- Electricity is the backbone of any modern society and economy. Therefore, economic growth and increa se in social wealth of a country usually lead to an increase in demand for electrical energy especially for a country as Nigeria. As the population of Nigeria is increasing exponentially, there exist a need to make basic needs constantly available , for the wel lbeing of the increasing population. This is possible through mechanization. Reliable a nd stable electricity supply is the surest means to this end. As a result, there is need to constantly review the dynamics of the power system while more energy sources a nd loads are being added to the existing power network g rid . This creates a demand for precise models for the corresponding network. In this paper , the power network system of the Nigerian transmission grid w as implemented at normal operations to include t he dynamic models to the corresponding net work elements (i.e. generation U nits based on their installed capacities and controllers). With the help of this model, stationary load flow calculations , as well as network’s model performance in steady state was c onducted. The network’s model performance in the case of load changes and fault operations was also carried out . These allowed for investigations on the stability status of the Nigerian transmission grid. Key Words : Power System S tability Analysis (RMS) , Dynami c Network Model, Nigerian Transmission Network, DigSILENT PowerFactory Analysis, Short Circuit Analysis , Load - Flow Calculations, Load Events. 1.INTRODUCTION Due to the present state and challenges facing the Nigerian Electricity market and industries, th ere are almost frequent power - cuts and long periods of power outage that are seen in some areas of the country. The frequent power - cuts affect the profiles of Bus - voltages which is seen in some areas having constant low and/ flickering voltages for long p eriods. This affects the stability of the entire power network. This is believed to be resulting from inefficient network modelling and no dynamics considerations in the usual stationary load flows performed by the National Control Centre (NCC) of the Nige rian Transmission company of Nigeria (TCN) . As a result, there is need to introduce it into the Nigerian Electricity network to enable us to constantly study the effective loadings of network elements at almost all instants as well as estimate the stabilit y of the entire network prior to addition or removal of any element in the existing infrastructure of the Nigerian Grid system. The scope of this research is limited to the highest voltage (HV) infrastructure in the Nigerian transmission power network, whi ch is the 330 kV Network. The Network operators step down voltage from 330 kV voltage network to 132 kV voltage network and then to 33 kV voltage network. This ends the transmission network of the Transmission Company of Nigeria (TCN). The main reason for this scope is predom inantly because almost all the power p lants in the Nigerian power network are connected to this voltage level after generation and so it serves as the intermediate grid in the entire network, thus making it the most sensitive, important and the most consciously monitored Grid by the TCN in Nigeria . 2. A brief on the Nigerian Electricity System Electricity generation in Nigeria was thought to have begun in 1896 during the British colonial times. In 1929, the first recognised electrica l com pany was set up to control electricity generation , transmission and distribution in the country. T he arm which was charged with power generation (then hydro plants power ) was known as the Nigerian Dams Authority (NDA) while the arm charged with the el ectricity transmission and distribution was known as the Electricity Corporation of Nigeria (ECN). Because of the country’s division into different regions, other electrical companies beg an springing up in various regions that saw to the running of the ele ctrici ty generation and consumption [1 ]. It was not until 1972 that the only hydroelectric company at that time – Nigerian Dams Authority, merged with the Electricity Corporation of Nigeria (ECN) – the conglomeration of the small companies, to found the Na tional Electrical Power Authority (NEPA). As this was the only federal parastatal that controlled electr icity generation in the country . They were in control of 94% of the total electricity generation and maintained 100% of the transmission, distribution, the marketing sector and the system operators [2 ]. T his monopoly hindered the needed development in the sector that later led to the deregulation of electric power in Nigeria [3 ]. After the deregulation, 11 distribution companies (DISCO) took over the dis tribution of electricity, 6 - generation companies (GENCO) took over the generation arm while the transmission company of Nigeria still manages the electricity transmission from 330kV to 33kV high voltage infrastructures in the electricity system of Nigeria. The power Page 2 plants owned by the Niger Delta Power Holding