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04/18/20220004

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A. TITLE: New Melones Powerplant Generator Rewind

B. PURPOSE: The purpose of this amendment is to incorporate the New Melones Powerplant Unit

1 Stator Winding Temperature Evaluation noted in Section J Att. No. 9 Pre-Proposal

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NSN 7540-01-152-8067 OPTIONAL FORM 336 (4-86)

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TECHNICAL SERVICE CENTER

D,enver, Colorado

Hydroelectric Research and Technical Services Group

-'1

.Project Notes 8450-2002-05

,New Melones Powerplant Unit 1 Stator Winding Temperature Evaluation u.s. Department of the Interior

Bureau of Reclamation

May 2002

Amendment 0004

AI

u.s. Department of the Interior Mission Statement

The mission of the Department of the Interior is to protect and provide access· to our Nation's natural and cultural heritage and honor our trust responsibilities to tribes.

Bureau of Reclamation Mission Statement

The mission of the Bureau of Reclamation is to manage, develop, and protect water and related resources in an environmentally and economically sound manner in the interest of the American public.

Hydroelectric Research and TechniCal Services Gr.oup Bert Milano, Manager

. (303) 445-2300

PO Box 25007, Attention: D-8450' Denver, Colorado 80225-0007

TECHNICAL SERVICE CENTER

Denver, Colorado

Hydroelectric Research and Technical Services Group

.Project Notes 8450-2002-05

'New Melones Powerplant Unit 1 Stator Winding Temperature Evaluation

Prepared by:

James M. 'DeHaan

Richard L. Becker u.s. Department of the Interior

Bureau of Reclamation

May 2002

Project Notes 8450-2002-05

New Melones Powerplant Unit 1 Stator Winding Temperature Evaluation

James M. DeHaan Richard L. Becker

Hydroelectric Research and Technical Services Group U.S. Bureau of Reclamation Technical Service Center Denver, Colorado

May 2002

ABSTRACT

Stator winding heating problems for unit 1 (and also unit 2) have been evident since both generating units at New Melones Powerplant were commissioned. Temperature alarms have occurred sporadically over the years at full load operation. The Hydroelectric Research and Technical Services Group (D-8450) began to investigate this problem in March 1999 following numerous unit 1 stator winding temperature alarms. We were contacted to evaluate the situation and to verify the temperatures measured by the stator winding RIDs. A followup field trip was undertaken in May 2000 to determine if there was a stator winding problem. The results of the investigation and related recommendations are presented.

DISCLAIMER

This written matter consists of project notes primarily for the Central California Area Office, the MP Region, and the Hydroelectric Research and Technical Services Group. Use of this material as part of or in support of advertising for referenced products is forbidden.

New Melones Powerplant Unit 1 - Stator Winding Temperature Evaluation

Backeround

New Melones Powerplant and the two General Electric Company (GE) hydro-generating units were constructed and put into operation by tho Corps of Engineers (Corps). Records indicate that the units were commissioned and put into service in 1979. The Corps and the Bureau of Reclamation (Reclamation) conferred on the generator design. The final design decisions were made by the Corps. Shortly after commissioning, the facility was turned over to Reclamation for operation and maintenance.

The nameplate ratings of the generating units are as follows:

Rating Power Factor Number of Poles Rated Speed Line Frequency Rated Stator Voltage Rated Stator Current Stator Winding Connection Rated Field Voltage Rated Field Current

.166,667 kV A 0.90

171.4 rpm

13,800 volts 6,973 amps 3 circuit wye

375 volts 843 amps

The generators, as specified, were to be capable of continuous operation at 115 percent of nameplate MV A rating. Therefore, the continuous rating of each generator is 191,667 kVA at rated voltage, rated powerJactor, and frequency. It is noted that the units have and are operated at 191,667 kVA at unity power factor.

Stator winding heating problems for unit 1 (arid also unit 2) have been evident since both units were commissioned (Appendix A- March 20, 1986, and August 4, 1986, memos). Temperature alanns have occurred sporadically over the years, and the Hydroelectric Research and Technical Services Group (0-8450) began to investigate this problem in March 1999 following numerous stator winding temperature alanns at near full load operation of 192 MW.

Stator Windine Temperature Alarms

Stator winding heating has been an issue ever since the units at the plant were commissioned.

Per the March 20,1986, GE report (Appendix A), the stator winding temperature rise exceeded 60°C (specified stator winding temperature rise at 100 percent rated, 167 MV A, load). In response, GE designed a system to close the gap between the rotor rim air shroud and the fiberglass air deflectors. This reduced the stator winding temperature rise to 56.4 °c at 100 percent load verified by a heat run performed on unit 2 in 1986.

From the limited amount of documentation available, stator winding Resistance Temperature Detector (RID) temperature alarms for unit 1 first appeared in 1986 (Appendix A- August 4, 1986, memo). At that time the alarms were attributed to higher than normal stator ambient air temperatures. The ability of the coolers to remove enough heat from the stator cooling air to keep the ambient air temperatures below a maximum 40°C was questioned. The recommendation was to closely monitor the stator ambient air when the units are near their full load capability. The stator winding RID temperature alarm-and trip set points were increased 5 °C to 105 and 115°C, respectively, following this incident.

These new alarm temperature points on unit 1 were exceeded as early as 1997 and continued through D-8450's involvement in March 1999. It was the general impression of the plant personnel that the stator winding RID temperatures were rising with time. We were contacted to evaluate the situation and to verify the temperatures measured by the stator winding RIDs. A followup field trip was undertaken in May 2000 to determine if there was a stator winding problem.

