This document presents a project proposal for analyzing the transient stability of the Kenya power system incorporating geothermal power from the Menengai power station. The proposal provides background on geothermal power plants and their components. It discusses the problem statement around evaluating a power system's ability to withstand disturbances. The objectives are to analyze the transient stability of the system with more power injection and compare the stability of different synchronous machines. The methodology will use Dig SILENT software to simulate disturbances like faults, generation loss, and load changes to analyze active power, voltage magnitude, and rotor angle responses.

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JOMO KENYATTA UNIVERSITY OF AGRICULTURE AND
TECHNOLOGY
SCHOOL OF ELECTRICAL, ELECTRONIC AND INFORMATION
ENGINEERING
DEPARTMENT OF ELECTRICAL AND ELECTRONIC ENGINEERING
FINAL YEAR PROJECT PROPOSAL
JEFF M. WANJALA
EN271-C007-0046/2010
SUPERVISOR: MR. AMOS KIVUVA
TRANSIENT STABILITY ANALYSIS OF THE KENYA POWER SYSTEM
INCORPORATING GEOTHERMAL POWER FROM MENENGAI POWER
STATION
A Final Year Project submitted to the Department of Electrical and Electronic Engineering in
partial fulfillment of the requirements for the award of a Bachelor of Science Degree in Electrical
and Electronic Engineering.
July 2015

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DECLARATION
Thisprojectis myoriginal work,exceptwheredue acknowledgementismade inthe text,andtothe best
of my knowledge has not been previously submitted to Jomo Kenyatta University of Agriculture and
Technology or any other institution for the award of a degree or diploma.
NAME : JEFF M. WANJALA
REG. NO: EN271-C007-0046/2010
SIGNATURE………………………………………… DATE ………………………………
TITLE OF PROJECT: TRANSIENT STABILITY ANALYSISOF THE KENYA
POWER SYSTEM INCORPORATING GEOTHERMALPOWERFROM MENENGAI
POWER STATION
SUPERVISOR CONFIRMATION:
This project has been submitted to the Department of Electrical and Electronic Engineering, Jomo
Kenyatta University of Agriculture and Technology, with my approval as the supervisor:
NAME: MR. KIVUVA AMOS
SIGNATURE………………………………………… DATE ………………………………

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TABLE OF CONTENTS
DECLARATION............................................................................................................................... ii
SUPERVISOR CONFIRMATION:.................................................................................................... ii
1. INTRODUCTION.......................................................................................................................1
1.1 PROBLEM STATEMENT........................................................................................................2
1.2 PROBLEM JUSTIFICATION ...................................................................................................2
1.3 OBJECTIVES...........................................................................................................................3
1.3.1 MAIN OBJECTIVE............................................................................................................3
1.3.2 SPECIFIC OBJECTIVES....................................................................................................3
2. LITERATURE REVIEW.............................................................................................................4
2.1 GEOTHERMAL POWER PLANT.............................................................................................4
2.1.1 GEOTHERMAL POWER PLANT GENERAL SETUP........................................................5
2.1.2 TYPES OF GEOTHERMAL POWER PLANTS...................................................................6
2.2 POWER SYSTEM....................................................................................................................8
2.2.1 GENERATINGPOWER STATIONS..................................................................................8
2.2.2 SUBSTATIONS.................................................................................................................8
2.2.3 TRANSMISSION,SUB-TRANSMISSION AND DISTRIBUTION..............................8
2.2.4 LOADS..............................................................................................................................9
2.3 TRANSIENT STABILITY........................................................................................................9
2.3.1 TRANSIENT STABILITY CALCULATIONS.....................................................................9
2.3.2 CAUSE OF TRANSIENT INSTABILITY .........................................................................13
2.3.3 METHODS OF IMPROVING TRANSIENT STABILITY..................................................13
3. METHODOLOGY....................................................................................................................14
3.2 MAIN COMPONENT DESCRIPTION............................................................................................14
3.2.1 SYNCHRONOUS GENERATORS............................................................................................14
3.2.2 POWER TRANSFORMERS ...................................................................................................16
3.2.3 Transmission lines.............................................................................................................16
3.2.4 Loads................................................................................................................................16
3.3 INCREASING LOAD/ STRESSING OF THE SYSTEM ...............................................................17
3.4 SIMULATION PROCEDURE.................................................................................................17
3.4.1 THREE PHASE FAULTS.................................................................................................17
3.4.2 LOSS OF GENERATION.................................................................................................18

