Electrical Flashcards
(42 cards)
a) Name one publication dealing with the storage of ship’s batteries. (2)
b) List SEVEN precautions that should be taken when working in an area where
batteries are stored. (14)
a.) code of safe working practice (COWSP)
b.) adequate ventilation must be used
no smoking, naked flames, sparks hot work or non approved electric tools
all appropriate PPE must be worn, like boiler suit and safety boots, especially when handling acid batteries
care should be taken when working on exposed battery terminals as electrical burns are possible and general good housekeeping used to ensure battery space is clean
do not use metal tools in battery space and remove all metal jewellery before entry as if metal comes into contact with battery terminals it will cause a short circuit.
battery cell caps should be securely tightened
do not mix battery acid in non approved containers
With reference to secondary cell batteries:
a) State the two types; (4)
b) State four applications on board ship; (4)
c) Describe the maintenance required.(8)
a.) lead acid
alkaline
b.) starting up a lifeboat engine
Aldis lamp - Aldis Lamps are typically positioned on the bridge wing of maritime vessels. They signal Morse code messages via flashing light and are still used to this day as way of communication between ships, both warfighting and merchant.
starting up an emergency generator
fire detection system
emergency lighting
GMDSS - Global Maritime Distress and Safety System
c.) batteries are stored in a hazardous space that must be cleaned. regularly carry out a specific gravity test. top up battery with distilled water if required. keep terminal connections secure and clean. make use of petroleum jelly, this is smeared on battery terminal to protect against corrosion. regularly check battery charge which is measured in voltage. to check voltage preform a test using a multimeter. Ensure batteries are stowed securely. Ensure light fixings are working and are correct type for space. ensure ventilation system is in good operation
With reference to electrical distribution systems:
a) State the meaning of the term earth fault; (2)
b) State FOUR different possible causes of an earth fault occurring in an electric
motor; (4)
c) State THREE undesirable consequences of earth faults; (3)
d) Describe ONE method of detecting earth faults. (7)
a.) when electrical current leads in an unintentional or undesired flow path to the ships hull, perhaps due to weak insulation where current can no longer be contained.
b.) - weak insulation so current can no longer be contained
- loose connections touch motor casing, which causes an earth fault
- motor overload which leads to insulation breakdown
- moisture or water ingress, where the motor has water damage
c.) The ships structure can become live risking the potential for a dead short between multiple phases, which can lead to a black out.
high oscillating current throughout the ships structure can cause overheating and sparking , which is dangerous for ships carrying explosive and flammable cargo.
overcurrent protective devices efficiency is reduced due to a reduced potential difference
d.) to detect an earth fault, earth lamps are used. earth lamps are connected from each phase to earth by a test switch in star. when no earth fault is present lamps glow with low and equal intensity. when an earth fault occurs between any phase to earth the lamp that has an earth fault will go dark and the other two will go brighter.
draw earth lamp system
a) State four different causes of earth faults. (8)
b) For EACH cause stated in (a) explain how the fault is rectified. (8)
a.) - weak insulation so current can no longer be contained as well as loose connections
- loose connections touch motor casing, which causes an earth fault
- motor overload which leads to insulation breakdown
- moisture or water ingress, where the motor has water damage
b.) To prevent earth faults it is important to ensure that all electrical components are properly installed and maintained.
Additionally, regular inspections should be conducted to identify any potential issues before they become serious.
Regularly check the integrity of the cables. Finally, any equipment that is exposed to moisture should be properly sealed and insulated to prevent the possibility of an earth fault.
if there are loose connections replace and secure the cables.
Use electrical tape to protect against electrical shock and short circuits. It can also be used to secure loose wiring, prevent interference between wires, and provide a moisture barrier. When using electrical tape, it is important to choose the right size and thickness for the job. electrical tape is a temporary solution , it deteriorate over time and can also be affected by heat or moisture. It is important to properly repair or replace damaged wiring to ensure safety.
Identify and mark the cable with a marker pen. labelling helps reduce the time it takes to track down and resolve an issue. labelling the cable to power source also ensures you are capable of easily tracing cables to power source, thus making equipment maintenance or replacements easier.
With reference to marine electrical distribution systems:
a) State the meaning of the term insulated neutral. (8)
b) Briefly describe how the location of an earth fault can be found. (4)
a.) Insulated neutral is a system where the main generator neutral points aren’t connected to the ships hull. This system is preferred to be used to be used on low voltage ships operating at 1000VAC because it prevents nuisance tripping of equipment. additionally it allows essential equipment like steering gear motors and navigational lights to run under a single earth fault connection.
