An Improved Approach to Calculate a Zero-Sequence Impedance of an XLPE-cable Group

Single-core X-linked polyethylene (XLPE) cables are widely dispersed in 110-500 kV grids and supposed to replace traditional overhead lines due to different advantages, such as higher operating temperature, its compactness, etc. However, the construction of XLPE cable lines is complex, which defines many difficulties in calculation of its zero-sequence impedance, especially in the case of a group of several cable lines laid in one trench. The number of cable lines laying in one trench may vary from 4 to 6, and several cable lines may be placed in less than one meter between each other. In this case, the mutual inductance may take significant values and should be taken into account in the zero-sequence impedance calculation. This paper outlines a practical approach allowing for the calculation of the zero-sequence impedance precisely. This approach is based on matrix transformations.