SNS COLLEGE OF ENGINEERING
Kurumbapalayam(Po), Coimbatore – 641 107
Accredited by NAAC-UGC with ‘A’ Grade
Approved by AICTE & Affiliated to Anna University, Chennai
INTERNAL ASSESMENT EXAMINATIONS – III ANSWER KEY
COURSE: B.E – EEE
EE6603 – POWER SYSTEM OPERATION AND CONTROL
Class: VI SEM EEE
PART A
1.List the various constraints in economic dispatch problem.
Primary constraints (equality constraints)
Secondary constraints (inequality constraints)
Spare Capacity Constraints
Thermal Constraints
Bus voltage and Bus angle Constraints
2.Compare economic dispatch and unit commitment.
Economic dispatch with load schedule for one day is unit commitment
3. Explain Incremental fuel cost curve
4. Explain penalty factor.
Penality factor
of the loadi and is given
by
5. Write the coordination equation for (i) With loss (ii) Without loss.
(With losses)
6.What are the advantages of using Participation factor?
When load changes are small, it is possible to move from one optimal schedule to another using
PARTICIPATING FACTORS.
7.List the factors that affects the power system security
1.Transmission line outages
2. Generation unit failures
8. What is meant by network topology?
Preventive or corrective actions to improve power systems' operating states mainly concern power
generation rescheduling, load-shedding and tap modifications of in-phase or phase-angle transformers.this
can be achieved by rescheduling of network topology.
9.Comparison between power system reliability and security?
Reliability ensures the system perfomances to be good
System security ensure parameter should not violate the limit
10 Define state estimation.
State Estimation is to generate data from the partial data available .given certain measurements,
Find the states (voltages and angles) of the system
PART B
11
.
(a)
i)
Explain with neat flow chart the procedure for finding solution for unit commitment problems
using forward dynamic programming method.
Forward Dynamic Programming Approach
The dynamic programming algorithm can be run back ward in time starting from the final
hour to be studied back to the initial hour. Conversely, the algorithm can be run forward
in time from the initial hour to the final hour. Dynamic programming sub-divide the 24-h
day into discrete intervals .
The unit commitment procedure then searches for the most economic feasible
combination of generating units to serve the forecast load and spinning reserve
requirement of the system at each interval of the load cycle. In unit commitment problem
the DP is based on enumeration scheme and priority list methods. For example, if we
have four units, N = 4, then 15 possible combinations for each interval are
(b)
i)
OR
Obtain the priority list of unit commitment using full load average production cost for the given
data for the load level of 900 MW.
F1 = 392.7 + 5.544 P1 + 0.001093 P12
F2 = 217 + 5.495 P2 + 0.001358 P22
F3 = 65.5 + 6.695 P3 + 0.004049 P32 ,
P1, P2, P3 in MW
Generation limits : 150 < P1 <600 MW;100 < P2 < 400 MW 50 < P3 < 200 MW
There are no other constraints on system operation. Obtain an optimum unit commitment table
Unit 1 and 2 are running
12
.
(a)
i)
Derive coordination equation for economic dispatch including losses, in the power system
Give steps for economic dispatch calculation. Neglecting losses
(b)
i)
The fuel inputs per hour of plants 1 and 2 are given as
2
1
2
2
Determine the economic operating schedule and the corresponding cost of generation if the
maximum and minimum loading on each unit is 100 MW and 25 MW. Assume the transmission
losses are ignored and the total demand is 180 MW. Also determine the saving obtained if the
load is equally shared by both the units.
COST OF GENERATION 1 = 5255.8 RS/HR
COST OF GENERATION 2 = 4958.64 RS/HR
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NET SAVING 0.5559 RS/HR
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(a)
(i)
Consider the following three units:
IC1 = 7.92 + 0.003124 PG1
IC2 = 7.85 + 0.00388 PG2
IC3 = 7.97 + 0.00964 PG3
PD = 850 MW
PG1 = 392.2 MW, PG2 = 334.6 MW, PG3 = 122.2 MW
Determine the optimum schedule if the load is increased to 900 MW by using Participation
Factor method.
