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www.tjprc.org SCOPUS Indexed Journal [email protected] SIMULATION STUDY AND PERFORMANCE ANALYSIS FOR THE INTERACTION BETWEEN NPP AND ELECTRICAL GRID BASED ON MATLAB SIMULINK ASMAA M. ELSOTOHY 1 , MOHAMED A. MEHANNA 2 , AYMAN A. EISA 3 & AHMED S. ADAIL 4 1,3 Department of Nuclear Safety and Radiological Emergencies, NCRRT, Atomic Energy Authority, Egypt 2 Department of Electrical Machines and power Engineering, Al Azhar University, Egypt 4 Department of Fuel Technology, Hot Laboratory Centre, Atomic Energy Authority, Egypt ABSTRACT The electrical voltage is one of the important parameters, which must be considered to assure the safety of any power system. The secure, safe and reliable operation of Nuclear power plants (NPPs) needs many studies for the interaction between the NPP and Electrical Grid. This paper presents an analysis to show the mutual interface between electrical grid and NPP under different scenarios of abnormalities on both the electrical grid and NPP. The pressurized water reactor (PWR) NPP mathematical models are presented in MATLAB/ Simulink. The responses of NPP key parameters under step increase and decrease in power demand were studied and presented to evaluate and assess the load following ability of the NPP. Then the weighted least squares (WLS) state estimation method is used to study the IEEE 30-bus system response for a sudden shut down and generation loss of NPP by 50%. The IEEE 30 bus system voltage profile is presented and analysed. This study can contribute to understand the performance of both NPP and electrical grid under different scenarios of expected disturbances and this can offer certain guidance for the engineering practice. KEYWORDS: Electrical Grid, NPP, IEEE-30 Bus System, Bus Voltage & Matlab/Simulink Received: Feb 20, 2020; Accepted: Mar 10, 2020; Published: Jun 05, 2020; Paper Id.: IJMPERDJUN202083 1. INTRODUCTION The power of NPP has been developing continually in the world, and it is expected to grow greatly in the coming years [14]. Owing to the NPP high safety requirements and high capacity, large abnormalities in electrical systems may influence seriously on NPP and electrical grids. Thus, ensuring the power networks and NPPs stability and safety is an important issue [5]. Up to the present time, for safety, economic and environmental considerations, most NPPs operate as base load stations without participating in the power grid frequency control. A reliable and stable electrical grid (with reliable distribution systems, transmission systems and production units) is an essential to the NPP safety [6]. As shown in figure (1), the Output from the generating unit (NPP) is fed to the electrical grid via the generator transformer. During the normal operation, the electrical power is fed to NPP auxiliaries from the NPP generating unit via the unit transformers. NPP auxiliaries can be supplied from the electrical grid when the generator is shut down by opening the generator breaker in the connection to the generator terminals. To provide an independent electrical power supply to NPP auxiliary equipment, one or more station Original Article International Journal of Mechanical and Production Engineering Research and Development (IJMPERD) ISSN (P): 22496890; ISSN (E): 22498001 Vol. 10, Issue 3, Jun 2020, 933-950 © TJPR Pvt. Ltd.

SIMULATION STUDY AND PERFORMANCE ANALYSIS FOR THE … · 2020. 6. 16. · The pressurized water reactor (PWR) ... load stations without participating in the power grid frequency control

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  • www.tjprc.org SCOPUS Indexed Journal [email protected]

    SIMULATION STUDY AND PERFORMANCE ANALYSIS FOR THE INTERACTION

    BETWEEN NPP AND ELECTRICAL GRID BASED ON MATLAB SIMULINK

    ASMAA M. ELSOTOHY1, MOHAMED A. MEHANNA2,

    AYMAN A. EISA3 & AHMED S. ADAIL4

    1,3Department of Nuclear Safety and Radiological Emergencies, NCRRT, Atomic Energy Authority, Egypt

    2Department of Electrical Machines and power Engineering, Al Azhar University, Egypt

    4Department of Fuel Technology, Hot Laboratory Centre, Atomic Energy Authority, Egypt

    ABSTRACT

    The electrical voltage is one of the important parameters, which must be considered to assure the safety of any power

    system. The secure, safe and reliable operation of Nuclear power plants (NPPs) needs many studies for the interaction

    between the NPP and Electrical Grid. This paper presents an analysis to show the mutual interface between electrical grid

    and NPP under different scenarios of abnormalities on both the electrical grid and NPP. The pressurized water reactor

    (PWR) NPP mathematical models are presented in MATLAB/ Simulink. The responses of NPP key parameters under step

    increase and decrease in power demand were studied and presented to evaluate and assess the load following ability of the

    NPP. Then the weighted least squares (WLS) state estimation method is used to study the IEEE 30-bus system response

    for a sudden shut down and generation loss of NPP by 50%. The IEEE 30 bus system voltage profile is presented and

    analysed. This study can contribute to understand the performance of both NPP and electrical grid under different

    scenarios of expected disturbances and this can offer certain guidance for the engineering practice.

