Improvements to control of transformer-fed electrical power supplies

A distribution feeder apparatus 601 for controlling a transformer fed electrical power supply in relation to a load is especially suitable for a railway network signaling power distribution system. The apparatus 601 includes a passive circuit comprising a resistor network 604 which limits the current when in circuit, and an active circuit comprising a semiconductor switch assembly 611, 612 (for example thyristors) such that the active circuit is configured to maintain the voltage when in circuit. It also includes transducer(s) 615, 703 for sensing characteristics of the waveform of the current or the voltage, and a controller configured to monitor the sensed characteristics in order to distinguish an increase in current due to an inrush event from that of a short circuit. In the event of inrush current, the passive circuit is configured to be in circuit to limit the inrush current and a blocking signal may be sent to an upstream circuit protection. In the event of a short circuit, the active circuit is configured to be in circuit so the current is not limited by the passive circuit, and the upstream protective circuit is allowed to operate to interrupt the short circuit current.