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3.4.3 SUDDEN LOAD CHANGES............................................................................................18
4. RESULTS AND ANALYSIS.....................................................................................................19
4.1 SIMULATIONS IN THE MODELED SYSTEM......................................................................19
4.2 THREE PHASE FAULTS RESULSTS....................................................................................19
4.2.1 ACTIVE POWER RESPONSE..........................................................................................19
4.2.2 VOLTAGE MAGNITUDE RESPONSE ............................................................................21
4.2.3 ROTOR ANGLE RESPONSE...........................................................................................22
4.3 LOSS OF GENERATION.......................................................................................................24
4.4 SUDDEN CHANGE IN LOAD ...............................................................................................26
4.5 EFFECTS OF MOREPOWER INJECTION FROM MENENGAI.............................................28
 Active power.........................................................................................................................28
 Voltage magnitude response..................................................................................................29
 Rotor angle response..............................................................................................................31
5. RESULT ANALYSIS ...............................................................................................................32
5.1 LIMITATIONS AND ASSUMPTIONS MADE........................................................................32
REFERENCES.................................................................................................................................33
APPENDIX .....................................................................................................................................34
APENDIX A-PROJECT TIME PLAN...........................................................................................34
APPENDIX-B PROJECT BUDGET ......................................................................................................35
APPENDIX-C THE KENYAN POWER SYSTEM DATA .............................................................35

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TRANSIENT STABILITY ANALYSIS OF THE KENYA POWER SYSTEM
INCORPORATING GEOTHERMAL POWER FROM MENENGAI POWER
STATION
JEFF M. WANJALA – EN271-C007-0046/2010
Department of Electrical and Electronic Engineering, JKUAT
ABSTRACT:
Geothermal power is the production of electric power from steam generated from hot rocks deep
underground beneath the earth surface. It provides reliable and cost competitive power and is less
vulnerable to climate changes as compared to hydropower. Kenya is currently the largest producer of
geothermal energy in Africa generating 593MW with a potential of 10000MW according to Kenya’s
Geothermal Development Company (GDC). Currently, GDC is undertaking production drilling at
Menengai geothermal field for 105 MW power developments to be commissioned in 2015 by three
independent power producers (IPPs) each installing a 35MW power plant.
Transient stability analysis has recently become a major issue in the operation of power systems due to
the increasing stress on power system networks. This problem requires evaluation of a power system's
ability to withstand disturbances while maintaining the quality of service. Thus this project aims at
analyzing transient stability of the Kenya power system incorporating geothermal power from Menengai
power station.
I propose to use Dig SILENT simulator program to analyze the system’s behavior in terms of transient
when subjected to disturbances

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1.INTRODUCTION
Energy is considered an essential ingredient for economic growth and social development in
Kenya and the world as a whole. The growth of energy demand is driven by several factors as
follows, economic growth, industrialization, urbanization, an increase in electrical appliances
use, rural electrification programs and population growth. This is the main reason as to why it
would be difficult to achieve Kenya Vision 2030 without taking into consideration generation of
more electrical energy.
Currently there are plans and work under way to inject more electrical energy into the national
grid which for quite some time been predominantly dominated by hydropower and thermal
power. Much focus has been put into renewable energy mainly constituting of wind power
generation and geothermal power generation. The government in partnership with the private
sector will see this through by setting up strategic plans and deadline targets of the intended
power to be generated.
Geothermal power which is the production of electric power from steam generated from hot
rocks deep underground beneath the earth surface has been given much attention due to the
potential it holds. Kenya is currently the largest producer of geothermal energy in Africa and
eighth largest in the world generating 593MW with a potential of 10000MW and a short term
target to have harnessed 5000MW by 2017 according to Kenya’s Geothermal Development
Company (GDC). Currently, GDC is undertaking production drilling at Menengai geothermal
field for 105 MW power developments to be commissioned in 2015 by three independent power
producers (IPPs) which are, Ormat Tecnologies, Quantum Power and Sosion Energy each
installing a 35MW power plant.
Unlike the other ways of power production in Kenya, geothermal power has proven to be
reliable, cost competitive, environmental friendly and is less vulnerable to climate changes. For
instance, hydropower may be the cheapest way of power production trading at Ksh2.74 per Kwh
although many a times we are forced to switch to thermal power which trades at Ksh17.35 per
Kwh during drought seasons. This may be avoided by increasing the capacity of geothermal
power which trades at Ksh6.39 per Kwh thus lowering the cost of production in industries and
domestic consumer monthly bill. Inflation will also substantially lower as this would mean
importation of less barrels of High Fuel Oils a special type of diesel used in thermal generators.
Geothermal plants have also proven to be reliable and efficient as most a times the generated
power is close to the maximum installed capacity unlike hydro which are subjective to climate
changes.
With all this power being injected into the national grid, it would be of importance to analyze the
transient stability of the system and the benefits or drawbacks that more power would result.

