Earthing arrangement(s) at mines & quarries in NSW showing the 'tension' with AS/NZS 3000:2007 definitions. AS/NZS 3000 is a mandatory standard on the surface of mines in NSW

1. Confused ‘MEN’
MEN & other TN Earthing Systems
Confused ‘MEN’ – Bernard Gittins – Mine Safety Operations – July 2015

2. Note!
Whilst the presenter is a member of several of the
Australian standards committees whose standards are
discussed in this paper, this paper in no way represents
the official position of those committees.
Confused ‘MEN’ – Bernard Gittins – Mine Safety – July 2015

3. Confused ‘MEN’
 What Confusion?
 ‘MEN’ & other ‘TN” earthing in AS/NZS3000
– The ‘ambiguous’ definition of ‘MEN’ in the definitions section
– The ‘problematic’ AS/NZS3000 Clause 5.1.3
– The generic / inappropriate use of the term ‘MEN’
 A suggested way forward

4. The ‘ambiguous’ definition of MEN in AS3000
Clause 1.4.66
Multiple Earthed Neutral (MEN) system
‘A system of earthing in which the parts of an electrical installation
required to be earthed in accordance with this standard are
connected together to form an equipotentially bonded network and this
network is connected to both the neutral conductor of the supply and
the general mass of earth.’
Compare this with TN earthing in AS/NZS 3007 Appendix A2 Clause (a)
TN system
Power systems having the earthable point (neutral) directly connected to
earth, the exposed conductive parts of the installation being connected by
protective conductors to the earthable point of the power system.

5. AS 3000 Multiple Earthed Neutral system definition problem
‘A system of earthing in which the parts of an electrical installation
required to be earthed in accordance with this standard are connected
together to form an equipotentially bonded network and this network
is connected to both the neutral conductor of the supply and the
general mass of earth.’
IEC60364.1
Figure 31A1

6. AS 3000 Multiple Earthed Neutral system definition problem
‘A system of earthing in which the parts of an electrical installation
required to be earthed in accordance with this standard are connected
together to form an equipotentially bonded network and this network
is connected to both the neutral conductor of the supply and the
general mass of earth.’

7. AS 3000 Multiple Earthed Neutral system definition problem
‘A system of earthing in which the parts of an electrical installation
required to be earthed in accordance with this standard are connected
together to form an equipotentially bonded network and this network
is connected to both the neutral conductor of the supply and the
general mass of earth.’

8. AS 3000 Multiple Earthed Neutral system definition problem
‘A system of earthing in which the parts of an electrical installation
required to be earthed in accordance with this standard are connected
together to form an equipotentially bonded network and this network
is connected to both the neutral conductor of the supply and the
general mass of earth.’
N-E Link

9. AS 3000 Multiple Earthed Neutral system definition problem
‘A system of earthing in which the parts of an electrical installation
required to be earthed in accordance with this standard are connected
together to form an equipotentially bonded network and this network
is connected to both the neutral conductor of the supply and the
general mass of earth.’

10. AS 3000 Multiple Earthed Neutral system definition problem
‘A system of earthing in which the parts of an electrical installation
required to be earthed in accordance with this standard are connected
together to form an equipotentially bonded network and this network
is connected to both the neutral conductor of the supply and the
general mass of earth.’
Does not fit the
description of a
MEN system as found
in AS/NZS 3000 Cl
5.1.3
Installation shown
satisfies the MEN
definition of Cl 1.4.66
Not a MEN earthing
installation

11. AS 3000 Multiple Earthed Neutral system definition problem
‘A system of earthing in which the parts of an electrical installation
required to be earthed in accordance with this standard are connected
together to form an equipotentially bonded network and this network
is connected to both the neutral conductor of the supply and the
general mass of earth at the origin of the installation.’
In Europe it is
normally the earth
that is reticulated
as a PEN, in
Australia it is the
neutral which is
reticulated as a
PEN.
MEN earthing is a
variant of TN-C-S
earthing.

12. MEN earthing system as described in AS/NZS3000?
The problematical Clause 5.1.3…
5.1.3 MEN earthing system
The protective earthing arrangements required
in this Standard apply to electrical installations
connected to the multiple earthed neutral
(MEN) distribution system that forms the
standard distribution system used in Australia
and New Zealand.
- typically a three phase + neutral (PEN)
distribution system
- implies the standard is limited to urban
residential and light industry
application?

13. So how is the MEN earthing system described in
AS/NZS3000?
The problematical Clause 5.1.3…
5.1.3 MEN earthing system
The protective earthing arrangements required
in this Standard apply to electrical installations
connected to the multiple earthed neutral
(MEN) distribution system that forms the
standard distribution system used in Australia
and New Zealand.
- there are other non-MEN earthing systems
in electrical installations in Australia
- eg the light is not a MEN installation

14. Street lighting not covered by Clause 5.1.3 ?
N-Frame link
X X
Earthing is complex and cannot be described by simple generic
terms

15. Description of MEN in Clause 5.1.3 cntd
Clause 5.1.3 (paragraph 2)
Under the MEN system the neutral conductor of the distribution system
is earthed at the source of supply, at regular intervals throughout the
system and at each electrical installation connected to the system.
&
Within the electrical installation, the earthing system is separated from
the neutral conductor and is arranged for the connection of the
exposed conductive parts of equipment.
- a good description of an MEN system…..
- the presence of regular/multiple earthing (electrodes) enables the
standard not require any performance criteria for any particular
electrode!
- provides very effective earthing for urban areas
- but a normative reading of the first paragraph of Clause 5.1.3
implies that this is the only earthing system considered/required by
AS/NZS3000 !

