{"product_id":"abb-rex521-overcurrent-and-earth-fault-protection-relay","title":"ABB REX521 Overcurrent and Earth-Fault Protection Relay","description":"\u003ch3\u003e\u003cstrong\u003eProduct Overview\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eThe\u003cspan\u003e \u003c\/span\u003e\u003cstrong\u003eREX521\u003c\/strong\u003e\u003cspan\u003e \u003c\/span\u003eis a high-performance numerical feeder protection relay engineered for the comprehensive protection, control, and monitoring of medium-voltage distribution networks. Designed by ABB, the\u003cspan\u003e \u003c\/span\u003e\u003cstrong\u003eREX521\u003c\/strong\u003e\u003cspan\u003e \u003c\/span\u003eintegrates advanced microprocessor technology to provide rapid fault detection and isolation, effectively safeguarding transformers, motors, and distribution feeders. Its modular hardware architecture and flexible software configuration allow it to adapt to diverse utility and industrial power system requirements. By combining multi-function protection logic with real-time measurement and disturbance recording, the\u003cspan\u003e \u003c\/span\u003e\u003cstrong\u003eREX521\u003c\/strong\u003e\u003cspan\u003e \u003c\/span\u003eensures high system integrity and minimizes operational downtime in critical infrastructure.\u003c\/p\u003e\n\u003ch3\u003e\u003cstrong\u003eDetailed Technical Specifications\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul class=\"list-paddingleft-2\"\u003e\n\u003cli\u003e\n\u003cp\u003e\u003cstrong\u003eManufacturer\u003c\/strong\u003e: ABB\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003e\u003cstrong\u003eModel Designation\u003c\/strong\u003e: REX521\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003e\u003cstrong\u003eDevice Type\u003c\/strong\u003e: Numerical Feeder Protection Relay\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003e\u003cstrong\u003eProtection Logic\u003c\/strong\u003e: Non-directional\/directional overcurrent, earth-fault, thermal overload, and phase imbalance protection\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003e\u003cstrong\u003eRated Current Input\u003c\/strong\u003e: 1 A or 5 A (Selectable via hardware\/software)\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003e\u003cstrong\u003eRated Voltage Input\u003c\/strong\u003e: Standard 100 V \/ 110 V AC\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003e\u003cstrong\u003eNominal Frequency\u003c\/strong\u003e: 50 \/ 60 Hz\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003e\u003cstrong\u003eAuxiliary Power Supply\u003c\/strong\u003e: 24–250 V DC or 48–240 V AC (Wide-range universal input)\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003e\u003cstrong\u003eDigital I\/O\u003c\/strong\u003e: Multiple programmable binary inputs and outputs for interlocking and signaling\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003e\u003cstrong\u003eCommunication Protocols\u003c\/strong\u003e: Modbus RTU\/TCP, IEC 60870-5-103, and SPA bus\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003e\u003cstrong\u003eMonitoring \u0026amp; Recording\u003c\/strong\u003e: Integrated disturbance recorder and comprehensive event logs (up to 200 events)\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003e\u003cstrong\u003eInterface\u003c\/strong\u003e: Front-panel LCD display with dedicated navigation push buttons\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003e\u003cstrong\u003eOperating Temperature\u003c\/strong\u003e: -25°C to +70°C\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003e\u003cstrong\u003eDimensions (WxHxD)\u003c\/strong\u003e: 160 mm x 180 mm x 200 mm\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003e\u003cstrong\u003eWeight\u003c\/strong\u003e: 2.5 kg\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003e\u003cstrong\u003eMounting Configuration\u003c\/strong\u003e: Flush panel-mounted unit\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003e\u003cstrong\u003eIngress Protection\u003c\/strong\u003e: IP20 (Rear), Front panel varies by installation (up to IP54 with protective cover)\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003e\u003cstrong\u003eCompliance\u003c\/strong\u003e: IEC 60255 series for protection relays\u003c\/p\u003e\n\u003c\/li\u003e\n\u003c\/ul\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_695a7407-6fca-452a-9220-b6943b3e28fd.jpg?v=1773200427","url":"https:\/\/www.spareoil.com\/products\/abb-rex521-overcurrent-and-earth-fault-protection-relay","provider":"SpareOil Automation","version":"1.0","type":"link"}