- A ship always has hazards around her while she sails across the sea.
- Most of these dangers belong to the troubling waters and the weather conditions outside.
- Heavy weather overhead and lightning are a big part of these elements too.
- Hence, it is critical to understand how ships are protected from Lightning incidents.
A recent news article published in the Marine Insight interprets How Ships are Protected from Lightning – Ships Earthing System.
Many risks originate from such incidents
Many risks originate from such incidents of the loose electrical outbreak of any nature. However, lightning is not the only electrical hazard present for ships to deal with. Many short circuit incidents prove to be life-taking for seagoing vessels every year.
More than 1,200 electrical accidents and incidents of major and minor nature occur every year. Under such conditions, the ships earthing systems installations become essential for every size of the vessel. Such systems protect the internal electrical hazards and also any external electrical risks too.
The article explains how modern-day ships exhibit their ability to deal with Lightning incidents. It also includes their earthing design and how the neutral system works onboard. We also identify the probable risks if such incidents or the current breaks happen too often.
Ships Earthing System Working
The purpose of an Earthing connection on the electrical systems is to handle the flow of leaking current. Any waste charge flows through these connections, saving the equipment and the lines. It resolves the possible hazards that come from such an outbreak.
A current break or leak can occur from different sources, a few of which include:
- A glitch or cut in the wire or transmission lines leading to the electrical leaks
- A piece of faulty equipment such as broken motor winding
- A fault in the circuit breakers or the electrical panel leading to a major current surge
Nature of Ship Earthing Design
Cargo and Passenger ships earthing systems are insulated neutral, in contrast to the land designs of earthing neutral. It means that the neutral does not have direct tapping to the earth and has an insulating nature.
Hence, there is no direct pathway for the leaking current to flow to the earth. Despite this, ships adopt the insulated neutral design because of their critical operations.
On the land, a single earth fault of severe kind can cause the equipment to trip. It happens because the earthing connection allows a simple route for the current to flow, leading to a surge.
However, ships do not want their essential machinery to stop working under critical situations. Such lapses will lead to loss of propulsion, electrical power supply, or other incidents. These faults lead to navigation accidents and loss of cargo operations under serious situations.
Steering gear, navigation radar, fire pumps, and engine controls are highly critical equipment. Hence, the insulated neutral allows the machinery to work with one fault across the line.
Earth Fault Monitoring
A trip will happen when there is another earth fault across the other line, leading to interference. The two separate faults across phases cause the current flow to interfere in a hazardous manner.
Moreover, the higher number of machinery within a ship gives rise to more possibilities of earth faults. However, a short circuit is critical and does not usually occur because of the monitoring systems.
The monitoring system indicates the magnitude of the earth-fault for an initial idea. It helps the engineers on board to detect and isolate the faulty line and the equipment.
While the zones or equipment are not detectable, the step-wise fault-finding allows corrections. The indicating needle moves between 0 to infinity, depending on the occurrence of the fault. Hence, the earth fault correction and repairs take place to prevent any accidental trip.
Possible Risks
In the event of breakages within ships earthing systems, many risks loom large. The most severe situations coming from the possible earth fault and trips will be:
Fire Hazards
These can be from the possible sparks that result from the wires or the loose connections. Moreover, the overheating of systems before the equipment trip can result in fires too.
Fires are the scariest of shipboard risks due to their engulfing nature. The critical elements onboard do not have any other means of substitution. Once these systems catch fire, the total loss of ship control and accident becomes inevitable.
Short Circuit
The short circuit originating from these faults is a risk to the equipment. Under changing conditions, the short-circuit can lead to complete breakdown and failure too.
While there is protecting equipment in the line, a saving action does not guarantee from them. The rapid surges can also lead to overload trips or blackouts which becomes a threat to stability.
Life Threat
A fault in the earthing system creates a live nature of the current passage. It means any contact with the naked limb will give an easy way for current.
The current creates a shock leading to cardiac arrest or permanent damage to the body part. Almost 1400 incidents of varying nature of electrical shocks occur on ships every year.
Lightning Protection of Ships
To understand how ships are protected from lightning, the probable effects are equally important. It includes the understanding of the nature of lightning bolts and how they disturb the vessels. Moreover, the possible outcome of these lightning strikes and their hazards are equally important.
Lightning at Sea
The lightning and thunder at sea need a path of movement like on land. During storms, the clouds have a changing polarization within themselves. It leads to the separation of charges, with the electrons at the bottom half.
These negative charges are ready to combine with the positive polarity of the land surface. Hence, a lightning bolt comes out as a way of dissipation of this energy into the Earth.
These thunderbolts look for an easy way out at sea for the flow of this charge too. It means any conducting surface present above the water will provide lighting with an easy way out.
Ships as Conductors
Since current seeks the best and shortest route to ground, the conductors come into play. The nature of the charges to find the best way amplifies in the presence of such bodies. Hence, the floating ships with an all-metal design become the perfect conductor.
