minimum oil pressure of 220 pounds per square inch available at the pistons and are designed to move the wicket gates a full opening or closing stroke in 5 seconds under the maximum head, including water hammer, on the turbine of 920 feet with this minimum oil pressure. An automatic mechanical gate lock is provided on one of the servomotors to secure the gates in the closed position upon shutdown of the unit.

The gate lock is operated by oil pressure through the governor gate lock control valve. An interlock switch is provided to prevent starting the unit until the automatic gate lock is in the unlocked position.

A depressor system is provided for lowering the water level in the draft tube below the bottom of the runner when the unit is being motored on the line. The unit should never be motored unless the penstock butterfly valve is open and the spiral casing is full of water, because of the need for providing cooling water to the turbine runner seal rings. Wicket gates leakage water is needed to cool the runner seals; otherwise they will heat up and the runner may seize. The depressor system consists of a main control mounted on the main control board, two pilot-operated 4-inch valves, two 2-inch solenoid valves, two float-operated switches for controlling the compressed air supply, and control switches operated by adjustable cams on the restoring mechanism in the governor actuator cabinet. One of the 4-inch valves opens initially to admit compressed air through the turbine head cover for lowering the water level, and one 2-inch valve admits sufficient air through the shaft and runner snorkel to maintain the established water level below the runner. The other 4-inch valve is automatically opened to exhaust air to the atmosphere upon initiation of a shutdown while the unit is being motored. This permits the water level to rise so that its braking effect on the runner can be utilized to stop the unit. The 4-inch air vent valve is also controlled by means of a cam-operated switch in the governor. Initially the cam is designed and set to open the air vent valve from 0 to 15 percent gate. Cams can be cut to open the valve at any desired range of gate positions in addition to the 0 to 15 percent range. The other 2-inch valve admits atmospheric air below the runner at certain gate openings to improve operation of the unit if required. Opening of this valve is controlled by a cam-operated switch in the governor which is set initially to open the valve from 0.5 to 0.6 gate. Cams can be cut to open this valve over any desired portion of the full gate operating range.

276. Governors. (a) General Description. --The governors for regulating the speed of the turbines are of the oil-pressure, cabinet-actuator type with electrically driven speed-sensitive elements. The normal operating oil pressure will vary between 270 and 300 pounds per square inch. The portion of the governor system subject to pressure was designed to withstand 300 pounds per square inch.

The governors were designed and furnished by the Woodward Governor Co. in accordance with the requirements of invitation No. DS-5538.

A stationary air compressor with a capacity of 20 cubic feet per minute at 350 pounds per square inch air pressure, with connecting piping, is provided to add air to the pressure tanks of the governor system.

The governors are rated at 280, 000 foot-pounds which is the combined capacity of the servomotors of the turbine. The servomotors are designed to operate the turbine gates through a complete closing or opening stroke in 5 seconds with a minimum effective oil pressure of 220 pounds per square inch at the pistons. Stop nuts are provided in the main distributing valve in the governor that can be adjusted to limit the rate of movement of the turbine gates for a full gate closing or opening stroke in from 5 to 15 seconds.

Invitation No. DS-5538 describes the controls, indicators, airbrake valve, shutdown mechanism, automatic turbine gate lock, and all special devices furnished with the governor.

(b) Remote Governor Control and Indicators. --In addition to the controls and indicators located on the governors, the following devices for remote control and indication of the governor of each unit are mounted on the switchboard in the Spring Creek Powerplant control room:

(1) Gate-limit control. --Control for motor operating the gate limit. (Also at Keswick Powerplant.) (2) Gate-position and gate-limit indicator. --Electrically operated dual indication of gate position and gate limit.

(3) Speed-changer control. --Control for motor operating the speed adjustment. (Also at Keswick Powerplant.)

(4) Speed-changer-adjustment indicator. --Speed-changer control functions as indicated to show speed adjustment setting.

(5) Speed-droop-adjustment mechanism. --Control for motor operating the speed-droop adjustment. (Also at Keswick Powerplant.)

(6) Speed-droop-adjustment indicator. --Speed-droop-adjustment mechanism functions as indicator. (7) Draft tube water-level depressor control.

(8) Electrically operated tachometer, to indicate the speed of the turbine. (This indicator was furnished under separate contract from the tachometer on the actuator but is connected to the same rectifier-resistor pack furnished by Woodward Governor Co.)

(9) Complete shut down mechanism. --Electrical control to stop a unit manually or automatically when necessary.

