05000416/FIN-2015007-03

Finding

Title

Lack of Coordination of Division III HPCS Switchgear 127N Undervoltage Relays

Description

The following issues were discussed during the inspection; however, the team must review additional information provided by the licensee to determine whether these issues result in a more than minor performance deficiency or a violation of NRC requirements. In accordance with Inspection Manual Chapter 0612, this issue will be characterized as an unresolved item. The incoming offsite power supply circuit breakers for Division III 4160 V switchgear 17AC are equipped with 127N undervoltage relays. According to Drawing E-1009, One Line Meter and Relay Diagram, 4.16kV E.S.F. System Bus 17AC, Revision 9, these relays Trip incoming breaker to bus & start diesel. According to drawing E-0121-005, Summary of Relay Settings (ESF) 4.16 kV Bus 17AC and Diesel Gen 13, Revision 7, these relays are set with a 0 second time delay. This instantaneous time response potentially results in lack of coordination of the 127N undervoltage relays with high voltage system protective relays, switchgear overcurrent relays, and loss of voltage relays, thus preventing the other relays from performing their credited design functions. Protective devices that the 127N undervoltage relays are potentially not coordinated with are as follows: Protective relays associated the main transformer and its output circuit: Lack of coordination between the 127N undervoltage relays and the protective relays associated with the main transformer and its output circuit can result in coincident loss of two alternating current power supplies, contrary to the requirements of General Design Criterion 17. Grand Gulf Updated Final Safety Analysis Report Section 8.3.1.2.1 states: The degree of reliability of the power sources required for safe shutdown is considered very high due to independence and ample redundancy; it equals or exceeds all the requirements of Criterion 17. General Design Criterion 17 states: Provisions shall be included to minimize the probability of losing electric power from any of the remaining supplies as a result of, or coincident with, the loss of power generated by the nuclear power unit... Contrary to this General Design Criterion 17 requirement, a fault on the main transformer or its high voltage connection to the transmission system could cause coincident loss of electric power from both the main generator and the offsite power supply to Division III. The protective relaying on the main transformer and its output circuit is designed to initiate tripping of the main generator and isolation of the area of the fault without causing any cascading failures. However, the 127N undervoltage relay for the Division III 4160 V switchgear would also respond spuriously to the momentary voltage dip caused by the fault and cause loss of the offsite power supply to Division III. Transmission system bus protective relays: Grand Gulf Updated Final Safety Analysis Report Section 8.2, Offsite Power System, Subsection 8.2.2.1, Availability Considerations states: Short circuits on a section of a bus are isolated without interrupting service to any circuit other than that connected to the faulty bus section. Contrary to this requirement, the instantaneous setting of the 127N relays would not coordinate with the transmission bus protective relays and would react to the momentary voltage dip caused by a transmission system bus fault, resulting also in spurious loss of the offsite power supply to Division III. Loss of Voltage Relays: In addition to the 127N undervoltage relays, Division III high pressure core spray 4160 V switchgear 17AC is equipped with 127S1, S2, S3, and S4 loss of voltage relays and 127 1A, 1B, 2A, and 2B degraded voltage relays, which also trip the offsite power supply to 17AC upon actuation. NRC Regulatory Issue Summary 2011-12, Adequacy of Station Electric Distribution System Voltages, Revision 1, describes one of the functions of the degraded voltage relay time delay as follows: The time delay shall override the effect of expected short duration grid disturbances, preserving availability of the offsite power source(s). The same principle is relevant to the other undervoltage relays that automatically trip the switchgear offsite power supply. This conclusion is consistent with Grand Gulf Updated Final Safety Analysis Report Section 8.3.1.1.2.3, which states: Protective devices of Class 1E systems, particularly the ECCS, are set to maintain continuity of power as long as possible short of causing a derangement of the equipment. However, the 127N undervoltage relays do not