Generator Thermal Protective Relay and Alarm Settings

Appropriate temperatures to use in setting the alarm and trip points for the stator winding have been in question since January1986 (Appendix A- January 27, 1986, memo). The stator winding consists of coils insulated with class F insulation and installed with class B materials. Class B material typically includes the wedges, slot filler material, RIDs, and end-winding ties and braces. Following are several different stator temperature alarm and trip settings that could be applied to the New Melones units:

(1) The Corps of Engineers Operation and Maintenance Manual for New Melones Dam and Powerplant, dated December 1979, states the alarm point should be 125°C and the trip point 132°C.

(2) Stator winding trip setting left by GE following unit installation was 110°C.

(3) In general, the Bureau of Reclamation practice for class B insulation is to set the alarm at

95-100 °C and the trip at 110-115 °C.

The latest revision of ANSI C50.12 (1982) American National Standard Requirements for Salient-Pole Synchronous Generators and GeneratorlMotors for Hydraulic Turbine Applications (Appendix B) limits the hottest-spot total temperature (hot spot) I to 130°C for class B insulation and 155°C for class F insulation systems. This corresponds to a maximum observable temperature rise2 measured by RID of 75°C for class B insulation and 90°C for

I Hottest-spot temperature (hot spot) - The highest temperature attained in any part of the insulation of electric equipment.

2 Observable temperature rise - The difference between the observable insulation temperature and the ambient temperature.

class F insulation (based on an ambient temperature of 40°C). This results in a maximum observable insulation temperature3 of 115°C for class B insulation and 130°C for class F insulation. These RID values allow for a 15°C hottest-spot temperature allowance4 for class B insulation and 25°C for class F ins~lation. This allowance includes the temperature gradient across the insulation from the copper bar to the RID, and winding temperature variations.

Given these ANSI temperature limits, we concur with the Reclamation memo dated August 4, 1986, stating a stator winding temperature trip at 115°C, alarm at 105°C, and a stator air-cooler· discharge alarm at 40 °C for class B insulation. These settings have been in place on the unit since 1986. These values follow ANSI standard C50.12 f~r class B insulation in that the unit trip is set at 115°C. They are also in line with Reclamation's general practice. The values stated by the Corps are too high for class B insulation and are more in line with class F insulation temperature limits.

Stator Winding Heating Field Test Results

Initial field tests were performed by D-8450 in March 1999 at the request of plant personnel to investigate if there was a problem with the stator winding temperature monitoring system. No wiring, grounding, noise, or RID transducer problems were found that could cause the RID measurements to be inaccurate. In an effort to verify the RID readings, heat-sensitive tapes were attached to the upper and lower end windings. These tapes record the maximum temperature within ±3 °C. ~e unit was then operated over a period of several months before there was an opportunity to inspect and read these tapes. The tapes indicated temperatures in the end turns of the winding were exceeding the ANSI limit for class B insulation (115°C), with a maximum temperature that exceeded 121 °C. This was considerably hotter than the stator winding RIDs had indicated during this same period (about 102°C). [It is noted that during this time RID #15 that had been indicating higher than average stator winding temperature failed and is no longer functioning. Previous measurements made by this RID are suspect and the accuracy of these readings cannot be trusted.]

Given the temperature tape readings, additional field tests were performed in May 2000 to determine if these end winding temperature readings were accurate. Infrared surveys of the end winding areas were conducted to confirm temperature tape readings and identify any localized area(s) of heating. Concurrent with these measurements, stator winding RID and air cooler discharge temperatures were recorded during these tests. Phase and parallel circuit currents were

3 Observable insulation temperature - The temperature of the insulation in electrical equipment, which is measured in a specific way, for example, with a thennometer, RTD, resistance detector, winding resistance, or other suitable procedure.

4 Hottest-spot temperature allowance - The designated difference between the hottest-spot temperature and the observable insulation temperature.

also measured to determine if high stator temperatures were localized due to winding current unbalances.

- Infrared Monitoring of the Stator End-Turn Windings

Using an Inframetrics ThennaCAMTM PM280 infrared imaging radiometer, various areas of the stator end-turn windings were monitored in an attempt to locate an obvious source of the higher than nonnal winding temperatures. Temperatures were monitored at no-load, 50 MW, 130 MW, 150 MW, and 185 MW, and results can be found in Appendix C. Due to limited accessibility to the unit, only a small portion of the upper end turn area of the stator winding was monitored. We did select areas where the temperatures as measured by RID were the highest. More than 90 percent of the lower end turn area of the winding was monitored. The highest temperature noted was approximately 146°C. This was measured on the inside portion of the lower end turn near coil 90 during the 185-MW test. High temperatures were widespread on the lower end turns. Even though the winding insulation in this area is class F, these temperatures are a concern because they exceed ANSI maximum observable insulation temperature of 130°C for class F insulation. Appendix D contains several infrared reports detailing the temperatures observed.

The upper end-turn areas monitored with the infrared equipment did exhibit moderate temperatures (101°C). The temperatures observed in the upper end-turn areas are considered to be acceptable and are well below the observable class F insulation temperature limit of 130°C.

Please refer to Appendix D for the infrared report. The generator deck plates were removed to allow access for the infrared scann~ng of the winding. This may have altered the air flow pattern, and exposing the winding to the plant environment may have actually helped the winding cooling in these areas. However, this effect would be small and does not alter the conclusion that the upper end-tum area temperatures are acceptable.

Physical observations while making these measurements suggest that these high temperatures in the lower end-turns are the result of very low air flow in this area. Please refer to the infrared report .. The temperature of the winding as observed from the outside diameter appears to be substantially lower than winding temperature on the inside diameter. This suggests that there is insufficient air movement toward the inside of the winding as a result of not enough cooling air movement through the frame and wrapper plate. It is noted that the openings in the frame do seem to be smaller than have been observed on similar sized machines. A contributing factor to this problem could also be GE's redesign of the unit's cooling system when they closed the gap between the rotor rim air shroud and the fiberglass air deflectors in 1986. Any air flow that leaks out of this gap helps to cool the end windings, and by reducing this gap they possibly reduced the air flow and cooling in this area .