    KEYWORDS: Electrical Grid, NPP, IEEE-30 Bus System, Bus Voltage & Matlab/Simulink

    Received: Feb 20, 2020; Accepted: Mar 10, 2020; Published: Jun 05, 2020; Paper Id.: IJMPERDJUN202083

    1. INTRODUCTION

    The power of NPP has been developing continually in the world, and it is expected to grow greatly in the coming

    years [1–4]. Owing to the NPP high safety requirements and high capacity, large abnormalities in electrical systems

    may influence seriously on NPP and electrical grids. Thus, ensuring the power networks and NPPs stability and

    safety is an important issue [5].

    Up to the present time, for safety, economic and environmental considerations, most NPPs operate as base

    load stations without participating in the power grid frequency control.

    A reliable and stable electrical grid (with reliable distribution systems, transmission systems and

    production units) is an essential to the NPP safety [6].

    As shown in figure (1), the Output from the generating unit (NPP) is fed to the electrical grid via the

    generator transformer. During the normal operation, the electrical power is fed to NPP auxiliaries from the NPP

    generating unit via the unit transformers. NPP auxiliaries can be supplied from the electrical grid when the

    generator is shut down by opening the generator breaker in the connection to the generator terminals.

    To provide an independent electrical power supply to NPP auxiliary equipment, one or more station

    Orig

    ina

    l Article

    International Journal of Mechanical and Production

    Engineering Research and Development (IJMPERD)

    ISSN (P): 2249–6890; ISSN (E): 2249–8001

    Vol. 10, Issue 3, Jun 2020, 933-950

    © TJPR Pvt. Ltd.

  • 934 Asmaa M. Elsotohy, Mohamed A. Mehanna, Ayman A. Eisa & Ahmed S. Adail

    Impact Factor (JCC): 8.8746 SCOPUS Indexed Journal NAAS Rating: 3.11

    transformers provide the second connection to the grid [7]. This redundancy in power sources to NPP auxiliaries plays an

    important role for nuclear safety which is called defence in depth concept.

    There are an important technical issues related with the electrical grid –NPP interface. Among these issues are the

    sudden increasing or reduction in the electrical power required to supply various consumers or tripping of NPP, which

    supplying a major portion of the electrical grid load, these previous disturbances can result leads to an imbalance between

    load and the available generation and effect on the grid’s voltage and frequency.

    Frequency is one of the important parameters in power system operation, so that for the power system safety and

    quality of power delivery Frequency should be maintained around its nominal value. Deviation of the frequency is usually

    initiated from the imbalance between power production of generating units and the grid load. When generating units' power

    production is smaller than the gird load, the system frequency will drop. In reverse, the frequency will rise when the power

    production is larger than the load of the electrical grid. Since the disturbance of grid load is a problem that cannot be

    eliminated due to the load demand changing of consumers, the fluctuation of frequency is unavoidable, which needs to be

    monitored continuously and controlled within safe levels [8].

    To study the interaction between electrical grid and NPP, a detailed model of NPP is required to obtain an overall

    picture of what happened in the plant. In the previous studies, there are some detailed models for nuclear power plant have

    been proposed for power system stability analysis, among them, some are linear models [9-11] which cannot be used for

    large abnormalities such as load rejection. Other models were nonlinear, but some factors that are very important for power

    system are not taken into consideration and took a large number of assumptions that used to simplify the model such as

    simplifying the reactor model into one fuel node and two coolant nodes, so that the NPP model cant reflect accurately the

    interactions between NPPs and the electrical grid [12-17]. In this study, some of previous factors are taken into account, so

    the model becomes able to simulate the dynamic behavior of electrical grid and NPP.

    This paper presents a model for the Westinghouse PWR NPP using Matlab/ Simulink. Based on this detailed

    model, the dynamic responses of NPP under the change of electrical grid loads are studied. Also, impact of the plant

    tripping and loss of NPP generation by 50% on the IEEE 30 bus system voltage profile are studied.