Company (NDPHC) are controlled by the three tiers of government in Nigeria (Federal, State and Local). These power plants are classified as being part of the National Integrated Power Project (NIPP) while others are wholly owned by the state governments and/or private companies/individuals. Such a power plant is refe rred to as an Independent Power Producer (IPP). A brief history and structure of the Nigerian electricity system is summarized in figure 1. Fig - 1 : Overview of the History of Nigerian Electricity System 2. THE N IGERIAN POWER NETWORK Electricity is generated in Nigeria between 10.5 kV to 16 kV from the generators in power p lant stations. From these voltage levels, they are stepped - up by transformers depending on the choice of the injection voltage level but mostl y to 330kV. Transmission of Electricity sets in immediately from this point. Transmission starts with the transportation of the generated power through the 330kV voltage network along transmission lines/conductors and is stepped - down by transformers to 132 kV at the transmission substations. This voltage is again transported along 132 kV transmission lines to the injection substations and stepped down by a transformer to 33 kV. This is where the Distribu tion of electricity starts. The voltage is further tr ansported along the 33 kV transmission lines and is stepped down to 11 kV which in turn , is stepped down again to 0.415 kV before it find its way to Ni gerian homes and/ offices [ 4 ]. Fig - 2 : How Electricity is transported to Nig erian Homes [ 4 ]. These normal procedures does not disprove the fact that there are other voltage levels (e.g. 66 kV etc.) used by industries in Nigeria but these are subject to specifi c voltage requirements of these industries . This is a function of their machines and equipment . Fig - 3 : Map of Nigerian Power Network [5 ] At present, the total installed generation capacity in the entire network based on the received data from Transmission Company of Nigeria (TCN) in November 20 18 is Ele ctricity Supply National Electricity Power Authority (NEPA) - 1972 Niger Dams Authority 4 Divisions: Generation and Transmission; Distribution and Sales; Engineering; Finance and Admin istration Electricity Corporation of Nigeria (ECN) Power Holding Company of Nigeria (PHCN) - 2005 Distribution (11 companies): - 2005 Abuja Electricity Distribution Company plc Benin Electricity Distribution Company plc Eko Electricity Distribution Company plc Enugu Electricity Distribution Company plc Ibadan Electricity Distribution Company plc Ikeja Electricity Company plc Jos Electric ity Distribution Company plc Kano Electricity Distribution Company plc Kaduna Electricity Distribution Company plc Port Harcourt Electricity Distribution plc Yola Electricity Distribution Company plc Generation ( 6 companies): - 2005 Enugu Afam Power plc Egbin Power plc Kainji Hydro - Electric plc Sapele Power plc Shiroro Hydro - Electric plc Ughelli Power plc National Transmission Company of Nigeria (TCN) - 2005 Existing TCN Network Page 3 approximately 12,908 MW. The Power plants that contribute to this Capacity comprises of less - decommi ssioned units and therefore, were used in the analysis of the stability of th e Nigerian network and Table 1 to Table 4 show their list . Table - 1: Priv atised Companies - Hydro Stations [5 ] Plant Installed Capacity (Less - Decommissioned Units) (MW) Kainji G.S (Niger) 760.00 Jebba G.S (Niger) 578.40 Shiroro 600.00 SUB - TOTAL 1,938.40 Table - 2 : Privatised Companies - Thermal Stations [5 ] Egbin (Lagos) 1,320.00 Sapele Steam (Delta) 720.00 Transcorp Delta II - IV G.S. (Delta) 900.00 Afam IV & V (Rivers) 351.00 Geregu G.S. (Kogi) 414.00 Omotosho G.S.(Ondo) 335.00 Olorunsogo (Ogun) 335.00 SUB - TOTAL 4,375.00 Table - 3 : NIPP - Thermal Stations [5 ] Sapel e NIPP (Delta) 500.00 Alaoji NIPP (Abia) 500.00 Olorunsogo NIPP (Ogun) 750.00 Geregu NIPP (Kogi) 450.00 Omotosho NIPP (Ondo) 500.00 Ihovbor NIPP (Edo) 500.00 Odukpani (Cross - River) 625.00 Gbarain (Bayelsa) 120.00 SUB - TOTAL 3,945.00 Table - 4: IPP - Thermal Stations [5 ] Okpai G.S (Delta) 480.00 Afam VI G.S (Rivers) 650.00 Asco G.S (Kogi) 110.00 Ibom G.S (Akwa Ibom) 155.00 AES (Lagos) 294.00 Trans - Amadi (Rivers) 100.00 Rivers IPP (Rivers) 180.00 Azura IPP (Edo) 459.00 Omoku G.S (Rivers) 150.00 Paras - Energy (Lagos) 72.00 SUB - TOTAL 2650.00 GRD TOT./WTD AVERAGE 12,908.40 3. IMPLEMENTED DYNAMIC COMPONENTS FOR THE NIGERIAN NETWORK The represent ation of the network dynamics was done using the standard dynamic models for synchronous machine and t heir control devices. The reason for the choice of the controllers is based on the condition to use s tandard IEEE r ecommended models in order to facilitate the tuning processes for better and expected results. The dynamic components of the Generators in th e power plant s listed in Table 1 to Table 4 were implemented. These included the Synchronous generator, the Turbine/Governor (TGOV), the Automatic Voltage Regulator (AVR), as well as Power System Stabilizer (PSS). Below are the graphic diagrams of the abov e components modelled in the network. 