The two significant tests in deciding the health status of transformer oil and paper insulations are. By. MULTI-ATTRIBUTES BASED HEALTH ASSESSMENT.
RESEARCH PAPERS
MULTI-ATTRIBUTES BASED HEALTH ASSESSMENT OF POWER TRANSFORMERS By CHILAKA RANGA *
ASHWANI KUMAR CHANDEL **
RAJEEVAN CHANDEL ***
* Ph.D Scholar, Department of Electrical Engineering, NIT, Hamirpur, HP, India. ** Professor and Head, Department of Electrical Engineering, NIT, Hamirpur, HP, India. *** Professor, Department of Electronics and Communication Engineering, NIT, Hamirpur, HP, India.
ABSTRACT Condition monitoring of power transformers improves the reliability and the safety of an electrical power system. It protects the transformers from fire hazards, and avoids a huge revenue loss to the utilities. The health status of transformers is decided by their several influencing factors. An accurate health assessment of transformers based on various influencing factors has been a challenging task for the researchers as well as the diagnostic experts. In the present paper, a new multi-criterion technique for assessing the health condition of the transformers has been proposed. The main aspects of transformers have been taken into consideration in evaluating their present health status. The overall outcome of the proposed model depends upon all considered attributes as a whole, but not on any single attribute. Hence the proposed approach determines the more reliable and accurate health condition of transformers. It removes the over influence of the attributes in an exact decision making. It also overcomes the shortcomings of the conventional health assessment methods of transformers. Final calculated factors imply what kind of action needs to be implemented for optimal performance and life extension of the transformers. Keywords: Transformer, Attribute, Health, Condition Monitoring, Multi-Criteria, Insulation. INTRODUCTION
DGA and DP respectively. Incredible DGA determines the
Transformer is an important component of electricity
health condition of transformer oil based on total
transmission, and the most valuable device in a
dissolved combustible gasses, and identifies the incipient
substation. Various failures of transformer slow down its
faults present within the transformers [4]. Similarly, degree
age. The transformer abbreviates its life than its expected
of polymerization of transformer solid insulation decides its
life which contributes a huge revenue loss not only to
present health status [5]. This is a measure of the insulating
utilities but also to customers [1]. Therefore, the frequent
paper quality (mechanical strength) and hence an
health assessment of transformers has gained an
indicator of the consumed lifetime of a transformer.
immense importance in recent days. From the literature, it
During the past few years, several methods based on fuzzy
has been found that the health assessment of
logics, neural networks and genetic algorithms have been
transformers mainly depends on the information
developed by the researchers to incorporate the various
extracted from solid and liquid insulations [2-3]. Several
diagnostic test results [6-9]. These methods have their own
diagnostic tests including Dissolved Gas Analysis (DGA),
importance in determining the overall health condition of
Degree of Polymerization (DP), Furfural Analysis (FA), Break
transformers. However, none of these models consider the
Down Voltage (BDV), Interfacial Tension (IFT), and Flash
impact of all factors which influence the health of the
Point (FLP) tests have been conducted to analyze the
transformers [9]. This is due to the reason that more
behaviour of the solid and the liquid insulations inside the
number of inputs increase the complexity in these
transformers [4]. The two significant tests in deciding the
methods. Also the large number of inputs in these
health status of transformer oil and paper insulations are
methods reduce the accuracy of the output [3, 5]. Consequently, there is a need for a new approach which
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i-manager’s Journal on Power Systems Engineering, Vol. 4 l No. 3 l August - October 2016
RESEARCH PAPERS incorporates the impact of all influencing factors of
independently [14, 15]. These threshold scores as per IEEE
transformers in determining an accurate and reliable
guidelines provide a basic criterion for choosing possible
overall health index. This task has been accomplished in
condition based on the score provided for each of the
the present paper. In the present work, a multi-criterion
component or attributes of the transformer as seen in
based methodology for finding the condition of power
Table 1. Comparing these to the framed criteria helps to
transformers has been proposed. The paper has been
make a decision regarding the possible condition of the
organized as follows: Section 1 explains the different
transformer. Tables 2 and 3 depict the major influential
Attributes of Transforms, section 2 describes the proposed
sub-attributes of transformer windings.
multi-criterion methodology; mathematical modeling is
1.1 Design and Fabrication (Type of Winding)
given in section 3. In section 4, case-studies with discussions are presented. Finally conclusions are drawn in section 5.
