Standard
Title: LOW-VOLTAGE
RETICULATION SECTION 1:
LOW-VOLTAGE OVERHEAD
RETICULATION
Group Technology
Unique Identifier:
34-953
Part
3 - LV
Area of Applicability:
Distribution Engineering
Documentation Type:
Standard
Revision:
0
Total Pages:
71
Next Review Date:
March 2017
Controlled Disclosure
Disclosure Classification:
Compiled by
Approved by (SCOWT SC Chairperson)
Bruce McLaren
Riaz Asmal
IARC Custodian LV
MV/LV SC Chairperson
Date: 15/03/2012
Date: 16/03/2012
Functional Responsibility (Dx)
Authorized by
Vinod Singh
Prince Moyo
Power Plant Technologies Manager
Power Delivery Engineering GM (Acting)
Date: 22/03/2012
Date: 27/03/2012
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B Morrison / March 2012 / Rev 0
Document Classification: Controlled Disclosure
LOW-VOLTAGE RETICULATION SECTION 1: LOW-VOLTAGE
OVERHEAD RETICULATION
Unique Identifier:
34-953
Revision:
0
Page:
2 of 71
Content
Page
Foreword ............................................................................................................................................... 3
1. Scope ........................................................................................................................................... 4
2. Normative references ................................................................................................................... 6
3. Definitions and abbreviations ....................................................................................................... 7
3.1.
Definitions......................................................................................................................... 7
3.2.
Abbreviations ................................................................................................................... 8
4. Contextual application of the LV standard ................................................................................... 8
4.1.
Reticulation methods ........................................................................................................ 8
4.2.
Layout design options ...................................................................................................... 16
4.3.
Standard Requirements ................................................................................................... 16
4.4.
Clearances ....................................................................................................................... 23
4.5.
Telkom conditions for sharing of services ........................................................................ 25
4.6.
Protection ......................................................................................................................... 26
4.7.
Transformers and surge arresters ................................................................................... 29
4.8.
Earthing installation and tests .......................................................................................... 30
4.9.
Poles and stays ................................................................................................................ 30
4.10. Service connections ......................................................................................................... 31
4.11. Customer installations ...................................................................................................... 31
4.12. Customer metering ........................................................................................................... 32
4.13. Bills of materials (BOM) ................................................................................................... 32
4.14. Power Office ..................................................................................................................... 32
4.15. Marking and labeling ........................................................................................................ 32
5.
Tests and commissioning................................................................................................. 33
5.1.
Electrical tests .................................................................................................................. 33
Annex A – Impact Assessment ............................................................................................................. 34
Annex B - Conductor properties ........................................................................................................... 38
Annex C - Design spans for bare and insulated neutral ABC systems ................................................ 41
Annex D - Design spans for ACSR bare wire systems ........................................................................ 45
Annex E - Design spans for AAAC bare wire systems ......................................................................... 48
Annex F - Urban reticulation ................................................................................................................. 51
Annex G - Minimum separation between parallel LV and HV lines ...................................................... 52
Annex H - List of drawings .................................................................................................................... 55
Annex I - Connector installation practices on low voltage ABC networks ............................................ 60
Annex J - ABC connectors ................................................................................................................... 67
Annex K - National contract for Low Voltage Aerial Bundled Conductor with Insulated
neutral Conductor ................................................................................................................................. 68
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LOW-VOLTAGE RETICULATION SECTION 1: LOW-VOLTAGE
OVERHEAD RETICULATION
Unique Identifier:
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Foreword
Not applicable.
Revision history
This revision cancels and replaces revision no 5 of document no. DISASAAM2.
Date
Rev.
Compiled
By
March 2012
0
B McLaren
Clause
Remarks
Document reviewed and re packed.
Clause no.
Scope changed to exclude pole service box requirements
which are to be included in the services standard Part 8.
Relevant drawings will depict pole service box placement.
Connectors to the LV lines remain in this standard.
Check sheets have been removed due to duplication with
other standards.
Minimum separation between parallel LV and MV lines
now included as an Annex (informative).
Document number changed to DST 34-953.
Feb 2006
5
Document reformatted according to a new template.
Document approved
Dec 2005
4
Expanded to include single-phase and dual-phase and
generally modified for clarity
SABS changed to SANS
SCS Changed to DIS
References updated
Options indicated in fig.4
DT-SAT replaced by R-SAT
Clause 2.4.1: LV ABC updated to cater for both insulated
neutral ABC and bare neutral ABC
Clause 2.4.1.2: LV ABC fittings updated for insulated
neutral
Clause 2.4.1.4: Marking of the insulated neutral highlighted
Clause 2.4.1.9 is updated and fig.6 is included
Clause 2.4.1.10: Shearing of IPC torque shearing nuts
added
Clause 2.4.11 added
Clause2.4.15: Conductor size updated
Clauses 2.5.4, 2.7.6, 2.8.1and 2.8.3 updated
Clause 2.16: DT project replaced by Power Office and
CAD replaced by MicroS
BMS codification removed and standard amendment 1 is
incorporated
April 1997
3
References to service connections standard Part 8
section 1 added
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LOW-VOLTAGE RETICULATION SECTION 1: LOW-VOLTAGE
OVERHEAD RETICULATION
Compiled
By
Unique Identifier:
34-953
Revision:
0
Page:
4 of 71
Date
Rev.
Clause
Remarks
Feb 1996
2
A general improvement to the clarity, content and layout
of rev.1. The minimum ground clearance of 2,5 m for
service connections, stipulated in rev.1, has been
reduced to 2,2 m in rev.2.
June 1995
1
“Original issue – DISASAAM2
Acceptance
This document has been seen and accepted by:
Name
Designation
P Moyo
Power Delivery Engineering GM (Acting)
V Singh
Power Plant Technologies Manager
R Asmal
MV/LV SC Chairperson
This standard shall apply throughout Eskom Holdings Limited, its divisions, subsidiaries and entities
wherein Eskom has a controlling interest.
Development team
This revision was reviewed by;
Bruce McLaren
Rigard Sander
Keywords
Low voltage, Aerial bundled conductor, Overhead, single phase, dual phase, three phase.
Bibliography
The following documents, in addition to those in clause 2, were a source of reference in compiling this
standard. They do not constitute provisions of this standard but are referenced for further information.
NRS 018, Fittings and connectors for LV overhead powerlines using ABC cable.
NRS 018-1:1995, Fittings and connectors for LV overhead powerlines using ABC cable — Part 1:
Strain and suspension fittings for self-supporting ABC.
NRS 018-2:1995, Fittings and connectors for LV overhead powerlines using ABC cable — Part 2:
Strain and suspension fittings for insulated supporting core ABC.
NRS 018-4:1995, Fittings and connectors for LV overhead powerlines using ABC cable — Part 4:
Strain fittings for service cables. (No draft available).
NRS 027:1994, Distribution transformer — Completely self-protecting type.
NRS 034-1:1992, Guidelines for the provision of electrical distribution networks in residential areas —
Part 1: Planning and design of distribution systems : with amendment 1, Financial analysis.
1.
Scope
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OVERHEAD RETICULATION
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The Distribution Standard is a multi-part document whose total structure is defined in Part 0. This part
of the Distribution Standard consists of the following sections under the general title: Low voltage
reticulation:
Section 1: Low-voltage overhead reticulation.
Section 2: Low-voltage underground reticulation.
Section 3: Low-voltage protection philosophy.
Section 4: Low-voltage protection philosophy for low consumption areas.
The intention behind the production of the standard is that all Eskom LV overhead distribution systems
will be built using standard designs as specified in the standard. The standardized materials are
specified in SCSPVAAT6, IARC, Part 9: Buyers Guide.
This section of the Distribution Standard has been prepared to establish specifications for and promote
the use of standardized designs, structures and materials for low-voltage (LV) overhead distribution
systems.
It covers the construction of bare wire and insulated conductor overhead LV reticulation systems using
either wood or concrete poles. These systems are normally fed from MV/LV transformers and are used
to supply individual customers at LV.
The topology includes three overhead low-voltage reticulation methods, namely single-phase (2 wire),
dual-phase (3 wire), and three-phase (4 wire). These methods provide the reticulation designer with
the best known options to achieve cost effective reticulation for most electrification areas in South
Africa.
The three topologies use similar materials and construction techniques. Where appropriate, bare and
insulated systems can be used in combinations of the three topologies to achieve cost effective
reticulation.
Transformers feeding the LV overhead lines are generally pole-mounted (first choice for electrification
and smaller transformers) but ground-mounted units can also be used, where circumstances and size
dictate.
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This standard will be required to change continually as Eskom strives for continual improvements to its
standards. Users of this standard are thus required to establish the appropriate applications, however,
these should comply with the standard requirements set out in this document. Designers should be
cognizant of continuous improvement and standard changes to allow for designs to be frozen at the
desired point in a project to prevent the continual change from interfering with the project and its
associated costs.
The relevant T&Q change control forum enables the local area to cope with continual change to
standards while progressing with projects.
2.
Normative references
The following standards contain provisions that, through reference in the text, constitute provisions of
this standard. At the time of publication, the editions indicated were valid. All standards are subject to
revision, and parties to agreements based on this standard are encouraged to investigate the
possibility of applying the most recent editions of the standards listed below. Information on currently
valid national and international standards may be obtained from the South African Bureau of
Standards. Information on valid Eskom standards and software tools is available from Industrial
Association Resource Centre.
TSI report no. RES/IR/99/00043, “Safety of dwellings under transmission lines”
SANS 10142-1:2009, ED 1.07, The wiring of premises Part 1 :Low voltage installations
SANS 780:2009, ED 4, Distribution transformers.
SANS 10292:2001, Ed1.01, Earthing of low-voltage (LV) distribution systems.
SANS 10198 -14:1996, Ed 2, The selection, handling and installation of electric power cables of rating
not exceeding 33 kV Part 14: Installation of aerial bundled conductor (ABC) cables.
SANS 10280:2010, Ed 1.01, Overhead power lines for conditions prevailing in South Africa.
NRS 043:2005 ED 2, Code of practice for the joint use of structures for power and telecommunication
lines.
NRS 018-2:1995 Ed 1, Fittings and connectors for low voltage overhead power lines using aerial
bundled conductors – Part 1: Strain and suspension fittings for insulated neutral supporting
conductors.
DTC 0106, Specification for concrete poles (reinforced, partially pre-stressed and pre-stressed types).
ESKASAAN0:Rev.1, Standard for the labelling of high voltage equipment. DST 34-1439
SCSAGAAF5:Rev.1, Distribution standard — Part 3: Low-voltage reticulation — Section 3: Lowvoltage protection philosophy.
SCSAGAAH8:Rev.0, Distribution standard — Part 3: Low-voltage reticulation — Section 4: Lowvoltage protection philosophy for low consumption areas.
SCSAGAAI2:Rev.0, Design notes for single- and dual-phase reticulation.
DST 34 – 1985 REV 0, Distribution standard — Part 2: Earthing: Section 1: — MV and LV reticulation
earthing.
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DST34-1270– Distribution Standard - Part 4: Medium Voltage Reticulation: Section 2 – 22 kV
Overhead Reticulation for conductors up to Hare/Oak
SCSASAAS3:Rev.2, Distribution standard — Part 8 Low voltage services: Section 1 - Electrification.
S DST34-4, Distribution standard — Part 9: Buyer’s guide.
DSP34-1803, Aerial bundled conductor with un-insulated (bare) neutral.
DSP34-1647, Specification for wood poles, cross-arms and spacer blocks.
DSP34-343, Specification for oil-immersed power transformers to 500 KVA and 33 kV.
SCSSCAAL4:Rev.2, Fittings for bare neutral aerial bundled conductor.
SCSSCAAO1:Rev.1, Specification for conventional stay planting, percussion stay and rock anchor
installations and compaction testing
DSP34-342 – Specification for phase to phase (11, 22 & 33 kV) connected transformers with centre
tapped low voltage winding.
Occupational Health and Safety ACT, Act 85 of 1993.
TRR/E/96/ELI68, Large single phase motors (TRI Report).
Tools
•
Retic Master / CART
•
Power Office (NACS)
3.
Definitions and abbreviations
3.1.
Definitions
The definitions and abbreviations listed below apply to this document.
Balanced system: A dual- or three-phase system where all phase conductors are carrying a similar
load. The neutral return conductor carries little or no current
LV dual-phase: A 50 Hz a.c. supply at 230 V r.m.s. phase-to-neutral. 460 V r.m.s. phase-to-phase
(180° vector phase displacement). Note the difference to two-phase supply
LV single-phase: A 50 Hz a.c. supply at 230 V r.m.s. phase-to-neutral. The neutral carries the full
load current
LV three-phase: A 50 Hz a.c. supply at 230 V r.m.s. phase-to-neutral; 400 V r.m.s. phase-to-phase
(120° vector phase displacement).
MV phase-to-phase: Any two phases of a three-phase MV supply. An unbalanced three-phase MV
supply. (This is not a recommended method but it is obtained as a result of using two phases of a
three-phase system. It appears here to ensure that it is not confused with dual-phase).