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1.1 PROBLEM STATEMENT
Over the years the Kenya electrical power system has grown in size and complexity with large
number of interconnections. Coming up with the design of the system and its secure operation is
still a challenging operation. To maintain a reliable service of the system, the grid must remain
intact and be capable of withstanding a variety of small and large disturbances. For several years
stability has been a major concern. In evaluation of stability the concern is the behavior of the
system when subjected to transient disturbance, which may be small or large.
Transient Stability involves the study of the power system following a major disturbance.
Following a large disturbance of the synchronous alternator(s) the power (load) angle changes
due to sudden acceleration of the rotor shaft. The objective of the transient stability study is to
ascertain whether the load angle returns to a steady value following the clearance of the
disturbance. [1]
Although measures have been put in place to overcome transient faults, it is still a problem to
fully protect the system against it. In this project through analysis, the Kenya power system will
be studied on how it will behave with injection of more power into the grid from Menengai
geothermal fields (105MW).
1.2 PROBLEM JUSTIFICATION
The analysis of transient stability is usually used to investigate the stability of power systems
under sudden and large disturbances, and play an important role in maintaining security of power
system operation. The electrical power transient stability calculation program enables engineers
to accurately model power system dynamics and transients by simulating system disturbances.
By analysis, the transient behavior of the system may be studied when more power is injected
into the system (national grid). This may be of benefit as from it the drawbacks or benefits of
more power injection may be obtained thus facilitating in power planning and addition of more
power.
More reliable and steady power is essential for accomplishment of Kenya vision 2030 for the
growth of the economy and power supply to the population.

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1.3 OBJECTIVES
1.3.1 MAIN OBJECTIVE
To analyze the transient stability behavior of the system when subjected to major disturbances
comparing the transient stability of different types of synchronous machines to that of turbine
generator(s) with more power being injected into it from Menengai geothermal field.
1.3.2 SPECIFIC OBJECTIVES
i. To analyze the transient stability of the system with more power injection.
ii. To compare the transient stability of different synchronous machines to that of turbine
generators.

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2.LITERATUREREVIEW
The project is based on analyzing the effect of injection of more power to the system in terms of
transient stability with more power from Menengai geothermal field. There is need to analyze the
system which has grown is size and capacity over the years with newer power generation plants,
substations, transmission lines and buses. Currently, there is work underway to increase the
produced power by 105MW from Menengai geothermal field.
2.1 GEOTHERMALPOWER PLANT
Whether a power plant is fueled by nuclear, coal or geothermal energy, all have one feature in
common, convert heat energy to electrical energy. Heat energy from the Earth is called
geothermal which is derived from geo (Earth) and thermal (heat). This energy is accessed by
drilling steam or water in a process similar to drilling of natural gas or oil.
Geothermal power plants are very similar to traditional power plants like thermal and hydro
generating power stations as they use some components which are similar, including generators,
turbines, transformers and other standard equipments used in power generation. Generally there
are three types of geothermal power plants depending on how the steam or hot water is extracted
and used to turn the turbines.
Figure 1; Geothermal Power Plant

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2.1.1 GEOTHERMALPOWER PLANT GENERALSETUP
In general a plant will mainly consist of wells, turbines, generators and a transmission to deliver
the power.
Figure 2; General setup of a geothermal power plant
This is the channels through which geothermal steam or water from the earth or re-injected water
passes through. It is usual a pipe drilled deep into the earth geothermal aquifers about 350-3050
meters deep.
i. TURBINE
This is where high pressure steam energy is converted to rotary motion which in turn rotates the
generator coupled to it. Without the turbine, it would be impossible to generate any electrical
power.
ii. GENERATOR
A geothermal generator operates on the same principle as any other synchronous generator
despite operating at higher speeds of revolution per minute. Usually the synchronous generator
produces power at 11kV.