3. Turbine and Governor Unit Auxiliaries

277. Generator and Turbine Bearing Lubrication. (a) Generator Bearings. --The generator thrust and upper guide bearings have the same oil reservoir and are entirely independent of the lubrication system of the lower guide bearing. All bearings are self-lubricating. In addition to the normal lubricating system, a high-pressure lubricating system is furnished to establish an oil film between the thrust bearing surfaces prior to starting, and to maintain the oil film during shutdown. The high-pressure system is self-contained, including a motor-driven high-pressure oil pump, a piping system to introduce the oil between the bearing surfaces, pressure gages, and a pressure relay.

(b) Turbine Guide Bearing. --The babbitt-lined turbine guide bearing is lubricated by an oil-circulated pressure system with two motor-driven oil pumps. One is an alternating-current unit for maintaining normal pressure; the other, a direct-current unit which operates automatically if the oil pressure supply from the alternating-current primary unit drops to a predetermined low. The oil leaving the bearing drains back into an oil reservoir located in the turbine head cover. The reservoir has a capacity of 70 gallons, and each rotary-type oil pump has a capacity of 6 gallons per minute. Provision is made for the future' installation of a heater in the oil reservoir if operating experience indicates it is needed.

(c) Other Turbine Bearings. --A centralized lubricating system is provided for lubricating the gate stem bearings, gate-operating ring, servomotor connections, and gate linkages.

278. Unit Cooling System. (a) Generator Air Cooling Water. --An automatically controlled cooling water system is provided for cooling the air in the generator housing. The system consists of a pumping unit, a diaphragm-operated, three-way diverting valve along with an indicating pneumatic control thermometer and a pneumatic valve positioner.

A centrifugal pump in the unwatering gallery, with a capacity of 1, 800 gallons per minute under a 135-foot head, takes water from the tailrace through a 10-inch valve and twin strainer and pumps it through an 8-inch header to the generator air coolers. An 8-inch, three-way diverting valve in the return line from the coolers proportions the quantity of water to be recirculated and the quantity to be discharged to tailwater.

One emergency cooling water supply pumping unit is provided for the two generating units. Valves are provided for manual control of this source of supply.

A 1/2-inch header, with automatic air-vacuum valves in branch lines from the top of each air cooler, is provided to prevent the accumulation of air in the generator air cooling water system.

(b) Unit Bearing Cooling Water. --The normal unit bearing cooling water is supplied from the turbine spiral casing through a 4-inch plug valve, twin strainer, and a 2-1/2-inch motor-operated valve. A pilotoperated, pressure regulating valve reduces spiral case water pressure to a safe value. A pressure relief valve set to discharge at pressure of 60 pounds per square inch is provided for additional protection. Cooling water from this source is supplied to the generator thrust and upper guide bearing, the generator lower guide bearing, the turbine guide bearing, and the turbine packing box. The approximate flows for each unit are 130 gallons per minute to the generator thrust and upper guide bearing, 10 gallons per minute to the generator lower guide bearing, 45 gallons per minute to the turbine guide bearing heat exchanger, and 20 gallons per minute to the turbine packing box. An emergency cooling water supply for the unit bearings is obtained from the station fire-protection system.

279. Generator Airbrakes and Jacks. Each generator is equipped with air-operated brakes of sufficient capacity to bring the generator and turbine to a stop from one-half normal operating speed within 5 minutes after the brakes are applied.

The brakes are also designed to serve as hydraulic jacks to lift the generator rotor a sufficient distance to provide for removal or adjustment of the thrust bearings. A hand-operated double-plunger pump supplies the oil pressure for jacking.

280. Auxiliary and Service Facilities. (a) Description of Drainage System. --The unwatering system in the powerplant consists of the pumps, piping, and valves necessary to completely unwater each penstock, turbine casing, and draft tube for inspection or repairs. The combined drainage and unwatering sump has an area of approximately 247 square feet. Two sump pumps, each having a capacity of 3, 500 gallons per minute at a total head of 37 feet, are provided to remove the incoming water. Float controls are set to give each pump an operating range of 5 feet variation of water level in the sump. The settings for the float controls are stepped to give a total operating range of 9.5 feet in water level in the sump, with provisions for manually alternating the sequence of the two pumps. A manually operated 1-1/2- by 2-inch scavenging eductor is provided for complete unwatering of the sump.

Special chilling drains from the oil storage and purifier rooms are provided.

