GE L90 Instruction Manual

Also see for L90: Communications manual Communications guide Instruction manual Instruction manual Instruction manual

Contents

GE Multilin L90 Line Differential Relay 2-72 PRODUCT DESCRIPTION 2.2 PILOT CHANNEL RELAYING22.2PILOT CHANNEL RELAYING 2.2.1 INTER-RELAY COMMUNICATIONSDedicated inter-relay communications may operate over 64 kbps digital channels or dedicated fiber optic channels. Avail-able interfaces include:ï RS422 at 64 kbpsï G.703 at 64 kbpsï Dedicated fiber optics at 64 kbps. The fiber optic options include:ñ 820 nm multi-mode fiber with an LED transmitterñ 1300 nm multi-mode fiber with an LED transmitterñ 1300 nm single-mode fiber with an ELED transmitterñ 1300 nm single-mode fiber with a LASER transmitterñ 1550 nm single-mode fiber with a LASER transmitterñ IEEE C37.94 820 nm multi-mode fiber with an LED transmitterAll fiber optic options use an ST connector. L90 models are available for use on two or three terminal lines. A two terminalline application requires one bidirectional channel. However, in two terminal line applications, it is also possible to use anL90 relay with two bidirectional channels. The second bidirectional channel will provide a redundant backup channel withautomatic switchover if the first channel fails.The L90 current differential relay is designed to function in a Peer to Peer or MasterñMaster architecture. In the Peer toPeer architecture, all relays in the system are identical and perform identical functions in the current differential scheme. Inorder for every relay on the line to be a Peer, each relay must be able to communicate with all of the other relays. If there isa failure in communications among the relays, the relays will revert to a MasterñSlave architecture on a 3-terminal system,with the Master as the relay that has current phasors from all terminals. Using two different operational modes increasesthe dependability of the current differential scheme on a 3-terminal system by reducing reliance on communications.The main difference between a Master and a Slave L90 is that only a Master relay performs the actual current differentialcalculation, and only a Master relay communicates with the relays at all other terminals of the protected line.At least one Master L90 relay must have live communications to all other terminals in the current differential scheme; theother L90 relays on that line may operate as Slave relays. All Master relays in the scheme will be equal, and each will per-form all functions. Each L90 relay in the scheme will determine if it is a Master by comparing the number of terminals on theline to the number of active communication channels.The Slave terminals only communicate with the Master; there is no Slave to Slave communications path. As a result, aSlave L90 relay cannot calculate the differential current. When a Master L90 relay issues a local trip signal, it also sends aDirect Transfer Trip signal to all of the other L90 relays on the protected line.If a Slave L90 relay issues a trip from one of its backup functions, it can send a transfer trip signal to its Master and otherSlave relays if such option is designated. Because a Slave cannot communicate with all the relays in the differentialscheme, the Master will then ìbroadcastî the Direct Transfer Trip signal to all other terminals.The Slave L90 Relay performs the following functions:ï Samples currents and voltagesï Removes DC offset from the current via the mimic algorithmï Creates phaseletsï Calculates sum of squares dataï Transmits current data to all Master L90 relaysï Performs all local relaying functionsï Receives Current Differential DTT and Direct Input signals from all other L90 relaysï Transmits Direct Output signals to all communicating relaysï Sends synchronization information of local clock to all other L90 clocksThe Master L90 Relay performs the following functions:ï Performs all functions of a Slave L90ï Receives current phasor information from all relaysï Performs the Current Differential algorithmï Sends a Current Differential DTT signal to all L90 relays on the protected line