ML23125A093
| ML23125A093 | |
| Person / Time | |
|---|---|
| Issue date: | 01/10/2023 |
| From: | Mohammad Sadollah NRC/RES/DE |
| To: | |
| Mo Sadollah 301-415-6804 | |
| References | |
| Download: ML23125A093 (1) | |
Text
1. DVR/LOV working status Docket Number Link Link Address Date Summary description of event 2. Deg. Voltage or Loss of Lessons and Insights Reference Information Voltage condition during performance of a second level undervoltage surveillance, Class-1 E 4.16 KV Bus 13- No LOVR/DVR actuation (but Errors during surveillance and Xelon Generation, Licensee Event Report 254/2018-005-01 "Loss 1 tripped on an Undervoltage Protection [surveillance error causing testing insuced findings are applicable) calibration of DVR/LOVR could of Safety Bus and Automatic Actuation of a Safety System During 254 2542018005 PDFView.ashx (inl.gov) 10/24/2018 grounding in DC and an inadvertent UV signal]. The associated EDG started but could not become risk significant.
Undervoltage Relay Surveillance," Quad Cities Nuclear Power load due to surveillance alignment. NO LOV or Degraded Voltage Station Unit 1, November 21. 2019; Condition Unit 1 Failure of a Timing Relay During a Technical Specification Surveillance. The PDF file No LOVR/DVR actuation (but It appears Solid state relays is not easily readable. Main conclusion is as follows: There have been many occurrences findings are applicable) generally used for DVRs are where the as-found condition of this or similarly functioning timing relays were found much more resillent to out of acceptance criteria or outside Technical Specification criteria. However all events NO LOV or Degraded Voltage setpoint drift. South Texas Project Unit 1 Docket No. SIN 50-498 Licensee Event 498 4982017001 PDFView.ashx (inl.gov) 3/10/2017 involved the old model E7000 timers. It is important to note that the older model relays Condition Report 2017-001-00 Unit 1 Failure of a Timing Relay During a are diaphragm type designs, while the new relay timers are solid state designs. Since Technical Specification Surveillance these timers were replaced (starting in 2012) this condition is the first case of its kind.
While doing the third harmonic test for generator relay drop off, they received a DVR worked (actuated)
Turkey Point Unit 4 Docket No. 50-251 Reportable Event: 2013-002-degraded voltage condition. The trip occurred as a result of degraded voltage at the 480V 251 2512013002 https://lersearch.inl.gov/PDFView.a 4/19/2013 00 Reactor Trip Due to Loss of Offsite Power Resulting From load centers (down to 440 volts for 60 Seconds) . Wrong procedure was use. Degraded Voltage condition Generator Testing, June 18, 2013 (internal causes)
The electrical insulator failure resulted in a sustained open phase event and a low level LOVR did not work Response of LOVR and DVR to ground fault occurred on the SAT 242- 1/2 side of the open phase.The 4.16 kV OPC should be evaluated.
Byron Station, Unit 1 05000454 12 OF 12 2, Docket No. 05000454, 455 4542012001 https://lersearch.inl.gov/PDFView.a 1/30/2012 Engineered Safety Feature (ESF) buses undervoltage protection scheme did not satisfy Sustained open phase condition September 28, 2012 due to open phase condition and it did not automatically switch over to the emergency (OPC) not LOVR Diesel Generators (DG).
Following a scram, the Auxiliary Power System transferred from its main power source to No LOVR actuation (Not the reserve power source, as designed. During this transfer, the Unit 2/3 Emergency Applicable)
Diesel Generator automatically started. This automatic start occurred as the result of the Exelon, Dresden Nuclear Power Station, Unit 3 Renewed Facility 249 2492010001 https://lersearch.inl.gov/PDFView.a 10/11/2010 EDG start logic momentarily sensing both the main power source breaker and the NO LOV or Degraded Voltage Operating License No. DPR-25 NRC Docket No. 50-249 - December reserve power source breaker contacts being open concurrently. Since there was no Condition . Spurious EDG start 10, 2010 undervoltage signal received, the automatic start of the EDG is considered invalid.