Moreover, the height of the ship along with the mast is several meters over the water surface. Hence, this path presents a better trajectory for the lightning instead of the air passage. In such conditions, the absence of preventing equipment positions vessels as an ideal conductor of lightning.
Damages From Lightning
If ships do not have a protective system for lightning, there will be severe results. The damages do not happen to machinery or equipment but to the people on board too.
Sensitive Systems
Navigation equipment and communication systems onboard ships operate at relatively low voltages. It means any surge in the power supply can severely damage them or make them useless. Moreover, errors in the signal can originate from such interference too.
Lightning strikes of any magnitude will result in voltage surges at these terminals. It will spoil the equipment or create short circuits, causing risk to navigation safety.
The radar mast, radio antenna, and GPS positioner also fall in the line of action. These instruments have maximum exposure to lightning and are at most risk.
Human Life
The systems leading to how ships are protected from lightning have a high focus on human lives. Any electrical shocks act as a life-ending impact on the human body. Hence, lightning needs to dissipate into the surroundings before it contacts the people onboard.
It includes any small residual current from the lightning in the hull. Moreover, it can also cause damage to the vulnerable property available on the ship.
Fire
The sheer impact of a lightning strike causes enough charge movement in a definite time. It creates a volatile environment, leading to fires on board in the region of the impact. Such fires are uncontrollable out at sea when the equipment is out of service after the strike.
Lightning Protection Equipment Requirements
The lightning protection system onboard a vessel contains multiple layers of protection equipment. These elements play different roles in the overall safety protection of a ship against lightning.
Direct Strike Protection
The damages and impact of a direct lightning strike are the sources of lightning hazards. Hence, the protection system needs to mitigate the bolts while contacting the ship’s surface. Moreover, the system needs to move the lightning at one point instead to protect the other areas too.
Surge Protection
A surge in the voltage causes critical components of the vessel operation system to go ineffective. Hence, the lightning protection setup needs to account for surge protection with the bonding arrangement. It also includes the diversion of the lightning strikes to a safe zone onboard for further handling.
Flashing Safety
The side risk of a lightning incident onboard is the arc flashes on the systems. These will instantly lead to fires or blasts in the nearby area, causing fatalities and losses. Hence, direct bonding arrangements for all the equipment to a common point becomes essential.
Life Protection
The dissipation of lightning into the hull will impact the people on board with immediate shock. These shocks will range up to several thousand volts, immediately killing everything in sight. Hence, proper grounding arrangement for all the accommodation and other spaces takes care of this hazard.
Lighting Protection Installation
The lightning protection installation systems are the best explanation of how ships are protected from lightning. The installation starts at the top of the monkey island from the radar mast, progressing towards the hull. The critical elements handle lightning from the time of contact up to its final mitigation.
Air Terminal Installation
The air terminal at the mast will be a single rising element with additional electrodes as a cluster. The element gathers the lightning and directs it towards a safe zone for grounding into the electrodes. The voltage rating of these terminals goes up to 500-750 kV for modern systems.
While the main body is of steel, the inside consists of a series of resistors to lower the intensity. The outer shielding consists of a fibreglass rod that shields the inner elements. These are secured onto the mast base with the help of U-bolts and a rubber clamp for security.
The air terminal further connects to the bonding cable that carries the lightning safely into the water. The crucial components of this unit summarize into:
- Upper termination Unit
- U-clamps
- Fiberglass rod
- Lower Termination Unit
- Bonding Conductor
Bonding Cable
The bonding or the shielding cable connects the air terminal to immersing clamp that acts as ground screws. The high voltage cable contains multiple layers of sheathing and a rating of 1.25 times the air terminal. It ensures the safe handling of any transient surges for safely dissipating them in the water.
Surge Suppression Unit
The Surge suppression unit contains individual breakers and fuses, and the interconnection to a surging box. These contain single-phase and 3-phase power supply protection kits of different ratings. A common example is that of the trademark 3DR100KA-385-NE100 surge protection setup.
The surge protection box also has connections from several critical elements. These wires are of the equivalent rating for the shielding cable. The cables further connect the box to the single bonding point for the grounding of the lightning into the water.
Bonding and Earth Discharge Connection
The bonding and earthing arrangements vary as per the size and nature of the vessel. An oil tanker bonding screw at the hull is different from that of a bulk carrier. A simple silicon or bronze screw electrode has a higher rate of reduction in comparison to other designs.
These bonding connections are the final point of contact where the lightning safely dissipates into the water. Hence, the safe passage of lightning finally ends with grounding into the sea.
Ship Earthing and Lightning Protection
Ships earthing systems design and the lightning protection system play critical roles in safety. Catastrophic incidents of marine pollution, ship sinking, and loss of life are avoidable with these installations.
Each vessel has a particular choice of installations, with variations in the makers too. However, the basics of lightning handling through a safe passage and finally into the water remains constant.
With the increasing sensitivity of equipment and the importance of human life, lightning protection is always critical. All these arrangements in place lead to a safer and more efficient shipping operation future.
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Source: Marine Insight
