One interrupted neutral I saw was between a power distribution transformer on a pole and a house weathercap. It was due to a squirrel chewing through the bare aluminum neutral wire in the service drop. Damaged some user equipment which the power company paid for. Squirrel did that 4 or 5 times before the power company replaced the drop with copper wire which squirrels don't use to sharpen their teeth.
Earthing systems are governed by national wiring regulations. TT is used in e.g. southern Europe, TN-S in northern Europe. Both have pros and cons and neither is better or safer than the other.
Nice subject!
I felt a distinct tingle when connecting my computer to my stereo system.
And a lot of noise and buzz when connecting.
All with 2-pin plugs.
So I made grounding connections to the gas tubes, the tingle was gone but replaced by hum on low sound volume.
So the grounding was removed again.
I felt a distinct tingle when connecting my computer to my stereo system.
And a lot of noise and buzz when connecting.
All with 2-pin plugs.
So I made grounding connections to the gas tubes, the tingle was gone but replaced by hum on low sound volume.
So the grounding was removed again.
Most well-experienced technicians are "well grounded" in their knowledge base.
"Grounds are Commonly Misunderstood" - me
Stray capacitance, inductance of wires, resistance of wires, and all other parasitics . . . exist in order to provide us with ground loops.
Murphy at work.
"Grounds are Commonly Misunderstood" - me
Stray capacitance, inductance of wires, resistance of wires, and all other parasitics . . . exist in order to provide us with ground loops.
Murphy at work.
An observation of consumer electronics sold in Canada (AV equipment, kitchen countertop appliances, lamps, and some TVs without centred removable stands) is most do not have grounded three-wire plugs, including products with exposed stainless bodies. Some electronic devices even have reversible plugs. I have a few of those. I may have owned one piece of audio gear having a grounded plug. The chassis are only grounded for RFI/EMI by Y-safety capacitors to the hot and neutral wires entering the chassis.
It’s easy to state they must be double insulated, I see that online all the time when the topic is discussed, and a wall wart often is. Upon inspection of the other devices, however, there is the total absence of insulation around the power entry, wires and transformers in those ungrounded chassis. I have never seen an indication of additional transformer insulation either, so I contacted a transformer supplier for clarity about this and the reply was their transformers met Class II ratings without the additional layer between the windings. I don’t understand that. In fact, finding a ~400VA transformer with an extra layer was a bit of a task.
My father in-law, a retired inspector at CSA, and respected engineer, could not persuade a change to the rules. There might be a certain expected level of common sense, like don’t move electronics while they are plugged in, and don’t pour a drink over the toaster.
I can’t change what is, but when I build I ground the chassis to the receptacle earth through the three-wire power entry. Pin 1 of my XLRs ground to the chassis to act as an intended shield.
It’s easy to state they must be double insulated, I see that online all the time when the topic is discussed, and a wall wart often is. Upon inspection of the other devices, however, there is the total absence of insulation around the power entry, wires and transformers in those ungrounded chassis. I have never seen an indication of additional transformer insulation either, so I contacted a transformer supplier for clarity about this and the reply was their transformers met Class II ratings without the additional layer between the windings. I don’t understand that. In fact, finding a ~400VA transformer with an extra layer was a bit of a task.
My father in-law, a retired inspector at CSA, and respected engineer, could not persuade a change to the rules. There might be a certain expected level of common sense, like don’t move electronics while they are plugged in, and don’t pour a drink over the toaster.
I can’t change what is, but when I build I ground the chassis to the receptacle earth through the three-wire power entry. Pin 1 of my XLRs ground to the chassis to act as an intended shield.
Double insulation just means that, you need 2 independent "layers" of insulation between mains and the rest of the appliance. It can have a metal outside that is not connected to safety earth because those 2 layers make sure that even if a single layer breaks down, the other layer ensures isolation.
Having a single layer that has the same rating as a double insulation isn't a double insulation and cannot be considered compliant. That would fall under the classification of "reinforced insulation".
An XLR should have its metal parts connected to safety ground and pin 1 to signal ground. That is somewhere connected to safety ground at a point consistent with operation of the appliance. Very likely at the entrance but it doesn't need to be that way.
Having a single layer that has the same rating as a double insulation isn't a double insulation and cannot be considered compliant. That would fall under the classification of "reinforced insulation".
An XLR should have its metal parts connected to safety ground and pin 1 to signal ground. That is somewhere connected to safety ground at a point consistent with operation of the appliance. Very likely at the entrance but it doesn't need to be that way.
I have never heard of Pin 1 being connected to signal ground. The shell and Pin 1 are always connected to chassis safety ground, in my experience, since if they are connected to signal ground they inject noise pickup onto that ground. Pin 1 is not an audio common.
It has, but it is connected with an ungrounded extension lead.
So the grounds are floating.
The tingling may be caused by leakage current from EMI suppression capacitors in PSU. Many 2-pin plug devices using SMPS PSUs have their chassis at 115VAC (in 230VAC system) due to these capacitors. As the impedance is high the "electric shock" current is low (below 1mA) but can be felt as tingling.
Post #7 of this thread links to an article bij David Davenport on the subject of Audio Component Grounding and Interconnection. In it is referred to the "pin 1 problem" of XLR when it is designed wrong. It should be connected to chassis ground. Balanced audio does not require the shield to be connected to the signal reference as a return path like single ended does.
Obviously, it will end up connected to it through the star ground on the chassis anyway as for good shielding signal reference must also be connected to chassis ground. Connecting XLR pin 1 direct to chassis star ground gives the noise on the shield a low impedance return path "far" from the signal reference.
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Well, there you have the source of the tingle.
Grouding on pipes isn't allowed anymore nowadays as more and more are non-conductive (gas and water have alle switched to plastics). Grounding on pipes could - in case of a fault - make them live if their connection to earth has too high an impedance. There have been deaths in the shower in this country caused by electrocution as a result of such a situation.
Yes, you have rewritten most everything in my post. Pin 1 to chassis, which is safety grounded to the receptacle’s earth. This is the low impedance path. If Pin 1 is terminated directly to the audio signal ground, and to go a step further for clarity I’ll use the audio signal input end of a PCB for this example, it would introduce noise as the currents pass the length of the board’s ground to the end where it’s grounded to the chassis.
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