Re: [PSES] Ground on ship

[Ted Eckert]

I agree with Mr. Woodgate.

The issue is whether there is a risk of a voltage between the conductive 
enclosure of a device and exposed conductive materials in the environment. The 
“ground” system only needs to ensure that there won’t be a voltage difference 
between a device’s exposed parts and anything the user can touch in the 
environment. If the metal structure of the ship is used as the “ground” and the 
ground pin of outlets is connected to the metal structure of the ship, and the 
ship’s generator uses the metal structure as a grounding reference, the system 
should function similarly to the grounding system of a properly wired structure 
on solid land.

Ted Eckert
Microsoft Corporation

The opinions experessed are my own and do not necessarily reflect those of my 
employer.

From: John Woodgate 
Sent: Monday, July 8, 2019 11:39 AM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] Ground on ship


'Ground' only means 'the places which we agree have zero volts on them', 
nothing more. So wherever that is, on a ship or an aircraft (or inside an 
appliance with a  2-core power cable), that is 'ground'.

Best wishes

John Woodgate OOO-Own Opinions Only

J M Woodgate and Associates 
www.woodjohn.uk

Rayleigh, Essex UK
On 2019-07-08 19:19, 
06cee064502d-dmarc-requ...@ieee.org
 wrote:
Hello group,

Is there a real ground in a ship?  i.e if a Class I product is used on the 
board of a ship, does the ground pin actually doing anything? The ship is 
floating in the ocean and I cannot understand if there is a real ground there 
or not? Can you guys educate me please?

Thank you
Peter
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Re: [PSES] Ground on ship

[Ken Javor]

On US military surface ships, power is ungrounded.  Green wires do connect
to structure, so in the case of a fault the equipment enclosure is at ground
potential, but it isn¹t going to trigger a protection device that way.

The whole discussion about sea water conductivity is moot.  You could ask
the same question about an airplane: it¹s ungrounded in flight; metal
structure works just fine as John Woodgate says.

Where sea water is useful is transmitting hf.  As Rich notes, the large
surface area of the ship¹s hull in contact with conductive sea water allows
the surface of the sea to act as an extended counterpoise for hf masts
operating against the ship as a counterpoise. At frequencies where the ship
is electrically short, sea water makes these masts much more efficient than
they would be if only the ship structure acted as counterpoise.

Ken Javor
Phone: (256) 650-5261



From: Richard Nute 
Reply-To: 
Date: Mon, 8 Jul 2019 12:48:24 -0700
To: 
Subject: Re: [PSES] Ground on ship

   
 Hi Peter:
 
 Sea water is a very good conductor, better than soil.  Fresh water is an
okay conductor.  Pure water is a poor conductor.
 
 The hull of a steel ship is well grounded in the ocean, and reasonably well
grounded in fresh water due to the large contact area with the water.
 
 If the hull is not steel, there usually are enough fittings that the ship
is reasonably well-connected to the water.  The propeller and drive shaft
also provide a connection to the water.
 
 I've heard of ship-board hams who will tow a large brass plate for a good
ground for their transmitter.
 
 Commercial AM transmitters try to locate their antennas near a body of salt
water like San Francisco Bay or the Great Salt Lake.
 
 I would guess that a ground pin of a shipboard outlet would be connected to
the hull metal.  This gives the same protection from electric shock as
land-based outlets.
 
 See also:
 
 http://electrotechnical-officer.com/primary-methods-of-grounding-and-bondin
g-on-ship/
 
 
 Best regards,
 Rich
 
 
On 7/8/2019 11:19 AM, 06cee064502d-dmarc-requ...@ieee.org wrote:
 
 
>   
>  
>  
>  
> Hello group,
>  
> 
>  
>  
> Is there a real ground in a ship?  i.e if a Class I product is used on the
> board of a ship, does the ground pin actually doing anything? The ship is
> floating in the ocean and I cannot understand if there is a real ground there
> or not? Can you guys educate me please?
>  
> 
>  
>  
> Thank you
>  
> Peter
>  
>  
>  
>  
>  
 
 -


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Re: [PSES] Ground on ship

[Gert Gremmen]

Ground is only called ground because it was usage to use the real ground 
as safety potential.