.., Stator Winding RID and Air Cooler Measurements

Stator winding RID and air-cooler temperatures were recorded concurrent with the infrared measurements. During this testing, unit 1 was brought up to the specified load (no-load, 50 MW, 130 MW, 150 MW, and 185 MW) and held at that load until the stator winding temperatures started to stabilize. Western Area Power Administration (Western) limited the unit's availability during these tests. Due to these time constraints, RID temperatures did not completely stabi lize before measurements were taken. This allowed us to obtain the temperature information within the operational time constraints set forth by Western. However, these tests do not meet the heat run requirements set forth by Reclamation and cannot be used to determine loading levels. The 185-MW load was the maximum load available given the water level of the reservoir during these tests. Test measurements can be found in Appendix C.

The RID temperatures were within 4 DC of each other for the no-load test run. Prior to this test the unit was off line and the winding was at a constant temperature. Thus, the RTD reading accuracy is about ±2 DC. Por the 185-MW load test (Ill percent of nameplate load), the maximum stator RTD temperature was 102 DC, with an average air-cooler discharge temperature of 29 DC. This is an observable temperature rise of 73 DC. Extrapolating the load data (see graph in Appendix C) to 115 percent of rated nameplate load results in a predicted observable insulation temperature of 105 DC. This is equal to the stator RID alarm level of 105 DC. For these tests the average ambient temperature was about 30°C at similar load levels and, therefore, a predicted observable temperature rise would be about 75 DC. This is equal to the observable temperature rise limit of 75 DC set forth by ANSI. It is important to note that if the ambient temperature was to increase to 40 DC the observable insulation temperature would be 115 DC, which is equal to the stator RID trip level.

- Parallel Circuit CUlTent Measurements

The 3-phase generator stator winding consists of three parallel circuits per phase. 44 coils per circuit winding, and a total of 396 armature slots. Under normal operating conditions the phase current splits "fairly evenly" between the three parallel circuits. Unbalanced currents wou ld result in unbalanced heating of the stator and could be a source of high stator RID temperatures.

Nine parallel circuit currents (Ial, Ibl, etc.) were monitored during the load tests. Test results are contained in Appendix C. They show that the parallel circuit currents remain fairly balanced with a maximum measured deviation at 185 MW of 2 percent (53 amps out of an average current of 2547 amps). Stator temperature rise is roughly a function of stator current squared. Given this relationship, a 2 percent current deviation would result in a 4 percent temperature deviation.

At 185 MW this would result in a 4 °C temperature variation. A 4 °C parallel circuit temperature variation is fairly insignificant when compared to the hottest-spot temperature allowance of 15 °C for class B insulation. Thus, the slightly unbalanced circuit currents are not a contributing factor to high stator RTD temperatures.

Generator Electrical Discharge Damage

Signs of electrical discharge acti vity were noted in several locations around the unit in the end turn areas. These discharges are not related to high winding temperatures observed. Photos 1 and 2 show a white powdery residue resulting from electrical discharge activity between coils.

The electrical discharge area illustrated in the photos appears to be typical of the damage observed. Electrical discharges are occurring where there is insufficient space between adjacent coils of different phases. The discharge area shown in the photos is occurring between the front coil halves located in slots 92 and 93. Please refer to the winding layout included as Appendix E.

The coil in slot 92 is the A phase line-end coil, and the coil in slot 93 is a C phase coil , 17m from the line end. The voltage difference between the A and C phase coils is sufficient to cause electrical discharge acti vity in this area.

PhOto I-Circle and arrow indicate the area of electrical discharge between front coil sides in slots 92 and 93. Coil in slot 92 is a line-end A phase coil, and coil in 93 is number 17th from the line-end C phase coi I.

HW-oric Stator Windine Temperatures

Photo 2 -Closer view of area of electrical discharge between coils in slots 92 and 93.

Following the field tests, heat run test data were made avai lable to us by the regional office.

These data, for both units, were recorded in 1982 and 1986. Heat runs in 1986 were performed at 85 100, and 110 percent of rated nameplate load on unit 2 with a resulting obscrvable insulation te~perature of 81.7 DC, 93.9 DC, and 99.7 DC, and an observable temperature rise of 53.4 DC,

56.4 DC, and 65.7 DC, respectively. Extrapolating these data to J 15 percent of rated nameplate load (see graph in Appendix C) results in a predicted observable insulation temperature of 102°C and a predicted observable temperature rise of about 68 °c (ambient temperature of 340C). It is important to note that given this temperature rise data, an ambient temperature of

40 °e would result in an observable insulation temperature of 108 °e, which would activate the stator winding temperature alarm.

Examination of historic stator winding temperature data (1997-present) provided by plant personnel indicates that unit 1 typically approached the stator RTD alarm point of 105 °e when loaded to 115 percent nameplate load of 192 MW. Ambient air temperature information from this time period is not available, but the 1986 heat run test data indicate it is about 35 °e at this load level. Using these numbers the observable temperature rise is 70 °e. This correlates well with the 1986 heat run data. It also indicates that unit 1 runs about 5 °e below the 75 °e observable temperature rise limitation for class B insulation.

From GE's preliminary test procedures (see Appendix A - Retest Procedure dated 11-15-1983) it is also evident that as a result of their redesign effort GE was concerned about the temperature rise of the ring bus and end heads (end windings) at both the top and bottom of the stator. From test data attached to the March 20, 1986, report, GE measured the temperature of the ring bus (25 - 38 °e) during a rated current short-circuit heat run test but did not measure any end winding temperatures.

