The maximum temperature rise of the armature windings should not exceed 50° C., and field windings should not exceed 60° C. when delivering rated output continuously at rated voltage, power factor, and frequency, and with cooling air entering the generator at not more than 40° C. The effective life of the winding insulation may be shortened under higher operating temperatures. The contractor warrants that the synchronous condenser capacity of the generator when operating at rated voltage and frequency without exceeding the temperature rise specified above is as follows:

Zero power factor leading (overexcited), 241 kilovolt-amperes

Zero power factor lagging (underexcited), 328 kilovolt-amperes

During continuous operation under a rated load, the temperature in the generator windings, indicated by the resistance temperature detector, should not exceed 90° C. This is based on the generator rating of 50° C. rise above a 40° C. ambient air temperature.

155. Generator and Station-Service Control Equipment. (a) General. --The generator and stationservice control equipment is a completely metal-enclosed, modified industrial-control-type enclosure. It serves the function of housing all generator control devices including voltage regulator, exciter field rheostat, and generator field discharge resistor; generator switchgear; station-service power supply and switchgear; station-service distribution panel; and feeder supply breakers to the Lewiston Dam spillway gate structure and fish hatchery outlet structure. A wiring diagram for the generator and station-service control equipment is shown on figure 124.

The equipment is located on the generator floor immediately adjacent to the generator. All circuits enter or leave the enclosure by means of 600-volt-insulated cables.

(b) Generator Control. --The generator control board portion of the equipment is comprised of the generator air circuit breaker and generator control and protective devices. The generator air circuit breaker is a drawout, electrically operated device, complete with shunt trip, undervoltage trip, and closing motor.

(c) Station Service. --The station-service portion of the equipment is comprised of a manually operated, molded-case, feeder supply circuit breaker; a 480-208/120-volt, a 45-kv. -a. transformer, and a distribution breaker panel. No protective relaying, except for the thermal overload and short-circuit protection associated with the circuit breakers, has been furnished for the station-service system. Individual loads are complete with their own protective systems.

(d) Powerplant Lighting.--The alternating-current lighting distribution installation is supplied directly from the 120/208-volt, station-service distribution panel of the generator and station-service control equipment.

This panel provides branch circuits for energizing all alternating-current lighting fixtures, 115-volt convenience outlets, heating and ventilating units, and other 120-volt devices. All circuits originating in the panel are protected from overload and/or short circuits by circuit breakers of suitable current rating. 156. Service Structure. Because of the few items of electrical equipment required and their relatively small size, there is no switchyard at Lewiston Powerplant. The equipment is mounted on a service structure which is located approximately 30 feet southeast of the powerplant (fig. 119).

The service structure consists of a two-pole structure for terminating the incoming 12-kilovolt line; crossarms for mounting 15-kilovolt fuse-disconnecting switches and lightning arresters; a platform for mounting a 500-kv. -a., 12, 470-480-volt, distribution transformer and 7,200-120-volt neutral grounding potential transformer; and rigid steel conduits for transmission of low voltage to and from the powerplant.

157. Auxiliary and Service Facilities. (a) General.--The station-service facilities consist of the plant drainage system, the service water system, and the compressed air system. These facilities have been kept to a minimum, consistent with the size of the plant and in the interest of economy.

(b) Drainage System.--The plant drainage system consists of a drainage sump with an electric-motordriven, float-controlled, wet-pit-type pump; two floor drains; a turbine pit drain; and embedded drainage and pump discharge piping. The pump discharges to tail race, and a check valve and shutoff valve are provided in the discharge line within the sump. The pump has a capacity of 100 gallons per minute at a head of 20 feet, and was furnished complete with motor starter, float control, and sump cover plate.

An 18-inch emergency drain, consisting of a floor-stand-operated butterfly valve and a flap gate, connected with a cast-iron wall pipe, is provided in the downstream wall for draining out water above elevation 1842.00, in the event that the plant is flooded.

(c) Compressed Air System. --A vertical tank-mounted, single-stage air compressor with a capacity of 5.4 cubic feet per minute at a discharge pressure of 150 pounds per square inch, is provided in the plant to supply a small amount of service air.

(d) Service Water System. --Three 3/4-inch service water connections have been provided in the plant, one at each floor level. Water is supplied direct from the penstock by means of a 1-1/2-inch pipe. A shutoff valve and strainer are provided in the supply line near the penstock takeoff. The water is not potable.

158. Power Supply to Appurtenant Facilities. (a) General. --Lewiston Dam and related facilities, including the spillway, river outlet works, and hatchery outlet works, are discussed in sections 145 through 148. The electrical service provided for these facilities is described below.