- (draw system diagram)
b.) Earth faults are found by a process of elimination. crew is alerted, someone has to keep an eye on the fault monitor and then power can be switched off by racking the main circuit breakers in predetermined order and a general location is established, the exact location can then be found by preforming an insulation resistance test.
Explain the meaning of the term earth fault and state why it is undesirable in electrical installations. (6)
An earth fault occurs when electrical current leads in an unintentional flow path to the ships hull perhaps due to weak insulation or an exposed wire where electrical current can no longer be contained. a single earth fault can break down single phase winding, if not fixed then another earth fault can develop. when you have two earth fault this can lead to a short circuit, which causes fires and other problems. earth faults can be caused by loose connections or a motor overload which leads to a breakdown in insulation, moisture and water ingress. To fix weak insulation tie off or replace the cable so its not exposed. if the terminal box has moisture, replace the parts and seals and dry it out.
With reference to electrical motors:
a) List FOUR maintenance actions that are necessary for good operation. (8)
b) Describe how to test for electrical faults within in an electrical motor. (8)
a.) make sure the motor is tightly secured and free from vibration effect.
ensure resistance readings are good, this can be done by doing an insulation resistance test.
Check that motor shaft turns freely this can be done turning the shaft by hand when the motor is disassembled and maintenance is being done.
ensure bearings are greased but not overly greased, to prevent wear and tear or any damage.
ensure motor is kept clean and cooling fins are free from dust and moisture residues to prevent water ingress damage and overheating problems.
make sure motor is dissipating heat correctly and there is good ventilation.
ensure electrical connections are secure and correctly labelled.
regularly inspect motor windings to check integrity.
b.) before doing any electrical tests a permit to work must be obtained and a risk assessment carried out to put in place control measures.
to test for electrical faults an insulation resistance test can be done using an insulation resistance tester.
ensure the motor has been isolated and its safe for a electrical test to be carried out.
before carrying out an IR test ensure IR tester is working by touching the two probes together and pressing the test button.
the IR tester should read 0 ohms. this test is done to ensure copper phase windings are adequately insulated from each other. use the IR tester and test probes to test phase to phase. For example U to V, V to W, U to W. ensure readings are a minimum of 1Mohm at 500VDC test voltage, to prove for good insulation.
also check windings are insulated from ground. these readings must be done U to ground, V to ground and W to ground.
another test that can be done is a continuity test. this is done to check the condition of the windings. use a multimeter and set it to ohms and test between each phase. for instance U1 to U2, V1 to V2, W1 to W2. ensure readings are a minimum of 1Mohm.
one other test that can be preformed on an electric motor is a current draw test. this is done to check the current is balanced between the phases and that it matches full current load value on the motor name plate. use a clamp meter on each motor phase and check that current is similar or same to ensure current between phases is balanced.
a) Describe how you would overhaul an electric motor that has been flooded with sea water. (8)
b) Explain how to check the insulation resistance of the motor, stating the
minimum acceptable value. (8)
a.) Before you can overhaul an electric motor a risk assessment must be carried out and an electric permit to work must be obtained. then isolate the motor by using the lock out tag out method. dismantle the motor in to two parts the rotor and the stator. bring the parts to the workshop and clean them with freshwater to clean off the salt and seawater ingress damage. once all parts have been cleaned, dry out each part in a dry room, or with a hair dryer or electric heater. once all parts are dry apply varnish to the stator windings. once the varnish has dried electrical tests should be carried out. This includes an insulation resistance test to check for good insulation from phase to phase and phase to ground, to check phases are insulated from the earth. a continuity test to check condition of windings and a current draw test to check current is balanced between phases and it matches full current load provided on the motor name plate. if all test results are acceptable then motor can be reassembled with new bearings and then taken back to the engine room to be put back into service.
b.) before conducting an insulation resistance test you must ensure motor has been safely isolated and test prove test prove is done to ensure equipment is dead. ensure certified and appropriate rated test instruments are used. With the aid of an of an insulation resistance tester set to ohms with a test voltage of 500VDC on a 440VAC motor, touch the two test probes and press test to check equipment is working. then two sets of readings should be obtained one set of readings to test phase to phase. for example U to V, V to W and U to W. the other set of readings is to test phase to ground, so U to E, V to E and W to E. phase to phase readings will check if windings are insulated and phase to earth will check if windings are insulated from earth. the minimum acceptance value is 1Mohm if below this value this shows poor insulation, if reading is 1Mohm or above this shows good insulation. keep a record of the readings for trending purposes and to use as a guide to predict any problems that might occur.
