Line Differential Protection (Multi Ends)
The 7SD52/53 relay provides full scheme differential protection and incorporates all functions usually required for the protection of power lines. It is designed for all power and distribution levels and protects lines with two up to six line ends. The relay is designed to provide high-speed and phase-selective fault clearance. The relay uses fiber-optic cables or digital communication networks to exchange telegrams and includes special features for the use in multiplexed communication networks. Also pilot wires connections can be used with an external converter. This contributes toward improved reliability and availability of the electrical power system. The relay is suitable for single and three-phase tripping applications for two up to six line ends.
Also, transformers and compensation coils within the differential protection zone are protected as are serial and parallel-compensated lines and cables. The relays may be employed with any type of system grounding. The relay also provides a full-scheme and non-switched distance protection as an optional main 2 protection. Several teleprotection schemes ensure maximum selectivity and high-speed tripping time. The units measure the delay time in the communication networks and adaptively match their measurements accordingly. A special GPS-option allows the use of the relays in communication networks, where the delay time in the transmit and receive path may be quite different.
The 7SD52/53 has the following features:
2 full-scheme main protections in one unit (differential and distance protection)
High-speed tripping 10 – 15 ms
The serial protection interfaces (R2R interfaces) of the relays can flexibly be adapted to the requirements of all communication media available.
If the communication method is changed, fl exible retrofitting of communication modules to the existing confi guration is possible.
Tolerates loss of one data connection in a ring topology (routing in 120 ms). The differential protection scheme is fully available in a chain topology.
Browser-based commissioning tool.
Fault locator for one and two terminal measurement for high accuracy on long lines with high load and high fault resistance.
Capacitive charge current compensation increases the sensitivity of the differential protection on cables and long lines.
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
Differential protection with phasesegregated measurement (87L, 87T)
Restricted ground-fault protection (87N) if a transformer is within the protection zone
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)
Ground-fault detection in isolated and resonant-grounded networks
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)
Commands for control of circuit-breakers (isolators)
Self-supervision of relay and protection data (R2R) communication
Trip circuit supervision (74TC)
Oscillographic fault recording
Event logging/fault logging
User-friendly local operation
PC front port for relay setting
Function keys and 14 LEDs f. local alarm
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