Power System

Interview Questions

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Electrical Engineering Interview Questions (Power System)

Electrical Design Engineering, Hydro Power, Thermal Power Station Questions, Switchyard 220kV/ 400kV/ 765 kV, Substation Questions

1. HTC Interview: (as told by RS)

1. Preparation of DPR, How dimension are made for generator.
2. Favorite BOP item.
3. Ring / Bus topography in SCADA
4. SCR  and its value ?
5. What to specify in Generator Transformer tender ?
6. Transformer Losses Penalty ?
7. Specifications (415 Switchgear)
8. What u did in different projects?
9. Tell about your current Team in Company.
10. How work is done (Special Team or Project wise) in your company ?
11. Expected Package ?
12. Why HTC?
13. How u come to know us?
14. Why in short span of time, you post your cv on website?
15. About tender floating process ?
16. What was your involvement during pre-bid meeting etc.

2. Voith  (Telephonic Interview as told by RS)

1. Tell me about vector group Ynd11 what it’s technical mean ?
2. Protection of GT ? Differential and REF.
3. Ratio of REF CT ?
4. Why single phase transformer is used ?

3. Alstom (As told by RS, UP)

1. SLD – Any Hydro Electric Plant.
2. Schemes of Bas bars – CBIP : Main and Transfer BB Explanation
3. SS Equipments
4. LA Rating Why less than rated V ? : Fault level 40 kA, Current rating
5. Breaker : Types and ratings  — CBIP
6. Disconnector Switch / Isolator
7. Post Insulator
8. Civil

-       Structures

-       Foundations

-       Stool

9. Clearances for different Voltages

-       132/220/400kV

-       Sectional

-       Equipment

-       Earth

1. Layout of switchyard
2. Auto-Transformer: Function and why used ?
3. Transformer specification / Datasheet

-       Tx. Protection

-       WTI

-       OTI

-       Buckohles

-       Transformer Oil Functions  : Cooling, Insulation between Windings

Tea Break (Upto this 1hr)

1. What u have done…Tell.
2. Earthing : Start IEE-80, IS 3043, CBIP.

-       By flow chart of IEEE 80

-       Rg <1 ohm

-       Conductor spacing

-       Touch V, step v

-       Earthing rod : dia, length

-       Optimise the worst condition by these various standards.

3. Bus Bar Types:

-       Rigit and Flexible

-       ACSR

-       AAC

-       Al Pipe

4. SLD Full Protection from Gen. Transformer, Line, BB : Full SLD of HPP.

-       C & R Panel

-       Relaying Scheme : Diffential Protection, Distance Protection, Relay Setting (OC, EF, Trip Ckt Healthy, OV, UV)

-       REF settings

5. Lightning (RIL,Rangit)

-       Mast or Shield Wires

-       Methods : Mousa and Rizvig Method

-       Protection Area (Cone), Protection Angles : CBIP

-       Rolling square Method

6. Softwares Used

-       AutoCad

-       Etap Earthing

-       VB++

-       Mobile Software

7. Capacitor Panel

-       Pf Improvement

-       Function

-       Reactive Power injection

8. Battery Calculation

-       IEEE845

9. CT Code

-       Core

-       Class PS, 0.5, 0.2

-       VA Burden

10. PT Code

-       IVT

-       CVT

-       Dry

-       Fuse

-       11kV

11. Synchronising

-       DG sets

-       System

12. Ganttary

-       Wind Loading

-       Ice Loading

13. Tower Height – CBIP

-       400 kV (17+8)

-       220kV

14. Factor affecting at High Elevation

-       Air dielectric strength becomes less, so Temperature will reduces, so the pressure and dielectric strength.

-       Power f withstand and dynamic rating will changes

15. Corona Loss

-       Will be less in Pipe conductor

16. Cables

-       11kV

-       220kV

-       FRLA

-       Cable testing: HV test, IR test and outer area/sheath of cable stretch

-       A 3m piece of cable is put in fire for testing FRLS.

Technical Finish. Then HR and other discussion

Teaching, Any work done in Life with full enthusiasm.

4. CPRI, Bangalore  (As told by RS)

Q1. HVDC Studied?

Q2. Do u know about Power Evacuation?

Q3.  If we have 1050 MW to transmit from 1 substation to another. What electrical parameters you will think.

Q4.  If we have a 440 kV line of 400km. what will be its characteristics impedance?

Q4. If we have a 400kV of 400 km ? if line a another end is not connected to grid, then what will be the voltage level there and it is less, then how much ? what to do to remove that effect ? which element we connect  in line and where ?

5. BOP, ABB  (As told by AS)

Q: BOP Work Experience ?

Q: Difference in Tendering and DE ?

Q: Master in which field of Layout / System Engineering ?

Q:  Which Layour You Make ?  – Upto 220kV Double Bus.

Q: How equipments are arranged in substation ?

Q: List of Equipments in Switchyard ?

Q: Power Transformer Parameters ?

MVA, Vp, Vs, Cooling, Vector Diagram, Temperature, Insulation, Switching voltage

Q: 15/ 18 or 8/10 or 9/10 MVA Transformer. What are these two ratings ? and which is best ?

Ans. Generally we take 20 % difference in two ratings. so 8/10 is best.

Q: Difference between ONAN and ONAF.

Q: 433V why this voltage ?

Q: Winding Temperature of Transformer ?

Q: Oil Temrperature of transformer ?

Q: Vector diagram which you used :

– DYn11 step up

– Ynd11 Stepdown

Q: % impedance of Transformer Value ? IS-2026

Q: Earthing, What we CAlsulate ?

- R <1.0 ohm

Q: Fault Current for 132kV, 220kV, 400kV ?

- 220kV 40kA

- 132kV 31.5 kV

Q: Why for 220kV system LA used is of less rating ?

Q: For 220 kV which conductor is used ?

- Moose / Zebra

Q: Cable Sizing Parameters ?

- Voltage, Current, Temp., Type of arrangement, V drop, Length of Cable, Min. cross-section

Q: V Drop Formula for Cable ?

Motor delta-star are:

DOL : 6 times

Star-Delta: 3 times

Q: Full Form of ACSR and AAC

Q: Notice Period

6.  Electrical Design  (As told by HT)

Q1. What is fault current ?

Q2.  Earthing Design steps ?

Q3. Touch & Step Voltages Definations ?

Q4. Switchyard SLD

Q5. Fault Model – Calculations  ?

Q6. CAble Sizing and Calculations ?

Q7. % Z in Transformer  - Explain ?

Q8.  Define Synchronizing ?

Q9. Faults Ph-Ph, Ph-G, Ph-E ?

Q10. Sectionsal Clearances ?

Q11. CB GTP ?

Q12. GTP Main Parameters (Xer , CB)

Q13. Two Generators are connected to common bus then a common transforemer having all necessary details. If fault occurs at bus, what will be fault current ?

7.  Electrical Design Hydro (As told by RS)

Q1. Firm Power

Q2. Power Formula in Hydro ?

Q3. Hrdels in Hydro Power Plant ?

Q4. How capacity is decided for Hydro Power Plant ?

Q5. Power Potential Study