Re: [PSES] insulation between SELV and protective earthed accessible part- IEC 62052-31

2018-03-14 Thread John Woodgate 

See below.

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

On 2018-03-13 19:57, John Woodgate wrote:


I suspect that the SELV circuits of an electricity meter never leave 
the enclosure, so SELV is OK, but PELV would still be equally safe or 
better, even if a very low probability open-circuit earth occurred.


John Woodgate OOO-Own Opinions Only
J M Woodgate and Associateswww.woodjohn.uk
Rayleigh, Essex UK
On 2018-03-13 19:17, Ted Eckert wrote:


Part of the reason why two levels of protection are required is 
because of what happens if one level fails. If the protective earth 
bonding connection fails, and the exposed metal is no longer earthed, 
the product will typically continue to operate normally. There is no 
indication to the user that a failure has occurred. If a second 
failure occurs that bridges the insulation gap between hazardous 
voltage and that exposed metal, the chassis will become energized. 
The user may still have no obvious indication of a failure until they 
contact that energized chassis.


Different standards committees have different ways of addressing this 
issue. TC 108 generally requires that the protective earth bonding be 
designed and tested in such a way to prove that it is robust enough. 
In many ITE products, the user accessible circuits are earth ground 
references, so providing basic insulation between SELV and earth 
ground is not possible. Other standards committees may have chosen 
other methods of protection based on the products they cover. TC 13 
may have decided that basic insulation between SELV and earthed parts 
may be the best way to provide protection in their products. In this 
case, if the earth bonding fails, the basic insulation may be need to 
reduce the risk or arcing between hazardous voltage and the exposed 
metal.


Ted Eckert

Microsoft Corporation

The opinions expressed are my own and do not necessarily reflect 
those of my employer, TC 13 or TC 108.


*From:* Scott Aldous <0220f70c299a-dmarc-requ...@ieee.org 
<mailto:0220f70c299a-dmarc-requ...@ieee.org>>

*Sent:* Tuesday, March 13, 2018 8:57 AM
*To:* EMC-PSTC@LISTSERV.IEEE.ORG <mailto:EMC-PSTC@LISTSERV.IEEE.ORG>
*Subject:* Re: [PSES] insulation between SELV and protective earthed 
accessible part- IEC 62052-31


Hi Vyas,

I'm not familiar with this standard, but the general principle is 
that 2 levels of protection are required to protect operators from 
hazards. In the case of the "protective earthed accessible part", I 
imagine the standard assumes that a single fault could compromise the 
protective earthing, so Basic or Supplementary Insulation is also 
required between such a circuit and SELV. In the same vein, the table 
requires Double or Reinforced Insulation between an "unearthed 
accessible part" and SELV.


On Tue, Mar 13, 2018 at 5:56 AM, Balmukund Vyas 
<balmukund.v...@ymllabs.com <mailto:balmukund.v...@ymllabs.com>> wrote:


Dear All,

IEC 62052-31 is standard for product safety requirements for
electricity metering equipment. It has a table 20 (given below)
which details out insulation requirements between various types
of circuits.

My question is, why Basic insulation is required between SELV
circuit and protective earthed accessible parts? Isn’t a
functional insulation is sufficient for this?

Thanks

B M Vyas

-


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Re: [PSES] insulation between SELV and protective earthed accessible part- IEC 62052-31

2018-03-13 Thread Balmukund Vyas 

Thanks for your comments. The definitions of SEL and PELV in IEC 62052-31 are 
as below. Do you find it different?
Regards

B M Vyas

SELV system

An electrical system in which the voltage cannot exceed ELV:

· under normal conditions; and

· under single-fault conditions, including earth faults in other circuits

[IEC 61140 3.26.1]

1.1

PELV system

an electrical system in which the voltage cannot exceed ELV:

· under normal conditions, and

· under single-fault conditions, except earth faults in other circuits

[IEC 61140 3.26.1]



From: John Woodgate [mailto:j...@woodjohn.uk]
Sent: 14 March 2018 00:58
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] insulation between SELV and protective earthed accessible 
part- IEC 62052-31


I agree:  SELV as a low-voltage earth-free supply is not actually a safe 
concept. It's OK for short connections in the same space, because the 
probability of 'power cross' is extremely remote. But if SELV is extended into 
several spaces, including, for example, a void, the chance of power-cross is 
larger and it will remain undetected until someone touches both the SELV and 
earth.