The choice of the type of winding is largely determined by the rating of the winding. Some common types of windings viz. interleaved disc winding, continuous disc
1. Attributes of Transformer
winding, helical winding, etc. used in transformers are
The whole transformer assembly is fractioned into four
described in [16,17]. Interleaved disc winding is best
major attributes such as winding, core, oil and external
suitable for voltage more than 132 kV as per IEC: 60317.
factors. A total of sixty-eight sub-attributes which influence
The score or weightage for this type of winding is given as
the health of the transformers have been identified. All
zero in Table 2. Otherwise a score between 1 to 3 is
these sub-attributes have been determined based on the
assigned for another type of windings. Continuous disc
information corresponding to design and fabrication,
winding is used for voltage between 33 kV, and 132 kV and
failures, maintenance history, visual inspection, electrical
medium current ratings [18-20]. If the voltage is between
tests and measurements done for each component [10,
33 kV, and 132 kV and the winding is continuous, then a
11]. Each sub-attribute considered in the present work
weight of zero is given, otherwise assign a score between
affects the health of the transformers directly or indirectly.
1 to 3 depending on the condition of the winding. The best
Information regarding design and fabrication of each
selection of winding corresponds to particular voltage
component is provided by the manufacturer.
having lower weightage in the analysis.
Maintenance and operation history give information
1.2 Maintenance and Operation History (Winding Age)
regarding major failures and repairs of every component. Visual inspection of each component with a set of guidelines gives perceptible data. Electrical tests and measurements are to evaluate and state the condition of each component. Test data have the major role in the analysis of the transformer health condition. All these subattributes have been combined by appropriate weights based on their present status. The description of some of the sub-attributes are given below. After computing all attribute and sub-attribute weights related to the health, the final decision can then be taken. This may be whether it is necessary to send the test transformer for refurbishment or its normal operation is continued [12, 13]. The possible conditions of transformer which are the outcomes of multi-criterion analysis are based on the threshold score for each component
Liquid-immersed power transformers have an insulation system made up of natural cellulose based materials and mineral oil. Transformers insulation is always subjected to stresses such as thermal, electrical, or their combinations [21, 22]. These stresses act as a promoter of the chemical reactions and affect the electrical, chemical and mechanical properties of the insulation [23]. Thermal stress on the insulation system may occur due to discharges, dielectric heating, operation in a high Attribute
Different Health Conditions of Transformers Excellent Good Poor
Worst
Winding
(0-35)
(35-60)
(60-85)
>85
Core
(0-35)
(35-60)
(60-85)
>85
Oil
(0-35)
(35-60)
(60-85)
>85
Other factors
(0-25)
(25-50)
(50-75)
>75
Table 1. Weighted Percentage of Attributes as per IEEE Guidelines [12]
i-manager’s Journal on Power Systems Engineering, Vol. 4 l No. 3 l August - October 2016
29
RESEARCH PAPERS temperature environment, Joule heating (I2R losses), and
less than 10 years, then zero weighting is assigned to the
iron losses [24-26]. All these stresses age the transformer
sub-attribute because of its best operating conditions or
windings rapidly. However, in the present work it has been
negligible stresses. This score gradually rises with an
considered that if the age of the transformer windings is
increase in age as shown in Table 2.
