| 摘要 |
A protection and control system incorporates status acquisition apparatus (100) 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 an conversion circuit (101) which converts an input voltage to a pulse width modulated signal and a comparison circuit (103) 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 minimise 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. <IMAGE> |