Electrical supply breaker was inadvertently opened, which caused the "C" Reserve No LOVR actuation (Not Station Service Transformer (RSST) to de-energize. There was issue with calibrating the Applicable) Calibration methods for timing bus transfer during UV condition but not for the emergency buses. The event is generally relays will be examined so that Virginia Electric and Power Company, North Anna Power Station ,
339 3382009004 https://lersearch.inl.gov/PDFView.a 12/9/2009 of interest since it identifies generic calibration issues for UV relays including delay time NO LOV or Degraded Voltage specific methods may be Docket No.: 50-338 , February 3, 2010 (Part of utility Corrective Action Program (CAP), not discussed) Condition required or disallowed for certain circuits.
Both Units of Turkey Point tripped and undervoltage relays were actuated after a one LOVR properly actuated second time delay. The grid voltage disturbance occurred due to human error when a Protection and Control (P&C) field engineer disabled both levels of local protection at an LOV condition (Grid fault) 250 2502008001 https://lersearch.inl.gov/PDFView.a 2/26/2008 FPL, Turkey Point Units 3 and 4 ,05000250, April 25, 2008 electrical substation which then failed to actuate when a fault occurred during equipment troubleshooting (manual clearing of the fault took 1.7 second more than 1 second time allotted).
While off-site power was lost to several on site buildings,it was never lost to DVR was not actuated but the Manual transfer should be the busses supplying the power block area. Although the safeguards bus voltage was offsite power was manually considered as a back up to DVR swinging as a result of the grid transient, the voltage did not reach the undervoltage stripped for Grid instabilities.
setpoints. However, the Operators determined that the off-site supply was unreliable, manually started the Emergency Diesel Generators (EDGs), and then manuallyt Grid instability due to switching RGE, LER 2003-002, Major Power Grid Disturbance Causes Loss of 244 2442003002 https://lersearch.inl.gov/PDFView.a 8/14/2003 ransferred the safeguards busses to the EDGs. This resulted in declaring an Unusual transients Electrical Load and Reactor Trip R.E. Ginna Nuclear Power Plant Event that was terminated after power was later transferred back to the off-site sources. Docket No. 50-244 , October 9, 2003 On an event started by ground fault in 500 KV breaker, generator separated, turbine DVR worked (actuated) but not Design time delay and voltage triped and reactor scrammed. The E-buses were transfered to preferred power source in as intended recovery setpoint may not have addition of three of the Circulating Water (CW) pumps per design. The 4KV vital bus been correct. Time delay and PSEG, Salem Generating Station Unit 1, 'Reactor Trip due to Turbine voltages dropped below the second level undervoltage setting of 95.1%. Voltage on the Degraded Voltage condition voltage recovery setpoint 272 2722003002 https://lersearch.inl.gov/PDFView.a 7/29/2003 Trip Caused by a 500KV Switchyard Breaker Trip' LER 272, Salem Unit 1 4KV vital busses did not recover to the reset setpoint before the relay (internal causes) should have accounted for September 24, 2003 timeout caused the relay logic to separate the vital busses from offsite power. voltage dip and recovery time caused by start of 3 CW pump.
CCF (Common Cause failures) of fuses caused actuation of the LOVR actuated due to fuse Division 1 undervoltage (UV) protective circuit failures Exelon, LaSalle County Station, Unit 2, Docket No. 50-374, October 374 3742001003 https://lersearch.inl.gov/PDFView.a 9/3/2001 21, 2001 No low voltage condition A complex event during maintenance of bistable in RPS logic caused trip, Low voltage on DVR worked (actuated) 480 bus, striped the emergency bus and connected to EDGs. One bus tripped off due to overcurrent trip. Post trip evaluation found that found that the actual over current trip Degraded Voltage condition Indian Point No. 2, Docket No. 05000274, "Reactor Trip, ESF 247 2471999015 https://lersearch.inl.gov/PDFView.a 8/31/1999 setpoint for its Amptector was at 3200 amps, rather than the 6,000 amps setting as (internal causes) Actuation, Entry into TS 3.0.1, and Notification of Unusual Event."
designed. In addition the event might have been prevented if the Station Auxiliary August 31, 1999 Transformer Tap Changer was not in manual mode due to a defective voltage control relay.