John Woodgate OOO-Own Opinions Only

J M Woodgate and Associates www.woodjohn.uk<http://www.woodjohn.uk>

Rayleigh, Essex UK
On 2018-03-13 19:13, Richard Nute wrote:

Dear Mr. Vyas:

I suggest you review the definitions for SELV and PELV in IEC 62052.  These 
definitions are not the same throughout IEC standards.  (I don’t have IEC 
62052.)

In some standards, SELV is isolated from protective earth, and PELV is 
connected to protective earth.  If these are the definitions in IEC 62052, then 
SELV must be isolated from earth by Basic Insulation.  (I have never understood 
why we have both SELV and PELV as only the voltage and the isolation are the 
essential parameters for protection against electric shock.)

In other standards, SELV is determined by the voltage and the isolation from 
higher voltages; earthing (or not) of SELV does not enter into this 
determination.

Good luck and best regards,
Rich



From: Balmukund Vyas 
<balmukund.v...@ymllabs.com><mailto:balmukund.v...@ymllabs.com>
Sent: Tuesday, March 13, 2018 5:56 AM
To: EMC-PSTC@LISTSERV.IEEE.ORG<mailto:EMC-PSTC@LISTSERV.IEEE.ORG>
Subject: [PSES] insulation between SELV and protective earthed accessible part- 
IEC 62052-31



Dear All,
IEC 62052-31 is standard for product safety requirements for electricity 
metering equipment. It has a table 20 (given below) which details out 
insulation requirements between various types of circuits.
My question is, why Basic insulation is required between SELV circuit and 
protective earthed accessible parts? Isn’t a functional insulation is 
sufficient for this?

Thanks

B M Vyas


Table 20 – Insulation requirements between circuits and between circuits and 
accessible parts




HLV
mains-circuit1)


ELV circuit


SELV circuit


PELV circuit


PEB circuit2)


Protective earthed HLV non-mains-circuit2), 3)


Unearthed HLV non-mains circuit3)


HLV mains-circuit 1)


F/B1) 6)

Table 8Table 9


B

Table 8Table 9


D

Table 8Table 9


D

Table 8Table 9


B5)

Table 8Table 9


B

Table 8Table 9


B

Table 8Table 9


ELV circuit


B

Table 8Table 9


F/B6)

Table 13Table 14


B

Table 13Table 14


B

Table 13Table 14


F/B5), 6)

Table 13Table 14


B

Table 13Table 14


B

Table 13Table 14


SELV circuit


D

Table 8Table 9


B

Table 13Table 14


F/B6)

Table 13Table 14


F/B8)

Table 13Table 14


B

Table 13Table 14


D

Table 13Table 14


D

Table 13Table 14


PELV circuit2)


D

Table 8Table 9


B

Table 13Table 14


F/B8)

Table 13Table 14


F/B6)

Table 13Table 14


B

Table 13Table 14


D

Table 13Table 14


D

Table 13Table 14


PEB circuit2)


B5)

Table 8Table 9


F/B5), 6)

Table 13Table 14


B

Table 13Table 14


B

Table 13Table 14


F/B5)

Table 13Table 14


B

Table 13Table 14


B

Table 13Table 14


Protective earthed HLV non-mains circuit2), 3)


B

Table 8Table 9


B

Table 8Table 9


D

Table 8Table 9


D

Table 8Table 9


B

Table 8Table 9


F/B6)

Table 8Table 9


B

Table 8Table 9


Unearthed HLV non-mains circuit3)


B

Table 13Table 14


B

Table 13Table 14


D

Table 13Table 14


D

Table 13Table 14


B

Table 13Table 14


B

Table 13Table 14


F/B6)

Table 13Table 14


Protective earthed accessible part2), 7)


B

Table 8Table 9


F/B6)

Table 13Table 14


B

Table 13Table 14


B

Table 13Table 14


F/B6)

Table 13Table 14


B

Table 13Table 14


B

Table 13Table 14


Unearthed accessible part7)


D

Table 8Table 9


B

Table 13Table 14


B

Table 13Table 14


F/B6)

Table 13Table 14


B

Table 13Table 14


D

Table 13Table 14


B/D 4)

Table 13Table 14


Abbreviations for insulations:

B: Basic insulation or supplementary insulation

D: double insulation or reinforced insulation

F: Functional insulation

S: Supplementary insulation


1)If the functional voltage (not relative to earth/ground) is 
greater than the

Re: [PSES] insulation between SELV and protective earthed accessible part- IEC 62052-31

2018-03-13 Thread John Woodgate 
I suspect that the SELV circuits of an electricity meter never leave the 
enclosure, so SELV is OK, but PELV would still be equally safe or 
better, even if a very low probability open-circuit earth occurred.