    Figure 1: Electrical Power Systems of NPP [7].

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    2. MATHEMATICAL MODEL OF NPP

    The NPP can be divided into nuclear steam supply system (NSSS) and balance of plant (BOP) system. The NSSS contains

    the reactor connected to steam generator (SG) and a primary or main pump.in addition, there is one pressurizer connected

    to the reactor in the containment building. The BOP system mainly consists of turbine and condenser. The PWR objective

    is to transfer the energy, which is produced in the reactor to the SG, where it is converted into steam to drive the turbine

    generator in order to produce the electrical power (see figure 2).

    Figure 2: Overview of a Nuclear Power Generation Process [18].

    In this study, dynamic, detailed, and nonlinear mathematical models for the NPP systems of the Westinghouse

    pressurized water reactor (PWR) NPP is developed.

    2.1 Modelling the NPP Nuclear Steam Supply System (NSSS)

    Following ref [19], mathematical model for reactor core, pressurizer, SG model and their control systems are simulated in

    matlab/simulink as shown in figure 3.The detailed derivations of these models are presented in [12].

    Figure 3: The Structure of the NPP Nuclear Steam Supply System Simulink Model.

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    2.2 Modelling the NPP Balance of Plant (BOP) System

    The model development of BOP components of a PWR plant describes models for turbine, speed control system, and

    condenser. These models then connected to construct the BOP overall model of NPP.

    Description of steam and water flow path in steam turbine system is as following:-

    A saturated steam is supplied from the SG to the steam turbine. A portion of this saturated steam enters the

    turbine and the remainder bypassed to the reheater to improve the turbine thermal efficiency.

    After leaving the nozzle chest the steam expands in high pressure turbine (HPT).

    A portion of the steam is extracted to the HP feed water heater (Heater 2). The remainder of the steam enters

    the moisture separator that used to remove the water from steam.

    The removed water feds to Heater 2.

    The remaining steam is superheated in the steam reheater. And then, it enters the low pressure turbine (LPT).

    A portion of this steam is extracted to the LP feed water heater (Heater 1). The remainder is expanded in the

    LPT to produce the mechanical power.

    Figure 4: Representation for the Steam Turbine Flow Diagram.

    2.2.1 Turbine Model

    It includes models for the nozzle chest, HPT, reheater, moisture separator, LPT, and heater 1, 2.

    Turbine M ode l Governing Equat i ons

    (1)

    Noz zl e Che st Equati on

    (2)

    (3)

    (4)

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    (5)

    High Pressure Turbine (HPT) Equations

    (6)

    (7)

    (8)

    Moisture S eparator Equations

    (9)

    (10)

    Where

    Reheater Equations

    (11)

    (12)

    (13)

    (14)

  • 938 Asmaa M. Elsotohy, Mohamed A. Mehanna, Ayman A. Eisa & Ahmed S. Adail

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    (15)

    (16)

    Where

    (

    Low Pressure Turbine(LPT) Equations

    (17)

    (18)

    Feed Water Heater (1) Equations

    (19)

    (20)

    Feed Water Heater (2) Equation

    (21)

    (22)

    (23)

    (24)

    Output Power Equations

    (25)

    (26)

    (27)

    (28)

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    (29)

    (30)

    2.2.2 The Condenser

    The condenser is a large surface type heat exchanger. It is equipped with vacuum system, which maintains a constant

    pressure in the condenser for steady-state and transient and conditions, and the hot well pumps with their control systems

    to control the water level in the hot wells.

    Main condenser equations:-

    (31)

    (32)

    (33)

    (34)

    (35)

    (36)

    Where,

    Main steam valve coefficient

    Bypassed steam valve coefficient

    Heat conversion factor (5.404)

    Constant parameter1 of steam pressure equation (1.27453).

    Constant parameter2 of steam pressure equation (1068.8)

    Constant parameter of output power equation (1.414)

    Fraction of steam extracted from H.P to HPFH (0.1634)

    Fraction of steam extracted from L.P. to LPFH (0.2174)

    Enthalpy of steam leaving low pressure turbine.

    Enthalpy of steam leaving nozzle chest.

    Enthalpy of steam at reheater.

    Enthalpy of water in high pressure feed water heater (

    HPFH ) (280.4)

    Enthalpy of water i n low pressure feed water heater

    (LPFH) (529.15).

    HPFH Heat flow Constant parameter (475).