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iii. TRANSMISSION
Electric power generated from the plant is sent to a step-up transformer outside the plant. The
stepped up voltage is transmitted over transmission lines to industries, homes and businesses.
2.1.2 TYPES OF GEOTHERMALPOWER PLANTS
i. DRY STEAM POWER PLANT
For this type of power plant, the dry steam is fed directly to the turbines directly from inside the
earth. In this case, there is no need of additional boiler fuel and heating boilers. This type of
power plant is not common as natural hydrothermal reservoirs dry steam is very rare.
Fig3. Dry Steam power plant
ii. FLASH STEAM POWER PLANT
This is the most commonly used type of geothermal power plant, using water at temperature
greater than 362F. The water is collected in flash tanks resulting in drop in pressure thus liquid to
boil into steam as the hot water flows up through the drilled wells in the ground. This steam is
separated from liquid then used to run the turbines which in turn generate power.

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Fig4. Flash Steam Power Plant
iii. BINARY STEAM POWER PLANT
In this type of steam power plant, high temperature water from the geothermal well is used to
heat another fluid of lower boiling point. The fluid vaporizes to steam which in turn turns the
turbines then condenses back to liquid to begin the process again.
The steam condenses to water which is then re-injected back to the ground to be reheated. The
re-injected water does not come into contact with the working fluid.
Fig5. Binary Steam Power Plant

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2.2 POWER SYSTEM
An electric power system is a network of electrical components used to generate, transmit,
distribute and consume electrical power. [2]
Fig6. Power System
2.2.1 GENERATING POWER STATIONS
Generating power station is where electrical energy is generated from mechanical energy; this is
archived by turning conductors round a magnetic field which results in the flow of current.
Synchronous generators are widely used in this as they are of more benefits in the production of
bulk power as compared to induction generators.
2.2.2 SUBSTATIONS
Despite it having many electrical and protective components, the main reason as to why we need
substations is for voltage transformations by use of transformers. When power needs to be
transmitted, a generating substation will be used to step-up the voltage to higher levels to ensure
maximum power transfer to the intended load or user. A distribution substation will be used to
step down the voltages to lower levels to be consumed by industries, residential areas and
business premises.
2.2.3 TRANSMISSION, SUB-TRANSMISSIONAND
DISTRIBUTION
In transmission of bulk power, transmission lines are used to transmit 132kV or 220kV. This is
an interconnection between the power plant substation and distribution substation. Power is
transmitted at higher voltages to ensure maximum power transfer which means minimum power
loses. Sub-transmission involves transmitting power at lower levels usually 66kV or 33kV, it is

14. 9 | P a g e
most present in thermal plants close to the point of power consumption and from substations to
large electrical consumers. For small levels of power, example 415v, distribution lines are used.
2.2.4 LOADS
Loads are the electrical consumers classified as industries, commercial and residential. The
largest consumer of electrical power is industries that use it for manufacturing. Residential
consumers are domestic houses who mainly use power for lighting and heating purposes while
commercial are business premises that use it for lighting, running of computers and other office
equipments.
A good power system should be reliable, safe, economical and secure.
2.3 TRANSIENT STABILITY
Stability of the power system has been a headache over the past years with growth of the system
and newer interconnections from generating plants with different characteristics. It is every
power engineer’s wish to ensure a reliable power system that is stable enough to withstand faults
and disturbances. Transient stability analysis and studies have been of interest as they help in
analyzing the capabilities of a power system to regain stability after being subjected to major
physical disturbances.
2.3.1 TRANSIENTSTABILITYCALCULATIONS
As mentioned earlier, transient stability involves the study of the power system following a
major disturbance. Following this the alternator machine power angle changes due to sudden
acceleration of the rotor shaft. The main reason of transient stability analysis is to insure whether
the load angle returns to a steady value following the clearance of the disturbance. [3]
i. Power Angle Relationship
Consider the single-machine-infinite-bus (SMIB) system shown in Fig. 7.
Fig7. An SMIB system
The internal generated emf of the generator is the sending end voltage. Then the sending end
voltage and reviving end voltage will given by
 0, 21 VVVV RS 
Then the sending current