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

On 2018-03-13 19:17, Ted Eckert wrote:


Part of the reason why two levels of protection are required is 
because of what happens if one level fails. If the protective earth 
bonding connection fails, and the exposed metal is no longer earthed, 
the product will typically continue to operate normally. There is no 
indication to the user that a failure has occurred. If a second 
failure occurs that bridges the insulation gap between hazardous 
voltage and that exposed metal, the chassis will become energized. The 
user may still have no obvious indication of a failure until they 
contact that energized chassis.


Different standards committees have different ways of addressing this 
issue. TC 108 generally requires that the protective earth bonding be 
designed and tested in such a way to prove that it is robust enough. 
In many ITE products, the user accessible circuits are earth ground 
references, so providing basic insulation between SELV and earth 
ground is not possible. Other standards committees may have chosen 
other methods of protection based on the products they cover. TC 13 
may have decided that basic insulation between SELV and earthed parts 
may be the best way to provide protection in their products. In this 
case, if the earth bonding fails, the basic insulation may be need to 
reduce the risk or arcing between hazardous voltage and the exposed metal.


Ted Eckert

Microsoft Corporation

The opinions expressed are my own and do not necessarily reflect those 
of my employer, TC 13 or TC 108.


*From:* Scott Aldous <0220f70c299a-dmarc-requ...@ieee.org 
<mailto:0220f70c299a-dmarc-requ...@ieee.org>>

*Sent:* Tuesday, March 13, 2018 8:57 AM
*To:* EMC-PSTC@LISTSERV.IEEE.ORG <mailto:EMC-PSTC@LISTSERV.IEEE.ORG>
*Subject:* Re: [PSES] insulation between SELV and protective earthed 
accessible part- IEC 62052-31


Hi Vyas,

I'm not familiar with this standard, but the general principle is that 
2 levels of protection are required to protect operators from hazards. 
In the case of the "protective earthed accessible part", I imagine the 
standard assumes that a single fault could compromise the protective 
earthing, so Basic or Supplementary Insulation is also required 
between such a circuit and SELV. In the same vein, the table requires 
Double or Reinforced Insulation between an "unearthed accessible part" 
and SELV.


On Tue, Mar 13, 2018 at 5:56 AM, Balmukund Vyas 
<balmukund.v...@ymllabs.com <mailto:balmukund.v...@ymllabs.com>> wrote:


Dear All,

IEC 62052-31 is standard for product safety requirements for
electricity metering equipment. It has a table 20 (given below)
which details out insulation requirements between various types of
circuits.

My question is, why Basic insulation is required between SELV
circuit and protective earthed accessible parts? Isn’t a
functional insulation is sufficient for this?

Thanks

B M Vyas

-


This message is from the IEEE Product Safety Engineering Society 
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e-mail to <emc-p...@ieee.org <mailto:emc-p...@ieee.org>>


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graphics (in well-used formats), large files, etc.


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Instructions:  http://www.

Re: [PSES] insulation between SELV and protective earthed accessible part- IEC 62052-31

2018-03-13 Thread Ted Eckert 
Part of the reason why two levels of protection are required is because of what 
happens if one level fails. If the protective earth bonding connection fails, 
and the exposed metal is no longer earthed, the product will typically continue 
to operate normally. There is no indication to the user that a failure has 
occurred. If a second failure occurs that bridges the insulation gap between 
hazardous voltage and that exposed metal, the chassis will become energized. 
The user may still have no obvious indication of a failure until they contact 
that energized chassis.

Different standards committees have different ways of addressing this issue. TC 
108 generally requires that the protective earth bonding be designed and tested 
in such a way to prove that it is robust enough. In many ITE products, the user 
accessible circuits are earth ground references, so providing basic insulation 
between SELV and earth ground is not possible. Other standards committees may 
have chosen other methods of protection based on the products they cover. TC 13 
may have decided that basic insulation between SELV and earthed parts may be 
the best way to provide protection in their products. In this case, if the 
earth bonding fails, the basic insulation may be need to reduce the risk or 
arcing between hazardous voltage and the exposed metal.


Ted Eckert
Microsoft Corporation

The opinions expressed are my own and do not necessarily reflect those of my 
employer, TC 13 or TC 108.

