Sheath-sectionalizing joint

The sheath-sectionalizing joint is mathematically expressed by a rotation matrix [R] ... 

For submarine cables, it is more common to adopt solid bonding due to the difficulty in constructing joints offshore, as shown in Figure 3.3. Hence, submarine cables have higher sheath currents compared to underground cables that are normally crossbonded. In order to reduce the loss caused by higher sheath currents, the sheath conductors of submarine cables often have a lower resistance (i.e., a larger cross section). 

The lengths of the minor sections can have imbalances due to constraints on the locations of joints. The imbalances are designed to be as small as possible, since they increase sheath currents and raise sheath voltages. When a cable system has multiple major sections, the overall balance is considered for minimizing sheath currents. As a result, when a cable system has more than two major sections, sheath currents are generally balanced among three conductors, which allows for the reduction from three metallic sheaths to one conductor [4,5]. 

Since the three-phase sheath conductors are short-circuited and grounded in every major section as illustrated in Figure 3.6, the sheath voltages of three phases are equal at each earthing joint. Assuming sheath currents are balanced among three conductors, the sheath currents do not flow into the earth at each earthing joint ... 

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