PSO Manualmmm

Power Distribution Laboratory Lab. Manual

Handout no. 1

NameReg. NoMarks / Grade

EXPERIMENT # 1

ETAP:

Objective:

To learn and understand the fundamentals of ETAP (Load Flow Case Editor) Toolbox for Power System Simulation.

Theory:

ETAP; Electrical Transient Analyser Program offers a suite of fully integrated Electrical Engineering software solutions including arc flash, load flow, short circuit, transient stability, relay coordination, cable ampacity, optimal power flow, and more. Its modular functionality can be customized to fit the needs of any company, from small to large power systems.

ETAP load flow calculation program calculates bus voltages, branch power factors, currents, and power flows throughout the electrical system. ETAP allows for swing, voltage regulated, and unregulated power sources with unlimited power grids and generator connections. This load flow calculation software is capable of performing analysis on both radial and loop systems. ETAP allows you to select from several different load flow calculation methods in order to achieve the most efficient and accurate results.

Copyrights © Hasan Erteza Gelani,Lecturer EE Dept,UET Lhr Fsd Campus. This material is exclusively for the use of students studying in EE Dept UET Lhr,Fsd Campus.


Lab Exersice:

You are required to draw any network of your own will as a practice of network design; You may draw the network shown above.

Q1. Please go through the case editor of load flow toolbar and state what you have learnt from the case editor.

_____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Q2. Sometimes we get no result of load flow analysis; what could be the reasons?

__________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________



Handout no. 2


EXPERIMENT # 2

Gauss Siedel in ETAP

Objective:

To understand the simulation techniques involved in simulating a Power Network and analysing using Gauss Siedel in ETAP.

Theory:

ETAP Load Flow permits the user to choose from three different methods (Gauss-Seidel, Newton-Raphson and Fast Decoupled) in order to achieve the best calculation efficiency.

Gauss Siedel is a mathematical technique for the analysis of power system by employing an iterative method. The power flow equations are nonlinear algebraic equations and their solution can be derived from the method of successive iterations that Gauss Siedel adopts.

Lab Exersice:

You are required to make any interconnected network of your choice(like the one shown below) and show it to the instructor. Then run the system using Gauss Siedel equations from Load Flow Case Editor and generate the report. Attach the report with your handout.

Save your network because you are required to run the same using other load flow techniques and compare the results.



Q1. Discuss the significance of Gauss Siedel in power flow analysis.__________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Q2. We get load flows in ‘red colour’ after analysis is done; can we also get current/voltage measurements in the similar manner? How?__________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________



Handout no. 3


EXPERIMENT # 3

Newton Raphson ETAP

Objective:

To understand the simulation techniques involved in simulating a Power Network and analysing using Newton Raphson in ETAP.

Theory:

The goal of a power flow study is to obtain complete voltage angle and magnitude information for each bus in a power system for specified load and generator real power and voltage conditions. Once this information is known, real and reactive power flow on each branch as well as generator reactive power output can be analytically determined. Due to the nonlinear nature of this problem, numerical methods are employed to obtain a solution that is within an acceptable tolerance.

The solution to the power flow problem begins with identifying the known and unknown variables in the system. The known and unknown variables are dependent on the type of bus. A bus without any generators connected to it is called a Load Bus. With one exception, a bus with at least one generator connected to it is called a Generator Bus. The exception is one arbitrarily-selected bus that has a generator. This bus is referred to as the slack bus.

In the power flow problem, it is assumed that the real power PD and reactive power QD at each Load Bus are known. For this reason, Load Buses are also known as PQ Buses. For Generator Buses, it is assumed that the real power generated PG and the voltage magnitude |V| is known. For the Slack Bus, it is assumed that the voltage magnitude |V| and voltage phase Θ are known. Therefore, for each Load Bus, both the voltage magnitude and angle are unknown and must be solved for; for each Generator Bus, the voltage angle must be solved for; there are no variables that must be solved for the Slack Bus. In a system with N buses

and R generators, there are then unknowns.

In order to solve for the unknowns, there must

be equations that do not introduce any new unknown variables. The



possible equations to use are power balance equations, which can be written for real and reactive power for each bus. The real power balance equation is:

where is the net power injected at bus i, is the real part of the element in the bus admittance matrix YBUS corresponding to the ith row and kth column, is the imaginary part of the element in the YBUS corresponding to theith row and kth column and is the difference in voltage angle between the ith and kth buses. The reactive power balance equation is:

where is the net reactive power injected at bus i, and .

Equations included are the real and reactive power balance equations for each Load Bus and the real power balance equation for each Generator Bus. Only the real power balance equation is written for a Generator Bus because the net reactive power injected is not assumed to be known and therefore including the reactive power balance equation would result in an additional unknown variable. For similar reasons, there are no equations written for the Slack Bus.

