The utility model relates to a high-voltage measurement and protection device of a power system, in particular to an indoor three-phase electronic current transformer. The transformer comprises an insulator, and an A-phase coil, a B-phase coil, a C-phase coil and a zero-sequence coil which are sealed in the insulator, wherein the A-phase coil, the B-phase coil and the C-phase coil are sleeved in the zero-sequence coil at equal intervals; secondary lead terminals of the A-phase coil, the B-phase coil, the C-phase coil and the zero-sequence coil are arranged at the bottom of one side of the insulator; a secondary leading-out wire of the A-phase coil is connected with an A-phase sampling resistor in parallel, a secondary leading-out wire of the B-phase coil is connected with a B-phase sampling resistor in parallel, a secondary leading-out wire of the C-phase coil is connected with a C-phase sampling resistor in parallel, and a secondary leading-out wire of the zero-sequence phase coil isconnected with a zero-sequence sampling resistor in parallel. The device can be conveniently connected with interfaces of a digital instrument and a microcomputer protection control device, and functions of metering, control, measurement, protection and data transmission are realized.