With reference to the testing and maintenance of large electric motors:
a) State the minimum satisfactory value of insulation resistance. (2)
b) State the instrument AND the voltage to be used for the insulation resistance
test. (4)
c) State the regular maintenance that is necessary for good electric motor
operation. (10)
a.) The minimum satisfactory value for insulation resistance is 1Mohm
b.) To preform an insulation resistance test an insulation resistance test an insulation resistance tester is used, the voltage to be used is 500VDC for a 440VAC motor.
c.) regularly check motor connections are tightly secured and motor is free from vibration.
ensure regular insulation resistance readings are taken and recorded for trending and fault finding purposes.
make sure motor shaft turns freely by hand
make sure bearings are greased regularly but not overly to prevent seizing
make sure motor body is kept clean and the cooling fins to prevent overheating and ensure there is no water ingress damage
make sure motor dissipates heat quickly and is well ventilated.
ensure motor windings are secure and correctly labelled
regularly check the motor winding conditions and integrity
regularly preform a continuity test to check condition of windings and do a current draw test to check current is balanced between phases and it matches full current load value on motor name plate
With reference to small 3 phase electrical motor, driving a transfer pump that is not used on a regular basis, failing to rotate when the start button is pressed:
a) Outline the procedure to determine the possible cause (8)
b) Explain the procedure to remove the motor should it be faulty and require
changing (8)
a.) There are two possible reasons for this motor not starting on e being an electrical problem and the other a mechanical problem.
- mechanical problems
- one problem could be the motor bearing or gear have seized. to rectify this problem use bearing grease to lubricate the parts. if motor runs when bearings and gear have seized this will lead to overheating.
- another mechanical problem is the motor shaft has seized and will not turn. check to see if shaft can be turned by hand regularly.
- one other problem could be pump blockage, dismantle or detach pump to determine the possible cause.
- electrical problems
- The motor fuse has been blown so there’s no power. Do a voltage test with a multimeter to check its condition if dead replace fuse
- main circuit breaker has tripped due to a short circuit fault, check if breaker is stuck in the trip position
- motor has suffered an overcurrent trip due to excessive current from motor being drawn to a seized motor shaft. push the reset button on the OCR (overcurrent relay) and see if relay resets.
b.) prior to removing a motor a risk assessment must be carried out and an electrical permit to work must be obtained. then ensure to isolate the motor mechanically and electrically following the ships SMS requirements. to isolate motor electrically rack out the main circuit breaker to switch off the power. then do a prove test prove to check voltage readings with a multimeter to prove motor has been isolated. Then do a lock out tag out method and post signs and notices to let crew know maintenance is being carried out. ensure correct PPE tools, sufficient lighting and appropriate lifting equipment is available. motor can then be uncoupled from the pump and safely stowed to a designated storage space. work area must then be secured until a new motor is fitted to protect the pump.
With reference to electrical motors:
a) State the routine maintenance that is necessary. (8)
b) Describe the tests carried out to prove good electrical condition. (8)
With reference to the emergency generator:
a) state the checks required prior to starting the engine: (6)
b) describe the routine testing. (10)
a.) check emergency generator FO tank level by visually checking the fuel gauge
check LO sump tank by using the dipstick
check condition of emergency generator batteries
checking cooling water temperature, LO and FO temp
check cooling water level
check turbo charger oil level
check cooling water pressure, lube oil and fuel oil pressure
visually check around the emergency generator for any leaks and listen for any abnormal noises.
b.) the generator onboard a ship is generally tested offload once a week and onload once a month. the following procedure is followed to test a generator offload.
switch generator from automatic to manual control on the control panel
press the start button on the control panel to start the generator engine using the batteries
let the engine run up to speed and let parameters stabilise
check LO pressure and temperature, cooling water temperature and engine rpm
monitor output voltage and frequency
generator can then be stopped using the stop button at the control panel once the person testing the generator is satisfied that everything is working. afterwards switch the generator back to automatic control.
offload testing means he generator isn’t connected to the main bus bar and isn’t supplying any electrical power so hasn’t taken on any load
onload testing is when the emergency generator is connected up to the main bus bar and is underload producing electrical power to essential emergency equipment like emergency lighting, fire detection system, etc
State the procedure to be carried out if you found someone you suspected of
having received an electric shock. (16)
Danger Response Airway Breathing Circulation
firstly i would call the bridge for help and let them know any significant details and ask for assistance. visually look around surroundings to check if it is safe to approach the casualty. approach the casualty with extreme caution to make sure i don’t become a casualty myself. use an electric hook to remove casualty from electrical source. once casualty is away from the electrical source of power, check for a response and if necessary provide first aid and or use the CPR procedure. check the casualty’s airway and if conscious and breathing put them into a recovery position and continue monitoring the casualty condition. if necessary contact shore side medical assistance. ask a crew member for a defibrillator to help provide verbal communication to know when to preform CPR and apply shock.
