Method and apparatus for determining the insulation state of an object made of an electrically conductive material coated with electrically insulating material and placed in an electrically conductive medium

摘要

PCT No. PCT/FI87/00107 Sec. 371 Date Apr. 6, 1989 Sec. 102(e) Date Apr. 6, 1989 PCT Filed Aug. 26, 1987 PCT Pub. No. WO88/01748 PCT Pub. Date Mar. 10, 1988.The invention relates to a method for the determination of the condition of the insulation of an object (1) made of an electrically conducting material, coated with an electrical insulation (2) and positioned in an electrically conducting medium. According to the invention, the determination of the condition of the insulation is carried out without any electric contact with the object to be monitored in such a way that a first electromagnetic field (6) is created in the conducting medium (3), which field induces eddy currents (7, 8) both in the medium (3) and in the conducting object (1) positioned therein, a second electromagnetic field created by the eddy currents (7, 8) passing both in the conducting medium (3) and in the conducting object (1) is measured in the form of electrical information, essentially excluding the effect of the first electromagnetic field, and said electrical information is analyzed for detecting any changes in the condition of the insulation.