To increase the self-consumption of photovoltaic systems, consumers must be switched on or off depending on the available feed-in power. By measuring the current at the feed-in point, it is possible to determine whether there is enough surplus power available from the photovoltaic system for the heat pump, air conditioning system, cooling unit or other large consumers. The flow direction of the electricity is also important here. Simple current relays would switch on the loads even if no current is being supplied at all, but the current drawn exceeds the threshold. Ziehl offers the COSFI100V current direction relay for this purpose: It signals when a maximum of two freely adjustable current values are exceeded in a conductor. Currents of up to 10 A(AC) can be connected directly. The transformation ratio of the current transformers used for larger currents can be programmed so that the display shows the actual active current flowing. The current direction relay can also be used as a load monitor on motors to monitor overload and underload by evaluating the active current or the phase angle cos.