98   Journal of Engineering, Mechanics and Architecture                      www. grnjournal.us  

 
 

AMERICAN Journal of Engineering,  
Mechanics and Architecture 

Volume 3, Issue 7, 2025 ISSN (E): 2993-2637 

 
  

Analysis Transient Stability and short circuit of IEEE 9 Bus System 

by Power World Simulator 
 

Wafeeqa Abdulrazak Hasan 

Southern Technical University, Technical College Basrah, Iraq 

 

Abstract: Transient stability is typically regarded as a vital aspect of electrical power system 

design and development. Investigating and understanding the power system's stability was the 

goal of this investigation. This study used the power world simulator to model and analyze 

transient stability on the IEEE-9 bus system. Furthermore, load flow investigations were 

conducted using the Newton-Raphson Method to ascertain the system's pre-fault state. Changes 

in the system's power angle and frequency were examined using a three-phase balanced fault. A 

dependable indicator for identifying power system flaws is frequency. In order to bring the 

system back to stability, an examination of the three-phase balanced fault's quick fault clearing 

time was also carried out. As a result, the system's protection mechanism ought to react quickly. 

This analysis suggests that load shedding and quick fault clearing techniques can be used to 

improve system stability.  

Keywords: Transient stability, three-phase balanced faults, IEEE-9 bus system, short circuit, 

Power World Simulator. 

 
 

1. Introduction 

In the field of electrical engineering nowadays, maintaining the integrity and stability of power 

systems becomes crucial. Maintaining stability and balance becomes increasingly difficult as 

these systems evolve and become more complicated. Due to sudden changes in load, operational 

transitions, and unanticipated malfunctions, these systems experience a variety of disturbances, 

underscoring the urgent need to restore stability and balance after such disruptions [1][2]. 

Electrical systems are said to be stable if they can maintain synchronization during normal 

operating conditions and then regain this balance after disruptions. There are three main types of 

system stability: dynamic stability, transient stability, and static stability [1][3]. The transient 

stability of systems, also known as temporary stability, is the main subject of this study. It 

describes the system's capacity to maintain synchronization during disruptions that occur before 

regulating devices take effect. To ascertain whether stability is jeopardized during this primary 

phase, transient stability is analyzed within a brief timescale equal to the initial system 

oscillation [1]. The initial state of the system as well as its status throughout the disturbance are 

critical factors in transient stability. Initial swing instability, which is caused by non-periodic 

fluctuations brought on by insufficient synchronizing torque, is the outcome of these 

disturbances, which change the way the system operates and leave it in a post-disturbance state 

different from its initial configuration [4]. In electrical systems, transient stability analysis is the 

study of how these systems behave and remain stable when subjected to brief (transient) 

disruptions. An essential component in assessing the performance and stability of electrical 

power networks is this analysis [5]. A system's Critical Clearing Time (CCT) is the longest 

period of time it can withstand shocks without becoming unstable [6]. The algebraic/differential 



 

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equations are solved using a methodical calculation process employing time domain simulation 

because transient stability is quite nonlinear. Newton Raphson's second technique can also be 

used to determine stability using the direct method[7]. Electrical currents and voltages fluctuate 

as a result of the system's equilibrium being upset by electrical disturbances such as breakdowns 

or variations in load. Understanding how the system responds to these disruptions and its 

capacity to quickly return to stability and balance is the goal of transient stability analysis.[5]. 

The pre-fault voltage magnitude must be known in order to perform transient stability analysis. 

Important details in the power flow research include the generator bus power flow, the power 

flow and losses in the transmission line, the bus voltage magnitude, the bus voltage phase angle, 

etc. [8]. The Newton-Raphson approach or the rapid de-coupled method can be used to extract 

pre-fault conditions from load flow. The reserve bus selection has no bearing on convergence in 

the Newton-Raphson approach. All unknown parameters are first estimated using this procedure 

[9]. The electrical power system is nearly interconnected in our day and age, so faults might 

happen and high-rate currents need to be interrupted before normal circumstances can be 

established. Both symmetrical and unsymmetrical flaws can occur in a variety of forms. The 

Three-phase or symmetrical faults are the most serious failures that cause the most disruption in 

network accessories [10].  