    LPFH Heat flow Constant parameter (863.76)

  • 940 Asmaa M. Elsotohy, Mohamed A. Mehanna, Ayman A. Eisa & Ahmed S. Adail

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    Reheater Heat flow Constant parameter (22.589)

    Steam Enthalpy which leaving LPT.

    Steam Enthalpy which leaving nozzle chest (1196.1)

    Steam Enthalpy at reheater (1269.7)

    Steam Enthalpy at isentropic end point from pressure Pc.

    Steam Enthalpy at isentropic end point from pressure Pr.

    Saturated water Enthalpy in reheater.

    Saturated water Enthalpy in condenser.

    Latent water Enthalpy in reheater.

    Latent water Enthalpy in condenser.

    Nozzle chest Pressure (790).

    Reheater Pressure (160).

    Steam pressure in steam generator

    Output turbine power

    Heat transfer rate in reheater (216931).

    Nozzle chest Volume (200)

    Reheater Volume (20000)

    Flow rate of Steam passing through the main steam valve (3959.5).

    Flow rate of Steam leaving nozzle chest (3959.5).

    Flow rate of Steam leaving HPT (3311.56).

    Flow rate of Steam leaving moisture separator (2942.9).

    Flow rate of Steam leaving reheater (2942.9).

    Flow rate of Steam leaving LPT (2303).

    Flow rate of water from HPFH to LPFH.

    Flow rate Steam bypassed to reheater (186.36).

    Flow rate of Water from reheater to HPFH (186.336).

    bled steam from HPT to HPFH

    bled steam from HPT to LPFH .

    Water droplet rate into the condenser hot wells.

    Flow rate of Water condensation.

    Flow rate of Steam in condenser.

    Outlet flow rate from condenser to LPFH.

    Steam Density at nozzle chest (1.7337).

    Steam Density at reheater (0.4).

    Time constant associated with main condenser .

    Time constant related with HPFH .

    Time constant associated with LPFH .

    Time constant related with HPT .

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    Time constant related with LPT .

    Time constant related with reheater .

    Time constant related with main condenser

    2.2.3 Turbine Speed Control System

    Figure (5) shows a block diagram of a steam turbine speed control system. Initially, according to the electrical generator

    design frequency, the speed of the steam turbine is set at a reference value. In case of turbine speed deviation from its set

    point, the speed sensor provides a signal to the comparator device. The Speed error signal (difference between actual speed

    signals and the speed set point initiates the hydraulic system to an action according to the difference. The hydraulic system

    provides the required power for accurate positioning and rapid movement of the steam valve system. Any changes in the

    steam valve position will be proportional to the turbine output torque, which ultimately regulates the speed.

    Figure 5: Steam Turbine Speed Control System Representation.

    (37)

    (38)

    Where,

    The equation Conversion factor

    Turbine-generator moment of inertia

    Power demand

    Torque demand

    AS shown in figure 6 with connecting the turbine model with both condenser model and speed control system, the

    NPP balance of plant system will be provided.

  • 942 Asmaa M. Elsotohy, Mohamed A. Mehanna, Ayman A. Eisa & Ahmed S. Adail

    Impact Factor (JCC): 8.8746 SCOPUS Indexed Journal NAAS Rating: 3.11

    Figure 6: The Structure of the NPP Balance of Plant System Simulink Model.

    3. SIMULATION RESULTS OF INTERACTION BETWEEN ELECTRICAL GRID AND NPP

    There are many technical issues related with the electrical grid NPP interface among these issues is the sudden load

    rejection to NPP and the tripping of NPP [20, 21].The whole NPP Simulink model is shown in figure 7.

    Figure 7: The NPP Simulink Model Structure.

    3.1 Effect of Electrical Grid on NPP

    Abnormalities in electrical grid lead to transients in NPP. The effect depend on the severity of these Abnormalities, may

    lead to NPP islanding or even to reactor tripping. Such Abnormalities adversely effect on the life and performance of the

    plant [7].

    Supposing the nuclear power plant is the generation on bus (1) of IEEE 30 bus system (see figure 8).

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    Figure 8: IEEE 30 Bus System Single Line Diagram.

    3.1.1 A Step Increase in Power Demand

    As shown in figure 9, assuming that a step increase in power demand by 15% at the time=500 sec occurs. At the beginning

    of the load step increase, an imbalance between the turbine mechanical torque and the generator electromagnetic torque

    occurs and this leads to the decrease in speed of the turbine firstly. Then, according to the speed error signal the main

    steam governor valve will increase the steam flowrate according to demand power. Finally, the turbine mechanical power

    and output electrical power will match the connected load, and speed of the turbine will be returned to its set point value.

