Electric stresses in three-core cables equipped with optical fiber sensors

XLPE cables equipped with optical fiber sensors for on-line fault and problem detection are being manufactured and installed, particularly at the 66 kV level. The insertion of these sensors which generally possess electrical properties different from those of the cable insulation, is expected to influence the electric field distribution in the space surrounding the HV conductors. This situation in turn affects the `electric stress´ on the HV insulation. This paper examines those effects not only in terms of subsequent alterations in electric field magnitude but also the changes in the orientation of the field´s elliptic polarization which is prelude to the possible initiation of local discharges within the insulation. The boundary element technique is applied to simulate sheathed three-core belted cables with fiber sensors. With an adequate number of strip charges, this method is used to calculate the electric field distribution in a 66 kV power cable containing optical fiber units. The variation of the electric stress at critical spots within the insulation with the location of the sensor and the permittivity of its insulation material is investigated