High Voltage AC Power Transmission System

High Voltage AC Power Transmission System

Generally, a modern electrical power system is the AC type. We know that the modern power system is divided into three parts, such as Generation, Transmission, and Distribution. Basically, high-voltage AC power is transmitted from the generating station to the load center through the transmission line which is called a high voltage AC power transmission system. This high-voltage AC power transmission line meets the different electrical substations that is called grid substations/high voltage substations/primary transmission substations. The power is divided into various substations to distribute the electricity for consumer use.

What is the Difference Between Alternating Current and Direct Current?

Electrical energy comes into two forms: Direct current (DC), and Alternating current (AC). Now a day alternating current is used more because most of the electrical supply systems are AC. Basically, a high-voltage electrical transmission system consists of a bunch of components click to know details.

Direct Current (DC)

Whenever electrical energy is generated then it is DC power. Basically, electrical energy was generated in 1820 and early 1830 by Michael Faraday, he was a British scientist. An electric current was generated by the movement of a loop of the wire between the two magnetic poles and it was a DC current. In the 1970s and early 1980 electrical energy could be generated in the power stations.

At one stage the scientist is able to generate low-voltage DC power, and this power is used for lighting purposes. After a few years, electrical energy is generated in Alternating Current (AC) and used for commercial purposes due to the greater advantages of Alternating Current.

Alternating Current (AC)

American engineer and physicist Nikola Tesla has made dozens of advances in the production, transmission, and application of electrical energy. He invented the first alternating current motor and invented AC generation and transmission technology. Based on which AC power is produced today. There are some differences between Alternating Current and Direct Current (DC), such as

Alternating Current (AC)Direct Current (DC)
Alternating current is easy to maintain and safe to transmit long-distance.Direct current is not safe to transmit over long distances. Power loss occurs due to long-distance transmission.
The electric flow is changed due to the rotating magnetic field.Direct current flows in a single direction due to the steady magnetism.
Basically, alternating current changes its direction 50, or 60 times in a second.Direct current has no frequency.
AC power changes its direction periodically.DC power cannot change its direction, always flow in the same direction.
AC power can be generated at very high voltage.DC power cannot generate very high voltage due to the commutation problem.

Why is Stone used in Electrical Substations?

An electrical substation is a very important part of the whole power system. There are a large number of crucial high-voltage equipment (Electrical power transformer or distribution transformer, current transformer, potential transformer, and other high-voltage switchgear equipment) installed in the electrical substation. Such kinds of high-voltage equipment are grounded. Due to reduced ground potential rise stone is used in an electrical power substation.

In short, the stone is widely used in the electrical substation to reduce the touch potential and step potential whenever electrical technicians work in the switchyard. Basically, whenever a short circuit current flows through the conductor then touch potential and step potential occurs. Stone is used to give a very high resistance to ground and foot. On the other hand, stones in the substation can stop growing grass and weeds. 

What is the Comparison Between AC and DC Transmission Systems?

An electrical transmission system is used for AC and DC. Basically, most of the power line in the power system is AC. DC transmission is required wherever AC power is unavailable. There are lots of advantages and disadvantages between AC and DC transmission systems, such as

Advantages of DC transmission System

  • DC power transmission requires two conductors as compared to AC transmission.
  • DC power transmission has no capacitance, inductance, phase displacement, and surge problems.  
  • The voltage drop in the DC transmission is very low due to the absence of inductance.
  • DC transmission has no skin effect.
  • DC transmission line has no corona loss and reduced interference with the communication circuit.
  • The high-voltage DC transmission is free from dielectric losses.
  • There is no stability problem in the DC transmission line.

Disadvantages of HVDC Transmission System

HVDC means High Voltage, Direct Current. We know that DC power cannot be widely used in the modern power system due to some major problems. The disadvantages of DC transmission are given below.

  • The DC electric power cannot generate very high voltage due to its commutation problem.
  • The DC switches and circuit breakers have their own limitations.

What are the Advantages of a High Voltage Transmission System?

Nowadays electrical energy is generated, transmitted, and distributed in the form of AC due to the greater advantages of a high voltage electrical transmission system, or advantages of AC transmission.

  • Electrical power can be generated at a very high voltage.
  • You can step up or step down the voltage as your statutory limitation.
  • AC switches and circuit breakers have no limitations.

High voltage transmission power reduces the volume of conductor materials. The high-voltage AC power is transmitted through the transmission line due to the following effect:

               Load current = P/ √3 V cosΦ 


P = Power transmitted in watts.

V = Line voltage.

CosΦ = power factor of the load.

L = length of the line.

R = resistance per conductor.

ρ = resistivity of the conductor material.

a = area of the X- section of the conductor.

The transmission voltage and power factor are inversely proportional to the volume of the conductor material.

What are the Disadvantages of High Voltage Transmission Systems?

Though AC transmission has greater advantages, it has also some disadvantages, such as

  • AC power needs more copper than DC power to transmit the long distance.
  • AC transmission line construction is more complicated than DC transmission line.
  • In the AC transmission system, the skin effect is responsible for increasing the inductive resistance in the transmission line.
  • Continuous power losses occur in the high-voltage electrical transmission system due to the line capacitance.

What is the Limitation of High Voltage Transmission?

From the above discussion, it becomes clear that there are lots of advantages of a high voltage transmission system that saves the conductor materials. There are some limitations to the high-voltage AC power transmission system, such as

It means that there is a statutory limit to stepping up voltage levels and transmitting very high voltage through the transmission line. It is noted that there is a limit to stepping up the voltage level.

What is a Balanced and Unbalanced Load?

A load that is subject to the ground, at either end or the terminals is called a balanced load. On the other hand, balanced load means that where the load is distributed between the phases in the same way, the magnitude is the same within three phases, and a three-phase system will have the same phase rating which is called balanced load.

An unbalanced three-phase load is one where the load is not evenly distributed across the three phases. The maximum single-phase loading must be multiplied by three-phase to obtain an equivalent three-phase rating. An unbalanced load gives rise to uneven phase-to-phase and phase-to-neutral voltage. If the load is balanced the current through the neutral wire is reduced to zero.

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