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 Question: What is swing Equation ? By: supriya     Date: 2012-07-04 Answer: A swing equation describes the dynamic behaviour of the synchronous machine torque angle and rotor speed or it describes the electro-mechanical behaviour of the machine. Equal area criterion, used for finding the critical clearing time, is derived from the swing equation. Please go through Chapter 2 where swing equation is clearly explained. By: Dr. B. Kalyan Kumar     Date: 2012-07-20

 Question: what is EQUAL AREA CRITERION, CRITICAL CLEARING ANGLE AND TIME FOR TRANSIENT STABILITY. By: supriya     Date: 2012-07-04 Answer: Equal area criterion is derived from swing equation. Equal area criteria states that, when a fault occurs in the system because of which the output electrical power drops then the fault should be cleared within a certain critical time such that the area of acc acceleration in P-Î´ during a fault should be equal to the area of deceleration after the fault been cleared at a critical time so that the torque angle will not swing beyond the maximum permissible limit for stability. Equal area criterion is explained in detail in Chapter 2. By: Dr. B. Kalyan Kumar     Date: 2012-07-20

 Question: FACTORS AFFECTING TRANSIENT STABILITY ? By: supriya     Date: 2012-07-04 Answer: There are many factors which effect transient stability. The synchronous generator parameters, excitation system, speed governor, power system stabilizer, the network conditions, tap chaning transformer etc. will be effecting transient stability By: Dr. B. Kalyan Kumar     Date: 2012-07-20

 Question: plz upload some course on relays,circuit breakers (protection systems) By: levicorpus     Date: 2012-07-10 The co-ordinator will post his answer

 Question: in case of transient stability, rotor of a synchronous machine attains synchronous speed after a sequence of oscillations when the load is suddenly increased. in case of steady state stability, how does the machine attains synchronous speed after slowing down when the load is gradually increased? By: Rahul Roy     Date: 2012-07-12 Answer: Synchronous generators are provided with speed governors. Since, speed governors are mechanical systems they take certain time to act and hence their effect is not very significant during transients. After transients if the synchronous machine rotor reaches to a speed other than synchronous speed then the speed governor will act and will bring back the rotor speed to synchronous speed. The modelling aspects and characteristics of the speed governor are given in Chapter 4. By: Dr. B. Kalyan Kumar     Date: 2012-07-20

 Question: when the load on a syn motor is slowly incrsd(steady state stability),it slows down to incrs the load angle to meet the incrsd load.after attaining the new load angl,how does it attain the synchronous speed again?does the machine behave in the same oscillatory way as in case of transient stability? By: Rahul Roy     Date: 2012-07-12 Answer: When the load on a synchronous machine increases suddenly, the rotor of the machine slows down during transients. This is because of mismatch in the input mechanical power and output electrical power in case of synchronous generator and vice versa in case of synchronous motor. However, in steady state the input mechanical power and output electrical power should be equal and in order to enforce this speed governors are used. If the output electrical power requirement is more than the input mechanical power then the rotor speed of the synchronous machine will decrease and this decrease will cause the speed governor to increase the input mechanical power to the generator so as make the input mechanical power exactly equal to output electrical power. By: Dr. B. Kalyan Kumar     Date: 2012-07-20

 Question: what is generator capability curve?what are the steps to construct it.how can we calculate reactive power limits at a particular load. By: sunil     Date: 2012-07-25 The co-ordinator will post his answer

 Question: what happens to the load angle when the load on an alternator is gradually increased?does the speed decrease to transfer power from rotating mass to load? how does the alternator regain its stable operating condition? By: Rahul Roy     Date: 2012-08-09 The co-ordinator will post his answer

 Question: what will happen to the operation of an alternator if the load is increased gradually assuming that the mechanical input to it remains unchanged,i.e. the governor doesnt change the input to alternator? By: Rahul Roy     Date: 2012-08-09 The co-ordinator will post his answer

 Question: Dear Sir kindly please explain the concept of SCR and machine reactance with system stability in practical manner. By: shiva     Date: 2012-10-25 The co-ordinator will post his answer

 Question: Dear Sir, I am doing simulations in ETAP for transient stability studies. I want to know : What is the absolute rotor angle limit of syn. machines ? As I know, at 180 degree pole slipping occurs...If the angle crosses, 180 degree, does our system come back to stable state ? By: Mithun Chandran     Date: 2012-11-22 The co-ordinator will post his answer

 Question: what is the difference between active power and reactive power? (please give physical significance) By: upendra yadav     Date: 2013-01-11 The co-ordinator will post his answer

 Question: Sir , What is the difference between isochronous and droop speed mode of speed governor operation ?? By:     Date: 2013-02-09 The co-ordinator will post his answer

 Question: Is the equal area criterion applicable for finding the initial speed at which an alternator should be run so that it attains synchronism on switching the breaker.In other ways how can one find the maximum slip frequency limit for synchronization of generator using equal area criterion or otherwise? By: Nitish     Date: 2013-02-11 The co-ordinator will post his answer

 Question: how to include various FACTS device in multimachine power system for small signal stability improvement? which equations of chapter 6 will change? what will be the input signal to the facts controller? By: Gopi     Date: 2013-03-05 The co-ordinator will post his answer

 Question: A 300 MVA, 34.5 Y/138 kV  transformer is protected by differential relays with taps. Select CT ratios, CT connections, and relay tap settings. Also determine currents in the transformer and in the CTs at rated conditions. Assume that the available relay tap settings are 5:5, 5:5.5, 5:6, 5:7 By: robin     Date: 2013-03-08 The co-ordinator will post his answer
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