Top 100+ Transmission & Distribution Interview Questions And Answers
Question 1. Why Is Alternating Current Used For Transmission?
Answer :
AC is used for transmission because transformers can step it as much as excessive voltage for long distance, and right down to low voltage for local distribution and use. The output of energy stations comes from a rotary turbine, which via its nature is AC and therefore requires no power electronics to transform to DC Also, it's miles lots less difficult to exchange the voltage of AC electricity for transmission and distribution and the value of plant associated with AC transmission (circuit breakers, transformers and so forth) is a great deal lower than the equal of DC transmission. AC transmission offers a number of technical benefits. When a fault inside the network occurs, huge fault contemporary flows. In an AC device, this will become a good deal simpler to break, because the sine wave current will evidently have a tendency to zero in some unspecified time in the future making the modern-day easier to break.
Question 2. What Is Corona?
Answer :
The phenomenon of violet glow, hissing noise and production of ozone gas in an overhead transmission line is known as Corona.
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Question three. What Is Skin Effect?
Answer :
The tendency of alternating modern-day to pay attention close to the floor of a conductor is referred to as Skin Effect
Question 4. Why Is Voltage Stepped Up Before Transmission?
Answer :
Voltage is stepped up earlier than transmission due to the subsequent motives:
Reduces volume of conductor cloth
Increases transmission performance
Decreases percent line drop
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Question 5. What Are Standard Transmission And Distribution Voltages?
Answer :
Primary Transmission: sixty six kV, 132 KV, 220 kV and 400 kV
Secondary Transmission: 33 kV
Primary Distribution: 11 kV, 3-section, 3-twine
Secondary Distribution: 400 V between stages (three-phase, 4-wire) and 230 V between any individual segment and impartial
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Question 6. Explain Transmission And Distribution Systems?
Answer :
Electric-energy transmission gadget is the gadget used for bulk switch ofelectrical electricity, from producing power flora to electrical substations positioned near demand facilities. The specific structures of transmission are:
DC device
Single section AC gadget
Two phase AC device
Three segment AC machine
The a part of electricity machine which distributes electric powered energy for neighborhood use is known as Distribution System. The one of a kind distribution structures are:
• AC Distribution system
Primary distribution device
Secondary distribution device
• DC Distribution machine
2 twine DC system
3 twine DC gadget
Question 7. What Are The Equipments Used In Sub- Station?
Answer :
The factors of a sub- station are:
Primary energy strains
Ground twine
Overhead strains
Transformer for size of electric voltage
Disconnect switch
Circuit breaker
Current transformer
Lightning arrester
Main transformer
Control building
Security fence
Secondary power strains
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Question eight. What Is The Difference Between Relay And Fuse?
Answer :
A relay is a transfer; it isn't normally supposed to open below fault situations (high modern).
A fuse is a fault protection device. If a short circuit develops, big currents will go with the flow, and the fuse link will soften, causing the circuit to open.
Question 9. What Is Plcc?
Answer :
Power line verbal exchange or strength line service (PLC), additionally known as electricity line digital subscriber line (PDSL), mains communique, strength line telecom (PLT), energy line networking (PLN), or broadband over power traces (BPL) are systems for sporting facts on a conductor and are also used for electric electricity transmission. A wide range of electricity line communication technology are needed for distinctive packages, starting from home automation to Internet get entry to
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Question 10. What Are Lightning Arrestors?
Answer :
A Lightning Arrestor is a tool used in electric energy systems to protect the insulation on the machine from the dangerous impact of lightning
Question eleven. Explain The Principle Of Operation Of A Relay And A Circuit Breaker?
Answer :
RELAY: An electromagnetic relay works on two concepts
Electromagnetic appeal
Electromagnetic induction
The pressure of appeal produced has components-one is consistent and the alternative is fluctuating at a frequency, twice the natural frequency. This pressure in terms of modern is represented as-
F= K1 – K2 * I2
K1=K2 * I2
Since K1 and K2 both are constants, so the modern-day I will be regular. This is the condition whilst the relay is at the verge of operation and F=zero.
CIRCUIT BREAKER: Once a fault is detected, contacts within the circuit breaker must open to interrupt the circuit; a few routinely-saved strength (the usage of springs or compressed air) contained within the breaker is used to split the contacts, even though a number of the energy required may be acquired from the fault contemporary itself. When a modern is interrupted, an arc is generated. This arc ought to be contained, cooled, and extinguished in a controlled manner, so that the gap among the contacts can once more withstand the voltage within the circuit. Different circuit breakers use vacuum, air, insulating fuel, or oil because the medium wherein the arc forms
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Question 12. What Is A Bus Bar?
Answer :
A Bus bar is a strip of copper or aluminium that conducts power within a switchboard, distribution board, substation or different electric equipment. They shape a link among the incoming and outgoing circuits. The length of the bus bar determines the maximum quantity of present day that can be effectively carried
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Question 13. What Is Arc Formation?
Answer :
When a short circuit takes place, a heavy contemporary flows via the contacts of the circuit breaker and they may be opened by using the protecting system. At the immediately whilst the contacts start to separate, the contact area decreases hastily and large fault current causes improved current density and subsequently rise in temperature. The heat produced within the medium among the contacts is sufficient to ionise the medium. The ionised air or vapour acts as a conductor and an arc is struck among the contacts.
