363-206-305
Applications
2-64
Issue 3 June 2000
Teleprotection and Supervisory
Control and Data Acquisition
(SCADA) Communications for Electric
Utilities
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
SCADA applications.
DDM-2000 OC-3, OC-12, and FiberReach systems 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 virtual tributary (VT) path protection switching algorithm and is
provisioned as an unswitched path between any two nodes on the ring.
Figure 2-48 shows that locked DS1s can be used to interconnect adjacent nodes
all the way around SONET rings, thereby permitting access to the DS1 at each
SONET node.
Figure 2-48 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 FiberReach node using an external drop/insert multiplexer, such as the RFL
9001 Intelligent Multiplexer. Figure 2-48 also shows the DDM-2000
interconnecting at the DS1 level with an adjacent RFL 9001 Intelligent Multiplexer,
which 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
communicates 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-connection should the ring be cut. This algorithm
operates much faster than the SONET TR-496 algorithm, thereby minimizing
system outage during a protection switch.
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