ML17349A350
| ML17349A350 | |
| Person / Time | |
|---|---|
| Site: | Turkey Point  |
| Issue date: | 08/17/1992 |
| From: | FLORIDA POWER & LIGHT CO. |
| To: | |
| Shared Package | |
| ML17349A349 | List: |
| References | |
| NUDOCS 9208250065 | |
| Download: ML17349A350 (18) | |
Text
FLORIDA POWER AND LIGHT COMPANY TURKEY POINT UNITS 3 AND 4 ENGINEERING EVALUATION for VERIFICATION OF PSB-1 COMPUTER MODEL FOR SETTING OF UNDERVOLTAGE RELAYS
'9208250065 920817
1 lt I
L-92-204 Engineering Evaluation Page' of 7 TABLE OF CONTENTS 1.0 PURPOSE/SCOPE 2.0 ANALYSIS/EVALUATION
3.0 CONCLUSION
4.0 REFERENCES
ATTACHMENTS Undervoltage Relay Setpoints for FPL Turkey Point Units 3 and 4 Measured Field Voltage and Loading Values Versus Calculated Voltage Values and Percentage Difference
Engineering Evaluation Page 3 of 7 1.0 PURPOSE SCOPE This evaluation is provided in response to an NRC request (Reference 4.10) to verify by actual test that the computer model including inputs (i.e., cable sizes and equipment data) which was utilized to determine the Technical Specification 480 volt (480V) undervoltage relay setpoints correctly models the actual field configuration. This verification is required by NRC Power Systems Branch Technical Position 1 (PSB-1) . This evaluation shall be classified as Safety Related.
This verification of the computer model (Ebasco Computer Program AUXSYS 4078 12/31/89), associated with Calculation EC-145 "PSB-1 Voltage Analysis foz Electrical Auxiliary System", is performed by obtaining field measurements of the safety related bus loading and voltages during unit operation. The field measured bus loading is then input into the computer program and the resultant computer calculated voltages compared to the field measured voltages, These voltages shall be within 3%.
2.0 ANALYSIS 2.1 UNDERVOLTAGE RELAY TECHNICAL SPECIFICATION AMENDMENT The setpoints of the 480V load center undervoltage relays were modified during the Emergency Power System (EPS)
Enhancement Project. These setpoints were required to be modified as the EPS Enhancement Project added additional safety related busses and modified the loading on the existing safety related busses. As these settings are included in the Technical Specifications, a license amendment was submitted to obtain the required Technical Specification change. The NRC reviewed the amendment and issued Amendments Numbers 145 to Turkey Point Unit 3 and 140 to Turkey Point Unit 4 with a Safety Evaluation to incorporate the revised settings (Reference 4.10) . This Safety Evaluation required the following:
"Since the voltage and time delay trip settings have been calculated using a new computer program, the staff requires that the new software' analytical techniques and assumptions be verified by actual test and the results be provided to the NRC prior to the next refueling outage."
2.2 480V UNDERVOLTAGE RELAY SCHEME DESCRIPTION This section provides a description of the 480V undervoltage relay scheme.
a ~ The undervoltage monitoring system on the 480V safety related load centers is provided so that degraded (loss of voltage) load center voltage concurrent with a safety injection signal (SIS) would initiate transfer to onsite power. A set of two instantaneous undervoltage relays on each safety related load center are installed to monitor the load center voltage. The
Engineering Evaluation Page 4 of 7 2.2 480V UNDERVOLTAGE RELAY SCHEME DESCRIPTION continued two relays in each load center are connected in an "AND" logic and, when actuated due to a degraded (loss of voltage) voltage concurrent with a SIS and an open EDG breaker, would initiate, via time delay relay, load shedding, EDG start, onsite power connection and sequencing of the necessary loads.
- b. Also, the undervoltage monitoring system on the 480V safety related load centers is provided so that, if the offsite source experiences sustained undervoltage, and to prevent damage to associated 460V motors, would transfer to onsite power. To accomplish this it function a set of two inverse time delay undervoltage relays is installed for each safety zelated 480V load center bus. These relays initiate load shedding, EDG start and onsite power connection, and sequencing in the same manner as the instantaneous undervoltage relays in Item (a) above.
2.3 ANALYSIS EVALUATION The setting of the undervoltage relays are designed to protect Class 1E motors from degraded voltage. These settings are also selected to prevent spurious separation of the plant distribution system from the offsite power source due to the actuation (starting a large load) of the undervoltage relays.
Calculations No. PTN-BFJE-92-022, Revision 0, "PSB-1 Voltage Analysis for Electrical Auxiliary System", (Reference 4.4) and EC-145, Revision 5, "PSB-1 Voltage Analysis for Electrical Auxiliary System", (Reference 4.6) provide the setpoints for the undervoltage relays. The undervoltage relay setpoints (with available margin) are shown in Attachment 1. Calculation No. PTN-BFJE-92-031, Revision 0, "Verification of PSB-1 Computer Model", (Reference 4.5) provides the verification that the computer model used for determining the undervoltage relay setpoints for PSB-1 correctly models the actual field configuration. The verification was performed by taking actual field readings (bus voltages and curzents) on the plant AC system (References 4.2 and 4.3). The field readings were entered into the computer model (Reference 4.5) to demonstrate that the voltages obtained with the computer model are within 3%
of the voltage values obtained using actual field readings.