3.1 Power Plant Model A synchronous generator standard model in PowerFactory was used to define the characteristics of the power plants and their dynamic components in the design. The power plant frame is shown in fi gure 4 . The choice of this model is based on IEEE g uide for synchronous generator modeling practice and applications in pow er system stability analysis [ 6 ]. In the power plant frame shown below, it is important to state that the meter bus placed to introdu ce voltage and frequency measurements to the power system stabiliser (PSS) input, the over - excitation limiter (OEL) and the under - excitation limiter (UEL), all situated at the left side of the power plant frame was not considered in this design and therefo re does not contribute to the overall activity of the entire system. Fig - 4 : Standard Power Plant in PowerFactory [7 ]. Irrespective of the type of synchronous generator and the controllers used, the power plant frame in figur e 3 remains almost the same for most configurations . Hence, for any type of controller used depending on its input variables, the synchronous generator will deliver the necessary input variable s for efficient operation of its controllers. Page 4 Table - 5 : Genera tor Basic Signals Generator Input Signals Details ve Excitation voltage from the AVR pt Mechanical Turbine Power Output Signals Details ut Terminal voltage pgt Electrical Power fe/wf Frequency speed/xspeed Shaft speed xmt Mechanical Torque xme Ele ctrical Torque cosn Powerfactor Sgnn Apparent power 3 .2 Turbine/Governor Model A steam turbine converts the stored energy of high pressure and high temperature steam into a rotating energy. This energy is in turn converted into electrical energy by th e generator whose speed i s controlled by the governor [8 ]. In Nigeria, the heat source for the boiler s upplying the steam is typically fired by Liquefied natural gas (LNG). The Turbine/Governor models used in the design were of IEEE recommendations for dyn amic models of Turbine - Governor in power system studies [9 ]. Two models were used, one for the hydro - plant (HYGOV) and the other for the thermal plants (TGOV 1 ). In these two models (HYGOV and TGOV 1 ), the operations and basic signals are the same. The basic input signals of measured frequency and electrical power are compared at the summation point ( - ) against their reference set values in order to decode any deviation. The result of these deviations in the frequency and power to the reference values is nece ssary to enable creation of the necessary primary control Droop instruction needed to be fed into the controller for valve adjustment (steam/gas open/close time) in the event of any disturbance. The signal gate Limiter, which serves as valve adjustment reg ulator, is also placed alongside the necessary delay constant functions considering the effect of frictional losses and are also compared with other signals like the apparent power and powerfactor from the synchronous generator to be able to effect a contr olled change in the turbine input (pt) of that power plant. Fig - 5 : Frame of the Thermal Turbine - Governor (TGOV1) The important signal s to the studies are shown in T able 6. Table - 6: Turbine - Governor Basic Signals TGOV - Input S ignals Details Pgt Electrical Power Generated fe/wf Frequency Speed Synchronous machine speed Output Signals Details At Controlled valve relative position to the position Pt Mechanical Turbine Power fe/wf Frequency Sgnn Apparent power Cosn Powerfa ctor 3 .3 Automatic Voltage Regulator Model Here, the choice of the Automatic Voltage Regulator (AVR_SEXS) as the voltage regulator and the excitation system used for the synchronous generator was influenced by ENTSO - E in [ 10 ]. The basic operations of th e automatic voltage regulation of SEX standard is significantly the same with any other AVR device. One of its few advantages can be attributed to low number of input parameters as against many other standard models. It is important to state that the volt age input signals of OEL and UEL are not considered in this model. Page 5 Fig - 6 : Frame of the AVR Device (AVR_SEXS) in PowerF actory Here, the reference voltage (Usetp) alongside any bias (Vbias), terminal voltage (ut) and the volta ge output of the PSS (Upss) are compared. Any deviation at this stage is fed to the filter in the lead - lag block. The output of this filter is then fed into the excitation limiter controller. With the help of its gain, the controller output is tuned in suc h a way that its output signal, excitation voltage (ve/ueers), is to control the generator stator terminal voltage. Table - 7 : Automatic Voltage Regulator (AVR) Basic Signals AVR Input Signals Details ut Terminal voltage Upss Power system stabilizer (P SS) output Speed speed Pgt Electrical Power Usetp Reference voltage/voltage setpoint Output Signals Details ve/ueers Excitation voltage 3.4 Power System Stabilizer (PSS) Model Here, PSS is used to enhance damping of power system oscillations