Tricky but Easy Electrical Engineering!
Over voltages in power system may occur due to lightning or switching operation. These overvoltages could reach dangerous amplitudes for power system apparatus. To protect the system electrical equipment and to guarantee an economic and reliable operation, surge arresters are applied in almost all types of electrical power network. Gapless zinc oxide (ZnO) surge arresters … Read more
Being an Electrical Engineer, it is very much important to know about Electrical safety and what should be the action if someone gets shock. Safety is the first priority in any Industry and it is the responsibility of an Electrical Engineer to make aware of the Electrical safety to his/her subordinate. In most cases of … Read more
A Transmission Line classification based on its length are Short, Medium and Long lines. The length of line is calculated between the two substations of concern. If the length of line is less than 80 km then it is said to be Short Transmission Line. The length of Medium Transmission Line varies from 80 to 160 km. … Read more
SF6 gas is used in High Voltage and Extra High Voltage Circuit Breaker. For better understanding of why SF6 is chosen, we will go through the chemical and dielectric properties of SF6. Chemical Properties of SF6: 1) SF6gas is very stable gas and remains stable up to 500 °C. 2) SF6gas is inert. The … Read more
Lightning is an electric discharge in the form of a spark or flash originating in a charged cloud. Lightning is a very long electrical spark, ‘very long meaning greater than about 1 kilometer. Most lightning is generated in thunderstorms and is characterized by a length of 5 to 10 km, at the extreme about 100 … Read more
Protection of Power Transmission Line from the effect of Lightening is achieved by using Sky Wire which is also known as Ground Wire or Shield Wire. A direct Lightening Strike on a Power line or induced voltage from a nearby Lightening Strike may lead to the line flashover or insulation failure of transformers, arrestors … Read more
Isolator and Circuit Breaker both are switches to isolate a section of power system. But Isolator is off load device whereas Circuit Breaker is on load device. Off load device means, Isolator cannot be operated when load is connected i.e, current is flowing through the circuit. Therefore, Isolator shall only be operated when that circuit … Read more
Two types of Circuit Breakers are used in 400 kV Switchyard. They differ in only one features i.e. Pre Insertion Resistor (PIR). One type has PIR whereas other has no such provision. Both type of breaker are self-compensating Spring to Open and Spring to Close type. SF6 gas is used as arc quenching medium. The … Read more
In this post we will discuss about the feature of Harmonic Restraining feature of Differential Protection. First we should know why Harmonic Restraining is needed? Suppose we are going to energize the Transformer, obviously the Transformer will have an Inrush current which is around 6 times of full load current. Refer “Transformer Inrush Current” for … Read more
As discussed in the post “Transformer Differential Protection”, differential protection is supposed to operate for the internal faults or for the zone of protection it is intended for. Differential protection is not supposed to operate for a through fault. Through fault means a fault outside the zone of protection. Thus as discussed in earlier post, … Read more