(b) Governor and Lubricating Oil Service System. --Separate oil storage and oil transfer facilities are provided for handling the total amount of governor and lubricating oil contained in the governor system and bearing oil reservoirs of one complete generating unit. The same purifier used for purifying the transformer oil is used for the governor and lubricating oil system, and when used on this system, the rate of purifying should be reduced to approximately 300 gallons per hour. One purifier unit is provided for use at Trinity, Clear Creek, and Spring Creek Powerplants. In establishing the size of pipes in the system, the minimum temperature of the oil to be handled was considered to be 50° F. and its viscosity at that temperature 2,000 seconds Saybolt universal.

(c) Transformer Oil System. --Oil storage facilities are provided for handling the amount of transformer oil in the largest transformer installed at the powerplant. The transformers may be brought into the powerhouse for servicing or may be serviced in place. Oil filling and drain connections are provided on the transformer deck only. The system is designed so that unfiltered oil cannot enter the filtered lines. Separate supply and return headers and separate filtered and unfiltered oil storage tanks of identical capacity are provided outside of the powerplant. The transfer pump handles filtered oil only, and the return flow from equipment to unfiltered storage must be pumped. The transfer pump, for transformer oil, has a capacity of 55 gallons per minute to permit filling the largest transformer in approximately 3 hours; and a discharge pressure of 100 pounds per square inch so that standard weight pipe, 150-pound fittings, and 125-pound valves can be used in the piping system. A portable oil purifier with a capacity of 600 gallons per hour is provided for use of Trinity, Clear Creek, and Spring Creek Powerplants. This purifier will dehydrate the transformer oil required for one transformer in approximately 19 hours. In establishing the size of pipes in the system, and also the oil purifier capacity, the minimum temperature of the oil to be handled was considered to be 40° F. and its viscosity at that temperature was 200 seconds Saybolt universal.

(d) Compressed Air System. --Compressed air is provided for the operation of the generator airbrakes, air tools, grease pump, sewage ejector, draft tube water-level depressor system, governor pressure tanks, and for miscellaneous air service requirements.

Two stationary 100-p. s. i. air compressors are provided: one 65-c. f. m. single-stage horizontal compressor with a 48-inch-diameter by 12-foot receiver; and one 375-c. f. m. two-stage horizontal watercooled compressor, with one 48-inch-diameter by 12-foot receiver in the compressor room and one 48-inchdiameter by 12-foot air receiver in unit 1 bay. Aftercoolers and moisture separators are also furnished with these compressors. The air inlet to each compressor, located in a plenum chamber, is provided with an air filter and silencer. A separate header is used for the supply of compressed air to the generator airbrake control valves located on the governors. The plant compressed air piping is arranged so that the large compressor can serve as a standby supply to the generator airbrake system.

The recommended operating pressure range for the small compressor is 85 to 105 pounds per square inch and for the large compressor 80 to 100 pounds per square inch.

One stationary, two-stage, water-cooled, 20-c. f. m., 375-p. s. i. air compressor with aftercooler, moisture separator and 18-inch-diameter by 6-foot air receiver is provided for the air supply to the governor pressure tanks. The compressed air system is connected to the governor tanks with a permanently installed piping system. This high-pressure system also serves as a standby air supply for operation of the circuit breakers.

(e) Service Water System. --Water for general use, air compressor cooling, and domestic service is taken from the turbine penstocks. The 8-inch shutoff valve provided at each penstock and the 10-inch twin strainer are common to the service and fire-protection water systems. Service and domestic waterlines branch off from the common line after the twin strainer. The pressure in the service and domestic water system is regulated by means of pilot-operated pressure-reducing valves. The service and domestic water is not treated and therefore is not used as a source of drinking water. Space is provided for the future installation of a chlorinator and filters if needed.

The service water system also provides water to operate the sump eductor which is used to completely empty the drainage and unwatering sump.

(f) Fire-Protection Water System. --The normal water supply for this system is from the turbine penstocks as described in the preceding subsection. A pilot-operated pressure-reducing valve is provided to reduce the pressure to about 80 pounds per square inch. A pressure relief valve, which should be set to relieve at a pressure of 90 pounds per square inch, is provided to protect the system.

Two 250-g. p. m. pumps are provided for standby water supply to the fire-protection system. These pumps take water from the tailrace and are intended to supply water for the firehoses only. One pump is for normal standby use and the other is for emergency use. Pushbuttons are provided at each hose station so that a pumping unit can be started if the normal supply is shut off.