During a bus voltage transfer from Aux. Transformer to SU transformer, A degraded DVR worked (actuated) GPU Nuclear, Oyster Creek Nuclear Generating Station Docket No.
voltage condition was experienced on 4160 emergency buses resulting in spearartion 50-219, Licensee Event Report 97-010: Manual Reactor Scram, 219 2191997010 https://lersearch.inl.gov/PDFView.a 8/1/1997 from offsite power. The cause of degraded voltage was the inapporpriate setting of the Degraded Voltage condition Engineered Safety Feature Actuation and Design Deficiencies Noted SU transformer voltage regulator below the Degraded voltage setting. (internal causes) As a Result of Main Generator Exciter Preventive Maintenance, September 2, 1997 during the performance of an increased frequency surveillance test, 4 out of 8 Essential No LOVR/DVR actuation (but The calibration source should Bus Degraded Voltage relays were found high outside Technical Specification (TS) test findings are applicable) be free from harmonics per using an improved calibration technique. On October 17, 1994 all 8 relays were found NRC guidance. The distortion Duane Arnold Energy, DOCKET NUMBER: 05000-331, Essential Bus low outside the TS voltage limits using the improved calibration method. A 4.7 to 5.1% NO LOV or Degraded Voltage could be reduced by filters.
331 3311994012 Licensee Event Report Search l NRC 10/4/1994 Degraded Voltage Relay Calibration Errors Due to Harmonics, power source distortion (Harmonics) was identified which subsequently equated to Condition The filters should attenuate October 14, 1994 approximately 4.0 to 5.0 volt variance in the relay trip set points. The recommended higher harmonics below 3%.
vendor maximum distortion was 3%. IEEE std 141 should be consulted.
On June 3, 1991, the 91.6% sustained undervoltage relay minimum drop out No LOVR/DVR actuation (but The type of relay and trip setpoint voltage, for two (2) of the three (3) of the 2A 4KV Vital Bus undervoltage findings are applicable) calibration method with relays and for all three (3) 2B 4KV Vital Bus undervoltage relays, were found to be below harmonic free source will affect Salem Generating Station Unit 2, DOCKET NUMBER: 05000311, "4KV the Technical Specification minimum allowable value of 91%. The lowest as-found trip NO LOV or Degraded Voltage the relay setpoints. Certain Vital Bus UV Relay Setpoints Found Below Minimum Tech. Spec.
311 3111991008 https://lersearch.inl.gov/Index.aspx 6/3/1991 setpoint, of the five subject relays was 90.5%. The causal factors of the setpoint variance Condition relay types such as ASEA Brown Allowable Value." EVENT DATE: 06/03/91 LER #: 91-008-01 REPORT are relay design inadequacy and procedure inadequacy. The 4KV Vital Bus 91.6% Boveri type 27N relays appear DATE: 07/09/92 undervoltage Rochester relays (both Salem Units) were replaced with ASEA to have less setpoint drift.
Brown Boveri type 27N relays.
spurious actuation of the Unit 2 X01C phase fire deluge spray system. The spurious LOVR actuated properly This event also highlights the deluge spray apparently induced a flashover from the transformer to ground, (worked) potential complications that which was detected by protective circuitry causing generator and turbine trip followed may be introduced in setting Point Beach Nuclear Plant Unit 2,Docket No. 05000301, Fire by reactor scram. The emergency diesels automatically started because of bus the LOVR set point if there is 301 3011989002 https://lersearch.inl.gov/PDFView.a 3/29/1989 System Actuation Induced 2X01C Fault and Unit Trip, March 29, undervoltage. The undervoltage condition was the result of the premature actuation of LOV condition (internal causes) cross connections between 1989 the generator stuck breaker protection relay, which isolated a Unit 1 bus section cross- units.
connection. Voltage dips to 3700 volts on the normal 4160 v system were experienced.
LOVR worked (actuated) Dresden Nuclear Power Station, Unit 3, DOCKET NUMBER:
A phase-to-ground fault occurred, causing the loss of reserve auxiliary transformer 05000249, Turbine Trip and Reactor Scram on Stop Valve Closure 249 2491989001 https://lersearch.inl.gov/PDFView.a 3/25/1989 (TR) 32 which is fed from 345 KV Bus 8. Bus 32 feed breaker transfer from TR 32 to TR 31 Loss of voltage condition Due to Slow Transfer of House Loads During Loss of Offsite Power, was slow resulting to loss of the bus. March 25, 1989