Lucent Technologies DDM-2000 OC-3, User & Service Manual

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Applications
2-62 Issue 3 June 2001
Teleprotection and SCADA Applications 2
Electric utilities are facing an unprecedented demand for increased
communications bandwidth to support modern operations and business
applications such as substation automation, computer networking, and video
teleconferencing. Many electric utilities are installing SONET fiber optic
backbones to meet these needs. SONET fiber optic backbones are a valuable
communications resource that can also be used for real time protective relay and
supervisory control and data acquisition (SCADA) applications.
DDM-2000 OC-3, DDM-2000 OC-12, and DDM-2000 FiberReach Multiplexers
can be used in a flexible backbone network among electrical substations and
other important sites. These systems provide an innovative "locked cross-
connection" feature that enhances the ability of SONET rings to transport
protective relay and SCADA communications. The locked cross-connection
feature meets the teleprotection requirements for minimum and stable
transmission delay, minimum system outage during a protection switch, and DS0
level bandwidth management at all ring nodes.
The locked cross-connection feature allows a DS1 to be removed from the
TR-496 compliant VT path protection switching algorithm and provisioned as an
unprotected path between any two nodes on the ring. As shown in Figure 2-43,
locked cross-connection can be used to interconnect adjacent nodes all the way
around SONET rings, thereby permitting access to the DS1 at each SONET node.
Figure 2-43 shows a single DS1 locked between ring nodes, but this can be
extended to an arbitrary number of DS1s within the available SONET bandwidth.
This locked cross-connection feature fixes the ring rotation (and delay) of the DS1
paths on the ring and also permits DS0 grooming of the DS1s at each DDM-2000
or DDM-2000 FiberReach node using an external drop/insert multiplexer, such as
the RFL 9001 Intelligent Multiplexer. Figure 2-43 shows the DDM-2000
interconnecting at the DS1 level with an adjacent RFL 9001 Intelligent Multiplexer
that, in turn, connects on the low-speed side to protective relay and SCADA
equipment. Specially designed channel units in the RFL 9001 Intelligent
Multiplexer detect when a fault occurs on the power line or substation and
communicate at the DS0 level with other substation nodes to isolate the power
grid fault.
In addition to the efficient DS0 grooming capability, the RFL 9001 Intelligent
Multiplexer implements its own protection algorithm that can restore the DS0 level
circuits within the locked cross-connections should the ring be cut. This algorithm
operates much faster than the SONET TR-496 algorithm, thereby minimizing
system outage during a protection switch.