


Applicable Scope:This FO Line Diff Relay is designed for 132kV and below non-grounded/low-resistance grounded systems. It provides primary (differential) and backup (overcurrent/zero-sequence) protection with integrated monitoring. Supports switchgear or panel mounting, using dedicated/multiplexed fiber channels with 2048kbps E1 interface for substation and distribution applications.
Product functions(ANSI):87L | 50/51 | 51 | 50N/51N | 51N | 81U | 49 | 79 | 60 | 60 | 60 | 60/51 | 94 | 21
Communication functions:Supported Protocols:IEC 60870-5-103 (over Ethernet) | MODBUS RTU (via RS-485) | IEC 61850 (Ed.2 or Ed.1, as applicable)
Interfaces:2× Ethernet Ports (IEEE 802.3 compliant, 10/100 Mbps) | 2× RS-485 Ports (ANSI/TIA-485-A standard, galvanically isolated)
Other functions : Support time synchronization via communication message, SNTP (Simple Network Time Protocol) time synchronization, and IRIG-B time synchronization. Support the dot matrix printing function with serial port communication. Support the fault recording function
FO Line Differential Relay Introduction
This FO Line Diff Relay is suitable for non-effectively grounded or low-resistance grounded systems with voltage levels up to 132kV. It provides primary protection (optical fiber pilot differential) and backup protection (overcurrent, zero-sequence, etc.) for transmission lines and feeders, while integrating measurement and control functions.
The FO Line Diff Relay supports decentralized installation in switchgear cabinets or centralized panel mounting. It uses dedicated optical fiber or multiplexed channels as pilot communication media and is equipped with a 2048kbps E1 interface. Suitable for substations, distribution networks, and similar applications, it ensures selective protection while meeting remote monitoring requirements.
FO Line Differential Relay Protection Functions(ANSI)
1.Fiber-Optic Line Differential Protection (ANSI 87L)
2.Three-Stage Phase Overcurrent Protection (ANSI 50/51)
3.Inverse-Time Phase Overcurrent Protection (ANSI 51)
4.Two-Stage Zero-Sequence Overcurrent Protection (ANSI 50N/51N)
5.Inverse-Time Zero-Sequence Overcurrent Protection (ANSI 51N)
6.Underfrequency Load Shedding (ANSI 81U)
7.Overload Alarm (ANSI 49)
8.Three-Phase Single-Shot Reclosing (ANSI 79)
9.Bus PT Broken Wire Alarm (ANSI 60)
10.Line PT Broken Wire Alarm (ANSI 60)
11.CT Broken Wire Alarm (ANSI 60)
12.PT Broken Wire Overcurrent (ANSI 60/51)
13.Independent Tripping Circuit (ANSI 94)
14.Fault Recording (ANSI 21)
FO Line Differential Relay Protection Working Principle
1.The GWZC-9913 FO Line Diff Relay incorporates three key components:
①.power frequency variation current differential element,
②.phase current differential element,
③.zero-sequence current differential element.
All three elements can implement phase-segregated differential logic.
2.Fiber Optic Channel
Dedicated fiber optic channels shall be prioritized when the fiber core quantity and transmission distance permit. When power requirements cannot be met, multiplexed fiber optic channels may be adopted.
2048kbit/s dedicated fiber optic channel
2048kbit/s multiplexed fiber optic channel