TRANSMISSION AND DISTRIBUTION
Medium voltage fixed electrical
installations: SANS 10142 – Part 2
by Jaco van Heerden, TWP Projects
The use and application of the Wiring Code SANS 10142-1 is well known to all of us, and covers fixed electrical installations of
up to 1000 V AC and 1500 V DC and has been the topic of wide discussion over many years. This standard is called up by the
Occupational Health and Safety Act as well as for prescribed electrical installations by the Mines Health and Safety Act. A new
Part 2 of SANS 10142 has now been developed for voltages of up to 22 kV and power up to 3000 kW.
Developments during the past number of
years of self-contained residential villages,
sizeable commercial farms and even small
industrial sites created the need to receive
power at higher distribution voltages from
Licensed Suppliers. Design, construction,
commissioning and operation of these
installations in most instances took place
in an uncontrolled environment with
potential life threatening consequences.
The purpose of this paper is to explain the
reasons for compiling this new standard,
how it should be applied and what the
consequences it would have for the power
distribution equipment industr y and in
particular for designers and installers.
The aim of the new South African National
Standard
The little green book (grey book nowadays)
or SANS 1014 Part 1 as it was known so
well by the electrical contracting industry
covers all fixed electrical installations of up
to 1000 V AC and up to 1500 V DC. This
field of electrical supply is well understood
by most users of electricity and the
general rules are followed. Part 1 is clearly
referenced in the Occupational Health
and Safety Act and its stamp of authority
is generally well understood.
The nature of electrical supply to end
users has changed substantially over the
past two decades. Emergence of macro
commercial farmers and phenomenal
growth in eco-tourism has resulted in large
game farms and lodges being established
all over South Africa. In developed areas,
a strong trend toward security villages
caused used to group together rather
than applying individually for electrical
connections. The result of all this was
the emergence of many new medium
voltage points of control with voltage
transformation which had to be designed
constructed (and commissioned). Industrial
type medium voltage substations have
traditionally been designed by qualified
engineers and equipped with tested and
proven performance power distribution
equipment. A safety and performance void
was created where township developers
often weighs the CAPEX requirements of
establishing infrastructure in concentrated
developments to maximise profits to be
made.
The OHS Act and its regulations are
neither specific nor prescriptive on what is
required in terms of design, construction,
commissioning and operation when
a medium voltage supply has been
negotiated with a licensed supplier
o f e l e c t r i c i t y. M u n i c i p a l e l e c t r i c a l
undertakings and Eskom for several years
now are not involved or responsible for
the electricity supply once it crosses
the customer ’s boundar y. This is where
a prevailing void has been created
and especially small MV fixed electrical
installations are prone to being designed
and constructed by persons and installers
who may not be qualified nor competent
to perform such work.
During 2008 the SABS standards division
technical committee SC67F adopted the
IEC 61936-1 Power installations exceeding
1 kV AC-Part 1: Common rules. At the time
of developing the SANS 10142 Part 2, it was
felt that certain specific requirements for
MV electrical installation are applicable
for SA and that the IEC 61936-1 scope
is too wide. The IEC Standard is however
available for work on all HV Electrical
Installations.
The
purpose
of
the
new
SANS 10142 Part 2 is to provide, in a
convenient form, common rules for the
safety of specific, fixed, MV electrical
installations in systems with nominal
voltages above 1 kV AC not exceeding
22 kV AC and up to and including
3000 kW installed capacity. All parts of
the final MV installation below 1 kV are
covered by the requirements of SANS
10142-1. The upper voltage of 22 kV
was specifically selected since 11kV and
22 kV are common SA distribution voltages.
Specialised knowledge is required where
33 kV installations need to be designed.
The new Standard contains minimum
requirements and additional information
with regard to the safe operation, and
to ensure acceptable reliability, of the
medium-voltage part of an electrical
installation.
SANS 10142 Part 2 covers the system
engineering and erection, particularly
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concerning the safety aspects, of the said
electrical power installations. Installations
and equipment will be capable of
withstanding the electrical, mechanical,
climatic and environmental influences
anticipated on site.
The SABS technical committees for HV
equipment and for electrical distribution
established a working group to compile a
new Part 2 for SANS 10142 to address the
minimum safety requirements for medium
voltage fixed electrical installations above
1 kV AC and up to 22 kV AC and power
output of up to 3000 kW. The proposed
SANS 10142 Part 2 has passed through
all stages as a draft SA standard and has
been approved and published.
Who will be affected and who will be
advantaged by the new standard
The SANS 10142-Part 2 shall follow the same
route as SANS 10142-Part 1 where it will be
referenced in the Occupational Health and
Safety Act through the Electrical Machinery
Regulations. This action will firmly establish