Why ? Because we humans historically  tend to connect with our feet to 
the soil, and  if any touchable conductor has the same potential


as the soil, there is no hazard. This works only in reasonably wet areas.

Grounding Safety is about the voltage_difference_ we can reach as humans 
using hand and legs to bridge distances.


In the northern countries, and in the mountains the soil is mainly rock, 
and does not conduct electricity well enough


to function as a safety "ground" (actually "safety rock"). The utility 
their relies on other mechanisms for safety then soil ground.


The soil is connected to the surface of our globe. If we could reach the 
moon with our hand, there would probably


a huge discharge current between the two bodies, because the moon is not 
grounded.


Ground is relative. Inside a metallic volume, ground has no meaning 
anymore, because you need to touch


the metal wall before you can touch ground. Inside such a volume the 
'ground" is the metal wall.


All conductive items need to be connected to the volume (=ship) wall to 
remain safe.


It makes no sense seeking for our globes soil potential (ground) inside 
a metallic volume.


Gert Gremmen








On 8-7-2019 20:19, 06cee064502d-dmarc-requ...@ieee.org wrote:

Hello group,

Is there a real ground in a ship?  i.e if a Class I product is used on 
the board of a ship, does the ground pin actually doing anything? The 
ship is floating in the ocean and I cannot understand if there is a 
real ground there or not? Can you guys educate me please?


Thank you
Peter
-


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--
Independent Expert on CE marking
Harmonised Standards (HAS-) Consultant @ European Commission for RED and EMC
EMC Consultant
Electrical Safety Consultant


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<>

Re: [PSES] Ground on ship

[Doug Powell]

In actuality the ship's hull is not that well connected to the water. There
are a number of issues such as the paint used on the hull to prevent
corrosion in salt water and the fact that the ship's screws are generally
made of brass and galvanic corrosion is a problem. Which is why US Navy
ships have large sacrificial anode of lead on the bottom of the hull. Ships
can also become magnetized and often must pass through a degaussing range
on return to port. As for RF ground with respect to sea water, one might
argue that the paint is so thin that is the effective capacitance negates
any insulating value at frequency. However naval radio and radar systems
are very high powered and I don't believe they rely on that alone.

Best, Doug



On Mon, Jul 8, 2019 at 1:48 PM Richard Nute  wrote:

>
> Hi Peter:
>
> Sea water is a very good conductor, better than soil.  Fresh water is an
> okay conductor.  Pure water is a poor conductor.
>
> The hull of a steel ship is well grounded in the ocean, and reasonably
> well grounded in fresh water due to the large contact area with the water.
>
> If the hull is not steel, there usually are enough fittings that the ship
> is reasonably well-connected to the water.  The propeller and drive shaft
> also provide a connection to the water.
>
> I've heard of ship-board hams who will tow a large brass plate for a good
> ground for their transmitter.
>
> Commercial AM transmitters try to locate their antennas near a body of
> salt water like San Francisco Bay or the Great Salt Lake.
>
> I would guess that a ground pin of a shipboard outlet would be connected
> to the hull metal.  This gives the same protection from electric shock as
> land-based outlets.
>
> See also:
>
>
> http://electrotechnical-officer.com/primary-methods-of-grounding-and-bonding-on-ship/
>
>
> Best regards,
> Rich
>
> On 7/8/2019 11:19 AM, 06cee064502d-dmarc-requ...@ieee.org wrote:
>
> Hello group,
>
> Is there a real ground in a ship?  i.e if a Class I product is used on the
> board of a ship, does the ground pin actually doing anything? The ship is
> floating in the ocean and I cannot understand if there is a real ground
> there or not? Can you guys educate me please?
>
> Thank you
> Peter
>
>
> -
> 
>
> This message is from the IEEE Product Safety Engineering Society emc-pstc
> discussion list. To post a message to the list, send your e-mail to <
> emc-p...@ieee.org>
>
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> http://www.ieee-pses.org/emc-pstc.html
>
> Attachments are not permitted but the IEEE PSES Online Communities site at
> http://product-compliance.oc.ieee.org/ can be used for graphics (in
> well-used formats), large files, etc.
>
> Website: http://www.ieee-pses.org/
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-- 

