™
NEW TECHNOLOGIES DRIVE
SUBSTATION AUTOMATION
Vol 5, No 8, October 2000
www.utility-automation.com
New Relay
Technologies Drive
Substation Automation
By Jack McCall
Advancements in communications,
relays and programming technology
are working together to propel
substation automation to new levels.
S
ubstation automation is a catch-all phrase that connotes different objectives and technologies to different companies,
and even to different individuals within a company. Perhaps the simplest definition is that substation automation provides a means for obtaining timely information to assist in making operational decisions. Granted, this doesn’t sound
like automation. The word would imply that after being “automated” the substation should be able to sort things out by
itself. While some of this type of automation does take place, for the most part automation today is really about information. This reality is reinforced by some of the most commonly cited reasons for pursuing substation automation, namely:
• Improved decision making due to better and more timely access to data;
• Faster identification and resolution of faults due to better data access.
Early automation efforts involved installing remote terminal units (RTUs) in substations and making numerous
hardwired connections. To monitor relay and switch status, contact points were connected. For metering, analog transducers were put in place. Automation then took a new turn through the introduction of programmable logic controllers (PLCs) to replace the cumbersome collection of auxiliary relays and hardwired logic necessary to accomplish
the various inter-locks and transfer schemes found in substations. Finally, real communications were introduced as intelligent RTUs allowed a utility’s SCADA system to communicate directly with the various, and awkwardly named, intelligent electronic devices (IEDs) in a substation.
Current State of the Industry
Two distinct but related developments are driving substation automation today. The first involves the increasingly
sophisticated communications technologies being deployed within the substation. The dominant architecture now
being used employs some type of communication processor or port switch as a central hub, to which are connected
various IEDs. Growing in popularity is the use of a Local Area Network (LAN) in the substation to which all IEDs
are connected. This architecture is destined to be the future of substation automation architectures, since it eliminates costly and unnecessary intermediaries in the communications path.
The second development is in the distillation of the various IEDs being employed in a substation. Just a few
years ago, typical IEDs in a substation automation project would include: microprocessor-based protective relays;
microprocessor-based digital panel meters; PLCs; data multiplexers; RTUs; modems; communication port switches; communication processors specific to a given manufacturer’s relays, etc.; sequence-of-event recorders; transient
event recorders; and alarm panels.
This was still quite a bit of equipment to deploy and to get working properly. Combining a variety of functions into
one type of device then became the goal of equipment manufacturers. Over time it appears that utilities have voted
with their wallets that protective relays are the devices that will become the anchors of the automated substation. The
perception that relays are more rugged is one reason. Another reason is that a utility can live without a sequence-ofevents recorder or a meter on every feeder, but the relays are a necessity. Subsequently, the market has responded with
modern protective relays that can perform not only relaying functions, but often include metering, sequence-of-events
recording, transient recording, power quality monitoring, load profiling and custom control logic.
New Technologies
In parallel with these substation automation developments, the seemingly unrelated field of computer science was
rapidly maturing the concept of object-oriented programming (OOP). This programming method looks at the characteristics of a data set and treats it as an object. The programming then involves how the objects interact with each
other. This eliminates the focus on the detailed construction of the logic inter-relating how individual characteristics
interact. For example, it is easier to refer to Jane Doe than it is to refer to a female, age 45, with brown hair, and so
forth. If you have ever drawn a box or an arrow in a presentation graphics package, you have interacted with an
“object” in the classic OOP sense.
Two developments are introducing OOP to substation automation. The first is in the field of communication protocols. UCA 2.0/MMS is an object-oriented communication protocol developed through the cooperation of a wide
cross section of utilities, suppliers and research organizations. By combining the high bandwidth of a LAN with UCA
2.0’s ease of use and its promise of interoperability between various IEDs, UCA 2.0’s advocates promise that utilities
soon will be able to access much more data in a much easier fashion than with previous protocols.
Custom Control Logic
Perhaps a more easily understood use of OOP is found in the world of protective relays, which along with communications, form the cornerstones of the modern substation. One of the most useful features of modern microproces-
RELAY TECHNOLOGIES
Sample LTC Blocking Logic Configured
Using Custom Control Logic Software
To address these concerns, manufacturers are developing exceptionally powerful,
Block Unless Bkr Is Closed
intuitive and easy-to-use software tools that
And Recloser Is Reset
79:Reset Status=0
allow utilities to create, implement and test
Block When Sensitive Fault
custom logic and control
Detectors Pick Up
Fault=0
schemes using objectDrive the <LTC> Contact Output
Block When Sensitive Fault
oriented programming
To Block Any Tap Change
Detectors Pick Up
27P3=0
LTC
techniques.
