Transformer Services
1. Transformer Oil Sampling/Analysis
- Dielectric strength
- Moisture content
- Acid
- Gas content (DGA)
- PCB content
- Furan analysis of transformer
- Tan Delta
- Interfacial Tension
The annual oil sample is the most important part of transformer maintenance which should never be over looked. The sample drawn will tell you the exact conditions of internal operations thus pointing out any need for concern or if any attention is required at all.
2. Purification/Filtration of transformer oil
The process conducted to enhance the life span of transformers and save clients money in the long run by keeping transformer oil within SABS/SANS standards without doing an unnecessary oil change. We consist of skilled teams that can do on site purification and under the right conditions live purification can be done to save clients very costly down time.
3. Supply of transformer oil
We as a Transformer maintenance company also supply clients with Virgin and Regenerated oil needed for annual maintenance work.
- Virgin oil
- Regenerated oil supplied
- Regenerated oil on exchange
4. Supply of transformer components
- Silica gel
- Breathers
- HT & LT bushings
- Bucholz relays
- Oil temperature gauges
- Winding temperature gauges
- Sight glass / Oil level indicator
5. Repair or replacement of
- Leaking gaskets
- Cone rubbers
- Transformer bushings
- Drain valves
- Bucholz relays
- Transformer covers & cable boxes
6. Spray painting
Spray painting of transformers on site and in our repair facility (according to specification)
7. Protection Testing
Protection relay testing involves verifying the functionality and accuracy of protection relays in an electrical system. These relays are designed to detect faults, such as short circuits or overloads, and isolate the faulty part of the system to prevent damage. Testing ensures that relays are operating as intended, providing reliable protection to equipment and personnel.
Key aspects of protection relay testing include:
- Functional Testing: Verifying that the relay responds correctly to simulated fault conditions, such as overcurrent, undervoltage, or differential faults.
- Time-Current Characteristics: Checking the timing and current settings of the relay to ensure that they match system protection requirements.
- Calibration: Adjusting the relay to ensure it operates within the correct settings for specific protection schemes.
- Communication Testing: Ensuring that relays with digital communication capabilities (like IEC 61850) are correctly configured and communicating with supervisory control systems.
- Power Supply Testing: Ensuring the relay operates correctly with the power supply voltage.
- Simulation of Fault Conditions: Using test equipment (like a relay tester or a secondary injection test device) to simulate faults and verify the relays response.
By conducting thorough testing, technicians can confirm that the protection system will function as expected during an actual fault scenario, reducing the risk of equipment damage and improving overall system reliability.
8. Primary and Secondary Injection Testing
Primary and Secondary Injection Testing are two common methods used to test and verify the functionality of protection relays in electrical systems. Both methods ensure that relays will perform correctly when subjected to real-world fault conditions, but they differ in how they simulate these conditions.
Primary Injection Testing:
Primary injection testing involves injecting fault-level currents directly into the system, simulating real fault conditions. This test is done at the primary side of the protection device (i.e., the actual high-voltage circuit).
Key aspects:
Direct testing: A high-current source is used to apply fault currents directly to the protection relay's primary inputs. Simulating real fault conditions: The relay is tested under full system fault conditions, such as short circuits, overloads, or phase imbalances. High-voltage equipment: This test is often conducted on high-voltage equipment, and the tester must be designed to handle large currents. Applications: Used for testing protection relays in industrial power systems, substations, and power plants.
Advantages:
Provides a more realistic test by applying actual fault conditions. Can test the entire protection scheme, including the relay and associated equipment.
Disadvantages:
Requires access to high-voltage systems, which can be more dangerous and costly. Involves higher power levels, which may require specialized equipment.
Secondary Injection Testing:
Secondary injection testing is a safer, more controlled method in which test currents (often lower in magnitude) are injected into the secondary side of the protection relay, usually using a testing device like a relay test set.