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jX
jVVV
jX
VV
IS
 sincos 12121 



Thenthe sendingendreal powerandreactive powerare thengivenby
 
jX
jVVV
jVIVjQP SSSS


  

sincos
sincos 121
1
Thissimplifiesto
 
X
VVVjVV
jQP SS
 cossin 21
2
121 

Assumingthe line islossless,the real powerdissipatedfromthe sendingendisequal tothe real power
receivedatthe end.
 sinsin max
21
P
X
VV
PPP RSe 
Where Pmax = V1V2/X (maximum power)
Fig8. Typical power angle curve
From thisfigure we cansee that fora givenpower P0. There are two possible values of the angle   0
and max. The angles are given by

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0max
max
01
0
180
sin









 
P
P
ii. Swing Equation
Considering a three phase synchronous alternator, equation of motion of the rotor is given by
aem TTT
dt
d
J 2
2

Where
J is the total moment of inertia of the rotor mass in kgm2
Tm is the mechanical torque supplied by the prime mover in N-m
Te is the electrical torque output of the alternator in N-m
 is the angular position of the rotor in rad
Acceleration torque Ta is given by the difference between the mechanical and electrical torque
assuming there are no losses. During this period the rotor will move at synchronous speed s in
rad/s.
The angular position  is measured with a stationary reference frame. To represent it with respect
to the synchronously rotating frame, we define
  ts
Then
dt
d
dt
d
s




Defining the angular speed of the rotor as
dt
d
r

 
We can write this as
dt
d
sr

 
We can therefore conclude that the rotor angular speed is equal to the synchronous speed only
when ddt is equal to zero. We can therefore term ddt as the error in speed.
aem TTT
dt
d
J 2
2

Multiplying both sides by m we get

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aemr PPP
dt
d
J 2
2


Where Pm, Pe and Pa respectively are the mechanical, electrical and accelerating power in MW.
We now define a normalized inertia constant as
rated
s
S
J
H
2ratingMVAGenerator
joules-megainspeedssynchronouatenergykineticStored 2


Substituting we get
aemr
s
rated
PPP
dt
dS
H 2
2
2
2



Finally we get
aem
s
PPP
dt
dH
2
2
2 

per unit
From the final equation, the angular and synchronous speed of the machine is equal hence we
replace r in the above equation by s.
iii. Equal Area Criterion
Fig.8 Power angle curve for equal area criterion
For the system to be stable, area 1 should be equal to area 2.

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    
m
cr
cr
dPPdPP meem





0
2.3.2 CAUSE OF TRANSIENT INSTABILITY
 Sudden application or removal of load
 Switching operations
 Line faults
 Loss of generation
2.3.3 METHODSOF IMPROVING TRANSIENTSTABILITY
 Use of breaking resistors
 Use of high speed re-closing circuit breakers
 Fast valving
 Use of fast responding, high gain exciters
 Single pole switching

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3.METHODOLOGY
3.1 Kenyan system modeling
Due to expansion of the Kenyan power system, there has been an increase in the number of
connected generating plants, transmission lines and load capacity. This led to the improvement
of the reference Kenyan system model of 2008 comprising of 15 synchronous generators, 24
transformers, 51 transmission lines, 19 loads, and 56 buses to an updated 2013 version made
up of 21 synchronous generators, 26 transformers, 103 transmission lines, 56 loads, and 96
buses. With addition of 105MW Menengai Power Station, the number of synchronous
generators, transformers and buses increase by one becoming 27, 22 and 97 respectively. With
this improvement, the system had an installed capacity of 1676.51MW which increased to
1781.51MW after connection of Menengai while the connected load and the generation
remaining constant at 1560.00MW and 1609.05MW respectively.
3.2 MAIN COMPONENTDESCRIPTION
To come up with the Kenyan power system network, power elements which comprise of
generators generating at different power levels, transformers at generation stations, transmission
lines of different voltage levels and variable loads were used in interconnection. This was in
accordance to the 2013 model which gave the ratings of the elements in terms of power, voltage
and current and their parameters in terms of susceptance, reactance and limits.
3.2.1 SYNCHRONOUS GENERATORS
From the system, the main source of power was generated by synchronous generators of
different power and voltage ratings and of variable parameters all depending on type of machine
used weather salient pole or round rotor type. Machine used were mainly hydro synchronous
generators in hydro stations, turbo generators in geothermal stations and thermal generators in
diesel powered plants. The entire system’s generators were rated at 11kV with exception of three
units rated at 15kV which were Gitaru I, II and III generators, although in terms of power
generated and value of installed capacity of individual generators varied from machine to
machine. Another variation was also notable in the RMS values of the machines taking a sample
of hydro, thermal and turbo as shown in the tables below taken from the DigSILENT program.

