When manufacturing power cable terminations for cable distribution boxes, attention should be paid to separately leading out grounding wires for the cable's metal shielding layer and armor layer, ensuring reliable grounding. Do not connect the cable's metal shielding layer and armor layer internally before leading them out together for grounding.
Separately grounding the metal shielding layer and armor layer facilitates the insulation testing of the cable's inner sheath. For cross-linked polyethylene (XLPE) insulated power cables, cable distribution boxes must undergo the "cable inner sheath insulation resistance test" and the "copper shielding layer resistance to conductor resistance ratio test". If the cable's metal shielding layer and armor layer are welded together internally, the above tests cannot be performed.
During the installation of high-voltage cable lines, when the metal sheath of a single-core cable line is grounded at only one point, the induced voltage at any point of the metal sheath shall not exceed 50~100V (not greater than 50V if no safety measures are taken to prevent arbitrary contact with the metal sheath; if effective measures are adopted, it shall not be greater than 100V, and the metal sheath shall be insulated from the ground).
If the induced voltage of the cable distribution box exceeds this specified value, the metal sheath shall be insulated in sections or connected into a cross-bonded configuration after insulation. To reduce the impact of single-core cable lines on adjacent auxiliary cables and communication cables, the cross-bonding connection method should be adopted as much as possible, with grounding through cable cross-bonding grounding boxes. To protect the cable sheath insulation, a cable sheath protector shall be installed at the ungrounded end.
For more information, please visit China - DAYA Electric Group Co., Ltd. at https://www.hygraphics.com/