EE1402(Unit V)

Unit V


1. Define type test.
They are intended to prove or check the design features and the quality. They are done
on samples when new designs or design changes are introduced.

2. Define routine test.
They are intended to check the quality of an individual test piece. They are done to
ensure the reliability of an individual test object and quality and consistency of materials
used in their manufacture.

3. Define withstand test voltage.
The voltage which has to be applied to a test object under specified conditions in a
Withstand test is called withstand voltage.

4. Define flashover voltage.
The voltage that causes a flashover at each of its applications under specified conditions
when applied to test objects as specified is called flashover voltage.

5. Name the tests conducted on surge diverters.
Power frequency spark over test, Hundred percent impulse spark over test, Front of
Wave sparkover test and residual voltage test.
6. Give any two classification of test on cables.
Partial discharge test and impulse withstand voltage test.

7. Explain the porosity test on insulators.
The insulator is broken and immersed in a 0.5 % alcohol solution under a pressure of
13800 KN/sq.m for 24 hours. The broken insulator is taken out and further broken. It
Should not show any sign of impregnation.

8. What is a surge diverter?
It is a non-linear resistor in series with a spark gap kept at line terminals in the
substations.

9. Define creeping distance.
It is the shortest distance on the contour of the external surface of the insulator unit .

10. What is the importance of radio interference voltage measurements for extra high
Voltage power apparatus?
In the power apparatus it produces unwanted electrical signals in radio and high
frequency ranges.It is important to see that the noise generated should be reduced.
For this purpose this measurement is important.

11. Name the test conducted on bushings.
Power frequency test , impulse voltage test and thermal test.


12. Define partial discharge.
An electrical discharge that only partially bridges the dielectric between the
Conductors. Examples are surface discharge, internal discharge

.
13. What is the function of surge arrester?
They are capable of discharging 10 to 20 KA of long duration surges and 100 to
250 KA of short duration surge currents.

14. State the consequences of RIV.
When the noise meter measurements are stated the information regarding the
Specification of meters used in the band pass characteristics and the open circuit the
detector characteristics has to be mentioned.

15. What do you mean by radio interference?
The power apparatus produces unwanted signals in the radio and high frequency
ranges. These are called radio interference.

16. Define an isolator.
It is a disconnector or a mechanical switching device which provides in the open
position an isolating distance in accordance with special requirements.

17. Define a circuit breaker.
It is a switch which automatically interrupts the circuit when a critical current or
voltage rating is exceeded.

18. Define 50% flashover voltage
It is the voltage which has the 50 % flashover when applied to test object.


19. Define 100 % flash over voltage
The voltage that causes a flashover at each of its application under specified conditions
when applied to test objects as specified.

20. State 2 standard tests to be conducted on HV Transformers.
Induced overvoltage test and partial discharge test

21. What does the selection of BIL level for lines depend?
Atmospheric conditions, lightning activity, insulation pollution and acceptable outage of
the line.