GE Multilin 850 Feeder Protection Relay

Overview

The GE Multilin 850 is a feeder protection and bay control relay from the Multilin 8 Series platform, designed by GE for the management, protection and control of distribution feeders. It provides primary or backup protection for underground and overhead medium voltage feeders in industrial facilities and distribution utilities, and it combines overcurrent, directional, voltage and frequency protection with programmable logic, high-density I/O and detailed asset monitoring in a single draw-out device. GE built the platform around reliability: every unit goes through electrical stress screening, the boards carry harsh-environment conformal coating as standard, and the design eliminates electrolytic capacitors, which are a common life-limiting component in electronic relays.

Seven Star LLC supplies the GE Multilin 850 to switchgear builders, utilities, refineries and process plants across Oman and the GCC. Our Muscat engineering team checks each order code against the published GE ordering table, confirms the CT secondary rating, power supply, protection and communications options for the specific panel, and supports retrofit projects where an older feeder relay is being replaced with the GE Multilin 850.

Protection Principle

The relay measures three-phase currents, ground or sensitive ground current and phase voltages, then derives fundamental phasors, RMS values, sequence components and harmonics up to the 25th. Time overcurrent elements for phase, neutral and ground follow IEEE, ANSI, IEC, IAC, I2t, I4t, definite time or user FlexCurve characteristics, so the GE Multilin 850 can be graded with upstream incomers and downstream fuses or motor starters. Instantaneous overcurrent elements clear heavy faults quickly, while directional elements with quadrature polarising separate forward and reverse faults on ring or parallel feeders.

Voltage and frequency elements extend the scheme beyond simple overcurrent. Undervoltage, overvoltage, negative sequence voltage, underfrequency, overfrequency and frequency rate of change are available in the voltage option, together with synchrocheck and directional power. GE describes intelligent load shedding as a key use: when a plant partially islands and the remaining generation cannot carry the load, underfrequency and rate-of-change elements shed selected feeders before the frequency collapses. Auto-reclose with up to four shots, cold load pickup and breaker failure complete the feeder logic.

Engineering Design of the GE Multilin 850

Mechanically the GE Multilin 850 uses a custom extruded aluminium chassis with a low-insertion-force draw-out case, so the relay can be withdrawn for testing without disturbing the panel wiring. The rear of the unit carries the CT and VT terminals, digital input and output cards, the power supply, the standard serial and RJ45 Ethernet module and the optional fibre communications module. The power supply is field swappable, which shortens repair time if a supply is ever damaged by a surge on the station battery.

The front face carries a large full colour graphic control panel with soft-key navigation, fourteen LED indicators, three LED pushbuttons and a front USB port. Ten of the LEDs are user programmable in red, green or orange and can be latched or self-reset. A patented environmental monitoring function records temperature, humidity, voltage surges and vibration seen by the relay, giving maintenance teams evidence about the conditions inside the switchroom. Cyber security features include password complexity, RADIUS authentication and role-based access control to help users meet NERC CIP and NISTIR 7628 requirements.

Key Features

The main features of the GE Multilin 850 that matter to protection engineers are summarised below.

• Phase, neutral, ground and sensitive ground time and instantaneous overcurrent protection with a wide choice of standard and user-defined curves.
• Directional phase, neutral and ground overcurrent, load encroachment and broken conductor detection in the advanced current protection option.
• Undervoltage, overvoltage, frequency, rate of change of frequency, synchrocheck and directional power elements for load shedding and interconnection duty.
• Four-shot auto-reclose, cold load pickup, breaker failure and automatic bus transfer logic built into the relay rather than wired externally.
• FlexLogic programmable logic in the GE Multilin 850, digital counters and a configurable trip bus for custom interlocking schemes.
• Transient recorder with selectable sampling up to 128 samples per cycle and an event recorder with one microsecond time tagging.
• Embedded IEC 61850, PRP redundancy, DNP 3.0, IEC 60870-5-103 and 104, and Modbus protocols with two independent IP addresses.
• Draw-out construction, field swappable supply, IP54 front rating and harsh conformal coating for long service life in difficult switchrooms.

Industrial Applications

For the GE Multilin 850, GE lists oil and gas, petrochemical and refinery feeders, mining and metals, and distribution utilities as the core applications. In Oman that maps directly onto medium voltage switchboards at gas processing plants, refinery and petrochemical complexes in Sohar and Duqm, desalination plants, mining sites and utility primary substations. On a main-tie-main switchboard the GE Multilin 850 can handle incomer and tie protection while executing a high-speed transfer, and on radial or looped distribution circuits the auto-reclose scheme helps restore supply after transient overhead line faults. Engineers comparing feeder relays often review the SEL-751 feeder protection relay and the Siemens SIPROTEC 7SJ85 alongside the 850.

Seven Star LLC supports these projects with model selection and sourcing support from Muscat. For plants that also run GE turbine control systems we can source related spares such as the GE IS200EPSMG1A exciter power supply module, helping maintenance teams consolidate GE purchasing for power generation and distribution assets through one supplier in Oman and the GCC.

Technical Specifications

The table below summarises key GE Multilin 850 data taken from the GE brochure GEA-12715B. Always confirm the final order code with the current GE documentation.

How to Order

To order the GE Multilin 850, send Seven Star LLC your formal RFQ with the full order code or the protection, power supply and communications options you need. Our instrumentation and power division in Muscat will confirm the configuration, coordinate delivery to sites in 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 850 variant for your feeder, incomer or bus transfer scheme.