ABB REF615 Applications Manual page 195

1MRS756378 D
REF615
Application Manual
Trip-circuit supervision and other trip contacts
It is typical that the trip circuit contains more than one trip contact in parallel, for
example in transformer feeders where the trip of a Buchholz relay is connected in
parallel with the feeder terminal and other relays involved. The constant test current
flow is shown in the following figure. The supervising current cannot detect if one
or all the other contacts connected in parallel are not connected properly.
A070968 V2 EN
Figure 93: Current flow in parallel trip contacts and trip-circuit supervision
In case of parallel trip contacts, the recommended way to do the wiring is that the
TCS test current flows through all wires and joints as shown in the following figure.
Section 7
Supervision functions
189