Conclusions

Stator RTDs are functioning properly, and the observed insulation temperatures are correct.

Parallel circuit current measurements indicate the winding currents are balanced and are not the source of high winding temperatures as recorded by the RTDs. Infrared monitoring of the upper and lower end turns also shows that the winding temperature was fairly uniform and that any perceived high temperatures as recorded from the RTDs could not be attributed to a localized winding problem.

However, infrared scanning did show excessive heating in the lower winding end-turns. There appears to be insufficient air flow across the lower end-turns. As a result, the end-turn temperatures are exceeding the observable class F insulation limit of 130 °e set by ANSI. The heating observed is not a localized problem and appears to extend around the lower portion of the unit winding. The upper end-turn area was much cooler and does not approach the 130 °e limit.

Exceeding ANSI temperature limits increases the risk of an insulation failure. Failure of the insulation in the end-turn area could lead to a phase-to-phase fault in the generator, which would be very destructive.

Analysis and extrapolation of historical heat run data along with temperature measurements made during field tests indicate that operation at 115 percent of nameplate rating (191,667 kV A at 0.9 PF) will result in an observable insulation temperature that approaches, or meets, the stator winding RTD alarm temperature of 105 °e. These data also show a slight increase in observable .

insulation temperature from 102 °e in 1986 to 105 °e in 2000. The resulting observable temperature rise varies from about 70 °e to 75 °e, respectively. This is a small increase and is not indicative of a stator winding problem.

Recent sporadic stator winding temperature alarms are likely occurring because, as discussed above, this unit at full load operates very close to its observable temperature rise limit. Thus, fluctuations in the ambient air temperature, and to a lesser extent the repeatability accuracy of the RID monitoring system, cause the observable insulation temperature to occasionally exceed the stator winding RID alarm set point. Ambient air temperature (air-cooler discharge temperature) becomes a controlling factor as to whether or not the observable insulation temperature of 105°C is reached. Data also show that if the ambient air temperature was to increase to 40 °C (the upper limit per ANSI), the observable insulation temperature would be about 110-115 °C.

This is very close to, or meets, the 115°C limit for class B insulation set by ANSI and also the stator winding temperature trip level.

Recommendations

The following recommendations address the three major unit 1 winding problems as identified in this report. (Recommendations are also applicable to unit 2.) The recommendations under each heading are for that specific problem and do not apply to the other problem areas.

Stator Winding RID Alarm Problem - Addressing this problem first involves making sure that the air coolers are operating at their designed performance level. To accomplish this a thorough inspection and cleaning of each cooler is required. This involves disassembly of the coolers, checking for and removing any obstructions, and cleaning each cooler tube. Monitoring and recording the air cooler performance would also be very beneficial. At a minimum, the ambient air-housing temperature needs to be recorded and trended. In addition, it would also be good to record inlet and outlet water temperatures and the inlet and discharge air temperature of each cooler. Constant monitoring and trending will help identify any changes that could affect the unit's continuous full load rating.

Following this air-cooler maintenance, a heat run at 115 percent rated nameplate load (192 MW) should be performed. From the historical documents we have received, a heat run at this load has not been performed. Because the units at New Melones operate very close to the observable temperature rise limit set by ANSI, it is important to accurately measure and document the observable insulation temperature, ambient air temperature, and the resulting observable temperature rise.

These heat run data can then be used to determine if the unit can reliably be operated at the 115 percent nameplate rating (192 MW) without nuisance stator winding temperature alarms. If, as past experience has indicated, there is a reasonable chance that the observable insulation temperature could activate the stator winding temperature alarm, plant and/or regional management will need to decide which of the following two options to pursue:

OPTION A -Allow the observable insulation temperatures to reach, or exceed, 105°C.

The stator RID alarm settings would need to be increased about 5 °C above the maximum observable temperature rise measured during the heat run plus 40°C (ambient air temperature limit) to avoid nuisance alarms. The stator RID trip level would also have to be raised by the same amount. Under this option, the stator winding, class F insulation, would still be well below its observable insulation temperature limit of 130°C. However, the materials used to install the winding (wedges, slot filler material, RTDs, and end winding ties and braces) are class B and would be subject to temperatures that approach, or exceed, their temperature limit. Hotter temperatures shorten the life of insulating materials. The industry rule-of-thumb is that for every 10 °C rise the expected life is cut in half.

OPTION B - Lower the 192-MW generator continuous full load rating until the observable temperature rise plus 40°C (ambient air temperature limit) reaches a maximum temperature of about 100 °C. This would allow the unit to operate 5 °C below the stator winding temperature alarm point and well below the class B insulation temperature limit of 115°C set by ANSI.

Evaluation of these two options would involve an economic analysis that weighs the risk of shortening the life of the stator insulation (operating the generator at or above ANSI insulation temperature limits) versus the loss of revenue from lowering the generator full load rating (operating the generator below ANSI insulation temperature limits).

Stator End Tum Heating Problem - The heating of the lower end turns needs to be addressed. It is suggested to conduct an infrared survey of unit 2 to determine if heating patterns are unique to unit 1 or apply to both units. Air flow measurements would need to be taken to determine if supplemental air handling equipment or modifications are needed to provide cooling to the end tum area. The addition of supplemental fans in the air housing to increase air flow in the lower end-tum area is one possible solution that could be verified during these measurements.

Stator Winding Ramp Test and Inspection - A DC ramp test and visual/physical inspection of both units is also recommended to better evaluate the general condition of the winding insulation.

This inspection should be conducted per guidelines in FIST Volume 3.1.

