communication modems. This clock can also be a GPS clock but the
telecommunication network synchronization is totally separate from the line
differential protection IED's internal clock synchronization.
2.2 Telecommunication network types
GUID-3AA2C8C6-62B7-42E4-AD80-0479BAFF21C6 v1
There are two main types of telecommunication networks used by electric power
utilities: Plesiochronous Digital Hierarchy (PDH) networks and Synchronous
Digital Hierarchy (SDH) networks (see Figure 2). These networks are mostly
owned by the utilities, but it is also possible to lease communication links from
external companies.
PDH networks are used with 64 kbit/s communication. Proper synchronization of
PDH networks must be available so that hey can be used with protection
applications. SDH networks are used with 2 Mbit/s communication.
SDH networks ≥ 2 Mbit/s
PDH networks ≤ 2 Mbit/s
ATM/IP networks ≥ 622 Mbit/s
Other networks ≥ X Gbit/s
PDH = Plesiochronous Digital Hierarchy
SDH = Synchronous Digital Hierarchy
IEC07000240-1-en.vsdx
PDH/SDH networks are most commonly
used for utility communication
IED
IEC07000240 V1 EN-US
Figure 2: Telecommunication networks for electric power utilities
2.3 Telecommunication networks with symmetric or
fixed routes
GUID-36D8D02D-E63A-4DFC-83C0-1C37708390AD v1
It is possible to use networks with fixed routes where symmetric time delay is
applied, or networks with fixed route switching where both directions have a
symmetric time delay even after route switching has been performed. In these types
Section 2 1MRK 505 382-UEN B
Telecommunication networks and line differential protection
14 Communication set-up 670/650 series 2.2
Application Guide
To Next Page
Loading...