17. Installation 1
eg, residence,
a block of units
Installation 2
eg out-buildings
Distribution
Section
eg power lines in suburbia, but
not to a mine or quarry

18. Installation 1
eg, residence,
a block of units
or a mine?
Installation 2
eg out-buildings
Distribution
Section
Supply PEN has many
earthing connections
called MEN links
PENs are part of the
supply system

19. Installation 1
eg, residence,
a block of units
or a mine?
Installation 2
eg out-buildings
Distribution
Section
One MEN per
Installation

20. Installation 1
eg, residence,
a block of units
or a mine?
Installation 2
eg out-buildings
Distribution
Section
Typical of a
Class 1
equipment
Installation
(TN-S)
Typical sub-
board in the
installation
(TN-S)
Aside:
The outbuilding
submain cannot be
protected by earth
leakage protection
due to the down-
stream MEN link

21. Difficulties of AS/NZS 3000 Clause 5.1.3
- mines & quarries are not
connected to MEN distribution
systems as described/required in
Cl 5.1.3
- the LV side of the transformer may
be connected to a TN-S earthing
system (or even an IT system).
- but paragraph 1 says
…The protective earthing arrangements required in this Standard apply to
electrical installations connected to the multiple earthed neutral (MEN)
distribution system that forms the standard distribution system used in
Australia and New Zealand.

22. AS/NZS3000 & Legislation
WHS(M)R Clause 32 (2)(a)
….. the mine operator must ensure:
(a)that electrical installation work
at the surface is carried out in
accordance with the Wiring
Rules ….
Question:
Do we have a problem?

23. Figure 5.2. An Alternative
arrangement ….
Not a MEN installation because:
- there is no MEN link at the origin
of the LV installation
- there is no installation earthing
electrode
- not supplied by a distributed MEN
network (see Cl 5.1.3)
- only one possible N-E link in the
total network
Such installations can be found at
some quarries
- normally pole-top transformers
- sometimes without the PEN and
neutral bar at transformer
- enables earth leakage protection
of the LV mains
This configuration is what the IEC call
a TN-S system of earthing
Supply
Installation
Generic use of
term ‘MEN’

24. Now it is clearly a ‘TN-C-S installation’
Installation
- common installation at
mines with both pad and
pole mounted transformers
Supply
Kiosk Tx
- main switchboard contains
the ‘N-E link’ and earth
electrode at the origin of the
installation
- ‘awkward fit’ to Clause 5.1.3
re description wrt multiple E-N
connections in the distribution
system supplying to the
installation
- PEN from supply
- really an alternate ‘MEN’
installation

25. Where to now?
- limit the term ‘MEN’ to urban distribution MEN systems
- utilise IEC terminology for all other installations

26. AS/NZS 3000 ‘alignment’ of terminology with IEC
AS/NZS 3000:2007 Clause 5.1.3
NOTE
IEC 60364 describes the MEN system as a TN-C-S system with the letters
signifying—
T the distribution system is directly connected to earth—at the neutral point of
the supply transformer (AS/NZS  IEC  )
N the exposed conductive parts are connected to the earthed point of the
distribution system—at the MEN connection ( AS/NZS  IEC  )
C the neutral and protective conductor functions are combined in a single
conductor (the neutral conductor of the distribution system) (AS/NZS  IEC X)
S the protective conductor within the installation is separated from the neutral
conductor (AS/NZS  IEC  )

27. Earthing system definitions aligned to the IEC 60364
for AS/NZS3000?
IT System
TN system
TN-C system … street lighting
TN-S system … for mines, heavy industry /and sub-boards
TN-C-S … (except for urban distributed TN-C-S systems – MEN)
TT System ?
Ditto: AS/NZS3010, AS/NZS3012, AS/NZS4059 etc

28. Summary of Presenter’s Thoughts
 AS/NZS 3000 defines MEN earthing incorrectly in its ‘all inclusive‘ TN
earthing definition
 AS/NZS 3000 Sect 5 is written for installations connected to MEN
distribution networks (user beware)
 Mine electrical installations are not connected to the distributed MEN
networks as described in Clause 5.1.3. Such installations would be better
described utilising the appropriate IEC terminology
 The term ’MEN’ in AS/NZS 3000 is often used in a generic sense which
is not always technically correct or helpful … ‘easily’ fixed
 There is a need to bring AS/NZS3000 into closer alignment with IEC
60364.1 definitions
 The distinction between MEN earthing and other forms of TN-C-S
earthing needs to be managed and explained in AS/NZS3000.
 AS/NZS3000 is mandated for mines; use it carefully 

29. Thanks