– By K. Steiner-Dicks –
“The bus duct system, partially due to its inert status, has often been overlooked. People see big pipes in the air and think ‘what could go wrong with that,’ failing to understand the function and purpose of the bus duct apparatus,” says Jessica D. Netter Ducharme, EBI VP Sales and Marketing.
Q: Recently Electrical Builders, Inc. (EBI) and Doble Engineering teamed up to offer bus duct testing to power plants while the plant is in service. How was this made possible and is this service offering the first of its kind for the nuclear power sector?
A: EMI Diagnostics has been offered and proven to be an invaluable resource to determine power plant component health for many decades. This type of testing has been proven with over 8,000 successful field tests on more than 500 different designs with 70 types of defects and conditions identified, catalogued and verified.
However, this service has historically focused on the mechanical apparatus at the plants. The bus duct system, partially due to its inert status, has often been overlooked. People see “big pipes in the air” and think “what could go wrong with that,” failing to understand the function and purpose of the bus duct apparatus. Despite the proven and successful history of this type of testing technology, this is the first time that it has been applied specifically to focus on the health of bus duct systems.
Q: Could you explain what electromagnetic interference is and what it could identify?
A: Electromagnetic interference is the precise frequency domain measurement and identification of radio frequency energy that results from electrical partial discharge and arcing at defects. EMI data is collected from the temporary placement of a single split core radio frequency current transformer (RFCT) around the power conduit, safety ground or neutral lead of the component being tested. The acquired radio frequency spectrum, or EMI signature, is unique for each physical location of the defect present within the electrical system.
Q: What are the benefits of EMI diagnostics?
A: EMI diagnostics can identify compromised IPB before an outage; provide broader view of system defects including partial discharge; enable limited maintenance budgets to be targeted toward critical/problematic units; empower improved condition assessment and optimized preventative maintenance programs; plus it can allow you to look back at the generator and forward to the transformer.
Q: What specifically could EMI Diagnostics identify?
It could identify loose or broken support insulators; loose or corroded hardware; defective insulation; stray circulating currents; foreign material or objects inside the bus.
Other cases that we have found include defective bus PT connections; open PT high-voltage fuses; contaminated insulators (dirt, dust, water); and loose or compromised braid, laminate and shunt connections.
Q: What are the potential cost savings of being able to keep the plant online while you handle your bus duct testing checks?
A: It is important to understand that this type of online testing does not replace traditional testing and inspection methods. What it does is give you though is insight into where to focus your inspection, cleaning and repair efforts when you do go offline.
The benefit of combining the online/offline approach is that you are not going into your outage blind. You know if you have bus duct issues to address before you get into the outage, allowing for more efficient and cost effective outage planning.
Furthermore, if you are planning to swap out a transformer, how do you know that the bus duct system you plan to connect it to is free of issues and is functioning properly? Do you want to risk hooking your new multi-million dollar transformer up to defective bus duct, putting both at risk for failure?
Q: Since the NRC has boosted safety measures for the industry in recent months, has this had any impact on your business/sales revenue?
A: Yes, we have seen a dramatic increase in our inspection and maintenance division, particularly for our internal bus duct video inspection and cleaning services as plants become more aware of the benefits these services provide in both repair costs and increased safety.
Q: Since Nuclear Energy Insider last spoke to EBI, has the O&M side of your industry seen a greater understanding of your product and the benefits it can bring to a plant; proactive measures that can maintain plant safety and operations?
A: Yes, however, this education is not something that happens overnight. It takes time and even once plant operators fully understand the benefits, it requires a shift in operations to allow for proactive vs. reactive budget planning.
Q: What is the general condition of the older generation bus ducts in the US–still robust or do they need updating? Could you give us some examples based on your experience?
A: The vast majority of bus duct systems we encounter are in dire need of repair, replacement or at minimum inspection and cleaning. The lifespan of the typical transformer is 30 or more years, depending on maintenance and load requirements.
The lifespan of a typical bus duct system is comparable provided recommended cleaning and maintenance schedules are followed. Unfortunately, most forget that when the bus duct is installed the bus duct manufacturer provides recommendations for bus duct maintenance, which involves physically inspecting and cleaning the internal IPB every outage or at a minimum every two years.
EBI has learned through discovery that recommendations from the manufacturer are not followed by many plants. Countless times we arrive to a site to discover an IPB system that has never been internally inspected.
Corona is present, dirt and debris are found throughout the system, gasketing is old and deteriorated allowing water and contaminants into the system, insulators have failed and more. In many cases, we are called in after a failure that could have been averted with proper proactive inspection and maintenance.
Doble Engineering: Doble has been in the electric power diagnostic solutions business for over 90 years. Doble’s business proposition combines three elements-diagnostics test instruments, expert consulting and testing services, and the world’s largest resource library of related knowledge – into complete diagnostic solutions.