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MV single-phase: A 50 Hz a.c. supply at derived typically from a fully earthed 33 kV system, 19.05
kV r.m.s. phase-to-neutral. The neutral which originates from the source transformer, carries the
residual load current.
MV three-phase: A 50 Hz a.c. supply at 12,7 kV r.m.s. phase-to-neutral; 22 kV r.m.s. phase-to-phase
(120° vector phase displacement).
Single wire earth return: A 50 Hz a.c. supply typically at 19 kV r.m.s. phase-to-earth, where the
return current is through the general body of the earth.
Unbalanced system: A dual- or three-phase system where the phase conductors do not carry a
similar load. The neutral return conductor carries a significant current
3.2.
Abbreviations
ABC: Aerial bundled conductors
SWER: Single wire earth return
LV: Low voltage
4.
Contextual application of the LV standard
4.1.
Reticulation methods
4.1.1.
Introduction
The practice of three-phase MV and LV reticulation is sometimes not the most cost effective method of
electrification. The use of MV philosophies like SWER, single-phase and phase-to-phase systems
combined with LV philosophies like single-phase and dual-phase systems are often more appropriate,
especially when dealing with small, dispersed loads.
This is mainly due to the fact that three-phase conductors may have a power transfer capability greater
than that required by the load and the transformer ratings resulting in the conductors not being fully
utilized.
The main cost advantages of the above methods are
a)
SWER and two-phase MV systems could require shorter poles and/or can provide longer
span lengths than three-phase designs when using the same height poles,
b)
SWER and two-phase MV systems require less pole-dressing equipment,
c)
single-phase and dual-phase transformers are less costly than three-phase units, and
d)
single- and dual-phase LV ABC can be spanned up to 30 % further than three-phase ABC.
e)
reduced maintenance and life cycle costs
There are some possible disadvantages of these methods and these are
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a)
traditional three-phase LV supplies are not available but a three-phase supply can be
created using power electronics. Refer to TRI report TRR/AE/96/ELI68 “Large Single Phase
Motors”,
b)
if there is sufficient motivation to upgrade an area to three-phase supply the customers
would experience outages on these networks to enable the upgrade, and
c)
unbalance could limit transfer capabilities however this is not expected to have an
undesirable effect on electrification projects.
The three-phase, dual-phase and single-phase LV reticulation methods are described in figures 1, 2
and 3.
4.1.2.
Three phase system
3 phase MV
RED
400V
W H IT E
BLU E
NEU T RAL
N +E
L
N
E
DOM ES TIC
S UPP LY
P OINT
Note separate
neutral & earth
in custom ers
dw elling
22 kV/400V (230V ∠ 0°, 230V ∠ 120°, 230V ∠ 240°).
Vector group: Dyn11/Yzn11
Figure 1 — Three-phase LV system
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4.1.3.
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Dual phase system
3 phase
or
ph-ph MV
or
SWER
PHASE 1
+ 230V
- 230V
PHASE 2
NEUTRAL
N+E
L
N
Note separate
neutral & earth
in customers
dwelling
E
DOMESTIC
SUPPLY
POINT
22 kV/460V ( 230V ∠ 180°, 230V
∠ 0° ).
Figure 2 — Dual-phase LV system
4.1.4.
Single-phase system
3 phase
or
ph-ph MV
or
SWER
230V
PHASE
NEUTRAL
N+E
L
N
E
DOMESTIC
SUPPLY
POINT
Note separate
neutral & earth
in customers
dwelling
22 kV/400V ( 230V ∠ 0°)
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Figure 3 — Single-phase LV system
Table 1 — Combinations of MV and LV for various methodologies
1
2
3
4
LV methodology
MV options
Transformer options
LV cable options
Three-phase
Three-phase
50 kVA , 100 kVA &
200kVA
Three-phase
ABC or bare wire
two-wire,
four-wire
three-wire
or
16 kVA single-phase
32 kVA & 64 kVA dualphase
Dual-phase
Single-phase
32 kVA & 64 kVA dualphase for SWER or ph-ph
ABC or bare wire
OR SWER
Three-phase, Ph-Ph
Three-phase or
16 kVA single-phase
ABC or bare wire
ph-ph
4.1.5.
three-wire and two-wire
two-wire
Mixing of technology options
The above topologies provide for the various options available for mixing methods on a particular
project or reticulation system. It is important to mix the methods in a manner that ensures the best
overall electrification solution, for example, due to the marginal difference in cost between two-wire
and three-wire 35 mm² ABC it would not make sense to mix the two if significant cost benefit was not
evident. On the other hand an electrically sound design using a mix of four-wire and two-wire ABC
would generally show significant cost savings.
Also note that the combination of bare wire and ABC systems in a particular transformer zone is
allowed.
These issues shall be discussed with and agreed to by the Regional T&Q.
4.1.6.
Planning factors
Planners and designers should take a medium to long term view when deciding on technology options.
This long term view should be influenced by historical patterns, human settlement dynamics, system
master plans and key MV feeder routes. This doesn’t imply all systems should be 3 phase, however
with judicious thinking, the most appropriate technology should be applied and the “percentage game
plan” should be used to influence planning thinking. From electrification review projects, the
fundamental aspects that influence MV/LV designs long term success are correct scoping and
appropriate customer loading criteria.
If phase-to-phase or SWER MV and dual-phase or single-phase LV provide the right technology fit and
a customer requests a three-phase supply point, designers should consider various options before
changing to three-phase technology, including, does the customer actually need three-phase supply?
In most cases a three-phase supply point is not necessary for the application required. In almost all
cases it is much more cost effective to supply a single-phase point and install a load that will run on
the single-phase supply. For example, single-phase motors up to 7,5 kW are readily available (e.g.
GEC motors). Loads that can be serviced by motors of about 3 kW include
a)
pumps,
b)
commercial and industrial coolers and freezers,
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c)
mortuary rooms,
d)
4-post car hoists, and
e)
miscellaneous garage equipment.
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For motor loads greater than 7,5 kW, written pole and other single-phase motor types are available.
Note that modifications or adjustments to the customer equipment may be required.
4.1.6.1
Load balancing
On both three-phase and dual-phase LV systems, balancing two-phases per node (pole-top box) for
customer connections will result in the minimum number of nodes to achieve load balancing.
This is difficult in practice due to the customer layouts, particularly on rural networks. The Eskom
standard pole-top box (node) is only equipped for connection to a single-phase supply for this reason.
On projects where the balancing of two phases per node is needed two options exist, depending on
the circumstances.
Option (1): Layouts where most nodes will only have enough customer connections for a singlephase connection.
a)
Use a single, standard pole-top box that has a single-phase connection for most nodes.
b)
Use two single pole-top boxes for those nodes that can be balanced on two phases, as
appropriate.
Option (2): Layouts where most nodes can be balanced by using two phases.
Specify the pole-top box for two-phase connections. The specification allows for this option.
The diagrams in figure 4 illustrate the differences between balancing with one or two phases per node:
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OPTION 1
ph1
ph1
ph1
ph2
ph1
ph2
ph2
ph2
ph3
ph3
ph3
ph3
ph3
ph3
ph3
ph3
ph2
ph2
ph2
ph2
ph1
ph1
Balanced three-phase LV phase connection — One phase per node
OPTION 2
ph1
ph1
Ph2
Ph2
Ph2
Ph2
ph3
ph3
Ph3
Ph3
Ph1
Ph1
Balanced three-phase LV phase connection — Two phases per node
OPTION 1
ph1
ph1
ph1
ph1
ph2
ph2
ph2
ph2
ph2
ph2
ph2
ph2
ph1
ph1
ph1
ph1
Balanced dual-phase LV phase connection — One phase per node
OPTION 2
ph1
ph2
ph1
ph2
ph1
ph2
ph1
ph2
ph1
ph1
ph2
ph2
ph1
ph2
ph1
ph2
Balanced dual-phase LV phase connection — Two phases per node
Figure 4 — Load balancing
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ph1
ph1
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The following vector diagrams indicate the different types of networks:
Balanced three-phase LV network with
neutral voltage drop = 0
Three-phase network with only one phase
loaded, equivalent to a single-phase system
or a two-phase LV system with only one
phase loaded
Balanced dual-phase LV network with neutral
voltage drop = 0 (180° between the phases)
NOTE — In all practical situations unbalance will exist giving rise to neutral current. The prime objective is to design for
minimal unbalance. Balancing of a dual-phase system is easier than a three-phase system as only two phases are
under consideration.
Figure 5 — Vector diagrams
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4.1.6.2
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Voltage drop
The power transfer capability ratios of the three-phase, dual phase and the single-phase methods are
as follows:
Three-phase
Dual-phase
Single-phase
6
4
1
This means that the balanced three-phase method is 6 times more efficient in transmitting power than
the single-phase method and the dual-phase method is four times more efficient in transmitting power
than the single-phase method. Use of approved load flow design software e.g. “Reticmaster” will verify
the optimum methodology for any electrification design.
4.1.6.3
Upgrade paths
Eskom has introduced a philosophy into electrification design that requires the networks to be
appropriate for the customer base. This means that a certain amount of information is needed about
the customers in order to design appropriate networks after considering the load for the first 5 years,
then 10 years and 20 years. Planning guidelines in support of the philosophy are obtainable from the
Planning functions in the Operating Divisions. Full advantage needs to be taken of delaying capital
expenditure whilst considering the customer needs. The philosophy thus needs to be supported by an
Upgrade Guideline, the main points of which are indicated in table 2:
Table 2 — Upgrade paths
1
Existing network
Three-phase MV feeding
three-phase LV
2
Reason for upgrade
1 LV voltage drop too high
2 Transformer overload
3 Combination of above
Three-phase MV feeding
single-phase LV
1 LV voltage drop too high
2 Transformer overload
3 Combination of above
Phase-to-phase
feeding
single-phase LV
1 LV voltage drop too high
2 Transformer overload
3 Combination of above
or
SWER
Phase-to-phase or SWER
feeding dual-phase LV
1 LV voltage drop too high
2 Transformer overload
3 Combination of above
3
Upgrade options
1.1 Add extra conductor or increase
conductor size
1.2 Reduce LV line length by extending
MV and adding transformers
2.1 Increase transformer size or create
two transformer areas from one as
above
2.2 Suitable combination of above
1.1 Bare wire-Convert to three-phase or
dual-phase by changing transformer
and adding extra conductor
1.2 ABC-Convert
to
dual-phase
by
changing transformer and adding one
more ABC conductor
2.1 Change transformer
2.2 Suitable combination of above
1.1 Bare wire-Convert to dual-phase by
changing transformer and adding extra
conductor
1.2 ABC-Convert
to
dual-phase
by
changing transformer and adding one
more ABC conductor
2.1 Change transformer
2.2 Suitable combination of above
1.1 Double circuit dual-phase
1.2 Reduce LV line length by extending
MV and adding transformers
2.1 Increase transformer size or create
two transformer areas from one as above
2.2 Suitable combination of above
It is generally not necessary to upgrade phase-phase MV and SWER to three-phase. This situation
may arise in the event of a special load being required. This situation needs to be treated on its
merits.
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The requirements of the Occupational Health and Safety Act, Act 85 of 1993 (OHS Act) and all
subsequent amendments and regulations shall be observed.
Factors of safety shall be as stated in the OHS Act except where exemption has been obtained.
4.2.
Layout design options
Radial LV systems are generally the most economical with conductor sections selected after
optimization utilizing approved design software. There are a number of customer layouts that shall be
considered when doing an electrification design. These can be classified into two main layouts:
4.2.1.
Structured or grid layout
Two acceptable LV reticulation designs for a structured/grid layout are as follows depending on the
circumstances:
a)
between the stands in a block, (mid block) with spurs to poles for street lights where
necessary; and
b)
along the street frontage of the stands.
4.2.2.
Unstructured (informal) or Scattered layouts
The most appropriate reticulation design for this type of layout shall be used. LV layouts will be
dependent on optimum transformer installation positions, accessibility and density of areas.
4.3.
Standard Requirements
4.3.1.
Overhead topologies
The two standard overhead systems to be used by Eskom are:
a)
Aerial bundled conductor (ABC) with un-insulated (bare) neutral and aerial bundled
conductor (ABC) with insulated neutral
b)
ACSR and AAAC bare conductors.
ABC has generally accepted as the preferred option due to its apparent simplicity of construction,
minimal components and its inherent long-term reliability. Recent findings indicate that ABC
installations require specific skills and components applied in the correct manner. A disturbing trend of
the lack of adherence to specific ABC stringing and connection techniques will result in these poorly
constructed installations providing long term operational problems with inherent flaws that will require
difficult fault finding procedures to be implemented. This will impact negatively on safety, performance
resulting in high life cycle costs. Furthermore, LV feeder problems may indicate symptoms similar to
those of transformer overloads, which further exacerbates the aforementioned cycle.
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Factors which support LV ABC installations and related initial capital/project cost benefits are, inter
alia;
•
Lower clearance requirements
•
Lower stringing costs
•
Relatively longer preventative maintenance inspection intervals.