throug h excitation control. The PSS (i.e. PSS2A) standard model used in this design was influenced by the IEEE recommended practice for Excitation system models for po wer system stability studies [11 ]. The PSS2A standard Frame in Powerfactory is shown in figure 7. Fig - 7 : Frame of the PSS Devi ce in PowerFactory The Dual Input selector of the PSS2A model selects from the following input signals: 0 - Reference Speed (speed - ref), 1 - Speed (xspeed), 2 - Reference Frequency (f0), 3 - Frequency (fe), 4 - Power generated, 5 - Rotor angle, 6 - Mechanical torque (xmt), 7 - Electrical torque (xme), 8 - Terminal voltage (u), 9 - reference voltage/ Voltage set point (Usetp). The Ic1 - first input code, Ic2 - second input code, Input base (IPB) selector: 1 - Generator MV A, 0 - Generator MW base). From any input selected, Signal 1 and/ Signal 2, almost the same process is followed. The selected input signal either takes the MVA or MW base as assigned to it by the IPB selector, is fed into necessary first order lag differenti ators and then to the signal transducer block (T6 and T7) represented by their time constants. Again, their outputs are compared and the result fed into the Lead - Lag block which allows for ramp - tracking in the input signals. The output of the Lead - Lag blo ck is then compared with the gain - tuned input of the Signal 2 and the result fed into the PSS controller. The output at this stage is also fed into other necessary first and second Lead - Lag derivative and delay blocks which is responsible for the control of phase compensations. The output of this lead - Lag block serves as input to the voltage Limiter block used for excitation control to output the controlled - voltage signal input (Upss), which in turn, as an input to the AVR device, is used to add damping to the synchronous generator stator oscillations in the case of any disturbance in the network. Table - 7: Power System Stabiliser Basic Signals PSS - Input Signals Details fe/wf Frequency from Turbine - Governor ve Excitation voltage from AVR Speed Rotor Sp eed cosn Powerfactor Page 6 Pgt Electrical Power ut Terminal voltage Usetp Voltage setpoint xmt Mechanical torque xme Electrical torque Output Signals Details Upss Power system stabilizer (PSS) output 4 . LOAD FLOW CALCULATIONS A load flow calculation d etermines the voltage magnitude (V) and the voltage angle ( θ ) of the nodes, as well as the active (P) and reactive (Q) power flow on branches. In this design, Powerfactory was used to implement the Newton - Raphson (power equation, classical) method as its non - linear equation solver because of its fast - convergence n ature. This Newton - Raphson algorithm is sufficient for Load - flow calculations for large transmission systems, most especially when heavily loaded. This method was used for A.C. Load flow calculation during the top of the hour at Off – Peak Minimum (OPM - 8:00 Hours) and also at Maximum Power Flow (MPF - 22:00 Hours) The currents at stea dy state are calculated from [1 2 ]: where i=1,2,3,…m where m = 107 generators from 28 Power Plant sta tions. V i is the terminal voltage of the generator; and P i and Q i represents the true and reactive powers. For the 71 - bus system, the voltages at the nodes can be represented by the equation in matrix form given as:                     71 2 1 ... ... ... I I I =                     nn n n n n i n i Y Y Y Y Y Y Y Y Y Y Y Y ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... 1 2 1 2 2 22 21 1 1 12 11                     71 2 1 ... ... ... V V V Where n = 71= number of buses or simply put; I bus = Y bus V bus Where I bus is the vector of the injecting bus currents and V bus is the vector of bus voltages measured from the reference node. Y bus can also be referred to as the admittance matrix. The diagonal element of each node is the sum of admittances connected to it. It is also known as self - admittance given by [1 2 ]: Y ii =    n j ij y 0 where j ≠ i The off - diagonal element is equal to the negative of the ad mittance between the nodes. It is known as mutual admittance and it is shown below. Yij = Y ji = - y ij In summary, the flow chart for the Newton - Raphson Load flow calculation al gorithm is shown in figure 8 . Fig - 8 : Flow Chart for Load Flow Calculations us ing Newton - Raphson method [12 ] The figures below show the Single line diagram of the Load f low calculation in the DigSILENT PowerFactory software. Page 7 Fig - 9 a : Single Line Diagram of the Nigerian Transmission Grid (OPM; 08:00 Hours) Fig - 9b : Single Line Diagram of the Nigerian Transmission Grid (OPM; 08:00 Hours) Continuation Fig - 1 0a : Single Line Diagram of the Nigerian T ransmission Grid (MH; 22 :00 Hours) Fig - 1 0b : Single Line Diagram of the N igerian T ransmission Grid (MH; 22 :00 Hours) Continuation Page 8 Fig - 1 1a : Heat Map of the Single Line Diagram of the Nigerian T ransmission Grid (OPM; 08 :00 Hours) Fig - 1 1b : Heat Map of the Single Line Diagram of the Nigerian Transmission Grid (MH; 22:00 Hour s) 4 .1 Load flow calculation results during the