Douglas E Powell

doug...@gmail.com
http://www.linkedin.com/in/dougp01

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Re: [PSES] Ground on ship

[John Woodgate]

Hi, Rich. All what you say is true. Now extend it to a fibreglass rowing 
boat! The connection of the hull with sea water is of no significance at 
all, as I'm sure you know. The pernicious idea that you can dump 
unwanted electricity into the planet, dry(ish) or wet, is responsible 
for more EMC failures than you can shake a mainmast at!


This confusion stems from radio transmission at low radio-frequencies. 
At VHF and above, the transmitter's output is connected to the two arms 
of a dipole (or other mechanical device that has effectively the same 
electrical function). At lower frequencies, such a structure would be 
too big, so one arm is simulated by an array of wires buried in the 
earth. This acts as a mirror, so eliminating the problem of sinking a 
300 foot mast into bedrock.  There must be a continuous circuit, 
otherwise no current could flow from the transmitter. The fact that we 
can't see the energy flowing out as an electromagnetic wave is just due 
to our limited visual bandwidth (just one octave out of at least 21 
octaves in the electromagnetic spectrum).


The same thing applies at the receiver; for VHF and above we hoist a 
dipole (maybe with extra elements to make a Yagi), which has two 
conductors leading from it, but at lower frequencies we have to put up a 
long wire antenna, connected to one side of the receiver input circuit 
and connect the other end of the receiver input circuit to a buried 
metal rod, thus setting up the continuous circuit.  This has nothing to 
do with some concept of a 'ground', with mysterious powers to absorb 
however much unwanted electrical energy we throw at it.


Ground is whatever you decide has zero volts on it, so all other 
voltages are measured with respect to it. In a digital wristwatch, it's 
about a square millimetre of PCB foil.



Best wishes
John Woodgate OOO-Own Opinions Only
J M Woodgate and Associates www.woodjohn.uk
Rayleigh, Essex UK

On 2019-07-08 20:48, Richard Nute wrote:


Hi Peter:

Sea water is a very good conductor, better than soil.  Fresh water is 
an okay conductor.  Pure water is a poor conductor.


The hull of a steel ship is well grounded in the ocean, and reasonably 
well grounded in fresh water due to the large contact area with the 
water.


If the hull is not steel, there usually are enough fittings that the 
ship is reasonably well-connected to the water.  The propeller and 
drive shaft also provide a connection to the water.


I've heard of ship-board hams who will tow a large brass plate for a 
good ground for their transmitter.


Commercial AM transmitters try to locate their antennas near a body of 
salt water like San Francisco Bay or the Great Salt Lake.


I would guess that a ground pin of a shipboard outlet would be 
connected to the hull metal.  This gives the same protection from 
electric shock as land-based outlets.


See also:

http://electrotechnical-officer.com/primary-methods-of-grounding-and-bonding-on-ship/


Best regards,
Rich

On 7/8/2019 11:19 AM, 06cee064502d-dmarc-requ...@ieee.org wrote:

Hello group,

Is there a real ground in a ship?  i.e if a Class I product is used 
on the board of a ship, does the ground pin actually doing anything? 
The ship is floating in the ocean and I cannot understand if there is 
a real ground there or not? Can you guys educate me please?


Thank you
Peter



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Re: [PSES] Ground on ship

[IBM Ken]

Ultimately if the on-board AC power generation is connected to the metal
structure of the ship, then I'd think it is the same as on land, except the
ship hull superstructure is the 'ground'.

