,

      2. Type of core material,

      3. Leg center

      4. core weight,

      5. frequency

      The noise level is depending on operating peak flux density and core weight. The change in noise level as a function of these two factors can be expressed as:

      If core weight is assumed to change with flux density approximately in inverse Manner, for a flux density change from 1.6 T to 1.7 T, Then increase in noise level is 1.7 dB [64 Log10(1.7/1.6)]. One of the ways of reducing noise is by designing transformer at lower operating flux density and this way reliability is to improve .thus in 0.1T Reduction the noise level to be reduced by 2 dB [9].

      Bonding of laminations by adhesives and placing of anti- vibration and damping elements between the core and tank not only reduced the noise level but also it increases the strength of core [2]. When higher level of noise reduction is required than latest core material to be used and also good quality of Windings material to be used.

      Table- I Development of Core Material

      Year	Core Material
      1910	Warm Rolled FeSi Material
      1950	Cold Rolled (CRGO)
      1960	Cold Rolled (CRGO)
      1965	Cold Rolled (CRGO)
      1975	Amorphous Metal Material
      1980	Cold Rolled (CRGO)
      1985	Cold Rolled(CRGO)
      2000	Advanced Stage Material like Superconducting Alloy

   2. ANALYSIS OF NOISE

      1. Sound Pressure Level Lp=20* Log10 (P/P0) [dB]

         P is the Sound Pressure in Pa and P0 is reference sound Pressure.

      2. Sound Power Level Lw

         Lw= 10* Log10 (W/W0) [dB]

         W is sound Power and W0 is reference sound power.

      3. Sound Intensity level Li Li= 10 log10 (I/I0)

         I is sound Intensity [w/m2] and I0 is reference value of sound intensity.

         the measurement of the noise level is done as per the above equation.

      4. Aerodynamic Noise Reduction

      For Increasing the Capacity of the Transformer cooling fans are provided. By installation of these fans the capacity of the Transformer is increased. Fan dynamic revolution leads to maximum noise generation and also leads to generation hum sound[12]. Thus this type of noise generation is depend on the source of noise [6] generation and its various configuration and they are as below

      1. Revolution of Fan

      2. Sweep of Fan

      Thus the fan revolution is restricted up to certain number of revolution so that the speed can be monitored and regulate. by optimization [13]of speed the Aerodynamic noise is reduced. With having large number of Blades and having large length of the fan Blade the noise level also to be reduced ad leads reducing the noise generation in Aerodynamic mode.

      Thus the Aerodynamic Speed Noise Reduction can be measured as below

      FWA (Fan) = 70 Log10 (D/D0) +50 Log10 (N/N0) +K1+K2

      Where K1=Intrinsic Noise factor Where K2=Environment Impact Factor

      Thus the Noise [14] Reduction may be adapted by the way to adopting the both the configuration with speed and diameter to be low as much as possible. The Optimization of Transformer will be done based on the configuration and type of Configuration used.

      The Reliability of Transformer can be improved in view of reduction of Noise and also by reducing the losses in Transformer are below.

      1. Using More Material

      2. Better Material

      3. New Advanced material

      4. Improved material for LV & MV Voltage Level.

      5. Improving in cooling medium and Reduced Noise level

   3. NOISE RATIO CORRELATION & REGRESSION

      Noise error is generated with respect to the error in the signal transmitted with noise and it is co-related with the factor for synchronizing the error in the ratio of the error in the noise and defined with Diameter of the Fan and speed of the fan for external co-relation of the factor. The diagrammatical analysis of this noise ratio correlation for the transformer was done in the different cases given in the result section.

      Diamter of

      Fan Ratio (D/D0)

      Speed of Fan Ratio (N/N0)

      24.625.6

      22.3

      16.117.9

      40.0

      30.0

      20.0

      1. Noise Optimization: Estimation of Noise Error Case-1:

         60.0

         50.0

         53.3

         1 2 3 4 5

         Fan Ratio

         (D/D0)

         Speed of

         Fan Ratio (N/N0)

         14.0

         23.61

         20.71

         19.4

         17.81

         16.3

         14.92

         20.00

         15.00

         Noise 10.032 1.62 1.82 21.2 21.52 (X)[dB]

         0.0

         14.9

         11.5

         10.5

         10.0

         Fig 3 Noise Error & Speed of Fan Case-2

         30.00

         25.00

         26.51 Diamter of

         10.00

         12.3 Noise

         (X)[dB]

         5.00

         1.51591.53511.54541.551.755

         Noise Error

         in %

         1 2 3 4 5

         0

         0.00

         Fig 4 Noise Error & Speed of Fan

         Case-3 Case-3

         70.00

         60.00

         50.00

         40.00

         62.3

         57.14

         42.74

         36.033.7

         Diamter of Fan Ratio (D/D0)

         Speed of Fan Ratio (N/N0)

         30.00

         20.00

         10.00

         0.00

         2391.842

         24.21

         14.92

         10.51591.7511.87892.403732.247

         1 2 3 4 5

         Noise (X)[dB]

         Noise Error in %

         Case-4

         Fig 8 Noise Correlation & Noise Regression

         Fig 5 Noise Error & Speed of Fan

      2. Noise Optimization: Noise Error, Noise Correlation, Noise Regression

      Case-1

      Fig 9 Noise Correlation & Noise Regression

      Case-2

      Fig 6 Noise Correlation & Noise Regression

      Fig 7 Noise Correlation & Noise Regression

   4. CONCLUSION

External Noise is dynamic Index which is going to change every space of Progression. The External Noise regression and correlation will depend on the Profile of Noise Level and Correlation is spontaneous with moment of noise and thus the Noise Regression is on the Platform is depend of the external causes and by the virtue of external noise.

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