Sistema Eléctrico B767-300

B767

ElectricalDONOTUSEFORFLIGHT

IntroductionThe electrical system generates and distributes AC and DC power to other airplane systems, and is comprised of: main AC power, main DC power, and battery/standby power. System operation is automatic. Electrical faults are automatically detected and isolated.A hydraulic driven generator operates automatically as a backup source of power in the event that both main AC buses become inoperative.

AC Electrical SystemThe AC electrical system is the main source for airplane electrical power.

AC Electrical System Power SourcesThe entire airplane AC electrical load can be supplied by any two main airplane AC power sources.The main airplane AC electrical power sources are:

left and right engine integrated drive generators (IDGs) APU generator.

The entire airplane AC electrical load also can be supplied by external power.The power sources operate isolated from one another.

Integrated Drive Generators (IDGs)Each engine has an IDG. Each IDG has automatic control and system protection functions.When an engine starts, with the GEN CONT switch selected ON, the IDG automatically powers the respective main bus. The previous power source is disconnected from that bus.The IDG can be electrically disconnected from the busses by pushing the GEN CONT switch to OFF. The IDG can also be electrically disconnected from its respective bus by selecting external power prior to engine shutdown. (See External Power in this section.) The OFF light in the GEN CONT switch illuminates, and the EICAS Advisory message L or R GEN OFF displays whenever the generator control breaker is open.

Boeing B767 - Systems Summary [Electrical]

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The DRIVE light illuminates and the EICAS Advisory message L or R GEN DRIVE displays when low oil pressure or high oil temperature is detected in an IDG. The IDG drive can be disconnected from the engine by pushing the respective DRIVE DISC switch. The IDG cannot be reconnected by the flight crew.

APU GeneratorThe APU generator is electrically identical to the IDG generators. The APU generator can power either or both main busses, and may be used in flight as a replacement to an IDG source. If no other power source is available when the APU generator becomes available, the APU generator automatically connects to both main AC busses. If the external source is powering both main busses, the external source continues to power both main busses.The APU Generator OFF light illuminates, and the EICAS advisory message APU GEN OFF displays when the APU is operating and the APU generator breaker is open because of a fault or the APU GEN switch is selected OFF. When the APU GENERATOR switch is ON and a fault is detected, the APU generator cannot connect to the busses.

External PowerExternal power can power the left and right main busses. When the power source voltage and frequency are within limits, the external power AVAIL light illuminates.Pushing the EXT PWR switch ON connects external power to both main busses and removes the IDGs and the APU generator from the busses, if they were powering the busses. When external power is connected to a main bus, the EXTERNAL POWER ON light illuminates.

AC Electrical Power DistributionAC power is distributed through the left and right main busses and the ground service bus.

AC Main BussesThe right IDG normally powers the right main bus and the left IDG normally powers the left main bus. The APU normally powers both main busses when they are not powered by any other source. External power may also be connected and will also power both main busses.Bus tie breakers, controlled by BUS TIE switches, isolate or parallel the right and left main busses. When both BUS TIE switches are set to AUTO, the bus tie system operates automatically to maintain power to both main busses.


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The AC bus ISLN light illuminates and the EICAS advisory message L or R BUS ISOLATED displays when the bus tie breaker is open because of a fault or the BUS TIE switch is OFF.The BUS OFF light illuminates and the EICAS caution message L or R AC BUS OFF displays if an AC bus is unpowered.The source order for powering left and right main busses is the:

respective IDG APU generator opposite IDG.

Utility BussesLeft and right utility busses, powered by their respective main AC bus, are controlled by UTILITY BUS switches. Left and right galley busses are powered by their respective utility busses, and have no direct controls or indicators. The utility bus OFF lights illuminate and the EICAS advisory message L or R UTIL BUS OFF displays when a galley and utility bus are unpowered.

Ground Service BusThe ground service bus is normally powered by the right main bus. Alternate sources of power for the ground service bus are:

the APU generator external power.

The ground service bus powers:

Ground Handling BusThe ground handling bus can be powered only on the ground and only from the APU generator or from the external power source. It is provided for loads such as cargo handling and equipment energized only during ground operations.

AutolandDuring autoland, the busses isolate to allow three independent sources to power the three autopilots:

the left main system powers the left autopilot and the captains flight instrument transfer bus

the right main system powers the right autopilot and the first officers flight instrument transfer bus

the battery/standby system powers the center autopilot.

the main battery charger the APU battery charger

miscellaneous cabin and system loads.


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Above 200 feet, loss of a generator results in: both bus tie breakers closing and the operating generator powers both left

and right AC busses the left main system powers the center autopilot NO LAND 3 appears on the Autoland Status Annunciator.