top of the hour at Off – Peak Minimum (OPM) Hours Fig - 11a : Bus Voltage Profile in Per - Unit after Load Flow Calculations Fig - 11b : Bus Voltage Profile in Per - Unit after Load Flow Calculations (Continuati on) Page 9 Fig - 12a : Transmission Line Loadings in Percentage, % Fig - 12b : Transmission Line Loadings in Percentage, % (Continuation) 4 .2 Load Fl ow Calculation R esults during the top of the Maximum Hour (MH - 22:00 Hours) Power F low Fig - 13a : Bus Voltage Pr ofile in Per - Unit after Load Flow Calculations Fig - 13b : Bus Voltage Profile in Per - Unit after Load Flow Calculations (Continuation) Page 10 Fig - 14a : Transmission Line Loadings in Percentage, % Fig - 14b : Transmission Line Loadings in Percentage, % (Continu ation) 5 . STABILITY INVESTIGATIONS The Stability Analysis, RMS simulation (electromechanical transient) was implemented using previously discussed control devices following analysis and results were collected during the top of Maximum Hour power flow (MH - 22:00 Hours). This 22 - hours analysis is chosen because it is the hours of maximum power flow at maximum load utilities. For this study case, six (6) Buses, B’Kebbi (North - West), Osogbo NCC (South - West), New - Haven (South - East), Ikot - Ekpene (South - South), M aiduguri (North - East), including the Slack Bus, Egbin (West) were selected for the terminal voltage and frequency behaviour analysis. They were selected because of their strategic locations in the Nigerian Map. In addition, short circuit event was created on the longest line, B’Kebbi - Kainji (310km) with a switch event of 100ms. The behaviour of this short circuit event on the transmission network was monitored on the three (3) longest lines that included, B’Kebbi - Kainji (310km), Osogbo - Ikeja West (235km) an d New Haven - Ikot Ekpene (143km) lines, the above mentioned Buses in our case study as well as on the randomly selected Power Plants units, which included, the Egbin Plant (ST1 - slack machine), Shiroro (411G1 - hydro station), Sapele Gas GT1 (thermal station) and Asco Plant (thermal station). One of the importance of this short circuit analysis is to be able to simulate and investigate single and/ multiple faults as well as be able to check the ratings of network equipment during the planning period. Below are the results of the analysis as shown by DigSILENT PowerFactory software. Fig - 15a : Terminal Voltage Profile of Case study Bus Bars over 30 seconds at No Event Page 11 Fig - 15a : Terminal Voltage Profile of Case study Bus Bars over 30 seconds at No Event (Continuation) Fig - 15c : Terminal Voltage Profile of Case study Bus Bars over 30 seconds at B’Kebbi Load Event Fig - 15d : Terminal Voltage Profile of Case study Bus Bars over 30 seconds at B’Kebbi Load E vent (Continuation) Fig - 15e : Terminal Voltage Profile of Case study Bus Bars over 30 seconds at Ikeja - West Load Event Fig - 15f : Terminal Voltage Profile of Case study Bus Bars over 30 seconds at Ikeja West Load Event (Continuation) Fig - 15g : Fre quency Profile of Case study Bus Bars over 30 seconds at No Event Page 12 Fig - 15h : Frequency Profile of Case study Bus Bars over 30 seconds at No Event (Continuation) Fig - 15i : Frequency Profile of Case study Bus Bars over 30 seconds at B’Kebbi Load Event Fig - 15i : Frequency Profile of Case study Bus Bars over 30 seconds at B’Kebbi Load Event (Continuation) Fig - 15j : Frequency Profile of Case study Bus Bars over 30 seconds at Ikeja - West Load Event Fig - 15k : Frequency Profile of Case study Bus Bars o ver 30 seconds at Ikeja - West Load Event (Continuation) Various characteristics of the selected network elements to the Short Circuit Event at B’Kebbi - Kainji transmission line (310 km) over 30 seconds are shown below . Fig - 16a : Voltage Profile of Case s tudy Bus Bars over 30 seconds at B’Kebbi - Kainji Line Short Circuit Event Page 13 Fig - 16b : Voltage Profile of Case study Bus Bars over 30 seconds at B’Kebbi - Kainji Line Short Circuit Event (Continuation) Fig - 16c : Frequency Profile of Case study Bus Bars over 30 seconds at B’Kebbi - Kainji Line Short Circuit Event Fig - 16d : Frequency Profile of Case study Bus Bars over 30 seconds at B’Kebbi - Kainji Line Short Circuit Event (Continuation) Fig - 17a : Total Active Power/Terminal i (MW) of Case study Lines over 30 seconds at No Event Fig - 17b : Total Reactive Power/Terminal i (MVar ) of Case study Lines over 30 seconds at No Event Fig - 17 c : Total Active Power/Terminal i (M W) of case study Lines over 30 sec onds at B’Kebbi - Kainji Short Circuit Event Page 14 Fig - 17d: Total Reactive Power/T erminal i (M Var ) of case study Lines over 30 seconds at B’Kebbi - Kainji Short Circuit Event Fig - 18a : Rotor Angle Profile of Case study Power Plants over 30 seconds at No Event Fig - 18b : Rotor Angle Profile of Case study Power Plants over 30 seconds at B’Kebbi - Kainji Line Short Circuit Event 6. SUMMARY AND CONCLUSION From the entire characteristic figures shown in part 5, it is clear that the voltage and frequency characteri stics of the modelled