    Also, it is shown that there is permissible decrease in the buses voltage of electrical grid.

    (b)

    (a)

  • 944 Asmaa M. Elsotohy, Mohamed A. Mehanna, Ayman A. Eisa & Ahmed S. Adail

    Impact Factor (JCC): 8.8746 SCOPUS Indexed Journal NAAS Rating: 3.11

    (d)

    (c)

    (f)

    (e)

    Figure 9: Dynamic Responses of the Nuclear Plant During a Step Increase in Demand Power.

    (a) Turbine Speed (b) Steam Valve Coefficient, (c) Steam Generator Pressure

    (d) Output Turbine Power (e) Electrical Power (f) Voltage Profile of IEEE-30 Bus System.

    3.1.2 A Step Decrease in Power Demand

    As shown in figure (10), assuming that a step decrease in power demand by 15% at the time=500 sec occurs. When the

    load request sharply decreases, turbine power deviates from its set value. As the governor responses, the control valves

    (CVs) close partly to reduce the flow rate of steam. So that there is a decreasing in flow of steam through the turbine, while

    the steam temperature and pressure in the SG increase. Thus, the exchange of heat between the primary and the secondary

    sides of SG decreases, and the temperature of coolant increases. Then, power of the turbine decreases to provide the

    required power demand. Also, the electrical grid voltage will increase responding to the decrease in the load.

    (b)

    (a)

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    (d)

    (c)

    (f)

    (e)

    Figure 10: Dynamic Responses of the Nuclear Plant During a Step Decrease in Demand Power

    (a) Turbine Speed (b) Steam Valve Coefficient, (c) Steam Generator Pressure,

    (d) Output Turbine Power, (e) Electrical Power, (f) Voltage Profile of IEEE-30 Bus System.

    3.2 Effect of NPP ON Electrical Grid

    Due to the large size of NPP, during operating, it plays an effective role in stabilizing the electrical grid. In a situation of

    NPP tripping, an imbalance between the required load and the available generation happens. Without an additional

    generation, power can be quickly imported through external connections of grid or adding generation quickly, this may

    lead to degrading in voltage on the alternate connections of offsite power that may result in loss of offsite power to the

    NPP.

    The proposed NPP model is implemented on IEEE 30-Bus system to evaluate the effectiveness of NPP model in

    this study. An IEEE 30-bus system Single line diagram is showed in figure (8). Data of buses, regulated bus data, data of

    lines, capacitors and transformer data for this test system can be found in the standard power system test case archive [22]

    The system has 41 branches with 24 loads, 30 buses, 4 transformers, 2 generators and 4 synchronous condensers which are

    used only for supporting the reactive power.

    To show the effect of NPP abnormalities on voltage profile of IEEE 30bus system, a study for three power flow

    cases were presented on the IEEE 30-Bus system. First, the magnitudes of voltage and phase angles were found for the

    standard base case without any change on the NPP generation level.

    The other two studies were:

    Total loss of generation at bus 1 and at bus 2 (NPP shutdown)

    loss of NPP generation at bus 1 by 50%

  • 946 Asmaa M. Elsotohy, Mohamed A. Mehanna, Ayman A. Eisa & Ahmed S. Adail

    Impact Factor (JCC): 8.8746 SCOPUS Indexed Journal NAAS Rating: 3.11

    The aim was to study the voltage magnitude of IEEE 30 bus system under these different previous mentioned

    cases.

    3.2.1 Steady State Condition

    This is the standard base case without any change in generation of the system. The results obtained in case of applying

    state estimation method on the system shows that buses 26 and 30 have minimum voltages (Voltage at bus 26 equal 0.9999

    pu and Voltage at bus 30, 0.9922 pu) and those are the weakest buses on the system. Therefore, these two buses can be

    selected to implement facts on the future work.