Fault is an undesirable and unexpected circumstance that results in equipment failure, which 

affects costs in addition to stressing the network. Blocking the excessive current flow is essential 

before causing any damage to any equipment. An undesirable circumstance that increases the 

network's stress level is called a fault in a distribution network. A very high current flow is the 

result of a malfunction, and it must be stopped before it destroys any network segments [10]. 

One computer application that focuses on examining and modeling electric power systems is 

called Power World Simulator. With the help of Power World Simulator, electrical engineers 

may build intricate models of electrical power systems and examine how they behave under 

various scenarios. The tool allows for the simulation of network operation, pregnancy 

distribution analysis, dynamic stability testing, and operating effects study. Drawing the system's 

electrical circuits and determining various physical characteristics, including voltage, current, 

and other pertinent data, are made possible by Power World Simulator's user-friendly graphical 

interface. [11]  

This work's investigation of the IEEE-9 bus system model's transient stability is its main goal, 

which the Power World Simulator technology was used to emulate. Transient stability refers to 

the system's capacity to maintain synchronization throughout the disruption and before the 

governors have a chance to take action. One swing's duration is the brief time frame within 

which the transient stability study is conducted. The purpose of this study is to determine 

whether or not the system becomes unstable during the initial swing. IEEE-9 bus power systems 

in both normal and abnormal operating conditions are used to test the proposed work.  

This paper's succeeding sections are organized as follows: A power flow analysis is described in 

Section 2. Methods employed in Section 3 to use the IEEE-9 bus system model to analyze 

transient stability and short circuit. Results from the IEEE-9 bus system model and simulation 

are presented and discussed in Section 4. The results are shown in Section 5. 

2. A Power Flow Studies 

A recognition of the pre-fault voltage magnitude is necessary for transient stability studies. The 

generator bus power flow, transmission line power flow and losses, bus voltage magnitude, bus 

phase angle, and other important data are all included in the power flow analysis [8]. Newton 

Raphson or rapid decoupled methods can be used to obtain pre-fault circumstances based on load 

flow analysis [9].  

2.1 Fast Decoupled Method 

In order to solve power flow-related difficulties, this approach is thought to be quick and 

effective. This approach is essentially a continuation of the Newton-Raphson method. Stott and 



 

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Alsac initially introduced this technique in 1974[12-14]. This method quickly became the most 

often used approach in power flow problems because it is based on the Newton-Raphson 

method, which makes computations much simpler and yields solid answers with fast 

convergence. This method yields quick algorithms for power problems by using polar 

coordinates and a few approximations. But occasionally, non-convergence is also the result of 

using specific approximations. Examples include situations where low voltages occur at certain 

busses and situations where resistance-to-reactance ratios are high. When approximations cause 

the solutions to not converge cleanly, one must make certain assumptions in order to simplify the 

Jacobian matrix [15]. 

2.2 Newton-Raphson Method 

This approach is named for Sir Isaac Newton and Raphson, who developed it. This approach 

uses an iterative process. This technique uses Taylor series to approximate nonlinear 

simultaneous equations into linear ones. But only the first order approximations of the Taylor 

series are enlarged. 

When compared to similar techniques, this numerical method's strong convergence properties 

make it popular for power flow calculations.  

shows up at some buses. In certain situations, one must make certain assumptions in order to 

simplify the Jacobian matrix because the solutions do not converge cleanly due to 

approximations [15]. Conditions before the fault can be derived from load flow analysis utilizing 

the rapid decoupled approach or Newton-Raphson method. The reserve bus selection has no 

effect on convergence in the Newton-Raphson approach. This approach begins by making an 

initial estimate for each unknown parameter [9]. 

