What is Electrical Power System:
The Power system is defined as the system which involves generation, Transmission and distribution, Protection and utilization of electrical energy.\\Before discussing the electrical power system in detail we should know the importance electrical Energy.
Importance of Electrical Energy
- Energy exists in different forms in nature but the most important form is the electrical energy. The modern society is so much dependent upon the use of electrical energy that it has become a part and parcel of our life.
- Energy may be needed as heat, as light, as motive power etc. The present day advancement in science and technology has made it possible to convert electrical energy into any desired form. This has given electrical energy a place of pride in the modern world.
- Electricity has many uses in our day to day life. It is used for lighting rooms, working fans and domestic appliances like using electric stoves, A/C and more. All these provide comfort to people. In factories, large machines are worked with the help of electricity. Essential items like food, cloth, paper and many other things are the product of electricity.
- Modern means of transportation and communication have been revolutionised by it. Electric trains and battery cars are quick means of travel. Electricity also provides means of amusement, radio, television and cinema, which are the most popular forms of entertainment are the result of electricity. Modern equipment like computers and robots have also been developed because of electricity. Electricity plays a pivotal role in the fields of medicines and surgery too — such as X-ray, ECG. The use of electricity is increasing day by day.
Superiority of Electrical Energy
Electrical energy is superior to all other forms of energy due to the following reasons.
- Convenient form: Electrical energy is a very convenient form of energy. It can be easily converted into other forms of energy. For example, if we want to convert electrical energy into heat, the only thing to be done is to pass electrical current through a wire of high resistance e.g., a heater. Similarly, electrical energy can be converted into light (e.g. electric bulb), mechanical energy (e.g. electric motors) etc.
- Easy control: The electrically operated machines have simple and convenient starting, control and operation. For instance, an electric motor can be started or stopped by turning on or off a switch. Similarly, with simple arrangements, the speed of electric motors can be easily varied over the desired range.
- Greater flexibility: One important reason for preferring electrical energy is the flexibility that it offers. It can be easily transported from one place to another with the help of conductors.
- Cheapness: Electrical energy is much cheaper than other forms of energy. Thus it is overall economical to use this form of energy for domestic, commercial and industrial purposes.
- Cleanliness: Electrical energy is not associated with smoke, fumes or poisonous gases. Therefore, its use ensures cleanliness and healthy conditions.
- High transmission efficiency: The consumers of electrical energy are generally situated quite away from the centres of its production. The electrical energy can be transmitted conveniently and efficiently from the centres of generation to the consumers with the help of overhead conductors known as transmission lines.
Generation of Electrical Energy
Electrical Energy is generated by plants called generating stations. A generating station consists prime mover coupled with alternator for production of electricity. Prime mover(Turbine) converts energy from some other form into mechanical energy and alternator converts mechanical energy into electrical energy. They different forms of electric generating stations are
- Hydro-Electric Generating Station.
- Steam/Thermal Generating Station.
- Nuclear Generating Station.
- Diesel Generating Station.
Transmission of Electrical Energy
The Transmission of electrical energy involves network that transfers electric power from generating stations to the distribution substations. This network is called the transmission system.
The Electrical energy can be transmitted in AC or DC form. Traditionally, AC has been used for years now, but HVDC (High Voltage DC) is rapidly gaining popularity.
When it is generated at a power station, electrical energy will typically be anywhere between 11kV and 33kV. Before it is sent to distribution centres via transmission lines, it is stepped up using a transformer to a voltage level that can be anywhere between 100kV and 700kV or more, depending on the distance that it needs to be transmitted; the longer the distance, the higher the voltage level.
The reason electrical power is stepped up to these voltage levels is to make it more efficient by reducing the I2R losses that take place when power is transmitted. When voltage is stepped up, the current reduces relative to the voltage so that power remains constant, thus reducing these I2R losses.
The transfer of a large quantity of electrical power from the initial generating station to the receiving station via overhead electrical lines is called primary transmission. In some countries, underground cables are also used in cases where transmission takes place over a shorter distance.
After reaching the Electrical power at receiving station, the electrical power is stepped down to a voltage typically between 33kV and 66kV. Then Transferred to the substations near to load centres like Village, Industries, cities. This stage of transmission is called secondary Transmission.
Distribution of Electrical Energy
When electrical power reaches a substation near to load centres, it is stepped down once again by a step-down transformer to voltages 11kV. From here, the transmission phase enters into the distribution phase, and electrical power is used to meet demand from primary and secondary consumers.
Large industrial consumers can be supplied at 11kV directly from these substations. This stage is called as primary distribution.
Finally, the voltage is stepped down to 415 volts by a pole-mounted distribution transformer and delivered to the distributors. End consumers are supplied through a service mains line from distributors. This stage is called secondary distribution. The secondary distribution system consists of distributors and service mains.
Protection of Electrical Energy
A system which is responsible for protecting electrical systems from faults by isolating the faulty part from the rest of the system, so power is not disconnected from healthy parts is called power protection system.
A good electric power system should ensure the availability of electrical power without any interruption to every load connected to it. Generally, power is transmitted through high voltage transmission line and lines are exposed, there may be chances of their breakdown due to storms, falling of external objects, and damage to the insulators etc. These can result not only mechanical damage but also in an electrical fault.
Protective relays and relaying systems detect abnormal conditions like faults in electrical circuits and automatically operate the switchgear to isolate faulty equipment from the system as quick as possible.
This limits the damage at the fault location and prevents the effects of the fault spreading into the system. The switch gear must be capable of interrupting both normal currents as well as fault current. The protective relay on the other hand must be able to recognize an abnormal condition in the power system and take suitable steps so that there will be least possible disturbance to normal operation. Relay does not prevent the appearance of faults. It can take action only after the fault has occurred. However, there are some devices which can anticipate and prevent major faults. For example, Buchholz relay is capable of detecting the gas accumulation produced by an incipient fault in a transformer