Paralleling Generators & Load Sharing Flashcards
(15 cards)
Describe how to manually couple a second generator to the main switchboard and balance out the load
Assuming the generator is running at full speed.
- Pre Checks (oil, coolant)
- Select Manual
- Runup Standby Generator
ENSURING PARAMETRES - Check that the Voltage of the incoming and running generators are the same. (use AVR to adjust the voltage if necessary)
- Check that Frequency of incoming and running generators are the same. (use governor controls to adjust if necessary)
- 480V, 60Hz
- Switch on Synchroscope and it should be observed as running in a clockwise motion at a speed of 5 seconds per rev.
CONNECTING THEM - Close circuit breaker when synchroscope is at 5 to 12 position.
- Switch off synchroscope (not meant to be ran constantly)
- Increase fuel of the incoming generator and decrease fuel to the running generator (using governor), This is adjusting the KW load over the two generators, continue until load is evenly shared.
State the reequipments for connecting an incoming alternator to live busbar
- Same Voltage
- Same Frequency
- Same Phase Angle
- Same Phase Sequence
State the possible consequences of incorrect paralleling
- Overheating or fire in electrical components due to circulating currents.
- Damage to prime mover from sudden load changes or mechanical stress.
- Failure of prime mover if synchronization is poor or load sharing is uneven.
- Potential blackout if generators trip or protection systems activate.
Explain how the main circuit breaker for an alternator that is not running is prevented from being accidentally connected to a live bus bar
The main circuit breaker has an interlock that prevents it from closing if the alternator is not running or not synchronised with the live bus bar.
State the conditions that must be satisfied before paralleling an a.c generator with the main electrical switch board
- Same Voltage
- Same Frequency
- Same Phase Angle
- Same Phase Sequence
Explain how EACH of the conditions are monitored
Voltage, Frequency, Phase Angle, Phase Sequence
Voltage - Voltmeter
Frequency - Frequency Meter
Phase Angle - Monitored on the Meter
Phase Sequence - Seen on the Synchroscope
Explain how EACH of the conditions are adjusted
Voltage, Frequency, Phase Angle, Phase Sequence
Describe how to manually couple a second generator to the main switchboard and balance out the load
Assuming the generator is running at full speed.
- Pre Checks (oil, coolant)
- Select Manual
- Runup Standby Generator
ENSURING PARAMETRES - Check that the Voltage of the incoming and running generators are the same. (use AVR to adjust the voltage if necessary)
- Check that Frequency of incoming and running generators are the same. (use governor controls to adjust if necessary)
- 480V, 60Hz
- Switch on Synchroscope and it should be observed as running in a clockwise motion at a speed of 5 seconds per rev.
CONNECTING THEM - Close circuit breaker when synchroscope is at 5 to 12 position.
- Switch off synchroscope (not meant to be ran constantly)
- Increase fuel of the incoming generator and decrease fuel to the running generator (using governor), This is adjusting the KW load over the two generators, continue until load is evenly shared.
Explain why the protective device “Revers Power” is fitted to a main electrical switchboard
WHY IT IS FITTED
- To avoid the loss of electrical power and possibly damaging the generator set.
WHAT IT IS
- Reverse power trip happens when a generator starts to act like a motor, the generator then starts to take power from the bus bar instead of supplying it.
CONSEQUENCES
- This can damage or cause failure of the prime mover (engine or turbine)
Explain why the protective device “Under Voltage” is fitted to a main electrical switchboard
WHY IT IS FITTED
- To prevent the circuit breaker of a dead generator to be closed on to a live bus bar.
CONSEQUENCES
- Closing a dead generator on a live busbar will equal to a three phase short circuit.
MORE INFO
- It also trips during a sever voltage drop (usually around 50%), when the voltage drops a mechanical latch lifts, causing the breaker contacts to open protecting the system.
Explain why the protective device “Main Circuit Breaker Overcurrent” is fitted to a main electrical switchboard
WHY IT IS FITTED
- To prevent the generator from damages of overcurrent, usually by overheating.
Explain why the protective device “Preference Trips” is fitted to a main electrical switchboard
WHY IT IS FITTED
- To prevent the generator from overloading.
WHAT IT IS
- In the vent of overcurrent, all non essential services will be tripped in stages.
First Stage - Non-essential Loads (galley, air conditioning, laundry)
Second Stage - Semi-essential Loads - (deck machinery, cargo pumps)
Final Stage - Essential Loads - (Navigation and safety systems are maintained while everything else is disconnected)
State why preference trip is fitted
To prevent the generator from overloading.
Explain the operation of a THREE stage trip
In the vent of overcurrent, all non essential services will be tripped in three stages.
First Stage - Yellow
Non-essential Loads (galley, air conditioning, laundry)
Second Stage - Blue
Semi-essential Loads - (deck machinery, cargo pumps)
Final Stage - Red
Essential Loads - (Navigation and safety systems are maintained while everything else is disconnected)
State THREE circuits that can not be connected to the preference trip giving a reason for EACH
Emergency Lighting - Must remain on during power loss for safety and evacuation.
Fire Detection and Alarm Systems - Critical for detecting and responding to fires, cannot be interrupted.
Steering Gear - Essential for ship control and must always be powered for safe navigation.