The water supply to the transformer fire-protection sprays is supplied from the penstocks and is controlled by a motor-operated valve located in the upstream gallery on the turbine floor. The valve is automatically opened by thermostatic controls in the transformers or it can be operated manually. A 2-inch fire-protection water connection is provided adjacent to the 1-line wall and b-line wall at elevation 614.75 for future connection to the spare transformer.

The fire-protection system was designed for the following minimum flows and discharge pressures at the nozzles:

The automatic sprinklers in the oil storage and oil purifier rooms are fusible-link type to release at a room temperature of 165° F. The nozzles on the 1-1/2-inch first-aid hose are nonadjustable, spray or fog type, suitable for class A, B, or C fires. In addition, solid-stream-type nozzles suitable for class A fires are provided. Only nonadjustable fog-type nozzles are provided for the 2-1/2-inch firehoses. The 2-1/2-inch firehoses should be used only by trained personnel.

(g) Stationary Carbon Dioxide Fire-Protection System. --The main generators are protected by a carbon dioxide system which releases its initial discharge of gas upon operation of fusible-link switches located within the generator housings, operation of the generator differential relays, generator ground relay, remote control electric pushbutton stations, or manually at the carbon dioxide cylinders. Electrical and manual release is provided for the subsequent discharges of delayed gas, timed to maintain 25 percent concentration of the gas within the housing for a period of 45 minutes or until the unit stops, whichever is the longer. One bank of 15 initial discharge and 4 delayed discharge 75-pound cylinders protects both generators, the discharge being automatically directed to the proper unit by routing valves in each carbon dioxide manifold.

The oil purifier room is also protected by a stationary carbon dioxide system designed for automatic release 5 minutes after the sprinkler system starts, or for manual release. Release of the carbon dioxide gas to the oil purifier room automatically turns off the sprinkler system by means of a pneumatic trip operated by the gas pressure actuating a weight-operated shutoff valve. One bank of three 75-pound cylinders (initial only) protects the room. Provision is made to close all ventilation openings and fire door by carbon dioxide gas-operated trips in addition to automatic closure by fusible links.

(h) Portable Fire-Protection Equipment.--In addition to the fire-protection water and carbon dioxide stationary systems described above in the previous two subsections, the following portable carbon dioxide fireprotection equipment is provided for first-aid use in fighting fires in the powerhouse:

Note: The portable carbon dioxide extinguishers are for use on class B and C

fires.

(1) Water-Level Gages and Turbine Flowmeters.

(1) Tailwater level.--An indicating-recording water-level system is provided in the powerhouse for tailwater levels. The system consists of a stilling well, a water-level indicator and transmitter, and an indicating-recording receiver. The stilling well is located in unit 1 bay near the downstream wall. It is lined with an 18-inch-outside-diameter steel pipe connected to the tailwater by a 4-inch pipe which extends approximately 50 feet downstream from the centerline of the units. The inlet to the 4-inch pipe has an orifice plate with three 1/2-inch holes to suppress tailwater surges at the float. A connection is provided at the bottom for installing a manometer during tests or for blowing out the connecting line with compressed air if needed.

A float-operated water-level indicator-transmitter is located on top of the stilling well at elevation 604.00, which operates over a range of tailwater levels from elevation 572. 0 to elevation 590.0.

The indicating-recording receiver is located in the control room. This device records the tailwater level on a 10-inch strip chart which travels at the rate of 14. 4 inches per day.

The tailwater level indicating-transmitter and recording equipment was furnished by Leupold and Stevens Instruments, Inc., under invitation No. (D) H-33, 455-A.

(2) Turbine flowmeters. --Flowmeters are provided to measure, indicate, totalize, and record the flow through the individual turbines, summate the flow through the two units, and transmit the summated data to Keswick Powerplant where the data are indicated, totalized, and recorded.

The flowmeters operate by means of the differential pressures obtained from Winter-Kennedy piezometer taps installed in the turbine casings. The flowmeter transmits the instantaneous flow data through the turbine to a receiver-indicator-recorder-transmitter unit. The summator receives the data from the individual units, adds the data, and transmits the total through the plant to Keswick Powerplant. The receiving unit at Keswick Powerplant indicates the instantaneous flow through the plant, totalizes the flow, and makes a continuous record of the flow.

The flowmeters, summator, and receivers were provided originally with dummy flow scales, dials, and charts graduated in convenient units. Data obtained during the turbine acceptance test were used to make flow scales, dials, and charts graduated in correct units.

The turbine flowmeters were furnished by Permutit Co., Division of Simplex Control Systems, under invitation No. (D) J-33, 062-A.

