Siemens SIPROTEC 5 7SJ81 Overcurrent & Feeder Protection Relay
The Siemens SIPROTEC 5 7SJ81 is a high-performance Overcurrent and Feeder Protection Relay designed for reliable protection of medium and high-voltage systems. It supports low-power current and voltage transformers, making it ideal for a wide range of primary current ratings from 20 A to 2500 A. Built with advanced SIPROTEC 5 technology, it ensures flexible configuration, accurate fault detection, and long-term system reliability
Technical Specifications
Main Function: Overcurrent and feeder protection (including motor and transformer backup protection)
Inputs:
4x Low-Power Current Transformer (LPCT) inputs
3x optional Low-Power Voltage Transformer (LPVT) inputs
Supported CT ratios:
100 A/225 mV → 20–200 A
300 A/225 mV → 60–630 A
600 A/225 mV → 120–1250 A
1250 A/225 mV → 250–2500 A
Highlights:
Programmable logic with CFC
6-line display & up to 9 function keys
Integrated Ethernet ports with RSTP, PRP, HSR redundancy
IEC 61850 GOOSE communication
SNTP time synchronization
USB front port, removable terminals, conformal coating
Monitoring:
V, I, frequency
Energy metering (Wp, Wg)
CB wear, fuse failure, and trip circuit supervision
8 oscillographic fault records
Applications:
Line and feeder protection in MV/HV networks
Motor and transformer backup protection
Industrial and utility substations
Inputs:
4x Low-Power Current Transformer (LPCT) inputs
3x optional Low-Power Voltage Transformer (LPVT) inputs
Supported CT ratios:
100 A/225 mV → 20–200 A
300 A/225 mV → 60–630 A
600 A/225 mV → 120–1250 A
1250 A/225 mV → 250–2500 A
Highlights:
Programmable logic with CFC
6-line display & up to 9 function keys
Integrated Ethernet ports with RSTP, PRP, HSR redundancy
IEC 61850 GOOSE communication
SNTP time synchronization
USB front port, removable terminals, conformal coating
Monitoring:
V, I, frequency
Energy metering (Wp, Wg)
CB wear, fuse failure, and trip circuit supervision
8 oscillographic fault records
Applications:
Line and feeder protection in MV/HV networks
Motor and transformer backup protection
Industrial and utility substations
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