Sub-attribute
Score
1
Design and Fabrication
1.A
Tightness of winding 100(rated)
0
(100-80)
3
(80-60)
1.B
1.C
2
1.E
No & type of coil faults None
3
2
5
Outside coil
5
40-60 2
20
Nothing Sub Attribute 2
10 22
Sub Attribute 8 Winding age
35
70
20
A
16
Sub Attribute 9
70
Y
20
Sub Attribute 3 Channel Separator
70
None (0-1)mm
0 1 to 3
Wood
0
(1-3)mm
3 to 5
>3mm
5 to 8
Sub Attribute 10 Displacement of LV
16
Crepe Kraft paper
2
Paper Sub Attribute 4
5 7
2.D
2 2.E
Type of winding
None
0
(0-1)mm
1 to 3
(1-3)mm >3mm
3 to 5 5 to 8
Sub Attribute 11
16
2
Continuous disc winding (33-132)kV with Cu.
0
132kV with Cu./Al.
1 to 3
5%
0o2
0
(5-10) (10-20)
2 to 5 5 to8
>20
8 to 15
1 to 3
Sub Attribute 12
30
Spiral winding (up to 33kV & low current) with Cu./Al.
2.F
Helical Winding
2.G
(low voltage high current) with Cu./Al. Otherwise
0 1 to 3
Sub Attribute 5
3
Winding Bracing & Coil clamping Proper Improper
0 2
2
Sub Attribute 6 Total of Design and Fabrication
2 129
17
20
1
1
1
Water & moisture absorption
>33kV with Cu./Al. (up to 20A) with Cu./Al.
2
Displacement of HV winding
Interleaved Disc winding 0 1 to 3
2
Faults in last 5 - 7 years
Automatic protection
0 2 3
CS-I
0
Connection
(>132kV) with copper made Otherwise.
1.F
Score
Maintenance and operation History
2.A
Class - C with Mixed insulation Class C with Organic insulating materials Class C with Inorganic insulating materials
1.D
Sub-attribute
CS-I
1
Tertiary winding rating None Less than or equal to 1/3 rd of main rating
0 1
Otherwise
2
Sub Attribute 13
3
Total of Attribute Maintenance and operation History
200
0
28
Table 2. Sub-Attributes Corresponding to Design and Fabrication, and Maintenance and Operational History of Transformer Winding
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i-manager’s Journal on Power Systems Engineering, Vol. 4 l No. 3 l August - October 2016
RESEARCH PAPERS 1.3 Visual Inspection (Presence of Dust and Dirt)
could be penetration of the insulation through cracks
Presence of dust and dirt, on the winding and coils
finally leads to short circuit. The transformers which are
contaminates the insulation, thus adversely affect the
afresh and do not have dust problem, such transformers
integrity of the insulation [27, 28]. By operation use, the
are assigned to zero score. In case the thickness of the
winding and coils are exposed to various contaminations.
dust and dirt is between 1 to 5 mm then a score between 1
Degradation of insulation starts from day one of its
to 3 is assigned. In case this value is more than 5 mm then
operation and if proper actions are not initiated, then it
score between 3 to 5 is assigned. Details of the same are
may finally lead to its breakdown [29, 30]. The presence of
given in Tables 2 and 3.
contamination provides a path or medium for currents to
1.4 Tests and Measurements (Temperature Rise Test)
flow on the surface of the insulation, which results in the
A current passing through a wire increases its temperature.