The following myths regarding the safe use of ABC which have developed over time and need to be
exposed.
ABC is a fully insulated system - Bare neutral ABC will become live if broken when connected to load.
Due to the above inherent relaxations, has the potential to become significantly dangerous, particularly
when;
•
Incorrect jointing/connecting/repairing techniques are used.
•
Fuses are bridged/by passed.
•
Incorrect stringing and tensioning techniques are used.
Protection requirements for ABC can be less stringent that for bare wire systems - Due to its makeup,
bare neutral ABC is unlikely to cause protection to operate in the event of a broken phase/neutral
conductor. This can result in live exposed conductor on the ground.
In view of this, Designers, Specifiers, Installers, Operators and Maintainers need to understand their
role, responsibility and accountability in the relevant role of implementing, operating and maintaining
this technology.
Bare wire installations, have the reciprocal factors which impact on initial costs and maintenance
components, however the following issues are considered to be important when considering the use of
bare wire LV.
•
Specific conductor configuration requirement. The neutral shall be the lower/st conductor at
all times.
•
Prospective fault currents and tripping times require faster operation times.
•
Specific stay requirements - conductor tension dependant.
Notwithstanding the above, bare wire systems are simple and easy to operate and maintain as most of
the fundamental components and techniques are used for MV lines.
Eskom has used both insulated neutral ABC systems and bare neutral ABC systems extensively in the
past. Presently bare neutral systems are used for inland (i.e. non corrosive) and insulated neutral
systems for coastal (i.e. corrosive) areas.
The low-voltage ABC shall conform to SCSSCAAD5.
a)
Insulated neutral ABC
In coastal areas, existing bare neutral ABC systems shall be extended using insulated neutral ABC.
The connector used for connection of the insulated neutral ABC to the bare neutral ABC is shown on
D-DT-3039, (Part 9). Note that the connector is coloured white/cream to distinguish it from other
connectors.
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The preferred conductor sizes are:
•
3 × 70 mm² phase conductors + 50 mm² neutral:
three-phase (4 -wire).
•
2 × 70 mm² phase conductors + 50 mm² neutral:
dual phase (2 -wire).
•
3 × 35 mm² phase conductors + 35 mm² neutral :
three-phase (4-wire).
•
2 × 35 mm² phase conductors + 35 mm² neutral :
dual-phase (3-wire).
•
1 × 35 mm² phase conductors + 35 mm² neutral :
single-phase (2-wire).
b)
Bare neutral ABC:
The preferred conductor sizes are:
•
3 × 70 mm² phase conductors + 50 mm² neutral (Bare):
three-phase (4-wire).
•
2 × 70 mm² phase conductors + 50 mm² neutral (Bare):
dual phase (2 -wire).
•
3 × 35 mm² phase conductors + 35 mm² neutral (Bare):
three-phase (4-wire).
•
2 × 35 mm² phase conductors + 35 mm² neutral (Bare):
dual-phase (3-wire).
•
1 × 35 mm² phase conductors + 35 mm² neutral (Bare):
single-phase (2-wire).
LV ABC fittings for bare neutral shall conform to SCSSCAAL4 and for insulated neutral suspension
and strain fittings to NRS 018-2.
LV ABC may allow for auxiliary supplies to street lights, traffic signals and other outlets. Where
specified, auxiliary supplies of this nature are generally taken directly from a phase core. An additional
supply core does enable more control of the apparatus connected to it, for example, control of groups
of streetlights from a set point on the reticulation. The use of the additional auxiliary supply core is not
a specified Eskom standard when using ABC and shall be the exception and not the rule.
Phase cores are identified by indented or embossed numbers 1,2 or 3.
a)
The bare neutral requires no identification as it is bare.
b)
The insulated neutral shall be marked “N” and/or embossed coloured stripe
c)
Single-phase ABC shall have the phase core marked ‘1’.
d)
Dual-phase ABC shall have the phase cores marked ‘1’ and ‘2’.
e)
Three-phase ABC shall have the phase cores marked ‘1’, ‘2’ and ‘3’.
Table 3 — ABC core allocation for different reticulation methods
1
2
3
4
ABC
Marking
Nominal
Nominal
phase-tophase
phase-neutral
voltage
Three-phase
1 = White
voltage
400 V
230 V
N/A
230 V
460 V
+230 V
2 = Blue
3 = Red
Single-phase
1 = White or
Blue or
Red
Dual-phase
1= +VE
2= -VE
-230 V
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2
ABC
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3
Nominal
Nominal
phase-tophase
phase-neutral
voltage
Upgrading
singlephase to dual-phase
(both
conductors
have phase cores
marked 1)
4
Original conductor + ve.
nd
Mark 2 phase conductor,
at each pole, 2-ve using an
aluminium label stuck end
to end around the core.
460V
voltage
+230V
-230V
2-Ve
NOTE — It is possible that LV ABC systems may have to be upgraded in the future to
compensate for unacceptable low voltage levels due to increased loads. Even though each
situation needs to be treated separately some upgrade recommendations, applicable to ABC,
are presented in Table 2. In this unlikely event of upgrading single-phase lines to dual-phase
lines, use an aluminium label as described above to identify the cores.
The service connections shall be distributed between the two or three phases as determined by the
electrical planning function.
The most effective method of LV distribution is usually several radial feeders from each transformer.
Design span and sag tables for LV ABC are given in Annex C.
Clearances applicable to shared Telkom Structures are found in NRS 043. Examples are given on
drawings D-DT-0348 and D-DT-0349. The maximum span that can be tolerated by Telkom shall be
established from Telkom in the area. Accommodation of Telkom maximum spans can be achieved by
doing the following:
a)
MV poles at design span length with a LV pole between to accommodate LV and Telkom
conductors; and
b)
MV or LV poles at the Telkom span length, for example, 60 m.
Additional costs to accommodate Telkom shall be in accordance with the Eskom/Telkom agreement,
specified in NRS 043.
4.3.1.1
Positioning and installation of insulation piercing connectors (IPC’s) and cable ties
Annex I provides detailed information relating to the installation of insulation piercing connectors.
Notwithstanding,
The neutral IPC’s should be positioned closest to the pole and then the phase IPC’s shall follow.
Where a pole-top box and streetlight is fitted on the same pole, the streetlight IPC’s (neutral and line)
shall be put up last i.e. furthest from the pole The same spacing distance as in 1 & 2 above shall be
valid for streetlight IPC’s.
Streetlights are generally maintained from a bucket-truck and therefore distance from the pole is not a
problem.
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The service distribution box and streetlight fitting cables (and thus IPC’s) shall be distributed, as far as
reasonably practicable, evenly on both sides of intermediate and strain poles. This is to assist ease of
maintenance, as it is done from a ladder.
At terminal poles all service distribution box and streetlight fitting cables will be connected to the ABC
on the tension side of the strain clamp.
All IPC’s shall be positioned in such a manner that the tightening bolt is in a vertical position, with the
torque-shear nut on top. This ensures that the grease, enhancing water-tightness, does not run out.
As far as is practically possible the ABC bare neutral conductor should be positioned in such a way
that it does not lie adjacent to the mouth of the phase IPC.
4.3.1.2
Shearing of IPC torque shear nuts
•
Personnel working on ABC networks shall be equipped with a 13-mm tube spanner with Tbar or a 6-sided (hexagon) socket, to be used with a ratchet.
•
NOTE - The performance of the tube spanner or socket is not affected by the temperature of
the IPC and appears to consistently shear the torque shear nut as required.
•
During installation of IPC’s it shall be ensured that the IPC is held securely in order to
prevent it from twisting.
•
A standard 24-sided socket or 13mm spanner shall not be used.
•
Sheared IPC torque shear nuts must be removed from the IPC and the Clerk of Works are to
perform a visual inspection to check that all torque shear nuts are removed.
4.3.1.3
Jointing of ABC neutral after failures(D DT 0300)
The following full tension jointing methods shall be used:
•
compression joint as per Eskom drawing D-DT-0302.
•
automatic line splice that is suitable for the ABC neutral conductor diameter (D DT 3228).
On all bare neutral ABC systems the neutral shall be insulated from the strain clamp to the transformer
connection with a UV protected covering. Refer to D-DT-3127.
All ABC tails or ends shall be sealed using end caps.
The ABC shall be installed in accordance with SANS 0198 part 14.
Only 70 mm ABC aluminium conductors shall be used to connect between the transformer and
the low-voltage fuse units. Where larger power transfer is required appropriately rated ABC shall be
used.
ABC to ABC (refer to D-DT-0314)
a)
Non-tension phase connections on ABC shall be made using a 95/35 - 95/35 IPC in
accordance with D-DT-3039 (Part 9)
b)
Non-tension neutral connections on bare neutral ABC shall be made using either:
1)
a minimum of one H crimp in accordance with D-DT-3019 (Part 9) per
connection; or
2)
two PG clamps in accordance with D-DT-3058 (Part 9) per connection; or
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Non-tension neutral connections on insulated neutral ABC shall be made using two 95/35 95/35 IPC in accordance with D-DT-3039 (Part 9)
ABC to pole top distribution box (refer D-DT- 3039 and 3058)
d)
The ABC shall be connected to the pole-top distribution box using either:
1)
35 - 95/6-25 IPC (refer to D-DT-3039 (Part 9)) for phase connections;
2)
two PG clamps in accordance with D-DT-3058 (Part 9) per neutral connection.
3)
Minimum of one H-crimp (refer to D-DT-3019 (Part 9) for bare neutral ABC
connections;
NOTE — The H-crimp and PG clamp is suitable for aluminium to copper connections only if, with the H-crimp/clamp
vertically positioned, the copper conductor is below the aluminium conductor. The crimp is performed with a tool capable
of exerting at least 10 tons and an ‘0’ die.
4)
2 x 35-95 (PG)/6-25 (IPC’s) (refer to D-DT-3039 (Part 9)) for bare neutral ABC
connections; or
5)
2 x 35 - 95/6-25 IPC’s (refer to D-DT-3039 (Part 9)) for insulated neutral ABC
connections.
e)
All workers performing crimp connections shall be certified as competent to do so by the
project construction manager.
f)
When upgrading ABC systems and when it is necessary to optimize customer connections
on the ABC run, it is better to leave the existing pole-top distribution boxes where they are
and install new ones at more desirable positions. This is to ensure that the ABC remains
sealed against moisture ingress.
g)
The pole top box shall be installed 300 mm below the neutral /earth conductor.
h)
Once an IPC connector has been applied to an ABC phase conductor (or any insulated
conductor) it shall not be removed. The ABC insulation cannot be repaired by the use of
grease and tapes and the ABC conductor and connector are best left as a system. Cut away
phase conductors shall have their ends sealed.
If the connection is in the wrong place leave it where it is and make a new connection at the
desired point.
4.3.2.
Bare LV conductors
As with ABC systems, bare wire systems may be used for all the reticulation methods, i.e. threephase, single-phase, dual-phase and their practical combinations.
The bare wire system has the following benefits; it is
a)
easy to rebalance;
b)
simple to apply and has good reliability; and
c)
easy to fault-find and maintain.
From an initial cost perspective it is suited to rural, low-density application with site conditions that
allow for long spans. It is also appropriate when an easy upgrade path is desired for the area.
a)
a stricter earth to neutral clearance requirement (5,5 m) for bare wire systems;
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b)
more stringent safety requirements for bare wire systems; and
c)
bare wire systems are less forgiving to poor initial installation practice than ABC.
d)
bare wire is more vulnerable to vandalism (wire throwing), however, based on past
experience the occurrence is relatively seldom.
The specific requirements for LV bare wire systems are as follows:
a)
the conductors shall be arranged in a vertical configuration with the neutral conductor always
being closest to the ground i.e. the lowest conductor;
b)
where dedicated street lighting circuits exist which result in the neutral conductor not being
the lowest, suspended earthing devices must be installed;
c)
Connections
1)
Bare wire to bare wire connections may be made with the bolted PG (type) clamps or
other acceptable crimping techniques i.e. the 4-point indent system or H-crimps.
The H-crimp and PG clamp is suitable for aluminium to copper connections only if,
with the H-crimp/clamp vertically positioned, the copper conductor is below the
aluminium conductor. The crimp is performed with a tool capable of exerting at least
10 tons and an ‘0’ die.
2)
Bare wire to insulated conductor connections.
i.
Bare wire (normally ACSR or AAAC) to ABC.
o
A suitably sized PG/IPC connector may be used. (Refer to D-DT-3039,
Part 9).
ii) Bare wire to insulated service box lead
ii.
35-95 / 6-25(IPC). (Refer to D-DT-3039, Part 9)
o
Minimum of one H-crimp (refer to D-DT-3019 (Part 9)
o
PG clamps in accordance with D-DT-3058 (Part 9) per connection.
