ABSTRACT
Many cases of malfunctions and even damage of microprocessors are caused as a result of the impact of electromagnetic disturbances from the power supply network in the operation of digital protective relays (DPR). DPRs also have a wide interval of characteristics on allowable voltage reductions. The internal switching-mode power supply of the DPR contains, as a rule, a smoothing capacitor of rather large capacity, capable of supporting the function of the relay during a short time period. Power units are supplied by powerful accumulator batteries with a constantly connected charger, or by an uninterrupted power supply cushioning the negative impact of the factors listed; however, the same system supplies driving gears of power switches and many other devices, causing spikes. The power capacity of the inverter makes mill watts, which are spent only for compensation of self-discharging of the capacitor.