State the safety precautions to be taken before investigating faulty electrical machinery. (4)
A risk assessment is carried out by a competent person to put in place control measures. The electrical equipment must be safely isolated and a lock out tag out method used. A prove test prove is carried using a multimeter to test for voltage, this done to ensure equipment has been safely isolated. An electrical permit to work must be obtained to ensure work has been authorised and to make a high risk electrical task safer.
a) List FIVE precautions that should be taken before any work is carried out on
electrical equipment. (10)
b) Identify THREE additional precautions to those in Q3(a), if it has become
essential to work near to live equipment. (6)
a.) a risk assessment should be carried out before hand by a competent person to put in place control measures.
electrical equipment must be safely isolated and a lock out tag out method used.
carry out a prove test prove using a multimeter to test for voltage, this is done to ensure equipment is isolated.
an electrical permit to work must be obtained before doing any work.
use sign if working on live equipment, danger sign if working on live equipment and caution if on dead equipment.
correct PPE must be worn like a boiler suit and safety boots, gloves etc. to provide some protection from injury
b.) Introduce safety barriers to ensure engine room crew are aware that live electrical work is being carried out and not to enter the space.
Have another competent person assist you with the work to reduce risk of injury and provide some insight
Use electrically rubber insulated mats to provide further protection make sure they’re flat to surface.
a) State THREE underlying causes of electrical equipment failure. (6)
b) State the precautions to be taken before working on the switchboard. (10)
a.) Overloading - when the current has increased over the full load current causing am overload or overcurrent trip
Insulation failure - cable has been exposed or damaged and can no longer contain current
Misuse - when electrical equipment hasn’t been operated or used correctly
b.) Have a competent officer with you to provide assistance, reduce risk of injury and provide technical support.
Ensure you have electrical PPE on and you use insulated tools beforehand and ensure they’re working
Use electrical rubber insulated mats and ensure they’re rated to the voltage of the live equipment you’re working on
Have an electrical rescue hook on standby if available so that if necessary you can pull a casualty away from a live electrical source.
Control access to the area by using safety barriers or tape and signs to signs to make crew aware of where its safe to work
Ensure any conductive metals or objects are at a safe distance away from any live equipment
Isolate electrical power to the switchboard by racking/closing off the circuit breaker feeding the electrical machinery
Use a lock out tag out method to secure and warn against re-closing the circuit breaker
Use a multimeter to test for voltage and thereby carrying out a prove test prove to ensure equipment is isolated
Carry out a risk assessment to introduce Control measures and obtain a permit to work to ensure work is authorised and to minimise risks
Describe the procedure for running up and paralleling an alternator onto the switchboard. (16)
ensure crew aren’t doing any maintenance on the generator before its started.
all machinery covers and guards must be in place.
carry out all pre-start checks before hand. this includes a visual inspection of starting air, control air, fuel supply and cooling system pipes and associated equipment for leaks or any abnormalities.
check the LO level in sump tank is adequate by using dipstick high and low level markings.
start the lube oil priming pump and visually inspect to ensure running normally, wait for pressure on gauge to rise to normal.
then open all indicator cocks, ensuring the fuel oil supply is closed as this is the engine blow down stage and then engage the turning gear.
go to local control panel to ensure engine is switched to local control and fuel notch handle is at the correct position (stop), push the start button on control panel to blow engine by air.
blow down procedure is carried out to purge cylinders and indicator cocks of debris, oil moisture or water.
then disengage the turning gear, close all indicator cocks and open fuel supply, afterwards raise fuel notch handle and press start button at local control panel to start generator.
do another safety round to check visually for any leaks or abnormalities whilst generator is running.
before going to engine control room switch generator from local to remote. go to control room to monitor all pressure and temperature parameters, wait for them to stabilise.