Key aspects:
Simulated fault conditions: Test signals or currents are injected into the relay's secondary or control circuit, simulating fault conditions without the need to apply high currents directly to the primary circuit. Low-voltage testing: This test is typically done on the low-voltage side of the protection relay, which is safer and more accessible. No need for high-power equipment: Secondary injection uses much smaller current levels, making it safer and more cost-effective. Applications: Typically used during factory testing, commissioning, or routine maintenance of relays and protection schemes in low and medium voltage systems.
Advantages:
Safer and easier to conduct compared to primary injection testing. Requires less equipment and is more cost-effective. Can test the relays response to various faults without disrupting the actual power system.
Disadvantages:
Less realistic than primary injection, as it does not replicate the actual fault conditions on the high-voltage side of the system. May not fully simulate certain fault scenarios, such as those involving high fault currents.
Primary Injection
More accurate for full-system fault simulation, but requires higher power and involves greater risks.
Secondary Injection
Safer, more economical, and easier to conduct, but may not replicate fault conditions at the same scale as primary injection.
Both types of testing are valuable and often used together to ensure the proper functionality of protection relays and the overall protection system.
1. Inspection and Assessment:
Visual inspection: Checking the exterior for signs of damage, oil leaks, rust, or contamination. Electrical testing: Performing insulation resistance, dielectric strength, and power factor tests to assess the internal condition of the transformers insulation system. Oil analysis: Testing the transformer oil for contaminants, moisture, and the presence of gases that indicate deterioration or faults. Thermal scans: Using infrared thermography to detect any hot spots or abnormal heating in the transformers windings or connections.
2. Disassembly and Cleaning:
Drain and dispose of old oil: If the oil is found to be contaminated or degraded, it is removed and replaced with fresh, high-quality transformer oil. Disassemble components: The transformer may be partially or fully disassembled, depending on the level of refurbishment required. Cleaning: All parts, including bushings, tap changers, radiators, and the core, are cleaned to remove dirt, dust, oil residues, and other contaminants.
3. Replacement or Reconditioning of Parts:
Insulation renewal: Worn-out insulation materials (such as paper or pressboard) may be replaced to restore the dielectric properties and enhance the transformers insulation. Winding reconditioning: If the windings are damaged or deteriorated, they may be cleaned, repaired, or replaced. In some cases, they may be rewound with new wire. Tap changer servicing: The on-load tap changer (OLTC) is often disassembled, cleaned, lubricated, or replaced if it shows signs of wear. Bushings replacement: Aging or damaged bushings are replaced to ensure proper electrical insulation at the points where the transformer connects to external circuits.
4. Core and Coil Restoration:
Core inspection: The core is examined for any signs of mechanical damage, corrosion, or overheating. In some cases, it may need to be reconditioned or re-laminated. Winding checks: Transformer windings are thoroughly checked for any damage, corrosion, or short circuits. They may be re-tensioned, cleaned, or even replaced if necessary.
5. Testing and Reassembly:
Electrical testing: Before refurbishing, the transformer undergoes rigorous testing, such as: Insulation Resistance Test Turns Ratio test DC Winding Resistance Test Short Circuit Impedance Test Ratio and Insulation resistance tests on CTs Tan Delta testing on windings and bushings Operational tests of auxiliary equipment Reassembly: Once all the components have been reconditioned and tested, the transformer is reassembled and filled with new oil (if required).
6. Final Acceptance Testing and Commissioning:
Final testing: After the transformer is refurbished and reassembled, comprehensive acceptance testing is conducted to ensure it operates correctly and safely under normal operating conditions. Commissioning: The transformer is placed back into service, often with monitoring systems to track its performance and condition during its extended service life.
Benefits of Refurbishing a Transformer:
Cost-effective: Refurbishment is often more economical than purchasing a new transformer, especially for large or custom-built units. Environmental impact: Refurbishing extends the life of the transformer, reducing the need for new manufacturing and the disposal of old units. Increased reliability: Refurbished transformers can often meet or exceed the original specifications, improving overall system reliability. Extended lifespan: A well-refurbished transformer can often operate for many more years, reducing capital expenditure on new equipment.
