Essential Components of Excitation Systems
Excitation power systems play a vital role in power generation by keeping generators functioning at optimum levels. Some key components that make up excitation power systems include:
Rotating Exciter: This component generates alternating current (AC) power to energize the generator’s field windings. Rotating exciters come powered by the generator shaft. Different design variants include brushless excitation power systems or static excitation power systems.
Rectifier: The rectifier converts the AC power from the rotating exciter to direct current (DC) power required to energize the generator’s field windings. Earlier systems used mercury-arc valves or thyristor valves as rectifiers. Modern excitation power systems employ silicon controlled rectifiers (SCRs) or diodes in bridge rectifier configurations.
Regulator: The regulator controls the output voltage of the Excitation Systems by regulating the field current supplied to the generator. Earlier analog designs used rotating amplidynes as regulators. Digital static excitation power systems now incorporate microprocessor-based regulators with firing circuits to control SCR valves.
Sensing and Feedback: Various sensors measure generator output parameters like voltage, current, power factor, etc. and feed this valuable feedback to the regulator. This closed-loop control ensures generator output remains stable under all load variations. Potential and current transformers are commonly used for sensing.
Modes of Operation and Control Strategies
Excitation systems operate in various modes depending on generator operational needs:
No-Load Excitation: At no external load, the minimum field current required to maintain rated voltage is supplied. This establishes the steady-state operating point.
Build-Up: When the generator is started from standstill, the field is progressively strengthened in controlled steps to build voltage up to rated levels before taking load. This avoids transients on switch-on.
Voltage Regulation: Under changing load conditions, the regulator acts to keep output voltage constant by adjusting the field current in linear or quadratic response modes via thyristor firing angles.
Stabilization: Large disturbances are counteracted by providing additional field current momentarily until normal voltage control resumes. Strict operating bandwidth and response times are crucial for grid stability.
Demagnetization: When the generator is shut down, the field current is gradually reduced to avoid sudden release of residual magnetism, reducing mechanical transients.
Trends in Modern Excitation System Technologies
Advancements are continually being made to improve excitation power system performance and reliability:
Brushless Systems: Brush wearing issues led to the development of brushless systems employing rotating diodes or static elements like an AC exciter stator. Less maintenance needs.
Static Excitation: Entirely static schemes replace mechanical components with power electronic converters, providing faster, digital control and elimination of rotating parts for improved life. IGBTs are commonly used.
Digital Control: Microprocessors have replaced analog designs, offering programmable control strategies, self-diagnostics, communication capabilities and parameter adjustments without hardware changes.
Flexible AC Transmission Systems (FACTS): Emerging technologies like thyristor-controlled series capacitors (TCSC) and static VAR compensators (SVC) assist excitation power systems in maintaining high power transfer capacity of transmission networks.
Renewable Integration: With increasing penetration of weather-dependent renewable energy sources, advanced control strategies help maintain grid stability in tandem with energy storage systems.
Thus modern excitation power systems ensure reliable power generation through robust designs and digital controls optimized for smart grid requirements. Their evolution also reflects the drive for reduced downtime and lifecycle cost optimization in power plants.
Interaction with other Systems to Ensure Stable Power Flows
Optimal coordination between the excitation power system and other plant equipment components is necessary for dependable power delivery:
Turbine Control: The regulator coordinates with the turbine speed governor to prevent hunting between electrical and mechanical power outputs during load swings.
Power System Stabilizer: Additional damping is provided through supplementary signals from the PSS to counter low frequency oscillations across the network during disturbances.
Automatic Voltage Regulator: The AVR maintains scheduled voltage by controlling the generator terminal voltage based on a voltage reference signal received from the control center.
Reactive Power Compensation: Capacitors, reactors and SVC/STATCOM devices coordinated with the exciter control the generator terminal voltage and bus voltage for managing reactive power flows.
Synchronizing Systems: Phase-matching data from synchronizers enables switching the generator onto the grid in precise synchronism to prevent tripping due to phase angle errors.
Thus robust communications and coordinated controls between the excitation power system, other plant auxiliaries and the grid operator facilitate secure power transfers even during contingencies. This ensures power systems run optimally and reliably.
Maintenance Considerations for Maximizing Equipment Uptime
Scheduled maintenance is vital for excitation systems to sustain rated performance over their design lives:
Inspections: Regular visual checks detect deterioration or damage to components like sliprings, rectifiers, circuit boards early to avoid failures. Thermography aids.
Testing: Periodic functional testing of individual loops like voltage regulation validates operation. End-to-end commissioning tests regulation throughout load ranges.
Calibration: Drifts in sensors/references require re-setting measurement thresholds and setpoints to design accuracy levels using calibration equipment.
Overhaul: Major attendances replace worn components, perform protective relay setting reviews and upgrade software/hardware afterousands of operating hours.
Spares: Adequate inventory of frequently replaced items like rectifier discs, fuses and spare parts prevents downtime due to non-availability.
Proactive practices like condition monitoring, vibration analysis, oil testing and infrared scanning also help maintenance planning by predicting defects in advance. This keeps exciters running cost-effectively with high availability similar to other substation equipment.
Excitation systems play a pivotal role in electric power generation by maintaining synchronous machines at their operating points. Their evolution from electromechanical to static electronic designs has vastly improved generator regulation and grid support capabilities. Optimized maintenance further enhances their reliability for delivering clean, affordable and uninterrupted power supplies.
Discover the Report for More Insights, Tailored to Your Language.
French German Italian Russian Japanese Chinese Korean Portuguese
*Note:
1. Source: Coherent Market Insights, Public sources, Desk research
2. We have leveraged AI tools to mine information and compile it
About Author - Ravina Pandya
Ravina Pandya, a content writer, has a strong foothold in the market research industry. She specializes in writing well-researched articles from different industries, including food and beverages, information and technology, healthcare, chemicals and materials, etc. With an MBA in E-commerce, she has expertise in SEO-optimized content that resonates with industry professionals. LinkedIn Profile