What’s the meaning of transformer product model and letters

A: The product model using Hanyupeng capital letters or other suitable letters to represent the main features of the product, with Arabic numerals that the product performance level code or design serial number and code specifications.

Examples:First: S - three-phase; D - single-phase. Second: S - three windings; E - double windings. Third place: O - auto. F - non-auto. Fourth place: Z - load voltage regulator; W - no excitation voltage regulator. Fifth: O - oil insulation; G - SF6 insulation. Sixth: (internal cooling) N - natural circulation; F - forced circulation; D - forced to guide the cycle. Seventh place: (external cooling method) A - air; W - water. Eighth place: N - natural circulation; F - forced circulation. "The previous figure - rated capacity (kVA). "" After the figure - rated voltage (kV).The company is located in: