Transformer differential protection
SIPROTEC 7UT612
The SIPROTEC 7UT612 differential protection relay are used for fast and selective fault clearing of short-circuits in transformers of all voltage levels and also in rotating electric machines like motors and generators, for short lines and busbars. The protection relay can be parameterized for use with threephase and single-phase transformers.
Features
The specific application can be chosen by parameterization. In this way an optimal adaption 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. 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. 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.
The protection relay can be parameterized for use with three-phase and single-phase transformers. In addition to this, a thermal replica is integrated for the supervision of the ohmic losses in the plant.
Hardware
7 current transformers, 1 IEE
3 binary inputs
4 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
Functions
Function overview
Differential protection for two-winding transformers (3-/1-phase)
Differential protection for motors and generators
Differential protection for short lines
Differential protection for busbars up to 7 feeders (phase-segregated or with summation CT)
Protection functions
Differential protection with phase-segregated measurement
Sensitive measuring stage for low-fault currents
Fast tripping for high-fault currents
Restraint against inrush of the transformer
Phase/ground-overcurrent protection
Overload protection with or without temperature measurement
Negative-sequence protection
Breaker failure protection
Low-or high-impedance restricted earth fault (REF)
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
