EE8701 HVE 2marks

Anna University Regulation 2017 EEE EE8701 HVE 2marks & 16marks for all 5 units are provided below. EE8701 HVE Short answers, Question Bank for HIGH VOLTAGE ENGINEERING Engineering are listed down for students to make perfect utilization and score maximum marks with our study materials.

EE8701 HVE HIGH VOLTAGE ENGINEERING

1. What are the chief causes of over voltages in electric power system?
1) Lightning over voltages (Natural causes)
2) Switching over voltages (system oriented causes)

2. How are switching over voltages originated in a power system?
Switching over voltages originate in the system itself by the connection and disconnection of circuit breaker contacts or due to initiation or interruption of faults.

3. What are switching over voltages?
Switching over voltages are highly damped short duration over voltages. They are temporary over voltages of power frequency or its harmonic frequencies.
They are sustained or weakly damped
They originate in switching and fault clearing process.

4. For ultra high voltages, perhaps, switching surges may be the chief condition for design considerations. Why?
The magnitudes of lighting voltages appearing on a transmission line do not depend on line design hence lightning performance does not improve with increasing insulation level, that is, the system voltage. On the other hand switching over voltages is proportional to
operating voltage. Hence for ultra high voltages switching surges may he the chief condition for consideration.

5. State the parameters and characteristics of the lightning strokes:
1. Amplitude of currents
2. The rate of rise.
3. The probability distribution
4. Wave shape of the lightning voltage and current.
5. Time to peak value.

6. How are lightning strokes on transmission lines classified.
1) Direct strokes
2) Inducted strokes
Direct stroke:
When thunder cloud directly discharges on to a transmission line tower or line wires, it is called direct stroke. This is the most severe form and this occurs rarely.
Inducted Stroke:
When thunder storm generates negative charges at its ground end. The transmission line and Tower develop induced positive charges.

7. What is Back Flashover?
Some times when a direct lightning stroke occurs on tower if the tower footing resistance is considerable, the potential of the tower rises to a large value, in view of the huge lightning stroke current, steeply with respect to the line and consequently a flash over may take place, along the insulator string. This is known as Back Flash over.

8. Give the mathematical Model for lightning:
Let Io – lightning current (current source)
Zo – source impedance(of the cloud )
Z – object Impedance
V – Voltage built across the object
Tr line : 300 to 500 ohms
Ground wire : 100-150ohms
Tower : 10-50 ohms
Therefore Z/Zo=less and can be neglected.
Therefore V= Io.Z
Where Io = lightning stroke current
Z = surge impedance.

9. A lightning stroke 10KA strikes a line of 400 ohms surge Impedance. (I) What is the over
Voltage caused?(II) If a direct stroke occurs over the top of the unshielded Tr line what is the
over voltage?
Case :I
V = Io . Z
= 10KA .400 = 4000 kv
Case II
V = Io (Z/2) = 10 x 400 KV =2000KV

10. What is Thunder storm days?
Thunder storm days (TD) (is known as the Iso Keraunic level) is defined as the number of days in a year when thunder is heard or recorded in a particular location,
 The incidence of lightning strikes on Tr. Line / substation in related to T.D.
 T.D is =5 to 10 in Brittan
30 to 50 in USA
30 t0 50 in India

EE8701 HVE Unit 1 2marks & 16marks – Download Here

EE8701 HVE Unit 2 2marks & 16marks – Download Here

EE8701 HVE Unit 3 2marks & 16marks – Download Here

EE8701 HVE Unit 4 2marks & 16marks – Download Here

EE8701 HVE All Units 2marks & 16marks – Download Here

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