dynamic components of the Nigerian transmission network resulted to expected and favourable outcomes, prior to addition of further controllers to increase fast damping during system oscillations because of transient events. This shows in a greater extent the accuracy and fitting of the standard dynamic models used in the Nigerian transmission network modelling and suggest their suitability in the fu ture power system analysis and operational procedure follow - up of the Nigerian transmiss ion Network. T his research have succeeded in exposing the stability of the Nigerian Transmission Network. The fact that the National Control Center (NCC) of the Transmission Company of Nigeria (TCN) do not perform system dynamics is evident in the epilep tic power supply that Nigeria is currently battling at any careless disturbance. The dynamic models of the power plants helped to understand the behaviour of the critical network parameters and as such will help in understanding the effect of any contingen cy in the network. The importance of these dynamic models implementation is far beyond this project as it serves as the platform for all other analysis and any electrical parameter investigation that maybe of interest to the system operators, the National Electricity Regulatory Commission (NERC), the National Control Center and/ the research Academia. These can include but are not limited to Modal Analysis, further transient analysis, Contingency Analysis, short circuit single o r multiple fault analysis an d other investigations . These analyses are important in the Nigerian context especially during the case of load shading, generators out of operation due to faults or maintenance, integration of renewable energy sources into the Grid etc. Page 15 APPENDIX A: Trans mission Line Data Line Name Grid Par. no. Length Max. Limiting Current kV km kA Adiabor - Odukpani 330 1 18 1.36 Afam IV_V - Port Harcourt 330 2 45 2.72 Afam VI - Alaoji 330 2 25 2.72 Afam V I - Ikot Ekpene 330 2 90 2.72 Ahoada - Yenegoa 132 2 46 0.8 Aj a - Alagbon 330 2 26 2.72 Aja - Egbin 330 2 14 2.72 Ajaokuta Benin 330 1 195 1.36 Ajaokuta - Geregu 330 2 5 2.72 Ajaokuta - Lokoja 330 2 38 2.72 Aladja - Delta 330 1 32 1.36 Aladja - Sapele NIPP 330 1 63 1.36 Alaoji G.S - Alaoji T.S 330 2 5 2.72 Alaoji - I kot Ekpene 330 2 38 2.72 Alaoji - Onitsha 330 1 138 1.36 Alaoji - Owerri 330 2 60 2.72 Aliade Ugwuaji - Makurdi 330 2 50 2.72 Aliade - N/Haven South 330 2 150 2.72 Ayede - Ikeja West 330 1 137 1.36 Ayede - Osogbo 330 1 115 1.36 Azura - Benin 330 2 5 2.72 B 'Kebbi - Kainji 330 1 310 1.36 Benin North - Ajaokuta 330 2 195 2.72 Benin North - Eyaen 330 2 5 2.72 Benin - Benin North 330 2 20 2.72 Benin - Delta 330 2 107 2.72 Benin - Egbin 330 2 218 2.72 Benin - Ikeja West 330 2 280 2.72 Benin - Omotosho 330 2 120 2.72 Be nin - Onitsha 330 2 137 2.72 Benin - Osogbo 330 1 251 1.36 Benin - Sapele G.S 330 2 50 2.72 Calabar - Ikot Ekpene 330 2 72 2.72 Damaturu - Gombe 330 1 160 1.36 Damaturu - Maiduguri 330 1 260 1.36 Egbema - Omoku 330 2 30 2.72 Egbema - Owerri 330 2 30 2.72 Egbin - Er unkan 330 2 30 2.72 Egbin - Ikeja West 330 2 62 2.72 Erunkan - Ikeja West 330 1 32 1.36 Ganmo - Osogbo 330 1 87 1.36 Gbaran - Yenegoa 132 2 5 0.8 Gombe - Yola 330 2 217 2.72 Gwags - Katampe 330 2 30 2.72 Gwags - Lokoja 330 2 140 2.72 Gwags - Shiroro 330 2 114 2.7 2 Ibom - Ikot - Abasi 330 2 5 2.72 Ihovbor - Osogbo 330 1 5 1.36 Ikeja West - Akangba 330 1 18 1.36 Ikeja West - Omotosho 330 1 160 1.36 Ikeja West - Osogbo 330 1 252 1.36 Ikot_ Abasi - Ikot Ekpene 330 2 75 2.72 Ikot Ekpene - N/Haven South 330 2 143 2.72 Jaling o - Yola 330 2 132 2.72 Jebba G.S - Jebba T.S 330 2 8 2.72 Jebba - Ganmo 330 1 70 1.36 Jebba - Kainji T.S 330 2 81 2.72 Jebba - Osogbo T.S 330 1 157 1.36 Jebba - Shiroro 330 2 244 2.72 Jos - Gombe 330 2 265 2.72 Jos - Makurdi 330 2 230 2.72 Kaduna - Kano 330 1 230 1.36 Kaduna - Shiroro 330 2 96 2.72 Kainji G.S - Kainji T.S 330 2 0.47 2.72 Katampe - Shiroro 330 2 144 2.72 N/Haven - N/Haven South 330 2 5 2.72 N/Haven - Onitsha 330 2 96 2.72 Odukpani - Ikot Ekpene 330 2 5 2.72 Okearo - Egbin 330 2 30 2.72 Okear o - Ikeja West 330 2 32 2.72 Okpai - Onitsha 33 0 2 80 2.72 Omoku - Port Harcourt 330 1 5 1.36 Onitsha - Owerri 330 2 137 2.72 Owerri 132kv - Ahoda 132 2 73 0.8 Papalanto - Ayede 330 1 60 1.36 Papalanto - Ikeja West 330 2 30 2.72 Paras Energy - Ikorodu 330 2 18 0.8 Rivers IPP - Port Harcourt 330 2 5 2.72 Sakete - Ikeja West 330 1 70 1.36 TransAmadi - Port - Harcourt 330 2 5 2.72 Page 16 Kaduna - Jos 330 1 197 1.36 Typical 330 kV Transmission Line parameters used R1 R0 X1 X0 B1 B0 Y1 Y0 C1 C0 Ω/k m Ω/ k m Ω/ km Ω/ km µS / k m µS /k m µS /k m µS /k m µF/ km µF/k m 0.0 39 4 0. 27 4 0. 33 1 0. 99 7 3.4 9 2.4 9 3.4 9 2.4 9 0.01 213 4 0.007 3052 Typical 132 kV Transmission Line parameters used: R1 R0 X1 X0 B1 B0 Y1 Y0 C1 C0 Ω/ k m Ω/ k m Ω/ k m Ω/ k m µS /k m µS /k m µS /k m µS /k m µF /k m µF/k m 0. 12 3 0. 31 5 0. 39 2 1. 