Tricky but Easy Electrical Engineering!
Electrical Protection is considered as the heart of power system. Protection system should be such robust to isolate the fault in minimum possible time to minimize the equipment damage. The design of electrical protection is based on the following basic considerations: Adequacy The selected protection should be adequate to cover all types of faults and … Read more
A distance relay is said to under reach when the impedance seen by relay due to fault is more than the relay setting value even though the fault point is within the protected zone of line. This means that reach of relay has decreased from the setting value. Therefore, percentage under reach can be defined … Read more
Capability Curve of Generator defines the boundaries within which it can deliver reactive power continuously without overheating. Generator rating is specified in terms of MVA and power factor at a particular terminal voltage. Active power delivered by generator is only limited by the power delivering capability of turbine. But the reactive power which a generator … Read more
Zero sequence filtering is a concept used to eliminate zero sequence current component from the secondary current of Current Transformer used in Differential Protection of Transformer. This concept is useful in Transformer having earthed Star winding. What is the Need for Zero Sequence Filtering? Let us have a detailed discussion on this topic. For better … Read more
Loadability of line is defined as the extent of load which can flow through the line without exceeding the limitations. Line Loadability is expressed in percentage of Surge Impedance Loading of line. The limiting factor for line loading are: thermal limit, voltage drop limit and steady state stability. The loading of line shall not exceed … Read more
Surge Impedance is the characteristic impedance of a lossless transmission line. It is also called Natural Impedance because this impedance has nothing to do with load impedance. Since line is assumed to be lossless, this means that series resistance and shunt conductance is negligible i.e. zero for power lines. This means that, Series Resistance R … Read more
Characteristic Impedance of a Transmission line is defined as the square root of ratio of series impedance per unit length per phase and shunt admittance per unit length per phase. If z and y are series impedance and shunt admittance of line, the characteristic impedance Zc is given as Zc = √(z/y) Where z = … Read more
End Part Heating is localized heating at the end region of stator core of Generator. This heating is a result of eddy current loss in the laminations of stator core due to end turn flux of armature winding. This heating imposes a limitation on the operation of Synchronous Generator know as End Part Heating Limit. … Read more
Grounding Transformer is often called Earthing Transformer. The purpose of Grounding Transformer is to artificially create neutral point. In Delta Connected Transformer or Generator where neutral point is unavailable or in case where neutral point is inaccessible, Grounding Transformer is used to create neutral point. Constructional Design of Grounding Transformer Grounding Transformer is so designed to … Read more
VVVF stands for Variable Voltage Variable Frequency. VVVF Speed Control method is widely used method for Induction Motor. Origin of VVVF Speed Control As we know that synchronous speed of machine is given as N (rpm) = 120f/P …………………………………(1) where f is frequency and P is number of pole. Thus if we can change the … Read more