Protection of mixed overhead-underground lines

ARTECHE’s SDO MU CFD is a Merging Unit that is installed at the primary substation at the beginning or the end of a mixed overhead-underground line.

The SDO MU CFD is connected to the passive SDO FCT-s (Flexible Current Transformers) that are located at the remote overhead-underground transition points by means of a dedicated, standard Single Mode Fiber Optics pair (for instance, a standard f.o. pair from the OPGW of the line). The SDO MU CFD gets the optically measured signals from the FCTs and processes them according to a line differential (87L) or ground current (50G) algorithm.

The output of the system can be either an auto-reclose block (79) signal (a digital output) that is connected to the protection IED or the measured current that is sent as Sampled Values that are processed by the algorithms of an external protection IED.

One SDO MU CFD can be connected to up to 3 overhead-underground transitions (with the 50G option).

Transition points as far as 20km are not a problem, ARTECHE’s SDO MU CFD can monitor them without any need to install any power supply at the remote transition point.

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