Greetings! In this article we will analyze the first actions of the ETO when low 220V insulation occurs on a ship. How to find the source of low insulation and what steps to do in such situation.
On a vessel it is very important to pay special attention to this, because by promptly eliminating low insulation, you can prevent dangerous smoke or even fire.
As often happens, the “Low insulation 220V” alarm goes out to the alarm monitoring system in the ECR and the ETO has to look for the source of low insulation on the ship.
The way to find low insulation is to turn off the circuit breakers on the 220V feeder panel of the main switchboard one by one and at the same time monitor the megohmmeter needle.
The megohmmeter shows how the insulation resistance of the ship's electrical network changes in real time, so if you turn off the desired circuit breaker (de-energize a group of consumers with low insulation), its needle should instantly point towards infinity.
The alarm setting for the ground monitor is 0.01 MOhm. What should the value be? I'm waiting for your answer in the comments.
The first action of an electrician when searching for low insulation is to turn off the desired circuit breaker and narrow the search. Non-essential consumers are turned off first, these could be outlets or lights on the deck, galley, washing machines and dryers.
- The first circuit breaker that I turn off is the lighting and sockets for the forecastle.
- The second circuit breaker is the galley and laundry.
- The third breaker is for lighting and power outlets on the main deck and aft part.
- Next, I turn off the navigation lights, lighting and engine room outlets section by section.
- If none of the above helps, then you have to turn off the cabins. At the same time, it is necessary to make an announcement so that the crew turn off their computers and phones from the sockets.
- If this is not the problem, then you need to turn off systems and devices that use 220V. For example, fire alarm system, water ingress alarm system, public address system, shaft power meter, etc.
If all the circuit breakers are turned off, but the insulation is still low, then you need to inspect the main service transformer, but it rarely comes to that.
After the main circuit breaker has been found, it is necessary to take a portable megger and inspect the secant circuit breakers of this group. Each phase must be measured relative to the ground (hull) (be sure to remove power from the phase).
Next we go to the source of low insulation directly. Below are the most common problems with low insulation on a ship.
All of the above cases of poor insulation on a ship are only a small part of the reasons why the low insulation 220V alarm occurs. An electrical engineer's job is to find and fix these problems.
Let's consider a real situation when low insulation 220V came out. When switching off the circuit breakers, the breaker of the 4th group with low insulation was found.
Using a portable megger, we found the 9th circuit breaker in the 4th distribution board with low insulation.
From the diagram we see that this circuit breaker has many different sockets.
As a result of testing all sockets one by one, an socket with low insulation was found in the SUEZ CREW room.
Despite the fact that this was a room, the outlet was located practically on the open deck (with access to the starboard side of the main deck) and experienced maximum loads from the aggressive marine environment. After replacing the socket, the 220V insulation was restored to normal.
It is very important to know the operating conditions of the vessel and understand what is currently turned on and what could lead to low insulation.
For example, the ship is in maneuveringmode and is passing through a narrow channel; the Steering Light on the bow mast is turned on. The ship is passing through the Suez Canal and has turned on the Suez lights or anti-fog projector light on the forecastle. The ship approaches Singapore and the special three green lights on the masthead are turned on. This may result in poor insulation of these lights. All these and other examples indicate that something is always turned on and off on a ship, and it is important to understand what exactly and when.
To check such lights or outdoor lighting, you need to check the phases on the contactors that are activated when the lights are turned on.
Typically, the activation of exterior lighting, navigation and special lights occurs on the bridge.
For example, we pressed the "ACC. OUTSIDE PASSAGE LIGHT (UPPER DECK)" button, the MC2 contactor in the distribution panel of the 4th group of breakers was activated and the external lighting on the main deck turned on.
So in this case we must check the circuit to the ground after the contactor.
If we measure the phase resistance to the ground after the breaker, then only the circuit “contactor - breaker” will be checked.
Finally, we’ll do an Earth Test to make sure that the megohmmeter is working properly and that none of the phases are “sitting” on the ground.
Low insulation in a 220V electrical system on ships can lead to significant safety hazards and operational issues, similar to those in higher voltage systems. Proper detection, maintenance, and mitigation are essential to prevent these problems. Here's a comprehensive overview of low insulation in a 220V system on a vessel, including implications, causes, detection methods, and mitigation strategies.
Implications of Low Insulation
1. Electrical Safety Hazards:
- Electric Shocks: Increased risk of electric shocks to crew members.
- Fire Risk: Potential for electrical fires due to arcing or short circuits.
2. Equipment Damage:
- Short Circuits: Can cause damage or failure of electrical equipment.
- Operational Downtime: Equipment failure can disrupt critical operations on the vessel.
3. Regulatory Non-Compliance:
Common Causes of Low Insulation
- Safety Standards: Failure to meet maritime safety regulations and standards.
1. Environmental Factors:
- Moisture and Humidity: Water ingress and high humidity can degrade electrical insulation.
- Saltwater Exposure: Corrosive effects of saltwater can deteriorate insulation materials.
2. Aging and Wear:
- Material Degradation: Insulation materials can break down over time.
- Mechanical Damage: Physical damage from vibrations, impacts, or abrasions.
3. Improper Installation or Maintenance:
- Faulty Installation: Poor installation practices can compromise insulation integrity.
- Lack of Maintenance: Neglecting regular maintenance can lead to unnoticed deterioration.
Detection of Low Insulation
1. Insulation Resistance Testing:
- Megger Testing: An insulation resistance tester (megger) measures the resistance of the insulation. Low resistance readings indicate potential problems.
2. Thermographic Surveys:
- Infrared Cameras: Detecting hotspots that indicate areas of insulation failure.
3. Visual Inspections:
- Routine Checks: Regular visual inspections of cables and electrical components for signs of wear, damage, or corrosion.
4. Monitoring Systems:
- Continuous Monitoring: Systems that continuously monitor insulation resistance and alert crew to potential issues.
Mitigation and Maintenance
1. Regular Maintenance:
- Scheduled Inspections: Regular inspections and testing to detect insulation issues early.
- Cleaning and Drying: Keeping electrical components clean and dry to prevent moisture-related insulation degradation.
2. Immediate Repairs:
- Prompt Action: Repairing or replacing damaged insulation and cables as soon as issues are detected.
3. Environmental Control:
- Humidity Control: Using dehumidifiers and ensuring proper ventilation to control humidity levels in electrical compartments.
- Waterproofing: Ensuring all electrical enclosures are properly sealed against water ingress.
4. Training and Awareness:
- Crew Training: Ensuring crew members are trained to recognize signs of insulation failure and understand the importance of regular maintenance.
Low insulation in a 220V electrical system on a vessel can lead to serious safety and operational risks. It is essential to promptly detect and address these issues through regular maintenance, proper environmental controls, and immediate repairs. Implementing robust inspection and monitoring practices will help maintain the integrity of electrical systems, ensuring both safety and operational efficiency on the vessel.
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