A busbar is a copper plate/bar which is used in ship’s main and emergency switchboards to conduct electricity from generators or from one electrical terminal to another. Technically, there are no electrical wire connections inside the main and emergency switchboards on ships for connecting Power supply from generators to these switchboards. All high voltage and high current systems are connected by bus bars.
The busbar’s copper plates/ bars are connected together with the help of nut bolts, which transmit electricity as required. During normal ship operations, the busbar connections are subjected to ship’s harsh environment along with the vibrations generated by the ship and ship machinery such as Main Engine, auxiliary engines, compressors etc. These vibrations cause loosening of nut bolts in the busbar, which can lead to short circuit or any other type of accident. Loose connections inside the switchboard can also lead to sparks that can cause fire.
Moreover, the busbars are meant to carry high voltage and current which tend to heat up the lines due to energy flow in the system. For this reason, inspection and maintenance of busbar at regular inspection of time are required for smooth operation.
If any maintenance is planned for busbars, highest standards of safety are required as even the tiniest mistake can lead to electrocution and even death. The busbar maintenance is therefore performed when the complete busbar panel or Switchboard is turned “OFF”. Following are the precautions for safety to be carried out when the bus bar maintenance is to be carried out:
When the bus bar maintenance should be done?
- Bus bar maintenance can be done when the ship is in black out condition, i.e. ship’s generators are not running and no power is supplied to main or emergency switchboards
- If the main switchboard busbars are to be inspected or to be work on, keep emergency generator running. Keep in mind that there will be some portion of the main switchboard which will be fed by emergency switch board. Hence know the complete system properly and keep away from those areas
- The best time to do bus bar maintenance is when the ship is in the dry dock
Safety before doing bus bar maintenance:
- Put the “lockout” tag in all generators and in the emergency generator
- Keep all the generator system including load dependent start stop system in manual mode
- Ensure to wear rubber gloves even when the board is not in “Live” condition
- Wear all required personal protective equipment (PPEs) when working on switchboard
- If the ship is in complete black out situation, ensure that before cleaning the main and emergency switchboard, the area is well lit by sufficient lights. In dry dock same can be arranged from shore workshop
How Busbar Inspection and maintenance is carried out?
Any maintenance on busbars should only be performed when the ship in Dry dock or Black out condition:
- Open the door for main and emergency switchboards where inspection is to be performed
- Carryout visual inspection of copper plate and nut bolts. Mark any missing or burn out areas
- By hand or using a metal or plastic stick (where access for hand is not possible), tap the bus plates gently so as to make out for any loose connection. Ensure to wear electrical gloves even when bus bar is not live
- The busbars are mechanical supported inside the switchboard by means of insulators, which may be of rubber or ceramic materials (bad conductors). Check for any damages in the insulator part
- By using only dedicate size spanner or pre adjusted torque wrench, tighten the nuts in the busbar connection for main and emergency switch boards
- Check the tightness of the wire connections, which is connected to the circuit breakers
- Clean the bus bar and switchboard area with the help of vacuum cleaner
- If u find any loose connection or spark, black-out the particular and adjacent bus bar before tightening the nut
- If u find any metal piece or nut bolts missing or inside the panel, ensure to remove it as the same can cause short circuit or fire
The ship’s electrical officer is required to inspect the busbar periodically for record keeping and also as stated by the preventive maintenance system. This is done to avoid any type of accident from electrical faults on ships. When doing such inspection the following highest safety measures are to be taken with all required PPEs as the Bus bar is “LIVE”:
- Check the load in the running generator by means of KW meter provided in the main switchboard.
- Open the bus bar access door provided at the backside of MSB or ESB.
- Do the visual inspection and by the help of infrared temperature gun, measure the temperature of copper plates and bus bar connection.It should not be more than given limits depending upon the generator load. Example if the generator load is 50%, the room temperature is 28 deg c, the bus bar temperature must be within 50 deg c, if the temperature is too high then some thing is abnormal.
Once the inspection and maintenance is completed:
- Close the bus bar access doors
- Remove the lock out tag
- Restore the main power supply by the generators
- Inform the Chief Engineer and the in-charge of that particular machinery regarding the same
- Reset the main power and check if there is any abnormal sound in main switch board and emergency switch board
- Monitor the temperature of the busbar area with laser temperature gun
- Keep the emergency switchboard in the auto mode
How do you carry out busbar maintenance on board ships? Let us know in the comments below.