Except for the H-crimp a single connector is used for the phase and two connectors for the neutral
connections. The H-crimp and PG clamp is suitable for aluminium to copper connections only if, with
the H-crimp/clamp vertically positioned, the copper conductor is below the aluminium conductor. The
crimp is performed with a tool capable of exerting at least 10 tons and an ‘0’ die.
d)
All bolted clamps used for connections shall have non-oxide grease applied.
e)
The pole top box shall be installed 300 mm below the neutral /earth conductor.
f)
The pole top box leads shall be stapled to the pole using double pin clips (Concentric clips)
(refer to D-DT-3111, Part 9). The opening of the pole top service box shall be installed in-line
to the line direction (D- DT0921).
g)
The structure drawing (D DT 0920) shows an eye-nut attached to the neutral hardware. This
is to facilitate the service connection at a higher attachment point and to obviate the need for
additional pigtail bolts.
h)
All nuts that are associated with insulator supports shall have nut retention paint applied.
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i)
All galvanized metal work that is cut on site shall have anti-corrosion treatment applied
immediately i.e. cold galvanizing. This method to be approved prior to execution by the local
Technology and Quality department.
j)
The phase and neutral conductor position on the poles shall be as follows for the single-,
dual- and three-phase methods.
Three-phase
White
Blue
Red
Neutral
Single-phase
Phase (W,B,R)
Neutral
Nil
Nil
Dual-phase
Phase +ve
Phase -ve
Neutral
Nil
NB: Upgrading involves moving conductors to be inline with the above, or redoing the
connections to suit. Pre-energization tests to ensure correct connections are mandatory.
k)
l)
Upgrading
1)
Where conditions allow, poles shall be installed at maximum spacing (100 m to 115 m)
or the project engineer shall decide on maximum spacing using R-SAT. Phase
separators shall be installed for spacing greater than 80m. The spacing shall allow for
future intermediate installations thus the initial spacing shall be in multiples to allow for
final spacing exceeding 40m.
2)
When upgrades occur, additional hardware is installed, conductors are run out, service
boxes are reset and loads are balanced.
3)
With the latest technology developments, more emphasis shall be placed on dualphase LV networks and dual-phase transformers, with upgradeable backbones and
lateral feeders placed as close to the load as possible so as to facilitate the use of
4mm² concentric service cable.
Standard conductors
1)
ACSR : Squirrel, Fox, Mink, Hare.
2)
AAAC : Acacia, Pine, 35, Oak.
m)
Only aluminium conductors shall be connected to low-voltage fuse units.
4.4.
Clearances
The SANS 10280 published during 2010 has different clearance requirements to those published in
the OHS Act. The following table has been taken from SANS 10280.
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Table 4 — Clearance (at maximum sag or swing as applicable)
1
2
3
Highest
system
r.m.s.
voltage
System
nominal
r.m.s.
voltage
kV
kV
<1
7,2
12
24
36
48
72
100
145
245
300
362
420
b
800
d.c.
c
533 kV
4
Safety
Safety
clearance clearance
phase-to- phase-toearth
phase
5
6
7
8
9
Minimum vertical clearances
Minimum
clearances any
direction
m
Roads in
townships,
and
proclaimed
roads,
railways
To telecommunication
lines and
between power
lines
Ground
clearance
10
Minimum
vertical and
horizontal
clearances
m
To buildings,
poles,
structures not
part of power
lines and
vegetation
m
Tower-top
clearances at
maximum insulator
swing and
minimum
clearances at
extreme wind
conductor blowout
m
m
–
6,6
11
22
33
44
66
88
132
220
–
0,15
0,20
0,32
0,43
0,54
0,77
1,00
1,45
2,1
–
0,2
0,3
0,4
0,5
0,61
0,89
1,14
1,68
2,7
4,9
5,5
5,5
5,5
5,5
5,5
5,7
5,9
6,3
7,0
a
6,1
6,2
6,3
6,4
6,5
6,6
6,9
7,1
7,5
8,2
0,6
0,7
0,8
0,9
1,0
1,1
1,4
1,6
2,0
2,7
3,0
3,0
3,0
3,0
3,0
3,0
3,2
3,4
3,8
4,5
0,1
0,1
0,1
0,1
0,1
0,15
0,20
0,24
0,35
0,6
275
330
400
765
2,5
2,9
3,2
5,5
3,6
4,3
4,8
8,9
7,4
7,8
8,1
8,6
9,0
9,3
11,6
3,1
3,5
3,8
6,1
4,9
5,3
5,6
8,5
0,7
0,86
1,0
1,9
–
3,7
–
10,4
8,6
9,8
a
4,3
a
m
a
6,1
NOTE The assumption on which the values are based, is given in C.2.
a
For insulated power lines complying to SANS 1418-1 and SANS 1418-2 (Aerial bundled conductor systems) or SANS 1507-6 (concentric cable)
no minimum safety clearances are required here. The same will apply to technologies for which compulsory SANS safety standards may be developed.
Sag and ground clearances shall be calculated using the conductor operating temperature and this
can be assumed to be 50 °C, unless the operating te mperature is more than this value.
A minimum conductor temperature of 50 °C shall be u sed to determine clearances under conductor
swing conditions. The swing angle shall be that corresponding to 500 Pa of wind pressure. These
separation distances shall apply under all operating and environmental conditions.
ABC with a bare neutral is classified as a fully insulated system, notwithstanding designers are to be
cognizant of risks associated with broken neutrals regardless of the technology, where dangerous
voltages will occur on exposed fallen neutral conductors as well as all customer installations where a
neutral conductor breaks. On method to mitigate against this risk, is to connect all LV feeder neutrals
in the same transformer zone, by means of neutral line interconnectors.
While not normally practicable, unless neutrals are connected to conductive poles which are part of a
meshed neutral systems, the conductive path including footing resistance of conductive poles needs to
be such as to prevent dangerous touch potentials.
Whenever a part of an insulated conductor is bare at the structure (e.g. a bare terminal) then the bare
conductor separation distances shall apply.
Bare conductor clearances above water shall comply with the requirements set out in SANS 10280.
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Telkom conditions for sharing of services
The requirements for the joint use and sharing of structures are set out in NRS 043 which surpasses
this document in terms of hierarchical placement and should always be the main reference in all thing
relating to shared structures.
Relevant excerpts of the specification and set out below.
4.5.1.
Clearances (minimum) for shared services
The minimum attachment spacing between Eskom and Telkom services are listed in table 5.
Table 5 — Attachment spacing
1
2
3
Bare
Insulated
Bare
Insulated
2m
0,9 m
1,2 m
0,9 m
MV
4
LV
The minimum attachment clearance between an insulated power conductor and a Telkom conductor
on the same structure 0,9 m. The separation distance between a power conductor and a separated
Telkom line will be 3m..
There are no restrictions on the Eskom conductor type as specified in this document.
Separation distances at attachment points are between the telecommunication cable and the lowest
attachment point of the power conductor or the lowest attachment point of the service distribution box.
Table 6 lists the minimum Telkom clearances.
Table 6 — Ground clearance of telecommunication cables
1
2
Location of route
Minimum ground
clearance
1)
Across non-electrified railways
6,10
2)
Across any national road
6,50
3)
Across abnormal provincial roads
7,50
4)
Across other provincial roads
6,10*
5)
Across other public roads
6,10
6)
Across streets, roads other than (2), (3), or (4) above, or across privately owned
railway tracks in or near towns
5,50
7)
Across private roads or railway tracks not in or near towns
4,90
8)
Along streets (including midblock), roads or privately owned railway lines in or near
towns.
3,70
9)
Along country roads or railway lines, or over veld or private lands other than (10).
3,00
10) Over cultivated farm lands and across points of entry into cultivated lands.
4,90
* This may be reduced to 5,5 m subject to negotiation with provincial authorities.
Telkom and Eskom service conductors may be hung from the same attachment points on the 4 m/5 m
poles only if no electrical connection points exist on the pole top in question.
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4.5.2.
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Conditions
The clearances in tables 4, 5 and 6 are mandatory and no deviation shall be permitted without the
written agreement of Telkom and the power supply authority.
Earth connection of conductive poles resistance to earth shall be such that the pole does not become
live during an earth fault. No further earthing is required on poles bonded to an LV neutral.
Telkom employees are required to go through a basic training as specified in the Eskom training
course before they can do work on power line structures.
Stay anchors shall be supplied by each authority where they deem it necessary.
All plans for residential areas electrification shall be submitted to Telkom in the prescribed manner .In
view of the time factor involved in the submission and approval of plans it is strongly recommended
that the proposed layout be clearly shown on acceptable plans and discussed with Telkom Regional
representatives in the earliest stage of the project.
Telkom will provide Eskom with a request for any shared circuits.
Eskom should only agree to sharing of circuits if Telkom’s contribution to the shared circuits is greater
than any additional Eskom expenditure to accommodate Telkom.
4.6.
Protection
All protection issues set out in this standard should be applied in conjunction with LV protection
philosophy for low consumption areas, SCSAGAAH8.
CSP transformers are being phased out. Where these occur designers are to take cognizance of and
apply protection requirements applicable to SANS 780 transformers.
The requirements for protection of the low-voltage system are as follows:
The rating of the protective device applied at the transformer LV shall be chosen in order that the
lowest possible phase-to-neutral fault level on an LV distributor will operate the device. In order to
ensure this:
a)
LV ABC distributors protected by CSP type circuit-breakers shall have a minimum phase-toneutral fault level of 2 × the full load rating of the transformer;
b)
LV ABC distributors protected by fuses shall have a minimum phase-to-neutral fault level of
1.6 × the fuse rating i.e. the conventional fusing current of the fuse.
Where this cannot be achieved suitable fuses shall be applied down the line.
On bare wire LV systems the protective device applied at the transformer LV or any point down line
shall ensure that the lowest possible phase-to-neutral fault level within its zone of protection will result
in a protection operating time of less than 100 s.
CSP type transformers have an internal oil immersed circuit-breaker that protects the transformer
against overloading. The circuit-breaker can also provide adequate protection of LV ABC distributors if
the full load rating of the transformer that it protects is less than 70 % of the full load rating of the
conductor.
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Where 100 kVA or 200 kVA CSP transformers supply 35 mm² ABC and 70 mm² ABC this requirement
is not always met, however the circuit-breaker will protect the ABC provided the LV distributor does not
exceed the length specified in table 7:
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Table 7 — Maximum protected lengths of ABC
1
2
3
CSP Transformer
Maximum recommended length
of 35 mm² ABC
Minimum recommended
2
length of 70 mm ABC
100 kVA
250 m
See 2.7.3
200 kVA
Will not protect ABC
170 m
Transformers without internal oil immersed circuit-breakers shall be equipped with external fuses using
the following guidelines:
a)
16 kVA single-phase
1 × 80 A HRC fuse.
b)
32 kVA dual-phase
2 × 80 A HRC fuses.
c)
50 kVA three-phase
3 × 80 A fuses
d)
100 kVA three-phase
3 × 160 A HRC fuses
e)
200 kVA three-phase
2 × 3 × 160 A HRC fuses
The fuses will also provide adequate protection for the LV distributor if the fuse rating is less than the
full load rating of the conductor used for the LV distribution.
Where 100 kVA or 200 kVA transformers with 160 A fuses supply 35 mm² ABC, this requirement is not
met, however the fuse will protect the ABC provided the LV distributor does not exceed the length
specified in table 8:
Table 8 — Maximum protected lengths of ABC
Transformer
Maximum recommended length
of 35 mm² ABC
100 kVA
280 m
200 kVA
290 m
Due to the introduction of split metering and with the view of future smart metering applications, the
pole service box requirements are covered in distribution standard part 8 services. Notwithstanding, to
ensure continuity, both standards shall ensure compatibility in terms of grading and protection
requirements. In view of this as an interim measure, until such time as the relevant protection
standards are revised, the following are to be accepted.
Service cables of the concentric type originate from a pole-top box that is equipped with a 50 A MCB.
This will grade reasonably with the transformer protection and the customer’s installation. Overload
protection of the service cable is provided by the load limiting function of the energy control unit (ECU),
however short circuit protection shall be provided by the protection device in the pole service box, with
the proviso, this protective device will operate before the damage to the concentric cable in the event
of overloading..
Further details regarding the low-voltage protection philosophy are given in SCSAGAAF5 and
SCSAGAAH8.
Previously issued ED’s were equipped with a single-pole isolator. Current ED’s do not have any
protective devices and rely on the protective device in the pole top box for isolation.
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4.7.
Transformers and surge arresters
4.7.1.
Transformers
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Transformers shall comply with the following:
a)
Three phase and single phase transformers shall comply with SCSSCAAH4. Dual phase
transformers shall comply with DISSCAAK7.
b)
The preferred sizes for transformers are 16 kVA (single-phase), 32 and 64 kVA (dual-phase),
50, 100 and 200 kVA (three-phase). The actual size will depend on the ADMD predicted for
the supply area and load platform. The time/overload capacity of the transformer shall be
considered to ensure cost effective design and the full overload capability of the transformer
shall be used in estimating the number of customers / transformers for a specific ADMD.
c)
All transformers shall be earthed in accordance with drawing D-DT-0627 in SCSASAAL9.
d)
The transformer LV connection shall be made in accordance with drawing D-DT-0308 for
CSP units or drawing D-DT-0309 for the SANS 780 type.