Below 200 feet, loss of a generator results in: both bus tie breakers remaining open the autopilot associated with a failed generator is unpowered the flight instruments remain powered through the flight instrument

transfer busses the autoland continues using the remaining two autopilots.

When the autopilots are disengaged or an autopilot goaround is performed, the electrical system reverts to normal, nonisolated operation.

Flight Instrument Transfer BussesNormally, the captains flight instruments are powered by the left main AC Bus, and the first officers flight instruments are powered by the right main AC Bus. If the respective bus tie breakers are in AUTO, the flight instrument transfer busses transfer to the opposite main AC bus in the event power is lost to a main AC Bus.If power is lost to both main AC busses, the captains flight instruments are powered by the hydraulic driven generator.

AC Transfer BussesLeft and right AC transfer busses power items considered necessary for ETOPS flights, which are not powered by the battery/standby system. Transfer busses are normally powered by their associated main AC busses, but also can be powered by the Hydraulic Driven Generator when both AC busses are unpowered.

Electrical Load SheddingElectrical load shedding occurs automatically to ensure power is available to critical and essential equipment.If the electrical loads exceed the power available, the electrical system automatically sheds AC loads by priority until the loads are within the capacity of the generators. The load shedding is galley power first, then utility busses. Utility busses are followed by individual equipment items powered by the main AC busses. When an additional power source becomes available or the load decreases, the electrical system automatically restores power to the shed systems (in the reverse order).


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Examples of load shedding that may be observed during normal operations include:

an electric hydraulic pump prior to engine start center tank fuel pumps prior to engine start utility busses during engine start.

Examples of load shedding that may be observed during nonnormal operations include:

utility busses after a generator failure center tank fuel pump after an engine failure cabin ceiling lights after an engine failure.

On the ground, advancing the thrust levers into the takeoff range with the engines shut down may cause inadvertent load shedding of the utility busses to occur. Returning the thrust levers to idle, then pushing the UTILITY BUS switches OFF, then ON will reset this inadvertent load shedding.


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AC Electrical System Schematic (Hydraulic Driven Generator)

DC Electrical SystemThe main DC electrical system uses transformerrectifier units (TRUs) to produce DC power. The TRUs are powered by the main AC busses.

DRIVE

SECONDARY OR BACKUP POWER SOURCE

PRIMARY POWER SOURCE

APU GEN

SWITCHCONTROL

CONTROL

LEFTGEN RIGHT

CONTROLGEN

RIGHTMAIN

BUSAC

TIEBUSRIGHTLEFT

TIEBUS

DRIVELEFT

TO STANDBYAC BUS

EXTERNAL

GEN

APU

GROUNDHANDLING BUS SWITCH

POWER

TO

CHARGERSBATTERY

RIGHT UTILITYBUS

F/O FLT INSTRTRANSFER BUS

RIGHT ACTRANSFER BUSTRANSFER BUS

LEFT AC

TRANSFER BUSCAPT FLT INSTR

LEFT UTILITYBUS

GROUNDSERVICE BUS

DRIVEN GENERATORHYDRAULIC

MAINLEFT

BUSAC

DRIVERIGHT

ISLN

AUTO

ISLN

AUTO

OFF

ON

OFF

ON

APU GEN EXT PWR

BUSOFF

ON

AVAIL

BUSOFF

ONOFF

BUS TIE BUS TIE

UTILITY BUS

L R R BUSL BUS

LGENCONT

RGENCONTGEN DRIVE DISC

L R

ONOFF

ONOFFDRIVE


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The TRUs operate isolated from one another. If one TRU fails, the DC bus tie breaker closes to keep both DC busses powered. Both BUS TIE switches must be in AUTO for the DC bus tie breaker to close.There are no flight deck controls for the main DC electrical system.


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DC Electrical System Schematic

DRIVEDRIVE

DCDC

DC BUS

BATTERY BUS

FROM RIGHTAC BUS

FROM LEFTAC BUS

BATTERYMAIN

TIE BREAKERDC BUS

T

RIGHTMAIN

BUS

TO STANDBY

MAINLEFT

BUS

TRU TRU

SECONDARY OR BACKUP POWER SOURCE

PRIMARY POWER SOURCE

ISLN

AUTO

ISLN

AUTO

OFF

ON

OFF

ON

APU GEN EXT PWR

ON

AVAILON

OFF

BUS TIE BUS TIE

UTILITY BUS

L R R BUSL BUS

LGENCONT


L R

ONOFF

ONOFF

BUSOFF

BUSOFF


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Battery/Standby Power SystemThe battery/standby power electrical system can supply DC and AC power to selected flight instruments, communications and navigation systems, and other critical systems, if there are main AC and DC electrical power system failures.The Battery/Standby Power System consists of the following busses:

the hot battery bus the battery bus the standby AC bus the standby DC bus

Hot Battery BusThe hot battery bus provides power to items which must be continuously powered, such as the clocks time reference.Prior to establishing electrical power, the main battery powers the hot battery bus.After establishing electrical power, the main battery charger powers the hot battery bus.

