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New relays put intelligence into the circuit protection chain

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A new range of protection relays from Merlin Gerin, a brand of Schneider Electric, deliver high performance and reliable protection, yet are simple to specify and easy to fit. The new Sepam range relays are the intelligent link in the circuit protection chain for high and medium voltage applications within substations, and are used to protect underground cables, overhead lines, busbars, transformers, motors and even generators.

All power protection arrangements consist of three essential components: a measurement sensor (either current and/or voltage transformer); the protection relay to analyse signals; and the breaking device equipped with a tripping coil (circuit-breakers or contactors) to isolate the faulty part when required. Of these components, the relay is most critical in ensuring continuity of supply, which is why so much attention has been paid to the design of the new Sepam range.

Effective protection is provided from a number of measured parameters. Thermal protection is based on temperature rise calculations which use predictive data to optimise process control. Directional phase overcurrent protection is provided for ring networks. Directional earth fault protection is suited to all neutral earthing systems. Quick and sensitive protection of transformers, motors and generators is delivered via differential protection with restraint elements.

The Sepam family consists of three models the Series 20, 40 and 80 covering common general applications, demanding applications and total solutions respectively. The design is modular and thereby allows configuration according to specific needs. Commissioning is aided by a simple parameter setting procedure. A clear LCD shows relay status and faults, or the devices can communicate remotely via a communications interface.

The Sepam Series 20 has 10 logic inputs, 8 relay outputs and 8 temperature probe inputs. The Series 40 has a similar specification but has 16 temperature probe inputs
and a logic equations editor. The Series 80 is a powerful device with 42 logic inputs, 23 relay outputs, 16 temperature probe inputs and a removable memory cartridge with parameters and settings for fast commissioning after replacement. All devices have a modbus communications port, with the Series 80 device having two modbus ports for multi-master or where there is a redundancy system.

Diagnostics capabilities include the recording of all electrical values, switchgear status (including sensors and trip circuit as well as mechanical switchgear status), disturbance recording and the Sepam self-diagnosis and watchdog.

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