Input currents are supplied to 3 current transformers: – two measuring phase current (the third current is computed as vector sum of the two others) – one measuring the earth fault zero-sequence current. Phase current rated input can be 1 or 5A (Selectable by movable bridges an relay card) For zero-sequence current taps for 1A and 5A input are provided on relay’s terminal board. Make electric connection in conformity with the diagram reported on relay’s enclosure. Check that input currents are same as reported on the diagram and on the test certificate. The auxiliary power is supplied by a built-in interchangeable module fully isolated an self protected.
The relays fitted with the serial communication option can be connected via a cable bus or (with proper adapters) a fiber optic bus for interfacing with a Personal Computer (type IBM or compatible). All the operations which can be performed locally (for example reading of measured data and changing of relay’s settings) are also possible via the serial communication interface. Furthermore the serial port allows the user to read the demand recording data. The unit has a RS232 / RS485 interface and can be connected either directly to a P.C. via a dedicated cable or to a RS485 serial bus, thus having many relays to exchange data with a single master P.C. using the same physical serial line. A RS485/232 converter is available on request. The communication protocol is MODBUS RTU (only functions 3, 4 and 16 are implemented). Each relay is identified by its programmable address code (NodeAd) and can be called from the P.C. A dedicated communication software (MSCOM) for Windows 95/98/NT4 SP3 (or later) is available. Please refer to the MSCOM instruction manual for more information Microelettric Scientific.
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