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relay technology. Thus, the rigorous
analysis and testing efforts ultimately
enabled the team to develop a unique
and innovative solution to the open-phase
issue: apply proven protective relaying
technology (voltage balance relays) at the
Class 1E power system boundary along
with use of the EPRI OPD technology for
standby offsite power transformers.
Productivity/Efficiency
Response
Given the fact that nuclear plants
must alter their plant design in some way
due to the open-phase issue, this design
solution offers enhanced organizational
productivity and efficiency by allowing
use of existing surveillance, maintenance,
and alarm response procedures with
minimal revisions. This is because the
protective relay design and hardware
mirrors the physical installation, alarm
response, maintenance, and surveillance
instructions of existing Class 1E
undervoltage relays. The open-phase
detection equipment on the standby
transformers mirrors existing similar
detection equipment and alarm responses
(e.g. transformer trouble alarm).
Transferability
Response
The approach, overall design
strategy, and open-phase solution are
transferrable to other nuclear plants. The
specific analytical techniques and design
concepts have been shared throughout
the industry in NEI forums, NRC public
meetings, and WANO nuclear utility
workshop presentations.
The approach provides for seamless
alignment with existing industry
standards, and members of the team are
actively involved in industry standard
working groups to adapt the various
elements into existing standards (e.g.
IEEE Std 308, 741, 765, and 1792). In
addition, the analysis, overall design
strategy, and implementation plans have
been recognized as an industry strength
in recent INPO inspections.
Ref 1: University of Tennessee
Chattanooga Internal Research Report:
“Investigation of Open-Phase Conditions
in Three-Leg Core-Type Transformers”,
September 2014.
Ref 2: NRC Public Meeting, Design
Vulnerability in Electric Power Systems,
June 27, 2013, NRC Headquarters.
Ref 3: WANO Design and Safety
Challenges of Open Phase Conditions
Workshop, January 13, 2014, WANO
Paris Centre.
Ref 4: World Nuclear News article,
“ETAP Addresses Open-Phase Faults”,
September 9, 2014.
Ref 5: NRC Public Meeting, Status
of Industry Efforts on Open-Phase Issue,
June 4, 2014, NRC Headquarters.
Ref 6: EPRI Report #3002004953,
“TVA Supports EPRI Field Testing of
Open-Phase Detection Technology”,
2014 Technology Transfer AwardWinner.
Contact: Mark Bowman, TVA,
telephone: (423) 751-8239, email:
.
