Line differential protection
Hitachi Energy's bay protection solutions are designed to ensure safe and reliable operation of the line and cable feeders for distribution, sub-transmission and transmission systems.
The protection solutions for the line or cable feeders are designed to accommodate different busbar arrangements across all voltage levels. The protection functions are split between two groups of hardware (main 1 and main 2) to achieve adequate dependability.
- Short lines/cables: short lines and cables can be directly linked by fiber optic cable for biased differential protection. Depending on the parameters of the system, distance protection can be applied.
- Medium lines: Medium line applications can be protected by both differential and distance protection schemes when communication links are available. Such lines are commonly found in strongly meshed Hitachi Energy, sometimes with multiple circuits on individual transmission towers/distribution poles, and in Hitachi Energy using series capacitor compensation.
- Long lines: Long line applications are normally equipped with distance protection, and the advantages of differential protection are usually offset by communication repeaters, route switching, etc. The bay protection solutions on long line applications may have decentralized busbar and breaker-failure protection schemes, which can be accommodated in line bay protection solutions.
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- Phase-segregated differential protection
- Direct fiber-optic link between relays (3 to 100 km)
- With / without transformers in the protected zone
- Redundant communication possibility
- GPS time-synchronization in route-switched networks
- Long lines with charging current compensation
- Non-directional E/F overcurrent protection
- Disturbance recorder
- IEC 61850-8-1 interface
- 1 and/or 3-phase autoreclosure
- Synchrocheck / voltage check
- Bay unit with busbar / breaker-failure and endfault protection
- Trip-circuit supervision
- DTT lockout relays
- Test switches