(3) Forebay. --The water-level gage for Whiskeytown Reservoir is located in the emergency gate structure of Spring Creek Power Conduit, and is described in section 245.

281. Turbine Draft Tubes. The draft tubes are of the elbow type, with one intermediate pier in the horizontal portion below the elbow. A welded plate steel draft tube liner extends to the beginning of the pier nose. Mandoors, 24 by 30 inches, are provided in the upstream and downstream draft tube access passages to allow entrance to the underside of the turbine runner for inspection and repairs.

282.

Turbine Draft Tube Bulkhead Gates and Hoists. See sections 123 and 137 for a discussion of the design of the draft tube bulkhead gates and hoists for Trinity Powerplant, which are similar in design and operation to those at Spring Creek Powerplant but differ in size.

5. Major Electrical Equipment

283. Generators. The two generators in this plant are each rated 83,333 kilovolt-amperes, 90 percent power factor, 225 revolutions per minute, 13,800 volts, 3-phase, and 60 cycles. Figures 229 and 230 show the electrical main single-line diagram and switching diagram, respectively. Each generator is a verticalshaft synchronous machine designed for clockwise rotation when looking down on the unit. Each machine is furnished with a thrust and guide bearing located above the rotor, and a guide bearing below the rotor. A common oil reservoir is provided for the thrust and upper guide bearings, and a separate oil reservoir is provided for the lower guide bearing. The thrust bearing is a Kingsbury adjustable-shoe type and is constructed to permit adjustment, dismantling, and assembly of the runner and shoes without disturbing or removing the rotor, stator, upper guide bearing, or upper bearing bracket other than jacking the load from the bearing, and without dismantling the exciter.

The generator manufacturer has embedded thermocouples in the babbitt faces of two shoes of one thrust bearing. The purpose of the thermocouples is an experiment to evaluate bearing performance as indicated by variation in oil film temperature across the faces of the shoes, and by temperature gradients through the shoes. The manufacturer proposes to perform tests utilizing these thermocouples during the normal preliminary operating period. The thrust bearing is supported by the upper bearing bracket. The main exciter and permanent magnet generator, which are directly coupled to the generator shaft, are also supported by the upper bearing bracket. The total load of the upper bearing bracket is transmitted through the stator frame to the soleplates and to the concrete foundation. The generator has eight soleplates, each supporting a vertical load of 219,000 pounds. Each soleplate will support a tangential load of 133,000 pounds, which may occur during a single-phase short circuit.

The lower guide bearing is supported by the lower bracket which also supports the combination airbrakes and hydraulic jacks.

The lower bracket is comprised of eight arms which transmit the load to the soleplates, each of which will support a vertical load of 95,000 pounds when the jacks are used to lift the rotating parts.

Each generator is equipped with a self-contained lubrication system which includes a high-pressure oil system to establish an oil film prior to starting a generator and to maintain the oil film during stopping. Each generator is provided with an enclosed cooling system complete with air ducts, six surface coolers, and a metal housing. The housing is practically airtight to insure effective operation of the automatic carbon dioxide fire-extinguishing system.

Each generator is provided with equipment to automatically control the temperature of air in the air housing by regulation of the cooling water entering the surface coolers. The cooling water control is designed to reduce the magnitude of the variations in machine temperatures which accompany changes in loading.

The main and neutral leads are arranged so that they can be readily interchanged by changing connections to the circuit rings.

Both the armature and field windings are provided with ASA class B insulation. The rotor is equipped with an amortisseur winding, designed to improve stability under fault conditions and to reduce voltage distortion under conditions of a single-phase fault.

The generators were manufactured by the Allis-Chalmers Manufacturing Co. under invitation No. DS-5447 (a) Characteristics. --A tabulation of the generator characteristics is presented in the "Designers' Operating Criteria. "2/

284. Main Exciters. (a) General Description. --Each main exciter is a direct-connected, vertical-shaft, shunt-wound, self-excited, direct-current generator mounted on top of the main generator. The capacity of each main exciter is designed to be at least 10 percent in excess of the actual capacity (in amperes) required to supply the field excitation current of the generator, when the latter is operated at 115 percent rated kilovolt-ampere output, 90 percent power factor and 105 percent rated voltage.

27"Designers' Operating Criteria--Trinity River Division Power System, Central Valley Project, California--Part 5, Spring Creek Powerplant and Power Conduit," Bureau of Reclamation, August 1963 (unpublished).