Line Differential Protection
General Information
- Description
The line differential protection is used to protect strictly selective areas at high speed. The simple measuring principle of current comparison requires a communication link between the partner devices.
While in former times, analog measured values used to be transmitted (current balance principle), modern devices use the advantages of digital communication. SIPROTEC4 line differential protection devices can protect system configurations with up to six ends.
Our Portfolio (3)
7SD52
Multi-end differential protection relay for two to six line ends, 4-line backlit display
- Description
- Function overview
Power system configurations need to be adjusted onto changing needs. New challenges, like multi-circuit and multiended overhead lines, embedded generation etc. require alterations of traditional transmission line relaying concepts. Apart from technical issues, the utility has to survive in a competitive environment. The challenge is sustaining system reliability at lower costs.
Dependable fault clearance and quick transmission line restoration contribute significantly to efficiency in power system management. In such economic schemes fit ideally SIPROTEC 7SD5. Fully redundant operating Differential- and Distance relays accommodated in on single IED provide high speed operation of both relays and excellent fault coverage, even of peculiar conditions. Precise distance-to-fault location avoids time consuming line patrolling and reduces the down time of the line to a minimum.
Features:
- The protected differential zone may be easily extended from 2 up to 6 line ends. Complex system configurations receive clearly defined protection zones and maximum fault coverage.The high-speed distance relay operates fully independent from the differential relay. Back-up zones provide remote back-up for upstream and downstream lines and other power system components. Contrary to traditional measurement approaches, the distance-to-fault locator uses measurement quantities from both line terminals. This results in precise readings,even under difficult system conditions, e.g. parallel lines or resistive line faults fed from both line terminals. The readings are available right after fault clearance for quickline clearance and system restoration.
- The high-speed distance relay operates fully independent from the differential relay. Back-up zones provide remote back-up for upstream and downstream lines and other power system components.
- Contrary to traditional measurement approaches, the distance-to-fault locator uses measurement quantities from both line terminals. This results in precise readings, even under difficult system conditions, e.g. parallel lines or resistive line faults fed from both line terminals. The readings are available right after fault clearance for quick line clearance and system restoration.
- The relays provide optical ports for relay-to-relay (R2R). The adjustment to other communication media takes place via media converter. They accept all traditional and modern communication media, i.e. fibers, comms networks and pilot wires. The relays remain unchanged.
- For multi-ended lines the communication links may be operated in open or closed rings. The latter provides communication even if one link is broken.
Protection functions
- Differential protection with phasesegregated measurement (87L, 87T)
- Sensitive measuring stage for high-resistance faults
- Non-switched distance protection with 6 measuring systems (21/21N)
- High resistance ground (earth)-fault protection for single and three-pole tripping (50N/51N/67N)
- Phase-selective intertripping (85)
- Tele (pilot) protection (85/21, 85/67N)
- Weak-infeed protection (27WI)
- Fault locator (FL)
- Power swing detection/tripping (68/68T)
- 3-stage overcurrent protection (50, 50N, 51, 51N)
- STUB bus protection (50 STUB)
- Switch-onto-fault protection (50HS)
- Over/undervoltage protection (59/27)
- Over/underfrequency protection (81O/U)
- Auto-reclosure (79), Synchro-check (25)
- Breaker failure protection (50BF)
- Overload protection (49)
- Lockout function (86)
Control functions
- Commands for control of circuit-breakers and disconnectors (isolators)
Monitoring functions
- Self-supervision of relay and protection data (R2R) communication
- Trip circuit supervision (74TC)
- Measured-value supervision
- Oscillographic fault recording
- Event logging/fault logging
- Switching statistics
Front design
- User-friendly local operation
- PC front port for relay setting
- Function keys and 14 LEDs f. local alarm
Communication interfaces
- 2 serial protection data (R2R) interfaces for ring and chain topology
- Front interface for connecting a PC
- System interface for connection to a control system via various protocols
– IEC 61850 Ethernet
– IEC 60870-5-103
– PROFIBUS-FMS/-DP and DNP 3.0 - Rear-side service/modem interface
- Time synchronization via IRIG-B or DCF77 or system interface
