Maintain or refurb?: Generator excitation systems choices in the modern day
Author : Douglas Cope, Excitation Engineering Services
01 November 2024
With the average age of power stations in the UK approaching 45 years old, there is an increasing need for stations to modernise. Maintaining and refurbishing generator excitation systems in power plants is critical for reliability and availability.
Here, Douglas Cope, Director at excitation control specialist Excitation Engineering Services Ltd, explores the use of proactive maintenance and refurbishment strategies, and how plant operators can navigate this decision.
Maintenance and refurbishment are two different approaches for ensuring that generator excitation systems remain operational. Maintenance focuses on preserving the system’s current state by addressing wear and tear through routine inspections, minor repairs and the replacement of consumables like brushes and capacitors. It ensures that the system runs smoothly without necessarily enhancing its performance or lifespan.
Refurbishment, on the other hand, is a more comprehensive strategy. It focuses on the replacement or upgrade of key components to restore the system’s functionality and improve its reliability. While maintenance is about sustaining day-to-day operations, refurbishment targets medium- to long-term reliability by addressing age-related issues and enhancing system efficiency with modern technology.
Comparing strategies
A brushless static exciter illustrates the contrast between strategies. Refurbishment costing upwards of £1,000,000 with a 4- to 8-year payback period, and focuses on targeted upgrades like digital controls and solid-state devices. These upgrades replace older mechanical systems for improved voltage regulation and reliability.
However, older components like electrolytic capacitors and motorised potentiometers may require ongoing maintenance. Integrating new technologies requires compatibility checks and software updates to support the new functionalities. While extending operational life, refurbishment of excitation systems may not achieve the comprehensive reliability of a complete refurbishment.
By comparison, the complete replacement of the excitation control system typically includes supply of new excitation front end, programmable logic controller (PLC), thyristor bridges and other critical components. This approach not only restores the system to optimal conditions but also addresses potential issues, ensuring it continues to operate effectively and meets current standards.
Despite the higher costs – potentially 65 percent more than refurbishment – and extended downtime of days to weeks, replacement ensures the excitation control system maintains peak performance and long-term reliability. This makes it more suitable for systems requiring extensive upgrades.
Considerations for plant operators
Power stations nearing the end of their operational life face unique challenges. For those with only a few years remaining, the focus is often on increased maintenance and refurbishment to ensure short-term reliability.
EES, for example, specialises in both maintenance and refurbishment of excitation systems, offering tailored solutions based on the operational context and age of synchronous machines, whether motors or generators. This allows the company to recommend the most cost-effective strategy that aligns with the plant’s immediate needs and long-term sustainability goals.
Conversely, stations with a longer expected lifespan might invest in replacement to benefit from modern technology and improved performance. Balancing the options is crucial. EES provides comprehensive evaluations to ensure continued operational efficiency and reliability throughout the plant’s lifecycle, regardless of the maintenance strategy.
Grid code compliance is also a critical consideration. Refurbishment typically adheres to the existing grid code rules established at the time of original installation, making it a less complex and more cost-effective option. In contrast, replacement often requires compliance with updated standards, adding complexity and expense due to the necessary studies and demonstrations.
These regulatory requirements will impact the decision-making process, as ensuring compliance with new standards may involve additional planning and resources. Understanding the implications of grid code compliance is essential for power plant operators when choosing between maintaining and refurbishing.
The decision between refurbishing and replacement of excitation systems demands careful consideration. Tailored solutions are essential for power plant upgrades to ensure reliability and operational availability.
To talk to an expert on whether maintaining or refurbishing is best for your excitation system, or to see about bespoke electrical excitation panels specific to your needs, visit excitationengineering.co.uk.
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