POWER SYSTEM - BIGGEST TOPIC - GATE SYLLABUS

The major topics in Power Systems can be listed as follows:

• Transmission and Distribution
  • The first topic under this unit is overhead transmission lines and in this topic first you need to memorize the expressions for Inductance and Capacitance for both Single Phase and Three Phase Lines. So you should practice some problems based on this which involve the computation of GMD and GMR.
  • The next topic that you should cover is modelling of Short and Medium Transmission Lines as Long Transmission Lines is not much important in Steady State Analysis and Short Transmission Line is most important.
    Here you should also focus on the A,B,C,D Parameters of the line and the power expressions in terms of A,B,C,D and remember the approximate voltage regulation in Short Transmission Line which is same as Transformer.
  • The next topic under this unit is Surges and in that topic you need to memorize the thevenin equivalent circuit for analysis of surges and by that you can easily calculate the Transmission and Reflection Coefficient for Voltage and the coefficients for currents are not important.
  • The other important topic is Voltage Control and Power Factor Correction and both these concepts for Numericals involve a single approach which will be better illustrated in kuestion but these two concepts are important as you can expect one of either two topics in GATE exam.
  • The next topic is UG Cables and in UG Cables there are two important concepts, one is the insulation resistance and other is the capacitance model for 3 phase  3 core belted cable which has core capacitance and sheath capacitance but question is rare from this topic.
  • The other small topic under this unit is Overhead Insulator where only a single problem based on voltage distribution across different discs can be asked and that you can easily derive using KCL or remember the expression upto 3 discs.
  • The last topic is the Distribution Systems which also has a single type of problem which involves just applying KVL and finding the currents in different branches.

• Load Flow Studies
  • In this unit you need to study about construction of Bus Admittance Matrix and you can leave out the algorithm for construction of Bus Impedance Matrix.
  • But we need to study the fault Analysis by the use of Bus Impedance Matrix which involves knowing that diagonal elements of the matrix represent thevenin impedances at different buses.
  • The next thing that we need to remember is the order of Jacobian Matrix in Newton-Raphson Load Flow Solution.
  • Also, there are some simple question where we need to find voltages and their angles at different buses and those are the simplest questions as they just involve using KVL between different buses and using power expression for Short Transmission Line and this point will be more illustrated in Kuestion.

• Economic Load Dispatch
  • In this topic you just need to study about the transmission loss coefficients and penalty factor and then how to distribute load across various generating units based on Incremental Cost and Penalty Factor.

• Fault Analysis
  • Here we need to study about Symmetrical and Unsymmetrical faults and first thing in case of Symmetrical faults is the transient and steady state component of fault current and there you just need to memorize a single expression by which you can easily derive the maximum momentary current as well.
  • Then in symmetrical fault analysis you need to solve problems where we find the symmetrical SC currents by drawing the equivalent circuits and also problems where we need to calculate the current limiting reactance.
    One thing that you need to take care about is units as the answer may be given in pu or in ohms so you need to take care else you can mark the incorrect answer.
  • The last thing about symmetrical faults is calculating the ratings of Circuit Breakers based on Symmetrical fault Analysis like Momentary Current, Breaking Current and Making Current.
  • Before going to Unsymmetrical Fault Analysis you need to study about Symmetrical Components which involves just a small transformation matrix and about Sequence Networks in which zero sequence network for Transformers in most important and can be asked directly in exam. This is explained in detail in K-Notes for Power Systems which will be up soon.
  • In case of Unsymmetrical Fault Analysis we need to remember the equivalent circuits for all three types of faults LG, LL and LLG Faults and how to calculate fault current from sequence components.

• Power System Stability
  • This is the smallest topic in Power Systems but still it is very important. Here Steady State Stability is not Important but transient stability is and you need to remember the two inertia constants “H” and “M” for that and the swing equation.
  • The next thing is that you need to remember the equivalent M and H when there are two machines which are swinging coherently or in-coherently.
  • The last and most important topic is the equal area criteria for calculating the critical clearing angle and i would recommend that you understand the method involved instead of memorizing the expressions involved as that will reduce the chances of error.

• Power System Protection
  • This is most rarely asked topic and is widest of all the units but now since exams are happening in multiple sessions so we can expect one question at least in one of the sets.
  • The only numerical part in this unit is concentrated around Plug Setting Multiplier(PSM) and the differential relay so you need to be clear on both the aspects and practice a few problems based on these two concepts.
  • Other than that for theoretical purposes you can remember the usage of some general relays like Distance Relays types and which type is used where and also the types of relays used in Transformers like Buchholz Relay.