It depends on establishing Taylor Series equations for power balance problems, which are 

essentially linear approximations to these equations. When working with a complex network, 

this is crucial. With the exception of the slack bus, it first concentrates on PQ buses, enabling 

actual and reactive power to be functions of angles and voltage [16]. 

First, the presence of a load bus and a distant PQ bus is investigated. In reference to the ith bus: 

𝑝𝑖 = ∑𝑛
𝑘=1 |𝑉𝑖| ∗ |𝑉𝑘| ∗ |𝑌𝑖𝑘| 𝑐𝑜𝑠 𝑐𝑜𝑠 (𝜃𝑖𝑘 + 𝛿𝑘 − 𝛿𝑖)  = 𝑝𝑖( |𝑉|, 𝛿𝑘 )   (1) 

𝑄𝑖 = ∑

𝑛

𝑘=1

|𝑉𝑖| ∗ |𝑉𝑘| ∗ |𝑌𝑖𝑘| 𝑠𝑖𝑛 𝑠𝑖𝑛 (𝜃𝑖𝑘 + 𝛿𝑘 − 𝛿𝑖)  = 𝑄𝑖( |𝑉|, 𝛿𝑘 )     (2)  

i.e., both real and reactive powers are functions of ) |V|, 𝛿), where: 

|𝑉| =  (|𝑉1|, … . , |𝑉𝑛 |𝑇 )𝛿 = (𝛿1, … . , 𝛿𝑛)𝑇                   (3)  

𝑃𝑖 (|𝑉|) =  𝑃𝑖(𝑥)                (4) 

𝑄𝑖 (|𝑉|) = 𝑄𝑖(𝑥)                (5)  

𝑥 =  [
𝛿

|𝑉|
]                           (6) 

 

Assume that the load buses' scheduled powers are Pi and Qi. Using Newton Raphson's second 

technique, x should gravitate to that value during iteration, creating stability [11]. 

𝜕𝑃𝑖 (𝑥)

𝜕𝛿𝑘
= − |𝑉𝑖| |𝑉𝑘|| 𝑌𝑖𝑘| 𝑠𝑖𝑛 𝑠𝑖𝑛 (𝜃𝑖𝑘 + 𝛿𝑘 − 𝛿𝑖 ), (𝑖 ≠ 𝑘 )                  (7)  

𝜕𝑃𝑖 (𝑥)

𝜕𝛿𝑘
= ∑𝑛

𝑘=1 𝑘≠𝑖 |𝑉𝑖||𝑉𝑘||𝑌𝑖𝑘| 𝑠𝑖𝑛 𝑠𝑖𝑛 (𝜃𝑖𝑘 + 𝛿𝑘 − 𝛿𝑖) , (𝑖 = 𝑘)    (8) 

𝜕𝑃𝑖 (𝑥)

𝜕|𝑉𝐾|
= |𝑉𝑖||𝑉𝑘| 𝑐𝑜𝑠 |𝑌𝑖𝑘|𝑐𝑜𝑠 (𝜃𝑖𝑘 + 𝛿𝑘 − 𝛿𝑖)  , (𝑖 ≠ 𝑘)                      (9) 



 

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𝜕𝑃𝑖 (𝑥)

𝜕|𝑉𝐾|
= 2|𝑉𝑖| 𝑐𝑜𝑠 |𝑌𝑖𝑘|𝑐𝑜𝑠 𝜃𝑖𝑖 + ∑𝑛

𝑘=1 𝑘≠𝑖 |𝑉𝑘||𝑌𝑖𝑘|𝑐𝑜𝑠 (𝜃𝑖𝑘 + 𝛿𝑘 − 𝛿𝑖), (𝑖 = 𝑘)   (10) 

𝜕𝑄𝑖 (𝑥)

𝜕𝛿𝑘
= |𝑉𝑖||𝑉𝑘||𝑌𝑖𝑘| 𝑠𝑖𝑛 𝑠𝑖𝑛 (𝜃𝑖𝑘 + 𝛿𝑘 − 𝛿𝑖), (𝑖 ≠ 𝑘)                                                      (11)  

