ABB RET650 Applications Manual page 316

Section 16
Station communication
310
IEC06000537 V1 EN-US
Figure 110: Example of a station configuration with separated process bus and
station bus
The IED can get analog values simultaneously from a classical CT or VT and from
a Merging Unit, like in this example:
The merging units (MU) are called so because they can gather analog values from
one or more measuring transformers, sample the data and send the data over
process bus to other clients (or subscribers) in the system. Some merging units are
able to get data from classical measuring transformers, others from non-
conventional measuring transducers and yet others can pick up data from both
types. The electronic part of a non-conventional measuring transducer (like a
Rogowski coil or a capacitive divider) can represent a MU by itself as long as it
can send sampled data over process bus.
1MRK 504 169-UEN A
Transformer protection RET650 2.2 IEC
Application manual