There are several different methods of solving the resulting nonlinear system of equations. The most popular is known as the Newton–Raphson method. This method begins with initial guesses of all unknown variables (voltage magnitude and angles at Load Buses and voltage angles at Generator Buses). Next, a Taylor Series is written, with the higher order terms ignored, for each of the power balance equations included in the system of equations . The result is a linear system of equations that can be expressed as:

where and are called the mismatch equations:

and is a matrix of partial derivatives known as a Jacobian:

.


http://en.wikipedia.org/wiki/Jacobian_matrix_and_determinant


The linearized system of equations is solved to determine the next guess (m + 1) of voltage magnitude and angles based on:

The process continues until a stopping condition is met. A common stopping condition is to terminate if the norm of the mismatch equations is below a specified tolerance.

A rough outline of solution of the power flow problem is:

1. Make an initial guess of all unknown voltage magnitudes and angles. It is common to use a "flat start" in which all voltage angles are set to zero and all voltage magnitudes are set to 1.0 p.u.

2. Solve the power balance equations using the most recent voltage angle and magnitude values.

3. Linearize the system around the most recent voltage angle and magnitude values4. Solve for the change in voltage angle and magnitude5. Update the voltage magnitude and angles6. Check the stopping conditions, if met then terminate, else go to step 2.

Lab Exersice:

You are required to run the same network of previous lab session and run it using Newton Raphson from the Case Editor. Generate the report and attach it with the handout.

Q1. Compare the results of Gauss Siedel and Newton Raphson and state below what you have learnt.



Handout no. 4


EXPERIMENT # 4

Fast Decoupled in ETAP:

Objective:

To understand the simulation techniques involved in simulating a Power Network and analysing using Fast Decoupled in ETAP.

Theory:

Fast Decoupled is a variation on Newton-Raphson that exploits the approximate decoupling of active and reactive flows in well-behaved power networks, and additionaly fixes the value of the Jacobian during the iteration in order to avoid costly matrix decompositions.

Fast Decoupled makes assumptions in Newton Raphson method and reduces the size of Jacobian and hence, lesser equations are to be solved and quick solution is gained.

Lab Exersice:

You are required to run the same network of previous lab session and run it using Fast Decoupled from the Case Editor. Generate the report and attach it with the handout.

Q1. State briefly the comparison between the three techniques by analysing their results.



Handout no. 5


EXPERIMENT # 5

Economic Dispatch

Objective:

To understand the concept of economic dispatch and make a MATLAB code for it.

Theory:

Economic dispatch is the short-term determination of the optimal output of a number of electricity generation facilities, to meet the system load, at the lowest possible cost, while serving power to the public in a robust and reliable manner. The Economic Dispatch Problem is solved by specialized computer software which should honour the operational and system constraints of the available resources and corresponding transmission capabilities.

The diagram above shows N units supplying Pload. They can deliver Pload at minimum cost by solving the problem using economic dispatch algorithm.



Lab Exersice:

You have studied in your class lecture how economic problem can be solved. You are required to solve any problem(by hand) on handout and write MATLAB code for it.



Handout no. 6


EXPERIMENT # 6

Lambda Iteration

Objective:

To understand the concept of Lambda Iteration and write Matlab code for it.

Theory:

Following is the Lambda Iteration algorithm:



Lab Exersice:

You are required to write the code for above algorithm; write your Matlab commands below:

Hint: Take help from Hadi Sa’adat.



Handout no. 7


EXPERIMENT # 7

Fault Analysis:

Objective:

To simulate a power system and observe the effect of short circuit on system parameters using ETAP.

Theory:

If a fault occurs in a power system; the magnitude of fault current is controlled by the percentage reactance at that point. The fault current is related to full load current by a factor of 100/%X. Therefore if the percentage reactance is low, the magnitude of the fault current will be high.

In this lab session you are required to simulate a simple circuit and observe what happens when a three phase fault occurs in a power system. The important thing to observe is the rise in the magnitude of current during the fault.

ETAP short circuit analysis software analyzes the effect of 3-phase, 1-phase, line-to-ground, line-to-line, and line-to-line-to-ground fault currents on electrical power systems. The fault current calculation software simulates the total short circuit currents as well as the fault current contributions of individual motors, generators, and utility ties in the power system.

Lab Exersice:

You are required to simulate a comprehensive network of your campus; place a fault at any bus and check the results.

You are also required to attach the results with handout.

Q1. Why is there a huge rise in current during fault?



Q2. What happens to the voltage at fault point?