𝜕𝑄𝑖 (𝑥)

𝜕𝛿𝑘
= ∑

𝑛

𝑘=1 𝑘≠𝑖 

|𝑉𝑖||𝑉𝑘||𝑌𝑖𝑘| 𝑐𝑜𝑠 𝑐𝑜𝑠 (𝜃𝑖𝑘 + 𝛿𝑘 − 𝛿𝑖) (𝑖 = 𝑘)                                   (12) 

𝜕𝑄𝑖 (𝑥)

𝜕|𝑉𝐾|
= |𝑉𝑖||𝑌𝑖𝑘| 𝑠𝑖𝑛 𝑠𝑖𝑛 (𝜃𝑖𝑘 + 𝛿𝑘 − 𝛿𝑖) (𝑖 ≠ 𝑘)                                                               (13) 

𝜕𝑄𝑖 (𝑥)

𝜕|𝑉𝐾|
= 2|𝑉𝑖| 𝑠𝑖𝑛 |𝑌𝑖𝑘|𝑠𝑖𝑛 𝜃𝑖𝑖 + ∑𝑛

𝑘=1 𝑘≠𝑖 |𝑉𝑘||𝑌𝑖𝑘|𝑠𝑖𝑛 (𝜃𝑖𝑘 + 𝛿𝑘 − 𝛿𝑖), (𝑖 = 𝑘)    (14) 

 

3. METHODOLOGY  

The Power World Simulator program was used for this investigation. The standard is used to 

conduct the load flow and short circuit studies initially.  

The outcomes are documented for the IEEE 9-Bus system. Using the Newton-Raphson iterative 

approach, the software has assessed the load flow. The two studies described above are then 

carried out once again after one generator has been taken out of the test system. After being 

recorded, the outcomes of these studies on this new system are compared to those derived from 

the conventional system. 

3.1 Test System Specifications. 

Comprising nine buses connected by transmission lines, an analysis and research tool for power 

systems is the IEEE 9 bus system. It is an eliminated model of a power distribution network and 

is frequently used to investigate a number of power system topics, encompassing load flow 

analysis, fault classification and detection, the impact of incorporating renewable energy, system 

stability analysis, and power flow optimization [15]. IEEE 9Bus Circuit: The IEEE 9 bus circuit 

is a famous model in the field of electric power systems, consisting of Nine buses, three 

generators, three loads, and three transformers make up the typical IEEE 9 bus system, as shown 

in figure (1)[11]. 

Furthermore, the IEEE-9 bus system's standard parameters for each bus are shown in table (1), 

followed by table (2). Provide the IEEE-9 Bus System's line information. 

 

Fig. 1 Single line diagram of IEEE-9 bus test system. 

Table1. Data for each bus of IEEE-9 Bus System. 

Angle (Degree) V (kv) V(p.u) Type NO 

0.0 16.5 1.04 Slack 1 

9.3 18.0 1.025 PV 2 

4.7 13.8 1.025 PV 3 



 

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2.2 230 1 PQ 4 

4.0 230 1 PQ 5 

-3.7 230 1 PQ 6 

3.7 230 1 PQ 7 

0.7 230 1 PQ 8 

2.0 230 1 PQ 9 
  

Table 2. Line data of IEEE-9 Bus System 

 

 

 

 

 

  

 

 

The study of transient stability examines the impact of significant, abrupt disruptions, such as a 

large-scale cable outage, a fault, or the abrupt load removal or application. The purpose of 

transient stability analysis is to make sure that a system can withstand the transient state that 

follows a disturbance. In Power World Simulator, follow these steps for transient stability 

analysis: 

Step One: an IEEE-9 bus system is chosen. The power world simulator implements and runs the 

system model, and load flow is carried out. The Newton Raphson approach aids in the load flow 

analysis of a nine-bus system. 