reduction of insulation properties. The worst condition
Similarly, when the transformer is loaded to full load, the
Sub-attribute 3 3.A
3.B
Score
Sub-attribute
Evaluation (CS-I)
Score
Visual Inspection Presence of dust & Dirt
4.E
PD Test
Negligible
0
No PD loss
0
5mm
3 to 5
>20
6 to 10
Sub Attribute 14
9
Sub Attribute 20
19
4
Partial Discharge white powder
4.F
None Low Medium High
0 0 to 2 2 to 4 4 to 7
Sub Attribute 15
13
Total of Visual Inspection
22
6
0% +5% +10% 15%
0 1 to 2 2 to 5 5 to 9
>15%
9 to 15
Sub Attribute 21 Temp. Rise test
31
4
Tests and Measurements
Class F; Class B;
4.A
Turns ratio test
90 Deg. C; > 90 Deg. C
15
Sub Attribute 22
26
0 2 to 5 >0.5%
0 to 2 2 to 5
Sub Attribute 16
7
Winding resistance test 100%
0
(80-100)% 6n
3 6
8n
8 Sub attribute17
4.C
4.D
2
4.H 3
17
Zero sequence impedance
4.I 2
0.001-0.002 0.002-0.003
0 to 2 3 to 5
>0.003
6 to 8
Sub Attribute 23
15
0 to 2 2 to 5
95-100
1
>0.003 Sub Attribute 18
5 to 8 15
90-95 80-85
1 to 3 3 to 5
Rated value
65-80
5 to 7
Dielectric loss 0 1 to 5
4
14
2
Break down strength
0.002-0.003
(100-110)
8
Dissipation factor
0.001-0.002
0
4
Insulation Resistance
2
4.G
4.B
Evaluation (CS-I)
0
125
10 to15 20
Total of Attribute G1
549
92
Sub Attribute 19
50
Table 3. Sub-Attributes Corresponding to Visual Inspection and Tests and Measurements of Transformer Winding
i-manager’s Journal on Power Systems Engineering, Vol. 4 l No. 3 l August - October 2016
31
RESEARCH PAPERS rated current flows through the windings and as a result,
Total of Attribute G 4 = Sub - Attribute (m ) (4) å m= 51,....,68
heat is produced based on the value of current. The insulation system of the windings has particular thermal capacity. A higher temperature could break the insulation between the windings, thus producing more heat due to higher short-circuit current [31]. The temperature rise test is performed at full load either with thermocouple (TC) embedded inside the windings or with resistance
Total (G) = Gj å
(5)
j= 1,..4
where,
G1 indicates transformer winding; G2 indicates transformer core; G3 indicates transformer oil; G4 indicates mechanical components and external factors of the transformer.
measurement of winding. The maximum thermal
Weightage of Gi is defined as Wi which is calculated using
capacity of insulating material depends on its class as
(6) and the data provided in Table 1.
standardized by NEMA MG as shown in Table 3. The scores for different temperatures of various windings are
(Sum of scores of all sub - attributes of attribute ' i ') (6) Wi = (Sum of max scores of all attributes) å
assigned as given in Table 3. Health assessment of
where,
transformer through multi-criterion analysis majorly depends on its various test results. The different test results of two test transformers along with their corresponding assigned weights are given in Table 4. Figure 1 details all the sub-sttributes of the transformers along with their final
i= 1,..4
W1 denotes weightage of transformer winding; W2 denotes weightage of transformer core; W3 denotes weight age of oil; W4 denotes weight age of mechanical components and external factors in the analysis. The relative importance of the possible condition Xi with
weights given in open bands.
respect to attribute Gj is given by weightage Xij as per the
2. The Proposed Multi-Attribute Methodology
IEEE guidelines [6].
Let Xi be the set of possible condition of the transformer X ={Xi; i = 1,2,3,4}. where, X1 indicates that the condition of the transformer is excellent and a routine maintenance is an option. X2 indicates that the condition of the transformer is either good or average and a routine maintenance is an option along with a constant and careful supervision. X3 indicates
Xi (threshhold score) of possible condition Xij = Gj,max
Values of Xij for ith possible condition with respect to jth goal or attribute. Zij gives the range for each possible condition with respect to weightage of the goal. Zij is computed by using (8). Zij = Xij ´ Wi
that the condition of the transformer is poor and refurbishment is an option for reliable operation. X4 to bring the transformer back to service refurbishment is
(8)
Xi is then computed using equation (9). 4
indicates that the condition of the transformer is worst and an option.
