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44 Electrical Line January / February 2021 electricalline.com
Logic Controllers and Communications Processors.
As a result, transmission and distribution substations that
rely heavily on legacy RTUs are ripe for upgrade. Unfortunately
, the task traditionally meant not only replacing the
RTUs, but also disconnecting and reconnecting hundreds of
wires to monitored and controlled devices.
Even medium-sized distribution substations can have 200-
300 I/O points that need to be monitored by RTUs. The larger
transmission substations can have well over 1000, so the
magnitude of an RTU retrofit can be significant. In addition
to the efforts to re-wire, there’s also the need in transmission
to check out each re-wired circuit using skilled personnel in
a costly and time-consuming commissioning process, and
possibly applying for an outage. As a result of these high
costs, utilities have stretched the service life of legacy RTUs
to the breaking point, increasing the chances of disruptive
failure and loss of real-time substation visibility.
In response, leading substation automation manufacturers
have developed retrofit solutions that allow the replacement
of legacy RTUs with modern alternatives without the need
for re-wiring.
One innovative solution from NovaTech allows for the
replacement of legacy RTUs – including D20, Telegy, ACS,
Systems Northwest and Telvent – with adaptor boards in the
place of the legacy I/O. These adapter boards are connected
to the company’s Orion I/O unit through pre-designed wire
harnesses. The adaptor boards are designed so the pre-existing
wire connectors from the legacy system can be removed
and installed while keeping all the wiring intact.
In most cases, the field wiring is not hardwired to the
legacy I/O board. Instead, it is wired through a removable
connector, which can be lifted and reconnected to the adapter
board. The adaptor boards are typically designed to accommodate
all of the connectors for the legacy discrete input, discrete
output, analog input, and combination cards.
In situations where field wiring cannot be removed, a “top
hat” approach can be used. The top hat is a NovaTech board
that is placed on top of the legacy I/O card, connecting to the
I/O signal pins. These pins would normally be connected to the
legacy RTU, but in retrofits is connected to the Orion RTU.
A slight modification of the above approaches is used for
D20 retrofits. The D20 I/O uses four connector styles, two of
which – the Phoenix-style terminal and the DB25-style – can
be removed from the legacy I/O modules. In these retrofits, a
1 RU (rack unit) wide adapter plates is attached to the Orion
I/O module (which is 2 RU), creating an assembly than can
be retrofitted into the same panel space as the 3 RU D20 I/O.
By using the same panel space, retrofits are simplified.
In some cases, minor customization and re-wiring may be
required. Given the wide range of legacy RTUs in use, new
adaptor boards and wire harnesses can be required and
NovaTech has the design and manufacturing capabilities to
produce new boards quickly, when needed.
Tapping Into Advanced RTU Functionality
With a modern RTU like the Orion I/O, one of the primary
benefits of an upgrade is significantly enhanced automation
and visualization functionality. Math and Logic can now be
executed on the RTU to add needed local real-time control in
the substation, including controlling tie breakers, minimizing
circulating VARs, forcing settings group changes, adding
complex interlocking to reclosing schemes and executing
“Distribution Automation” schemes.
All this can be put into the “Smart RTU” without adding
logic to protective relays or adding a separate controller. In
addition, pre-configured math and logic for alarm grouping,
filtering and intelligent blocking can make reported alarms
more meaningful, so that they are reported only when pertinent
. The math and logic style can be tailored to the application
; e.g. “ladder logic” for technicians to troubleshoot interlocking
, higher-level text-based math and logic for engineers
to create embedded routines and “canned” routines for commonly-used
functions.
Utilities can also configure the modern RTU as a “Tile
Alarm Annunciator without adding yet another box. A monitor
can be attached to the RTU (no PC required), and a webpage
served out showing a screen of colored tiles visually
displaying alarm status. Custom pages can be added to further
expand local annunciation including one-line diagrams
and animated IED faceplates.
Security is significantly enhanced with today’s modern RTUs
as well. Legacy RTUs only support elementary passwords,
include no security event logging, and can’t tell you when someone
is logged in. All that is standard fare in modern RTUs, along
with secure protocols based upon public key infrastructure.
With age diminishing the effectiveness of legacy RTUs and
the opportunity for more complete remote control and monitoring
with newer units, substation operators are challenged to find
retrofit solutions that reduce costs and simplify the process.
Eliminating rewiring from the scope of a retrofit can save
significant time and cost for the utility thereby ensuring that
their RTUs will continue to provide critical remote control
and management functions.
Ray Wright is the VP of Product Management, Power
Products at NovaTech Automation, a supplier of automation
and engineering solutions for the electric utilities and process
manufacturing industries. www.novatechautomation.com
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