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Fig.9 Kiambere RMS values

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Fig.10 Thika Power RMS values
Fig.11 Menengai Power RMS values
3.2.2 POWER TRANSFORMERS
Power transformer is connected between the generator terminals and the transmission system and
converts the voltage level of the generator to the transmission voltage level. In the configuration
of the transformers, the YN-YN connection was used. This was mainly to avoid the phase shift
introduction by other connection configuration like that of ∆-Y. The rating of the transformers
varied from station to station. In the modeling of the transformers, mainly they were 11/132kV
apart from the ones in Gitaru which were 15/132kV and the other 15/220kV.
3.2.3 Transmissionlines
The values given to the transmission lines parameters which are the resistance, impedance and
susceptance per kilometer for the positive sequence and zero sequence was in accordance to the
reference table having the type of cable used and the rated voltage value being transmitted. This
table’s values were used together with the 2013 model as the model gave information of the
length in kilometers of the cables between connection points. Also the maximum current and
apparent power capabilities of the line were given.
3.2.4 Loads
The loads were represented at various load buses in mega-watts (MW) and mega-var (MVar).
During modeling of the system, the load was initially at 1560.00MW although it was not
possible to maintain at this value when stressing the system as much as it would be desirable to
maintain it constant. Load values varied from load points depending with the amount of power

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demanded at a particular point as it was notable more power was demanded in bigger cities as
compared with remote locations.
3.3 INCREASING LOAD/ STRESSING OFTHE SYSTEM
From the 2013 model with inclusion of Menengai, the system load was increased at random at
various load points by 62MW lowering the system reserve thus stressing the system. The main
reason as to why this was done was to make the system highly responsive to transient
disturbances for analysis purposes. After stressing the system, load flow calculation was done
and the grid summary obtained so as to ascertain the system was still running and had no faults.
This altered some values like the generated power and load to 1672.96MW and 1619.00MW
respectively showing an increase in both with the spinning reserve lowering from 211.53MW to
106.39MW. The stressed system formed the basis of our analysis.
3.4 SIMULATION PROCEDURE
From the stressed system which formed the basis of our analysis, transient analysis simulations
were done by intentionally creating disturbances on various parts on the network keeping some
parameters of the network constant. These parameters were the load values of the system, the
generated power by the system’s generators and the parameters of the elements used in the
model assembly. The disturbances created on the system were, three phase faults on the
transmission lines, sudden load change which included connection and removal of load suddenly
at the load buses and loss of generation at the generation station. Comparisons were done among
the different types of generators taking the turbo generator as the reference. Hydro and diesel
powered generators were compared to turbo generators in terms of transient response Menengai
station being the reference.
3.4.1 THREE PHASE FAULTS
Transient three phase faults were introduced intentionally at the transmission lines at an equal
distance from the generation units for all the generators under study. First, this was done to the
system with disconnection of Menengai Power Station then with connection of the Power
Station. Comparison between the transient responses of different machines was done and the
effect of more power connection to the grid noted. Created faults were at an equal selected
distance. That is, if in the first scenario a fault location was set 20KM away from a diesel
powered station, the same was selected for a hydro station and turbo generator. When creating
the faults, an execution time of 2.00seconds was selected for the fault happening in the short
circuit event panel box to be cleared in a time laps of 0.07seconds by opening the circuit
breakers. The circuit breakers execution time was set to happen in a time laps of 2.07seconds set
in the switch event panel box. After setting of the execution time for both short circuit and
switching events, initial condition calculations for RMS values were done although not necessary
to ascertain the system had no problems before simulation. A run simulation time of 4.8seconds
was selected in which the transient response of the machines would be viewed.