Question 14. What Is three-phase Supply?
Answer :
It is a type of poly section gadget and is the maximum commonplace method utilized by gridsworldwide to transfer electricity. In a three-section system, 3 circuit conductors convey three alternating currents (of the equal frequency) which reach their immediate peak values at one-of-a-kind times
Question 15. Why Do We Require Protection Against Lightning?
Answer :
The lightning surges may also motive critical harm to the high priced equipments in the strength gadget (e.G. Turbines, transformers and so on.) either via direct strokes on the device or with the aid of the strokes at the transmission lines that reach the equipment as journeying waves.
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Question sixteen. What Is A Sub-station?
Answer :
The meeting of apparatus used to alternate a few characteristics (e.G. Voltage, AC to DC, frequency, power thing) of the electric deliver is known as a sub-station
Question 17. What Is Grading Of Cables?
Answer :
The process of reaching uniform electrostatic pressure within the dielectric of cables is known as grading of cables
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Question 18. Explain The Purpose Of Fuse?
Answer :
When a short circuit or overload takes place, the present day thru the fuse will increase past its rated price which increases the temperature and fuse element melts (or blows out), disconnecting the circuit covered with the aid of it
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Question 19. What Is Transmission Cable Made Up Of?
Answer :
The foremost insulating substances utilized in cables are rubber, vulcanised India rubber, impregnated paper, varnished cambric and polyvinyl chloride.
Question 20. What Will Happen When Power Factor Is Leading In Distribution Of Power?
Answer :
If there's high energy issue, i.E. If the energy component is close to one
Losses inside the form of heat might be decreased,
Cable turns into less cumbersome and easy to carry, and really cheap to come up with the money for, &
It also reduces over heating of transformers.
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Question 21. What Are The Faults In A Three Phase Line?
Answer :
The styles of faults in a three section line are:
Phase-To-Earth Fault
Phase-To-Phase Fault
Phase-To-Phase-To-Earth Fault
Three-Phase Fault
Three-Phase-To-Earth Fault
Phase-To-Pilot Fault
Pilot-To-Earth Fault
Question 22. What Is Current Chopping?
Answer :
Current slicing in CB is the incident of arc modern interruption earlier than everyday current zero is reached. If this cutting-edge is sufficient to supply a voltage which is more than restriking voltage than the arc will retain once more. But progressively the modern falls and surely the voltage also reduces and ultimately falls down the restriking voltage and ultimately arc is extinguished. It effects in voltage oscillation within the line which affects the electrical equipments
Question 23. Which Circuit Breaker Uses Current Chopping Circuit?
Answer :
Vacuum circuit breaker uses modern-day reducing circuit
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Question 24. What Is Scada?
Answer :
SCADA (supervisory manage and records acquisition) typically refers to Industrial Control Systems (ICS): computer systems that monitor and control business, infrastructure, or facility-primarily based tactics
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Question 25. Why Do We Use A Wave Trap?
Answer :
Line entice is also referred to as Wave entice. It allows in trapping the excessive frequency conversation alerts despatched on the line from the faraway substation and diverting them to the telecom/ tele-safety panel within the substation manage room (thru coupling capacitor and LMU). The Line entice offers high impedance to the high frequency conversation indicators that obstructs the go with the flow of those alerts in to the substation Bus bars.
Question 26. Which Are Preferred – Underground Or Overhead Cables?
Answer :
Although many low voltage, neighborhood electric distribution traces are buried underground, nearly all high-voltage electric transmission traces are attempted to be located as overhead cables due to the price distinction.
Question 27. What Is The Basic Structure Of A Rotating Electrical Machine?
Answer :
It particularly includes the following circuits:
Magnetic circuit
Electric circuit
Dielectric circuit
Thermal circuit
Mechanical parts
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Question 28. What Is Specific Electric Loading?
Answer :
The number of Armature (and Stator) Amperage Conductors in line with Metre of Armature (and Stator) periphery at the air hole is known as Specific Electric Loading.
Question 29. What Is Specific Magnetic Loading?
Answer :
The common flux density over the air gap of a device is known as Specific Magnetic Loading.
Question 30. What Are The Various Types Of Ratings Of A Machine?
Answer :
The one of a kind sorts of scores are:
Continuous duty
Short time obligation
Intermittent periodic obligation
Intermittent periodic duty with beginning
Intermittent periodic obligation with beginning and braking
Continuous responsibility with intermittent periodic obligation
Continuous responsibility with starting and braking
Continuous responsibility with periodic speed modifications
Question 31. What Is A Runaway Speed?
Answer :
It is defined as the velocity which the top mover might have, if it is all at once unloaded while working at its rated load.
Question 32. What Are The Modes Of Heat Dissipation?
Answer :
The warmness can be dissipated via
Conduction
Convection
Radiation
Question 33. What Is A Field Form Factor?
Answer :
It is the ratio of the common flux density over the pole pitch to the most flux density. It is also called flux distribution aspect.
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Question 34. What Is A Window Space Factor?
Answer :
It is defined as the ratio of copper vicinity inside the window of the total window region
Question 35. What Are The Different Types Of Cores?
Answer :
Different Types of cores are:
Rectangular center
Square core
Stepped center