    Table 1: Base Case Voltage and Phase Angle for IEEE 30 Bus System

    Bus No. VM (p.u) VA (deg)

    1 1.06 0

    2 1.045 -5.3782

    3 1.0212 -7.5287

    4 1.0123 -9.2794

    5 1.01 -14.1488

    6 1.0106 -11.055

    7 1.0026 -12.8523

    8 1.01 -11.7974

    9 1.0511 -14.098

    10 1.0454 -15.6882

    11 1.082 -14.098

    12 1.0573 -14.9329

    13 1.071 -14.9329

    14 1.0425 -15.8245

    15 1.0379 -15.9164

    16 1.0446 -15.5154

    17 1.0402 -15.8499

    18 1.0284 -16.5302

    19 1.0259 -16.7037

    20 1.03 -16.5072

    21 1.033 -16.1307

    22 1.0335 -16.1164

    23 1.0274 -16.3066

    24 1.0218 -16.4828

    25 1.0176 -16.0546

    26 0.9999 -16.474

    27 1.0235 -15.5301

    28 1.0071 -11.6773

    29 1.0037 -16.7593

    30 0.9922 -17.6416

    VM: Voltage magnitude

    VA: Voltage phase angle

    3.2.2 Shutdown of NPP

    In case of a sudden shutdown of NPP at bus 1 occurs (bus 1 presents 85% of the total generation of IEEE 30 bus system),

    the voltage of all buses reduced and goes out the safety limits. This NPP outage will lead to a significant generation loss

    for the grid. In this case, the grid must have reserves enough to warrant voltage stability of the system during down-times

    or shutdown of NPP.

    On the other hand, in case of considering NPP shutdown at bus 2 (bus 2 presents 15% of the IEEE 30 bus system

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    total generation), buses voltage will be reduced to a level higher than the voltage in case of assuming shut down of NPP at

    bus1. The results containing comparison of nodal voltage magnitudes with the IEEE 30 bus system standard base case

    shown in Figure 11.

    0.75

    0.8

    0.85

    0.9

    0.95

    1

    1.05

    1.1

    1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

    Bu

    s V

    olt

    age

    (pu

    )

    NO. of Bus

    Steady state operation Generation 1 shutdown Generation 2 shut down

    Figure 11: IEEE 30-Bus System Voltage Magnitude in Case of Steady

    State and Total Loss of Generation (NPP Shutdown) at Buses 1, 2.

    3.2.3 Loss of Generation by 50%

    Now, the test network was studied in case of loss of generation at bus number 1 by 50%. In this case, the voltage of all

    buses reduced as shown in figure 12, this is due to losing a high effective percentage of generation.

    0.75

    0.8

    0.85

    0.9

    0.95

    1

    1.05

    1.1

    1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

    Bu

    s V

    olt

    age

    (pu

    )

    NO. of BusSteady state operation Decrease Generation 1 by 50%

    Figure 12: IEEE 30-Bus System Voltage Magnitude in Case of Steady

    State and Loss of Generation by 50% at bus 1.

    4. CONCLUSIONS

    This paper presented a model for both NPP and test case IEEE 30 bus system through a MATLAB program, in order to

    study the mutual interface between electrical grid and NPP. A study for NPP response to step increase and decrease in

    power demand is performed and analyzed. The NPP fast response to abnormalities showed the load following ability of

    this plant, as it follows the changes in the load safely with a good response. Also, a study for the impacts of the NPP on the

    voltage profile of the power network under abnormal conditions of NPP sudden shutdown and loss of NPP generation by

  • 948 Asmaa M. Elsotohy, Mohamed A. Mehanna, Ayman A. Eisa & Ahmed S. Adail

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    50% based on the power system state estimation load flow method is presented. It is found that the sudden shutdown of

    NPP capable of decreasing the voltage profile at the almost buses of system, depending on the percentage of generation

    lost comparing with the total generation of the network. Also, the buses voltages in case of loss of generation by 50% are

    plotted, analyzed and compared with the standard base case. Hence, the objective of this current work is to present the

    unbalance that occurs in the electrical network, in case of losing a large percentage of generation.

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  • 1. INTRODUCTION2. MATHEMATICAL MODEL OF NPP2.1 Modelling the NPP Nuclear Steam Supply System (NSSS)2.2 Modelling the NPP Balance of Plant (BOP) System2.2.1 Turbine Model2.2.2 The Condenser2.2.3 Turbine Speed Control System

    3. SIMULATION RESULTS OF INTERACTION BETWEEN ELECTRICAL GRID AND NPP3.1 Effect of Electrical Grid on NPP3.1.1 A Step Increase in Power Demand3.1.2 A Step Decrease in Power Demand

    3.2 Effect of NPP ON Electrical Grid3.2.1 Steady State Condition3.2.2 Shutdown of NPP3.2.3 Loss of Generation by 50%

    4. CONCLUSIONSREFERENCES