POWER SYSTEM OPERATION & CONTROL. Instructor: Dr. A. M. Kulkarni. Page 2. Module 1 Introduction. Lecture 1 Modern Power Systems. Page 3. Page 4. Power System Operation and Control is a comprehensive text designed for an undergraduate course in electrical engineering. Written in a simple and. 𝗣𝗗𝗙 | On Jan 1, , C. R. Balamurugan and others published Power System Operation and Control.
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CLASS NOTES ON POWER SYSTEM OPERATION AND CONTROL 3. F OREWORD BY THE AUTHOR Modern power system is a complex system, spread over. Lecture #2. Introduction to Power System. Operation and Control using ARISTO. Davood Babazadeh. Wollenberg, Bruce F. “Power System Operation and Control”. The Electric Power Engineering Handbook. Ed. L.L. Grigsby. Boca Raton: CRC Press LLC,
The power system has also seen new emerging trend in its technology, operation and planning. The issues such as, reactive power and active power control, angle stability and voltage stability, inter-area power transfer, power quality, automatic generation and frequency control for multi-machine system, reliability evaluation, operation in competitive environment, are important factors in operation and control of the power system. Generation, transmission, distribution, and loads make up the fundamental structure of a power system.
Generators, substations, transmission circuits, transformers, circuit breakers, metering, demand, load, are the main physical devices of an electric power system. Voltage, current, power, energy, frequency, and impedance are the fundamental terms used in power technology. The operation of power system needs proper coordination between these devices such that the fundamental variables of the system remain within desired limits. Average value of the power at a month for a different time periods are calculated and plotted in the graph which is known as monthly load curve.
What is yearly load curve? It is obtained from monthly load curve which is used to find annual load factor. What is connected load? It is the sum of continuous ratings of all the equipments connected to supply systems.
What is Maximum demand? It is the greatest demand of load on the power station during a given period.
What is Demand factor? It is the ratio of maximum demand to connected load. What is Average demand? The average of loads occurring on the power station in a given period day or month or year is known as average demand.
What is Load factor? The ratio of average load to the maximum demand during a given period is known as load factor. What is Diversity factor? The ratio of the sum of individual maximum demand on power station is known as diversity factor. What is Capacity factor? This is the ratio of actual energy produced to the maximum possible energy that could have been produced during a given period. What is Plant use factor? It is the ratio of units generated to the product of plant capacity and the number of hours for which the plant was in operation.
What is Load duration curve? When the load elements of a load curve are arranged in the order of descending magnitudes the curve then obtained is called load duration curve.
U IT-II 1. What is the major control loops used in large generators? The major control loops used in large generators are 1. What is the use of secondary loop?
A slower secondary loop maintains the fine adjustment of the frequency, and also by reset action maintains proper MW interchange with other pool members.
This loop is insensitive to rapid load and frequency changes but focuses instead on drift like changes which take place over periods of minutes. AVR loop is much faster than the ALFC loop and therefore there is a tendency, for the AVR dynamics to settle down before they can make themselves felt in the slower load frequency control channel. What is the diff. Large signal analysis is used where voltage and power may undergo sudden changes of magnitude that may approach percent of operating values.
Usually this type of analysis leads to differential equations of non-linear type. Small signal anaysis is used when variable excursions are relatively small, typically at most a few percent of normal operating values. What is the exciter? The exciter is the main component in AVR loop. It delivers the DC power to the generator field. It must have adequate power capacity and sufficient speed of response rise time less than 0.
What is the function of AVR? The basic role of the AVR is to provide constancy of the generator terminal voltage during normal, small and slow changes in the load. Explain about static AVR loop? In a static AVR loop, the execution power is obtained directly from the generator terminals or from the station service bus.
The AC power is rectified by thyristor bridges and fed into the main generator field via slip rings. Static exciters are very fast and contribute to improved transient stability.
Write the static performance of AVR loop? The AVR loop must regulate the terminal V to within required static accuracy limit. Have sufficient speed of response. Be stable. What is the dis. How is to be eliminated? High loop gain is needed for static accuracy but this causes undesirable dynamic response, possibly instability. What are the effects of generator loading in AVR loop? Added load does not change the basic features of the AVR loop, it will however affect the values of both gain factor Kf and the field constant.
High loading will make the generator work at higher magnetic saturation levels. This means smaller changes in E for incremental increases in if, translating into the reduction of KF. This circumstance permits the formation of transient stator currents the existence of which yields a lower effective field induction.
What are the functions of ALFC? The ALFC also helps to keep the net interchange of power between pool members at predetermined values. Control should be applied in such a fashion that highly differing response characteristics of units of various types are recognized. Also unnecessary power output changes should be kept at a minimum in order to reduce wear of control valves. Specify the dis. The ALFC loop will main control only during normal changes in load and frequency. It is typically unable to provide adequate control during emergency situations, when large MW imbalances occur.