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3.4.2 LOSS OF GENERATION
Although perceived most of the time a disturbance might only be line faults, loss of generation is
also a major fault that may occur and cause a transient disturbance to a system. When this type of
fault occurs, the whole power generation site may stop providing power or only a single
component of the generating station stops providing power all depending on the number of
stacked generators. It is very likely most of the power plants we have in Kenya and the world
over consist of synchronous generators connected together in parallel to provide a rated power
generation. For instance a generating station of 280MW may consist of four units each providing
70MW which in our study is the case although represented by a single unit as it assumed the
stacked machines are coherent. In this, the generated power of a station was disconnected from
the grid by opening the circuit breaker. The disconnection was done to represent a fault that had
occurred to the station thus opening the circuit breaker of that station isolating it from the grid.
The time at which the breaker was set to open was 2.00seconds in the switch event panel box of
the generators after which transient response of the machines was analyzed. Analysis was done
to the different machines taking a comparison with and without connection of Menengai.
3.4.3 SUDDEN LOAD CHANGES
The value of demanded power by the load is very rare for it to be constant as it keeps on
fluctuating depending on the time of day. More power is demanded during day hours as that is
the time most companies are running. Sudden changes in load(s) were introduced to the system
by sudden connection and disconnection of load from the load buses. This was done by setting
the load circuit breakers to open suddenly after a set time of 2.00seconds in the switch event
panel box before the initial conditions were calculated then the simulation. In the simulation,
transient response of the system was analyzed between the different types of machines with and
without additional connection of Menengai.

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4.RESULTSAND ANALYSIS
To analyze the transient effects of more power generation from Menengai turbo generator,
simulations in DigSILENT were done in accordance to the simulation procedure where results
from the various types of disturbances were analyzed. The results of the analysis were compared
among the different types of machines used in the model. Turbo generators were of more interest
as from the introduction, Kenya is planning to have more power production from them.
4.1 SIMULATIONS IN THE MODELED SYSTEM
From the modeled system (stressed), an execution time of 2.00seconds was set for all the
scenarios, that is, for the three phase faults, loss of generation and sudden change in load. Active
power response, speed deviation and voltage magnitude response were taken.
4.2 THREE PHASE FAULTS RESULSTS
4.2.1 ACTIVE POWER RESPONSE
First the faults were done at an equal distance from the generators. A fault was created 68km
away from Olkaria I A.U, Gitaru I and II and Kipevu 2 taking the transient response of the
machine.
Fig.14 Comparison of active power response of Olkaria I A.U

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Fig.17 Gitaru II and III active power response
Fig.18 Kipevu 2 active power response

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4.2.2 VOLTAGE MAGNITUDE RESPONSE
In similar way to the active power response, faults 68km away from the generator were created.
Fig.19 Okaria I A.U voltage magnitude response

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Fig.20 Gitaru II and III Voltage Magnitude response in p.u
Fig.21 Kipevu 2 voltage magnitude response in p.u
4.2.3 ROTOR ANGLE RESPONSE
The angle response of the machines was taken having faults 68Km from the machines.

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Fig.22 Olkaria I A.U speed deviation response
Fig.23 Olkaria I A.U rotor angle reference to reference machine angle

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Fig24. Gitaru II and III rotor speed deviation response
Fig.25 Gitaru II and III rotor angle response with reference to reference bus voltage in degrees
4.3 LOSS OF GENERATION
In this, the first scenario was loss of generation in Olkaria I generator.

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Fig.26 Olkaria I A.U active power response in MW
In the second scenario was loss of generation in Sangoro generator.
Fig.27 Turkwel rotor angle response with reference to bus voltage

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Fig.28 Turkwel active power response with loss of Sondu generator
4.4 SUDDEN CHANGE IN LOAD
Fig.29 Turkwel active power response in MW after sudden loss of Lessos load

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Fig.30 Menengai (connected) active power response with sudden disconnection of load at
Naivasha
Fig.31 Turkwel active power response with sudden loss of Lessos load

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Fig.32 Kipevu 3 active power response with sudden loss of load at Kipevu 132 bus
4.5 EFFECTSOF MORE POWER INJECTIONFROM MENENGAI
 Active power
It was very evident that with more power injection from Menengai, the active power response of
the machines in transient response improved. This was shown in the case of Olkaria I A.U with
the magnitude of the output active power from the machine increasing though having the same
swing. From this, the machine was able to maintain a higher power magnitude output. The rapid
fall in the output power was slightly raised when Menengai was connected although the extent to
which a machine responded depended with the distance from the fault. A similar observation was
viewed in Gitaru II and III where the swing was similar though a raise in magnitude was noted.