From: Scott Aldous 
<0220f70c299a-dmarc-requ...@ieee.org<mailto:0220f70c299a-dmarc-requ...@ieee.org>>
Sent: Tuesday, March 13, 2018 8:57 AM
To: EMC-PSTC@LISTSERV.IEEE.ORG<mailto:EMC-PSTC@LISTSERV.IEEE.ORG>
Subject: Re: [PSES] insulation between SELV and protective earthed accessible 
part- IEC 62052-31

Hi Vyas,

I'm not familiar with this standard, but the general principle is that 2 levels 
of protection are required to protect operators from hazards. In the case of 
the "protective earthed accessible part", I imagine the standard assumes that a 
single fault could compromise the protective earthing, so Basic or 
Supplementary Insulation is also required between such a circuit and SELV. In 
the same vein, the table requires Double or Reinforced Insulation between an 
"unearthed accessible part" and SELV.

On Tue, Mar 13, 2018 at 5:56 AM, Balmukund Vyas 
<balmukund.v...@ymllabs.com<mailto:balmukund.v...@ymllabs.com>> wrote:


Dear All,
IEC 62052-31 is standard for product safety requirements for electricity 
metering equipment. It has a table 20 (given below) which details out 
insulation requirements between various types of circuits.
My question is, why Basic insulation is required between SELV circuit and 
protective earthed accessible parts? Isn’t a functional insulation is 
sufficient for this?

Thanks

B M Vyas


-

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:
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/
Instructions:  http://www.ieee-pses.org/list.html (including how to unsubscribe)
List rules: http://www.ieee-pses.org/listrules.html

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Mike Cantwell <mcantw...@ieee.org>

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Re: [PSES] insulation between SELV and protective earthed accessible part- IEC 62052-31

2018-03-13 Thread John Woodgate 
I agree:  SELV as a low-voltage earth-free supply is not actually a safe 
concept. It's OK for short connections in the same space, because the 
probability of 'power cross' is extremely remote. But if SELV is 
extended into several spaces, including, for example, a void, the chance 
of power-cross is larger and it will remain *undetected* until someone 
touches both the SELV and earth.


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

On 2018-03-13 19:13, Richard Nute wrote:


Dear Mr. Vyas:

I suggest you review the definitions for SELV and PELV in IEC 62052.  
These definitions are not the same throughout IEC standards.  (I don’t 
have IEC 62052.)


In some standards, SELV is isolated from protective earth, and PELV is 
connected to protective earth.  If these are the definitions in IEC 
62052, then SELV must be isolated from earth by Basic Insulation.  (I 
have never understood why we have both SELV and PELV as only the 
voltage and the isolation are the essential parameters for protection 
against electric shock.)


In other standards, SELV is determined by the voltage and the 
isolation from higher voltages; earthing (or not) of SELV does not 
enter into this determination.


Good luck and best regards,

Rich

*From:* Balmukund Vyas <balmukund.v...@ymllabs.com>
*Sent:* Tuesday, March 13, 2018 5:56 AM
*To:* EMC-PSTC@LISTSERV.IEEE.ORG
*Subject:* [PSES] insulation between SELV and protective earthed 
accessible part- IEC 62052-31


Dear All,

IEC 62052-31 is standard for product safety requirements for 
electricity metering equipment. It has a table 20 (given below) which 
details out insulation requirements between various types of circuits.


My question is, why Basic insulation is required between SELV circuit 
and protective earthed accessible parts? Isn’t a functional insulation 
is sufficient for this?


Thanks

B M Vyas

Table 20 – Insulation requirements between circuits and between 
circuits and accessible parts




HLV
mains-circuit^1)



ELV circuit



SELV circuit



PELV circuit



PEB circuit^2)



Protective earthed HLV non-mains-circuit^2), 3)



Unearthed HLV non-mains circuit^3)

HLV mains-circuit ^1)



F/B^1) 6)

Table 8Table 9



B

Table 8Table 9



D

Table 8Table 9



D

Table 8Table 9



B^5)

Table 8Table 9



B

Table 8Table 9



B

Table 8Table 9

ELV circuit



B

Table 8Table 9



F/B^6)

Table 13Table 14



B

Table 13Table 14



B

Table 13Table 14



F/B^5), 6)

Table 13Table 14



B

Table 13Table 14



B

Table 13Table 14

SELV circuit



D

Table 8Table 9



B

Table 13Table 14



F/B^6)

Table 13Table 14



F/B^8)

Table 13Table 14



B

Table 13Table 14



D

Table 13Table 14



D

Table 13Table 14

PELV circuit^2)



D

Table 8Table 9



B

Table 13Table 14



F/B^8)

Table 13Table 14



F/B^6)

Table 13Table 14



B

Table 13Table 14



D

Table 13Table 14



D

Table 13Table 14

PEB circuit^2)



B^5)

Table 8Table 9



F/B^5), 6)

