ENS 52188

v t e ENS Event
23:26 Aug 17, 2016
Title	Offsite Power Source Below the Operability Limit
Event Description	At 1826 [CDT], Operators identified that off-site 161 kV power source predicted post-trip voltage was below the operability limit of 161.3 kV. [Operators] entered AOP-31, 161 kV Grid Malfunctions, Section 1, 161 kV Grid Instability, and declared House Service Transformers T1A-3 and T1A-4 inoperable. [Operators] entered Technical Specification 2.7(2)c. Per Technical Specification 2.7(2)c, 'Both house service transformers T1A-3 and T1A-4 (4.16kV) may be inoperable for up to 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. The loss of the 161kV incoming line renders both transformers inoperable. The NRC Operations Center shall be notified by telephone within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> after inoperability of both transformers.' Per OPPD [Omaha Public Power District] Transmission, grid conditions are currently stable. OPPD Transmission has successfully raised predicted post-trip 161 kV voltage with all predicted voltages meeting or exceeding operability requirement of 161.3 kV as of 1834. Current post-trip predicted voltage is 162.2 kV as of 2029. Lowest observed actual voltage was 163.7 kV. The 161 kV line and transformers T1A-3 and T1A-4 remained available at all times. The licensee notified the NRC Resident Inspector.

ENS 52188 +/-
Where
Fort Calhoun Nebraska (NRC Region 4)
Reporting

Other Unspec Reqmnt
Time - Person (Reporting Time:+-1.93 h-0.0804 days <br />-0.0115 weeks <br />-0.00264 months <br />)
Opened:	Charles Smith 21:30 Aug 17, 2016
NRC Officer:	Vince Klco
Last Updated:	Aug 17, 2016
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v • d • e

v t e Emergency Notification System
Fort Calhoun with Other Unspec Reqmnt
WEEKMONTHYEAR2016-08-17T23:26:00 [Table view]
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