the standard as compulsory for the range
of small medium voltage fixed electrical
installations. Specific medium voltage
electrical installations include residential
complexes, commercial complexes,
industrial complexes and installations
with regard to agriculture. Mediumvoltage electrical installations include
generators, transformers, switchgear,
auxiliary equipment and circuits.
This part of SANS 10142 does not cover
distribution systems operated by licensed
suppliers Eskom and municipalities since
it is deemed that these organisations
traditionally have sufficient expertise and
knowhow to ensure safe and functionally
designed installations. Developers of
security villages, small commercial and
industrial complexes as well as game
farm owners will be affected by the
new requirements since they would
need to appoint designers and installers
who are deemed competent before
undertaking such design, construction
and commissioning work. Developers and
Owners (users) will be advantaged since
TRANSMISSION AND DISTRIBUTION
fruitless expenditure on poor designs may
be prevented and the safety of the MV
installation should improve. This would
positive influence the safety of persons
appointed to perform maintenance work
on such installations.
The new standard iscompulsor y for the
above applications for all new development
and it should be noted that extensions to
existing small medium voltage installations
would also be forming part of the new
requirements. The registered person
(designer) defined as "a person registered
with the Engineering Council of South Africa
(ECSA) and who is competent to perform
work in accordance with this part of
SANS 10142" would be required to inspect
existing MV installations where extensions
are required and submit an opinion on the
safety and functionality of the existing MV
installation. Unsafe installations may need
to be rectified or replaced prior to further
extensions being implemented.
Where does the new standard fit in for
licensed suppliers of electricity?
The new standard, as mentioned
above, is not applicable to Eskom and
municipalities. Other licensed suppliers
of electricity are however bound by the
standard’s requirements in cases where
their supply falls within the scope of the
standard. Individual customers of all
licensed suppliers would however need
to observe the requirements of the new
standard.
The diagram given in Fig. 1 depicts typical
distribution scenarios covered by this
document with specific reference to MV
installations
ECSA’s role with implementation of the
new Standard
The role of the Engineering Council of South
African (ECSA) is to ensure that persons
who are registered in specific categories
are indeed theoretically and technically
sufficiently qualified to ensure that such
Registered persons are competent to
perform the categor y of work. For this
purpose, competency baselines need to
be clearly defined. The baseline simply
refers to a code of professional conduct
which must be followed by the registered
person. The ECSA accepts that the SA
National Standards in several instances
describe the roles of persons when certain
categories of work need to be performed.
A typical example of roles description is
found in SANS 10400 "The application of
the national building regulations".
The Council for the Built Environment ’s
(CBE) aim is to register each special
category of work for registration of persons
i.e. sub-registration within the engineering
discipline ie "substation engineer, structural
engineer, i.e. geo-technical engineer, fire
Fig. 1: Fields of electrical transmission and distribution with specific reference
to the applicability of SANS 10142 Part 2.
engineer etc." Unit standards are typically
generated for specialised categories and
are registered via the SA Qualifications
Authority (SAQA). The ECSA will be informed
regarding the new SANS 10142 Part 2 and
the need for an ECSA code of practice for
MV electrical installations would thereafter
be evaluated.
Technical content of the new standard
and how it should be applied
The standard has been compiled in
such a way that it would be expected
of the registered person to have an
understanding of the respective Legislation,
relevant regulations, codes of practices
and performance standards referenced
in the document. A total of seventy five
SANS standards and eleven IEC standards
are referenced as normative standards
which means that their use is compulsory
when designing and constructing an MV
electrical installation. Included in the
above are nineteen codes of practice
which prescribe the way design and
installation work should be performed. It
is important to note that all cables used
as part of the MV electrical installation
must comply with the compulsory safety
specifications (standards) as issued by
the National Regulator for Compulsor y
Specifications (NRCS) of South Africa and
valid regulator certificates of compliance
(RCC ’s) accompanies the MV and
LV cables (used as part of the power
distribution equipment) i.e. SANS 97,
SANS 1339, SANS 1507 and SANS 1574.
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The technological landscape of power
distribution equipment per formance
capabilities is changing at an extremely
fast pace and performance standards
follow suit. It is therefore imperative for
designers (ultimately consulting engineers)
to keep abreast of new standards and
revisions to existing standards. In a similar
way, Installers who regard themselves
competent to construct and test such
MV installations should have a clear
understanding of the respective codes of
practice for installation work.
The following aspects are covered by the
new Standard:

Compliance with statutory requirements

Electrical design

Mechanical design

Earthing

Buildings and enclosures

Clearance distances

External fences, walls, access doors
and barriers

Climatic and environmental conditions

Electrical protection systems

Audible noise levels

Notices and labeling

Installation of power distribution
equipment

Testing and measurement

Commissioning

Documentation
TRANSMISSION AND DISTRIBUTION
MV Installation Safety Report
Registered person – design, supervision and witness testing
Questions
Equipment of the new, extended or reconstructed installation
20
Protection design and settings
5
Substation design and construction
16
Transformer
1
Earthing
5
Total design related questions
47
Contractor – procurement, installation, testing and commissioning
Questions
Equipment of the new, extended or reconstructed installation
15
Protection design and settings
4
Substation design and construction
12
Transformer
4
Earthing
4
Tests carried out and instruments used
20
Total installation and testing related questions
59
Total positive questions for completion of the installation safety report
106
Table 1: Compulsory compliance for particular elemental design.

Safety measures

Installation safety report
As indicated above, three selected
combinations of documents are to be
used by the designer i.e. Compulsor y
safety legislation, performance standards
and codes of practice, the latter of
which, mainly concentrate on installation
methods. Of particular importance is
Table 1 which specifies compulsor y
compliance for the particular elemental
d e s i g n o r c o m m o d i t y. T h e d e s i g n e r
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(Registered Person) should be capable
to interpret the respective Standards and
be able to evaluate test reports where
type-tests have been per formed on
power distribution equipment. General
acceptance of test certificates must be
TRANSMISSION AND DISTRIBUTION
steered clear from due to insufficient
information normally supplied on crucial
safety and performance characteristics
of the commodity tested.
Fo r s o m e e l e m e n t s o f d e s i g n , t h e
new standard refers the designer to
consult specific legislation, performance
standards and the relevant codes
of practice. It remains the registered
person’s responsibility to have covered all
appropriate engineering design criteria for
the MV electrical installation.
The new standard is quite specific on
minimum safety distances and clearances
which must be observed in during design
and construction. Such distances are
important to prevent accidental contact
when operation and maintenance take
place. Minimum lightning impulse withstand
voltage values ensure that insulation
co-ordination for power distribution
equipment has been established under
operating conditions.
Circuit protection and setting of protection
relays form an important part of the new
standard. Registered persons should have
experience in the field of calculating
protection settings or ensure that a
specialist in this field have performed all
required protection settings and have
certified same in writing.
The requirements for signs, boards and
notices are referred to in a comprehensive
manner with specific instructions for clear
identification and unambiguous marking in
order to avoid incorrect operation, human
error, accidents, etc. during operation
and when maintenance is being carried
out. Signs, boards and notices must be
made of durable and non-corrodible
material and printing shall be in indelible
characters. This requirement will enhance
the safety of MV electrical installations.
Routine testing is an important component
of commissioning and testing which is
fully covered in the new Standard. Testing
requirements of each power distribution
equipment item together with that of
the complete installation ensure that a
safe and functional MV fixed electrical
installation.
Documentation such as type-test reports,
installation, commissioning and testing
instruction manuals with associated
engineering drawings are more than often
missing or not even handed over to the
Customer at completion of the project.
The MV safety installation report will now
ensure that this most important element
is fully complied with.
Knowledge base required by designers
and by contractors to implement the
standard.
The standard is structured in such a way to
guide the designer to consider all safety
and per formance requirements for a