Handout no. 8




EXPERIMENT # 8

Transient Stability in ETAP

Objective:

To understand the concept of Transient Stability and plot the results after a disturbance strikes our system using ETAP.

Theory

The stability of a system refers to the ability of a system to return back to its steady state when subjected to a disturbance. As mentioned before, power is generated by synchronous generators that operate in synchronism with the rest of the system. A generator is synchronized with a bus when both of them have same frequency, voltage and phase sequence. We can thus define the power system stability as the ability of the power system to return to steady state without losing synchronism. Usually power system stability is categorized into Steady State, Transient and Dynamic Stability.

Steady State Stability studies are restricted to small and gradual changes in the system operating conditions. In this we basically concentrate on restricting the bus voltages close to their nominal values. We also ensure that phase angles between two buses are not too large and check for the overloading of the power equipment and transmission lines. These checks are usually done using power flow studies.

Transient Stability involves the study of the power system following a major disturbance. Following a large disturbance the synchronous alternator the machine power (load) angle changes due to sudden acceleration of the rotor shaft. The objective of the transient stability


http://nptel.iitm.ac.in/courses/Webcourse-contents/IIT-KANPUR/power-system/chapter_9/9_1.html#dynamic

http://nptel.iitm.ac.in/courses/Webcourse-contents/IIT-KANPUR/power-system/chapter_9/9_1.html#transient

http://nptel.iitm.ac.in/courses/Webcourse-contents/IIT-KANPUR/power-system/chapter_9/9_1.html#steady


study is to ascertain whether the load angle returns to a steady value following the clearance of the disturbance.

The ability of a power system to maintain stability under continuous small disturbances is investigated under the name of Dynamic Stability (also known as small-signal stability). These small disturbances occur due random fluctuations in loads and generation levels. In an interconnected power system, these random variations can lead catastrophic failure as this may force the rotor angle to increase steadily.

Lab Exersice:

You are required to redraw the network of previous lab session and run transient stability after assigning events for the occurrence and clearance of fault.

State your events below:

(Attach your network and plots for Generator’s parameters with the handout)



Handout no. 9


EXPERIMENT # 9

Transient Stability in Matlab(Exercise Handout 1)

Objective:

To understand the concept of Transient Stability by solving examples and writing Matlab code for their solution/verification.

Lab Exersice:

You are required to solve example 11.2 and 11.3 of Hadi Sa’adat and write their Matlab Code:

Handout no. 10




EXPERIMENT # 10

Load Frequency Control

Objective:

To understand the concept of LFC( Load Frequency Control) and simulate its control system using Matlab.

Theory:

Active power control is one of the important control actions to be perform to be normal operation of the system to match the system generation with the continuously changing system load in order to maintain the constancy of system frequency to a fine tolerance level. This is one of the foremost requirements in proving quality power supply. A change in system load cases a change in the speed of all rotating masses (Turbine – generator rotor systems) of the system leading to change in system frequency. The speed change form synchronous speed initiates the governor control (primary control) action result in the entire participating generator – turbine units taking up the change in load, stabilizing system frequency. Restoration of frequency to nominal value requires secondary control action which adjusts the load - reference set points of selected (regulating) generator – turbine units. The primary objectives of automatic generation control (AGC) are to regulate system frequency to the set nominal value and also to regulate the net interchange of each area to the scheduled value by adjusting the outputs of the regulating units. This function is referred to as load – frequency control (LFC).

The ALFC is to control the frequency deviation by maintaining the real power balance in the system. The main functions of the ALFC are to i) to maintain the steady frequency; ii) control the tie-line flows; and iii) distribute the load among the participating generating units.The control (input) signals are the tie-line deviation ∆Ptie (measured from the tieline flows), and the frequency deviation ∆f (obtained by measuring the angle deviation ∆δ). These error signals ∆f and ∆Ptie are amplified, mixed and transformed to a real power signal, which then controls the valve position. Depending on the valve position, the turbine (prime mover) changes its output power to establish the real power balance.

The complete block representation of LFC with all its components is shown below:



Lab Exersice:

You are required to simulate example 12.1 of Hadi Sa’adat using Simulink (MATLAB)



Handout no. 11


EXPERIMENT # 11

Automatic Voltage Control

Objective:

To understand the concept of AVR( Automatic Voltage Control) and simulate its control system using Matlab.

Theory

The voltage of the generator is proportional to the speed and excitation (flux) of the generator. The speed being constant, the excitation is used to control the voltage. Therefore, the voltage control system is also called as excitation control system or automatic voltage regulator (AVR).The complete block diagram representation is shown below:

Lab Exersice:

You are required to simulate example 12.6 of Hadi Sa’adat using Simulink (MATLAB)


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