Voltage Band Relays protect equipment that is required to operate within an upper and lower voltage limit. VMP Series and VAKP Series provide Over/Under voltage protection. VMP240A - Protection Relay Overvoltage, Undervoltage Socketable from Macromatic Industrial Controls. Versions are available in. tentially damaging. They are designed to energize when the operating voltage reaches a preset value and drop-out when the operating voltage drops to a level be in the table below. under/over / unbalance Voltage / reverse phase sequence / singe phasing) Protection - [Fixed Setting - Single Phase Prevention, Phase Sequence & Unbalance (10%)], Time Delay - Trip Ti.