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1. Electrical power engineering
test (2(
Elect.Eng/ Mohamed Safwat

2. Q1) 1a-What are abbreviations referring to?
1- UPS
2- ONAN
3- BDV
1-UPS: Uninterruptible Power Supply
Is used in very important loads.
2-ONAN: Oil Natural Air Natural
is a type of cooling used in oil transformers up to (30 MVA(.
3-BDV: Break Down Voltage
Break down voltage of any isolation material like [ oil , pvc , ……,etc[
This value the voltage of any system can’t be over it , may be [33 KV or 66 KV[

3. Q2) What is meant by derating factor = 0.65
This mean that if we have cable withstand 100 A in normal condition so if we take
derating factor 0.65 the maximum withstanding current will be 65 A so we lost
35A

4. Q3) what is the function of Synchrocheck relay?
Is used in case of parallel connection
between two generators to feed large load
to adapt the synchronization

5. Q4)What are the conditions of parallel connection
between transformers?
1-The voltage ratio must be the same.
2-The per-unit impedence must be the same.
3-The polarity connection must be the same I order to
avoid circulating current.

6. Q5) what are the suitable method to start induction motor ,
explain with drawings?
1-Rotor resistance method (only for wound rotor).
2-Stator resistor or reactance.
3-Auto transformer method.
4-Star-Delta Switch.
5-Soft starting method.
The best method is:
1-Soft starting method.
2-Star delta switch.

7. 1-Soft starting method.

8. 2-Star delta switch.

9. Q6) what are the excitation system types for synchronous
generators , explain with drawings?
1-Dc excitation system using amplidyne

10. 2-Ac excitation system
a- using rectifier

11. b- using brushless

12. 3-using static excitation method

13. Q7) draw the schematic drawing for ups system and
identify each component of it
ups

14. Q8)what are the precaution required to change the CT
burden during energized system?
Never open circuit a current transformer
secondary while the primary is energized

15. Q9) draw the differential protection circuit install on motor
and identify its parameters and draw C/C curve of it?

16. Q10)Three pumps working sequentially after delayed for
some time in start one after one with motor rated power
= 55 KW and rated voltage = 400V and rated power
factor = 0.85 lag please draw the power and control
circuit for it and determine all circuit components
parameters that you use it