(b) River Outlet Works Conduit Lighting. --The circuit serving the river outlet works conduit lighting system originates in the station-service distribution panel of Lewiston Powerplant. Bare lamp outlets are provided in the access passage to the conduit, in the conduit proper, and in the gate chamber. Convenience outlets are provided in the gate chamber and near the entrance door of the access passage. Lights and outlets are controlled by a double-pole switch located near the entrance door at the top of the access passage ladder shaft.

(c) Spillway Electrical System. --Electrical service for the spillway gate structure is extended from Lewiston Powerplant to the structure by buried cable. The service is nominally 480 volts, 3 phase, 60 cycles, and the service circuit originates at a circuit breaker in the powerplant station-service control equipment cubicle and terminates at a motor-starting and control equipment cabinet located at the left abutment of the spillway gate structure. The cabinet is an outdoor weather-resistant type and contains circuit breaker and motor-starting equipment, telemetering equipment, and a lighting transformer. The motorstarting equipment controls operation of the spillway radial gate hoist motors. Operation of motor-starting equipment is generally by remote supervisory control from Keswick Powerplant. The lighting transformer in the cabinet serves lighting circuits extending to pole-mounted lighting fixtures on the gate hoist deck. Spillway gate hoists are provided with limit switches which are connected in the motor-starter control circuits. The switches function to stop gate hoist motors when the gates attain fully open or fully closed positions. Gate position indications and reservoir water-level indication are provided and function in conjunction and association with telemetering system equipment. Telemetering of the two spillway radial gate positions and of Lewiston Reservoir water-level indication to Keswick Powerplant has been provided. Telemetering circuits are extended from the spillway cabinet to Lewiston Powerplant by means of a buried control cable which is generally routed along the buried power service cable which serves the spillway structure.

The motor, control, and lighting circuits emanating from the spillway electrical cabinet are afforded overcurrent protection by circuit breakers in the cabinet. Motors are also afforded overload protection by thermal overload devices associated with the motor starters. Operation of gates is to be normally controlled by the telemetering system.

The spillway structure is provided with a grounding system to which electrical equipment enclosures, electrical conduits, machinery bases, and other metalwork items are connected.

(d) Hatchery Outlet Works Electrical System. --Electrical service for the outlet works structure is extended from Lewiston Powerplant to the structure by buried cable. The service is nominally 480 volts, 3 phase, 60 cycles, and the service circuit originates at a circuit breaker in the powerplant station-service control equipment cubicle and terminates at an electrical control board located on the upstream wall of the outlet works regulating structure. The control board enclosure is an outdoor weather-resistant type. Control board equipment includes power and lighting circuit breakers, and motor-starting and control equipment for the slide gate lifts located on the regulating structure.

(1) Intake structure power system. --Power service to the intake structure is nominally 480 volts, 3 phase, 60 cycles. The service is supplied to the intake structure by a circuit originating at the regulating structure control board, extending through the horseshoe outlet conduit, and rising to the hoist deck of the intake structure. The circuit serves two circuit breakers and a combination motor starter located or a metal plate attached to the hoist deck handrailing. The two circuit breakers serve circuits extending to screen hoist motor control equipment installed on the structure.

(2) Outlet works lighting. --Single-phase lighting service at 120/240 volts, 60 cycles, is obtained from a single-phase, 480- to 120/240-volt transformer located adjacent to the control board at the regulating structure.

The transformer is served from a two-pole power breaker in the control board, and this transformer in turn serves a group of single-pole branch lighting circuit breakers in the control board with the indicated 120/240-volt service. The branch lighting circuit breakers serve lighting circuits extending to the intake structure, the horseshoe outlet conduit, and the hoist or lift deck of the regulating structure. A circuit from a lighting breaker also serves the ventilating fan located in the horseshoe outlet conduit.

(3) Regulating gate control system. --The regulating gate lift motors are connected to and operate through magnetic reversing starters contained in the control board. The starters afford associated lift motors overload protection by means of manual-reset-type thermal overload devices provided with the starter equipment and are also contained in the control board. Auxiliary control components are provided to function with motor starters in such a manner that lifts can be operated manually by pushbuttons or automatically through probe or electrode relay devices actuated by rise and fall of water surface in the downstream chamber of the regulating structure. Selector switches are provided in the control board to permit an operator to select either manual or automatic operation for each gate lift as desired.

The structure is provided with a grounding system, to which electrical equipment enclosures, electrical conduits, machinery bases, and other metalwork items are connected.