(7)
Xi = Zij å
(9)
j= 1
3. Results and Discussions The proposed methodology is a generalized one, and has
Let's consider the attributes of the transformer are
been tested on a number of test cases. However, in the
denoted by a set G, where G ={Gj; j = 1,2,3,4}.
present work test results of two cases have been
According to the guidelines a total of each attribute
presented.
based on scoring is calculated according to equations [1]-[5]. Total of Attribute G1 = Sub - Attribute (m ) å
(1)
Total of Attribu te G2 = Sub - Attribute (m ) å
(2)
Total of Attribute G3 = Sub - Attribute( m) å m= 37,....,50
32
It is a 132/33 kV, 25 MVA transformer owned by Himachal Pradesh power utility and installed at its substation at
m= 1,....,24
m= 25,....,36
3.1 Case Study-I: 132/33 kV ANU Substation
Hamirpur, Himachal Pradesh. This transformer has been in operation since 9th June 2007. Multi-criterion has been
(3)
used to determine the overall health condition of this
i-manager’s Journal on Power Systems Engineering, Vol. 4 l No. 3 l August - October 2016
RESEARCH PAPERS S.No.
Parameter/Sub-Attribute
1 1.A
Transformer Winding Turns ratio test
Weight age
(0-0.1)%
1.B
1.C
1.D
0 to 2
>0.5% Sub Attribute T1
2 to 5 7
100%
0
(80-100)%
3n
60-80) 20
3 to 6 6 to 10
1.F
Insulation Resistance
1.G
0% +5% +10% 15% >15% Sub Attribute T6 Temp. rise test Class F; Class B; 90 Deg. C; > 90 Deg. C Sub Attribute T7
7 to 15 15 26
0 to 2 2 to 5 5 to 8
Sub Attribute T8 Breakdown strength
15
Rated value 95-100
0 1
90-95 80-85 65-80 0.003
5
0 2
0 1 to 3 3 to 7
Sub Attribute T10 Magnetic saturation test
53
3.C
40 to 60 Deg, C; 35 to 45 Deg. C 60 to 80 Deg, C, 45 to 55 Deg. C
5
Air gap test Without air gap Low
2
19
0
Imbalance
20
3
20 50
Without imbalance
(80-100)% 2.C
4
Weight age (11/0.433kV)
Sub Attribute T11
Zero sequence impedance
Sub Attribute T5
1.I
Parameter/Sub-Attribute
2 2.A
Winding resistance test
>125 Sub Attribute T4
1.H
S.No.
0
(0.1-0.5)%
0 (100-110)
1.E
(11/0.433kV) (132/33 kV)
0
5
0
1
2
0 to 2 0 to 2 0 to 2 0 to 2 0 to 2 0 to 2 0 to 2 14 3 to 6
C2H6 101 - 150 H2 701 - 1800
3 to 6 3 to 6
CH4 401 - 1000 C2H2 51 - 80 CO 571 - 1400
3 to 6 3 to 6 3 to 6
CO2 4001 - 10000 Sub Attribute T15
3 to 6 28
14
28
7 7
H2 CH4
>1800 >1000
7 7
C2H2 CO
>80 >1400
7 7
CO2 >10000 Sub Attribute T16
0
0 0
Advise maintenance C2H4 101 - 200
Removal from service C2H4 >200 C2H6 >150
(132/33 kV)
7 49
2
Table 4. Sub-Attributes Corresponding to Different Tests and Measurements, and Evaluation of two Test Transformers
i-manager’s Journal on Power Systems Engineering, Vol. 4 l No. 3 l August - October 2016
33
RESEARCH PAPERS
Figure 1. Block Diagram Representation of Transformer Attributes and Sub-Attributes along with Their Weigths
transformer. Scores of all main attributes and sub-
continuous disc winding is best suitable for this specified
attributes of this transformer are as given in column 3 of
rating of transformers. Therefore, a score between 0 to 3, i.e.
Table 5.