Step Two: Following load flow, the system's initial parameters, such as bus voltages, bus 

frequencies, bus power angles, and generator power angles, are examined. 

Step Three: Using the Newton-Raphson Method, a three-phase balanced fault is delivered to a 

transmission line at different buses, and tests the increased and decreased load in bus 5 and 6 and 

test outage the generator the outcomes are displayed in Power World Simulator. 

Step Four: Use Power World Simulator to investigate how load switching affects the IEEE 9 

bus model. The transient stability analysis is carried out for a short time 

4. RESULTS AND DISCUSSION 

The system model has been loaded and it simulated by used Power World Simulator software 

ware to generate the output results as well as the load flow analysis using the Newton Raphson 

technique at different as following: 

Case 1: Before the fault 

1. Load flows 

The load flow analysis and transient stability for the standard IEEE, Bus system are performed as 

indicated in Table (3). 

Table 3 Outcomes of the IEEE 9 Bus system's fault-free load flow analysis 

From To R(p.u) X(p.u) B(p.u) 

1 4 0 0.0576 0 

4 5 0.01 0.085 0.176 

4 6 0.017 0.092 0.158 

6 9 0.039 0.17 0.358 

5 7 0.032 0.161 0.306 

9 3 0 0.0586 0 

7 2 0 0.0625 0 

9 8 0.0119 0.1008 0.209 

7 8 0.0085 0.072 0.149 

Sr. 

No 

Bus 

No 
Area 

Nom 

(kV) 

p.u. 

(kV) 

Volt 

(kV) 

Angel 

(Deg) 

Load 

(MW) 

Load 

(Mvar) 

Gen 

(MW) 

Gen 

(Mvar) 

1 BUS1 1 16.50 1.040 17.160 0.00 0 0 71.6 27.91 

2 BUS2 1 18.00 1.025 18.450 9.35 0 0 163.00 4.90 



 

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2. The Power flows 

For examining these needs, the power flow is the fundamental instrument. The voltage 

magnitude and angle at each bus in a power system operating in a balanced three-phase steady-

state condition are determined by the power flow. As seen in Table (4), it also calculates the 

actual and reactive power flows for every piece of equipment that connects the buses. 

Table .4 Outcomes of Fault-Free Power Flow Analysis 

From 

Bus 

To 

Bus 

Branch 

Device Type 
MW from Bus 

Mvar from 

Bus 

MVA 

from 

8 9 Line -24.01 -0.4 34.2 

6 4 Line -30.56 -13.69 33.5 

7 8 Line 76.5 -0.25 76.5 

9 6 Line -59.45 -16.31 61.6 

5 4 Line -40.96 -35.71 54.3 

7 5 Line 86.51 -2.54 86.5 

4 1 Transformer 71.96 24.8 75.8 

2 7 Transformer -163 2.28 163 

9 3 Transformer 85.01 -3.65 85.01 

 

Case 2: Three phase short circuit balanced fault 

In the overall scheme of electrical systems, transient stability analysis is the study of how these 

systems behave and remain stable when subjected to brief (transient) disruptions. 

1. Fault between bus 4 and bus 5 at 1.0 s  

The transmission line between buses 5 and 4 experienced a three-phase short circuit balanced 

fault at 1.0 seconds, which was resolved at 1.1 second. All three generators' rotor angles are 

displayed in figure 2. Additionally, Figure 3 shows the frequencies of the three generators. 

 

 

 

. 

 

 

 
 

Fig.2: The rotor angles of three generators for a three-phase short circuit balanced fault 

between buses 4 and 5 at 1.0 seconds during the transmission line. 