When is Transformer Refurbishment Needed?
Aging transformers: Older transformers that are still functional but have deteriorated over time may benefit from refurbishment. Minor faults or damage: Transformers that have sustained minor damage, like insulation wear or oil contamination, can often be repaired through refurbishment. Obsolete models: If the transformer is no longer in production but still vital to operations, refurbishment can bring it up to current standards.
Conclusion:
Transformer refurbishment is a critical process for maintaining the reliability and efficiency of electrical systems. It allows utility companies and industrial plants to extend the operational life of expensive transformer equipment, mitigate the risks of failure, and improve performance while saving on the costs of new installations.
10. Supply , Installation and Commissioning of New and Refurbished Transformers
Providing both brand-new and overhauled electrical transformers, setting them up at the designated location, and ensuring they are fully operational. This involves the delivery of transformers, their safe installation, thorough testing, and the final commissioning to ensure they meet performance standards and safety requirements for efficient electricity distribution or power transformation.
11. Infra-Red Scanning
Infra-Red (IR) scanning on transformers and substations is a non-invasive diagnostic technique used to detect potential issues by capturing thermal images. This process involves using infrared cameras to identify hot spots or abnormal temperature variations in electrical components, such as transformers, circuit breakers, busbars, and connections. Elevated temperatures can indicate problems like loose connections, overloading, or equipment wear. By conducting IR scanning, maintenance teams can proactively identify faults, prevent failures, and enhance the reliability and safety of the electrical infrastructure.
12. On Load and Off Load Tap Changer Services.
On-Load and Off-Load Tap Changer services refer to the maintenance and operation of tap changers in transformers, which adjust the voltage levels to ensure stable power supply.
On-Load Tap Changer Services: These services are related to tap changers that allow voltage adjustments while the transformer is under load (i.e., during operation). OLTCs are crucial for regulating voltage fluctuations without interrupting the power supply. Services include inspection, cleaning, lubrication, repair, and testing to ensure optimal functionality and prevent operational failures.
Off-Load Tap Changer Services: Off-load tap changers require the transformer to be de-energized to adjust the voltage. These services involve maintenance tasks like inspections, cleaning, and replacements when the transformer is not in use. These changers typically need less frequent maintenance, but ensuring they operate correctly is important for efficient transformer performance.
Both types of tap changers require regular servicing to ensure reliable voltage regulation and transformer longevity.
13. Standby Transformers
Keeping standby transformers in stock for emergency situations involves maintaining a ready inventory of spare transformers that can be quickly deployed in case of an unforeseen failure or disruption in the power supply. These transformers are stored in a secure location and regularly inspected and tested to ensure they are in optimal condition. In emergency situations, a standby transformer can be rapidly installed to replace a faulty unit, ensuring minimal downtime and uninterrupted power to critical infrastructure. This proactive approach helps mitigate risks, maintain operational continuity, and minimize potential losses due to power outages.
14. Rigging and Transporting of all types of Transformers.
Rigging and Transporting of Transformers involves the safe and efficient handling, lifting, and moving of transformers from one location to another, ensuring that they are properly secured during transit. This process includes:
Rigging: The use of specialized equipment, such as cranes, slings, hydraulic jacks, slides and rollers, to lift and position transformers, often heavy and large, onto transport vehicles. Rigging ensures that the transformer is moved safely without causing damage to the equipment or surrounding infrastructure.
Transporting: The actual movement of transformers, either within a site or between locations, typically using flatbed trucks or heavy-duty transport vehicles. The transformers are secured properly to avoid shifting or damage during transit. In some cases, special permits or escort vehicles are required for transporting oversized transformers over public roads.
This service ensures that transformers are safely relocated or delivered to installation sites, minimizing downtime and ensuring the equipment arrives in proper working condition.
Complete refurbishment of transformers in accordance with SABS standards and client's specifications.