medium voltage electrical installation. In
a similar sense, the standard cannot be
used as a "cook book" with the expectation
to achieve a workable design by a noncompetent person. The exact opposite
can be expected if such attempts are
made. The interrelationship of the one
standard to the next, the technical content
and the level of electrical engineering
expertise called for when applying the
normative standards, are of an advanced
nature. The extent and complexity of
design work cannot be understated if the
number of regulations and performance
standards which the designer must consult
are taken into consideration.
International Standards, which have been
adopted by the SABS and which are
called up in SANS 10142-Part 2, places
SA consulting engineers in a position
to have direct access to a carefully
selected set of documents portraying the
work of experts from all over the world. A
clear understanding, how the respective
standards interlink and complement
each other, should be mastered by every
engineer who is commissioned to design
and commission a medium voltage
electrical installation.
Earthing of electrical installations
(irrespective of its size) is an area often
not fully covered by many designers
and maintenance engineers. This aspect
is addressed in extensive detail by
SANS 10313 which is now a front-end
standard to SANS 63305-3 where a lightning
protection system comprises of an aerial
protections system, a down conductor
system and an earthing termination system.
The Standard requires that a risk analysis
should be performed to determine to
what extent the respective systems would
result in an effective earthing system for
the complete fixed electrical installation.
A recommendation to the SABS standards
approvals committee to adopt the IEEE
80-2000 code of practice for substation
grounding is expected to be supported
and reference to this widely used code
of practice. It is envisaged to include this
document in the new standard.
Introduction of a comprehensive MV
installation safety report
The installation safety report requires
upfront confirmation that the power
distribution equipment as specified,
complies with the applicable standards
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listed in Table 1. This requirement places
extensive responsibility on the Registered
Person to declare that the respective
equipment has in fact been type-tested
and are in compliance with the relevant
Standards. Attention to routine tests
performed on re-conditioned equipment
is also required.
Advantages of the new standard to
improve the safety and performance of
fixed MV electrical installations
SANS 10142-Part 2 will create a new
awareness amongst the power distribution
equipment industry, designers, installers
and ultimately developers/users of the
critical importance of achieving minimum
safety for MV electrical installations.
MV fixed electrical installations falling within
the scope of the new standard in most
cases are not supervised by a qualified
person. From this perspective it is crucial
that the installation’s upfront design and
construction must offer an additional
margin of safety to prevent unexpected
malfunctioning or complete failure.
Operation and maintenance of fixed MV
electrical installations falling within the
scope of the new standard are under
practical situations, seldom performed.
Failures and malfunctioning of equipment
can more easily be prevented or minimised
when robust design, construction and
commissioning testing principles as
specified in the new Standard were
followed.
The area of MV fixed electrical installation
design and construction work has with
the new Standard, been brought into
the public domain and a benchmark
for minimum safety design, construction
and commissioning testing has now
been established. It is foreseen that
SANS 10142 Part-2 will be thoroughly
scrutinised by prospective users and stake
holders and that constructive input will be
received for continual improvement to
serve those best whose lives are at stake
during operation and maintenance as
well as to users who deserve a safe and
durable supply of quality electricity.
References
[1] Occupational Health and Safety Act 1993 (Act
No. 85 of 1993).
[2] SANS 10142-2. The wiring of premises Part 2:
Medium-voltage installations above 1 kV AC not
exceeding 22 kV AC and up to and including
3000 kW installed capacity.
Contact Jaco van Heerden,
TWP Projects, Tel 011 218-3000,
jacovh@twp.co.za 