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Preparation and checks before drydock for receiving shore power:
A chief engineer to ensure the following checks are made to ensure safe operation.
ship’s electrical engineer will prepare the ship’s power receiving terminal box and should do following things:
- Ensure the receiving box is not obstructed with any object, pipes or spares. It is usually located either on the deck near accommodation entrance or the emergency generator room
- If the box is not used or maintained for long, clean the box and ensure the safety door hinges and locks are functioning smoothly
- Ensure all the receiving terminals inside the box are present and in good working condition
- Ensure earthing cable is provided to earth the ship’s hull to shore earth
- Ensure measuring instrument such as voltmeter, phase sequence indicator, and tester etc. are present
- Ensure the indication of shore power (in the form of light bulb) is present and working
- Ensure a safety device (circuit breaker or fuse) is provided in the terminal to protect the MSB of the ship
- Ensure details of shore power requirement is pasted near the shore receiving terminal box, which includes required voltage, frequency, and method of connecting the shore supply
- Ensure the ship’s batteries are tested for full charging
Following things to be checked before connecting shore supply to ship in a drydock:
- Check the cable drawn to ship for providing shore supply is in excellent condition
- Check the insulation resistance of the cable provided for the shore supply
- Check the insulation resistance of the shore supply box
- Check the polarity of shore supply using a voltmeter
- Check and ensure the frequency and voltage of shore supply are matching with the specifications required by the ship
- Check the phase sequence of the shore supply using phase sequence tester
- Check the tightness of the shore cable connector clamp to ensure they are not loose
- Ensure to display notice near the vicinity of ship’s receiving terminal box about high power cable in use
- Check and ensure the ship’s generators are disconnected from the Main Switch Board of the ship
- A responsible officer must check and record the energy meter reading provided on shoreside
- Ensure ship’s hull is earthed to the shore before supplying shore power to the ship.
Once all checks are performed by ship’s engineer and the ship is ready to take the shore power, take the following steps:
- Once the shore supply power is made available to the vessel, the light indicator provided in the terminal box will be ON
- Close the breaker to start the supply of the shore power to ship
- For checking the phase sequence, a bulb type phase sequence indicator can be used in which two lamps are connected to unbalanced load across the 3 phase via capacitor and resistors. The phase sequence will be considered “OK” when the right side lamp is bright, and the left side one is dark
- Another instrument used to measure PSI is a small portable 3 phase induction motor driven meter with a rotary pointer
- Check the frequency of the supply from the provided frequency meter or on the Main Switch Board of the ship
- Ensure to keep the emergency generator in manual mode to use the same if the shore power goes off abruptly and electricity supply is needed
Common problem faced by ship’s staff while taking shore supply-
- Shore supply switched on, but the ship is not getting power
- Check the three fuses connected between the ship’s terminal and Main Switch Board (MSB)
- Check the circuit breaker located in shore supply switchboard
- Check circuit breaker interlocks which are arranged in the system to avoid paralleling of shore and generator power
- Shore power trips during supply
- Faulty shore cable. Ensure the cables used for supplying power is of proper size and as per the maximum protective current value of the ship.
- Overload in the system. Ensure to correctly calculate the electrical load of the ship during the drydock using electric power balance table to avoid overload trip.
Generator circuit breaker trip: It is possible that the safety breaker for the generator trips the shore supply during the inspection or maintenance of generator’s interlock.
- Wrong shore supply
Most countries have their local regulations which make the shore supply compulsory to avoid emission problems. If the voltage and frequency of shore power do not match with the ship’s rating, the machinery will operate at lower efficiency and may face overheating problems. The ship manager must ensure to choose a drydock, which can provide shore supply as per the ship’s requirement.
quote: https://www.marineinsight.com/tech/procedure-take-shore-power-dry-docking-ships/
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