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This internal arcing has been one of the most catastrophic modes of failure that could potentially produce personnel hazards, long-duration outages, as well as, full loss of the power transformer. Internal arcing is a must-exclude technology for large power distribution, and is totally off the table for both renewable power and for industrial applications. In recent decades, the oil immersed transformer has undergone significant changes, advanced design principles, materials science and strict testing protocols that have greatly minimized the risk of internal arcs which are evident in the transformer. At Jiangsu Ryan Electric Co., Ltd., we design our oil immersed transformer products in layers of protection against the failure caused by the arc. Our CNAS-accredited 35 kV and 110kV test laboratories and compliance with IEEE, IEC and CSA standards ensure the transformers' reliability—trusted by clients including Microsoft and State Grid in over 50 countries.
Optimized Insulation Coordination and Dielectric Design
The basic steps towards arcing prevention in an oil immersed transformer lie in its dielectric system. Today's designs use sophisticated insulation coordination to ensure that the voltage stresses are distributed to every winding, barrier and lead exit. Each of these oil immersed transformers at Jiangsu Ryan Electric are computationally analyzed for optimum placement of the pressboard insulation, angle rings, and electrostatic shields so as to minimize the potential for partial discharge to occur (a precursor to complete arcing) through the removal of excessively amplified field areas. Our transformers undergo extensive lightning impulse and switching impulse testing in our state-of-the-art test bays to ensure insulation systems are capable of surviving transient overvoltages much higher than normal operating conditions. Additionally, high quality kraft paper and thermally upgraded insulation materials are used—so that the dielectric strength of the transformer will not deteriorate under thermal cycling and moisture ingress conditions typical in outdoor substation applications throughout the transformer's service life.
Superior Fluid Quality and Active Filtration Systems
Oil immersed transformers do not just have insulating oil to passively provide a barrier between the parts, it is a line of defense against arcing. The high purity mineral oil or ester based fluids have excellent dielectric properties and arc-quenching properties which deteriorate with time because of oxidation, moisture absorption and particulate contamination. We tackle this issue at Jiangsu Ryan Electric by adopting a strict control on oil processing during production, which includes vacuum filling, degassing and dehydration to ensure the oil contains less than 10 ppm moisture and high dielectric breakdown voltage of more than 70 kV. Our oil immersed transformer designs also include oil preservation systems, including a nitrogen blanket or conservator tank, to reduce exposure to the atmosphere and to preserve the fluid quality. Clients in environmentally sensitive or high-risk installations benefit from sealed tank designs which eliminate the possibility of the insulating fluid being exposed to the external environment, thus maintaining a constant dielectric performance and greatly minimizing the chance of the tank developing an arc.
Robust Tank Construction and Arc Relief Mechanisms
While prevention is the primary goal, modern oil immersed transformers also account for the rare occurrence of an internal arc with passive safety features that help limit damage and keep personnel safe. Jiangsu Ryan Electric produces tanks with high quality steel, reinforced seams, pressure-relief mechanisms—such as sudden-pressure relieving, rapid-decompression valves. These components sense the rapid pressure rise that accompanies arcing, and respond in a fraction of a millisecond to release the gases inside before tank rupture occurs. Also, our oil immersed transformer designs include conservatively sized gas-cushion spaces and pressure-relief ducts to divert gas in the event of an arc away from the winding area. Such a combination of structural strength and active pressure control means that if an arc does occur the transformer will be contained and will not create a hazard to other equipment or personnel. The overpressure and vacuum tightness are confirmed by our factory routine tests, so all the transformers that leave the factory comply with the most stringent international safety requirements.
Comprehensive Testing and Condition Monitoring
The best way to prevent arcs is to combine quality assurance at the production line with continuous monitoring as the device is used. Our test bays accommodate dry-type, liquid-immersed, and substation transformers, subjecting each to comprehensive routine, type, and special tests. These tests are conducted in accordance to UL, ASTA, CE and DEKRA certified tests including partial discharge measurement, induced overvoltage withstand and short circuit testing. In addition to factory tests, our solutions for oil immersed transformers integrate with online monitoring systems for dissolved gas analysis (DGA), temperature profile and bushing condition. Predictive maintenance interventions can be made several steps ahead of the arcing conditions when anomalous gas generation (like acetylene or hydrogen) is detected early. The combination of engineering precision, state-of-the-art materials and monitoring compatibility, guarantees that Jiangsu Ryan Electric's oil immersed transformer products offer the most effective arc-risk mitigation on the market today to utility operators and industrial clients.