In fact, you might have a 'better' ground on a ship since the metal
structure of the ship is exposed in more situations ('ground' is all around
on a ship, as compared to the paths to earth ground on land; cold water
pipes, ground rods, green/yellow wires, conduit, RF grounds, etc), so
there's more opportunities for a fault to 'ground out' and trip an upstream
overcurrent protection device.

I'm thinking mostly of large military ships - if you're talking about
fiberglass (or wooden!) pleasure craft then the story is less clear, but I
believe they often have a common grounding point too; it's just much
smaller.


-Ken A

On Mon, Jul 8, 2019 at 2:19 PM <06cee064502d-dmarc-requ...@ieee.org>
wrote:

> Hello group,
>
> Is there a real ground in a ship?  i.e if a Class I product is used on the
> board of a ship, does the ground pin actually doing anything? The ship is
> floating in the ocean and I cannot understand if there is a real ground
> there or not? Can you guys educate me please?
>
> Thank you
> Peter
> -
> 
>
> This message is from the IEEE Product Safety Engineering Society emc-pstc
> discussion list. To post a message to the list, send your e-mail to <
> emc-p...@ieee.org>
>
> All emc-pstc postings are archived and searchable on the web at:
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>
> Attachments are not permitted but the IEEE PSES Online Communities site at
> http://product-compliance.oc.ieee.org/ can be used for graphics (in
> well-used formats), large files, etc.
>
> Website: http://www.ieee-pses.org/
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Re: [PSES] Ground on ship

[ebj]

Good resources are MIL-STD-1310H and MIL-STD-1399-300B, I believe... Elyaנשלח 
מסמארטפון ה-Samsung Galaxy שלי.
 הודעה מקורית מאת: Richard Nute  תאריך: 
8.7.2019  15:48  (GMT-05:00) אל: EMC-PSTC@LISTSERV.IEEE.ORG נושא: Re: [PSES] 
Ground on ship 

Hi Peter:
  
  Sea water is a very good conductor, better than soil.  Fresh water
  is an okay conductor.  Pure water is a poor conductor.
  
  The hull of a steel ship is well grounded in the ocean, and
  reasonably well grounded in fresh water due to the large contact
  area with the water. 
  
  If the hull is not steel, there usually are enough fittings that
  the ship is reasonably well-connected to the water.  The propeller
  and drive shaft also provide a connection to the water.
  
  I've heard of ship-board hams who will tow a large brass plate for
  a good ground for their transmitter.
  
  Commercial AM transmitters try to locate their antennas near a
  body of salt water like San Francisco Bay or the Great Salt Lake.
  
  I would guess that a ground pin of a shipboard outlet would be
  connected to the hull metal.  This gives the same protection from
  electric shock as land-based outlets.
  
  See also:


http://electrotechnical-officer.com/primary-methods-of-grounding-and-bonding-on-ship/
  
  
  Best regards,
  Rich

On 7/8/2019 11:19 AM,
  06cee064502d-dmarc-requ...@ieee.org wrote:


  
  

  
Hello group,


Is there a real ground in a ship?  i.e if a Class I
  product is used on the board of a ship, does the ground
  pin actually doing anything? The ship is floating in the
  ocean and I cannot understand if there is a real ground
  there or not? Can you guys educate me please?


Thank you
Peter
  

#yiv5252605836 #yiv5252605836 --_filtered #yiv5252605836 
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Re: [PSES] Ground on ship

[Richard Nute]

Hi Peter:

Sea water is a very good conductor, better than soil.  Fresh water is an 
okay conductor.  Pure water is a poor conductor.


The hull of a steel ship is well grounded in the ocean, and reasonably 
well grounded in fresh water due to the large contact area with the water.


If the hull is not steel, there usually are enough fittings that the 
ship is reasonably well-connected to the water.  The propeller and drive 
shaft also provide a connection to the water.


I've heard of ship-board hams who will tow a large brass plate for a 
good ground for their transmitter.


Commercial AM transmitters try to locate their antennas near a body of 
salt water like San Francisco Bay or the Great Salt Lake.


I would guess that a ground pin of a shipboard outlet would be connected 
to the hull metal.  This gives the same protection from electric shock 
as land-based outlets.


