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28/05/2024

Low insulation 440V. First actions of the ETO

Greetings! Today we will analyze the sequence of actions of an electrician when finding the source of low 440V insulation on the vessel. In the previous article we looked at the first actions of the ETO when searching for low insulation 220V, I recommend reading that article first, because it is more detailed. And the search methods are not much different, but there are nuances.

Low insulation 440V. First actions of the ETO

Finding low 440V insulation on a vessel involves tripping the circuit breakers one at a time, starting with the non-critical consumers. 

It may happen that the reason for low insulation is immediately known, because a 440V high pressure machine was started on the deck and perhaps it was flooded with water. But it happens that you cannot find the source on the first try.

When disconnecting breakers, you need to pay attention to the pointer megohmmeter, which is located on the 440V feeder panel of the main switchboard. 

Pointer megohmmeter
Pointer megohmmeter

This device instantly shows the change in insulation resistance when disconnecting consumers with low insulation relative to the ship's hull (the arrow goes to infinity).

Circuit of operation of a pointer megohmmeter
Circuit of operation of a pointer megohmmeter
Ground monitor
Ground monitor

The grounding monitor is a key device for measuring the insulation resistance of the entire power circuit and issues a corresponding signal (alarm) if the resistance values reach the set point (For example, 0.2 MOhm).

List of circuit breakers when searching

Below I propose to familiarize yourself with the list of circuit breakers that I turn off sequentially when the 440V insulation is occured. This sequence or list may vary depending on the type of vessel, but is suitable for most.

  1. The first breaker I usually turn off is the galley and laundry.
  2. The second breaker is deck machinery and 440V sockets on deck (high pressure machines, cranes, ladder winches, mooring winches, windlasses, capstans, etc.). Of course, cranes should not be turned off during cargo operations, and deck winches should not be turned off during mooring operations.
  3. The third breaker is air conditioning and ventilation systems (superstructure and engine room).
  4. The fourth breaker is auxiliary mechanisms, the shutdown of which will not entail a blackout of the vessel or a stop of the main engine (on the move). For example, cathodic protection, ballast pump, etc.
  5. The fifth breaker is responsible devices, but first it is advisable to switch to a backup (standby) system, if possible. For example, start the second main engine Lube oil pump and stop the first one, which needs to be checked.

Search for low insulation

Suppose a low insulation 440V came out, we found that this is a group 5 circuit breaker, which includes galley equipment.

Low insulation alarm 440V
Low insulation alarm 440V
Group 5 breaker (galley)
Group 5 breaker (galley)
Scheme of the 5th consumer group
Scheme of the 5th consumer group

Turning off the power one by one and checking each breaker in this group, we find that this is cooking range in the galley.

Bottom left plate
Lower left hot plate
Checking the hot plate
Checking the hot plate

Checking each hot plate, we conclude that the lower left hot plate with low insulation, also requires replacement of the cable and contact group (as you can see on the photo). 

It is important to understand that if the switch on the hot plate is turned off while the plates are being tested, the device may not show low insulation. Because it will “check” only the circuit up to the switch and the switch itself; it will not check the hot plate if the switch not opens its contact.

Scheme of operation of an electric hot plate of 4 elements and an oven
Scheme of operation of an electric hot plate of 4 elements and an oven

We install a new plate and thus eliminate the low 440V insulation.

Which equipment most often gives low 440V insulation?

  • heating elements (heating elements) (heaters, heaters in boiler and auxiliary engine systems, electric heaters of the main engine); 
  • hot plates and ovens in the galley;
  • dryers and washing machines (440V); 
  • high-pressure deck machines, submersible motors/pumps; 
  • electric motors of mechanisms that are located on the open deck.

In this way, low 440V insulation on the ship is found and eliminated.

I also recommend reading articles about low insulation 440V:

  1. Abnormal Fire. The boiler does not start. Troubleshooting
  2. The autotransformer was flooded with sea water. Emergency fire pump problem
  3. Motor Fault on the crane. Troubleshooting
  4. Problems with cargo cranes. Some problems with cargo cranes that occur on the ship

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