Recommendation of site commissioning tests for rapid recovery transformers with an installation time less than 30 hours

摘要

Transformer testing is an indispensable procedure to guarantee that transformers are fulfilling all requirements and guaranteed values. After completed FAT (Factory Acceptance Test), to proof the transformer design, site commissioning test shall be performed to detect potential transport damages or faults at site installation before energizing the transformer. As a minimum requirement, we recommend to perform a dissipation factor (tan δ)-, TTR (Transformer Turns Ratio)-, insulation resistance-, ohmic resistance and SFRA (Sweep Frequency Response Analysis) measurement for conventional transformers as site tests. Depending on circumstances, various additional tests can be performed according to customer requirements. For transformer or reactor site works, the installation time might be critical (e.g. outage time of a power plant) but can be planned in advance. In case of an emergency, the time between failure and energizing the replacement unit is crucial. But also under time pressure, to dispense on site test is saving on the wrong place, and may lead to huge technical damages and monetary losses. A different approach to overcome a long installation and commissioning time are multi ratio and lightweight single phase transformers filled with environmental friendly synthetic ester, which can be transported without any special transport permits. This has also been proven at a demonstration run where it took just 30 working hours within three working days, to install, test and energize a 345 kV transformer bank, three 1-phase units each 100 MVA, which worked then in regular network operation including overload conditions. We give some recommendation about the required site tests, due to the fact that these transformers are more complex compared to conventional transformers. The higher complexity is justified by the fact that the resilience transformers are covering many different transformer designs and can be installed very flexible in the shortest possible time on site.