A customer installed new switchgear, as well as a new transformer and reactor. A self-contained substation was installed, which included a battery bank and charger. The contract did not require the installing company to test the molded-case circuit breakers in the panel that fed the battery charger. After all, those circuit breakers probably cost less than $100 each, and it would cost more than that to test them. Additionally, considering that the equipment was brand new, maintenance personnel did not check on it often.
One night, the underground feeder cable from this new switchgear failed. The 100 A two-pole circuit breaker feeding the battery charger was defective and tripped (this 100 A circuit breaker would trip with only 45 A within 70 seconds), causing the battery bank to slowly discharge. The fault caused considerable damage to the switchgear, transformer and reactor, as the circuit breaker protecting them had no control of circuit power from the battery bank. This incident cost upward of $5.2 million, all because a $100 circuit breaker was not tested during installation.
The takeaway here is that protective devices on critical loads should always be tested and verified, regardless of the perceived value of the protective device. Although the incident did not involve a wind farm, the same concept can be applied to how your substation interacts with your wind turbines.
When most think of wind farm reliability, the focus is often on a turbine’s blades, generators and gearboxes. As the previous example illustrates, if reliability is not maintained with your main transformer or your substation, feeders, or other substation components, the entire wind farm can be compromised.
Electrical equipment is impacted by the atmosphere and conditions under which the equipment is operated and maintained. Other factors such as water, dust, temperature, humidity and vibration can harmfully affect electrical components. To improve reliability and extend the life of your electrical components, you should adopt practices that promote cleanliness, dryness, tightness and the prevention of friction.
The ABCs of RCM
Whenever equipment fails, it is important to understand the reason it failed. A root-cause analysis is a method of problem solving that tries to identify the root causes of faults or problems. Often, finding the root cause will prevent a failure from happening again and allow for continuous improvement.
To maintain the wind farm’s reliability, you should consider adopting a reliability-centered maintenance (RCM) program. Simply put, the driving factor behind RCM is maintaining substation reliability. An RCM program allows for critical analysis and deeper investigations into ensuring electrical maintenance aligns with the “critical path” of the facility. Such critical analysis can result in cost-effective solutions for preventive maintenance.
An effective RCM program should align with the critical path of your facility and ensure that specific equipment, such as main transformers (the heart of the wind farm), receives top priority. It is important to note that nonessential equipment should receive less attention, as overly maintaining your wind farm can be costly to your organization, and oftentimes, you will see diminishing returns on your investment.
There are three important philosophies of RCM:
1. The focus of RCM is to enhance the current electrical maintenance plan to improve application and cost-effectiveness;
2. Assessments for RCM help determine maintenance requirements built on the function of the system and how the equipment supports the function. RCM provides a technical foundation for preventive maintenance that is not firmly based upon regulatory requirements, original equipment manufacturer (OEM)standards or industry standards; and
3. The focus is on equipment critical to maintain important system functions. Therefore, RCM emphasizes proactive, predictive maintenance techniques over traditional, time-directed maintenance techniques.
Predictive, proactive and preventive maintenances can often be done while the wind farm is online and can be performed by the owner. Infrared scans, transformer oil samples and even some types of cable testing are cost-effective solutions for predictive maintenance.
You have probably used industry best practices and OEM recommendations, such as ANSI/NETA maintenance and testing specifications, to develop your electrical preventive maintenance program (EPM).
An important element in an effective RCM program should include a failure mode effects and criticality analysis (FMECA). A FMECA is a tool commonly used for failure analysis and includes a criticality analysis, which charts the probability of failure modes against the severity of their consequences. RCM challenges you not to just replace the component, but also to find the root cause of the failure to prevent the failure from happening again. Prevention of the failure will increase the reliability of your wind farm.
It is often said that spending $1.00 on maintenance will get you $5.00 in return. With that said, having an EPM is a good start; however, it is time to take your maintenance to the next step.
RCM will help you take the next steps to predict when and where your next failure will occur. By using the RCM analytics, you can find the root cause to the failure and prevent the failure from happening in the future, while increasing your reliability. Remember, what piece of equipment can take down your entire wind farm? What is the lead time on the particular piece of equipment? w
Industry At Large: Wind Farm Reliability
How Substation Maintenance Impacts Reliability
By Paul Idziak
When it comes to reliability and wind farms, many people focus on the blades, generators and gearboxes. However, substations play an integral role in a wind farm’s operating performance.
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