Elements of Power System Network and its Operation and Economic Analysis and Operation and Operations and Economic Operation of Power Systems

Overview and Goals of Power System Analysis

• Goal of the Course: To provide a comprehensive overview of interconnected power system operations, utilizing modern methods for analysis and design.

• Thinking Process Development: The curriculum is structured to develop students' analytical thinking, ensuring a sound understanding of electronic power system engineering and motivating interest in the industry.

• Basic Tools: Equips students with fundamental tools for analyzing power systems during both normal and emergency conditions.

• Learning Objectives:

  • Describe the scope and nature of power system courses.

  • Explain the functional roles of a Power System.

  • Identify and understand various power system elements.

  • Describe components and their complex interactions.

  • Comprehend the economic operation of power systems.

The Core Structure of a Power System

• Interconnected Network: The modern power system is the largest and most complex man-made system, subdivided into four major parts:

  1. Generation System: The production of electricity.

  2. Transmission System: Moving bulk power over long distances.

  3. Distribution System: Final delivery to individual consumers.

  4. Loads/Consumers: The end utilization points.

• Operational Goals:

  • Achieving the highest possible reliability standards.

  • Maintaining low operational costs.

  • Ensuring minimum environmental impacts.

• The Journey of Electricity: Electricity is generated at high voltages for efficiency, stepped up via transformers at substations for long-distance transport, and stepped down for safe residential and business use.

The Generation System

• Primary Energy Conversion: Generation involves converting primary energy (coal, natural gas, wind, etc.) into electrical power at power stations or generating units.

• The Generator Mechanism: Work is performed by moving a magnet near a wire to create a flow of electrons (current). This is achieved by rotating a turbine attached to the generator shaft.

• Geographic Dispersion: Generating plants are dispersed geographically and may house multiple units.

• Regulatory Environment (Philippines):

  • Power generation is not a public utility; no congressional franchise is needed.

  • The Energy Regulatory Commission (ERC) regulates the sector, issuing Certificates of Compliance.

  • Adheres to the Electric Power Industry Reform Act of 2001 (EPIRA).

• Types of Generating Plants:

  • Conventional: Uses magnetism and mechanical action from non-renewable sources (Fossil fuels, Nuclear, large Hydro).

  • Non-Conventional: Primarily renewable energy sources (Solar, Wind, Biomass).

Energy Sources and Functional Mechanisms

• Fossil-Based Sources:

  • Coal: Black/brown carbonized rock burned in a furnace to heat a boiler; the resulting steam spins turbines.

  • Natural Gas: Flammable gas. Burned to produce steam or used directly in gas turbines.

  • Nuclear: Uses uranium atoms; thermal energy from nuclear fission creates steam to drive generators.

• Renewable and Alternative Sources:

  • Hydroelectric: Uses falling water forced through a narrow passage to spin turbines. Classified as conventional but renewable.

  • Wind: Blades capture wind energy to rotate a generator shaft.

  • Solar: Panels contain crystals that produce electrical current when struck by sunlight.

  • Biomass: Organic materials (wood, crops, waste) burned for heat and electricity.

  • Captured Methane: Gas collected from decomposing landfill trash is burned for fuel.

• Conventional vs. Non-Conventional Comparison:

  • Conventional (Non-renewable): Limited quantity, reliable, but creates pollution. Examples: Coal, natural gas, petroleum.

  • Non-Conventional (Renewable): Unlimited, clean, but produces unpredictable time-varying power. Examples: Solar, wind, tidal.

Operational Classifications of Power Plants

• Baseload Power Plants:

  • Function: Meets consistent daily demand.

  • Characteristics: Continuous operation, low cost, run year-round except for maintenance.

  • Capacity Factor: $\text{67\%}$ and above.

  • Examples: Coal, Biomass, Geothermal (e.g., $2 \times 647\,MW$ Team Energy Sual Coal-Fired Plant).

• Intermediate / Mid-merit Load Power Plants:

  • Function: Bridges the gap between baseload and peaking.

