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SIPROTEC 7SJ81 - Overcurrent protection

4xI 0/3xV, directional, low-power CTs

The SIPROTEC Compact 7SJ81 provides 4 low-power current transber bs and optionally 3 low-power voltage transber bs. With the same low-power current transber (LPCT) a wide range of primary rated line currents can be covered. Objects with rated currents in the range of 40 A to 5000 A can be protected when using low-power current transbers.

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

• 100 A/225 mV for a primary operating current range of 40 A … 600 A
• 50 A/22.5 mV for a primary operating current range of 200 A … 3000 A
• 400 A/225 mV for a primary operating current range of 200 A … 2500 A
• 100 A/22.5 mV for a primary operating current range of 400 A … 5000 A

The 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 transber 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 b 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.

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www.siemens.com/7SJ81

• Inputs for Low power CTs and VTs according IEC 61869-6 (berly IEC 60044-7 and IEC 60044-8
• Removable terminal block
• Binary b 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 protocol RSTP for highest availability
• Relay-to-relay communication through Ethernet with IEC 61850 GOOSE
• Millisecond-accurate time synchronization through Ethernet with SNTP.

Overcurrent protection for Low-Power CT and VT Applications– Applications

The SIPROTEC 7SJ81 unit is a numerical protection with low power CT and VT bs. The device perbs control and monitoring functions and therefore provides the user with a cost-effective platb for power system management, that ensures reliable supply of electrical power to the customers. The ergonomic design makes control easy from the relay front panel. A large, easy-to-read display was a key design factor.

Control

The integrated control function permits control of disconnect devices, grounding switches or circuit-breakers through the integrated operator panel, binary bs, DIGSI 4 or the control or automation system (e.g. SICAM).

Programmable logic

The integrated logic characteristics (CFC) allow the user to add own functions for automation of switchgear (e.g. interlocking) or switching sequence. The user can also generate user-defined messages. This functionality can b the base to create extremely flexible transfer schemes.

Operational measured values

Extensive measured values (e.g. I, V), metered values (e.g. Wp,Wq) and limit values (e.g. for voltage, frequency) provide improved system management.

Operational indications

Event logs, trip logs, fault records and statistics documents are stored in the relay to provide the user or operator with all the key data required to operate modern substations.

Line protection

The SIPROTEC 7SJ81 units can be used for line protection of high and medium-voltage networks with grounded, low-resistance grounded, isolated or a compensated neutral point.

Transber protection

The relay provides all the functions for backup protection for transber differential protection. The inrush suppression effectively prevents unwanted trips that can be caused by inrush currents.

Backup protection

SIPROTEC 7SJ81 can be used as a backup protection for a wide range of applications.

Switchgear cubicles for high/medium voltage

All units are designed specifi cally to meet the requirements of medium-voltage applications. In general, no separate measuring instruments (e.g., for current, voltage, frequency, …) or additional control components are necessary in the cubicles.

Control functions/programmable logic

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

Monitoring functions

• Operational measured values V, I, f
• Energy metering values Wp, Wg
• Circuit-breaker wear monitoring
• Minimum and maximum values
• Trip circuit supervision (74TC)
• Fuse failure monitor
• 8 oscillographic fault records

Communication interfaces

• System/service interface
  • IEC 61850
  • IEC 60870-5-103
  • PROFIBUS-DP
  • DNP 3.0
  • MODBUS RTU
  • Ethernet redundancy protocols RSTP, PRP and HSR
• Ethernet interface for DIGSI 4
• USB front interface for DIGSI 4

Hardware

• 4 low-power current transber bs
• 0/3 voltage bs
• 3/7 binary bs (thresholds configurable using software)
• 5/8 binary outputs (2 changeover/Form C contacts)
• 1 life contact
• Pluggable voltage terminals