EHV lines require ___ at suspension points and dead ends to prevent the magnetic fields from concentrating in any given location.

High Voltage (EHV) lines are designed to transmit electricity efficiently over long distances, which necessitates managing the electromagnetic fields generated by the high voltage. At suspension points and dead ends, the electric fields can become concentrated, potentially leading to unwanted electrical discharge, radio interference, or safety hazards.

The use of corona shields is crucial in these scenarios as they help to disperse the electromagnetic fields created around high voltage lines. By providing a physical barrier, these shields prevent the buildup of voltage that could otherwise lead to corona discharge or arcing. This is particularly important at points in the system where the wires are suspended or where they terminate, as these are locations where electric fields can intensify.

Insulators are important for preventing electrical short circuits and ensuring that power does not transfer to unwanted surfaces, but they do not specifically address the concentration of magnetic fields. Magnetic shields are typically used in applications involving electromagnetic interference, not specifically for EHV lines. Ground wires serve key functions, such as providing protection against lightning and ensuring safety, but they do not mitigate the concentration of magnetic fields at suspension points and dead ends.

Thus, the selection of corona shields as the correct answer reflects their specific role in managing and redistributing the magnetic fields around extended high voltage lines,