Siemens SIPROTEC 7SJ81 Overcurrent & Feeder Protection Relay
The SIPROTEC 7SJ81 is an advanced numerical overcurrent and feeder protection relay designed for industrial and utility applications. Equipped with 4xI (4xV) inputs, it provides fast, accurate monitoring, control, and coordinated protection, ensuring system reliability and minimizing downtime
Technical Specifications
Directional and non-directional overcurrent protection
Ground-fault detection for compensated or isolated networks (3I0>, V0>, transient, cosφ, sinφ, admittance, intermittent faults)
Arc-flash protection
Overvoltage & undervoltage protection
Frequency and ROCOF protection
Active/reactive power protection
QU (reactive-undervoltage) protection
Synchro-check
Circuit breaker failure protection
Harmonic detection up to 50th harmonic
Integrated Ethernet RJ45, IEC 61850, IEC 60870-5-103/104, Modbus TCP, DNP3, PROFINET
PRP / HSR redundancy support
Web-based access, RBAC cyber-security, signed firmware
IEEE-1588 time synchronization
Fault recording up to 40 s at 2 kHz
Fully configurable with DIGSI 5
Ground-fault detection for compensated or isolated networks (3I0>, V0>, transient, cosφ, sinφ, admittance, intermittent faults)
Arc-flash protection
Overvoltage & undervoltage protection
Frequency and ROCOF protection
Active/reactive power protection
QU (reactive-undervoltage) protection
Synchro-check
Circuit breaker failure protection
Harmonic detection up to 50th harmonic
Integrated Ethernet RJ45, IEC 61850, IEC 60870-5-103/104, Modbus TCP, DNP3, PROFINET
PRP / HSR redundancy support
Web-based access, RBAC cyber-security, signed firmware
IEEE-1588 time synchronization
Fault recording up to 40 s at 2 kHz
Fully configurable with DIGSI 5
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