Tutorial LFS

Computer Methods in Power System Analysis (2710711)

Tutorial on Load Flow Studies Note: EN = Enrollment No. For example, if your Enrollment No. is 25

0.0EN=0.025

→

1. Fig. shows the single line direction of a sample 3-bus power system. Data for this system are given in the following tables.

1 3

2

Table 1: Scheduled generation and loads and assumed bus voltage for system (Base MVA = 100) Bus code

Bus Voltage

1(slack bus) 2 3

Generation MW MVAR

1.05 +  j0.0

‐

‐

‐ ‐

50 0

30 0

Load MW 0 305.6 138.6

MVAR 0 140.2 45.2

Table 2: Line impedances Bus Code 1‐2 1‐3 2‐3

Impedance 0.0EN +  j0.04 0.01 +  j0.03 0.0125 +  j0.0EN

Using the Gauss-Seidel method, determine the voltage at bases 2 & 3. Perform 1 iteration only. Using updated voltage at the end of iteration 1, find power flow in line connected between bus-1 and  bus-2

M.E. Electrical (Sem‐1)

G.H.Patel College of Engg. of  Engg. & Tech., Vallabh Vidyanagar

Computer Methods in Power System Analysis (2710711)

2. The following is the system data for a load flow solution: The line admittances:

Bus Code

Admittance

1‐2 1‐3 2‐3

2 – j8.0 1 – j4.EN 0.666 – j2.662

2‐4 3‐4

1 – j4.EN 2 – j8.0

The schedule of active and reactive powers: Bus Code 1 2

P

Q 

‐

‐

3

0.5 0.4

0.2 0.3

4

0.3

0.1

V 1.06 1 + j0.0

Remarks Slack bus PQ bus

1 + j0.0

PQ bus

1 + j0.0

PQ bus

Determine the voltages at the end of first iteration using Gauss-Seidel method. Take

α =

3. Following is the data for load flow solution of four bus system as shown in fig:

1

2 -j5.0

-j5.0

-

  -j5.0

3 The line admittances are as shown in fig. The schedule of active and reactive powers is as follows:

Bus

P

Q

V

Remarks

1 2 3

‐

‐

1 + j0

1 3.5

0.1 0.EN

4

1

0.2

‐ ‐ ‐

Slack bus P‐Q bus P‐Q bus P‐Q bus

Find the voltages at the end of first iteration using G-S method. M.E. Electrical (Sem‐1)

G.H.Patel College of Engg. & Tech., Vallabh Vidyanagar

1.6

Computer Methods in Power System Analysis (2710711)

4. For the system shown in the fig using NR method calculate voltage mag. and phase angle at bus o o 2 after first iteration (assume V2  = 1, δ2  = 0)

100

Z12 = 0.EN + G

50 Mvar V1 = 1.0, base MVA = 100

5. A 3-bus power system has three transmission line connected between bus 1, 2& 3. Each line has series reactance of j0.11 pu. Series resistance & shunt admittance of each line is negligible. The  bus data is given below. BUS 1 2 3

TYPE slack P‐V P‐Q 

PL 1 0 1.EN

Q L 0.5 0 0.EN

PG

Q G

‐

‐ ‐

V 1.03 + j0.0 1.03

0

‐

1.5 0

2 P1 slack 

P3 For bus-2, the maximum and minimum reactive power limits are 0 and 0.8 resp. a) Form YBUS and find B’ & B” matrices of FDLF method.  b) Find P2, P3 & Q3 for initial condition, assuming V3 = 1.0 pu and δ3 &δ2 = 0 . c) Form general equation of FDLF method. d) Perform one iteration & calculate P2, P3 & Q3. e) Find line losses and Total generation at Bus-1 and Bus-2.

M.E. Electrical (Sem‐1)

G.H.Patel College of Engg. & Tech., Vallabh Vidyanagar