This document describes various tests performed on insulators, including: temperature cycle testing; electro-mechanical testing; puncture testing; mechanical routine testing; power factor testing; partial discharge testing; visible discharge testing; impulse withstand testing; chopped wave and switching surge testing; temperature rise testing; and thermal stability testing. The tests are conducted to evaluate insulators' performance under different conditions and ensure high insulation efficiency, long life, and ability to withstand various stresses.

1. Testing of insulators
Contents
• Temperature cycle test
• Electro-mechanical test
• Puncture test
• Mechanical routine test
• Different test
• Power factor test
• Partial discharge test
• Visible discharge test
• Impulse withstand test
• Chopped wave and switching surge test
• Temperature rise test
• Thermal stability test.
• Conclusion and reference
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2. Temperature cycle test
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3. Electro-Mechanical test
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5. Puncture test
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6. Mechanical routine test
• String insulator is suspended vertically
and horizontally and a tensible load 20%
in excess of the maximum specified
working load
• Applied for one minute
• No damage to string
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7. Different test
• Power factor test
• Partial discharge test
• Visible discharge test at power
frequency
• One minute wet Withstand test
• Impulse Withstand test
• Chopped wave and switching surge test
• Temperature rise test
• Thermal stability test
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8. Power factor test
• Bushing is installed as in service or
immersed in oil
• HV voltage terminal of bushing is
connected to high voltage terminal of the
Schering bridge and tank/earth portion of
the bushing is connected to the detector of
the bridge.
• Capacitance and power factor of the
bushing - different voltages as specified –
within the range.
• PF high- eff. High- long life
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9. Partial Discharge Test
• Composite dielectric
• V applied – partial discharges occurred-
due to voids, cracks & imperfections
ONE MINUTE WET WITHSTAND TEST
• Specified voltage is applied (rainy
season)
• Flashover does not occur for one minute
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10. Visible discharge test
• Test under give rise to radio
interference
• In a dark room
• V applied as specified
• No discharge other than that from the
grading rings or arching horns
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11. Impulse withstand test
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12. Chopped wave and switching
surges Test
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13. Temperature rise test
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14. Thermal Stability Test
• Some time the bushing is operated with
the transformer, the temperature may
increase beyond 80 degree C and thermal
run away condition occurs.
• When 86% of the nominal system V is
applied
• This test is conducted for bushing used for
above 132kV.
• In high voltage application , the dielectric
losses are high.
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15. • Conclusion
From this we concluded that varies test
incorporated in insulators.
• Reference
“High voltage engineering ” by M S Naidu and
V Kamaraju, Tata McGraw Hill Education, 5th
edition.
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