controller turret from the Montrose Power Operations Center has not been provided. The unit controller turret has the following control and indication features:

(1) Lighted pushbuttons for "On-Off" control of each unit. The "On" pushbutton lights red when the unit is on load and frequency control and the "Off" pushbutton lights green when the unit is off load and frequency control. "On-Off" control indication for each unit has been provided at the Montrose Power Operations Center.

(2) Microwave signal failure white lamp indication for each unit.

(3) A short-time duration audible alarm.

Unit load and frequency control for the individual units will be automatically tripped off and an audible alarm will be sounded for the following:

(1) A long-time pulse duration for raise or lower impulses to prevent misoperation of the generator due to faulty equipment or during extended periods of high noise level on the microwave channel.

(2) Microwave channel signal failure.

(3) Loss of direct-current control power.
(4) Abnormally high plant total frequency.
(5) Unit shutdown to speed-no-load.

(6) Emergency and normal unit shutdown.

Whenever any unit is taken off load and frequency control, the unit must be manually returned to load and frequency control at the powerplant.

114. Protective Relaying. (a) General.--The protective relays for each line, transformer, and generator are semiflush mounted on the rear panels of the main control board. The relaying scheme is shown on the single-line diagram, figure 142.

(b) 230-Kilovolt PP and L Line, 138-Kilovolt Lines, and Transfer Breaker. --The following line relays have been provided:

Device 121. --Zone-packaged, directional distance relays for phase protection.
Device 167G. --Directionally polarized overcurrent ground relays.

Spare 121 and 167G relays have been provided on the control board for two future 138-kilovolt lines. Also, space has been provided on the control board for future carrier relaying for the 138-kilovolt lines.

The 121 and 167G relays for the bus-tie breaker will protect for 138-kilovolt line phase and ground faults whenever the bus-tie breaker is substituted for a line breaker. These bus-tie relays will also offer protection for faults on the 138-kilovolt transfer bus and backup protection for many faults associated with transformer KY1A, 69-kilovolt buses, and 69-kilovolt Bridger Valley line. Single-shot reclosing is provided for each 138-kilovolt line breaker and for the 230-kilovolt transformer breaker. The reclosing for the 138-kilovolt lines, however, is interlocked with three-option checking: dead line, live bus; dead bus, live line; and synchronism checking.

The 230-kilovolt PP and L line is provided with carrier relaying transfer trip; therefore, three-option checking is not required for reclosing.

(c) 69-Kilovolt Line. --The following standard line overcurrent relaying has been provided:

Device 151. --Overcurrent relay for phase protection.
Device 151G. --Overcurrent relay for line ground protection.

Three-shot reclosing is provided and is interlocked with a dead line checking relay to permit reclosing only on a dead line.

Device 1591. --Instantaneous overvoltage relay.
Device 159T. --Time delay overvoltage relay.
Device 181. --Overfrequency relay.

These devices are provided to protect loads on the 69-kilovolt line from damage due to overvoltage or overfrequency resulting from load rejection on the 138- and

230-kilovolt lines. These relays are energized from the 69-kilovolt bus potential transformers. They are used to trip the 69-kilovolt breaker, the 24.9-kilovolt reclosers, and the 12.5-kilovolt station-service breaker. They also block reclosing of the 69-kilovolt breaker. The 24.9-kilovolt reclosers will not reclose when tripped by these relays, but will reclose on overload trip only.

(d) 69- and 138-Kilovolt Buses. --Induction disk, overcurrent relays with short-time current characteristics are used for differential protection of the 69-kilovolt main bus, the 138-kilovolt transformer bus from the generators, the 138-kilovolt main bus, and the 138-kilovolt bus to the 230-kilovolt transformer KY2A. Each bus differential circuit extends to the bushings of the transformers except the 69-kilovolt bus differential relay circuit which includes the 69-kilovolt transformer KX2A. All current transformers in these circuits are differentially connected. The 138-kilovolt bus differential relaying is to be taken out of operation (by turning the transfer trip switches) when the tie breaker is out of service or is used to replace the generator breaker or to replace a line breaker. Under these conditions 138-kilovolt main bus faults are cleared as follows:

(1) Vernal lines No. 1 and 2 relays cannot detect the fault because of their directional characteristics; therefore, the breakers at the Vernal substation will be tripped by the relays there.

