GE Multilin 350 Feeder Protection Relay

Overview

The GE Multilin 350 is a feeder protection relay from the Multilin 3 Series, built to give medium voltage feeders dependable overcurrent protection in a compact, easy-to-configure package. GE uses it for primary circuit protection on medium voltage feeders and for downstream breaker protection in distribution utilities. The basic function set covers phase, neutral and ground time and instantaneous overcurrent for coordination with upstream and downstream devices, and order options add directional elements, voltage and frequency protection, cold load pickup blocking, breaker failure and four-shot auto-reclose. GE emphasises simple engineering: a standard feeder application can be configured in one step with minimal settings.

Seven Star LLC supplies the GE Multilin 350 to switchgear manufacturers, contractors and plant maintenance teams in Oman and the GCC. Many regional switchboards were built with compact feeder relays, and our engineers in Muscat help customers choose the right current input rating, power supply, case style and communication option so that the GE Multilin 350 drops into new panels or retrofit cutouts without surprises.

Protection Principle

The relay measures phase currents, ground or sensitive ground current and, where the voltage option is fitted, phase voltages. Time overcurrent elements use ANSI, IEEE, IEC, IAC or user flex curves so that the GE Multilin 350 can be coordinated with fuses, motor starters and upstream incomers, while instantaneous elements give fast clearance of close-in faults. Negative sequence overcurrent detects unbalanced faults and open phases, and directional phase, neutral and ground elements allow selective tripping on parallel feeders and ring circuits. A cable thermal model protects conductors from overheating under sustained overload.

Feeder control functions are an important part of the scheme. Cold load pickup automatically or manually blocks or raises trip settings when a feeder is re-energised after a long outage, so that the inrush from loads that have lost diversity does not cause a nuisance trip. Breaker failure sends a trip to upstream breakers if the local breaker does not clear the fault. Auto-reclose offers up to four shots, each with its own dead time, and for each shot the relay can block selected overcurrent elements. Zone inter-tripping, flex curves and multiple setting groups support arc flash mitigation strategies.

Engineering Design of the GE Multilin 350

The GE Multilin 350 is a small, side-by-side mountable relay that suits crowded medium voltage panels. In draw-out form the relay withdraws without rewiring, without opening the switchgear door and without disconnecting Ethernet fibre, copper or RJ45 cables. Inputs and outputs comprise ten contact inputs with programmable thresholds, two Form A trip and close outputs with coil monitoring and five Form C output relays. Sixteen logic elements support manual control, interlocking and peer-to-peer tripping, and virtual inputs allow remote commands from SCADA.

The front panel provides a four-line display, twelve LED indicators (programmable LEDs on the draw-out version) and a front USB port. Diagnostics include an event recorder with 256 events, oscillography at 32 samples per cycle, trip and close coil monitoring, IRIG-B time synchronisation and a security audit trail that records setting changes. The relay monitors ambient temperature and alarms on high temperatures, helping users plan maintenance where switchrooms run hot. GE subjects the design to accelerated life testing to verify reliable operation under abnormal conditions.

Key Features

The GE Multilin 350 offers the following capabilities for medium voltage feeder protection.

• Phase, neutral and ground time and instantaneous overcurrent with ANSI, IEEE, IEC, IAC and flex curves.
• Optional directional phase, neutral and ground overcurrent and negative sequence overcurrent.
• Optional undervoltage, overvoltage, negative sequence voltage, underfrequency and overfrequency protection.
• Cable thermal model, cold load pickup, breaker failure and lockout functions.
• Four-shot auto-reclose with independent dead times and per-shot element blocking.
• Ten contact inputs and seven outputs, sixteen logic elements and two setting groups.
• Draw-out or non draw-out case with easy retrofit into existing S1 and S2 cutouts using adapter plates.
• Front USB, rear RS485 and optional copper and fibre Ethernet with IEC 61850, IEC 61850 GOOSE, DNP3.0 and Modbus.

Industrial Applications

The GE Multilin 350 is well suited to outgoing feeders on industrial medium voltage switchboards, distribution utility downstream breakers and ring main feeders, and auxiliary distribution in power plants, water treatment works and oil and gas facilities. In Oman it fits feeder panels in utility secondary substations, district cooling plants, hotels and commercial developments in Muscat, and process plant switchrooms in Sohar and Salalah where compact relays help keep panel widths small. Engineers comparing compact feeder relays often evaluate the Schneider Electric Sepam Series 20 protection relay and the Schneider Electric MiCOM P139 feeder protection relay alongside the 350.

Seven Star LLC supports these projects with model selection and sourcing support from Muscat. For retrofit work where older feeder relays such as the Vamp 257 feeder protection relay are being replaced, we help customers in Oman and the GCC map existing settings and wiring onto the GE Multilin 350 configuration.

Technical Specifications

The GE Multilin 350 specifications below are taken from the GE brochure GEA-12777M; confirm the final order code with current GE documentation.

How to Order

Send your formal RFQ for the GE Multilin 350 to Seven Star LLC with the GE order code, or tell us the CT rating, power supply, protection and communication options you require. Our instrumentation and power division in Muscat will confirm the configuration, coordinate delivery across Oman and the GCC, and share the GE brochure available for download on this page. Contact our engineering team for help selecting the right GE Multilin 350 variant for your feeder panels.