The LV earth may be positioned at the transformer (preferred) or one span away on at least two
feeders. The choice will depend on the prevailing circumstances; however the MV and LV earths shall
be at least 5 m apart.
4.7.2.
LV neutral surge arrester
An LV surge arrester shall be placed between the LV neutral bushing and the transformer tank to
protect the transformer during transient fault conditions. The connection shall be in accordance with
D-DT-0308 for CSP transformers and D-DT-0356 for SANS 780 transformers.
4.7.3.
LV connections and jumpers
Pre insulated lugs (DDT 3116) shall be used to connect the jumpers to the transformer
bushings. Where a large number of jumpers are required to be connected to the transformer
bushing but is restricted due to the available bushing thread, either transformer lugs
(DDT3126) or extension connectors can be used. Transformer jumpers between the
transformer phase bushings and the fuse unit shall be made of 70 mm2 ABC. Neutral
conductors are to be brought up from the LV circuit and made off on the neutral bushing using
the above connectors or a bi metallic lug. Copper tinned lugs (D DT 3102) shall be used to
connect the copper earth wire to the neutral bushing to avoid bi-metallic corrosion.
LV fuse unit
The LV fuse units shall be positioned in a way that facilitates ease of operation from ground level using
a link stick with the appropriate attachments. The units shall be placed below the LV conductor and
the position shall also allow for future LV units to be installed where upgrading of the network is
anticipated. The transformer structure drawing D-DT-0309 indicates proposed fuse unit positions for
up to 4 units. Typically, two LV feeders can be fed from one fuse unit.
LV jumpering
The LV jumpering shall be bunched together and neatly routed from the transformer bushings to the
LV fuse units. The ABC shall not be bent in an arc with a radius of less than 200mm so that the entry
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point is not under stress. Sharp bends shall be avoided. In the case of a bare neutral conductor the
neutral shall be covered with LDPE tubing, in accordance with D-DT-3127, from the neutral bushing to
the LV fuse unit. The jumpering shall be routed in such a way that it will not chafe against sharp
objects. Cable ties can also be used to keep the jumpering in position: stainless steel strapping is not
recommended. A separate set of jumpers is required for each fuse unit. The neutral conductor shall
bypass the fuse unit and shall not be broken.
LV feeder take off
The LV feeder shall be located at a position that maintains ground clearance from the transformer and
MV network. To ensure a safe working clearance the fuse unit must be installed a radial distance of
1.1m from the bottom of the transformer tank.
4.8.
Earthing installation and tests
Installation earthing and earth tests shall be carried out in accordance with SANS 10292, and
SCSASAAL9, with particular reference to D-DT-0627 in SCSASAAL9.
4.9.
Poles and stays
Poles may be either wood or concrete. The preference of the local engineering area shall be
established. Concrete and wooden poles of the same height are not inter-changeable without
considering the stresses they can withstand.
Poles shall be selected in accordance with
SCSSCAAO1.
a)
b)
Safety factors
1)
Wood pole structures shall be designed with a safety factor of 2,7 in the case of
suspension structures and 4,5 in the case of strain structures.
2)
Concrete poles are to be designed in accordance with clause 14 of the OHS Act.
Specifications of pole lengths
1)
Wood poles shall comply with SCSSCAAD7. Standard wood pole lengths are 5 m, 7
m, 9m, 10 m, 11 m, 12 m and 13 m.
2)
Concrete poles shall be manufactured in accordance with DTC 0106. The standard
concrete pole lengths are 4 m, 7 m, 9 m, 10 m and 11 m. The design drawings of
standard concrete poles used are given in Annex J.
c)
It can be cost effective for LV, MV, street lighting and telephone services to share poles.
This shall be undertaken whenever practical and appropriate. If MV and LV share the same
structure then a taller pole shall be used with the LV connections at the same height above
the ground as for LV alone. Refer to D-DT-0335 and D-DT-0336 of SCSASAAP2.
d)
Where conductive poles e.g. steel, are used, all conductive parts shall be bonded to the LV
neutral. Concrete poles are considered semi conductive and do not need to be bonded to
the LV neutral:
e)
The planting depths of concrete and wood poles are specified in table 9;
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Table 9 — Planting depths of equivalent concrete and wood poles
1
2
3
4
Concrete poles
5
6
Wooden poles 55 MPa
Length
Strength
Planting depth
m
kN
mm
Length
Pole top
m
Planting depth
mm
mm
4
1
800
5
80
1 000
7
4
1 300
7
120
1 300
9
6
1 500
9
140
1 500
10
8
1 800
10
160
1 800
10 (Trf.)
8
1 800
11(Trf.)
180
1 800
11
8
1 800
11
160
1 800
12
200
2 000
13
200
2 200
NOTE — These are recommended pole sizes. If other sizes are used Distribution Technology shall be consulted.
f)
Planting poles
g)
1)
Pole holes shall be dug in such a way that the longest side of the hole dug for the
pole is parallel to the feeder line, the hole shall be dug so that the width is as narrow
as possible whilst allowing the pole to be planted to the correct depth.
2)
The designer shall determine and include measures to mitigate against the impact of
both overturning and subsidence where poor soil conditions are encountered (stay
plates, lintels, cement to soil mixture).
3)
After a pole has been planted to the required depth, the soil that is to be filled into
the hole shall be slightly damp. If the soil is held in the hand and squeezed, it shall
stay as it was squeezed after opening the hand: that will indicate an optimum
moisture content to ensure good soil compaction.
Compaction
Compaction shall be in accordance with SCSSCAAO1.
h)
Stays may be of the conventional type in accordance with D-DT-0341 or of the percussion
type. An example using the “mule stay” is shown on D-DT-0350 sheet 2. Stay rod
installation is shown on D-DT-0350 sheet 1.
i)
For bare wire systems the designer is to ensure that correctly rated stays are used in
accordance with the conductor type. This implies that 95kN stays are to be deployed for
conductor sizes greater than 50mm2.
4.10.
Service connections
The service connections shall conform to the requirements of DISASAAS3.
4.11.
Customer installations
The customer installations shall conform to the requirements of DISASAAS3.
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4.12.
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Customer metering
The customer metering shall conform to the requirements of DISASAAS3.
Structure drawings for bare wire and ABC overhead reticulation systems and a list thereof, can be
found in annex H.
A separate structure drawing for each reticulation method (single-phase, dual-phase, three-phase), for
bare wire and ABC and for wood and concrete poles is provided.
NOTE — Bare wire lines are constructed on wood poles only.
4.13.
Bills of materials (BOM)
A bill of materials in list form is not provided, however all the materials required are described on each
drawing and are referenced to SCSPVAAT6.
4.14.
Power Office
Power Office will be available from IARC, Simmerpan or the Local Operating Divisions
This tool will be used to provide a complete Bill of Resources for all structure types and conductor
combinations used on a particular project. It will interface with MicroStation systems and the Eskom
Project Management to provide the necessary Bills of Resources.
4.15.
Marking and labeling
4.15.1. Statutory requirements
All controlling apparatus shall be permanently marked or labelled so as to identify the system or part of
the system or the electrical machinery that it controls. Where such control apparatus is accessible from
the front and back, these markings shall be on both the front and the back.
NOTE — Dymotape, masking tape, etc., are not permanent labels and may not be used under any circumstances. The
Local Operating Division labelling requirements are to be established and used for reticulation in that area.
4.15.2. Labelling requirements
All labels shall be permanently and indelibly inscribed and of a size that can be read from ground level
and shall be in accordance with ESKASAAN0.
All labels shall have black letters on a yellow background.
The label size shall be in accordance with the labelling requirements. The material used shall be
durable and resistant to ultraviolet and pollution. Recommended materials are: Iscor Chromodek
0,6 mm (Ref. PO4008 yellow) or aluminium alloy 25 painted with PVF2 yellow.
All lettering/numbering shall be a minimum of 50 mm high. It is recommended that Scotch vinyl decals
(Ref. GSP220) be used.
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The label shall be positioned in such a way that it is:
a)
readable from ground level from the direction that is most logical from an operational
perspective.
b)
not accessible to the public.
Labelling of transformer/s zones
a)
each feeder
b)
LV fuses or circuit-breakers
along the line:
pole-top boxes.
5.
Tests and commissioning
To ensure the safe and reliable operation of a reticulation system the visual inspections and electrical
tests shall be done before and after permanent energizing.
Sample inspection and test sheets are given in annexes F for use by the project resources. The OHS
ACT shall be the minimum requirement for testing and inspection.
5.1.
5.1.1.
Electrical tests
Insulation resistance tests
Disconnect the LV feeders at the transformer. With all pole-top box MCBs switched off use a 1 kV
insulation tester and test between each phase and earth as well as between phases. Care shall be
taken to discharge the ABC before disconnecting the insulation tester leads. Record readings on a
test result sheet (annex H).
Expected results are 1 MΩ or higher between phases and 1 MΩ or higher between phase and neutral.
If the results are below 1 MΩ, corrective action shall be taken.
5.1.2.
Earth resistance tests
These tests shall be done in accordance with SCSASAAL9. These tests shall be done after the
insulation test.
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Annex A – Impact Assessment
(Normative)
Impact assessment form to be completed for all documents.
A1
Guidelines
o
All comments must be completed.
o
Motivate why items are N/A (not applicable)
o
Indicate actions to be taken, persons or organisations responsible for actions and deadline for
action.
o
Change control committees to discuss the impact assessment, and if necessary give feedback
to the compiler of any omissions or errors.
A2
Critical points
A2.1 Importance of this document. E.g. is implementation required due to safety deficiencies,
statutory requirements, technology changes, document revisions, improved service
quality, improved service performance, optimised costs.
Comment:
A2.2 If the document to be released impacts on statutory or legal compliance - this need to be
very clearly stated and so highlighted.
Comment:
A2.3 Impact on stock holding and depletion of existing stock prior to switch over.
Comment:
A2.4 When will new stock be available?
Comment:
A2.5 Has the interchangeability of the product or item been verified - i.e. when it fails is a
straight swop possible with a competitor's product?
Comment:
A2.6 Identify and provide details of other critical (items required for the successful
implementation of this document) points to be considered in the implementation of this
document.
Comment:
A2.7 Provide details of any comments made by the Regions regarding the implementation of
this document.
Comment: (N/A during commenting phase)
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Annex A
(continued)
A3
Implementation timeframe
A3.1 Time period for implementation of requirements.
Comment:
A3.2 Deadline for changeover to new item and personnel to be informed of DX wide changeover.
Comment:
A4
Buyers Guide and Power Office
A4.1 Does the Buyers Guide or Buyers List need updating?
Comment:
A4.2 What Buyer’s Guides or items have been created?
Comment:
A4.3 List all assembly drawing changes that have been revised in conjunction with this
document.
Comment:
A4.4 If the implementation of this document requires assessment by CAP, provide details
under 5
A4.5 Which Power Office packages have been created, modified or removed?
Comment:
A5
CAP / LAP Pre-Qualification Process related impacts
A5.1 Is an ad-hoc re-evaluation of all currently accepted suppliers required as a result of
implementation of this document?
Comment:
A5.2 If NO, provide motivation for issuing this specification before Acceptance Cycle Expiry
date.
Comment:
A5.3 Are ALL suppliers (currently accepted per LAP), aware of the nature of changes
contained in this document?
Comment:
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Annex A
(continued)
A5.4 Is implementation of the provisions of this document required during the current supplier
qualification period?
Comment:
A5.5 If Yes to 5.4, what date has been set for all currently accepted suppliers to comply fully?
Comment:
A5.6 If Yes to 5.4, have all currently accepted suppliers been sent a prior formal notification
informing them of Eskom’s expectations, including the implementation date deadline?
Comment:
A5.7 Can the changes made, potentially impact
material/equipment?
upon the purchase price of the
Comment:
A5.8 Material group(s) affected by specification: (Refer to Pre-Qualification invitation schedule
for list of material groups)
Comment:
A6
Training or communication
A6.1 Is training required?
Comment: (If NO then 6.2 – 6.6 will be N/A)
A6.2 State the level of training required to implement this document. (E.g. awareness training,
practical / on job, module, etc.)
Comment:
A6.3 State designations of personnel that will require training.
Comment:
A6.4 Is the training material available? Identify person responsible for the development of
training material.
Comment:
A6.5 If applicable, provide details of training that will take place. (E.G. sponsor, costs, trainer,
schedule of training, course material availability, training in erection / use of new
equipment, maintenance training, etc).
Comment:
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Annex A
(continued)
A6.6 Was Technical Training Section consulted w.r.t module development process?
Comment:
A6.7 State communications channels to be used to inform target audience.
Comment:
A7
Special tools, equipment, software
A7.1 What special tools, equipment, software, etc will need to be purchased by the Region to
effectively implement?
Comment:
A7.2 Are there stock numbers available for the new equipment?
Comment:
A7.3 What will be the costs of these special tools, equipment, software?
A8
Finances
A8.1 What total costs would the Regions be required to incur in implementing this document?
Identify all cost activities associated with implementation, e.g. labour, training, tooling,
stock, obsolescence
Comment:
……………………………………………………………………………………………………………………….