Generator Electrical Discharge Damage - Stabilize and eliminate further electrical discharge activity and the resulting damage by cleaning the affected areas to remove the residue as best as possible. Then, pack the space between the coils in these areas with filler material (Dacron felt soaked with polyester or epoxy resin), lashing the filler material in place.

Appendix A

Historical Reports, Test Procedures, and Memos

/1

83-11-15

NEW MELONES

RETEST PROCEDURE

1. MODIFICATIONS

X

(a) De~ermine runou~ of angle iron seal on rim by ro~ating unit a~ lo~ speed on high pressure oil.

(b) Add ~ex~olite s~rips at 1D of shrouds to reduce clearance between seal and shroud to minimum determined by slow rotational check.

(cl Seal space between rotor covers and insid~ of rim to eliminate air leakage in this area.

(d)

(e)

(g)

TESTS

(a)

(b)

( c)

(d)

Baffl~ off scallops between poles in rim plate at top and bottom at: rim.

Seal up any other air leakage paths in both rotor system and stator. such as leakage around air cooler supports.

Place thermocouples on circuit rings and on stator bar endheads (at both top and bottom of stator). Perform short circuit heat run. record temperatures. air flow and air pressures under the shrouds.

It excessive temperatures are observed. steps will be taken to improve ventilation in this area by addition of batfles.

Conduct full load heat run to confirm that stator and field tem~erature rises do not exceed guaranteed limits with modified air flaw.

Uncouple generator frofu-turbin~.

Perform retardation runs to determine generator windage friction loss.

Recouple generator and turbine.

LV4fj2 -==--/ -- -

. Q: SLC

~- ~ t1~ J. M. QUlgley .

Supervising Engineer.

Electrical Engineering.

Engineering-Genera~ors.

21219-785-2572 MELONES POWERPLANT

United States' Department of tbe Interior

BUREAU OF RECLAMATION

IN REPLY KP-462

REFI;R TO: 651,.

MID-PACIFIC ItEOIONAL OFFICE

, 2800 COTTAGE WAY

SACRAMENTO, CALIFOR.NIA ~S8lS

~ 2 '11986

. D. A. D~uuis, Chief Constructlon-operatloDS Division Department of the A~y Sacrameu~o Division, Corps of 'Engineers 650 Capitol Hall Sacrameu~o, CA 9S814

Dear Hr. Dennis:

'Questions have been raised regardlag the appropriate temperature to use in setting the a1arm aud trip points for stator winding t'e..perature relays of the New Helones Geuerators supplied under your contract DACWOS-76-C-OOSl with the General E1ectric Company (CfE) •. Paragraph 2-6.3 ~f the contract specifies class B insulation. ANSI Stau.clard CSO.12-196S, which was in effect at the time of manufacture, states ~he limiting observable temperature rise for class B insulation as 60°C above 40°C ambient for the type of geo.erators at New Melones. The 1982 revision of ANSI CSO.12'raises this temperacure to 7Soc. The Corps of Engineers Operation and Maintenance Manu4l for New Ke10nes Dam aud !owerplant, date De~ember 1979, on page 11-4-37 says the alarm point shoUld be 12SoC and trip point 1320 C but the tr~p sett~ns aw left by GE during ins~allat1on. ~as 110oC.

Infor.al d1scu$s1ou with GE indicates the stator coils ~ay ~ actually be class F insulation, but the wedges may be ~lass B.

If the ma'teria1s used were predolll1.nL4tly class P, it may be lIlore app~opr1ate to fol1ov the 1982 revision of ANSI CSO.12. Ve would appreciate your assistance in determining the actual class of the winding .aterials used and the,.axim~m11mlting temperature rise recommended by GE. Please reply to the attention of KP-460.

Si7e11, ,:1 / ;;{/;Wn4G IdI~ ,"

I '

LAWRENCE, F. HANCOCK

, ACTING REGIONAL DIR~CTOR

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~:.~.""~'" , ." >:<'~'~:~f:0~':':' .. " ~{:

March 20, 1986

Work Order M6-025 G.E. Unit Modification & Test

On Febru~ry 24, 1986, Don Scranton Ca G~neral Electric Erection Engineer) and two mi+lwrights· arrived at the job sit.e to install ventilation baffles· on the upper air shrouds to increase self cooling capability of the test unit. (Melones Unit 112)

During initial heat· runs and efficiency tests of 1981, it was necessary to remove all air flow calibraticg plates between the rotor spider arms on the upper and lO"tver ends 6f the arms. This was found to be necessary to limit temperature rise to 60°c during the 100% rated heat run. With all air plates removed, the losses attributed to friction and windage were excessive and the guaranteed efficiency was missed by 0.16 of 1.0% or by Dppr~ximotcly 65 kilo wntts.

General Electric Co. designed· a system to be installed to block air flow escapement by closing the· gap between the rotor rim air shroud, and the· fibre glass upper air deflector. This gap was reduced from approximately ·3/4" to a nominal .3/8". Also, strips of 1/8" plate were welded along the rotor rim and rotor iron to close air gaps in that area.

Af·ter the modification was complete, the test engineer arrived on the job site to set .uP .for heat· runs·. Heat runs were made at . iOO%, 110% and 85% rated load. The 100% heat run required transformer tap setting changes on KIA & K2A from tap il3 to tap III in order to. under excite· Unit III sufficiently to :p.rovide r·equired reactive load to Unit 112 for the heat run at 100% KVAcapacity rating.

Sta·tor air cooler discharge valves were all throttled evenly to ~rovide uniform air housing ambient temperature to about 37°c and all air deflector calibrating plates were eventually replaced between the spider arms.CUpper· and lower) The 110% and 85% heat runs followed the- 100% rated heat run~ Heat runs began on March 8 and .were finally completed on March ·12

A short circuit heat run was performed on March 13 for seven hours.