  • Characteristics: Efficient operation, higher construction cost than peaking plants but lower operational costs.

  • Capacity Factor: $23\text{-}67\%$.

  • Examples: Natural Gas (e.g., $2 \times 600\,MW$ KEILCO Ilijan plant, Batangas).

• Peaking Power Plants:

  • Function: Operates during peak demand periods.

  • Characteristics: Highly responsive to demand changes; expensive fuel (diesel/bunker oil).

  • Capacity Factor: Below $23\%$.

  • Examples: Dam-type Hydro and Oil-based plants (e.g., $242\,MW$ TMI Power Barges).

Key Capacity Terminologies

• Installed Capacity: The total manufacturer-rated capacity (nameplate capacity) that the equipment can possibly produce.

• Dependable Capacity: The reliable load-carrying ability of a plant for medium-term (MT) and long-term (LT) planning.

• Available Capacity: The current hourly or daily ability to produce electricity, used for short-term (ST) planning.

Transmission System (The Grid)

• Purpose: Interconnects generating stations with load centers; acts as the "interstate highway" of electricity.

• Bulk Movement: Moves large amounts of power over long distances at high voltage (usually $\geq 100\,kV$).

• Philippine Transmission Sector:

  • Managed by: NGCP (National Grid Corporation of the Philippines).

  • Three Grids: Luzon, Visayas, Mindanao.

  • Voltage Levels (Luzon): $500, 230, 138, 115, \text{ and } 69\,kV$.

  • Voltage Levels (Visayas): $230, 138, \text{ and } 69\,kV$.

  • Voltage Levels (Mindanao): $138, \text{ and } 69\,kV$.

• AC vs. DC Transmission:

  • AC transmission: Uses 3 conductors; distance models include Short, Medium (Pi and T models), and Long.

  • DC transmission: Uses 2 conductors for long-distance power transfer.

Distribution System and Configurations

• Final Delivery Stage: Carries power from transmission substations to individual consumers. Includes primary distribution (medium voltage) and secondary distribution (utilization voltage).

• Primary Distribution Systems:

  • Radial System: Simplest; feeders radiate from a single source. A fault results in a total loss of supply downstream.

  • Loop System: Provides two-way feed; if one side fails, the other carries the load. Can be "Normally Open" or "Normally Closed."

  • Primary Network System: Interconnected mesh/grid. High reliability but rarely implemented due to cost.

• Secondary Distribution Systems:

  • Individual Transformer: For isolated consumers far apart.

  • Common Secondary Main: Most common; utilizes diversity between consumer loads.

  • Banked Secondaries: Single-feeder low-voltage grid; transformers are connected to the same secondary main.

  • Secondary Networks: Highest reliability; mains are fed from two or more primary feeders.

• Overhead vs. Underground Distribution:

  • Safety: Underground is safer; overhead poses hazard risks.

  • Cost: Underground is $5\text{-}10\times$ more expensive due to trenching and conduit costs.

  • Flexibility: Overhead is easier to expand; underground is permanent.

  • Life Span: Overhead is approx. $25$ years; underground is over $50$ years.

Types of Electrical Systems and Voltage Classes

• DC System: 2-wire (unipolar) or 3-wire (bipolar). Mostly legacy or specialty use.

• AC Single-Phase: 2-wire (one constant voltage) or 3-wire (combination of two 2-wire systems with a neutral).

• AC Two-Phase: 4-wire (two 1-phase systems 90 degrees out of phase), 3-wire (common neutral), or 5-wire.

• AC Three-Phase: Most common.

  • Four-wire: Three 1-phase systems with a common neutral.

  • Three-wire (Wye/Delta): Used when loads are balanced (no neutral current).

• Voltage Classes (ANSI C84.1-2016):

  • Low Voltage (LV): $\leq 1000\,V$ .

  • Medium Voltage (MV): > 1000\,V \text{ to } < 100\,kV.

  • High Voltage (HV): $100\,kV \text{ to } 230\,kV$.

