Important Short Questions and Answers: Computer Control of Power Systems

COMPUTER CONTROL OF POWER SYSTEMS

1. What are the functions of control center?

^Ø   System monitoring contingency analysis security constrained optimal power flow.

2. What is the function of system monitoring?

^Ø   System monitoring provides upto date information about the power system.

3. Define SCADA system?

^Ø   It stands for supervisory control and data acquisition system, allows a few operators to monitor the generation and high voltage transmission systems and to take action to correct overloads.

4. What are the states of power system?  Define normal mode?

^Ø   Normal state alert mode contingency mode emergency mode.

^Ø   The system is in secure even the occurrence of all possible outages has been simulated the system remain secure is called normal mode.

5. Define alert mode?

^Ø   The occurrence of all possible outages the system does not remain in the secure is called alert mode.

6. What are the distribution factors?

^Ø   Line outage distribution factor, generation outage distribution factor.

7. Define state estimation?

^Ø   State estimation is the process of assigning a value to an unknown system state variable based on measurements from that system according to some criteria.

8. Define max. likelihood criterion?

^Ø   The objective is to maximize the probability that estimate the state variable x, is the true value of the state variable vector (i.e, to maximize the P(x)=x).

9. Define weighted least-squares criterion?

^Ø   The objective is to minimize the sum of the squares of the weighted deviations of the estimated measurements z, from the actual measurement.

10.          Define minimum variance criterion?

^Ø   The objective is to minimize the expected value of the squares of the deviations of the estimated components of the state variable vector from the corresponding components of the true state variable vector.

11.            Define must run constraint?

^Ø   Some units are given a must run status during certain times of the year for reason of voltage support on the transmission network.

12.            Define fuel constraints?

^Ø   A system in which some units have limited fuel or else have constraints that require them to burn a specified amount of fuel in a given time.

13.            What are the assumptions made in priority list method?

^Ø   No load cost are zero unit input-output characteristics are linear between zero output and full load there are no other restrictions startup cost are affixed amount.

14.            State the adv of forward DP approach?

^Ø   If the start up cost of a unit is a function of the unit is a function of the time it has been offline, then a forward dynamic program approach is more suitable since the previous history of the unit can be computed at each stage.

15.            State the dis.adv of dynamic programming method?

^Ø   It has the necessity of forcing the dynamic programming solution to search over a small number of commitment states to reduce the number of combinations that must be tested in each period.

16. What are the known values in short term hydro scheduling problem? What is meant by telemetry system?

^Ø   The load, hydraulic inflows & uit availabilities are assumed known.

^Ø   The states of the system were measured and transmitted to a control center by means of telemetry system.

17.            What are the functions of security constraints optimal power flow?

^Ø   In this function, contingency analysis is combined with an optimal power flow which seeks to make changes to the optimal dispatch of generation.

^Ø   As well as other adjustments, so that when a security analysis is run, no contingency result in violations.

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18.            Define the state of optimal dispatch?

^Ø   This is the state that the power system is in prior to any contingency. It is optimal with respect to economic operation but may not be secure.

19.            Define post contingency? Define secure dispatch?

^Ø   This is the state of the power system after a contingency has occurred.

^Ø   This is state of the power system with no contingency outages, but with correction to the operating parameters to account for security violations.

20.            What are the priorities for operation of modern power system?

^Ø   Operate the system in such a way that power is delivered reliably.

^Ø   Within the constraints placed on the system operation by reliability considerations, the system will be operated most economically.

21.            What is meant by linear sensitivity factor?

^Ø   Many outages become very difficult to solve if it is desired to present the results quickly.

^Ø   Easiest way to provide quick calculation of possible overloads is linear sensitivity factors.

22.            What are linear sensitivity factors?

^Ø   Generation shift factors line outage distribution factors.

23. What is the uses of line distribution factor?

^Ø It is used to apply to the testing for overloads when transmission circuits are lost.

24.            What is meant by external equvalencing?

In order to simplify the calculations and memory storage the system is sub divided into 3 sub systems called as external equvalencing