Battery BusPrior to establishing electrical power, when the battery switch is ON, the main battery powers the battery bus.After establishing electrical power, the left DC system powers the battery bus, and the main battery provides a backup source of power.The Battery DISCH light illuminates when the main battery is discharging. If EICAS is powered, the advisory message MAIN BAT DISCH also displays.The battery OFF light illuminates and the EICAS advisory message BATTERY OFF displays if the battery switch is OFF after electrical power is established.

Standby DC BusThe standby DC bus can be powered by several sources. Prior to establishing electrical power, when the battery switch is ON and the standby power selector is in AUTO, the main battery powers the standby DC bus. The Battery DISCH light illuminates when the main battery is discharging. After establishing electrical power, the left DC system powers the standby DC bus and the main battery provides a backup source of power. When the standby power selector is in BAT, the main battery powers the standby DC bus.The standby bus OFF light illuminates and the EICAS advisory message STANDBY BUS OFF displays if the standby DC bus is not powered.


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Standby AC BusThe standby AC bus can be powered by several sources. Prior to establishing electrical power, when the battery switch is ON and the standby power selector is in AUTO, the main battery powers the standby inverter which provides AC power to the standby AC bus. After establishing electrical power, the left AC system powers the standby AC bus and the main battery and standby inverter provide a backup source of power. When the standby power selector is in BAT, the main battery and standby inverter power the standby AC bus.The standby bus OFF light illuminates and the EICAS advisory message STANDBY BUS OFF displays if the standby AC bus is not powered.


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Battery/Standby System Schematic

Hydraulic Driven GeneratorThe hydraulic driven generator (HDG) activates automatically when both the left and right main AC busses are unpowered. The Hydraulic Driven Generator (HDG) is powered by the Center Hydraulic System.

ON

ON

ON

BATOFF

AUTO

STBY POWERBAT

L MAINDC BUS

L MAINAC BUS

DC BUSSTANDBY

AC BUSSTANDBY

BATTERYBUS

FFO

BATTERYMAIN

HOT BATTERYBUS

BATTERYCHARGER

BATOFF

AUTO

STBY POWERBAT

L MAINDC BUS

L MAINAC BUS

DC BUSSTANDBY

AC BUSSTANDBY

BATTERYMAIN

HOT BATTERYBUS

BATTERYCHARGER

BATTERYBUS

FFO

BATOFF

AUTO

STBY POWERBAT

BATTERYMAIN

DC BUSSTANDBYHOT BATTERY

BUS

L MAINDC BUS

L MAINAC BUS

BATTERYCHARGER

(FROM THE GROUND SERVICE BUS)

BATTERYBUS

AC BUSSTANDBYF

FO

HCSID

SI

NOT ON PANEL:FLOW LINES

LIGHT ILLUMINATED

DC POWER FLOWINGDC POWER NOT FLOWING

AC POWER FLOWINGAC POWER NOT FLOWING

HCSI

INV

INV

OFF

OFF

OFF


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The HDG provides AC power to: the left AC transfer bus the right AC transfer bus the standby AC bus (through the left AC transfer bus) the captains flight instrument transfer bus

The HDG provides DC power to: the hot battery bus the battery bus the standby DC bus.

The amount of DC power produced by the HDG is less than the DC power produced by a fully charged battery. When the HDG first begin to operate, the battery DISCH light may illuminate, until the battery power decreases to the power level produced by the HDG.

Battery/Standby System Schematic (Hydraulic Driven Generator Operating)

BATOFF

AUTO

STBY POWERBAT

ON

HYDRAULIC DRIVENGENERATOR

NOT ON PANEL:FLOW LINES

DC POWER FLOWINGDC POWER NOT FLOWING

AC POWER FLOWINGAC POWER NOT FLOWING

BATTERYBUS

CAPT FLT INSTRTRANSFER BUS

RIGHTTRANSFER BUS

LEFTTRANSFER BUS

L MAINDC BUS

BATTERYMAIN

HOT BATTERYBUS

BATTERYCHARGER

STANDBYDC BUSSTANDBYAC BUSF

FO

OFFDISCH


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Electrical EICAS MessagesThe following EICAS messages can be displayed.