34 9 2.9 93 1.7 9 2.9 93 1.7 9 0.00 1085 3 0.00 1778 3 APPENDIX B : Generator Basic Data Name Grid k V TypeSym Plant Catego ry AES GT1 Plant 330 AES Plant Gas AES GT2 Plant 330 AES Plant Gas Afam I - III 1 330 Afam I - III Plant Gas Afam I - III 2 330 Afam I - III Plant Gas Afam I - III 3 330 Afam I - III Plant Gas Afam IV - VI GT1 33 0 Afam IV - VI Plant Gas Afam IV - VI GT2 330 Afam IV - VI Plant Gas Afam IV - VI GT3 330 Afam IV - VI Plant Gas Afam IV - VI GT4 330 Afam IV - VI Plant Gas Alaoji NIPP GT 1 330 Alaoji Plant Gas Alaoji NIPP GT2 330 Alaoji Plant Gas Alaoji NIPP GT3 330 Alaoji Plant Gas Asco Plant 330k V Asco Plant Gas Azura IPP GT1 330 Azura IPP Plant Gas Azura IPP GT2 330 Azura IPP Plant Gas Azura IPP GT3 330 Azura IPP Plant Gas Azura IPP GT4 330 Azura IPP Plant Gas Egbin ST1 330 Egbin Plant Steam Egbin ST2 330 Egbin Plant Steam Egbin ST3 330 Egbin Plant Steam Egbin ST4 330 Egbin Plant Steam Egbin ST5 330 Egbin Plant Steam Egbin ST6 330 Egbin Plant Steam Gbaran Plant 330 Gbaran P lant Gas Geregu GT1 330 Geregu - GT1 - GT3 Plant Gas Geregu GT2 330 Geregu - GT1 - GT3 Plant Gas Geregu GT3 330 Geregu - GT1 - GT3 Plant Gas Geregu NIPP 1 330 Geregu NIPP Plant Gas Geregu NIPP 2 330 Geregu NIPP Plant Gas Geregu NIPP 3 330 Geregu NIPP Plant Gas Geregu NIPP 4 330 Geregu NIPP Plant Gas Ibom Power 330 Ibom Power Plant Gas Ihovbor NIPP GT1 330 Ihovbor NIPP Plant Gas Ihovbor NIPP GT2 330 Ihovbor NIPP Plant Gas Ihovbor NIPP GT3 330 Ihovbor NIPP Plant Gas Ihovbor NIPP GT4 330 Ihovbor NIPP Plant Gas Jebba 2G1 330 Jebba Plant Hydro Jebba 2G2 330 Jebba Plant Hydro Jebba 2G3 330 Jebba Plant Hydro Jebba 2G4 330 Jebba Plant Hydro Jebba 2G5 330 Jebba Plant Hydro Jebba 2G6 330 Jebba Plant Hydro Kainji 1G10 330 Kainji Plant Hydro Kainji 1G11 330 Kain ji Plant Hydro Kainji 1G12 330 Kainji Plant Hydro Kainji 1G5 330 Kainji Plant Hydro Kainji 1G6 330 Kainji Plant Hydro Kainji 1G7 330 Kainji Plant Hydro Kainji 1G8 330 Kainji Plant Hydro Kainji 1G9 330 Kainji Plant Hydro Odukpani GT1 330 Odukpani Pla nt Gas Odukpani GT2 330 Odukpani Plant Gas Odukpani GT3 330 Odukpani Plant Gas Odukpani GT4 330 Odukpani Plant Gas Odukpani GT5 330 Odukpani Plant Gas Okpai GT1 330 Okpai GT1 - GT3 Gas Okpai GT2 330 Okpai GT1 - GT3 Gas Okpai GT3 330 Okpai GT1 - GT3 Gas Page 17 O lorunsogo NIPP GT1 330 Olorunsogo NIPP Plant Gas Olorunsogo NIPP GT2 330 Olorunsogo NIPP Plant Gas Olorunsogo NIPP GT3 330 Olorunsogo NIPP Plant Gas Olorunsogo NIPP GT4 330 Olorunsogo NIPP Plant Gas Olorunsogo NIPP GT5 330 Olorunsogo NIPP Plant Gas Om oku Unit 1 GT1 - GT3 330 Omoku Plant Gas Omoku Unit 2 GT1 - 3 330 Omoku Plant Gas Omotosho GT1 330 Omotosho Plant Gas Omotosho GT2 330 Omotosho Plant Gas Omotosho GT3 330 Omotosho Plant Gas Omotosho NIPP GT1 330 Omotosho NIPP Plant Gas Omotosho NIPP GT2 330 Omotosho NIPP Plant Gas Omotosho NIPP GT3 330 Omotosho NIPP Plant Gas Omotosho NIPP GT4 330 Omotosho NIPP Plant Gas Omotosho NIPP GT5 330 Omotosho NIPP Plant Gas Papal/Oloruns ogo PH1 G1 330 Papalanto/Oloruns ogo Plant Gas Papal/Oloruns ogo PH1 G2 33 0 Papalanto/Oloruns ogo Plant Gas Papal/Oloruns ogo PH1 G3 330 Papalanto/Oloruns ogo Plant Gas Papal/Oloruns ogo PH1 G4 330 Papalanto/Oloruns ogo Plant Gas Papal/Oloruns ogo PH1 G5 330 Papalanto/Oloruns ogo Plant Gas Papal/Oloruns ogo PH1 G6 330 Papalanto/Olor un sogo Plant Gas Papal/Oloruns ogo PH1 G7 330 Papalanto/Olorun sogo Plant Gas Papal/Oloruns ogo PH1 G8 330 Papalanto/Olorun sogo Plant Gas Paras - Energy Plant 330 Paras - Energy Plant Gas Rivers IPP GT1 330 Rivers IPP Plant Gas Rivers IPP GT2 330 Rivers IPP Plant Gas Sapele Gas GT1 330 Sapele Gas Plant Gas Sapele Gas GT2 330 Sapele Gas Plant Gas Sapele Gas GT3 330 Sapele Gas Plant Gas Sapele Gas GT4 330 Sapele Gas Plant Gas Sapele Gas GT5 330 Sapele Gas Plant Gas Sapele Steam ST1 330 Sapele Steam Plant Steam Sapele Steam ST2 330 Sapele Steam Plant Steam Sapele Steam ST3 330 Sapele Steam Plant Steam Sapele Steam ST4 330 Sapele Steam Plant Steam Sapele Steam ST5 330 Sapele Steam Plant Steam Sapele Steam ST6 330 Sapele Steam Plant Steam Shiroro 411G1 330 Shiroro Plant Hydro Shiroro 411G2 330 Shiroro Plant Hydro Shiroro 411G3 330 Shiroro Plant Hydro Shiroro 411G4 330 Shiroro Plant Hydro Trans - Amadi Plant 330 Trans - Amadi Plant Gas Transcorp Delta I - III Plant 1 330 Transcorp Delta Plant 1 Gas Trans corp GT15 Plant 2 330 Transcorp Plant 2 Gas Transcorp GT16 Plant 2 330 Transcorp Plant 2 Gas Transcorp GT17 Plant 2 330 Transcorp Plant 2 Gas Transcorp GT18 Plant 2 330 Transcorp Plant 2 Gas Transcorp GT20 Plant 2 330 Transcorp Plant 2 Gas APPENDIX C : Generator Data used Name Active Pow er Reactiv Pow er Appar. Power Power Factor MW Mvar MVA AES - GT1 Plant 147 110.25 183.75 0.8 AES - GT2 Plant 147 110.25 183.75 0.8 Afam I - III 1 117 87.75 146.25 0.8 Afam I - III 2 117 87.75 146.25 0.8 Afam I - III 3 1 17 87.75 146.25 0.8 Afam - IV - VI GT1 162.503 100.710 3 191.18 0.85 Afam - IV - VI GT2 162.503 100.710 3 191.18 0.85 Afam - IV - VI GT3 162.503 100.710 3 191.18 0.85 Afam - IV - VI GT4 162.503 100.710 3 191.18 0.85 Alaoji - NIPP GT1 166.668 103.291 5 196.08 0.85 Alaoji - NI PP GT2 166.668 103.291 5 196.08 0.85 Page 18 Alaoji - NIPP GT3 166.668 103.291 5 196.08 0.85 Asco Plant 110.032 