Distribution transformers are an often-overlooked electrical asset. Tucked away in the corner or hidden in a substation, enjoying a typical service life of around 25 years, and possessing virtually no moving parts, they are often installed and then promptly forgotten. While electrical equipment with movable parts, such as motors or circuit breaker, typically get regular preventative maintenance attention, transformers are left to gather dust and fend for themselves in some forgotten corner of the site.
Unfortunately, both the operating environment and maintenance play a significant role in the life of all electrical equipment; transformers included. The frequency, severity, and duration of overloads, the construction, loading, type of insulation system and a host of other factors play a significant role in determining service life.
Plant and facility space is at a premium and most often transformers are tucked away and installed in architecturally convenient dead spaces, which environmentally are less than ideal, where they remain largely forgotten; until they unexpectedly fail and someone in senior management starts screaming at the operations team and demanding to know why. At that point some unfortunate facilities manager, plant engineer, or maintenance coordinator is struggling to explain how this critical piece of equipment was overlooked.
Fortunately, there’s a host of testing, monitoring, and diagnostic techniques available to help assess the condition of electrical distribution equipment. Ideally, you’ve already been testing and monitoring the equipment at your site, and you have a history with data to trend. If not, the process is a little more challenging but, it’s not too late to start. Problems such as overheating, arcing, partial discharge, contamination, and degradation can be detected and diagnosed through routine testing and annual oil sampling helping to prevent potential problems with the transformer.
Transformers offer a host of inspection and testing techniques that vary by transformer type but can provide useful insight into the condition and life span of the device.
1. Visual Inspection: A thorough visual examination of the transformer can identify signs of damage, structural integrity, corrosion, or other physical issues.
2. Transformer Insulation Testing: Measuring insulation resistance is used to assess the health of the insulation system and identify potential issues.
3. Turns Ratio Testing: Verification of the transformer's turns ratio ensure sproper voltage transformation and detect any winding issues.
4. Power Factor Testing: Assessing power factor is helpful in evaluating the condition of the insulation and identify dielectric losses.
5. Oil Analysis: Testing and analysis of transformer oil to detect contaminants, provide insight on internal conditions, assess insulation condition, and identify potential internal faults.
6. Dissolved Gas Analysis (DGA): Monitoring and analysis of gases dissolved in transformer oil to detect incipient faults, aging, insulation condition, and other potential issues.
7. Partial Discharge Testing: Detection of partial discharges within the transformer helps to identify insulation weaknesses and potential failure points.
8. Transformer Winding Resistance Measurement: Measuring winding resistance helps to assess the condition of the transformer windings and internal connections.
9. Bushings and Tap Changer Inspection: Inspection and testing of bushings and tap changers helps to ensure proper functioning and identify any abnormalities.
10. Load Tap Changer (LTC) Maintenance: On larger transformers equipped with a LTC, inspection, lubrication, and regular testing of load tap changers helps to ensure proper voltage regulation.
11. Cooling System Evaluation: Assessment of the cooling system, including fans and radiators, to ensure effective heat dissipation, help retain nameplate capacity, and prevent overheating.
12. External Grounding Inspection: Often overlooked verification of the transformer's external grounding system ensures electrical system safety and compliance with regulations.
13. Repair and Refurbishment: Once identified, follow through and implementation of all necessary repairs, replacement of defective or faulty components, and insulating fluid refurbishment will extend the transformer's operational life.
Partnering with a trusted engineering services provider can help close that experience gap and identify issues before they cause performance problems. Evaluating your electrical system, performing regular testing and maintenance, completing power system studies and proper protection and coordination will help ensure the reliability, safety, compliance, and longevity of the plant’s electrical assets. An engineering study reviews and evaluates the current state of your plant or facility by identifying potential hazards, operational issues, equipment and maintenance short comings, and looks to find the coordination issues and system limitations that lead to unplanned outages while uncovering the root cause of pending failures before they happen.
Are you prepared for the summer storms, brownouts, and outages? If not, EnerG Test would like to help!!