Describe the types of transport lines and why transport lines are transposed?

Describe the types of transmission lines: Transmission lines are divided into three categories on the basis of length and operating voltage i) Short length transmission lines:- When the length of a transmission line is below 80km and the transmission voltage is below 20 kv, it is called a short length transmission line.ii) Medium Transmission Line: When the length of the transmission line is between 80 – 200km and the transmission voltage is between 20 – 100 kv, it is called medium transmission line. iii) Long transmission line: When the length of transmission line is above 200 km and the transmission voltage is above 100 kv, it is called long transmission line.

Why is transposition of transport lines? Answer: Due to transposition, the average inductance capacitance of each line is equal. Show the resulting voltage regulation and transport efficiency diagram. is relatively advanced.

What is the Ferranti effect? Ans: In medium and long transmission lines with no load or very little load connected, the voltage value at the receiving end is higher than that at the receiving end due to the flow of a leading charging current. This phenomenon is called the Ferranti effect.

Why is underground capacitance higher than overhead lines? Ans: In underground cable system conductor and conductor to-earth sheaths have very short spacing. Moreover, the permittivity of cable dielectric is always higher than that of air. Because of this, the capacitance of underground cables is always higher than that of overhead lines of the same length.

What is grid system? Ans: The system of supplying electricity generated by multiple power plants together in a network through specific high voltage transmission lines is called grid.

Give brief description of feeder, distributor and service main? Answer: Feeder: The thick conductor or cable connecting the generating station with the populated area is called feeder. The main feature of the feeder is – No tapping is taken out from the feeder to supply power to consumers. As a result, the value of current remains constant along its entire length. Basically feeders are designed based on current carrying capacity.

Distributor: Electricity is supplied to consumers by taking out various tappings from the distributor. Due to tapping, the value of current varies along the length of the distributor. The voltage drop of the distributor should not be more than 6 V.

What are the advantages and disadvantages of HVDC?

 Ans: Advantages: (i) Since there is no charging current in DC, even if the line is very long, the stability of the supply system is not lost. ii) Even if one of the positive or negative poles is bad, 50% of the power supply can be maintained with the help of the other pole. iii) Corona loss and radio interference are less in DC compared to AC in high voltage transmission. iv) In case of DC the insulation of the conductor may flow a small amount of leakage current, which can be neglected.

Disadvantages : M COACHING & GUIDE OPTIMUM i) Transformer cannot be used in this system. For this reason both ends of HVDC transmission have to be connected to the AC system. That is, a single DC system capable of sub-transmission and distribution. ii) Thyristors used at both ends of the line are very expensive. & GUIDE OPTIM iii) DC Voltage cannot be stepped up. iv) There is no HVDC circuit breaker in this system.

Compare A.C and D.C transmission?

Answer: A.Ctransmission i) Requires three wires, resulting in higher copper consumption. ii) The voltage can be stepped up and down as required by a transformer. iii) Inductance capacitance, power factor, surge and skin effect exist. iv) As the electrical stress on the insulation is high, more insulation is required. D.Ctransmission i) Requires two wires. Power can be transmitted in one wire using earth as neutral.It saves copper. ii) Transformer cannot be used as voltage cannot be step-up or step-down. iii) They have no effect. iv) Electric stress on insulation is times 1 √h of AC. Hence insulation takes Opcomm. v) Voltage regulation v) Voltage regulation is poor. advanced vi) Corona-induced vi) Corona-induced dissipation is very low and the peripheral communication power is wasted. As a result, there is a disturbance in the communication line adjacent to the line. Disruption rate is very low.