ABSTRACT
Solid-state protection devices are normally assembled from functional units which themselves are made up of standardized modules. In the case of large protection systems with a number of protection functions, the outputs of the various functions are grouped and assigned to the different tripping signals by a tripping logic. The input transformers step down the secondary currents and voltages coming from the main primary system Current transformers and Voltage transformers to a level suitable for processing by the electronic circuits. The supervision and control unit enables the power supply unit to start-up after an interruption of the battery supply and also limits the output current in the event of a short-circuit in the electronic modules. Generally the power supply units also include some form of energy reservoir to maintain the supply to the protection during voltage dips on the battery supply.
