{"product_id":"st400s-series-microprocessor-based-line-protection-relay-protection-metering-communication","title":"ST400S Series Microprocessor-Based Line Protection Relay | Protection, Metering \u0026 Communication","description":"\u003cp\u003eThe ST400S Series is a microprocessor-based line protection relay designed for low-voltage applications up to AC 660V at rated frequencies of 50\/60Hz. It integrates protection, measurement, control, management, and communication functions into a single intelligent device — the ideal choice for smart power distribution systems.\u003c\/p\u003e\u003cp\u003eThe series features a modular design comprising the main unit and dedicated current transformers. Its compact, space-saving structure allows direct installation in 1\/4-modular and larger withdrawable switchgear cabinets. Widely applied in power generation, petroleum, petrochemical, chemical, metallurgy, coal, paper, and rail transit industries.\u003c\/p\u003e\u003cp\u003eComplies with GB\/T 14598.2-2011 (Measuring Relays and Protection Equipment — Part 1: General Requirements) and GB\/T 14598.26-2015 (Part 26: Electromagnetic Compatibility Requirements).\u003c\/p\u003e\u003ch2\u003eProduct Variants\u003c\/h2\u003e\u003ch3\u003eCommunication Options\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003eST400S1 — No communication\u003c\/li\u003e\n\u003cli\u003eST400S3 — 1× Modbus-RTU (RS485)\u003c\/li\u003e\n\u003cli\u003eST400S5 — 2× Modbus-RTU (RS485)\u003c\/li\u003e\n\u003cli\u003eEVTP — Modbus-TCP (optional)\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003eCT Installation Types\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eIntegrated (L)\u003c\/strong\u003e — 1A \/ 5A CTs, mounted directly on the unit\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSplit (F)\u003c\/strong\u003e — 1A, 5A, 25A, 100A, 160A, 400A CTs, externally mounted; cable lengths: 0.5m, 2m, or 3m\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003eRated Current Range (CT Selection)\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003e1 (0.2–1A)\u003c\/li\u003e\n\u003cli\u003e5 (0.5–5A)\u003c\/li\u003e\n\u003cli\u003e25 (2.5–25A)\u003c\/li\u003e\n\u003cli\u003e100 (10–100A)\u003c\/li\u003e\n\u003cli\u003e160 (16–160A)\u003c\/li\u003e\n\u003cli\u003e400 (40–400A)\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003eOptional Add-on Functions\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003eV1 — Voltage protection, AC 100V\u003c\/li\u003e\n\u003cli\u003eV2 — Voltage protection, AC 400V\u003c\/li\u003e\n\u003cli\u003eV3 — Voltage protection, AC 660V\u003c\/li\u003e\n\u003cli\u003eM1 — 1× 4–20mA analog output\u003c\/li\u003e\n\u003cli\u003eM2 — 2× 4–20mA analog output (uses 5 relay outputs)\u003c\/li\u003e\n\u003cli\u003eL — Residual current protection (requires external ZCT)\u003c\/li\u003e\n\u003cli\u003eR — Fault waveform recording (3-phase current + 3-phase voltage, 6 channels)\u003c\/li\u003e\n\u003cli\u003eT2 — Temperature protection, 2-wire (PT100)\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003eExpansion Modules (Optional)\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003eEDP — 1× Profibus-DP (DPV0\/V1, DB9 interface)\u003c\/li\u003e\n\u003cli\u003eE2DP — 2× Profibus-DP (DPV0\/V1, DB9 interface)\u003c\/li\u003e\n\u003cli\u003eEPN \/ EMTP — 1× RS485 (RJ45 interface)\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003eResidual Current Transformers (for L option)\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003eLZT46-1A — Bore 46mm, range 0.1–1A\u003c\/li\u003e\n\u003cli\u003eLZT80-1A — Bore 80mm, range 0.1–1A\u003c\/li\u003e\n\u003cli\u003eLZT120-1A — Bore 120mm, range 0.1–1A\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003eDisplay Module (Optional)\u003c\/h3\u003e\u003cul\u003e\u003cli\u003eST523L — Multi-line color panel display with WiFi wireless data upload\/download, historical data analysis, and fault management\u003c\/li\u003e\u003c\/ul\u003e\u003ch2\u003eDigital Input Power Supply Options\u003c\/h2\u003e\u003cul\u003e\n\u003cli\u003eBuilt-in DC 24V (internal supply for optically isolated DI)\u003c\/li\u003e\n\u003cli\u003eExternal AC 220V \/ DC 110V \/ DC 220V\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch2\u003eRelay Outputs\u003c\/h2\u003e\u003cul\u003e\n\u003cli\u003eStandard: 6 relay outputs\u003c\/li\u003e\n\u003cli\u003eWith M2 or T2 option: 5 relay outputs\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"Wanlong Electric","offers":[{"title":"Default Title","offer_id":44140644925506,"sku":null,"price":260.0,"currency_code":"USD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0688\/1221\/0242\/files\/ST400S.webp?v=1784270081","url":"https:\/\/wanlongelectric.com\/zh\/products\/st400s-series-microprocessor-based-line-protection-relay-protection-metering-communication","provider":"Wan Long Electric Group Co., Ltd.","version":"1.0","type":"link"}