Message Level Light Aural Condition

L AC BUS OFF

R AC BUS OFF

Caution BUS OFF

Beeper AC Bus is unpowered.

APU GEN OFF Advisory OFF APU generator control breaker is open due to a fault with the APU running.

BATTERY OFF Advisory OFF Battery switch is OFF.

L BUS ISOLATED

R BUS ISOLATED

Advisory ISLN Bus tie breaker is open due to an AC electrical system fault.

L GEN DRIVE

R GEN DRIVE

Advisory DRIVE Generator drive oil pressure is low or generator drive oil temperature is high.

L GEN OFF

R GEN OFF

Advisory OFF Generator control breaker is open.

MAIN BAT DISCH Advisory DISCH Main battery is discharging.

STANDBY BUS OFF Advisory OFF Standby AC or DC bus is unpowered.

L UTIL BUS OFF

R UTIL BUS OFF

Advisory OFF Galley and utility busses are unpowered.


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Electrical Panel

1 APU Generator (APU GEN) Control SwitchON (bar in view)

arms APU generator breaker to automatically close.OFF (bar not visible)

opens APU generator breaker resets fault trip circuitry.

2 APU Generator OFF LightIlluminated (amber)

the APU generator breaker is open because of a fault with APU running the APU generator control switch is selected OFF.

ONOFF

ISLN

AUTO

ISLN

AUTO

OFF

ON

OFF

ON

APU GEN EXT PWR

BUSOFF

ON

AVAIL

BUSOFF

ONOFF

DRIVE

BUS TIE BUS TIE

UTILITY BUS

L R R BUSL BUS

LGENCONT


L R

ONOFFDRIVE

OVERHEAD PANEL

1

2

3

4

5

6

7

8

9

10

11

12

13

14


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3 BUS TIE SwitchesAUTO

arms automatic AC bus tie circuits arms automatic DC bus tie circuits arms automatic flight instrument transfer bus circuits.

OFF (AUTO not visible) commands the AC bus tie open commands the DC bus tie open commands the flight instrument bus tie open resets fault trip circuitry.

4 AC Bus Isolation (ISLN) LightsIlluminated (amber)

a fault has occurred, automatically opening the AC bus tie breaker the BUS TIE switch is OFF.

5 AC BUS OFF LightsIlluminated (amber) the AC bus is unpowered.

6 Generator Control (GEN CONT) SwitchesON (bar in view) arms the generator breaker to close automatically when generator power is available.OFF (bar not visible)

opens generator breaker resets fault trip circuitry.

7 Generator OFF LightsIlluminated (amber) the generator breaker is open.

8 External Power (EXT PWR) SwitchPush if AVAIL light is illuminated, closes external power contactorSubsequent push opens external power contactor.

9 External Power ON LightIlluminated (white) external power is powering the bus(es).


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10 External Power Available (AVAIL) LightIlluminated (white) external power is plugged in and power quality is acceptable.

11 UTILITY BUS SwitchesON (bar in view) if no load shed signal is present, connects utility and galley busses to main AC bus.OFF (bar not visible)

disconnects utility and galley busses from main AC bus resets overload load shed circuitry.

12 Utility Bus OFF LightsIlluminated (amber) the utility and galley busses are unpowered.

13 Generator Drive Disconnect (GEN DRIVE DISC) SwitchesPush

disconnects generator drive from the engine requires maintenance action on the ground to reconnect the generator

drive.

14 Generator DRIVE LightsIlluminated (amber)

the generator drive oil temperature is high the generator drive oil pressure is low.

Battery/Standby Control Panel

ON

OFF

AUTOBAT

STBY POWER

OFF

FFO

BAT

HCSID

OVERHEAD PANEL

1

2

3 5

4


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1 Battery (BAT) SwitchON

Unpowered airplane on the ground: a few annunciator lights illuminate allows the APU to be started

Powered airplane inflight or on the ground when AC power is removed or lost: the standby and battery busses are powered.

OFF (ON not visible) turns battery power off.

2 Battery OFF LightIlluminated (amber) the battery switch is off.

3 Battery Discharge (DISCH) LightIlluminated (amber) the main battery is discharging.

4 Standby (STBY) POWER Selector OFF the standby busses are unpowered.AUTO the standby busses transfer to battery power if normal AC power is lost.BAT the standby busses are powered from the main battery.

5 Standby Power Bus OFF LightIlluminated (amber) standby AC or DC bus not powered.

Hydraulic Generator Test Switch

HYD GEN

ACCESSORY PANEL

1

1 Hydraulic Generator Test SwitchSpring-loaded to center.HYD GEN initiates hydraulic driven generator system test.


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Sistema Eléctrico B767-300

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