Tripping Circuit Arrangement - ABB REB670 Applications Manual

1MRK 505 337-UUS -
6.1.3.12
Application manual
• the CT switching is made only in software, and CT secondary current circuits do not
include any auxiliary contacts, as shown in figure 62.
• the IED is always supplied with a special zone and phase selective "Open CT
Detection" algorithm, which can instantly block the differential function in case of an
open CT secondary circuits caused by accidents or mistakes.
• internal check zone feature is available
This means that a very cost effective solution can be achieved using REB670, producing
extra savings during scheme engineering, installation, commissioning, service and
maintenance.
The pre-configured binary output contacts, are provided in the IED in order to alarm the
open CT circuit condition. At the same time, one of the LEDs on the local HMI can be
programmed to light up. It shall be noted that the Open CT Circuit alarm can only be
manually reset by one of the three following ways:
1. By using the reset menu on the local HMI
2. By energizing the dedicated binary input called "Reset OCT" via communication
links
3. By energizing the dedicated binary input called "Reset OCT" via logic done in the
internal configuration
For more details about the working principles of the Open CT Detection algorithm, refer
to Technical reference manual.

Tripping circuit arrangement

The contact outputs are of medium duty type. It is possible to use them to directly trip the
individual bay circuit breakers. This solution is suitable for all types of station
arrangements. The internal zone selection logic provides individual bay trip signals in the
internal software and no external relay for this purpose are required. This arrangement
insures correct trip signal distribution to all circuit breakers in case of busbar protection
operation or individual bay breaker failure protection operation. Breaker failure
protection can be internal or external to the IED.
By a parameter setting it is possible to provide self-rest or latched trip output contacts from
the IED. However it shall be noted that the latching is electrical (that is, if dc supply to the
IED is lost the output contacts will reset).
However, sometimes due to a large number of required trip output contacts (that is, single
pole operated circuit breakers and/or main and backup trip coils), a separate trip repeat
relay unit is applied for the tripping of the circuit breakers in the station. In that case the
tripping arrangement can be done in different ways.
Section 6
Differential protection
125