Today is a short post. It is about the need for thorough control of all stages of the cable line life cycle. And especially for the project and installation. The photo shows a 110 kV cable line, for which the cross-bonding of the screens was to be made according to the project. However, the installation company did not have the necessary type of cable joints. Therefore, they decided to do the cross-bonding with improvised means right in the trench. They did the following:
1️⃣ Removed a short section of the outer sheath of the 110 kV cable.
2️⃣ Cut the copper screen of the cable, dividing it into left and right.
3️⃣ Connected the left and right screens to the coaxial “bonding” cable.
4️⃣ Applied heat shrinkage to the junction, as well as they could.
5️⃣ Wrapped scotch tape on top of the junction, for “reliability”.

Such a line has successfully passed all commissioning sheath tests and worked successfully for several years, and only then the specified place got wet enough so that during subsequent tests of the outer sheath it could not withstand DC 10 kV. When test team started locating the place of damage to the outer sheath, they found such a miracle cable joint.

A branching of one cable (bonding cable) from another (main one) is a serious task. This is not the right place to use just tape (even really good), much less ordinary basic cheap “household scotch.” Joint manufacturers spend huge amounts of money on developing and testing reliable joint designs. And thank them for that, since otherwise cross-bonding wouldn’t work properly.

What are the conclusions?
✅ Find a trusted person who will be present at all stages of laying and installing your cable. Let him take photos and videos. Let him launch the drone and fly to places inaccessible to him, along all the line route. It’s worth a penny compared to how much you can lose if the cable is laid and installed incorrectly.
✅ Read the book (Part 3), it says very well how cross-bonding works. It shows very well how you can calculate it yourself using a pocket calculator, and thereby check the proposed project and the induced AC 50 Hz voltages, currents and power losses.

All projects/installations will seem “successful” until you study them more thoroughly. Please, never leave your cable unattended! Treat the cable like a child!

PS
There are important holidays in April, and there is a good book offer for these days. Present this book to yourself and your colleagues. It will help to perform calculations and, therefore, check the projects and fix the typical design errors that occur there. The book is not IEC, it is a hundred times simpler and clearer.