(2) The generator voltage-restrained, overcurrent relays 51V will initiate shutdown and trip the generator breakers.

(3) The Bridger Valley 69-kilovolt line relays cannot detect a 138-kilovolt bus fault; therefore, relays at the customer's end of the line will operate to interrupt fault current contributed from this source.

(4) No fault current is supplied by the 24.9-kilovolt Moon Lake lines.

If the 138-kilovolt bus-tie breaker 2076 (JY9A) is not being used as a transformer KY1A breaker, all of the 138-kilovolt breakers will be tripped for 69-kilovolt bus or 69-kilovolt transformer KX5A faults. The 69-kilovolt main bus differential relaying is to be taken out of operation (by turning the transfer trip switch 169TB2 located on panel 11R) when the breaker is bypassed. Faults on the 69-kilovolt bus and line, or in the 69-kilovolt transformer KX2A will then be cleared as follows:

(1) By customer relaying at the remote end of the 69-kilovolt line.

(2) By protective relays at the 138-kilovolt bus-tie breaker 2076 (JY9A).

(e) Main Switchyard Transformer Banks. --The transformer banks in the switchyard are protected as follows:

(1) The 138/69/12.5-kilovolt transformer KY1A is provided with a set of percentage differential, harmonic-restrained relays 187T. The protected zone extends to the 138- and 69-kilovolt bushings on the transformer and to the load-side bushings of 12.5-kilovolt breaker JV1A. Faults on the low sides of the switchyard stationservice transformer KV1A and the visitors' center transformer KV2Å are limited by the impedances of these transformers so as to not trip the 187T differential relays.

If the 138-kilovolt bus-tie breaker 2076 (JY9A) is not being used as the transformer breaker, then all 138-kilovolt breakers will be tripped for transformer KY1A faults.

(2) The 67/24.9-kilovolt transformer KX2A is included in the 69-kilovolt bus differential relay circuit as stated in paragraph (d) above.

(3) The 230/138/13.2-kilovolt transformer KY2A is provided with a set of percentage differential, harmonic-restrained relays 187T3. When transformer breaker 1872 (JY2A) is replaced by breaker 2076 (JY9A), tripping is transferred to breaker 2076 by turning the transfer trip switch 169TB3 located on panel 12R.

(f) Unit Transformers. -- Each unit transformer is provided with a set of percentagedifferential, harmonic-restrained relays 87T which trip all three unit breakers, the station-service breakers, and the transformer bus breaker 12372 (JY3A). When the transformer bus breaker (JY3A) is replaced by (JY9A), tripping is transferred to 2076 (JY9A) by turning transfer trip switch 169TB1 located on panel 3R.

The protected zone extends from the generator side of the generator breakers to the 138-kilovolt bushings of the unit transformers. For units 1 and 2, the zones also

extend to the load side of the station-service breakers (U1A2 and U2A 2, respectively). Unit 3 does not provide station-service load.

(g) Generators. -- Each generator is provided with the following protective relays:

(1) A set of percentage differential relays.

(2) An instantaneous overvoltage relay.

(3) A time delay overvoltage relay.

(4) A set of voltage-restrained overcurrent relays for backup protection of the generator. The protective zone includes the 138-kilovolt bus.

(5) A ground relay of the overvoltage, induction disk type. This relay is connected to the generator neutral grounding transformer.

(h) Station-Service Transformers. --The station-service transformers are protected as follows:

(1) Transformer KR1B (which is fed from either unit 1 or 2) is protected by a set of overcurrent relays (51T) which trip either breaker U1A2 or U2A2 depending upon which one is being used. Transferring the tripping to the proper breaker is automatically provided by "a" contacts in the breaker; hence, no transfer trip switch is required.

(2) Transformer KR2B (which is fed from the tertiary winding of transformer KY1A in the switchyard) is protected by a set of overcurrent relays (151-2) which trip station-service oil-circuit breaker 5024 (JV1A) in the switchyard. These relays also protect the 12.5-kilovolt overhead line from the switchyard to the powerplant.