Block For Phase
Undervoltage
One such tool, Cooper
co7(TB4:1-2)
59P3=0
Power
Systems’ IDEA
Block For Neg
Seq Overvoltage
Workbench, provides users
59Q=0
Note Implications:
with the ability to impleBlock For Zero
Voltage Elements Are Used Here
For LTC Blocking, So May Be Disabled For
Seq Overvoltage
UV Or Ov Feeder Tripping.
ment
custom logic and algo59VO=0
rithms through a drag-anddrop construction technique. Users are able
sor relays and controls is their ability to
to access any of the relay’s internal signals,
execute custom control logic. For many
contact states, analog quantities and comapplications, this eliminates the need for
munications inputs. A set of tools is providseparate programmable logic controllers
(PLCs) and their associated cost, complex- ed to manipulate and combine these signals
ity and wiring. Yet for all of its advantages, in a variety of manners. The resulting logic
may be used to alter the relay’s operation,
contemporary custom logic implementaoperate contacts or initiate communications.
tions are still fraught with drawbacks.
Once constructed, the logic may be testMost significantly:
ed utilizing the program’s Virtual Test Set
feature. The scope of such testing includes
• The equation- or command-based
structure in use today has a relatively not only the created logic, but also its effect
steep learning curve and is non-intu- on the operation and behavior of the relay
itive to decipher when examining the as a whole. This eliminates the need to
physically test a relay with test equipment.
finished product.
• Equation- and command-based logic Additionally, the operation of every element
of the custom logic is observable while
is usually entered as a collection of
examining captured event records.
ASCII setting strings. These are
One added feature in many of these new
prone to human error when transoftware programs is the ability to be downscribed from setting sheets to the
actual relay. Indeed, a frequent com- loaded to the relay. The custom logic is
never reduced to an ASCII string, but rather
plaint of relay engineers is that misis downloaded to the relay as a file separate
takes made in entering custom logic
equations is the most common form from the other settings. This ensures that
once the logic is developed and configured
of setting errors. These errors are
notoriously difficult to troubleshoot. on the relay, it is essentially out of the way
• Most implementations are limited in and cannot be affected by routine setting
changes. The custom logic is tested and
the number of specific logic
elements, such as timers, that may be debugged on a PC, and either downloaded
to the relay in the lab, or sent to the relay
used. There is no recourse once this
technicians as a separate file that requires no
number is exceeded.
manual data entry process into the relay.
• Testing the logic requires users to
have at their disposal a sample of the
relay and a suitable complement of
Example
test equipment.
This technique provides for the imple• Preparing documentation as to what, mentation of exceptionally complex and
and how, the custom logic works is
sophisticated control and adaptive automamandatory to ensure its ability to be tion techniques. As an example, Figure 1
supported in the future.
shows the implementation of some simple
logic designed to block the operation of a
power transformer’s load tap changer
(LTC) for a variety of conditions. The logic
drives an output contact that is wired to the
LTC. Examination of this figure shows a
number of advantages of this new software
technology over conventional equation- or
command-based logic methods.
• The logic implementation is intuitive.
With no further explanation other than
Figure 1, the reader is able to determine
exactly how the logic operates and under
what conditions the LTC’s operation
will be inhibited. The logic is implemented in the exact fashion it is typically
envisioned in the engineer’s mind.
• Notes were embedded in the logic by
the developer to provide helpful explanations or insights to those who may need
to examine the logic later.
• The figure shows the logic state during
playback of a previously recorded event.
The appearance of all elements is dynamic, enabling the user to observe the
behavior of the custom logic in operation. Logic gates appear red when their
output is logical 1 and appear green
when their output is logical 0. Knowing
this, it is easy to determine that the LTC
blocking contact is closed at this point in
time, and the cause is that the reclose
logic is not reset (due to being in the
midst of a reclose sequence).
• The actual state of all the other driving
inputs may be observed by looking at
the values displayed inside the green signal arrows.
Conclusion
The sophistication of current substation
automation technology is a far cry from
that of a few years ago. Advances in substation LANs, advanced communication protocols, and relays that can be re-configured
by the user with simple object-oriented
programming will dramatically increase the
power of automation. ■
Jack McCall is currently Cooper Power Systems’ Director of Protective
Relay and Automated Systems Group located in Franksville, Wis. He
has a master’s degree in electric power engineering from Rensselaer
Polytechnic Institute and a bachelor’s degree in electrical engineering
from Gannon University. He is a member of the IEEE Power Engineering Society and has authored numerous papers. More information
is available at www.cooperpower.com/idea.
Reprinted from the October 2000 edition of UTILITY AUTOMATION
Copyright 2000 by PennWell Corporation