Table 13Table 14



B

Table 13Table 14



B

Table 13Table 14



F/B^5)

Table 13Table 14



B

Table 13Table 14



B

Table 13Table 14

Protective earthed HLV non-mains circuit^2), 3)



B

Table 8Table 9



B

Table 8Table 9



D

Table 8Table 9



D

Table 8Table 9



B

Table 8Table 9



F/B^6)

Table 8Table 9



B

Table 8Table 9

Unearthed HLV non-mains circuit^3)



B

Table 13Table 14



B

Table 13Table 14



D

Table 13Table 14



D

Table 13Table 14



B

Table 13Table 14



B

Table 13Table 14



F/B^6)

Table 13Table 14

Protective earthed accessible part^2), 7)



B

Table 8Table 9



F/B^6)

Table 13Table 14



B

Table 13Table 14



B

Table 13Table 14



F/B^6)

Table 13Table 14



B

Table 13Table 14



B

Table 13Table 14

Unearthed accessible part^7)



D

Table 8Table 9



B

Table 13Table 14



B

Table 13Table 14



F/B^6)

Table 13Table 14



B

Table 13Table 14



D

Table 13Table 14



B/D ^4)

Table 13Table 14

Abbreviations for insulations:

B: Basic insulation or supplementary insulation

D: double insulation or reinforced insulation

F: Functional insulation

S: Supplementary insulation

1)If the functional voltage (not relative to earth/ground) is greater 
than the rated insulation voltage, the creepage distance for the 
functional insulation may be greater than that for the basic 
insulation. An example is a terminal block of a three-phase metering 
equipment with /U/_n = 230/400 V,

Re: [PSES] insulation between SELV and protective earthed accessible part- IEC 62052-31

2018-03-13 Thread Richard Nute 
 

Dear Mr. Vyas:

 

I suggest you review the definitions for SELV and PELV in IEC 62052.  These 
definitions are not the same throughout IEC standards.  (I don’t have IEC 
62052.)

 

In some standards, SELV is isolated from protective earth, and PELV is 
connected to protective earth.  If these are the definitions in IEC 62052, then 
SELV must be isolated from earth by Basic Insulation.  (I have never understood 
why we have both SELV and PELV as only the voltage and the isolation are the 
essential parameters for protection against electric shock.)  

 

In other standards, SELV is determined by the voltage and the isolation from 
higher voltages; earthing (or not) of SELV does not enter into this 
determination.   

 

Good luck and best regards,

Rich

 

 

 

From: Balmukund Vyas <balmukund.v...@ymllabs.com> 
Sent: Tuesday, March 13, 2018 5:56 AM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: [PSES] insulation between SELV and protective earthed accessible part- 
IEC 62052-31

 

 

 

Dear All,

IEC 62052-31 is standard for product safety requirements for electricity 
metering equipment. It has a table 20 (given below) which details out 
insulation requirements between various types of circuits.

My question is, why Basic insulation is required between SELV circuit and 
protective earthed accessible parts? Isn’t a functional insulation is 
sufficient for this?

 

Thanks

 

B M Vyas

 

Table 20 – Insulation requirements between circuits and between circuits and 
accessible parts


 

HLV 
mains-circuit1)

ELV circuit

SELV circuit

PELV circuit

PEB circuit2)

Protective earthed HLV non-mains-circuit2), 3)

Unearthed HLV non-mains circuit3)


HLV mains-circuit 1)

F/B1) 6)

Table 8Table 9

B

Table 8Table 9

D

Table 8Table 9

D

Table 8Table 9

B5)

Table 8Table 9

B

Table 8Table 9

B

Table 8Table 9


ELV circuit

B

Table 8Table 9

F/B6)

Table 13Table 14

B

Table 13Table 14

B

Table 13Table 14

F/B5), 6)

Table 13Table 14

B

Table 13Table 14

B

Table 13Table 14


SELV circuit

D

Table 8Table 9

B

Table 13Table 14

F/B6)

Table 13Table 14

F/B8)

Table 13Table 14

B

Table 13Table 14

D

Table 13Table 14

D

Table 13Table 14


PELV circuit2)

D

Table 8Table 9

B

Table 13Table 14

F/B8)

Table 13Table 14

F/B6)

Table 13Table 14

B

Table 13Table 14

D

Table 13Table 14

D

Table 13Table 14


PEB circuit2)

B5)

Table 8Table 9

F/B5), 6)

Table 13Table 14

B

Table 13Table 14

B

Table 13Table 14

F/B5)