5 68.192 129.45 0.85 Azura - IPP GT1 114.75 55.5759 6 127.5 0.9 Azura - IPP GT2 114.75 55.5759 6 127.5 0.9 Azura - IPP GT3 114.75 55.5759 6 127.5 0.9 Azura - IPP GT4 114.75 55.5759 6 127.5 0.9 Egbin ST1 219.996 106.549 0 244.45 0.9 Egbin ST2 219.996 106.548 9 244.44 0.9 Egbin ST3 219.996 106.548 9 244.44 0.9 Egbin ST4 219.996 106.548 9 244.44 0.9 Egbin ST5 219.996 106.548 9 244.44 0.9 Egbin ST6 219.996 106.548 9 244 .44 0.9 Gbaran Plant 120 90 150 0.8 Geregu GT1 138 85.5247 6 162.353 0.85 Geregu GT2 138 85.5247 6 162.353 0.85 Geregu GT3 138 85.5247 6 162.353 0.85 Geregu NIPP 1 112.5 36.9769 6 118.421 1 0.95 Geregu NIPP 2 112.5 36.9769 5 118.421 1 0.95 Geregu NIPP 3 11 2.5 36.9769 5 118.421 1 0.95 Geregu NIPP 4 112.5 36.9769 6 118.421 1 0.95 Ibom Power 155 116.25 193.75 0.8 Ihovbor NIPP GT1 125 93.75 156.25 0.8 Ihovbor NIPP GT2 125 93.75 156.25 0.8 Ihovbor NIPP GT3 125 93.75 156.25 0.8 Ihovbor NIPP GT4 125 93.75 156.25 0.8 Jebba 2G1 96.407 59.7476 9 113.42 0.85 Jebba 2G2 96.407 59.7476 9 113.42 0.85 Jebba 2G3 96.407 59.7476 9 113.42 0.85 Jebba 2G4 96.407 59.7476 9 113.42 0.85 Jebba 2G5 96.407 59.7476 113.42 0.85 9 Jebba 2G6 96.407 59.7476 9 113.42 0.85 Kainji 1G10 95 3 1.2249 9 100 0.95 Kainji 1G11 95 31.2249 9 100 0.95 Kainji 1G12 95 31.2249 100 0.95 Kainji 1G5 95 31.2249 9 100 0.95 Kainji 1G6 95 31.2249 9 100 0.95 Kainji 1G7 95 31.2249 9 100 0.95 Kainji 1G8 95 31.2249 9 100 0.95 Kainji 1G9 95 31.2249 9 100 0.95 Odukpa ni GT1 125.001 77.4686 6 147.06 0.85 Odukpani GT2 125.001 77.4686 6 147.06 0.85 Odukpani GT3 125.001 77.4686 6 147.06 0.85 Odukpani GT4 125.001 77.4686 6 147.06 0.85 Odukpani GT5 125.001 77.4686 6 147.06 0.85 Okpai GT1 160.080 5 99.2089 9 188.33 0.85 Okpai GT2 160.080 5 99.2089 9 188.33 0.85 Okpai GT3 160.080 5 99.2089 9 188.33 0.85 Olorunsogo NIPP GT1 150.001 2 72.6489 2 166.668 0.9 Olorunsogo NIPP GT2 150.001 2 72.6489 2 166.668 0.9 Olorunsogo NIPP GT3 150.001 2 72.6489 2 166.668 0.9 Olorunsogo NIPP GT4 150.001 2 72.6489 2 166.668 0.9 Olorunsogo NIPP GT5 150.001 2 72.6489 2 166.668 0.9 Omoku Unit 1 GT1 - GT3 75 56.25 93.75 0.8 Omoku Unit 2 GT1 - 3 75 56.25 93.75 0.8 Omotosho GT1 111.667 2 83.7504 139.584 0.8 Omotosho GT2 111.667 2 83.7504 139.584 0.8 Omotosho GT3 11 1.667 2 83.7504 139.584 0.8 Omotosho NIPP GT1 100 75 125 0.8 Omotosho 100 75 125 0.8 Page 19 NIPP GT2 Omotosho NIPP GT3 100 75 125 0.8 Omotosho NIPP GT4 100 75 125 0.8 Omotosho NIPP GT5 100 75 125 0.8 Papal/Oloru n PH1 G1 41.88 31.41 52.35 0.8 Papal/Oloru n PH 1 G2 41.88 31.41 52.35 0.8 Papal/Oloru n PH1 G3 41.88 31.41 52.35 0.8 Papal/Oloru n PH1 G4 41.88 31.41 52.35 0.8 Papal/Oloru n PH1 G5 41.88 31.41 52.35 0.8 Papal/Oloru n PH1 G6 41.88 31.41 52.35 0.8 Papal/Oloru n PH1 G7 41.88 31.41 52.35 0.8 Papal/Oloru n PH1 G8 41.88 31.41 52.35 0.8 Paras - Energy Plant 72 34.8711 9 80 0.9 Rivers_IPP GT1 90.0022 5 55.7783 9 105.885 0.85 Rivers - IPP GT2 90.0022 5 55.7783 9 105.885 0.85 Sapele - Gas GT1 100 75 125 0.8 Sapele - Gas GT2 100 75 125 0.8 Sapele - Gas GT3 100 75 125 0.8 Sapele - Gas GT4 100 75 125 0.8 Sapele - Gas GT5 100 75 125 0.8 Sapele Steam ST1 120.006 58.1215 6 133.34 0.9 Sapele Steam ST2 120.006 58.1215 6 133.34 0.9 Sapele Steam ST3 120.006 58.1215 6 133.34 0.9 Sapele Steam ST4 120.006 58.1215 6 133.34 0.9 Sapele Ste am ST5 120.006 58.1215 6 133.34 0.9 Sapele Steam ST6 120.006 58.1215 6 133.34 0.9 Shiroro 411G1 150.025 92.9771 6 176.5 0.85 Shiroro 411G2 150.025 92.9771 3 176.5 0.85 Shiroro 411G3 150.025 92.9771 3 176.5 0.85 Shiroro 411G4 150.025 92.9771 3 176.5 0.85 Tr ans - Amadi Plant 100 48.4322 2 111.111 1 0.9 Transcorp Delta_I - III Plant 1 335 251.25 418.75 0.8 Transcorp GT15 Plant 2 113.000 7 70.0315 5 132.942 0.85 Transcorp GT16 Plant 2 113.000 7 70.0315 5 132.942 0.85 Transcorp GT17 Plant 2 113.000 7 70.0315 5 132.942 0 .85 Transcorp GT18 Plant 2 113.000 7 70.0315 5 132.942 0.85 Transcorp GT20 Plant 2 113.000 7 70.0315 5 132.942 0.85 APPENDIX D : Compensator s in the Network Bus Name Grid Qmax kV Mvar Ajaokuta 330 75 Alaoji 330 75 B'Kebbi 330 30 Benin 330 2 x 75 Go mbe 330 2 x 50 Ikeja West 330 2 x 75 Jebba G.S 330 2 x 75 Jos 330 75 Kaduna 330 75 Kano 330 75 Katampe 330 75 Lokoja 330 75 Makurdi 330 75 Ncc Osogbo 330 75 Okearo 330 75 Onitsha 330 75 Yola 330 2 x 30 Page 20 ACKNOWLEDGEMENT I want to use this opportunity to appreciate and thank my hig hly esteemed and distinguished Professor, Prof. Dr. - Ing Harald Weber and Martin Töpfer , Msc., for their tenacity in the realization and success of this research . My immense gratitude goes to DigSILENT G mbH for providing me with a free PowerFactory license, one of the world’s most powerful software tool for power system analysis. It is indeed a great privilege. My undiluted appreciation also goes to Engr. Nnajide Charles , Mr. Ilobi Izuchukwu and the entir e staff of the National Control Center Osogbo, of the Transmission Company of Nigeria and Egbin power station for their openness and support in the provision of the necessary and available data needed for this research . Lastly, but not the least, to Mr. Nn oli Stan for funding the entire fieldwork.