 

 

 

3 BUS3 1 13.80 1.025 14.145 5.14 0 0 85.00 -11.45 

4 BUS4 1 230.00 1.025 227.01 -2.22 0 0 0 0 

5 BUS5 1 230.00 0.999 220.25 -3.68 125.00 50.00 0 0 

6 BUS6 1 230.00 1.012 224.36 -3.57 90.00 30.00 0 0 

7 BUS7 1 230.00 1.026 229.12 3.80 0 0 0 0 

8 BUS8 1 230.00 1.017 226.70 13.4 100.00 35.00 0 0 

9 BUS9 1 230.00 1.032 230.78 2.44 0 0 0 0 



 

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Fig.3: bus frequencies between buses 4 and 5 for the three-phase short circuit balanced 

fault on transmission lines at 1.0 second 

Case 3: Increased load on buses 

Here, at 1.0 s, bus 5 increases load 1 by 50% while bus 6 increases load 2 by 50%. Explain the 

effects of this load adjustment. 

1. Increased load1 50% on bus 5 at 1.0s 

In addition, bus 5's load is instantly reduced at 1.1 seconds after being raised by 50% at 1.0 

seconds. Figure 4 displays the rotor angles of the three impacted generators. The system 

stabilizes after a while. Figure 5 displays the system's frequency response at each bus. Changes 

in the frequency of the linked system are also brought on by abrupt variations in load at bus 5. It 

rises as a result of unexpected loading and falls as an outcome of the system's heavy load at bus 

5. Thus, the three generators on bus 5 will have their rotor speeds altered by the change in load 1 

on bus 5, as shown in figure 6.  

 

 

 

 

 

 

 

Fig.4: Three generators' rotor angles for an abrupt 50% load rise on bus 5 at 1 second 

 

 

 

 

 

 

 

Fig.5: Bus frequencies for an abrupt 50% load rise on bus 5 at 1 second 

 

 

 

 

 

 

Fig. 6: Three generators' rotor speed for an abrupt 50% load rise on bus 5 at 1 second 



 

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2. Increased load2 50% on bus6 at 1.0s 

This causes bus 6's load to spike by 50% at 1.0 seconds and then be instantly removed at 1.1 

seconds. Figure 7 displays the three impacted generators' rotor angles. After a while, the system 

stabilizes. The response to frequency of the whole system at each bus is shown in figure 8. The 

frequency of the linked system varies as a result of the sudden changes in load at bus 5. When 

bus 6 is overloaded, the system's performance deteriorates, while unexpected loading causes it to 

grow. and the three generators on bus 6 will have their rotor speeds altered by the change in load 

2 on bus 6, as illustrated in figure 9.  

 

 

 

 

 

 
 

Fig.7: Three generators' rotor angles for a 50% load rise on bus 6 at 1 second 

 

 

 

 

 

 
 

Fig.8: Bus frequencies for an abrupt 50% load rise on bus 6 at 1 second 

 

 

 

 

 

 

 

Fig. 9: Three generators' rotor speed for an abrupt 50% load rise on bus 6 at 1 second 

Case 4: Decreased load on buses 

In this case, load1 is decreased by 50% on bus 5 and load 2 by 50% on bus 6 at 1.0 s. Describe 

the impact of this load adjustment.  

Although all three generators have a rotor angle divergence, the system eventually stabilizes. The 

angle difference, however, likewise rises as the CCT time does. This indicates that the system is 

operating in an unstable state. The CCT needs to be incredibly short to maintain system 

synchronization because if it takes longer to resolve the problem, the system will lose 

synchronization [17]. 

 

 



 

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1. Decreased load1 50% on bus 5 at 1.0s 

In Figure 10, the system buses' frequency response is displayed. Additionally, the unexpected 

load change at bus 5 causes a change in the frequency of the connected system. Figure 11 shows 

how the three generators' rotor angles changed when the load on bus 5 dropped by 50% at one 

second. Moreover, figure 12 illustrates the impact of an abrupt 50% drop in bus 5's load at a 

single minute in speed for the three generators' rotors. 