159. Spillway Gate Control and Telemetering System. A remote supervisory control and selective telemetering system has been provided between Keswick Powerplant, the controlling station, and Lewiston Dam, the controlled station. The supervisory control consists, principally, of position control of two spillway radial gates at Lewiston Dam. The telemetering equipment is used to transmit the position of the two spillway gates, the flow through the Lewiston Dam outlet works, the water level in the Lewiston Reservoir, abnormal flow alarm, Lewiston Powerplant general alarm, and high reservoir water-level alarm, to Keswick Powerplant. The supervisory control and telemetering channel uses audiotones superimposed on telephone circuits leased from the Pacific Telephone and Telegraph Co.

CHAPTER V. Design--CLEAR CREEK FEATURES

A. Clear Creek Power Conduit, Appurtenant Features, and Penstocks

1. General

160. Description. Clear Creek Tunnel is a portion of the power conduit used to carry water from Lewiston Reservoir on the Trinity River to Clear Creek Powerplant, which is located near the upper end of Whiskeytown Reservoir. The tunnel is about 10.8 miles in length and is lined throughout with concrete to a finished circular diameter of 17 feet 6 inches, except for a length of 385 feet at the outlet end which is lined with steelplate to a diameter of 15 feet 8 inches. At its outlet end the conduit divides into two 10-foot 6-inch diameter steel penstocks. The alinement and profile for the pressure tunnel are shown on figure 125. Sections and details of the pressure tunnel are shown on figure 126.

161. Scope. In general, this chapter is confined to the design of the features constructed under specifications No. DC-4803. These are Clear Creek Tunnel including the tunnel intake, the surge tank, and the tunnel outlet; instrumentation installations; and the steel penstock, 158-inch butterfly valves, and miscellaneous mechanical and electrical features pertinent to the tunnel system.

2. Preliminary Considerations

162. General. The power features of the Trinity River diversion plan are interrelated, so it was necessary to consider the total energy produced from all of the powerplants when studying any one feature. Since the capacities and sizes of the two conduit systems, namely Clear Creek and the later discussed Spring Creek, were not established, it was necessary to make numerous preliminary designs and estimates.

163. Alternative Routes. Following preliminary studies which indicated generally the terminal points for the diversion from the Trinity River, two routes were considered for the Clear Creek Power Conduit. These routes are referred to as lines A and B.

Line A was the most direct route from the intake site on the Trinity River (Lewiston Reservoir) to the powerplant site on Clear Creek. The length of this route was approximately 10.2 miles. The conduit would have consisted of four tunnels and three inverted siphons. The upstream two-thirds of the conduit would have traversed the Bradgon formation, which consists of black shales, gray siltstone, and sandstones metamorphosed to slates, argillites, and quartzites, and the remainder would have been in the metavolcanics.

The B line, approximately 10.8 miles in length, was laid out to take advantage of the better tunneling conditions expected in the granodioritic rock mass which lies to the southwest of the A line. The contact zone between the Bradgon and Granodiorite formations is characterized by the Hoadley fault zone, a 50- to 300-foot-wide belt of intensely sheared and crushed rock. The B line was located in the granodiorite to the south of and parallel to the fault zone. A total of four bends was required in the tunnel alinement in order to maintain a satisfactory location with respect to the fault. The line B route was selected in the final analysis.

164. Selection of Route. Field inspections of the alternative tunnel alinements were made from May 21 to 25, 1956. As a result of these inspections, the location of the B line was revised slightly to provide for more overburden cover in some reaches, and to gain what was considered to be better tunneling conditions and a better location for the penstocks at the tunnel outlet. The revised B line location is essentially the final alinement as shown on figures 125 and 127.

Using the revised alinement and revised geologic information for the B line as a basis, comparative cost estimates were prepared for both A and B lines. The difference in estimated cost between the two conduit locations, including allowances for the difference in head which would be developed under each plan, was insignificant.

As geologic conditions along the B line were considered to be more favorable, it was decided that construction should be undertaken on the latest general alinement of this line.

165. Selection of Capacity and Size. The selection of capacity and size for the Clear Creek Power Conduit required coordination with studies of size and capacity for the Spring Creek Power Conduit.

Numerous estimates were prepared so that the capacity of the installations for the Trinity project could be studied. Five estimates each were prepared on the Clear Creek Power Conduit and on the Spring Creek Power Conduit.

The estimates were prepared on the basis of the following capacities:

Feature

Design capacities, second-feet

Clear Creek Power Conduit
Spring Creek Power Conduit

1,700 2,500 3, 130 3, 400 4,000
1,700 2,500 3, 130 3, 600 4, 200