# High Voltage Engineering Questions and Answers – Testing of Bushings

This set of High Voltage Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Testing of Bushings”.

1. __________ is defined as the voltage which produces the loss of dielectric strength of an insulation.
a) Disruptive Discharge Voltage
b) Withstand voltage
c) Impulse voltage
d) AC test voltage

Explanation: Disruptive Discharge Voltage is defined as the voltage which produces the loss of dielectric strength of the insulation. At this voltage, the electrical stress in the insulation causes a failure such as the collapse of voltage and passage of current.

2. __________ is the voltage which has to be applied to the test object in a withstand test.
a) Disruptive Discharge Voltage
b) Withstand voltage
c) Impulse voltage
d) AC test voltage

Explanation: Withstand voltage is the voltage which has to be applied to the test object in a withstand test. They are applied under specified conditions.

3. In power-factor voltage test, bushing is immersed in oil.
a) True
b) False

Explanation: In power-factor voltage test, bushing is immersed in oil. The tank or earth portion goes to the detector side and the line-conductor goes to the high voltage side. This is a normal routine test.

4. __________ finds the deterioration or failure due to internal discharges caused in the insulation of bushing.
a) Power-factor voltage test
b) Internal or Partial Discharge test
c) Visible Discharge test
d) Momentary withstand test

Explanation: Internal or Partial Discharge test finds the deterioration or failure due to internal discharges caused in the insulation of bushing. The test is done by using an internal or partial discharge arrangement. Nowadays, this test is a routine test for high-voltage bushings.

5. In full wave withstand test, the bushing is tested for only negative polarity.
a) True
b) False

Explanation: In full wave withstand test, the bushing is tested for either polarity. Here five consecutive full waves of standard waveform are applied. The bushing is said to have failed in the test, if two of them cause flashover.

6. Chopped wave withstand test is done for __________ bushings.
a) very-low voltage
b) low voltage
c) high voltage
d) very-high voltage

Explanation: Chopped wave withstand test is done for high voltage bushings. It is a type of impulse voltage test. The tests are conducted similar to full-wave withstand test.

7. In power-factor voltage test __________ is/are recorded as the voltage is applied.
a) capacitance
b) resistance
c) power-factor
d) capacitance and power-factor

Explanation: In power-factor voltage test, capacitance and power-factor are recorded as the voltage is applied. In power-factor voltage test, bushing is immersed in oil. The tank or earth portion goes to the detector side and the line-conductor goes to the high voltage side. This is the most routine test.

8. The temperature rise test is carried out at __________
a) 25Hz
b) 50Hz
c) 75Hz
d) 100Hz

Explanation: The temperature rise test is carried out at 50Hz and at ambient temperature. This ensures that the bushing does not have any excessive temperature rise. It also tests for thermal runway condition.

9. The test related to radio interference is known as __________
a) Power-factor voltage test
b) Internal or Partial Discharge test
c) Visible Discharge test
d) Momentary withstand test

Explanation: The test related to radio interference is known as the Visible Discharge test. This test is conducted in a dark room. No discharge other than that from arcing horns or grading rings is visible to the observer while the conduction of this test.

10. What is the rating of large high-voltage bushings?
a) 1000A, 200kV
b) 1600A, 200kV
c) 1000A, 400kV
d) 1600A, 400kV

Explanation: The rating of large high-voltage bushings is usually 1600A, 400KV. They are usually transformer bushings. Usually, thermal stability tests are the routine tests carried out in large high-voltage bushings.

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