115. Metering and Indication. (a) General.--The indicating instruments for the 230-, 138-, and 69-kilovolt lines and for the generators are mounted on their respective front panels of the main control board CCA. The indicating instruments for the 24.9-kilovolt lines and for the station-service system are mounted on the unit graphic and miscellaneous control board CCB. Metering for the 230-, 69-, and 24.9-kilovolt lines is provided on their respective panels of the line graphic board CCC. Metering for the generators and for station service is provided on the unit graphic and miscellaneous control board CCB. A frequency recorder and a voltage recorder for 230-, 138-, and 69-kilovolt buses are also mounted on CCB. Mimic buses for the powerplant, switchyard, and station-service system are painted on the fronts of the main control board CCA and of the unit graphic and miscellaneous control board CCB.

(b) 230-, 138–, 69- and 24.9-Kilovolt Lines. --Each line and the 138-kilovolt bus-tie are provided with instruments to indicate amperes, watts, and vars. The 230- and 69kilovolt lines are each provided with three-element "in" and "out" watt-hour meters and "in" and "out" (watt) digital demand recorders. Each 24.9-kilovolt line is provided with a three-element "out" watt-hour meter with indicating demand and with an "out" (watt) digital demand recorder. Each breaker position (for 138- and 69-kilovolt breakers) is indicated by red and green lamps directly above the breaker control switch. White relay potential indicating lamps are provided for each 138-kilovolt line and are connected to each phase of the 138-kilovolt bus potential transformers.

(c) 230-, 138-, and 69-Kilovolt Buses.-- A frequency recorder, a bus voltage recorder, and a transfer switch are provided so that any one of the three bus voltages and frequencies can be recorded.

(d) 12.5-Kilovolt Station-Service System. --A voltmeter and switch is provided for the 12.5-kilovolt bus. An ammeter and switch and a two-element watt-hour meter with indicating demand are provided for the combined switchyard station-service and visitors' center loads.

(e) Powerplant Station Service.--A voltmeter with switch, two ammeters with switches, a watt-hour meter with indicating demand, and a watt-hour meter potential switch are provided on the unit graphic and miscellaneous control board CCB for the 440-volt powerplant station-service system. Breaker positions of supply (from switchyard or generators), main, and tie breakers are indicated by red and green lamps directly over each breaker control switch.

(f) Generating Units. -- Each generating unit is provided with instruments on the main control board to indicate volts, amperes, watts, vars, regulator current, field amperes,

percent speed, gate position, gate limit, speed setting, and speed droop, and a meter to record operating time. The percent speed, gate position, gate limit, speed setting, and speed droop indicators are also available at the governor actuator but are duplicated on the main control board so that the operator can perform all control functions from the control room.

The following lamp indication has been provided:

(1) Generator "Start-Stop" lamp.

(2) Annunciator group lamp.

(3) Auxiliaries "Running" lamp.

(4) Normal "Shutdown-Reset" lamps.

(5) Brake "On-Auto-Off" lamps.

(6) Breaker position lamps.

(7) Generator symbol.

(8) Exciter field rheostat lamps.

(9) Water depressing lamps.

(10) Turbine emergency shutdown lamps.

(11) Penstock gate emergency shutdown lamps.

(12) Field breaker lamps.

(g) Plant--General. Headwater and tailwater elevation recorders were provided in the southwest corner of the control room.

116. Annunciators. (a) General. -- Five 30-drop annunciators have been provided as follows:

(1) One for each generating unit.

(2) One for the lines and switchyards.

(3) One for the station-service system and the 24.9-kilovolt lines.

The generating unit and the line and switchyard annunciators are located on the main control board CCA; the station-service system and 24.9-kilovolt lines annunciator is located on the unit graphic and miscellaneous control board CCB.

Closing of a trouble contact will light the yellow group lamp, light an annunciator window, sound a common bell in the control room, and sound common alarm horns located in the generator room, in the pipe gallery, and in the switchyard. The bell and horns can be silenced and the group lamp extinguished by pushing the "Horn Reset" pushbutton. Releasing this reset button will not cause the bell and horns to sound nor the group lamp to light; however, the bell and horns will sound and the group lamp will light when another trouble contact closes. The annunciator windows can be reset by pushing the "Lamp Reset" pushbutton; however, if a trouble contact remains closed, the associated annunciator window will remain lighted. Each annunciator group can be tested by pushing the test pushbutton which should light all 30 annunciator windows in the group.

The generating unit annunciator systems are designed so that there will not be annunciation for normal startup nor for normal shutdown.