2 is assigned to the related sub-attribute. As the age of the
As per the collected data from substation, interleaved disc
transformer is less than 10 years, which is almost 7 years and
winding is used in this transformer. According to the criterion,
4 months, a score 1 is assigned to the corresponding sub-
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i-manager’s Journal on Power Systems Engineering, Vol. 4 l No. 3 l August - October 2016
RESEARCH PAPERS S.No
Attributes
Received weightage/ score (Case Study-I)
Received weightage/ score (Case Study-II)
1
Transformer winding (G1) Design and Fabrication (G1)
17
13
Maintenance and operation History
28
29
Visual Inspection
6
6
Tests
41
26
Total of Attribute (G1) Transformer core (G2)
92
74
2
Design and Fabrication
4
6
Maintenance and operation History
1
13
Visual Inspection
4
4
Tests Total of Attribute (G2)
1 10
23 46
3
Transformer oil (G3)
4
Design and Fabrication
7
9
Maintenance and operation History
5
15
Visual Inspection Tests
12 28
20 28
Total of Attribute (G3)
52
72
Mechanical components and External Factors (G4)
24
50
Table 5. Multi-Criterion Based Condition Evaluation of Transformer
attribute as per Table 3. From visual inspection at the site it is
attributes of the transformer is computed by using (6) and is
found that the thickness of dust and dirt is about 5 mm.
given in Figure 2.
Therefore, a score 5 is assigned to the related sub-attribute.
Based on computed weights of all attributes, a threshold
Subsequently, scores for remaining attributes and sub-
score is fixed for each decision according to the criterion
attributes are evaluated according to Tables 2 and 3. The
laid in Table 1. Further values of Xij for ith possible conditions
analysis of each component or attribute has been done
with respect to jth goal are as given in Table 6.
separately to know the condition of each component. The weighting of each attribute with respect to all other
In Table 7, range for the decision criterion is calculated based on the relative weighting of attribute with respect to possible conditions. Obtained weights (Wi) of this test case 1 are 0.516853933, 0.056179775, 0.292134831, and 0.134831461. These weights compare with the calculated range of different possible conditions, viz. excellent, good, poor, and worst as given in Table 7. It is Xij
G1
G2
G3
G4
X1
0.460526
3.5
0.673077
0.208333
X2
0.789474
6
1.153846
2.083333
X3
1.118421
8.5
1.634615
3.125
X4
>1.118421
>8.5
>1.634615
>3.125
Table 6. Weightage of Possible Condition w.r.t. Attributes
Figure 2. Final Received Weights of Both the Case-Studies Attributes Decision Possible Conditions
G1
G2
G3
Excellent
0.238025
0.196629
0.196629
0.02809
(0-0.659373)
Good Poor Worst
0.408043 0.57806 >0.57806
0.337079 0.477528 >0.477528
0.337079 0.477528 >0.477528
0.280899 0.421348 >0.421348
(0.659373-1.363099) (1.363099-1.954465) >1.954465
G4
Range of Possible Conditions
Table 7. The Range of Possible Conditions w.r.t. Attributes
i-manager’s Journal on Power Systems Engineering, Vol. 4 l No. 3 l August - October 2016
35
RESEARCH PAPERS found that all weights are lying in its excellent condition range. Therefore, Routine maintenance of transformer is an option for utility managers. 3.2 Case study-II: 11/0.433 kV NIT Hamirpur Substation Case study-II is carried on 11/0.433 kV, 630 kVA transformer. This is a distribution transformer and is owned by an educational institute. The transformer under study is in continuous operation since 23rd August 1995. In-depth visual and test studies are carried out on the transformer under study. Based on these scores, main and subattributes are assigned. Various scores assigned to this case are as given in column 4 of Table 5. The possible conditions of the transformer and the threshold scores corresponding to the possible conditions are given in Table 1. The values of Xij for ith possible conditions with respect to jth goal are given in Table 8.
Figure 3. Final Possible Ranges for all Attributes of the Transformers
conditions. The overall outcome of evaluation does not depend on just any single attribute. This would possibly remove the over influence of any one attribute for decision making.