The purpose of this run was to measure temperature rise of ·thering bus.

This tes t was requested· by General :Electric Compa.ny.··

After the sha"rt.circuit·heat run was complete· on March 13, the contractor removed· his ·instrument transformers, thermo-coupler and all instrumentati<:Jn except· his cot:lnection to the speed head in. preparation for retardation. runs to measure friction and windage ..

Bulkhead gates were installed in Unit #2 and the uriit was placed on an un-watered cl~arance. Station service was transferred to the P.G.& E. stand-by supply'and a clearance was issued on K2A, 13.8 Kv Station Service Breaker 224 and Station Service Bus 112 Feeder Breaker 52A to set up the three temporary 15 Kv circuits required for the retardation runs, At 2100 on March 15, the plant was shutdown 'and U,nit III was put on clearance to·finish 15 Kv'connections. Retardation runs ·continued through the. night; completion of 'tests and restoration of 'equipment continued until 0730 on Marcil 16,1986. -:

On Monday, March 17 U.nit 11.2· was watered ,up and' the clearance removed by 1600. The unit was ,'returned to commercial operation at t800 hours.

General Electric personnel spent the next few days packing their equipment for shipment an,d left the facility on . March 24, 1986.

A co~y of the heat runs and retardations runs are attached.

cc: Bud Pel=ry /MP-46 2 Planning/T-170

A// '~ ~.L--T/j~~~

Stuart L. Arwood, Chief Melones/O'Neill Power Branch

7-1654 (11-94) COMPUTATION SHEET

Bureau of Reclamation

BY PROJECT

OF

CHKD BY DATE FEATURE

M ... -f

DETAILS

Fvl} LeNI.d. = } (7 /1 V,4 pq+e/ Y. /,.1 e .9PF J'1a)(. '0 ~5~, ... tlt: II "'''4J~ () bfrf~/'/~

"..." I ~ • .J_", -,; ... ,., .. .,.,. AWI},,; .. ,.t ky. -r;.""rf,.n/~ !(/~.

0" ~TD)

}/14/8'.1 J /)1) Y. 1J.9.'C . "3 7. S-~C ~{'I./·C Of) 1)0

J/"I ,?.( I/IJ;/. 99.7·C ?Ll.Odc.. bJ.7"c.

11 JJ

1/11 /9'.1 8'~y. 8/, 7 Dc.. 28·1" (, ~J.I.J" C

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08/22/2000 10:33 209-785-2572 MELONES POWERPLANT

~(A'r~"":~'::~'~'~,~'~'f-" .. ~:'::' /~>:··:t~~~~~'~ '';:~~~~'~,' ') . : .... ?., DEPARTMENT OF THE ARMY

SACRAMENTO DISTRICt, CORPS OF ENGINEERS

6!50 CAPITOL MALI..

SACRAMENTO. CAUFORNIA 95a14

III.C"~" TO

... TTCNTION OF July 11, 1986

EPA GRANTS BRANCH

SUBJECT: Contract No. DACWOS-76-C-0051, Hydraulic Alternating Current Generators, New Melone California '

Bureau of Reclamation Mid-Pacific Regional Office

ATTN: MP-460

'2800 Cottage Way Sacramento, California 95825

Gentlemen:

r 1IVf1~\60F REClA'-'''T:Oii ' , .. ~"it:lA\. FIl E cOPY

~ O\iEfr'ff~us e , '/ JUL 151986

The enclosed Disposition Form CMT 2, dated 21 March 1986" is -the reply to your letter, copy enclosed, dated January 27, 1986, regarding the appropriate temperature rises to be applied to the

- stator windings of the New Melones generators installed under 't.he above cited contract. I trust that this information will provide the necessa~y data for your operational needs.

If you have any fUrther questions, you may contact Mr. Louis Tauber of North Pacific Division, enerator de'sign agent, at the telephone number listed t number ;ne.

Enclosures ttO'ilCL: IF '1I):.i ~:lACk ENCLOSURE p\.E.ASE. tHSE.lll"

CODE HO. ~

INlTlAL_---,- DAlE-------

""'-r!P<:;....-on. De n n i 5 Chief, Construction-Operations

Division

LL/'f(L k S~g-i .. i~TG-=~5S7 ·-(,70( c c

NPDEN-HD (SPKCO-E/S Feb 86) SUBJECT: Contract No. DACW05-76-c-OOSl, Rydrau11e Tu~bine Alternating

Current Generators, New :-1elone9 PoW'crllouBc. C;l.11tornia

-'1'0: SPKCO-E FROM: Ch, NPDEN-HD DATE:" 21 H2r 86 CMT2 'rauber/dc/3a IIS

1. We hll.ve the rolla.dng cQlD.Ii1ents to Mr. Denni.!l' letter of January '2.7, 1986 discussing the maximum allowable tcmpernture r1~e for the N~4 Me1oneo Gcner~tor8. With the i88u~nce or the 1982 ver3ion or ANSI C50.12 .Requi!"ements tor Salient-Pole Synchronouo OeneratoX's and Generatcr/Motors for Kyc1rau11c Turbine App11eat;iona" a change Wz,s !:Jade!n the manner'ot:

generator nmcep~ate r~t1ng. The 1965 version specified th~~ at lOO~ ~enerato~ rating, temperature rise above 40·c ambient could not e~ceed 60·c. It aleo pe~1tted generator ope~a~1on at 115% o~ n2meplate but did not li=1t maximl~ te:ape.rature rise unc1er that cOhdi tion. 'i'he 1982 vereion of A.."'SI C50.12 established a single unit rating on a continuous c1ut~ bas~s. Since this n~~ ra~~ng correBpor.~ed tQ the earl!e~ l!5% rating ro~ which no part~cul~ temperature rise W83 sped,ried, nev tempe::'at:ure rises above 40· C ambient were listed as 75 _. c: 'tor class B and gO· c t'or cla51i P insu12.t1on3.' The temperature rises selected tor ~he atand3:d were chosen as Tepresentative values which ~ou1~ be c:ons1sten~ vlth ~ne c1esign ot: ~he exis~ing 11~ulation OY3tems. -~n eotabl1~~~ns these temper~ture ~i~es an ~~owance (or nhot-spot~" of 10·c ~as ~ide and is included in the 75·c r~se~ This rise wou1d ~e seen by embedded detectors as a ga:imum t~,e~ature o~15·c + 40·c = 11S·c. To allow ~or detecto~ v~iations, p~ae:!ee at Cor~s of Enginec:s Prcj~cts has been to eet the a1~-m point at lO·c abovc the eon~inuo~s dut~ ~~ teQpe~ature (125·c) and to sct ~hc trip point at 1 - 10·c ~hove the alarm ;>\ point (132- to 13S·c). Di~cugsions betwee~ ~. Joe Quigley o~ C2n~~1an General Electric and ~. Lou Tau~er oC HOC con~i~ t~e settings ot 2.l~~ at 125·c and tr1~ ~t 132·c. Tha 110·c t~ip point set by O~ is too low •

2. The Ncw-P.elones class B windings consist of coil~ i~sul~~ed with elase ;< P insulation and insta1~ed ¥~~h c2ass B materi~3. The u:e or class F coil~ in clasD P ~nd class B windingB is a mat~er ot' eanu!ac~~in~ eeono~y. The prcsence of claso F eoila does not necessarily mean that the winding =~y be o!)c:oated at higher' than rated tempc:.:oatures a:in;:e the. cl~o B t:lateri2...l.s may be a~ve~gely affected and cause ,rematU::'evi~ding fai1ure~ Hoyeve~, as diseuesed 1~ pa:agrapn 1, the vindi~gs should oe continu~uD1J ope~ablc at 7S·c rise. To operll.te the mach1r.e at h!gh~ t~pc~at~e9 would reQui~e a detailed study including st~uct~~al l!~i~atious (shaft limit~ticns. etc.)

an~ cap~bility ot anc!ll~y e~uipment.

3~ Should'ycu have rur~~c~ ques~1cns, ple~se ~ee1 tree to contact ~~. Louis ~~uber ct HOC at (503) 221-38~5.

Enc~ nc GLENN R. I'IEI.OY > P. Eo • Ch~er, B7d:oelect:ic Design Center

08/22/2000 10:33 209-785-2572 MELONES POWERPLANT PAGE 05

. .;~ .;;r -

IN REPLY

REFER TO:

United States Department of the Int.,~.r~Ql{l ,Vr ~.:<:;~-.

- ". • ... i:>l<C' .' I.... To

:\ I:"\I'\~ ~ ~

BUREAU OF RECLAMATION . . "--r-'Bl -

MID-PACIFIC REGIONAL OFFICE , -.---~

2800 COTTAGE WAY ..L ••..• I ,

SACRAMENTO, CALIFORNIA 95825-l898 I ..

MP-463

651.

AUG ~Y2i&E.~~~ .-'2~ __ ~.~ " ; .--.----;-.--- j j~ .J~

To: ~s~~~oject Superintenden~, Tracy

I ACT ICH Tt~Nr NA

DATE:

--.. 'IIC'C- ~.-~-• ....__..-...... _-'

From; Regional Director

Subjee.~: New Melones Generator Operating, and MaxilllUlU Stator Telllperature Lim1tat1ol1s-New Kelones Powerplant Central Valley Project

As discussed wi~h Ivan French and Larry Ball of your office, we recommend lifting ~he megawatt limicatlon imposed by your office follOWing the incident where abovenorlllal stator ambient air temperatures were e~perienced on June 24, 1986. ~e believe the above norlllal temperatures you experienced were due to operational errors rather than a winding problem.

Some questions still r~m.ainregarding the ability of the coolers;;

to remove enough beac fromthestat.or air to keep the ambient;~;

rempera.tures . a.t ·or below·· Dormal. The stator·ambient'air;~) temperature sbould be closely monitored yhen the uni:ts near their full load c.apability in the likelihood that their is a problem vich the coolers.

The Corps of Engineers (Corps) have replied to our lette~ regarding the maxi mUla stator temperature of the New Melones -Units (see enclosure). According 'to ~he Corp6-the stator windings may be operated continuously with a 7 SoC temperature rise; over a 40°C ambient. This equates to a llSoe maximum allowable stator temperature. Since this maximum 1s SoC higher than we anticipated ve recommend adjusting the generator thermal protective relays as follows:

Relay Designation Function Old Setting New Setting

49Gl,49G2 Trip llOoe llSoe

49Gl.49G2 Alarm lOOoe lOSoC

P149S.P249S Trip lOSoC llSoe

26S Alarm 4Soc 40°C sic; ;'6"- /I,,. ~~O'~ ...

We vill follow up these relay changes with a aelay Change Order con.firming the chauges have beeu aade as soon as the n'ew Relay Data Sheet S,stem. has beau 11D.pleaented. If you experience any further .problems, please contact Dan Netto at FIS 460-5281.

Enclo8ure cc: Chief, Cen.tral Valley Operations Coordin.ating Office (with· enclosure)

AppendixB

Stator Winding Temperature Standard

AMERICAN NATIONAL STANI>A RI> (,SO.I1·I9X1

Table I Limiting Ohscr,ahie Temperature Rises of Indirectly Cooled Salient-Pole Synchronous

. Generators and Generator/Motors for Hydraulic Turbine Applications

Item

,\t:u:hinc I'a rts

Armature windin~' 7000 vol ts and less nver 7000 volts throu!!h 15 000 vults nvcr 15 000 volts

Field wind in!!

