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PowerWorld -Power Systems operation & control -- Animation of mechanical-hydraulic speed governor for power generator


1.Two power systems A and B are operating in parallel. If system A increases its generation to deliver 100 MW to system B, what will be the effect if system B does not reduce its generation simultaneously?

  1. frequency will increase
  2. frequency of both A and B will decrease
  3. frequency will remain unchanged.

Ans: (a)

  1. Governors for controlling the speed of power generation units provide

  1. A flat speed -load characteristics
  2. An increase of speed with increasing load
  3. A decrease of speed with increasing load

Ans. c

  1. When two identical a.c generating units are operated in parallel on governor control, and one machine has a 5% governor droop and the other a 10 % droop , the machine with the greater governor droop will

  1. Tend to take the greater portion of load changes
  2. Share load equally with the other machine
  3. Tend to take the lesser portion of load changes.

Ans. c

  1. On load-frequency control installations, error signals are developed proportional to the frequency error. If frequency declines , the error signal will act to

  1. Increase prime move input to the generators
  2. Reduce prime mover input to the generators
  3. Increase generator voltages

Ans. a

  1. When inter-connected power systems operate with tie-line bias, they will respond to

  1. Frequency changes only
  2. Both frequency & tie -line load changes
  3. Tie-line load changes only

  1. Power system A is operating in parallel with other power systems and has a frequency bias of 50 MW per 0.1 Hz. For a loss of generation in one of the interconnected systems which results in a frequency drop of 0.03 Hz , power system A should

  1. Provide 30 MW of support
  2. Not be affected
  3. Provide 15 MW of support

Ans. c

  1. Area control error is given by ACE = (To -T1) - 10 .B. (FO-F1), where

ACE- area control error

To -scheduled net interchange

T1- Actual net interchange

Fo- desired frequency, Hz

F1-actual frequency, Hz

B- Area bias, MW/one-tenth Hz

If scheduled net interchange To = 200 MW into the system, actual net interchange T1 =180 MW into the system, Fo = 50 Hz, F1= 49.9 Hz, B= 150 MW/0.1 Hz, then the ACE is

  1. +150 MW
  2. zero
  3. +170 MW
  4. -130 MW

  1. If frequency bias is set too low, an interconnected power system will respond to troubles in adjacent systems with

  1. More than its share of bias response
  2. Correct bias response
  3. Less than its share of bias response

  1. If a power system operates at an average frequency of less than 50 Hz,

  1. No time error will accumulate
  2. There will be a slow accumulated time error
  3. There will be a fast accumulated time error.

Ans. b

  1. When a power system operator observes an accumulated time error, he should correct it by

  1. Increasing generation on his system
  2. ]reducing generation on his system
  3. c0-ordinating time error with other interconnected systems

Ans. c

 Integrated operation of power systems