See also:

http://electrotechnical-officer.com/primary-methods-of-grounding-and-bonding-on-ship/


Best regards,
Rich

On 7/8/2019 11:19 AM, 06cee064502d-dmarc-requ...@ieee.org wrote:

Hello group,

Is there a real ground in a ship?  i.e if a Class I product is used on 
the board of a ship, does the ground pin actually doing anything? The 
ship is floating in the ocean and I cannot understand if there is a 
real ground there or not? Can you guys educate me please?


Thank you
Peter




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Re: [PSES] Ground on ship

[John Woodgate]

'Ground' only means 'the places which we agree have zero volts on them', 
nothing more. So wherever that is, on a ship or an aircraft (or inside 
an appliance with a  2-core power cable), that is 'ground'.


Best wishes
John Woodgate OOO-Own Opinions Only
J M Woodgate and Associates www.woodjohn.uk
Rayleigh, Essex UK

On 2019-07-08 19:19, 06cee064502d-dmarc-requ...@ieee.org wrote:

Hello group,

Is there a real ground in a ship?  i.e if a Class I product is used on 
the board of a ship, does the ground pin actually doing anything? The 
ship is floating in the ocean and I cannot understand if there is a 
real ground there or not? Can you guys educate me please?


Thank you
Peter
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[PSES] Looking for South American Product Safety Consultants

[Doug Nix]

Colleagues,

I have a client who is in need of some assistance with South American product 
safety requirements. If you are one, or if you know of someone reputable that I 
could refer my client to, please get in touch.

The sector is industrial machinery, including laser etching/marking, x-ray NDT, 
robotics and related equipment. 

Doug Nix
d...@ieee.org
+1 (519) 729-5704


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[PSES] Ground on ship

[000006cee064502d-dmarc-request]

Hello group,
Is there a real ground in a ship?  i.e if a Class I product is used on the 
board of a ship, does the ground pin actually doing anything? The ship is 
floating in the ocean and I cannot understand if there is a real ground there 
or not? Can you guys educate me please?
Thank youPeter#yiv5252605836 #yiv5252605836 -- _filtered #yiv5252605836 
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[PSES] Senior Compliance Engineer: Job Opportunity

[Kapur, Ken]

Job Opening at Thermo Fisher Scientific for Safety/ Compliance based in 
Sunnyvale, CA, Check the following link for more info:

Senior Compliance Engineer
https://jobs.thermofisher.com/ShowJob/Id/677321/Senior-Compliance-Engineer/


The Senior Compliance Engineer will provide guidance regarding product safety 
and product compliance requirements. This role is responsible for evaluating 
products to ensure they will meet applicable regulations including EMI/EMC, low 
voltage directive, product safety standards, and will be a key contributor to 
R&D during the development process for design to compliance.




Best Regards,
Ken Kapur
Director, Compliance
Thermo Fisher Scientific





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Re: [PSES] Fail analysis on a micro switch - who have this service?

[John Woodgate]

First, if you haven't already, consult the manufacturer. Maybe the 
contact material is not suitable for the voltage or the current in your 
application. Microswitches now rarely fail due to contamination.


Best wishes
John Woodgate OOO-Own Opinions Only
J M Woodgate and Associates www.woodjohn.uk
Rayleigh, Essex UK

On 2019-07-08 14:06, Amund Westin wrote:


A micro switch occasionally fails because it does not make contact 
during activation, and this is probably due to the contact surfaces 
being damaged or dust / debris on them.


Any suggestions on labs that may have this competence to do some work 
and analyze on such an issue?


Thanks!

Best regards

Amund

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[PSES] Fail analysis on a micro switch - who have this service?

[Amund Westin]

A micro switch occasionally fails because it does not make contact during
activation, and this is probably due to the contact surfaces being damaged
or dust / debris on them. 

Any suggestions on labs that may have this competence to do some work and
analyze on such an issue?

 

 

Thanks!

 

Best regards

Amund

 

 

 


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