The invention discloses a
current transformer for a
transformer substation, which prolongs the position of an oil drain port, expands the function of the oil drain port and is very practical. In addition, by improving the top protective cover and the interior of the top protective cover, the height of an expander can be observed more clearly, and the operation process of the expander can be conveniently limited through a limiting
assembly integrated inside the expander. According to the invention, a tee joint is mounted at an oil
discharge port and comprises an oil
discharge port interface used for being mounted with the oil
discharge port, a reserved interface used for being connected with a plug or an
oil pressure monitoring sensor and an interface used for being connected with a leading-down sampling
pipe; a leading-down oil discharging valve is mounted at the bottom of the leading-down sampling
pipe; a window is formed in the top protective cover, a circle of rubber frame is installed on the inner wall of the window, an indication line observation window is installed in the rubber frame, and the outer edge of the rubber frame is coated with a circle of waterproof glue; the expander is coated with a circle of position indication line; and an expander oiling and oil taking limiting
assembly is mounted in the top protective cover.