Relative weightings of the possible conditions with respect
The proposed methodology analyzes the input evaluation
to the weightings of attributes are given in the Table 9. As
of both case-studies and compares it with the numerical
shown in Figure 2, obtained weights (Wi) of test case 2 are
range of the possible conditions. Finally, transformer’s
0.305785124, 0.190082645, 0.297520661, and
present condition is computed as one of the possible four
0.20661157. After comparison of these weights with the
conditions.
obtained range of different four possible conditions, viz. excellent, good, poor, worst as given in Table 9, it has been found that all weights of this test case transformer lying in its excellent condition range. Therefore, an expert can take a decision about the transformer as Routine maintenance with a careful and frequent supervision. In Figure 3, the range for the decision criterion of two different case-studies is given based on the relative weighting of attribute with respect to the possible Xij
G1
G2
G3
G4
X1
0.472973
0.76087
0.486111
0.5
Conclusion Multi-criterion technique for assessing the accurate health condition of power and distribution transformers has been proposed in this work. Four main attributes and sixty eight sub-attributes have been identified for correctly determining the condition of the transformers. All these attributes are assigned with some weight, which is done based on expertise and the test results. Judiciously selected threshold value helps in segregating different conditions of the transformers. Depending upon the
X2
0.810811
1.304348
0.833333
1
scores earned by the various attributes or components of
X3
1.148649
1.847826
1.180556
1.5
transformers and based upon the threshold scores, the
X4
>1.148649
>1.847826
>1.180556
>1.5
Table 8. Weightage of Possible Condition w.r.t. Attributes
four conditions, viz. excellent, good, poor, and worst can be identified. The proposed technique is pragmatic and
Attributes Decision Possible Conditions
G1
G2
G3
G4
Range of Possible Condition
Excellent
0.144628
0.14462
0.14462
0.10330
0.53719
conventional health assessment methods of transformers
Good
0.247934
0.247934
0.2479
0.20661
0.950413
Poor
0.35124
0.35124
0.3512
0.30991
1.363636
including fuzzy logic and neural networks.
Worst
>0.35124
>0.35124
>0.3512 >0.30991 >1.363636
Table 9. Ratings of Possible Condition w.r.t. Attribute
36
can be easily utilized for the evaluation of the condition of the transformers. It overcomes the shortcomings of
Acknowledgement The authors would like to thank the authorities of TEQIP–II of
i-manager’s Journal on Power Systems Engineering, Vol. 4 l No. 3 l August - October 2016
RESEARCH PAPERS NIT Hamirpur India for providing the financial support with
Indian Journal of Power and River Valley Development.
grant number NIT/HMR/TEQIP–II/Research & Develpoment
Vol.2, pp.143-147.
–19/2015/2157–63. They are also thankful to the Himachal
[10]. Milan, Z. (1975). Multiple Criterion Decision Making.
Pradesh State Electricity Board (HPSEB)–India for providing
Tata McGraw-Hill: Delhi.
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ABOUT THE AUTHORS Chilaka Ranga (S'16) is received his B. Tech. Degree in Electrical and Electronics Engineering from Bapatla Engineering College, Bapatla (Ap), India in 2010. He received his M.Tech. Degree from National Institute of Technology, Hamirpur (HP), India, in 2012. Presently he is pursuing his Ph.D. from Department of Electrical Engineering, National Institute of Technology, Hamirpur (HP). His areas of interest are Performance Evaluation and Health Assessment of Power Transformers.
Ashwani Kumar Chandel (S'05–M'15) is received his Ph.D. Degree from Indian Institute of Technology Roorkee, India in 2005. He joined the Department of Electrical Engineering, National Institute of Technology, Hamirpur, HP, India, as Lecturer in 1991, where presently he is working as a Professor. His research areas are Harmonic Estimation and Elimination, Condition Monitoring of Transformers. He is a Fellow of IETE, Member IEEE and Life Member of ISTE
Rajeevan Chandel (S'05–M'15) is received her M.Tech. Degree in Integrated Electronics from IIT Delhi, India, in 1997 and Ph.D. Degree from IIT Roorkee in 2005. She joined as a Lecturer in E&CED, NIT Hamirpur in 1990, where she is currently a Professor and is Dean (R&C). She has five sponsored projects to her credit and over 50 research papers in journals of repute. Her research interests include Electronics Circuit Modeling and Low-Power Design. She is a Fellow of IETE (I), Life Member of ISTE (I) and Member IEEE.
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