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PG1 =416.7 MW ;PG2 =353.6 MW PG3=129.7MW
(b)
(i)
Discuss in detailed about Contigency analysis
Security’ implies the ability of the system to operate within system constraints (on
bus voltage magnitudes, current and power flow over the lines) in the event of
outage (contingency) of any component (generator or transmission line)
Any power system, the operating point of the system changes quite frequently
with change is loading/generating conditions.With the change in system
operating conditions, the contingency analysis exercise needs to be carried out
again at the new operating point
In any power system, the operating point of the system changes quite frequently
with change is loading/generating conditions.With the change in system
operating conditions, the contingency analysis exercise needs to be carried out
again at the new operating point. Thus, for proper monitoring of system security,
a large number of outage cases need to be simulated repeatedly over a short
span of time. Ideally,
these outage cases should be studied with the help of full AC load flow solutions.
However, analysis of thousands of outage cases with full AC power flow
technique will involve a significant amount of computation time and as a result, it
might not be possible to complete this entire exercise before the new operating
condition emerges. Therefore, instead of using full non-linear AC power flow
analysis, approximate, but much faster techniques based on linear sensitivity
factors are used to estimate the post contingency values of different quantities of
interest
there are two types of sensitivity factors and these are:
a. Generation outage sensitivity factor (GOSF)
b. Line outage sensitivity factor (LOSF)
GOSF relates the approximate change in power flow in line ‘i-j’ (i.e. between bus
‘i’ and ‘j’) dueto the outage of generator at bus ‘k’, whereas LOSF helps to
calculate the approximate change in power flow in line ‘i-j’ due to outage of line
‘m-n’.
The generation outage sensitivity factor is defined by,
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line outage distribution factors are also defined similarly. The LOSF is defined
by
(ii)
Illustrate the importance of WLSE and Derive its necessary conditions
Measurement Function
•Let z denote the measurement and state value x denote the quantities being estimated.
•Using the circuit (Kirchoff’s) law, we can write the ‘true’ value of the measurement as,
z true = h(x)
where h(.) is a known function of the state value x related the to the measurement value z
Measurement Error
•The true value of measurement may not be the same as what we measured.
•Let e denotes the error (or residual) in the meter, we can write,
e = z - z true = z - h(x)
•We then have the measurement function as follow.
z = h(x) + e
Measurement Function: Matrix Form
•Assume that we have m measurements in the system, we can write.
z = h(x) + e
•Where
–z is a vector of size (m×1)
–x is a vector of size (n×1)
–h(x) is a vector of size (m×1)
–e is a vector of size (m×1)
Objective Function of WLSE
•From
and z = h(x) + e. •Let W be the diagonal matrix with elements {wj}, we can write the
objective function in a matrix form as follow.
Minimize f = eTWe = (z - h(x)) T W(z - h(x))
Necessary Condition of WLSE
•From, f = (z - h(x))TW(z - h(x)).
•We write f = zTWz - 2h(x)TWz + h(x)TWh(x).
•Using necessary condition,
•We can then find the WLS estimate, x̂ from the above equation.
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(a)
(i)
Elaborate about State estimation with respect to power system? Explain briefly the maximum
likelihood weighted least square estimation.
State estimation includes additional functions as it is illustrated in Figure 1. Note that the basic
state estimation algorithm is suplemented with a number of supporting functions, such as
topology processor,data preprocessing, observabilioty analysis, bad data rejection, parameter
estimation and possibly remote calibration. Here we will focus on the basic state estimation
algorithm. The state estimation is a mathematical procedure by which the state of an electric
power system is extracted from a set of measurements. Traditionally, the measurements are P, Q
and V (real power, reactive power and voltage magnitude).
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(b)
(i)
Draw the state transition diagram and explain the various operating state of a power system and
the associated control actions.
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15
(a)
(b)
(i)
What is EMS? What are its major functions in power system operation and control?
(i)
Explain the hardware components and functional aspects of SCADA system using a functional
block diagram. Also discuss the functions of SCADA.
SCADA – Architecture
SCADA – Process,logging
SCADA as a System
User Interface – Human Machine Interface (HMI)
Critical Functions of SCADA
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