……………………………………………………………………………………………………………………….
……………………………………………………………………………………………………………………….
Impact assessment completed by:
Name: _________________________________________________________________
Designation: _____________________________________________________________
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Annex B - Conductor properties
Aerial Bundled Conductor (Refer SCSSCAAD5)
ACSR
AAAC
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Annex B
(Continued)
Conductor properties — LV ABC (cater for insulated)
1
2
3
4
5
6
7
8
9
Thickness of dielectric
Conductor
mm (Note 1)
Type of conductor of core
Phase
(aluminum)
Supporting & neutral
(aluminum alloy)
Conductor
size mm2
Number of
wires
Resistance at
20 °C
Diameter of
conductor
Breaking
force
Ω / km max.
mm
N
Min
Max
Min
Average
Min
Max
35
70
7
19
0,868
0,443
6,6
9,3
7,5
10,2
4500
8900
1,3
1,5
1,1
1,3
1,5
1,7
35
7
0,986
6,6
7,5
10300
N/A
N/A
N/A
50
7
0,720
7,7
8,4
14200
N/A
N/A
N/A
NOTE 1 — Columns 8 and 9 show the preferred radials as these are believed to be the most cost effective. Due to the manufacturing technology differences which may exist products
with up to the following radial thicknesses will not be rejected provided that they are within the concentricity requirements described below:
Table of maximum dielectric thicknesses and concentricity
Core (mm2)
Average (mm)
Maximum (mm)
Minimum (,,)
35
1,6
1,8
1,5
70
1,8
2,0
1,5
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Annex B
(Continued)
Conductor properties — ACSR & AAAC
1
2
3
Conductor
Stranding
Copper
Code
Name
and wire dia.
Equiv.
Area
Overall
Dia.
Total
Area
Mass
mm2
mm
mm2
6,35
6,33
mm
4
5
6
7
8
Mechanical properties
9
Coeff.
10
11
Electrical properties
Breaking
Load
Final
Modulus
of linear
expansion
D.C. res.
Rating
@ 20°C
@ 75°C
kg/km
kg
GPa
10-6 / °C
Ω/km
A
24,71
139,7
1893
133,76
13,68
2,707
78
24,48
85,2
818
80,4
19,31
1,3677
110
Table A1 - ACSR (Aluminium Conductor Steel Reinforced) - Extra Strong
Magpie
3/4/2,118
6,65
Table A2 - ACSR (Aluminium Conductor Steel Reinforced
Squirrel
6/1/2,11
12,9
Fox
6/1/2,79
22,58
8,37
42,8
149
1340
80,4
19,31
0,7822
155
Mink
6/1/3,66
38,71
10,98
73,65
257
2230
80,4
19,31
0,4546
215
Hare
6/1/4,72
64,52
14,16
122,48
427
3670
80,4
19,31
0,2733
290
6,24
23,79
65
682
61
23
1,39
110
Table A3 - AAAC (Aluminium Conductor Aluminium Alloy reinforced)
Acacia
7/2,08
13
35
7/2,77
22
8,31
42,18
115
1210
61
23
0,785
155
Pine
7/3,61
38
10,83
71,65
196
2060
61
23
0,462
215
Oak
7/4,65
63
13,95
118,9
325
3400
61
23
0,279
290
Table A4 - Galvanized Steel Wire
¼
1/4,00
–
4
12,57
102
1410
193
11,52
14,67
27
3/3,35
3/3,35
–
7,35
26,44
215
2910
191
11,52
7,4
41
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Annex C - Design spans for bare and insulated neutral ABC systems
THREE PHASE DESIGN SPANS FOR LV ABC 35 mm² CONDUCTOR
Pole
Pole top
Length
dia ( mm )
Nominal
Weight
Wood
Pole
Structures
Suspension
Wood Pole Strain Structures
Max span length Max span length Max span length-1*3 Phase ( m )
Span ( m ) Span ( m ) 1 *3 Phase ( m )
Max span length-2*3 Phase ( m )
2 *3 Phase ( m )
Dev. 30'
Dev. 60'
Dev. 90'
Dev. 30'
Dev. 60'
Dev. 90'
7
0.12
90
210
78
39
210
210
210
210
140
55
7
0.14
90
210
118
59
210
210
210
210
210
210
7
0.16
90
210
168
84
210
210
210
210
210
210
7
0.18
90
210
231
116
210
210
210
210
210
210
9
0.12
100
210
71
36
210
210
210
185
75
*
9
0.14
100
210
108
54
210
210
210
210
210
205
9
0.16
100
210
154
77
210
210
210
210
210
210
9
0.18
100
210
211
105
210
210
210
210
210
210
210
10
0.12
110
210
67
33
210
210
200
140
35
*
10
0.14
110
210
100
50
210
210
210
210
210
130
10
0.16
110
210
143
72
210
210
210
210
210
210
10
0.18
110
210
196
98
210
210
210
210
210
210
10
0.2
110
210
261
130
210
210
210
210
210
210
11
0.12
120
210
62
31
210
215
125
105
*
*
11
0.14
120
210
94
47
210
210
210
210
155
65
11
0.16
120
210
134
67
210
210
210
210
210
210
11
0.18
120
210
183
92
210
210
210
210
210
210
11
0.2
120
210
242
121
210
210
210
210
210
210
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Annex C
(Continued)
THREE PHASE DESIGN SPANS FOR LV ABC 70 mm² CONDUCTOR
Nominal
Weight
Wood
Pole
Structures
Pole
Pole top
Length
dia ( mm ) Span ( m ) Span ( m ) 1 * 3 Phase ( m )
Max span length
Suspension
Wood Pole Strain Structures
Max span length Max span length-1*3 Phase ( m )
Max span length-2*3 Phase ( m )
2 * 3 Phase ( m )
Dev. 30'
Dev. 60'
Dev. 90'
Dev. 30'
Dev. 60'
Dev. 90'
7
7
7
7
0.12
0.14
0.16
0.18
85
85
85
85
120
120
120
120
63
95
136
187
32
48
68
94
120
120
120
120
120
120
120
120
120
120
120
120
120
120
120
120
115
120
120
120
45
120
120
120
9
9
9
9
0.12
0.14
0.16
0.18
100
100
100
100
120
120
120
120
58
87
124
171
29
44
62
85
120
120
120
120
120
120
120
120
120
120
120
120
150
120
120
120
60
120
120
120
*
120
120
120
10
10
10
10
10
0.12
0.14
0.16
0.18
0.2
110
110
110
110
110
120
120
120
120
120
54
81
116
159
211
27
41
58
79
105
120
120
120
120
120
120
120
120
120
120
120
120
120
120
120
115
120
120
120
120
25
120
120
120
120
*
105
120
120
120
11
11
11
11
11
0.12
0.14
0.16
0.18
0.2
120
120
120
120
120
120
120
120
120
120
50
76
108
148
196
25
38
54
74
98
120
120
120
120
120
120
120
120
120
120
120
120
120
120
120
85
120
120
120
120
*
120
120
120
120
*
50
120
120
120
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Annex C
(Continued)
DUAL PHASE DESIGN SPANS FOR LV ABC 35 mm² CONDUCTOR
Wind
Wood Pole Suspension Structures
Pole
Pole top
Length
dia ( mm )
Nominal
Weight
Max span length
Max span length
Wood Pole Strain Structures
Max span length-1*Dual Phase ( m )
Max span length-2*Dual Phase ( m )
Span ( m )
Span ( m )
1 *Dual Phase ( m )
2 * Dual Phase ( m )
Dev. 30'
Dev. 60'
Dev. 90'
Dev. 30'
5
0.08
30
280
58
29
225
220
215
110
5
0.1
30
280
105
52
7
0.12
110
280
103
51
280
280
280
280
7
0.14
110
280
155
78
280
280
280
280
7
0.16
110
280
222
111
280
280
280
280
7
0.18
110
280
305
153
280
280
280
280
9
0.12
125
280
94
47
280
280
280
240
9
0.14
125
280
142
71
280
280
280
280
9
0.16
125
280
203
102
280
280
280
280
9
0.18
125
280
279
139
280
280
280
280
10
0.12
140
280
88
44
280
280
260
185
10
0.14
140
280
133
66
280
280
280
280
10
0.16
140
280
189
95
280
280
280
280
10
0.18
140
280
259
130
280
280
280
280
10
0.2
140
280
344
172
280
280
280
280
11
0.12
150
280
82
41
280
280
165
135
11
0.14
150
280
124
62
280
280
280
280
11
0.16
150
280
177
88
280
280
280
280
11
0.18
150
280
242
121
280
280
280
280
11
0.2
150
280
320
160
280
280
280
280
237
Dev. 60'
105
232
Dev. 90'
100
227
190
280
280
280
70
280
280
280
100
280
280
280
*
270
280
280
45
280
280
280
280
*
170
280
280
280
*
205
280
280
280
*
85
280
280
280
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Annex C
(Continued)
SINGLE PHASE DESIGN SPANS FOR LV ABC 35 mm² CONDUCTOR
Pole
Pole top
Length
dia ( mm )
Nominal
Weight
Span ( m ) Span ( m )
Wood
Pole
Structures
Suspension
Max span length
Max span length
Wood Pole Strain Structures
Max span length-1*1 Phase ( m )
Max span length-2*1 Phase ( m )
1 *1 Phase ( m )
2 * 1 Phase ( m )
Dev. 30'
Dev. 60'
Dev. 90'
Dev. 30'
Dev. 60'
Dev. 90'
5
0.08
50
440
74
37
289
282
276
141
135
128
5
0.1
50
440
135
67
305
298
292
7
0.12
125
440
123
62
440
440
440
395
230
85
7
0.14
125
440
186
93
440
440
440
440
440
440
7
0.16
125
440
266
133
440
440
440
440
440
440
7
0.18
125
440
366
183
440
440
440
440
440
440
9
0.12
140
440
113
57
440
440
440
290
125
*
9
0.14
140
440
170
85
440
440
440
440
440
325
9
0.16
140
440
243
122
440
440
440
440
440
440
9
0.18
140
440
334
167
440
440
440
440
440
440
10
0.12
150
440
105
53
440
440
315
220
55
*
10
0.14
150
440
159
79
440
440
440
440
345
205
10
0.16
150
440
227
113
440
440
440
440
440
440
10
0.18
150
440
311
155
440
440
440
440
440
440
10
0.2
150
440
412
206
440
440
440
440
440
440
11
0.12
160
440
98
49
440
340
200
165
*
*
11
0.14
160
440
148
74
440
440
440
410
245
100
11
0.16
160
440
212
106
440
440
440
440
440
440
11
0.18
160
440
289
145
440
440
440
440
440
440
11
0.2
160
440
384
192
440
440
440
440
440
440
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Annex D - Design spans for ACSR bare wire systems
LOW VOLTAGE DESIGN SPANS - SQUIRREL CONDUCTOR
1
Conductor Description
Angle
2
Weight
Span
3
Nominal Span
8m
9m
10 m
4
Wind Span - Wood Poles
11 m
140m
m
7m
160m
m
180m
m
140m
m
9m
160m
m
180m
m
200m
m
140m
m
10m
160m
m
180m
m
200m
m
140m
m
11m
160m
m
180m
m
200m
m
SINGLE PHASE BARE
WIRE
LV SQUIRREL
DUAL
WIRE
PHASE
0
30
60
90
290
290
290
290
65
65
65
65
105
105
105
105
135
135
135
135
180
180
180
180
265
290
290
290
380
290
290
290
520
290
290
290
240
290
290
290
345
290
290
290
475
290
290
290
630
290
290
290
225
290
290
290
325
290
290
290
445
290
290
290
590
290
290
290
210
290
290
290
300
290
290
290
410
290
290
290
545
290
290
290
0
30
60
90
290
290
290
290
40
40
40
40
100
100
100
100
125
125
125
125
170
170
170
170
180
290
290
290
260
290
290
290
355
290
290
290
165
290
290
290
235
290
290
290
320
290
290
290
430
290
290
290
155
290
290
170
220
290
290
290
300
290
290
290
400
290
290
290
140
290
290
*
200
290
290
290
275
290
290
290
370
290
290
290
0
30
60
90
290
290
290
290
*
*
*
*
85
85
85
85
110
110
110
110
155
155
155
155
140
290
290
290
200
290
290
290
275
290
290
290
125
290
290
15
180
290
290
290
245
290
290
290
330
290
290
290
115
290
200
*
165
290
290
290
230
290
290
290
305
290
290
290
105
290
20
*
155
290
290
200
210
290
290
290
280
290
290
290
BARE
LV SQUIRREL
THREE PHASE BARE
WIRE
LV SQUIRREL
NOTES:
1)
2)
The selected span length is determined by the limiting factors and is the least of the spans given in columns 2, 3 and 4.