  • Extra-High Voltage (EHV): > 230\,kV \text{ to } < 1000\,kV.

  • Ultra-High Voltage (UHV): $\geq 1000\,kV$.

Components of a Power System

• Single Line Diagram: Representation using standard symbols and straight lines for transmission.

• Power Transformers: Trades voltage for current; steps up voltage at generation sites and down for distribution.

• Instrument Transformers:

  • Current Transformers (CT): Scales high currents (thousands of Amperes) down for meters and protective relays.

  • Potential Transformers (PT): Scales high voltages down for safe measurement and relaying.

• Switchgear:

  • Circuit Breaker (CB): Opens/closes circuits under normal or fault conditions (e.g., Oil, Air-blast, Vacuum, SF6 types).

  • Isolators: Switches operated only under no load to isolate parts for maintenance.

• Bus-bar: Copper or aluminum conductors with low impedance used to connect multiple lines at the same voltage level.

Economic Operation and Load Management

• Operational Economics: Focuses on maximum efficiency to minimize costs. Divided into:

  • Economic Dispatch: Minimum cost of power production.

  • Loss Minimization: Minimum-loss delivery to loads.

• Load Curves: Graphs showing variation of load (MW) over time (hours). Allows identification of Peak demand.

• Mathematical Definitions:

  1. Connected Load: Sum of all connected equipment (ON or OFF).

  2. Average Load: $\text{Average Load} = \frac{\text{Total Energy Generated (kWh)}}{\text{Time Period (hours)}}$

  3. Maximum Demand: The peak load occurring within a specific window.

  4. Demand Factor: $\text{Demand Factor} = \frac{\text{Maximum Demand}}{\text{Connected Load}}$ (Always < 1).

  5. Load Factor: $\text{Load Factor} = \frac{\text{Average Load}}{\text{Maximum Demand}}$ (Should be as high as possible).

  6. Diversity Factor: $\text{Diversity Factor} = \frac{\sum \text{Individual Max Demands}}{\text{Maximum Demand of Power Station}}$ (Always > 1).

  7. Capacity Factor: $\text{Capacity Factor} = \frac{\text{Actual Energy Produced}}{\text{Maximum Possible Energy}}$.

  8. Utilization Factor: $\text{Ratio of Max Demand to Installed Capacity}$.

• Reserve Capacity: $\text{Reserve Capacity} = \text{Plant Capacity} - \text{Max Demand}$.

  • Spinning Reserve: Available instantaneously.

  • Hot Standby: Available in approx. $30$ minutes.

• Demand Side Management (DSM): Encouraging consumers to shift demand to off-peak hours (night/weekends) through smart metering or tariff incentives.

System Stability and Terminology

• Brownout: Reduced voltage causing flickering or potential appliance damage.

• Power Interruption: Loss of power in a specific area (scheduled or unscheduled).

• Blackout: Total or partial grid collapse.

• Optimization: Requires long-term and short-term load forecasts, using tools like Automatic Voltage Regulators (AVR) for Variable and Q control and Turbine Governors for P and f control.

Numerical Examples

• Problem 1: A plant with Max Demand = $60\,MW$, Load Factor = $0.75$, Capacity Factor = $0.6$, and Use Factor = $0.65$.

  • Annual Energy = $60 \times 10^3 \times 0.75 \times 8760 = 394.2 \times 10^6\,kWh$.

  • Plant Capacity = $\frac{\text{Average Load}}{\text{Capacity Factor}} = \frac{45}{0.6} = 75\,MW$.

  • Reserve Capacity = $75 - 60 = 15\,MW$.

• Problem 2: Connected Load = $40\,MW$, Max Demand = $20\,MW$, Yearly Energy = $73.6 \times 10^6\,kWh$.

  • Demand Factor = $\frac{20}{40} = 0.5$.

  • Average Load = $\frac{73.6 \times 10^6}{8760} \approx 8401\,kW$.

  • Load Factor = $\frac{8401}{20000} = 0.42$ or $42\%$.