Tricky but Easy Electrical Engineering!
3rd Harmonic Leakage Current Test is performed on Surge / Lightening Arrestor (LA) to monitor its healthiness. Need for Monitoring of LA The need for monitoring of Metal Oxide Lightening Arrestor (LA) arises as its deterioration may lead to heating and consequent blasting. Though LA being cheaper can be replaced but blasting of LA can … Read more
Many times I have been asked to justify why to conduct primary current injection test at rated current of circuit? Why to invest money in purchasing Primary Current Injection Kit? This is why I decided to write a topic on the importance of primary current injection test. After reading the topic you will be able … Read more
In Control System, we often encounter Laplace Transform. Transfer Function is expressed as the ratio of Laplace Transform of output and input to a system. Laplace Transform is used to ease the calculation as solving differential equation is quite tiresome. Suppose there is a second order differential equation, then solving of the second order differential … Read more
Power System instability is basically of two forms: a) Instability of Load which means stalling of Synchronous Load connected to the system. b) Pole slipping or out of step of Generators connected to the Synchronous Grid known as Synchronous Instability. Synchronous Stability is categorized into two: 1) Steady State Stability 2) Transient State Stability Steady … Read more
Automatic Voltage Regulator (AVR): Automatic Voltage Regulator is a device which maintains the Generator output terminal voltage. To be more accurate, AVR is a controller which always compares the Generator output terminal voltage Vt with the set reference voltage Vrefand as per the error signal i.e. (Vref – Vt) it changes the filed excitation of … Read more
Generator, Generator Transformer and Unit Transformer protections have been classified into Class-A, Class-B and Class-C. Class-A tripping is further classified into Class-A1 and Class-A2. In this post we will discuss each type of tripping classes and their significance. Picture taken from http://universalerectors.com/steam_turbine_generator.html Basis of Tripping Classification: The tipping classification of Generator is based on the need … Read more
Lets us consider a doubly excited magnetic system as shown in figure below. In this model of machine, both stator as well as rotor is assumed to be salient pole type. Let’s assume that stator is energized from source Vs whereas rotor is energized with source Vr. Total torque developed in such doubly excited magnetic … Read more
Rate of Change of Frequency (ROCOF or df/dt) relay is used for fast load shedding, to speed up operation time in over- and under-frequency situations and to detect loss of grid. For better understanding of role and operation of df/dt relay, let us first study the variation of frequency with load for a Grid. Graphical … Read more
The oil can only be filled in the transformer which satisfies the standard specifications mentioned by the manufacturer of transformer. Normally Transformer is supplied with gas filled i.e. the Main Tank of Transformer is filled with Nitrogen gas under some specified pressure to prevent any degradation of the insulation of core and winding. But we … Read more
Magnetization curve or saturation curve is basically the graphical relationship between the magnetic flux density B and magnetic filed intensity H for a given magnetic material. As we know that, B = μ0μrH where μ0 = Permeability of free space = 4πx10-7Tm/A μr = Relative Permeability of material Thus by using the above equation, we … Read more