How is the real power in a power system controlled? The real power in a power system is being controlled by controlling the driving torque of the individual turbines of the system. What is the need for large mechanical forces in speed-governing system? Very large mechanical forces are needed to position the main valve against the high stream pressure and these forces are obtained via several stages of hydraulic amplifiers U IT-III Reactive Power -Voltage Control 1.
What are the sources of reactive power? How it is controlled? The sources of reactive power are generators, capacitors, and reactors. These are controlled by field excitation. Give some excitation system amplifier. The excitation system amplifiers are, a Magnetic amplifier b Rotating amplifier c Modern electronic amplifier. When is feedback stability compensation used? This conflicting situation is resolved by adding feedback stabling compensation to the AVR loop.
Give the characteristics of line compensators? The characteristics of line compensators are, a. Ferranti effect is minimized. Under excited operation of synchronous generator is not required. What is known as bank of capacitors?
How it is adjusted? When a number of capacitors are connected in parallel to get the desired capacitance, it is known as bank of capacitors. The present operating point of the system is called base point. Define participation factor? The change in generation required to meet power demand is called as participation factor.
Define hydrothermal scheduling problem? The objective is to minimize the thermal generation cost with the constraints of water availability.
Define Uncommitment? Commitment of minmum generator to meet the required demand. Define spinning reserve? It is the term describe the total amount of generation availability from all units synchronized on the system.
What is meant by scheduled reserve? These include quick start diesel turbine units as well as most hydro units and pumped storage hydro units that can be brought online, synchronized and brought up to full capacity quickly.
What are the thermal unit constraint? Minimum up time, minimum down time crew constraints. Define minimum up time? Once the unit is running, it should not be turned off immediately. Define min. Once the unit is decommited, there is a minimum time before it can be recommended. Define crew constraints? If a plant consist of two or more units, all the units cannot be turned on at the same time since there are not enough crew members to attend both units while starting up. What are the two approaches to treat a thermal unit to operating temperature?
The first allow the unit boiler to cool down and then heat backup to operating temperature in time for a scheduled turn on. The second requires that sufficient energy be input to the boiler to just maintain operating temperature. What are the techniques for the solution of the unit commitment problem? Priority list method dynamic programming Lagrange relation What are the assumptions made in dynamic programming problem? A state consists of an array of units with specified units operating and the rest of the time.
The startup cost of a unit is independent of the time it has been offline. There are no costs for shutting down the units. Define long range hydro scheduling problem?
The problem involves the long range of water availability and scheduling of reservoir water releases. For an interval of time that depends on the reservoir capacities. What are the optimization technique for long range hydro scheduling problem? Dynamic programming composite hydraulic simulation methods statistical production cost. Define short range hydro scheduling problem? It involves the hour by hour scheduling of all generators on a system to achieve minimum production condition for the given time period.
Define system blackout problem? If the process of cascading failures continues, the entire system of it may completely collapse. This is referred as system blackout. What is meant by cascading outages? If one of the remaining lines is now too heavily loaded, it may open due to relay action, thereby causing even more load on the remaining lines.
This type of process is often termed as cascading outage. U IT-V 1. What are the functions of control center? System monitoring contingency analysis security constrained optimal power flow.
What is the function of system monitoring? System monitoring provides upto date information about the power system. Define scada system?
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. What are the states of power system? Normal state alert mode contingency mode emergency mode. Define normal mode? The system is in secure even the occurrence of all possible outages has been simulated the system remain secure is called normal mode.
Define alert mode? The occurrence of all possible outages the system does not remain in the secure is called alert mode. What are the distribution factors? Line outage distribution factor, generation outage distribution factor. Define state estimation? 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.
Define max. The objective is to maximize the probability that estimate the state variable x, is the true value of the state variable vector i. Define weighted least-squares criterion?
The objective is to minimize the sum of the squares of the weighted deviations of the estimated measurements z, from the actual measurement. Define minimum variance criterion? 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. Define must run constraint?
Some units are given a must run status during certain times of the year for reason of voltage support on the transmission network. Define fuel constraints? A system in which some units have limited fuel or else have constraints that require them to burn aspecified amount of fuel in a given time. What are the assumptions made in priority list method? 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.
State the adv of forward DP approach?
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. State the dis. 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. What are the known values in short term hydro scheduling problem?
What is meant by telemetry system? The states of the system were measured and transmitted to a control center by means of telemetry system. What are the functions of security constraints optimal power flow? In this function, contingency analysis is combined with an optimal power flow which seeks to make changes to the optimal dispatch of generation.
As well as other adjustments, so that when a security analysis is run, no contingency result in violations. Define the state of optimal dispatch? 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. Define post contingency?