Motor protection relay for low-power current transformer applications, Width: 1/6 x 19''


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    The SIPROTEC Compact 7SK81 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 rangefrom 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

    The SIPROTEC 7SK81 is a multi-functional motor protection relay. It is designed for protection of asynchronous motors of all sizes. The relays have all the required functions 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.


    • Inputs for low power VTs and CTs 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

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