keep an eye on the voltage, wait for it be equal to bus bar voltage, set by the AVR, switch synchroscope on and turn selector switch to generator that is being synchronised.
observe the synchroscope rotation and using the governor control, adjust the incoming frequency so its slightly faster than running generator, this is shown by the synchroscope turning slowly clockwise.
when synchroscope is at the 11’oclock position close the circuit breaker to allow for a delay in human reaction time.
when the circuit breaker is closed it will be at the 12’oclock position so phase sequence will be equal.
at this point incoming generator will synchronise with running one and start to produce power.
now the fuel and speed needs to adjusted to balance out the load for both generators.
to do this use the governor controls and carefully adjust till both generators are sharing load at 50%, then finally switch the synchroscope off.
Describe the conditions that must be satisfied before paralleling an a.c.
generator with the main electrical switchboard. For each condition described explain how it is achieved. (16)
One condition that must be met before paralleling a generator onto a switchboard is the voltage has to be kept the same for both incoming and running generator. To keep the voltage the same observe the voltmeter, adjustment are made by the automatic voltage regulator (AVR) manual voltage timer found at the switchboard.
Another condition that must be met is the frequency for both generators must be kept the same. This can be achieved by observing the frequency meter and using the governor controls on the synchronisation control panel to adjust the frequency.
The governor controls can also be used to keep the voltage for both generators in same phase rotation. This is done by observing the synchroscope phase rotation indicator and making any adjustments with governor controls provided on the main switchboard synchronisation panel.
a) State the conditions that must be satisfied before paralleling an a.c. generator
with the main electrical switchboard. (6)
b) For EACH condition stated in (a) explain EACH of the following:
(i) how it is monitored (4)
(ii) how it is adjusted (6)
a.) - Voltage for incoming and running generator must be kept the same
- Frequency for incoming and running generator must be kept the same
- Voltage for incoming and running generator must be in same phase rotation
b.) (i) - In order to monitor the voltage and keep it the same you must observe the voltmeter found on the synchronisation panel.
- To monitor the frequency for both generators so that it can be kept the same you must look at the frequency meter on the main switchboard.
- To keep the voltage in same phase rotation monitor the synchroscope
(ii) Voltage for incoming and running generator is adjusted by the AVR manual voltage timer.
Governor controls provided on the main switchboard generator synchronisation panel can be raised or lowered to adjust the frequency for the incoming and running generator as well as to keep the voltage in same phase rotation for both generators. When adjusting observe the voltmeter and frequency meter and make sure they match, use the governor controls for incoming and running generator one at a time and carefully so that paralleling is easier.
Describe how to manually couple a second auxiliary generator to the main
switchboard and balance out the load. (16)
Firstly before paralleling a generator onto the switchboard and balance out the load you have to carry out all pre start checks such as, doing a visual inspection of the air starting system, control air, fuel oil supply and cooling system pipes and associated equipment for any leaks or abnormalities. Check the LO sump tank level by oil dipstick high and low level markings. Start the LO priming pump and check suction and discharge pressure by using gauges. Then carry out a blow down procedure to purge the cylinders and indicator cocks of any debris, oil and water moisture and then engage the turning gear. Afterwards disengage the turning gear and open fuel supply, start engine from local control panel and raise the fuel notch. Before then heading to ECR switch generator from local control to remote. When you’ve arrived in ECR monitor the pressure and temperature parameters and wait for them to stabilise. Go to generator switchboard and turn on voltmeter and frequency meter. check to see if the incoming generator voltage is the same, if not then adjust by the AVR. Check if the frequency of incoming generator matches if not then adjust by raising or lowering the governor controls. Then turn on the synchroscope and ensure it runs in clockwise direction, this can be adjusted by using governor controls as well. Allow the synchroscope to operate at a rate of 4-5secs per revolution. Afterwards close the main circuit breaker for the incoming generator when the synchroscope is at the 5to12 position. This is to allow for a delay in human reaction time so the phase sequence will be equal. Let both generators run steadily so incoming generator can synchronise with running one and then start to produce electrical power. At this stage auxiliary generator load needs to be balanced out by adjusting the fuel and speed. To achieve this use the governor controls to increase fuel/speed of incoming generator slightly and decrease the fuel/speed of running one slightly. This adjustment will increase the KW of incoming generator and decrease the KW load from running one. Continue to adjust the KW load sharing until both generators load is evenly balanced
Explain the procedure to be taken in EACH of the following circumstances in order to prepare a large electrical generator set for maintenance:
a) taking the a. c. generator off electrical load; (6)
b) isolating the machine in order that work may be safely carried out. (10)
a.) on the generator synchronisation panel, put the selector switch from auto to manual. this is done to allow for manual control of generator that is going to be taken offload. keep all other generators on auto. then using the governor controls slowly unload the generator by lowering the fuel intake so that speed and load can be reduced. the speed and load for the running generators will adjust automatically to maintain 60hz and so only monitor the parameters. when the generator load has dropped to a safe level, about 50KW, open the main circuit breaker by turning the ACB (air circuit breaker) control knob to open. afterwards readjust speed and check running generators are maintaining load and running at 60Hz. let generator run a bit for cooling down purposes before securing. finally stop engine by switching control knob to stop on switchboard panel and then ensure engine has fully stopped so isolation of prime mover an alternator can start.