Span lengths for the Strain Structure's were calculated assuming that the stays are positioned on the bisector of the conductors
3)
*- exceed design limit
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Annex D
(Continued)
1
Conductor Description
Angle
2
Weight
Span
3
Nominal Span
8m
9m
10 m
LOW VOLTAGE DESIGN SPANS - FOX CONDUCTOR
4
Wind Span - Wood Poles
11 m
140m
m
7m
160m
m
180m
m
140m
m
9m
160m
m
180m
m
200m
m
140m
m
10m
160m
m
180m
m
200m
m
140m
m
11m
160m
m
180m
m
200m
m
SINGLE PHASE BARE
WIRE
LV FOX
DUAL
WIRE
PHASE
0
30
60
90
290
290
290
290
60
60
60
60
105
105
105
105
140
140
140
140
175
175
175
175
200
290
290
290
285
290
290
290
395
290
290
290
180
290
290
290
260
290
290
290
360
290
290
290
475
290
290
290
170
290
290
210
245
290
290
290
335
290
290
290
445
290
290
290
155
290
290
*
225
290
290
290
310
290
290
290
410
290
290
290
0
30
60
90
290
290
290
290
35
35
35
35
95
95
95
95
125
125
125
125
165
165
165
165
135
290
290
125
195
290
290
290
270
290
290
290
125
290
260
*
175
290
290
290
245
290
290
290
325
290
290
290
115
290
100
*
165
290
290
290
225
290
290
290
300
290
290
290
105
290
*
*
150
290
290
30
210
290
290
290
280
290
290
290
0
30
60
90
290
290
290
290
*
*
*
*
75
75
75
75
110
110
110
110
155
155
155
155
105
290
190
*
150
290
290
290
205
290
290
290
95
290
*
*
135
290
290
120
185
290
290
290
245
290
290
290
90
290
*
*
125
290
290
*
175
290
290
290
230
290
290
290
80
185
*
*
115
290
105
*
160
290
290
265
210
290
290
290
BARE
LV FOX
THREE PHASE BARE
WIRE
LV FOX
NOTES:
1)
2)
3)
The selected span length is determined by the limiting factors and is the least of the spans given in columns 2, 3 and 4.
Span lengths for the Strain Structure's were calculated assuming that the stays are positioned on the bisector of the conductors.
*- exceed design limit
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Annex D
(Continued)
LOW VOLTAGE DESIGN SPANS - MINK CONDUCTOR
1
Conductor Description
Angle
2
Weight
Span
3
Nominal Span
8m
9m
10 m
4
Wind Span - Wood Poles
11 m
140m
m
7m
160m
m
180m
m
140m
m
9m
160m
m
180m
m
200m
m
140m
m
10m
160m
m
180m
m
200m
m
140m
m
11m
160m
m
180m
m
200m
m
SINGLE PHASE BARE
WIRE
LV MINK
DUAL
WIRE
PHASE
0
30
60
90
290
290
290
290
55
55
55
55
105
105
105
105
135
135
135
135
170
170
170
170
150
290
290
20
220
290
290
290
300
290
290
290
140
290
210
*
200
290
290
290
275
290
290
290
365
290
290
290
130
290
35
*
185
290
290
280
255
290
290
290
340
290
290
290
120
290
*
*
170
290
290
*
235
290
290
290
310
290
290
290
0
30
60
90
290
290
290
290
35
35
35
35
90
90
90
90
120
120
120
120
160
160
160
160
105
290
*
*
150
290
290
200
205
290
290
290
95
290
*
*
135
290
290
*
185
290
290
290
245
290
290
290
85
230
*
*
125
290
140
*
175
290
290
290
230
290
290
290
80
80
*
*
115
290
*
*
160
290
290
*
210
290
290
290
0
30
60
90
290
290
290
290
*
*
*
*
75
85
85
85
110
110
110
110
150
150
150
150
80
290
*
*
115
290
290
*
155
290
290
290
70
115
*
*
100
290
*
*
140
290
290
85
190
290
290
290
65
20
*
*
95
290
*
*
130
290
290
*
175
290
290
290
60
*
*
*
90
235
*
*
120
290
75
*
160
290
290
155
BARE
LV MINK
THREE PHASE BARE
WIRE
LV MINK
NOTES:
1)
2)
3)
The selected span length is determined by the limiting factors and is the least of the spans given in columns 2, 3 and 4.
Span lengths for the Strain Structure's were calculated assuming that the stays are positioned on the bisector of the conductor
*- exceed design limit
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Unique Identifier:
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Annex E - Design spans for AAAC bare wire systems
1
Conductor Description
Angle
2
Weight
Span
LOW VOLTAGE DESIGN SPANS - ACACIA CONDUCTOR
3
Nominal Span
8 m 9 m 10 m 11 m
4
Wind Span - Wood Poles
7m
9m
10m
11m
140mm 160mm 180mm 140mm 160m 180mm 200mm 140mm 160mm 180mm 200mm 140mm 160mm 180mm 200mm
m
SINGLE PHASE BARE WIRE
LV ACACIA
0
30
60
90
290
290
290
290
65
65
65
65
100
100
100
100
130
130
130
130
180
180
180
180
270
290
290
290
385
290
290
290
530
290
290
290
245
290
290
290
350
290
290
290
480
290
290
290
640
290
290
290
230
290
290
290
330
290
290
290
450
290
290
290
600
290
290
290
210
290
290
290
305
290
290
290
415
290
290
290
550
290
290
290
0
30
60
90
290
290
290
290
35
35
35
35
100
100
100
100
115
115
115
115
165
165
165
165
185
290
290
290
260
290
290
290
360
290
290
290
165
290
290
290
240
290
290
290
329
290
290
290
435
290
290
290
155
290
290
290
225
290
290
290
305
290
290
290
405
290
290
290
145
290
290
290
205
290
290
290
280
290
290
290
375
290
290
290
0
30
60
90
290
290
290
290
*
*
*
*
80
80
80
80
100
100
100
100
150
150
150
150
140
290
290
290
200
290
290
290
275
290
290
290
125
290
290
290
180
290
290
290
250
290
290
290
335
290
290
290
120
290
290
230
170
290
290
290
235
290
290
290
310
290
290
290
110
290
290
25
155
290
290
200
215
290
290
290
285
290
290
290
DUAL PHASE BARE WIRE
LV ACACIA
THREE PHASE BARE WIRE
LV ACACIA
NOTES:
1)
2)
3)
The selected span length is determined by the limiting factors and is the least of the spans given in columns 2, 3 and 4.
Span lengths for the Strain Structure's were calculated assuming that the stays are positioned on the bisector of the conductors.
*- exceed design limit
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Annex E
(Continued)
1
2
Conductor Description
Angle
Weigh
Span
3
LOW VOLTAGE DESIGN SPANS - PINE CONDUCTOR
4
Nominal Span
8 m 9 m 10 m 11 m
Wind Span - Wood Poles
7m
9m
10m
11m
140mm 160mm 180mm 140mm 160m 180mm 200mm 140mm 160mm 180mm 200mm 140mm 160mm 180mm 200mm
m
SINGLE PHASE BARE WIRE
LV PINE
0
30
60
90
290
290
290
290
55
55
55
55
110
110
110
110
140
140
140
140
175
175
175
175
155
290
290
290
220
290
290
290
305
290
290
290
140
290
290
290
200
290
290
290
275
290
290
290
370
290
290
290
130
290
290
290
190
290
290
290
260
290
290
290
345
290
290
290
120
290
290
290
175
290
290
290
240
290
290
290
315
290
290
290
0
30
60
90
290
290
290
290
35
35
35
35
95
95
95
95
125
125
125
125
165
165
165
165
105
290
290
290
150
290
290
290
205
290
290
290
95
290
290
290
135
290
290
290
185
290
290
290
250
290
290
290
90
290
290
290
125
290
290
290
175
290
290
290
235
290
290
290
80
290
290
75
115
290
290
290
160
290
290
290
215
290
290
290
0
30
60
90
290
290
290
290
*
*
*
*
75
75
75
75
115
115
115
115
155
155
155
155
80
290
290
290
115
290
290
290
160
290
290
290
70
290
290
135
105
290
290
290
145
290
290
290
190
290
290
290
65
290
290
*
95
290
290
290
135
290
290
290
180
290
290
290
60
290
125
*
90
290
290
290
120
290
290
290
165
290
290
290
DUAL PHASE BARE WIRE
LV PINE
THREE PHASE BARE WIRE
LV PINE
NOTES:
1)
2)
3)
The selected span length is determined by the limiting factors and is the least of the spans given in columns 2, 3 and 4.
Span lengths for the Strain Structure's were calculated assuming that the stays are positioned on the bisector of the conductors.
*- exceed design limit
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Annex E
(Continued)
1
2
Conductor Description
Angle
Weigh
Span
LOW VOLTAGE DESIGN SPANS - 35 CONDUCTOR
3
4
Nominal Span
8 m 9 m 10 m 11 m
Wind Span - Wood Poles
7m
9m
10m
11m
140mm 160mm 180mm 140mm 160m 180mm 200mm 140mm 160mm 180mm 200mm 140mm 160mm 180mm 200mm
m
SINGLE PHASE BARE WIRE
LV 35 CONDUCTOR
0
30
60
90
290
290
290
290
60
60
60
60
110
110
110
110
140
140
140
140
180
180
180
180
200
290
290
290
290
290
290
290
395
290
290
290
185
290
290
290
265
290
290
290
360
290
290
290
480
290
290
290
170
290
290
290
245
290
290
290
340
290
290
290
450
290
290
290
160
290
290
210
225
290
290
290
310
290
290
290
415
290
290
290
0
30
60
90
290
290
290
290
35
35
35
35
95
95
95
95
130
130
130
130
170
170
170
170
135
290
290
290
195
290
290
290
270
290
290
290
125
290
290
105
180
290
290
290
245
290
290
290
325
290
290
290
115
290
290
*
165
290
290
290
230
290
290
290
305
290
290
290
105
290
290
*
155
290
290
105
210
290
290
290
280
290
290
290
0
30
60
90
290
290
290
290
*
*
*
*
80
80
80
80
115
115
115
115
160
160
160
160
105
290
290
35
150
290
290
290
205
290
290
290
95
290
150
*
135
290
290
290
185
290
290
290
250
290
290
290
90
290
30
*
125
290
290
200
175
290
290
290
230
290
290
290
80
290
*
*
115
290
290
*
160
290
290
290
215
290
290
290
DUAL PHASE BARE WIRE
LV 35 CONDUCTOR
THREE PHASE BARE WIRE
LV 35 CONDUCTOR
NOTES:
1)
2)
3)
The selected span length is determined by the limiting factors and is the least of the spans given in columns 2, 3 and 4.
Span lengths for the Strain Structure's were calculated assuming that the stays are positioned on the bisector of the conductor
*- exceed design limit
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to ensure it is in line with the authorised version on the WEB.
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Annex F - Urban reticulation
Typical mid block design
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Annex G - Minimum separation between parallel LV and HV lines
Earth fault current flowing in HV lines can induce a potentially hazardous voltage on LV lines that run
parallel to the HV lines (refer to TSI report RES/IR/99/00043). HV lines are defined as lines with
voltage greater than or equal to 44 kV. The earthing scheme employed on the HV network will have to
be solid bonding to earth for there to be a problem (resistance earthing would limit the single-phase-toearth fault level to safe levels). It is necessary to ensure that the separation between the parallel HV
and LV lines is sufficient to ensure that the voltage induced on the LV line is not hazardous. The
voltage induced on the LV line is proportional to the length that the two lines run parallel to each other
and to the fault current on the HV line. The greater the separation between the lines, the lower the
induced voltage.
The voltage induced on LV lines due to earth faults on MV lines was not considered in the TSI report,
but it is unlikely to be hazardous because the NECRT in the earth return path of the MV system limits
the MV earth fault current dramatically. Since the voltage induced on the LV system is proportional to
the fault current on the MV system, the voltage induced on the LV system is limited. Problems may
arise where MV and LV lines share structures for a significant distance.
In order to determine whether the proposed LV line route will be safe, split the LV line into line
segments. A line segment starts and ends at a point where the line changes direction or at the
beginning or end of the line. Calculate the voltage induced on each line segment using the following
procedure:
1.
Determine the separation between the HV line and the proposed LV line segment in metres. If
the LV line segment is at an angle to the HV line, use the average separation between the two
lines given by:
Average _ separation =
max imum _ separation − min imum _ separation
2
Where:
minimum separation is the minimum separation between the HV line and the LV line segment in
metres and
maximum separation is the maximum separation between the HV line and the LV line segment in
metres.
Note: Calculations based on an average separation calculated in this manner will not be 100% accurate but will serve to
give a rough estimate of the induced voltage on the LV line segment.
2.
Determine the effective length of the LV line segment in parallel with the HV line. This is given
by:
Effective _ length = LV _ line _ segment _ length × cos(α )
Where:
LV-line-segment-length is the length of the LV line segment and
α is the angle between the HV line and the LV line segment.
α is defined as 0 º when the HV line and LV line segment are parallel to each other and the LV line
segment is heading away from the transformer, 90 º when the HV line and LV line segment are
perpendicular to each other and 180 º when the HV line and LV line segment are parallel to each other
and the LV line segment is heading back towards the transformer.
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Annex G
(Continued)
3.