preserve availability of power as long as possible in the event of harmless transmission grid voltage transients, such as those caused by lightning strikes and normally-cleared faults on transmission lines, because their instantaneous setting miscoordinates with the time delay setting of the Technical Specification credited loss of voltage relays 127S1, S2, S3, and S4. According to Technical Specification Table TR 3.3.8.1-1, the 127S1, S2, S3, and S4 loss of voltage relays have a time delay setting of 2.3 seconds. According to Section 6.17 of calculation JC-Q1P81-90027, Division III Loss of Bus Voltage Setpoint Validation (T/S 3.3.8.1), Revision 2, Spurious segregation from the offsite source is prevented by the time delay function. However, since the non- Technical Specification 127N relays react instantaneously to trip the offsite power source during momentary voltage dips, their 0-second time delay setting invalidates this credited design function of the 2.3-second time delay of the 127S1, S2, S3, and S4 loss of voltage relays. Therefore, spurious segregation from the offsite source is not prevented, and a vulnerability exists for unnecessary loss of offsite power events initiated by, and subsequent to, harmless voltage transients from the transmission system. An actual event of this type occurred on April 2, 2012, as described in Licensee Event Report 2012-003. A lightning strike on a 500 kV transmission circuit resulted in actuation of the instantaneous 127N relay and unnecessary loss of the offsite power supply to the Division III electrical distribution system. Switchgear 17AC offsite power supply circuit breaker overcurrent relays: Grand Gulf Updated Final Safety Analysis Report Section 8.3.1.1.4.2.5.3, HPCS Class 1E Electrical Equipment Circuit Protection states: Emphasis is given in preserving function and limiting loss of Class 1E equipment function in situations of power loss and equipment failure. Contrary to this statement, the instantaneous setting of the 127N undervoltage relays prevents the offsite power supply circuit breaker overcurrent relays from preserving function and limiting loss of Class 1E equipment function in the event of a switchgear bus fault. Switchgear 17AC offsite power supply circuit breakers are equipped with 151B overcurrent relays that, when actuated, trip and lockout the switchgear supply breakers. The purpose of the lockout function is to prevent attempted reenergization of a faulted bus. However, due to the instantaneous response time of the 127N undervoltage relays, the fault would be cleared and the bus deenergized on the undervoltage signal before the overcurrent relays could respond and initiate the bus lockout signal. This would result in automatic starting of the Division III diesel generator, closure of the diesel generator output breaker onto the faulted bus, and the potential for damage to the diesel generator and further damage to the switchgear. Switchgear 17AC feeder circuit breaker overcurrent relays: The circuit breakers for feeders downstream of switchgear 17AC are equipped with 150/151M and 150/151T overcurrent relays that are designed to isolate downstream faults locally. Grand Gulf Updated Final Safety Analysis Report Section 8.3.1.1.2.3, Control Power and Circuit Protection states: A complete analysis of the application and coordination of the protective devices on Class 1E distribution has been conducted. This analysis shows that under design operation of these devices, faults, and undervoltages will be detected and corrected at the lowest level of distribution. Referring to the 150/151M and 150/151T overcurrent relays, Grand Gulf Updated Final Safety Analysis Report Section 8.3.1.1.4.2.5.3 states: Relay settings are coordinated in such a way that interference of service is not communicated to a higher level involving equipment other than that immediately affected by the fault or overload. Contrary to these requirements, the licensee failed to perform a coordination analysis or to ensure that interference of electrical service is limited as described. The voltage dip caused by a fault on a 4160 V circuit downstream of switchgear 17AC would be detected by the 127N relay, which would react instantaneously to trip the 17AC switchgear offsite power supply circuit breaker rather than isolating the fault locally at the downstream circuit breaker. This is contrary to the design criterion that the fault be detected and corrected at the lowest level of distribution and maintain continuity of power to the switchgear. These issues were entered into the licensees corrective action program as Condition Report CR-GGN-2015-4973.

