Interference with reception of VLF switching signals transmitted over local powerlines

Swiss power companies require controlled load-shedding to limit peak power loads. They can actively shed the load by sending VLF coded signals along local powerlines to "Decabit" receivers which switch the power to boilers and washing machines in homes. Individual switching codes are also used to change kWh meters from a high daytime tariff to a low night tariff from 10 pm to 6 am. Users of such systems may defraud the power company by counteracting these commands. Several approaches were evaluated to ascertain whether the required effort and cost for potential defrauders warrants an implementation of countermeasures. The simplest and least expensive defrauding equipment appears to be a physically fairly large LC filter, to short out the signal power at a location near the receiver. The cost of suitable countermeasures is discussed