The SIPROTEC Compact 7SJ81 provides 4 low-power current transformer inputs and optionally 3 low-power voltage transformer inputs. With the same low-power current transformer (LPCT) a wide range of primary rated line currents can be covered. Objects with rated currents in the range from 20 A to 2500 A can be protected when using low-power current transformers. 

The following low-power current transformer ratios are suitable for the following primary current operating ranges

• 300 A/225 mV for a primary operating current range of 60 A to 630 A

• 600 A/225 mV for a primary operating current range of 120 A to 1250 A

• 1250 A/225 mV for a primary operating current range of 250 A to 2500 A

• 100 A/225 mV for a primary operating current range of 20 A to 200 A

SIPROTEC 7SJ81 is a multi-functional motor protection relay. It is designed for protection of asynchronous motors of all sizes. The relays have all the functionality to be applied as a backup relay to a transformer differential relay. 

The relay provides numerous functions to respond flexibly to the system requirements and to deploy the invested capital economically. Examples for this are: exchangeable interfaces, flexible protection functions and the integrated automation level (CFC). Freely assignable LEDs and a six-line display ensure a unique and clear display of the process states. In combination with up to 9 function keys, the operating personnel can react quickly and safely in any situation. This guarantees a high operational reliability.

Highlights

• Inputs for Low power CTs and VTs according IEC 61869-6 (formerly IEC 60044-7 and IEC 60044-8)

• Removable terminal blocks

• Binary input thresholds settable using DIGSI (3 stages)

• 9 programmable function keys

• 6-line display

• Buffer battery exchangeable from the front

• USB front port

• 2 additional communication ports

• integrated switch for low-cost and redundant optical Ethernet rings

• Ethernet redundancy protocols RSTP, PRP and HSR for highest availability

• Relay-to-relay communication through Ethernet with IEC 61850 GOOSE

• Millisecond-accurate time synchronization through Ethernet with SNTP

The SIPROTEC Compact 7SJ81 relays can be used for line/feeder protection of high and medium-voltage networks with grounded, low-resistance grounded isolated or a compensated neutral point. The relays have all the functionality to be applied as a backup relay to a transformer differential relay. 

The SIPROTEC Compact 7SJ81 offers highest reliability at major functionality by the synergy of reliable algorithms with newly developed hardware. The reliability is proven by the experience in the field of almost 1,000,000 SIPROTEC devices. 
The relay provides numerous functions to respond flexibly to the system requirements and to deploy the invested capital economically. Examples for this are: exchangeable interfaces, flexible protection functions and the integrated automation level (CFC). Freely assignable LEDs and a six-line display ensure a unique and clear display of the process states. In combination with up to 9 function keys, the operating personnel can react quickly and safely in any situation. This guarantees a high operational reliability.