03
Site:	Grand Gulf
Report	IR 05000416/2015007 Section 1R21
Date counted	Dec 31, 2015 (2015Q4)
Type:	URI:
cornerstone	Mitigating Systems
Identified by:	NRC identified
Inspection Procedure:	IP 71111.21
Inspectors (proximate)	G George G Warnick M Young N Day P Hernandezd Lovelessh Leake J Watkins L Brandt R Latta T Farnholtz W Sherbin J Mchugh
INPO aspect
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v • d • e

Finding - Grand Gulf - IR 05000416/2015007

1(6)2(5)3(1)4(6)5(0)6(0)7(11)8(4)201(6)301(1)402(0)403(0)404(3)405(4)406(1)501(0)

IR 05000416/2015007: 1 2 3 4 5 6 7 8 9 10 11

Finding List (Grand Gulf) @ 2015Q4

CCA Matrix: 2015Q4

	Q	CCA	Title
05000416/FIN-2015001-02	2015Q1	H.12	Failure to Follow a Procedure Resulting in the Unplanned Inoperability of the Reactor Core Isolation Cooling System
05000416/FIN-2015001-05	2015Q1	H.8	Failure to Establish, Implement, and Maintain Appropriate Changes to the Offsite Dose Calculation Manual For REMP Airborne Sampling
05000416/FIN-2015001-04	2015Q1	H.1	Failure to Properly Calibrate Main Steam Line Radiation Monitors and Containment/Drywall High Range Radiation Monitors
05000416/FIN-2015001-03	2015Q1	P.2	Emergency Action Level Scheme for Nonfunctional Seismic Monitor
05000416/FIN-2015201-06	2015Q1		Security
05000416/FIN-2015201-05	2015Q1		Security
05000416/FIN-2015201-04	2015Q1		Security
05000416/FIN-2015201-03	2015Q1		Security
05000416/FIN-2015201-02	2015Q1		Security
05000416/FIN-2015201-01	2015Q1		Security
05000416/FIN-2015001-01	2015Q1		Failure to Take Timely Corrective Actions Associated with Division 1 and 2 Standby Service Water Pump House Ventilation System Due to Degraded Relays
05000416/FIN-2015001-06	2015Q1		Failure to Adequately Establish Commercial-Grade Items as Basic Components
05000416/FIN-2015002-03	2015Q2		Failure to the Update the Final Safety Analysis Report after the Extended Power Uprate
05000416/FIN-2015002-04	2015Q2		Possible Loss of Communications Systems during Control Room Fire Scenarios
05000416/FIN-2015002-01	2015Q2	H.12	Failure to Have Appropriate Instructions Resulted in the Unplanned Unavailability of the Reactor Core Isolation Cooling System
05000416/FIN-2015002-02	2015Q2	H.12	Failure to Identify High Vibration on the Division 3 EDG Soak Back Oil Pump
05000416/FIN-2015405-01	2015Q3		Security
05000416/FIN-2015003-01	2015Q3		Failure to Have Appropriate Instructions for Preventative Maintenance on the Division II Diesel Generator Fuel Rack Control Lever
05000416/FIN-2015007-05	2015Q4		Failure to Maintain a Safety-Related Cable Tray Overfill Analysis Record
05000416/FIN-2015007-02	2015Q4	H.6	Failure to Ensure that Electrical Interrupting Devices are Rated for Available Fault Current Levels
05000416/FIN-2015004-03	2015Q4		Failure to Make a Required Eight-Hour Report for Loss of Safety Function
05000416/FIN-2015007-07	2015Q4		Failure to Update the Final Safety Analysis Report
05000416/FIN-2015008-03	2015Q4	H.12	Failure to Declare Secondary Containment Inoperable Based on Failed Surveillance Testing
05000416/FIN-2015404-03	2015Q4		Security
05000416/FIN-2015404-02	2015Q4		Security
05000416/FIN-2015404-01	2015Q4		Security
05000416/FIN-2015007-08	2015Q4		Incomplete and Inaccurate Response to NRC Bulletin 88-04
05000416/FIN-2015008-04	2015Q4		Failure to Make Required Event Notification
05000416/FIN-2015007-03	2015Q4	S.4(o)	Lack of Coordination of Division III HPCS Switchgear 127N Undervoltage Relays
05000416/FIN-2015007-01	2015Q4		Failure to Ensure Safety-Related Alternating Current and Direct Current Equipment Operability and Functionality at Maximum Allowable Voltage Levels
05000416/FIN-2015008-01	2015Q4	P.1	Failure to Enter a Condition Adverse to Quality into the Corrective Action Program
05000416/FIN-2015007-04	2015Q4	H.8	Failure to Identify and Address Impacts of Revised Calculation Output Data
05000416/FIN-2015007-06	2015Q4		Failure to Perform Surveillance Requirement 3.8.1.9
05000416/FIN-2015007-09	2015Q4		Failure to Obtain a License Amendment for Use of Probabilistic Methods to Evaluate Tornado Missile Hazards
05000416/FIN-2015007-10	2015Q4	P.6	Failure to Ensure Equipment Operability and Functionality of Allowable Alternating Current Frequency Range
05000416/FIN-2015007-11	2015Q4	H.12	Failure to Implement Equipment Control Procedures for Loose Items in Containment
05000416/FIN-2015004-04	2015Q4		Failure to Establish Adequate Maintenance Instructions to Perform Work Activities on the Division III Diesel Generator Overspeed Trip Limit Switch
05000416/FIN-2015004-02	2015Q4	H.14	Failure to Timely Enter Technical Specification Surveillance Requirement 3.0.1
05000416/FIN-2015004-01	2015Q4	H.6	Failure to Have Appropriate Instructions for Preventative Maintenance on the Division I Diesel Generator Simulated Run
05000416/FIN-2015301-01	2015Q4	H.8	Inadequate Plant Operating Procedures with Eight Examples
05000416/FIN-2015008-02	2015Q4	P.1	Failure to Promptly Initiate Condition Reports

Self-Identified List (Grand Gulf)

	Q	Title
05000416/FIN-2015002-05	2015Q2	Licensee-Identified Violation
05000416/FIN-2015405-02	2015Q3	Licensee-Identified Violation
05000416/FIN-2015405-03	2015Q3	Licensee-Identified Violation
05000416/FIN-2015405-04	2015Q3	Licensee-Identified Violation
05000416/FIN-2015406-01	2015Q3	Security
05000416/FIN-2015004-05	2015Q4	Licensee-Identified Violation
05000416/FIN-2015004-06	2015Q4	Licensee-Identified Violation

[Grand Gulf Findings full list]

05000416/FIN-2015007-03

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