Impact of lightning or electrostatic charge

Whether it be a direct hit or near strike, the likelihood is that all electronics on board a vessel will have some measure of damage caused by a direct lightning strike or close proximity to a significant Electrostatic discharge.

Given the nature of an integrated system onboard of electrics and electronics it is impossible to predict what route the static discharge will take as is goes to ground and it also depends whether the boat or boatbuilder or installer made any precautions to try to protect against such an event.  

The damage to equipment, cabling and ancillaries can be immediate and components are blown up instantly or damage can be partial and the components will fail at an indeterminate period thereafter.  It is also likely the majority of other electrical equipment onboard will either be damaged or partially affected and will prematurely fail at some future point in time.

The Electrostatic discharge will cause random damage to PCBs and especially will destroy ICs and flat pack devices, as well as arc across copper tracks completely or partially severing them.

There is limited protection which can be provided to electronics to protect against static damage, simply due to the massive energy levels involved, however, installations can be given limited protection, simply by bonding all rigging to deck fittings and to an independent grounding plate using appropriate sizes of copper strapping will offer a reasonable level of protection.

The provision of lightning protection should be considered if the craft is intended for use in an area where there is likely to be a high incidence of electrical storms, for example inland lakes, Caribbean, North East Asia are all areas of significant Electrostatic activity.

There is a standard ISO 10134 : 1993 for lightning protection on small craft.

GENERAL PRINCIPLES

Lightning protection is the provision of a direct low resistance path from the masthead to a ground plate on the craft. It should be noted that lightning tends to take the shortest path. The connection from each mast or air terminal should be in a straight direct path vertically down to low level then horizontally direct to the ground plate on the hull or to a metal keel.

Usually the mast, rigging, stanchions and toe rail are all bonded together and are grounded to the sea through a grounding plate, this offers a good degree of protection, but again, depending on the size of discharge may still not offer a complete solution

ZONE PROTECTION

The zone of protection is equivalent to a cone, its point coincident with the top of the mast and the cone having a radius round the craft equal to the height of the mast and centred on the mast base – for example this can be formed by the effective bonding together of mast, shrouds and other standing rigging.

GROUNDING CONDUCTOR/WIRE CONDUCTOR

To provide an adequate lightning grounding conductor the entire circuit from the top of the mast or air terminal shall have a mechanical strength and conductivity not less than that of an 8 mm2 copper wire conductor., this can also be in the form of flat copper tape or strip of a similar cross section area.

LIGHTNING GROUND CONNECTION/PLATE

Any metal surface which is submerged in the water in any condition of heel or trim and the wetted surface area of which has an area of least 0.1m2.

Metallic radio ground plates or dynaplates may be used for the lightning ground connection.

NOTES:

i) Complete protection from equipment damage or personal injury may not be achieved and is not implied.

ii) Craft with metal hulls, if there is electrical continuity between the hull and the mast or other metallic superstructure of adequate height, no further protection against lightning is necessary.

iii) If a craft has been stuck by lightning, the compass, electronic and electrical gear should be checked for damage or change in calibration.

It is the customer’s/ boat builder’s responsibility to ensure the equipment onboard is correctly and effectively bonded and grounded and adequate lightning protection is provided

Our recommendation to customers is to completely replace all electronics that are in the affected circuit – replace cabling and switch gear since they may also have been damaged or burned as well as replacing any associated ancillary equipment which may also have been affected.

 

Mid Winter Checks

 

Tis the season to be jolly – tis also the season where general maintenance is most important as visits the boat are less frequent and the weather is cold and wet.

Here are some tips for what to check:

  • Replace any cables or junction boxes that show any signs of wear, damage or overload

 

    • Carefully check all electrical connections to ensure they are tight and secure against vibration, check fuses and fuse holders to ensure fuses are secure and making good contact with the cables and fuse holder.

 

  • Winter is a good time to asses all circuits on board, has additional equipment been added which may now overload the original fuse or cable? If in doubt, get the local qualified engineer to check and either redistribute load or install correct cabling and fusing to safely support and protect the electrical load.
  • If the mast is being un-stepped, remove mast head unit and store safely. Protect MHU plugs at mast head to prevent water ingress. Label and bag the loose cable at the base of mast to prevent water damage.

 

    • Check the VHF antenna and cable/plugs/connections.  If poor, remake.  If the antenna is 7-10 years old consider replacing them.  It’s easier to pull the new cable through the mast and fit the antenna when the mast is in the mast rack.  If in doubt, ask a dealer to check SWR reading. (Ideally before mast is un-stepped).

 

  • Check all electronic/electrical items that may need service and don’t leave it to the day you relaunch your vessel to contact your local dealer or supplier for service.
  • Consider electronic chart card updates for the next season.  Contact your supplier or manufacturer and do not leave to the last minute.
  • Go online and check for manufacturers sw updates.  There could be enhancements or new features at no extra costs.

 

 

When all this is done, go home and have a well deserved drink in the front of the fire to warm up.

 

From everyone at the BMEEA, we wish you the merriest of Christmases.

Season’s Greetings!

Winterising your boat’s Electrics and Electronics

With winter upon us we have some tips to help prepare your boat for the months ahead:

  • Where possible, remove batteries and keep them warm and dry over the winter – if you are unable to do this, ask your local approved and qualified marine electrician to do this, ( for a list of BMEEA members able to assist please visit the member locator)
  • Keep batteries fully charged or topped up at least every couple of months. Batteries left uncharged for long periods may need to be replaced completely. If you’re unable to remove batteries or if the boat is staying on its mooring, leave them fully topped up and regularly recharged, as full batteries are less likely to freeze in sub-zero temperatures.
  • Damp is the enemy of every electrical and electronic system, ensure the boat is well ventilated or installed with a dehumidifier.
  • Equipment left unused for extended periods of time can become erratic in operation due to damp affecting switch contacts, internal circuit boards, signal processors or even computer chips, so regular power up checks and operation during extended idle periods can help maintain correct operation
  • Switch contacts can accumulate Verdigris over extended idle periods and this can create high resistance connections or even complete isolation of switch contacts. Regular operation of the switches can slow down the deterioration of switch contact surfaces.
  • Do not spray the switch gear with corrosion inhibitors, this can leave a residue which effectively isolates the contact surfaces and creates a malfunctioning switch.
  • Carefully check all cables and Junction boxes to ensure the cable insulation is not damaged, cables are secured to bulkheads and not showing any signs of chafing, ensure all junction boxes are securely mounted and correctly sealed and no cables or junction boxes are mounted such that they remain submerged for extended periods of time.

If you have any other tips or questions, please let us know!