Siemens 7SK81 Siprotec Compact Motor Protection Relays

The SIPROTEC Compact 7SK81 motor protection relay 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:Highlights-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 AThe 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.Highlights-Inputs for Low power CTs and VTs according to 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

Control functions/programmable logic

• Commands for the ctrl. of CB, disconnect switches (isolators/isolating switches)
• Control through keyboard, binary inputs, DIGSI 4 or SCADA system
• User-defined PLC logic with CFC (e.g. interlocking)

Monitoring functions

• Operational measured values V, I, f
• Energy metering valuesWp,Wq
• Circuit-breaker wear monitoring Minimum and maximum values
• Trip circuit supervision
• Fast measuring voltage failure

 7SK81 Motor Protection Relay Features

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.

Hardware

• 4 current inputs
• 0/3 voltage inputs
• 3/7 binary inputs (thresholds configurable using software)
• 5/8 binary outputs (2 changeover)
• 0/5 RTD inputs
• 1 life contact
• Pluggable voltage terminals.

Perfectly suited for protection in distribution systems and industry, with minimal space requirement. SIPROTEC Compact devices provide a comprehensive range of functions in a surprisingly compact and space-saving housing. Whether as main or as backup protection, a single SIPROTEC Compact device provides protection functionality for every conceivable fault. And it can do even more – it supports the control, automation, and monitoring functions in the substation.