High sensitivity High stability for through faults Operating current set using 7 position plug bridge Optional 1A or 5A CT input Tuned to 50Hz or 60Hz 25ms operation at 5x setting Hand reset mechanical flag 2 heavy duty N/O trip contacts Rugged attracted armature sensing elements Use 3 independent units for 3 phase applications Size 2M draw out case Application The 2C73 relay provides high speed differential protection for various items of power system plant including generators, busbars, motors & the individual windings of power transformers. It is also suitable for restricted earth fault protection pplications. a When circulating current protection schemes are subjected to sudden & often asymmetrical growth in system currents due to through faults, the line current transformers can quickly reach saturation. In this condition, variation in transformer magnetizing characteristics can cause large ratio errors with a consequent circuit imbalance & false tripping of the protective elay scheme. r In order to ensure protection stability, a high impedance differential relay set to operate at a slightly higher voltage than that developed in the worst case of the above condition for a through fault current may be used. On a balanced earth fault system for example, this is when one CT of a group is saturated while the others remain unaffected. The saturated CT presents a low impedance path in parallel with the relay, which effectively limits the voltage applied to avoid operation. On internal faults however, this limitation does not exist & voltages of twice the relays ick up settings are easily reached. p The 2C73 relay is a single phase device built in a compact size 2M draw out case suitable for rack and flush mounting. Where 3 phase monitoring is required, 3 single phase units should be employed.
