IEEE PES T&D Conference & Exposition 2022 - 89

for a smaller control house footprint which saves money
in construction. It also allows for significantly less wiring
between devices which lowers cost and reduces the
opportunity for miswiring. It also allows for significant
data to be available for utilities to use to monitor systems
and leverage in their asset management programs. The SF6free
technology innovations such as green gas (g3) enabled
switchgear already to provide clean primary equipment
for the grid.
Figure 7 shows the hierarchical architecture of a digital
substation PAC system divided into three existing levels:
process, bay, and station. Considering the technology
cycles discussed earlier, the process level needs to " simplify "
through digitization using open standard data sharing
communication interfaces (i.e., IEC 61850-9-2LE and/or
IEC 61869-9/13). The bay level should be able to " converge "
PAC applications with centralized substation protection systems.
The modularized hardware of PAC intelligent electronic
devices (IEDs) can provide completely independent
communication ports to facilitate cyber security perimeter
segregation for process bus and station bus. The station bus
can be designed as " future-proof " with software-defined
applications for the grid of the future. As the grid/substation
evolves (such as through renewables penetration), the scalable
substation control/automation application platform can
allow future applications and solutions without replacing the
hardware or platform software.
Process interface units installed close to, or as part of,
primary equipment are used to digitize the signal interface
and communicate to process bus over interoperable IEC
61850-9-2 or IEC 61869-9/13 standards. The software and
settings at the process level need to be minimal or, if
possible, with minimum settings and segregated layer-2
(ethernet) level traffic. Easy-to-install and maintain hardware
delivers higher reliability and, with interoperable protocols,
this data would be available to any application at the
bay or station level.
Centralized Substation
Protection System
Centralized protection and control (CPC) is a concept to
combine the function of several IEDs into a single piece
of hardware as illustrated in Figure 8. This allows more
efficient use of processing power and achieves cost savings
by reducing the amount of hardware used. While
achieving cost savings is important, CPC does not compromise
the stability or ignore the reliability offered by a
conventional solution. Therefore, it is important to find a
balance of saving without overlooking the criticality of
power system operation.
CPC is not just about a single centralized protection
device because this device alone will not bring benefit to
the user. CPC is a system involving process-level digitization
and a substation human-machine interface. Having all functions
running in one centralized hardware opens some new
requirements, such as the need for robust cyber security in
a CPC unit, redundant systems to prevent maloperation due
to a faulty device, and time synchronization. Please refer to
the IEEE Power and Energy Society Power System Relaying
and Control Committee's Working Group K15 report online
for more details on the CPC system.
Software-Defined Automation
and Controls
Figure 9 presents innovation driving software-defined grid
automation and control platforms. The virtualized architecture
Integrated Digital Substation Architecture
Simplify at Process
Digital IO Interface
Converge at Bay
P&C IEDs
Future-Proof at Station
Automation at Adv Applications
LPITs -Optical
CT/VT
Bay Level Architectural Drivers
* Converged P&C Functions-Less HW at Bay
Digital Power
Equipment
Process Level Architectural Drivers
* Simple to Configure IO and Digital Sensor Types
* Easy to Install/Retrofit, Higher Reliability/Life
* Easy to Maintain-Least Intelligence/Safety Functions
* L2 Traffic Segregation-Inherent Cyber Security
* Leads to Digitized Primary Equipment and LPITs
figure 7. Digital substation architecture.
April 2022 Show Issue
ieee power & energy magazine
89
* Easy Device Management
* Virtual-Isolation of IEDs for Testing and Maintenance
Station Level Architectural Drivers
* Future Proof and Flexible Platform for Any Grid Challenges
* Advanced Automation and Wide-Area Applications
* Integrated Condition Monitoring (CBM)
* Cyber Security at Layer-3 (R-GOOSE, R-SV)
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