Table 13Table 14

B

Table 13Table 14

B

Table 13Table 14


Protective earthed HLV non-mains circuit2), 3)

B

Table 8Table 9

B

Table 8Table 9

D

Table 8Table 9

D

Table 8Table 9

B

Table 8Table 9

F/B6)

Table 8Table 9

B

Table 8Table 9


Unearthed HLV non-mains circuit3)

B

Table 13Table 14

B

Table 13Table 14

D

Table 13Table 14

D

Table 13Table 14

B

Table 13Table 14

B

Table 13Table 14

F/B6)

Table 13Table 14


Protective earthed accessible part2), 7)

B

Table 8Table 9

F/B6)

Table 13Table 14

B

Table 13Table 14

B

Table 13Table 14

F/B6)

Table 13Table 14

B

Table 13Table 14

B

Table 13Table 14


Unearthed accessible part7)

D

Table 8Table 9

B

Table 13Table 14

B

Table 13Table 14

F/B6)

Table 13Table 14

B

Table 13Table 14

D

Table 13Table 14

B/D 4)

Table 13Table 14


Abbreviations for insulations:

B: Basic insulation or supplementary insulation

D: double insulation or reinforced insulation

F: Functional insulation

S: Supplementary insulation


1)If the functional voltage (not relative to earth/ground) is 
greater than the rated insulation voltage, the creepage distance for the 
functional insulation may be greater than that for the basic insulation. An 
example is a terminal block of a three-phase metering equipment with Un = 
230/400 V, where the functional phase-to-phase voltage is 400 V r.m.s. For an 
indoor meter with material group III, the creepage distance for basic 
insulation from Table 9 is 3,2 mm, but the creepage distance for functional 
insulationfrom Table 14 is 4,0 mm.

2)Connections to the protective conductor shall comply with 
6.5.2.4. Otherwise, this shall be considered to be an unearthed circuit.

3)There shall be at least basic insulation between HLV non-mains 
circuits and HLV mains circuits.

4)Insulation between an unearthed non-mains circuit at hazardous 
voltage and an unearthed accessible conductive part shall satisfy the more 
onerous of the following:

-   double/reinforced insulation, the working voltage of which is equal to 
the hazardous voltage; or

-   supplementary insulation, the working voltage of which is equal to the 
voltage between the non-mains circuit athazardous voltage; and

*  another non-mains circuit at hazardous voltage; or

*  a mains circuit.

5)See Annex Bfor the conditional use of basic insulation for PEB.

6)Supplementary or basic insulation shall be used if one of the 
circuits is an independent circuit or is ad

Re: [PSES] insulation between SELV and protective earthed accessible part- IEC 62052-31

2018-03-13 Thread Scott Aldous 
Hi Vyas,

I'm not familiar with this standard, but the general principle is that 2
levels of protection are required to protect operators from hazards. In the
case of the "protective earthed accessible part", I imagine the standard
assumes that a single fault could compromise the protective earthing, so
Basic or Supplementary Insulation is also required between such a circuit
and SELV. In the same vein, the table requires Double or Reinforced
Insulation between an "unearthed accessible part" and SELV.

On Tue, Mar 13, 2018 at 5:56 AM, Balmukund Vyas 
wrote:

