In this paper, a 35KV step-down substation is designed. The high voltage side is 35kV, and the low voltage side is 10kV. First of all, the number and capacity of the main transformer are determined by the size and nature of the load in the original data, and the model of the main transformer is selected. Secondly, according to the requirements of reliability, economy and flexibility, the main wiring mode is determined. Then, the calculation of short-circuit current is carried out, and the effective value of cycle component of short-circuit current and short-circuit impulse current are calculated according to each short-circuit point. According to this result, the main electrical equipment including circuit breaker, disconnector, fuse, voltage and current transformer, bus and so on are selected and verified. Finally, in order to ensure the safe and reliable operation of the substation, the relay protection design and lightning protection design are carried out.
KEY WORDS: substation;the main transformer substation;main wiring;short circuit current alculation;electrical equipment