b.) in order to carry out maintenance on a generator the alternator and prime mover has to be isolated. to isolate a prime mover stop or shut down G/E and switch from manual to local control. isolate fuel supply by closing and locking off fuel valve. then close the starting air valve, remove the turning bar to engage interlock. Then isolate the lube oil and jacket water cooling system. to isolate the alternator simply rack out the main circuit breaker and put into lock position whenever any isolation is complete post notices to make crew aware.
a) List FIVE protective devices fitted to a main electrical switchboard. (10)
b) State the precautions to be taken before working on the switchboard.
a.) Overcurrent trip relay - when there is a small increase over the full load current. On a motor an overload trip is detected by an overcurrent relay.
Undervoltage relay - when there is a 50% or more voltage drop due to a release mechanism fitted on a G/E circuit breaker. Prevents a circuit breaker of a dead generator being closed on a live bus bar.
Preferential trip - used as protection to prevent a generator being overloaded by shedding off non essential electrical load in the event of an overload trip. After a time delay a preferential trip relay will switch off a predetermined set of non essential loads
Main circuit breaker - fitted as a protection device to prevent a generator from being damaged from an overcurrent trip
Reverse power trip - fitted to avoid loss of electrical power. Its when a generator consumes power instead of generating it. Its also known as a motoring effect where running generator can’t cope with electrical load from the one running in reverse so it will trip due to a reverse power relay.
b.) Have a competent officer with you to provide assistance, reduce risk of injury and provide technical support.
Ensure you have electrical PPE on and you use insulated tools beforehand and ensure they’re working
Use electrical rubber insulated mats and ensure they’re rated to the voltage of the live equipment you’re working on
Have an electrical rescue hook on standby if available so that if necessary you can pull a casualty away from a live electrical source.
Control access to the area by using safety barriers or tape and signs to signs to make crew aware of where its safe to work
Ensure any conductive metals or objects are at a safe distance away from any live equipment
Isolate electrical power to the switchboard by racking/closing off the circuit breaker feeding the electrical machinery
Use a lock out tag out method to secure and warn against re-closing the circuit breaker
Use a multimeter to test for voltage and thereby carrying out a prove test prove to ensure equipment is isolated
Carry out a risk assessment to introduce Control measures and obtain a permit to work to ensure work is authorised and to minimise risks
Explain why EACH of the following protective devices are fitted to a main
electrical switchboard (4 marks each)
Reverse power.
Under voltage.
Main circuit breaker
overcurrent.
Preference trips.
Reverse power - used on a switchboard to avoid loss of electrical power and damage to machinery. Reverse power is also known as motoring effect, it occurs when a generator a is consuming power instead of producing it. A running generator will not be able to cope with the electrical load of motoring one and will therefore trip once detected by a reverse power relay
Undervoltage - occurs when the average voltage of equipment falls below rated voltage amount. An undervoltage relay is fitted as protection to prevent circuit breaker of a dead generator being closed onto a live bus bar. Closing the circuit breaker would cause a three phase short circuit fault
Main circuit breaker overcurrent- a main circuit breaker is used as protection to prevent damage from overcurrent, which is current above full current rating of the generator
Preferential trip - protection fitted on a generator to prevent overloading by shedding the generator off non essential electrical loads. In the event of an overload, after a time delay the Preferential trip relay will switch off a predetermined set of non essential loads
What protective device stops a main circuit breaker being closed when the generator is not running. (4)
Undervoltage occurs when the average voltage of equipment falls below rated voltage amount. An undervoltage relay is fitted as protection to prevent circuit breaker of a dead generator being closed onto a live bus bar. Closing the circuit breaker would cause a three phase short circuit fault
