# Recent questions and answers in High voltage engineering

Why high voltage is used in power transmission?

What is the difference between line and phase current?

What is the difference between line and phase voltage?

What does BIL stand for in electrical terms?

Why does increase in current mean a decrease in voltage?

Why high voltage can reduce power loss?

The breakeven distance for HVDC transmission is (A) 100 kM (B) 250 kM (C) 500 kM – 800 kM (D) Above 1000 kM

What is the definition of extra low voltage?

Which of the following is TRUE with respect to HVDC transmission line? (A) For a short distance it is economical over HVAC. (B) In HVDC system, harmonics are not generated. (C) Use of HVDC can improve system stability. (D) Less and cheap terminal, equipments are required in HVDC.

A Unified Power Flow Controller (FACTS controller) is a voltage source converter based (A) Inter-phase power controller (B) Static Compensator (C) Combination of series and shunt compensators (D) Solid-state series compensator

In voltage source converter based HVDC transmission system the active power is controlled by changing (A) phase angle of the converter ac input voltage (B) supply frequency of the converter ac input voltage (C) magnitude of the converter ac input voltage (D) DC voltage at the inverter terminals

In the case of second order differential equation if the damping ratio is unity, then the poles are  A) Equal, positive and real B) Imaginary and complex conjugate C) Equal, negative and real D) None of the above

The effect of corona in high voltage a.c. transmission line is  A) Increased energy loss in the transmission line B) Increased line reactance C) Increased line to line capacitance D) All of the above

A bus coupler circuit breaker is utilized in a sub-station for  A) Connecting the transmission line with the bus-bar B) Connecting two power transformers in parallel C) Connecting the bus-bar with ground D) Connecting main and transfer buses in the sub-station

When the communication line run parallel to the power lines in close proximity  P. The electromagnetic effect produces current due to induction resulting its superposition on the speech signal of the communication line causing distortion  Q. The electrostatic effect raises the potential of the communication circuit as a whole and thereby posing a threat of damage to the ... lines  Which of the following combinations is valid?  A) R only B) P, Q & R C) P & Q only D) P & R only

Due to skin effect  A) Portion of conductor near the outer surface carries less current and the inner core of the conductor carries more current B) Portion of conductor near the outer surface carries more current and the inner core of the conductor carries less current C) Current density over the entire cross section of the conductor is uniform D) Current density near the center of the conductor is maximum and near the surface of the conductor zero

Back-to back connection is used in HVDC system to  A) Provide synchronous tie between two systems B) Provide bulk power transmission over long distance C) Provide asynchronous tie between two systems D) Reduce the line voltage drop and the transmission loss

What are the losses in a transmission line?

How do you fix voltage drop?

Is more power dissipated in series or parallel?

What is meant by flash over voltage?

Is 50hz or 60hz better?

What is dielectric breakdown strength?

How can power loss be reduced?

How do you calculate power loss?

What is the lowest acceptable insulation resistance for a cable?

What is the purpose of using a Megger?

Why high voltage test is done?

What is dielectric withstand voltage?

What do you mean by insulation coordination?

What is a safe distance from power lines?

What is a Ductor tester used for?

What is an insulation resistance test?

What is impulse voltage of transformer?

What is double or reinforced insulation?

What is a switching impulse?

What is Extra High Voltage?

What is the difference between a line voltage and low voltage control system?

What is basic insulation level?

What are the advantages of high voltage transmission?