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Fig.33 Olkaria I A.U active power response (three phase fault 68km from location)
Fig.34 Gitaru II and III active power response (three phase fault 68km from location)
 Voltage magnitude response
From the simulation, the voltage magnitude in per unit value improved characterized by a more
stable swing curve. For instance, the one observed from Olkaria I A.U showed a decrease in
magnitude in the rapid fall in voltage and the settling of the swing was better. This proved
addition of more power to the grid improved the voltage magnitude response of the system
during fault disturbance although this depended on the distance the additional machine was
connected relative to the one under study.

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Fig.35 Olkaria I A.U voltage magnitude response

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Fig.35 Gitaru II and III voltage magnitude response
 Rotorangle response
From the rotor angle response, an improvement was observed with the speed deviation lowering
with increase in power. This showed the rotor of the machine deviated less with more power
injection.
Fig36. Gitaru II and III rotor speed deviation response

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5.RESULTANALYSIS
The main objective of the project was to analyze the transient stability behavior of the system
when subjected to major disturbances comparing the transient stability of different types of
synchronous machines to that of turbine generator(s) with more power being injected into it from
Menengai geothermal field. From the results and discussion, it can be concluded that the systems
response to transient disturbances improved with more power injection. The transient response of
the turbo generator was better as compared to thermal and hydro generators taking reference of
Menengai power plant.
From the results obtained, it can be concluded Kenya is heading in the right direction with
proposal of having more power generation from geothermal considering a potential of
10,000MW from Menengai geothermal fields. This will ensure cheap and reliable source of
power which is advantageous to the economy as a whole.
From an engineering point of perspective, it can be viewed that geothermal power production is
very advantageous to the entire power system as it is subjected not to environmental changes as
compared to hydro power generation. This will ensure a relatively constant power being injected
to the system from it enabling the system to respond better during transient disturbances as seen
from the project’s simulation.
5.1 LIMITATIONS AND ASSUMPTIONSMADE
Though the project was successful, there were limitations to it like the data being incomplete due
to huddles in obtaining the actual data forcing the use of data from components of the same type
and use.
Assumptions were also made in the project like
 Only balanced three phase systems and balanced disturbances were considered. Therefore
only positive sequence networks were employed.

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REFERENCES
[1] J. D. Glover, Power System Analysis and Design, United States of
America: Thomson Learning, part of the Thomson Corporation,
2008.
[2] D. Das, Electrical Power System, New Delhi: New Age International
(P) publishers, 2006.
[3] P. Murty, Power System Analysis, Hyderabad: BS Publications,
2007.

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APPENDIX
APENDIX A-PROJECT TIME PLAN
ACTIVITY MAY
2015
JUN
2015
JUL
2015
AUG
2015
SEPT
2015
OCT
2015
NOV
2015
DEC
2015
DOCUMENTATION
PROPOSAL
WRITING
RESEARCH AND
LITERATURE
REVIEW
DESIGNING
SIMULATION
(KENYAN POWER
SYSTEM WITHOUT
MENENGAI
GEOTHERMAL
FIELD)
SIMULATION
(KENYAN POWER
SYSTEM
INCLUDING
MENENGAI
GEOTHERMAL
FIELD)
FINAL
PRESENTATION
Table1. Project time plan

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APPENDIX-BPROJECT BUDGET
ITEM QUANTITY PRICE PER PIECE AMOUNT IN
CASH
1. Printing and
stationary
- - 1500/=
2. Internet - - 3500/=
3. Transport - - 1500/=
4. Purchase of reading
materials
- - 2500/=
5. Correspondence - - 1000/=
TOTAL COST - - 10000/=
TableB.1 Projected Budget
APPENDIX-C THE KENYAN POWER SYSTEM DATA
Table C.1 Transmission line data

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Table C.2 Transformer data
Table C.3 Generator type and dynamic data
Fig C.1 Kenyan power system topology model 2013

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Fig C.2a Kenyan system modeled in DigSILENT

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Fig C.2b Kenyan system modeled in DigSILENT
The Kenyan power system shown above was modeled on two single line graphic pages then
connected through Kindaruma 132kV bus, Mang’u 132kV bus and Sultan Hamud 132kV bus.
This was by reason it not being able to fit in one page for present ability purposes.