The Siemens 7SR2422-2NA11-0BA0 is a Duobias-M multifunctional 2-winding transformer differential relay, purpose-built for protecting power transformers against internal faults. It measures differential current between the primary and secondary windings, tripping on imbalance beyond the slope-characteristic setting. The measuring input is rated 1/5 A, 40-160 V, 50/60 Hz, covering standard CT and VT secondaries for medium-voltage transformer bays. Auxiliary supply is wide-range: 24-250 V DC or 100-230 V AC. The binary input threshold is set at 88 V DC, rated for 110-250 V DC control circuits — meaning it will not pick up on a 24 V DC trip signal, so verify your control voltage before wiring. Communication is dual-protocol: IEC 60870-5-103 and Modbus RTU, user-selectable via setting. The rear RS485 port handles the SCADA link; the front USB port is for local commissioning with the Reydisp software suite.
Case, I/O, and what ships in the box
This variant uses the case with 6 CT inputs, 2 EF/REF CT inputs, 1 VT input, 9 binary inputs, 6 binary outputs, and 16 programmable LEDs. The I/O count is fixed — no expansion modules in this order code. The relay ships with the standard communication interface (USB front port, RS485 rear port) and Protection Function Package B (standard version plus additional functions). No optional extras are needed for basic differential protection — the kit is complete as delivered.