This would satisfy the requirements identified in Branch Technical Position PSB-1 (Reference 4.1).
The PSB-1 position states that the verification and testing should be performed in accordance with the four items listed in Section 4 of the branch position. These items and the method utilized to achieve resolution of these items are as follows:
L-92-204 Engineering Evaluation Page 5 of 7 2.3 ANALYSIS EVALUATION continued A. PSB-1 Loading the station distribution buses, including all Class 1E buses down to the 120/208 v level, to at least 30%.
Response: Both FPL Turkey Points Units 3 and 4 were at approximately 100% power and the station distribution busses were loaded at normal load which is well in excess of the required 30%
loading. The measured bus loading are provided in Attachment 2.
B. PSB-1: Recording the existing grid and Class 1E bus voltages and bus loading down to the 120/208 volt level at steady state conditions and during the starting of both a large Class 1E and non-Class 1E motor (not concurrently):
Response: The voltages and bus loading were recorded down to the 480 volt level only. All low voltage AC (i.e., less then 480 volts) Class 1E power circuits and associated busses are powered by either the 125 volt DC safety related station batteries or by inverters supplied by the station batteries. Being independent of offsite power, these busses are not included in the computer voltage analysis and, accordingly, recording of actual voltages was not required.
The computer model calculates voltages based on bus loading and the electrical system impedance (i.e., resistance and reactance of feeder cable, transformers, etc.). As the electrical system impedance is constant for steady-state and transient conditions, the model can be utilized to analyze voltage drops due to steady-state running loads as well as instantaneous voltage drops due to starting transients. Accordingly, to verify the model, it was necessary only to measure steady-state conditions. Utilizing these steady-state measurements, the computer model was verified to be accurate.
C. Using the analytical techniques and assumptions of the previous voltage analyses, and the measured existing grid voltage and bus loading conditions recorded during conduct of the test ,
PSB-1'esponse: calculate new set of voltages for all the Class 1E buses down to the 120/208 volt level.
I As stated in this evaluation, this calculation was performed and the results are provided in Attachment 2.
L-92-204 Engineering Evaluation Page 6 of 7 2' ANALYSIS EVALUATION continued D. PSB-1: Compare the analytically derived voltage values against the test results. In general, the test results should not be more than 3% lower then the analytical results; however, the difference between the two when subtracted from the voltage levels determined in the original analyses should never be less then the Class 1E equipment rated voltages.
Response: The results of this analysis and the percent error from the measured values are provided in Attachment 2. In general, good (within 3%)
correlation between the analytical and test results has been achieved.
The analytical results aze all lower than the measured values except for Unit 4 busses LC A, LC D, MCC A, MCC D and MCC J which are all within 0.3% of the measured values. This difference will not result in any Class lE equipment being powered at less than its rated voltage. This is due to the undervoltage relay settings being conservatively set higher (to provide margin for future addition of loads to the Class 1E busses) than the minimum analytical result which was previously calculated (Reference 4.4).
Based upon the above, the computer model Ebasco Computer Program AUXSYS 4078 12/31/89, including inputs are concluded to be accurate.
3' CONCLUSION This evaluation in response to an NRC request (Reference 4.10) provided a verification by actual test that the computer model which was utilized to determine the undervoltage relay settings correctly models the as-installed field conditions Section 2.3 provided and evaluated the setpoints foz the undervoltage relays at Turkey Point Units 3 and 4. The evaluation shows that the computer model used for determining the setpoints for the undervoltage relays at Turkey Point Units 3 and 4 properly models the field conditions. This verification was done by showing that the field voltage measurements and computer calculated voltages (using equivalent field conditions when field voltage measurements were taken) are within 3% and do not exceed the undezvoltage relay setpoints. This complies with NRC Branch Technical Position PSB-1 (Reference 4.1).
