Remote sense lines often break in a test system. Without sense leads, the output voltage will typically rise on a power supply (there’s no feedback through the sense lines because the sense lines are broken). The rising voltage causes an overvoltage condition. But because the sense lines are broken, the OVP circuit doesn’t detect the overvoltage condition and, therefore, no OVP shutdown. While a tracking-remote OVP seems to be the solution for false trips, it creates the possibility of an undetected real overvoltage condition when breakage occurs in the remote sense lines.
It's best when all electrically live cable routes in the building exposed to hazards are safeguarded by suitable protection devices according to a systematic “graded protection” concept: Beginning with the end device and all the way upstream to the entry of the power lines into the building, all power lines as well as the communication lines should be provided with overvoltage protection devices of various performance classes. The protection devices shall be selected in accordance with the electrical loads at the site of installation. This concept enables implementation of overvoltage and lightning protection measures tailored to local conditions and individual requirements.
The optimum size of a conductor for a given voltage and current can be estimated by Kelvin's law for conductor size , which states that the size is at its optimum when the annual cost of energy wasted in the resistance is equal to the annual capital charges of providing the conductor. At times of lower interest rates, Kelvin's law indicates that thicker wires are optimal; while, when metals are expensive, thinner conductors are indicated: however, power lines are designed for long-term use, so Kelvin's law has to be used in conjunction with long-term estimates of the price of copper and aluminum as well as interest rates for capital.