Microprocessor-Based Relays:
Implementation, Conflicts, and
Corrective Actions
Steven V. Deases
AEP – Station Engineer
Intro: Discussion Focus
• Level: High-Level Topic Discussion
• Scope: Station Protection
• Questions: Reserve Questions until the Conclusion
• Time Limitation: Approximately 30 minutes total
• Prospective: AEP’s Experiences
Intro: Discussion Focus
• Structure:
• Implementation Strategy
• Conflicts Encountered
• Corrective Actions
• Topics:
• Engineering Processes
• SCADA Communications
• Commissioning Procedures
Intro: Presenter’s Background
• Work Group:
• AEP Transmission Region Operations – Texas
• Technical Support Engineering
• Station Equipment and Protection & Controls
• Job Functions:
• Application Engineering & Design Review
• Technical Aid to Field Personnel
• Project Coordination & Administrative Support
• Technical Training of Technicians and Engineers
• Process Improvement & Quality Control
• System Performance Analysis & Reporting
Microprocessor Technology
Evolution of Protection Devices
Electromechanical
Steady
State
Microprocessor
Microprocessor Technology
• Advantages
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More sensitive and scalable
Communication Options
Fault Oscillography and SER data
Better targeting and annunciation
More reliable; failure alarm also included
Advanced protection features all in one box
Economical both Financially and Physically
• Disadvantages
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Shift in Thought: Digital Logic v. Circuitry
More Complex Logical Systems
Longer Commissioning Procedures
Additional Training Requirements
Engineering Processes
Engineering Aspects Affected:
• Standards
• Design
• Documentation
• Philosophy
Engineering Processes
Implementation Strategy:
Develop internal Standard Schemes for Protection & Control using
Microprocessor-based Relays that would replace existing
Electromechanical Relays and phase them out
These replacement schemes would be designed with a “protection zone”
scope (Line, Bus, Transformer, etc.)
The developed standards defined details such as:
– relay brand/model options
– general protection scheme with generic wiring
– relay panel plate configurations
– relay setting templates with predetermined logic
Engineering Processes
Documentation:
The intent of the documentation was to communicate the standards to
the design groups for implementation
Application Guides were written which described
– What standard schemes were available
– Where the standard schemes were to be applied
– What kind of protection was intended
– The general relay setting philosophy
CAD drawings with multiple layers were also developed to match the
standard relay schemes
Engineering Processes
Conflicts Encountered:
Despite the large effort in strategizing the implementation process, there still were
several conflicts encountered:
• Perpetual evolution of “standards” due to newly gained experiences
• Design Interpretation of standards resulted in inconsistent implementation
• Lack of adequate communication and training of standards
Engineering Processes
Corrective Actions:
To combat these engineering problems, we created and adopted…
•
“Design Module” concept that specifically lays out the entire intended design package of
protection for a specific station application

E.g. – 25MVA Power Xfmr w/ LV CB (Xfmr and LV Bus protection included)
•
Consistent Relay Setting Calculation Sheets
•
Additional Training of how to use these tools and the philosophy intent
•
Revision control of Standards
SCADA Communications
SCADA Communication Components:
• Relay
• RTU
• SCADA Master
SCADA Communications
Implementation Strategy:
• Send all potentially necessary data points to RTU, then filter which were actually
deemed necessary for Dispatchers to be sent to the SCADA Master
• Let local personnel decide which points the SCADA system are needed, configure the
devices themselves, and commission the data path
• Use existing equipment and communication protocols when able
SCADA Communications
Conflicts Encountered:
• Inconsistent amounts / types of data being sent to Dispatch
• Project Slowdown due to communication discussions on every project
• Little documentation of what was implemented
• Confusion regarding data identity due to lack of data point naming conventions
• SCADA Alarm Logging was not chronological
SCADA Communications
Corrective Actions:
• RTU Point Assignment documentation
• Communication Configurations for relays & RTUs delivered by engineering
• Training of advanced commissioning techniques
• Convert RTUs and Communication Protocol
Hard
Wired
Harris
DNP
Harris
DNP
DNP
Commissioning
Commissioning Aspects:
• Practices
• Procedures
• Troubleshooting
Commissioning
Implementation Strategy:
It was initially assumed that commissioning Microprocessor-based relays was essentially
very similar to commissioning Electromechanical relays.
Test each protection element individually while monitoring trip output.
Technician can create his own test plan based on past electromechanical procedures.
Commissioning
Conflicts Encountered:
The “Black Box” phenomena: one device that performs multiple functions with several
different outputs (trips, alarms, targets, annunciations, etc.)
Element Testing vs. Functional Testing
Those installing the scheme often asked, “What’s the intent of the design?”
“How should the scheme operate for this scenario?”
The procedure for troubleshooting a mis-operation or failed test is much different than that
of an electromechanical relay scheme
Commissioning
Corrective Actions:
• Commissioning Guides
• Automated Testing Procedures with Pre-determined Test Plans
• Design Intent Documents provided with each engineered job
• Logic Diagrams matching actual programmed internal logic
• New Training Program at New Training Facility
Lessons Learned
– Process Improvements
• Re-engineering the process is sometimes needed
• Continual auditing of the process
– Specify Process Feedback Loops
• Identify Experts for Focus Groups
• Defined Time Interval for Revisions to take place
– Quality Control
• Adding quality analysts to team
• Strengthening peer-review ideals
– Workforce Solutions
• Invest in additional engineers, technicians, and support staff
• Invest in Training Programs