>
>
>
>
> Dear All,
>
> IEC 62052-31 is standard for product safety requirements for electricity
> metering equipment. It has a table 20 (given below) which details out
> insulation requirements between various types of circuits.
>
> My question is, why Basic insulation is required between SELV circuit and
> protective earthed accessible parts? Isn’t a functional insulation is
> sufficient for this?
>
>
>
> Thanks
>
>
>
> B M Vyas
>
>
>
> Table 20 – Insulation requirements between circuits and between circuits
> and accessible parts
>
>
>
> HLV
> mains-circuit1)
>
> ELV circuit
>
> SELV circuit
>
> PELV circuit
>
> PEB circuit2)
>
> Protective earthed HLV non-mains-circuit2), 3)
>
> Unearthed HLV non-mains circuit3)
>
> HLV mains-circuit 1)
>
> F/B1) 6)
>
> Table 8Table 9
>
> B
>
> Table 8Table 9
>
> D
>
> Table 8Table 9
>
> D
>
> Table 8Table 9
>
> B5)
>
> Table 8Table 9
>
> B
>
> Table 8Table 9
>
> B
>
> Table 8Table 9
>
> ELV circuit
>
> B
>
> Table 8Table 9
>
> F/B6)
>
> Table 13Table 14
>
> B
>
> Table 13Table 14
>
> B
>
> Table 13Table 14
>
> F/B5), 6)
>
> Table 13Table 14
>
> B
>
> Table 13Table 14
>
> B
>
> Table 13Table 14
>
> SELV circuit
>
> D
>
> Table 8Table 9
>
> B
>
> Table 13Table 14
>
> F/B6)
>
> Table 13Table 14
>
> F/B8)
>
> Table 13Table 14
>
> B
>
> Table 13Table 14
>
> D
>
> Table 13Table 14
>
> D
>
> Table 13Table 14
>
> PELV circuit2)
>
> D
>
> Table 8Table 9
>
> B
>
> Table 13Table 14
>
> F/B8)
>
> Table 13Table 14
>
> F/B6)
>
> Table 13Table 14
>
> B
>
> Table 13Table 14
>
> D
>
> Table 13Table 14
>
> D
>
> Table 13Table 14
>
> PEB circuit2)
>
> B5)
>
> Table 8Table 9
>
> F/B5), 6)
>
> Table 13Table 14
>
> B
>
> Table 13Table 14
>
> B
>
> Table 13Table 14
>
> F/B5)
>
> Table 13Table 14
>
> B
>
> Table 13Table 14
>
> B
>
> Table 13Table 14
>
> Protective earthed HLV non-mains circuit2), 3)
>
> B
>
> Table 8Table 9
>
> B
>
> Table 8Table 9
>
> D
>
> Table 8Table 9
>
> D
>
> Table 8Table 9
>
> B
>
> Table 8Table 9
>
> F/B6)
>
> Table 8Table 9
>
> B
>
> Table 8Table 9
>
> Unearthed HLV non-mains circuit3)
>
> B
>
> Table 13Table 14
>
> B
>
> Table 13Table 14
>
> D
>
> Table 13Table 14
>
> D
>
> Table 13Table 14
>
> B
>
> Table 13Table 14
>
> B
>
> Table 13Table 14
>
> F/B6)
>
> Table 13Table 14
>
> Protective earthed accessible part2), 7)
>
> B
>
> Table 8Table 9
>
> F/B6)
>
> Table 13Table 14
>
> B
>
> Table 13Table 14
>
> B
>
> Table 13Table 14
>
> F/B6)
>
> Table 13Table 14
>
> B
>
> Table 13Table 14
>
> B
>
> Table 13Table 14
>
> Unearthed accessible part7)
>
> D
>
> Table 8Table 9
>
> B
>
> Table 13Table 14
>
> B
>
> Table 13Table 14
>
> F/B6)
>
> Table 13Table 14
>
> B
>
> Table 13Table 14
>
> D
>
> Table 13Table 14
>
> B/D 4)
>
> Table 13Table 14
>
> Abbreviations for insulations:
>
> B: Basic insulation or supplementary insulation
>
> D: double insulation or reinforced insulation
>
> F: Functional insulation
>
> S: Supplementary insulation
>
> 1)If the functional voltage (not relative to earth/ground) is
> greater than the rated insulation voltage, the creepage distance for the
> functional insulation may be greater than that for the basic insulation. An
> example is a terminal block of a three-phase metering equipment with *U*n
> = 230/400 V, where the functional phase-to-phase voltage is 400 V r.m.s.
> For an indoor meter with material group III, the creepage distance for
> basic insulation from Table 9 is 3,2 mm, but the creepage distance for
> functional insulationfrom Table 14 is 4,0 mm.
>
> 2)Connections to the protective conductor shall comply with
> 6.5.2.4. Otherwise, this shall be considered to be an unearthed circuit.
>
> 3)There shall be at least basic insulation between HLV
> non-mains circuits and HLV mains circuits.
>
> 4)Insulation between an unearthed non-mains circuit at
> hazardous voltage and an unearthed accessible conductive part shall satisfy
> the more onerous of the following:
>
> -   double/reinforced insulation, the working voltage of which is
> equal to the hazardous voltage; or
>
> -   supplementary insulation, the working voltage of which is equal
> to the voltage between the non-mains circuit athazardous voltage; and
>
> ·  another non-mains circuit at hazardous voltage; or
>
> ·  a mains circuit.
>
> 5)See Annex Bfor the conditional use of basic insulation for
> PEB.
>
> 6)

[PSES] insulation between SELV and protective earthed accessible part- IEC 62052-31

2018-03-13 Thread Balmukund Vyas 


Dear All,
IEC 62052-31 is standard for product safety requirements for electricity 
metering equipment. It has a table 20 (given below) which details out 
insulation requirements between various types of circuits.
My question is, why Basic insulation is required between SELV circuit and 
protective earthed accessible parts? Isn’t a functional insulation is 
sufficient for this?

