Based on electroluminescent (EL) effect,an optical voltage sensor is designed an d demonstrated experimentally using EL wire.The proposed voltage sensor is suitable for the measurement of 50Hz ac voltage.The ZnS dope d by Cu is used as the EL material in the wire,which can emit visible light with peak wavelength of 525nm under 50Hz ac voltage.The voltage-sensitive l ight signal is transmitted to a photo detector through a plastic optical fiber.In a certain voltage range,the open circuit voltage of the photo-detector approximately has linear relationshi p with the effective value of the applied ac voltage.The 50Hz ac voltage in the range of 100－500V was measured with nonlinear error less than 1.8%,and the voltage measurement sensiti vity is 10.8μV/V.Electroluminescent spectrum,input impedance,and temperature dependence of EL intensity of the used EL wire were also measured.Different from previous optical voltage sensor using electro-opti c crystal,the proposed voltage sensor doesn′t need any light source,and has advan tages of low cost,simple configuration,etc.