Collector rin):s

Corcs and mech:mical p:IIU in cllnt;let with or :Illj:lcent In insul;ltiun

~tethod of Temperature Determination embedded dele'tor' embedded detectur:

embedded detectm:

resistance thermometer thermometer or detectur

Temperature Rise ('C)

Oass 1\ Cbss F

80 100 +-is 90

70 85

80 100

85 85 nol 10 cxeeed the value for the associated adjacent insui:ltion'

5 Mbcelltineolls parts (~uch :u amoitisscur windin)!s. rotor surf'lce. brushhulders. brushes. etc) shall be permit tcd to attain such temperaturcs as will not injure the machint! in any respect.

'The ten'l'erature rise limits listed arc for insul:llion systems with thermosetting matcrials. Fur thermul'lastk materials the temperature rise limit shall be 70"C.

'Emhedued detectors arc localed within the slot of the muehine ami can be either resistancc elcments ur t hermocou plcs.

1 \\11cn core tcmperatures arc measured ;1\ the out~idc diameter of t 1e core, the Iimitin!! ~emper;ature risc shall be SoC less than the Iimilin)! Icmperature risc for the associated anuature windin!! insulatiun. .

4.2 Armature Voltage Rating. Prefcrred armature .v e a~c ratings ar.::

~ 400 volts 4 .160 volts 4 HOO volts

NOTE: Vt'It:I~es above 13 800 volts Ill: be desir:lble in m,l chines of I:If(!e capacity. Such t:HgC 11 . chines arc usually can nectcd directly to their own step-u ransformcrs and voltaj:e i5 selected un the ha5is of ccontll1 .. and technical considera tions.

Intermediate ratin~s twecn 6lJOO and 13800 volls may he desirahle to if erfal:e with othcr cquipment.

4.3 Power Factor ating. Prcfcrrcd powcr factor rat-

5,0.90, :lI1d 0.95 (allllvcrexcited);

4.4 Exci tion Voltage Rating. Preferred cxcitation

v(;ltage for ficld windings arc 62;5, 125.250,375, and

,500 reet voltagc, These preferred excitation volt:tgcs do ot :tpply to gene rators of the hrushlcss type with

Hel:t·conneclcd exciters.

..; 5, Tcmpcra:ures and Tcmpera turc .Riscs

5.1 General. When designing gellcfatms m ~ellerattJr/:

motors tOlllcct the.temperature rises shown in Tablcs I :lI1d 2, it is inlcnded that thc hottest.spot total tem·

102.3 pcr:tture should not qceClJ 130°(, for Class B "111(\

I S5 6C for CI:tss F insulativn systems. (The Class U'in.

sulation system applies to both indirectly .lI1d dire..:tly ctloleu ma..:hines, while the Class r: insulatitln sys'telll applies only 10 indirectly ..:tloled m:tchit1es.)

L.llge machines h:lve a si~ni ti"::lI1t thcrm.1I )!ratlkn t betwcen'th.: hottest spot. whkh is usually not mea.

surahle, anti the tlbservetl temperatltr.: as me:tslIlI:d by tJe'tector. lIowever, the m:tl:hines I:overeu hy this st :111· dard arc nHtximul11-rated at Ihe tCl11per:ltllr.: rise spe..:i· tied anti should he op~rated within th.: limits of the applkable I:ap.thility curv.:s. It shtluldnot he aSSIlt1h:tI thatoverlo:lding cap:tbility is av:tilahle if maximlllll per.

missible tcmperatures arc not re:tt;hcd ott rated kVA or hmsepowc r.

For maehincs that arc suhjet.:ted tu fre1luent t.:ydit.:

loading or arc st.lrted morc frequ.:ntly th:ttl twi~'l' pl'r day, considcration should he given to reducing thl.' tl'llI' peralure rises shown in T'lh1.:s I and ~'hy SoC til 10"("' sincc these conditions represent:t mtlre SCv.:rc duty than normal.

Unlcss othcrwise spcdlicd, :111 ma.:hines sh.tli bi! sup plied with cmbcdded tcmpcrature detectors, in act.:ll[· d:tncc with the requiremcnts Ilr ANSI (,50.10·1l177 .

5,2 Indirectly Cooled Machines. Tit\.' tlbsl'rv.thk' Il'lll' peratur.: rise of cadi tlr the P:llts lIf Ihe m:lt.:hinl' ahllVl' tlte temp.:rature of the cooling air, referred Itl as the cold air h:mpcr:tturc, shall not exce.:dlhe values ~iv':l1

G-7

" '" ~ '. •• - .. - ., ':"1" '----rr

A~IFRI(,"1" NATIONAL STANIlAi{1l csn.12·1'J82

Itcm

Table 2 Limiting Observnble TCll1perntures and Tcmperature Rises of

Directly Water-Coo:ed Salient-Pole Synchronous Generators and Generator/Motor for Hydraulic Turbine Applications

Coolant alld I>\:u:hine P"rts entd eoobnt

Dirc,tly ,llokd :IT!l1aturc windin~s

Dire,tly cO(lled field windin~s

Core and mechanical parts in ,ont:II:t with or adjacent to insul:ition

Collector rin~s

Method of Temperature

Determination

Detector or Thermomcter'

Coolant J

45-·50' (temperature)

55··50' (temperature rise)

55--50 .

(temperature rise)

85-80" \ (temperature rise)

(temper:lture rise)

6 Miscclbneous P:HtS (such as :lIllortisseur ·indin~s. rntor surface. brushh()lders. hrushes.