L-92-204 Engineering Evaluation Page' of 7 4 .0 REFERENCES 4.1 Branch Technical Position PSB-1, "Adequacy of Station Electric Distribution System Voltages", Revision 0, July 1981 4.2 Test Procedure TP-788, "Electrical Measurements on Plant AC Systems to Validate Undervoltage Relay Setpoints" 4.3 Letter No. PTN-TECH-91-253, "Transmittal of Test Data for TP-788", dated November 26, 1991 4.4 FPL Calculation No. PTN-BFJE-92-022, Revision 0, "PSB-1 Voltage Analysis for Electrical Auxiliary System" 4.5 FPL Calculation No. PTN-BFJE-92-031, Revision 0, "Vezification of PSB-1 Computer Model" 4.6 Ebasco Calculation EC-145, Revision 5, "PSB-1 Voltage Analysis for Electrical Auxiliary System 4.7 Turkey Point Units 3 and 4, Updated Final Safety Analysis Report (UFSAR) Revision 9, dated July 1991 4.8 Turkey Point Units 3 and 4, Technical Specifications, Amendments 151/146, effective February 7, 1992 4.9 JPN-QI 2.3, Revision 4, Safety Classifications 4.10 NRC Letter dated August 16, 1991, "Turkey Point Units 3 and 4 Issuance of Amendments Re: Relay Setpoints, Fire Detection and Administrative Changes"
ATTACHMENT 1 Undervoltage Relay Setpoints for FPL Turkey Point Units 3 and 4
L-92-204 Attachment 1 "Page' of 1 FPL Turke Point Unit 3 Summar of Set oint Volta es 3A 3B 3C 3D Load Center ~3301 ~33 02 ~33 03 ~3304 480V Instantaneous 430 438 434 434 480V Inverse Time 424 427 437 435 FPL Turke Point Unit 4 Summa of Set oint Volta es 4A 4B 4C 4D Load Center ~4301 ~4302 ~43 03 ~4304 480V Instantaneous 435 434 434 430 480V Inverse Time 430 436 434 434
ATTACHMENT 2 Measured Field Voltage and Loading Values Versus Calculated Voltage Values and Percentage Difference
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L-92-204 Page' of 4 TABLE 1 Field Measured Bus Volta es and Loads FPL Turke Point Unit 3 Bus Voltage Bus KVA 4KV Bus A* 4136. 3 9642.7 4KV Bus A** 3825.7 4KV Bus B* 4152.1 8919.1 4KV Bus B** 5536.6 4KV Bus D 4119.5 333.9 480V LC A 476 75.8 480V LC B 481 73.4
,480V LC C 475 255.6 480V LC D 479 136.8 480V LC H 473 121.5 480V MCC A 475 81.9 480V MCC B 480 151.9 480V MCC C 472 153.4 480V MCC D 472 109.1 480V MCC K 480 1.8 High-side of current limiting reactor Low-side of current limiting reactor Bus voltage values are not available, as bus metering is only installed I
on the high-side of the current limiting reactor.
L-92-204 Page 2 of 4 TABLE 2 Field Measured Bus Volta es and Loads FPL Turke Point Unit 4 Bus Voltage Bus KVA 4KV Bus A* 4099.2 9809 4KV Bus A** 3291.3 4KV Bus B* 4109.7 8728 '
4KV Bus B** 5567.5 4KV Bus D 4085.9 331.2 480V LC A 471.6 69.1 480V LC B 477.2 182.1 480V LC C 474.4 390.3 480V LC D 475.5 30.1 480V LC H 473.5 160 ~ 9 480V MCC A 469. 8 92. 4 480V MCC B 475.0 110.7 480V MCC C 472.3 165. 2 480V MCC D 473. 2 160 ~ 8 480V MCC K 476.5 25.4 480V MCC J 469.8 23.5 High-side of current limiting reactor Low-side of current limiting reactor Bus voltage values are not available, as bus metering is only installed on the high-side of current limiting reactor.
L-92-204 Page 3 of 4 CALCULATED BUS VOLTAGES USING FIELD MEASUREMENTS Turke Poi.nt Unit 3 Calculated Percent Difference Bus Voltage From Measured Voltages 4KV Bus A* 4082 1.3%
4KV Bus A** 4056 4KV Bus B* 4085 1.6%
4KV Bus B** 4057 4KV Bus D 4055 1.6%
480V LC A 473 0.63%
480V LC B 477 0.83%
480V LC C 470 1.05%
480V LC D 476 0.63%
480V LC H 465 1.70%
480V MCC A 472 0.63%
480V MCC B 474 1.25%
480V MCC C 1.27%
480V MCC D 464 1.69%
480V MCC K 476 0.83%
High-side of current limiting reactor Low-side of current limiting reactor Bus measured values are not available, as bus metering is only installed on the high-side of current limiting reactor.
L-92-204 Page 4 of 4 TABLE 4 CALCULATED BUS VOLTAGES USING FIELD MEASUREMENTS Turke Po3.nt Unit 4 Calculated Percent Difference Bus Voltage From Measured Voltages 4KV Bus A* 4078 0.5%
4KV Bus A** 4053 4KV Bus B* 4085 0.6%
4KV Bus B** 4056 4KV Bus D 4052 0.8%
480V LC A 472 -0.08%
480V LC B 476 0.3%
480V LC C 471 0.7%
480V LC D 476 -0.1%
480V LC H 475 0.3%
480V MCC A 471 -0.3%
480V MCC B 475 480V MCC C 468 0.9%
480V MCC D 474 -0.1%
480V MCC K 475 0.3%
480V MCC J 471 -0.2%
High-side of current limiting reactor Low-side of current limiting reactor Bus measured values are not available, as bus metering is only installed on the high-side of the current limiting reactor.
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