{"product_id":"abb-rex521-numerical-feeder-protection-relay","title":"ABB REX521 Numerical Feeder Protection Relay","description":"\u003ch2\u003eABB REX521 Overcurrent and Earth-Fault Protection Relay\u003c\/h2\u003e\n\u003cp\u003eConfigured for feeder fault detection and continuous line monitoring in distribution networks, the \u003cstrong\u003eABB REX521\u003c\/strong\u003e (\u003cstrong\u003eREX521\u003c\/strong\u003e Protection Relay) provides direct physical\/electrical execution. The unit processes multi-function overcurrent, earth-fault, thermal overload, and phase imbalance protection algorithms across medium-voltage utility and industrial platforms. Operating across 1 A or 5 A selectable current inputs with a 24-250 VDC or 48-240 VAC auxiliary power supply, the relay executes high-speed fault isolation and event recording.\u003c\/p\u003e\n\u003ch3\u003eHardware Specifications\u003c\/h3\u003e\n\u003cfigure class=\"table\"\u003e\n\u003ctable\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth\u003e\u003cstrong\u003eParameter\u003c\/strong\u003e\u003c\/th\u003e\n\u003cth\u003e\u003cstrong\u003eSpecification\u003c\/strong\u003e\u003c\/th\u003e\n\u003c\/tr\u003e\n\u003c\/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003eModel\u003c\/td\u003e\n\u003ctd\u003eREX521\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eBrand\u003c\/td\u003e\n\u003ctd\u003eABB\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eOrigin\u003c\/td\u003e\n\u003ctd\u003eSweden \/ Finland\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eWeight\u003c\/td\u003e\n\u003ctd\u003e2.5 kg\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eDimensions\u003c\/td\u003e\n\u003ctd\u003e160 mm x 180 mm x 200 mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eOperating Temp\u003c\/td\u003e\n\u003ctd\u003e-25 to +70 deg C\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003ePower Consumption\u003c\/td\u003e\n\u003ctd\u003eUniversal Auxiliary Input: 24-250 VDC or 48-240 VAC\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eProtection Logic\u003c\/td\u003e\n\u003ctd\u003eNon-directional\/directional overcurrent, earth-fault, thermal overload, phase imbalance\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eRated Current Input\u003c\/td\u003e\n\u003ctd\u003e1 A or 5 A (hardware\/software selectable)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eRated Voltage Input\u003c\/td\u003e\n\u003ctd\u003eStandard 100 V \/ 110 VAC\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eNominal Frequency\u003c\/td\u003e\n\u003ctd\u003e50 \/ 60 Hz\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eDigital I\/O\u003c\/td\u003e\n\u003ctd\u003eMultiple programmable binary inputs and outputs\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eField Protocols\u003c\/td\u003e\n\u003ctd\u003eModbus RTU\/TCP, IEC 60870-5-103, SPA bus\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eIngress Protection\u003c\/td\u003e\n\u003ctd\u003eIP20 (Rear), up to IP54 (Front panel with protective cover)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003c\/figure\u003e\n\u003ch3\u003eBackplane Bus Communication Velocity and Deterministic Networks\u003c\/h3\u003e\n\u003cp\u003eIndustrial substation platforms rely on deterministic protocol execution to ensure fast trip execution and reliable telemetry. The ABB REX521 integrates Modbus RTU\/TCP, IEC 60870-5-103, and SPA bus protocol stacks across dedicated serial and Ethernet physical layers. Network deterministic throughput guarantees low protocol latency during fault events, allowing real-time disturbance records and event logs (up to 200 events) to transmit to upper-level SCADA systems without impairing backplane protection logic processing.\u003c\/p\u003e\n\u003ch3\u003eFrequently Asked Questions\u003c\/h3\u003e\n\u003cp\u003eQ: How are current inputs configured on the ABB REX521 hardware? A: CT secondary circuits connect to selectable terminals supporting either 1 A or 5 A nominal rated current inputs via hardware tap or software configuration.\u003c\/p\u003e\n\u003cp\u003eQ: What data recording capabilities are available on the relay during a power system fault? A: The relay includes an integrated disturbance recorder along with non-volatile event logging memory capable of storing up to 200 sequential events.\u003c\/p\u003e\n\u003cp\u003eQ: Does the unit support hot-swapping or online withdrawal during operation?\u003c\/p\u003e\n\u003cp\u003eA: Terminal block connections must be de-energized and current transformer secondaries shorted before removing or replacing the panel-mounted unit to prevent dangerous overvoltages.\u003c\/p\u003e\n\u003ch3\u003eField Installation Guidelines\u003c\/h3\u003e\n\u003col\u003e\n\u003cli\u003eCut out panel dimensions to fit the 160 mm x 180 mm frame and mount the unit flush using standard panel clamps.\u003c\/li\u003e\n\u003cli\u003eVerify that CT secondary circuits are shorted prior to connecting 1 A or 5 A current input wiring to the terminal blocks.\u003c\/li\u003e\n\u003cli\u003eWire auxiliary power supply connections to the universal input terminals accepting 24-250 VDC or 48-240 VAC.\u003c\/li\u003e\n\u003cli\u003eConnect communication lines (Modbus, IEC 60870-5-103, or SPA bus) using shielded twisted-pair cables isolated from high-voltage primary conductors.\u003c\/li\u003e\n\u003cli\u003eConnect the rear protective earthing terminal directly to the main station ground bar using a low-impedance copper strap.\u003c\/li\u003e\n\u003c\/ol\u003e","brand":"ABB","offers":[{"title":"Default Title","offer_id":43026974998618,"sku":"REX521","price":99.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0710\/5957\/0778\/files\/37._92fb51c5-d6e7-4334-903a-79d9d08d5534.jpg?v=1773200427","url":"https:\/\/www.spareoil.com\/products\/abb-rex521-numerical-feeder-protection-relay","provider":"SpareOil Automation","version":"1.0","type":"link"}