# Power System Study for Pre-Feed of Power Factor Improvement in Electrical Power System of Qatar Gas

Power system study was carried out by IFluids Engineering, Qatar for the pre-feed of power factor improvement for electrical power system in Qatar gas RLTO facilities. Power system studies involve detailed analyses of electrical networks to ensure the reliability, safety, and optimal performance of power distribution to critical equipment and facilities. To learn on What is Power System Studies? Click Here

The LNG S&L, Non-LNG S&L and Common Sulphur Plant (CSP) area within Ras Laffan Terminal Operation (RLTO) facilities are powered by KAHRAMAA, the National Grid.

According to the KAHRAMAA regulation, the substations shall have load power factor within the range of 0.9 lagging to 0.95 leading. A lagging power factor of less than 0.9 shall be improved by installing the additional reactive power compensation system.

The objectives are as follows:

• To simulate the Electrical System to determine the actual condition of the Electrical System in substations.
• To determine the existing Power Factor at the Point of Common Coupling (PCC) and to provide Power Factor Correction (PFC) to the range of 0.90 lagging to 0.95 leading under various load conditions and switching configurations.
• To simulate the new Capacitor Bank ratings under various load conditions and switching configurations.

In the modeling of a substation and its electrical components, various models are used to represent different equipment and loads accurately. They are crucial components to accurately represent the behavior and interactions of the electrical system.

1. Transformer Model: The transformer model represents the electrical characteristics and behavior of the transformers present in the substation. Transformers are essential for voltage transformation and power distribution. The transformer model typically includes the following key parameters:
• Turns Ratio: Represents the ratio of the number of turns in the primary winding to the number of turns in the secondary winding, determining the voltage transformation ratio.
• Impedance: Includes the resistance and reactance of the transformer, which affects its ability to limit fault currents and regulate voltage.
• Core Losses: Modelled as hysteresis and eddy current losses, which are the losses in the transformer’s magnetic core when it operates.
• Copper Losses: Represent the losses in the transformer’s windings due to the resistance of the copper conductors carrying current.
• Magnetizing Current: The current required to establish the magnetic flux in the transformer’s core.
• Tap Changer: For on-load tap changers, the model includes different tap positions to simulate voltage regulation.
• Saturation Effects: To account for the magnetic core’s saturation at high magnetic flux levels.
• AC Network Model: The AC network model represents the entire electrical power system within and around the substation. It includes all the interconnected components, such as transformers, circuit breakers, transmission lines, loads, and generators. The AC network model captures the following elements:
• Electrical Components: Models for transformers, circuit breakers, disconnect switches, reactors, capacitors, etc.
• Transmission Lines: Models representing the impedance, capacitance, and inductance of transmission lines connecting the substation to other substations or power sources.
• Loads: Various types of loads (industrial, commercial, residential) modeled as per their active and reactive power characteristics.
• Generators: Models representing power generators or distributed energy resources connected to the substation.
• Protection and Control Systems: Models for protection relays, control systems, and automation equipment to simulate their response during fault events and other abnormal conditions.
• The AC network model allows engineers to perform various power system studies, including load flow analysis, short circuit analysis, transient stability studies, voltage regulation studies, and harmonics analysis. These studies help ensure the proper operation, stability, and reliability of the substation and the connected power grid.
• Cable Model: The cable model is used to represent the behavior of electrical cables connecting different components within the substation or the distribution network. Cables have resistance, inductance, and capacitance, which introduce voltage drop and phase shift in the system. Cable models can be represented using distributed parameter models (transmission line models) or lumped parameter models (PI or T models). These models help in analyzing power losses, transient effects, and voltage drops along the cable length.
• Motor Load Model: Motor loads are a common type of dynamic loads in a substation, especially in industrial settings. Modeling motor loads is essential for studying the impact of motor starting and motor load characteristics on the power system. Motor loads have a significant inrush current during startup and may exhibit different behavior under various operating conditions. The motor load model represents these characteristics using equivalent parameters like the motor’s starting current, slip, and efficiency.
• Lumped Load Model: A lumped load model is used to represent electrical loads that do not require a detailed representation but can be modeled as an equivalent single component. For instance, lighting loads, heating loads, and small appliances can be represented as a lumped load with their active and reactive power ratings. This simplifies the analysis while still capturing the overall impact of these loads on the system.
• Capacitor Bank Model: Capacitor banks are used for reactive power compensation and improving power factor in substations. Modeling capacitor banks involves representing the capacitors and their associated switching equipment. Capacitor bank models consider the bank’s reactive power ratings, control scheme (fixed or switched), and response time during switching operations. Proper modeling of capacitor banks is crucial to ensure effective voltage regulation and power factor correction in the substation.

In modern power system analysis software, engineers can create and incorporate these models to simulate the behavior of the substation and the entire power network accurately. These models help in performing various studies such as load flow analysis, fault studies, voltage regulation analysis, and dynamic simulations to ensure the substation’s reliability and stability. Additionally, model validation using actual field measurements is important to ensure the accuracy of the simulation results.

Load flow simulation analysis, also known as power flow analysis, is a fundamental and critical study conducted in power systems engineering to analyze the steady-state behavior of an electrical network. The primary goal of load flow analysis is to determine the voltage magnitude and phase angle at each bus (node) in the power system, along with the power flows through transmission lines, transformers, and other components. This analysis helps ensure that the power system operates within its normal operating limits and maintains acceptable voltage levels under various load conditions.

## Here’s how Load flow simulation analysis works:

• Power System Representation: The power system is represented as a network model consisting of buses (nodes) interconnected by transmission lines and other electrical components. Each bus is characterized by its voltage magnitude, phase angle, and load information.
• Formulation of Power Flow Equations: Load flow analysis is based on solving a set of nonlinear algebraic equations that describe the power flow within the network. These equations represent the balance between active power (real power) and reactive power at each bus, considering power injections from generators and power demand from loads.
• Load Flow Solution: The power flow equations are solved iteratively using numerical methods, such as the Newton-Raphson method or the Gauss-Seidel method. The solution process continues until the convergence criteria are met, indicating that the voltage magnitudes and phase angles have stabilized.
• Voltage and Power Analysis: After convergence, the load flow analysis provides the voltage magnitudes and phase angles at each bus, as well as the active and reactive power flows through transmission lines, transformers, and other components. These results indicate the steady-state operating condition of the power system.
• Validation and Analysis: Engineers analyze the load flow results to ensure that the power system is operating within acceptable limits. They check for voltage violations (overvoltages or undervoltages), overloading of equipment, and reactive power balance. If any issues are identified, corrective measures can be taken, such as adjusting generator setpoints, installing shunt capacitors or reactors, or reconfiguring the network.

Load flow simulation analysis is an essential tool for power system planning, design, and operation. It helps engineers ensure the reliability, stability, and efficiency of the power system by identifying potential problems and optimizing its performance. Advanced power system analysis software is used to perform load flow simulations due to their computational efficiency and accuracy.