A Substation Automation Tutorial
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by OPUS Publishing The purpose of this
tutorial is outline the context and steps that a utility engineer, vendor
or consult should take to develop a target architecture for substation
automation. To this end, an overview of the key features is described,
what should be done "keep it simple stupid" and to ensure
interoperability is emphasized, and the need to make sure that the target architecture
is extensible is described. |
Three key features
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The objective of any utility is to develop a substation automation
architecture that provides three key features:
- Interoperability between intelligent electronic devices (IEDs) must
be based on communication specifications defied by open standards;
i.e., no proprietary protocols
- Communication performance must be measurable and meet the
requirements specified in the standards and constraints imposed by the
utility's operating procedure.
- The target architecture should be extensible to ensure a graceful
transition from legacy systems to new technologies.
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The state of standardization and what you should do
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Given the state of standards development within the IEEE and
IEC, it is clear that a stable IED peer-to-peer communication solution has
not yet been specified and properly tested. Therefore, each utility must
develop a test and evaluation laboratory to perform sufficient testing to
have confidence in their target substation automation architectures.
Keep it simple stupid is critical
Utility engineers, vendors and consultants need to consider the
following:
 | The target architecture must be based on stable specification of
communication protocols.
 | A specification that is so esoteric that only a few vendors (and
consultants) understand it is going to be a tough sell to
management that must fund the project. |
| An organization's inability to understand the implementation
details will create, in the mind of most managers, a scenario that
has cost and schedule risks, which will probably derail the
project before it gets started. |
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| When remote access to the substation IEDs uses the utility's Wide
Area Network (WAN), buy-in by the Utility's Information System (IS)
department will be critical to sell the project to management.
| Strongly consider using Internet Protocols, which are well
understood. |
| Be wary of protocols that have been "tailored to address
the unique requirements of substation automation". These
protocols are probably not well understood by the IS department. |
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The key to interoperability
The key to interoperability is the data model that defines the syntax
and semantics of the information to exchanged. For substation automation,
GOMSFE (Generic Object Model for Substation and Feeder Equipment) is
relatively stable and is a good place to start.
Formal specification of GOMSFE objects should use the Abstract Syntax
Notation One (ASN.1) specification to prevent all ambiguities when being
interpreted. Because dial-up communications to the substation is used by
many Utilities, and efficient encoding/decoding scheme should be used.
Packed Encoding Rules (PER) should be strongly considered. |
Extensibility provides smooth migration
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To implement extensibility, the IEDs must interoperate using
a machine independent format. A target architecture must use a
specification that is extensible at three levels:
- Standards making organizations need to write extensions or
companion standards to the parent document.
- Vendors or consortiums of vendors (called User Groups) need to have
the flexibility to add Vendor Extensions to gain a competitive
advantage.
- End users need to have the flexibility to add User Extensions to add
desired functionality for operating procedures.
Utility engineers, vendors, and consultants need to review the
specification that they are considering to make absolutely sure that these
conditions for extensibility are built into the specification. If these
extensibility provisions are not part of the specification; the
specification is inadequate and should not be used. |
The next step is up to you
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Basic principles and concepts are outlined in this tutorial.
We kept it simple so that it can be used as a check list to make sure that
all substation automation issued are addressed. Your next step is to define a target architecture that provides the key
features of interoperability, testability and graceful transition from
legacy systems to new technologies. If you need help send us a request. Be
sure to include your EMAIL address.
Where do you want to go now?
  
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