 

 

 

 

 

 

 

Fig.10: Bus frequencies for an abrupt 50% load decrease on bus 5 at 1 second 

 

 

 

 

 

 

 

 

Fig.11: Three generators' rotor angles for a 50% load decrease on bus 5 at 1 second 

 

 

 

 

 

 

 

Fig. 12: Three generators' rotor speed for an abrupt 50% load decrease on bus 5 at 1 

second 

2. Decreased load2 50% on bus 6 at 1s 

Figure 13 displays the system buses' frequency response. The sudden decrease in load at bus 5 

also causes a change in the frequency of the connected system. Figure 14 shows the three 

generators' rotor angle changes for a 50% drop in bus 6 load at 1 second. Additionally, figure 15 

illustrates the impact of a sudden 50% drop in bus 6's load at a single speed shift for the three 

generators' rotors. 

 

 



 

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Fig.13: Bus frequencies for an abrupt 50% load decrease on bus 6 at 1 second 

 

 

 

 

 

 

 

 

Fig.14: Three generators' rotor angles for a 50% load decrease on bus 6 at 1 second 

 

 

 

 

 

  

 

 

Fig. 15: Three generators' rotor speed for an abrupt 50% load decrease on bus 6 at 1 

second 

Case 5: Outage of generator  

Figure 16 shows the rotor angles of the generators when generator 1 is not in use for 1.0 seconds. 

Because of the system outage, generator 1 does not have any rotor angle fluctuation, but 

generators 2 and 3 do. Figure 17 illustrates how changes in the frequency of the associated 

system are also brought on by the generator1 outage. Because the system has less generation as a 

result of the outage, the frequency of the system drops. Because bus 5 is no longer loaded due to 

a fault, the system's frequency rises as a result of less system loading. 

 

 

 

 

 



 

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Fig.16: Three generators' rotor angles during a single generator outage 1 second 

 

 

 

 

 

 

 

 

Fig.17: Bus frequencies during a 1.0 second generator1 outage 

5. Conclusion 

Considering generators 2 and 3 are closer to the problem point than generator 1, it can be 

concluded that their rotor angle deviation is the greatest. The system stabilizes after a period of 

time. A higher critical clearing time result in a greater angle difference. The system is in an 

unstable status as a result. If it takes longer to fix the issue, the system will be out of sync; hence, 

the CCT needs to be very tiny to keep the system in sync. Due to a transmission line problem 

between buses, the associated system's frequency also fluctuates. 4. and.5. As the load at bus 5 is 

eliminated owing to a malfunction, the system experiences less loading, which results in a rise in 

frequency. 

Furthermore, graphs in the IEEE 9 bus architecture show that the power angle curves are not 

stable and the system's frequency suddenly decreases when the unexpected load is increased by 

50%. Otherwise, all three generators exhibit a rotor angle deviation; however, the system 

eventually stabilizes. However, the angle difference likewise lengthens when the CCT duration 

is increased. This shows that there is instability in the system's operation. To maintain system 

synchronization, the CCT must be reasonably short since if more time is required to resolve the 

problem, the sudden change in the load on buses 5 and 6 would also cause the system to get out 

of sync. 

References: 

1. Prabha S. Kundur, Om P. Malik, “Power System Stability and Control”, Second Edition, Mc 

Graw Hill Education, 2022. 

2. Ziad M. Ali, Martin Ćalasan, Francisco Jurado, AND Shady H. E. Abdel Aleem, 

“Complexities of Power Quality and Harmonic-Induced Overheating in Modern Power Grids 

Studies: Challenges and Solutions'', 2024. 

3. Poulose, A.; Kim, S. “Transient Stability Analysis and Enhancement Techniques of 

Renewable-Rich Power Grids. Energies 2023, 16, 2495. https:// 

doi.org/10.3390/en16052495. 



 

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4. Anionovo U. E., DR. Emmanuel C. E., Augutine N. N., and Prof. Josiah C. O., “Hybrid 

Transient Stability Analysis Solution for Power System Stability Studies', IRE Journals | 

Volume 5 Issue 9 | ISSN: 2456-8880 

5. Peter W. Sauer , M. A. Pai , Joe H. Chow ,“ Power System Dynamics And Stability”, 2nd 

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