Transformer differential protection

The specific application can be chosen by parameterization. In this way an optimal adaptation of the relay to the protected object can be achieved.

In addition to the differential function, a backup overcurrent protection for 1 winding/ star point is integrated in the relay. Optionally, a low or high-impedance restricted earth-fault protection, a negative-sequence protection and a breaker failure protection can be used. 7UT613 features 4 voltage inputs. With this option an overvoltage and undervoltage protection is available as well as frequency protection, reverse / forward power protection, fuse failure monitor and overexcitation protection. With external temperature monitoring boxes (thermo-boxes) temperatures can be measured and monitored in the relay. Therefore, complete thermal monitoring of a transformer is possible, e.g. hot-spot calculation of the oil temperature.

7UT613 features full coverage of applications without external relays by the option of multiple protection functions e.g. overcurrent protection is available for each winding or measurement location of a transformer. Other functions are available twice: ground-fault differential protection, breaker failure protection and overload protection. Furthermore, up to 12 user-defined (flxible) protection functions may be activated by the customer with the choice of measured voltages, currents, power and frequency as input variables. The relays provide easy-to-use local control and automation functions.

The integrated programmable logic (CFC) allows the users to implement their own functions, e.g. for the automation of switchgear (interlocking). User-defined messages can be generated as well. The flexible communication interfaces are open for modem communication architectures with control system.

Hardware

• 12 current transformers, 1 IEE
• 4 voltage transformers
• 5 binary inputs
• 8 binary outputs
• Text display
• Surface-mounting or flush-mounting housing

Communication interfaces

• System port 
  – IEC 61850
  

  – IEC 60870-5-103 
  

  – PROFIBUS-DP 
  – DNP 3.0

  – MODBUS RTU

• Service port

  – DIGSI 4

  – Modem

  – Thermobox

• Front port

  – DIGSI 4

• Time synchronization via IRIG B, DCF77 or system interface

Function overview

• Differential protection for 2- up to 3-winding transformers (3-/1-phase)

• Differential protection for motors and generators

• Differential protection for short 2 up to 3 terminal lines

• Differential protection for busbars up to 9 feeders (phase-segregated or with summation CT)

Protection functions

• Differential protection with phase-segregated measurement

• Sensitive measuring for low-fault currents

• Fast tripping for high-fault currents

• Restraint against inrush of transformer

• Phase-/earth overcurrent protection

• Overload protection with or without temperature measurement

• Negative-sequence protection

• Breaker failure protection

• Low-or high-impedance restricted earth fault (REF)

• Voltage protection functions

Control functions

• Commands for control of c.b. and isolators

• Control via keyboard, binary inputs, DIGSI 4 or SCADA system

• User-defined logic with CFC

Monitoring functions

• Self-supervision of the relay

• Trip circuit supervision

• Oscillographic fault recording

• Permanent differential and restraint current measurement, extensive scope of operational values