(b) Sequential Operations Recorder. --A sequential operations recorder (recording annunciator) is provided in a separate cabinet mounted on, and connected to, a console housing in the control room against the 3-line wall behind the operator's desk. The recording cabinet may be relocated near the operator's desk and connected by a cable to the console housing. The recorder makes a printed record on chart paper of the opening and closing of up to 100 contacts. Events are recorded in sequence, and there is included a printed record of time of occurrence within 1 millisecond. The recorder is connected to record the closing and opening of circuit breakers, and also to record the operation of auxiliary relays in the annunciators. The closing of these auxiliary relays is controlled by trouble contacts; and the opening is controlled by operation of the annunciator reset pushbutton.

117. Grounding System. The grounding system consists of a ground mat under the powerhouse foundation and under part of the dam. The grounding system was designed to provide a ground resistance of less than 1 ohm. Field tests after installation indicated a ground resistance of between 0.9 and 1 ohm.

Six 500, 000-circular-mil risers and one No. 4/0 riser extend from the ground mat to the powerhouse. Each 500, 000-circular-mil riser is capable of withstanding 24, 000 amperes short-circuit current for 9 seconds.

G. Auxiliary Electrical Equipment and Installation

118. Alternating-Current Station-Service Supply System. (a) General. --The alternating-current station-service system is supplied from a 1, 500 kv.-a., 480-volt, double-ended unit substation. One end is supplied either from unit 1 through stationservice breaker U1A2 or from unit 2 through station-service breaker U2A2. The other end of the unit substation is supplied from the tertiary of switchyard transformer KY1A through oil-circuit breaker JV 1A. The unit substation has been designed with sufficient capacity so that either end can carry all essential plant loads. The breakers feeding the powerplant and dam main heating loads are provided with shunt trips, so that these loads can be automatically dropped. Station-service voltage at 480 volts was chosen as being the most practical for a plant of this size.

(b) 480-Volt Switchgear. --The 480-volt station-service switchgear consists of a double-bus, double-ended unit substation with two supply breakers and a tie breaker. The self-cooled 750-kv.-a. transformers are located on the transformer deck. Transformer KR1B is rated 12, 000 to 480 volts Y and is fed from either unit 1 or unit 2. Transformer KR2B is rated 13, 200 to 480 volts Y and is fed from the switchyard. A disconnect switch is provided on the high side of transformer KR2B and is key interlocked with the low-side breaker to prevent operation under load. The control circuits of the two supply breakers and of the tie breaker are electrically interlocked so that normally not more than two of these three breakers can be closed at the same time, thereby avoiding the possibility of connecting unsynchronized sources together through the switchgear. Under emergency conditions, it is possible to bypass this interlock and thereby close all three breakers in order to feed power to the switchyard station-service system. This should only be done when the switchyard supply is isolated from the tertiary of transformer KY1A by having switch 1521 (WV1B) in the switchyard open.

Under normal operating conditions, the station-service load is divided and one-half is connected to each of the two transformers. The tie breaker will close automatically if one of the supply breakers is tripped by its control switch or is tripped by its undervoltage relay if the breaker control transfer switch is in the "Auto" position. Closing of the transfer breaker is blocked if one of the supply breakers is tripped by its own overload protective devices.

If the tie breaker closes, the feeder breakers which supply the dam and powerplant heating loads will be tripped automatically and the entire remaining station-service load will be connected to one transformer. If the one transformer is overloaded under these conditions, it should be an operational procedure to manually drop additional load. Each breaker closing circuit is interlocked with a synchronism check relay to check synchronism and to close one breaker just before the other breaker trips.

(c) 460-Volt Distribution System. -- The following alternating-current distribution boards or motor control centers have been provided throughout the plant:

(1) Unit power boards (M1A, M2A, and M3A).

(2) Miscellaneous power boards for general plant loads (MCA, MRA, and MSA). (3) Machine shop miscellaneous power boards MSB.

(4) Starters and control centers for heat pumps (NSA and NSB).

The feeders to the crane and to the dam are supplied directly from the 480-volt unit substation. Figure 148 shows a single-line diagram of the 460-volt distribution system.

119. 125-Volt Direct-Current System. (a) General. --The direct-current power is used for all important powerplant and switchyard control circuits and is distributed from three locations: the direct-current distribution board BCA, breakers located on the rear of main control board CCA, and breakers located on the side sheets in unit graphic and miscellaneous control board CCB. Each control circuit has been provided with an undervoltage relay to provide alarm for loss of control voltage.