Seek advice on the selection of short-circuit reactance for autotransformers
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I am currently involved in the design and selection work for an LNG station at the institute. The compressor in the LNG station has a power rating of 11,500 kW; it is an 10 kV ABB synchronous motor, with a starting current of approximately 4.3 times its rated current. The power distribution system features one 35 kV incoming line, which is transformed via a 35/10 kV transformer. ABB recommends using LCI (soft start) to address system voltage drop issues. Our calculations show that an autotransformer can also meet 78% of the requirements for starting and system voltage drop. However, there are issues with the selection of the short-circuit reactance for autotransformers, and no relevant information is available on how to choose this value. I would appreciate your guidance on selecting the short-circuit reactance for autotransformers.
Given such high power levels, it is recommended to use a soft starter. Starting with a reactor requires many more devices and takes up more space; although the cost is much lower, a soft starter only needs one switch cabinet (equivalent to the space of two cabinets). In contrast, a reactor-based system requires that much space, plus there are also a bypass circuit and a start switch cabinet, which adds to the complexity.
2# Extremely attractive. Compared to the LCI method, only one additional side is added to the medium-voltage cabinet. The floor space required for an autotransformer is similar to that of an LCI (except that an oil-immersed type requires a separate transformer room); additionally, some LCIs need transformers of different voltage levels ； The cost is several million dollars lower after getting quotes.
If a soft start method is used, feel free to contact me!