Thanks

B M Vyas


Table 20 – Insulation requirements between circuits and between circuits and 
accessible parts




HLV
mains-circuit1)


ELV circuit


SELV circuit


PELV circuit


PEB circuit2)


Protective earthed HLV non-mains-circuit2), 3)


Unearthed HLV non-mains circuit3)


HLV mains-circuit 1)


F/B1) 6)

Table 8Table 9


B

Table 8Table 9


D

Table 8Table 9


D

Table 8Table 9


B5)

Table 8Table 9


B

Table 8Table 9


B

Table 8Table 9


ELV circuit


B

Table 8Table 9


F/B6)

Table 13Table 14


B

Table 13Table 14


B

Table 13Table 14


F/B5), 6)

Table 13Table 14


B

Table 13Table 14


B

Table 13Table 14


SELV circuit


D

Table 8Table 9


B

Table 13Table 14


F/B6)

Table 13Table 14


F/B8)

Table 13Table 14


B

Table 13Table 14


D

Table 13Table 14


D

Table 13Table 14


PELV circuit2)


D

Table 8Table 9


B

Table 13Table 14


F/B8)

Table 13Table 14


F/B6)

Table 13Table 14


B

Table 13Table 14


D

Table 13Table 14


D

Table 13Table 14


PEB circuit2)


B5)

Table 8Table 9


F/B5), 6)

Table 13Table 14


B

Table 13Table 14


B

Table 13Table 14


F/B5)

Table 13Table 14


B

Table 13Table 14


B

Table 13Table 14


Protective earthed HLV non-mains circuit2), 3)


B

Table 8Table 9


B

Table 8Table 9


D

Table 8Table 9


D

Table 8Table 9


B

Table 8Table 9


F/B6)

Table 8Table 9


B

Table 8Table 9


Unearthed HLV non-mains circuit3)


B

Table 13Table 14


B

Table 13Table 14


D

Table 13Table 14


D

Table 13Table 14


B

Table 13Table 14


B

Table 13Table 14


F/B6)

Table 13Table 14


Protective earthed accessible part2), 7)


B

Table 8Table 9


F/B6)

Table 13Table 14


B

Table 13Table 14


B

Table 13Table 14


F/B6)

Table 13Table 14


B

Table 13Table 14


B

Table 13Table 14


Unearthed accessible part7)


D

Table 8Table 9


B

Table 13Table 14


B

Table 13Table 14


F/B6)

Table 13Table 14


B

Table 13Table 14


D

Table 13Table 14


B/D 4)

Table 13Table 14


Abbreviations for insulations:

B: Basic insulation or supplementary insulation

D: double insulation or reinforced insulation

F: Functional insulation

S: Supplementary insulation


1)If the functional voltage (not relative to earth/ground) is 
greater than the rated insulation voltage, the creepage distance for the 
functional insulation may be greater than that for the basic insulation. An 
example is a terminal block of a three-phase metering equipment with Un = 
230/400 V, where the functional phase-to-phase voltage is 400 V r.m.s. For an 
indoor meter with material group III, the creepage distance for basic 
insulation from Table 9 is 3,2 mm, but the creepage distance for functional 
insulationfrom Table 14 is 4,0 mm.

2)Connections to the protective conductor shall comply with 
6.5.2.4. Otherwise, this shall be considered to be an unearthed circuit.

3)There shall be at least basic insulation between HLV non-mains 
circuits and HLV mains circuits.

4)Insulation between an unearthed non-mains circuit at hazardous 
voltage and an unearthed accessible conductive part shall satisfy the more 
onerous of the following:

-   double/reinforced insulation, the working voltage of which is equal to 
the hazardous voltage; or

-   supplementary insulation, the working voltage of which is equal to the 
voltage between the non-mains circuit athazardous voltage; and

·  another non-mains circuit at hazardous voltage; or

·  a mains circuit.

5)See Annex Bfor the conditional use of basic insulation for PEB.

6)Supplementary or basic insulation shall be used if one of the 
circuits is an independent circuit or is adjacent to a conductive part which 
may be earthed when the equipment is installed.

7)A functional earthed circuit shall be treated as an unearthed 
accessible part. The exception is where the functional earth is bonded to the 
protective conductor and this meets the relevant requirements, then it may be 
treated as an earthed accessible part.

8)For a PELV system earthed at one end of a cable run, it would be 
permissible to connect a SELV system at the other end.


NOTEReference is made to the respective tables specifying clearances and 
creepage distances.


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