Abstract: A trackside power distribution apparatus includes overlapping feeders. A first signal supply unit has an input adapted to receive power from a first electrical power source and an output for supply of power to a feeder. A first portion of feeder is connected to the output of the first signal supply unit and extends alongside a track to a unit requiring power. A second signal supply unit has an input adapted to receive power from a second electrical power source and an output for supply of power to a feeder. A second portion of feeder is connected to the output of the second signal supply unit and extends alongside the track to the unit requiring power. A selection apparatus is also provided which selects which feeder portion is used to supply power to the unit. The provision of the two feeder portions improves the reliability of the apparatus in the event that one power source fails.

Abstract: A protection and control system incorporates status acquisition apparatus for use in monitoring the status of a device in the protection and control system, such as a protection relay in a high voltage electrical circuit. The status acquisition apparatus comprises a conversion circuit which converts an input voltage to a pulse width modulated signal and a comparison circuit which monitors the pulse width modulated signal to determine the status of the device. The mark-space ratio of the pulse width modulated signal decreases as the input voltage is increased to minimize power dissipation over a range of input voltages. The status acquisition apparatus may form an integral part of a protective switching device, although other applications are envisaged.