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le 3: Comparison of Tan-Delta value between Factory Measured HV+IV/ TER/ HV+IV/ TER/
Acceptance Test & Site Acceptance Test (contd.) between TER+E HV+IV+E TER+E HV+IV+E
(FAT) (SAT)
Test Measured Voltage Tan Delta Tan Delta 600 Sec. 5550 (FAT) 21100 (SAT)
Mode Between (kV) (%) in FAT (%) in SAT PI Ratio 13000 42900
2.03 1.8
GST HV+IV/TER+E 10 0.208 0.218 3.35 3.04
GSTg TER/E 5 0.217 0.233
GSTg TER/E 10 0.220 0.226 CONCLUSION
GST TER/HV+IV+E 5 0.182 0.194
GST TER/HV+IV+E 10 0.183 0.170 After completing all other necessary jobs, the Transformer
was successfully commissioned on 10th December,
Figure 5: Tan delta vs moisture (%) for a new and 2021, well within stipulated timeline. Effective adoption
service-aged typical transformer of “Vacuum – Dry-Air Purging Cycle” accompanied by
intricate monitoring of Dew Point & Relative Humidity of
A tan delta/power factor measurement is a measure of active part of the Transformer inside the main tank have
the combined losses in oil and cellulose. It is known that made it possible in spite of the extremely moist inclement
the measurement cannot discriminate a dry transformer atmospheric condition at the time of installation.
with service aged oil from a wet transformer with new oil.
Solid Insulation is generally iinsensitive to moisture ACKNOWLEDGEMENT
levels < 2.5% as noted in Figure 5, which describes the
relationship between line frequency tan delta values We sincerely thanks to Mr. Sujit Pathak, Mr. Bratin Banerjee,
and moisture levels for a new and service-aged typical Mr. Subrata Panja & Mr. Soumya Tirtha Bhattacharya,
transformer. CESC Limited for their continuous support and
valuable suggestions. In addition, the authors gratefully
Table 4: Comparison of IR & PI value between Factory acknowledge the manufacturer for their continuous
Acceptance Test & Site Acceptance Test support throughout the process implementation and
successful commissioning of the transformer.
Measured HV+IV/ TER/ HV+IV/ TER/
between TER+E HV+IV+E TER+E HV+IV+E REFERENCES
(FAT) (SAT)
(FAT) (SAT) [1] IEEE Std. C57.93™-2007: IEEE Guideline for Maintenance
& Installation of Liquid-Immersed transformer
Voltage 5000 5000 5000 5000
60 Sec. 2740 3880 11750 14100 [2] IS 10028 (Part II): CODE OF PRACTICE FOR
SELECTION, INSTALLATION AND MAINTENANCE OF
TRANSFORMERS
[3] CBIP (Publication No. 317): Manual on Transformers
[4] IEEMA: Manual on Installation of Transformer
[5] Megger: Transformer Life Management Bulletin
(Moisture in Transformer)
[6] NASA Technical Note (NASA TN D-8401): Equation
for The Determination of Humidity from Dew Point &
Psychometric Data
44
Acceptance Test & Site Acceptance Test (contd.) between TER+E HV+IV+E TER+E HV+IV+E
(FAT) (SAT)
Test Measured Voltage Tan Delta Tan Delta 600 Sec. 5550 (FAT) 21100 (SAT)
Mode Between (kV) (%) in FAT (%) in SAT PI Ratio 13000 42900
2.03 1.8
GST HV+IV/TER+E 10 0.208 0.218 3.35 3.04
GSTg TER/E 5 0.217 0.233
GSTg TER/E 10 0.220 0.226 CONCLUSION
GST TER/HV+IV+E 5 0.182 0.194
GST TER/HV+IV+E 10 0.183 0.170 After completing all other necessary jobs, the Transformer
was successfully commissioned on 10th December,
Figure 5: Tan delta vs moisture (%) for a new and 2021, well within stipulated timeline. Effective adoption
service-aged typical transformer of “Vacuum – Dry-Air Purging Cycle” accompanied by
intricate monitoring of Dew Point & Relative Humidity of
A tan delta/power factor measurement is a measure of active part of the Transformer inside the main tank have
the combined losses in oil and cellulose. It is known that made it possible in spite of the extremely moist inclement
the measurement cannot discriminate a dry transformer atmospheric condition at the time of installation.
with service aged oil from a wet transformer with new oil.
Solid Insulation is generally iinsensitive to moisture ACKNOWLEDGEMENT
levels < 2.5% as noted in Figure 5, which describes the
relationship between line frequency tan delta values We sincerely thanks to Mr. Sujit Pathak, Mr. Bratin Banerjee,
and moisture levels for a new and service-aged typical Mr. Subrata Panja & Mr. Soumya Tirtha Bhattacharya,
transformer. CESC Limited for their continuous support and
valuable suggestions. In addition, the authors gratefully
Table 4: Comparison of IR & PI value between Factory acknowledge the manufacturer for their continuous
Acceptance Test & Site Acceptance Test support throughout the process implementation and
successful commissioning of the transformer.
Measured HV+IV/ TER/ HV+IV/ TER/
between TER+E HV+IV+E TER+E HV+IV+E REFERENCES
(FAT) (SAT)
(FAT) (SAT) [1] IEEE Std. C57.93™-2007: IEEE Guideline for Maintenance
& Installation of Liquid-Immersed transformer
Voltage 5000 5000 5000 5000
60 Sec. 2740 3880 11750 14100 [2] IS 10028 (Part II): CODE OF PRACTICE FOR
SELECTION, INSTALLATION AND MAINTENANCE OF
TRANSFORMERS
[3] CBIP (Publication No. 317): Manual on Transformers
[4] IEEMA: Manual on Installation of Transformer
[5] Megger: Transformer Life Management Bulletin
(Moisture in Transformer)
[6] NASA Technical Note (NASA TN D-8401): Equation
for The Determination of Humidity from Dew Point &
Psychometric Data
44