Determine the prospective single-phase-to-earth fault level of the HV system at the point at
which the HV and LV lines begin their parallel run. This information should be obtained from the
Planning department. The prospective single-phase-to-earth fault level is assumed constant for
the segment of the HV line in question.
4.
Determine the voltage induced on the LV line segment under HV fault conditions. This is given
by:
Induced voltage = k x single-phase-to-earth-fault-level x effective-length x reduction factor
Where:
k depends on the soil resistivity and effective separation and is read from the graph below (extracted
from the TSI report), where p in the graph’s legend is the soil resistivity in ohm.metres.
The reduction factor is read from the table below (based on information extracted from the TSI report):
Shield wires
None
2 x 7/3,35 steel
2 x 19/2,65 steel
Reduction factor
1
0,9
0,8
Now that the induced voltage per LV line segment has been calculated, determine whether the line is
safe. This is done by starting with a voltage of zero volts at the transformer and then adding the
voltage induced on each segment of the LV line to the total voltage in turn, working from the segment
connected to the transformer towards the end of the line. The voltage on segments that form an angle
of greater than 90 º with the HV line (i.e. when the LV line has a component in the direction towards
the transformer) will have a negative sign. The magnitude of the total voltage from the transformer to
the end of any of the line segments shall not exceed 650 V (i.e. –650 V< total voltage < 650 V). This
criterion can be summarised as follows:
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Annex G
(Continued)
N
∑V
n =1
n
≤ 650 VFor all integer N such that 0 < N ≤ the total number of line segments in the line
Where:
n is the line segment number
Vn is the voltage induced on line segment n
If the voltage induced on the LV line between the transformer and the end of any of the line segments
is greater than 650 V then the proposed LV network will have to be redesigned to reduce the voltage
(the 650 V criterion was extracted from the TSI report). This can be done by increasing the separation
between the HV line and LV line and by reducing the number and length of LV line segments that run
parallel to the HV line.
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Annex H - List of drawings
The following drawings form part of this annex:
List of three-phase ABC wood pole drawings
No.
Description
Rev
D-DT-1100
ABC Suspension Assembly 0-30
3
D-DT-1120
LABC Terminal Assembly
4
D-DT-1121
ABC Strain Assembly (0-60°)
5
D-DT-1122
ABC Strain Assembly (60-90°)
4
D-DT-1140
ABC T from Intermediate
4
D-DT-1141
ABC Intermediate Suspension Assembly
4
D-DT-1142
ABC T from Strain
4
D-DT-1143
ABC X Intermediate-Strain Assembly
4
List of three-phase bare wire wood pole drawings
No.
Description
Rev
D-DT-0920
Intermediate Assembly
4
D-DT-0921
In line strain Assembly
4
D-DT-0922
Angle Assembly 1-100°
4
D-DT-0924
Terminal Assembly
4
D-DT-0925
T-off from Intermediate
4
D-DT-0926
Intermediate-Intermediate Crossing
4
D-DT-0927
T-off from strain
4
D-DT-0928
Cable to BW connection
2
D-DT-0929
Service Box connection
4
D-DT-0932
ABC to BW connection
2
D-DT-0934
Intermediate-Strain Crossing
2
D-DT-0935
Strain-Strain Crossing
3
List of dual-phase ABC wood pole drawings
No.
D-DT-1145
D-DT-1146
D-DT-1147
D-DT-1148
D-DT-1149
D-DT-1150
D-DT-1151
D-DT-1152
Description
ABC Suspension Assembly 0-30
LABC Terminal Assembly
ABC Strain Assembly (0-60°)
ABC Strain Assembly (60-90°)
ABC T from Intermediate
ABC Intermediate Suspension Assembly
ABC T from Strain
ABC X Intermediate-Strain Assembly
Rev
0
0
0
0
0
0
0
0
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Annex H
(Continued)
List of dual-phase bare wire wood pole drawings
No.
Description
D-DT-0940
D-DT-0941
D-DT-0942
D-DT-0944
D-DT-0945
D-DT-0946
D-DT-0947
D-DT-0948
D-DT-0949
D-DT-0950
D-DT-0951
D-DT-0952
Intermediate Assembly
In line strain Assembly
Angle Assembly 1-100°
Terminal Assembly
T-off from Intermediate
Intermediate-Intermediate Crossing
T-off from strain
Cable to BW connection
Service Box connection
ABC to BW connection
Intermediate-Strain Crossing
Strain-Strain Crossing
Rev
0
0
0
0
0
0
0
0
0
0
0
0
List of single-phase ABC wood pole drawings
No.
Description
Rev
D-DT-1153
ABC Suspension Assembly 0-30
0
D-DT-1154
ABC Terminal Assembly
0
D-DT-1155
ABC Strain Assembly (0-60°)
0
D-DT-1156
ABC Strain Assembly (60-90°)
0
D-DT-1157
ABC T from Intermediate
0
D-DT-1158
ABC Intermediate Suspension Assembly
0
D-DT-1159
ABC T from Strain
0
D-DT-1160
ABC X Intermediate-Strain Assembly
0
List of single-phase bare wire wood pole drawings
No.
Description
Rev
D-DT-0960
Intermediate Assembly
0
D-DT-0961
In line strain Assembly
0
D-DT-0962
Angle Assembly 1-100°
0
D-DT-0964
Terminal Assembly
0
D-DT-0965
T-off from Intermediate
0
D-DT-0966
Intermediate-Intermediate Crossing
0
D-DT-0967
T-off from strain
0
D-DT-0968
Cable to BW connection
0
D-DT-0969
Service Box connection
0
D-DT-0970
ABC to BW connection
0
D-DT-0971
Intermediate-Strain Crossing
0
D-DT-0972
Strain-Strain Crossing
0
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Annex H
(Continued)
List of three-phase ABC concrete pole drawings
No.
Description
Rev
D-DT-0100
ABC Suspension Assembly 0-30
3
D-DT-0120
ABC Terminal Assembly
4
D-DT-0121
ABC Strain Assembly (0-60°)
5
D-DT-0122
ABC Strain Assembly (60-90°)
4
D-DT-0140
ABC T from Intermediate
4
D-DT-0141
ABC Intermediate Suspension Assembly
4
D-DT-0142
ABC T from Strain
4
D-DT-0143
ABC X Intermediate-Strain Assembly
4
List of single-phase ABC concrete pole drawings
No.
Description
Rev
D-DT-0153
ABC Suspension Assembly 0-30
0
D-DT-0154
ABC Terminal Assembly
0
D-DT-0155
ABC Strain Assembly (0-60°)
0
D-DT-0156
ABC Strain Assembly (60-90°)
0
D-DT-0157
ABC T from Intermediate
0
D-DT-0158
ABC Intermediate Suspension Assembly
0
D-DT-0159
ABC T from Strain
0
D-DT-0160
ABC X Intermediate-Strain Assembly
0
List of dual-phase ABC concrete pole drawings
No.
Description
Rev
D-DT-0145
ABC Suspension Assembly 0-30
0
D-DT-0146
ABC Terminal Assembly
0
D-DT-0147
ABC Strain Assembly (0-60°)
0
D-DT-0148
ABC Strain Assembly (60-90°)
0
D-DT-0149
ABC T from Intermediate
0
D-DT-0150
ABC Intermediate Suspension Assembly
0
D-DT-0151
ABC T from Strain
0
D-DT-0152
ABC X Intermediate-Strain Assembly
0
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Annex H
(Continued)
List of auxiliary drawings
No.
Description
Rev
D-DT-0165
Concrete pole LV stay Assembly
5
D-DT-0166
Stay attaching methods for concrete poles
3
D-DT-0167
Strut Pole for 7m and 9m concrete poles
2
D-DT-0168
Flying stay for concrete poles
2
D-DT-0180
ABC System Service Box Assembly
5
D-DT-0183
Bare wire Service Box Assembly
3
D-DT-0300
ABC full Tension compression Joint
3
D-DT-0302
ABC Full Tension compression Joint - Joining a core
1
D-DT-0305
BN ABC Intermediate Suspension with S/Box - Assembly Detail
6
D-DT-0307
BN ABC -Intermediate Suspension without S/Box - Assembly Detail
2
D-DT-0309
SABS 780 Transformer and LV Fuseholder connections Sheet 1
0
D-DT-0309
SABS 780 Transformer and LV Fuseholder connections Sheet 2
0
D-DT-0309
SABS 780 Transformer and LV Fuseholder connections Sheet 3
0
D-DT-0309
SABS 780 Transformer and LV Fuseholder connections Sheet 4
0
D-DT-0314
LV Barewire Connection Methods
0
D-DT-0315
Stay Assembly details
0
D-DT-0330
Pole Foundation Arrangement
2
D-DT-0332
Pole Planting Depths-Wood and Concrete
2
D-DT-0335
MV and LV Pole Hole Legend
0
D-DT-0336
Woodpole Hole positions
D-DT-0339
Concrete pole orientation layout
0
D-DT-0340
Surge Arrester connections
2
D-DT-0345
Schematic for 160kVA CSP Pole mounted transformer
1
D-DT-0348
Example for Shared Structure Clearances-MV, ABC and Telkom
3
D-DT-0349
Example for shared structure clearances ABC and Telkom
2
D-DT-0350
Sheet 1
Stay rod installation detail
2
D-DT-0350
Sheet 2
Mule stay Rod installation Detail
2
D-DT-0354
Streetlight Assembly
4
D-DT-0356
LV Surge Arrester Installations
2
D-DT-0357
Rock Anchor Installation
2
D-DT-0363
Fourway Pole top box connection detail - Sheet 1
2
D-DT-0363
Fourway Pole top box connection detail - Sheet 2
2
D-DT-0364
Terminal assembly for meter box customer from ABC
2
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Unique Identifier:
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Annex H
(Continued)
No.
Description
Rev
D-DT-0365
Service connection from Con. Intermediate pole
D-DT-0980
MV / LV Bare Wire Staying Methodology
0
D-DT-0981
LV Metering Unit - Sheet 1
0
D-DT-0981
LV Metering Unit - Sheet 2
0
D-DT-0981
LV Metering Unit - Sheet 3
0
D-DT-0981
LV Metering Unit - Sheet 4
0
D-DT-0982
Eye Nut Assembly
0
D-DT-0983
LV Barewire Binding Techniques
0
D-DT-1165
LV Stay Assembly for Woodpoles
D-DT-1167
Strut for 7m and 9m Woodpoles
3
D-DT-1168
Flying Stay Arrangement for Wood Poles
3
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Annex I - Connector installation practices on low voltage ABC networks
BACKGROUND
This bulletin highlights problems that are being created on LV ABC systems as a result of current
practices with regards to the following:
1. The use of cable ties and the positioning of the neutral conductor relative to the IPC’s at service
lead take-off points;
2. The use of a plastic spanners for shearing of IPC torque shear nuts; and
3. Jointing of ABC neutral conductor after failures.
Recommendations are made for future standard practices.
1. Positioning of cable ties, neutral conductor and IPC’s at service lead takeoffs
•
Problem
Eskom drawings D-DT-0305 and D-DT-0306 show two different applications of ABC, IPC’s and cable
ties. In general it appears that the trend in the field is to configure the IPC’s and cable ties according
to D-DT-0306 i.e. to have cable ties positioned before, between and after the IPC’s. This
arrangement results in the ABC conductors and the service distribution box cables being tightly
bunched together. There is also no clear guideline with regards to the minimum spacing required
between the IPC’s, the spacing affects the tightness of the bunched conductors.
A number of ABC failure investigations have highlighted that this practice can lead to the following
types of faults:
•
The ABC bare neutral conductor is pressed into the mouth of the phase conductor IPC which
does not create an immediate fault as the IPC teeth are insulated. Instead it takes a number of
months/years of vibration and movement for the ABC neutral conductor to wear through the IPC
teeth insulation and cause a phase to neutral fault. See photograph 1. The ABC bare neutral
conductor makes contact with only the outer teeth of the IPC resulting in an arcing fault that may
not raise sufficient fault current to operate the upstream fuses however do enough damage to
result in mechanical failure of the neutral conductor. See photograph 2.
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Annex I
(Continued)
Photo 1: ABC bare neutral conductor pressed into phase IPC mouth
Photo 2: Damaged ABC bare neutral conductor adjacent to removed phase IPC
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Annex I
(Continued)
•
The cable tie strapping of the PVC insulated service distribution box cables to the ABC bare
neutral conductor also results in chaffing of the PVC insulation at the cable tie positions to such
an extent that phase to neutral faults are created. An arcing fault is created that may not raise
sufficient fault current to operate the upstream fuses however do enough damage to result in
mechanical failure of the neutral conductor. See photograph 3.
Photo 3: Phase to neutral fault under cable ties resulting in neutral burn off
•
Recommendations
It is recommended that the following guidelines be adopted:
•
IPC’s shall be spaced in the following manner:
1. The two neutral IPC’s are spaced > 100mm and ≤ 200mm apart.
2. The distance between phase IPC’s; and from any phase IPC to a neutral IPC are spaced >
200mm and ≤ 300mm.
3. The neutral IPC’s should be positioned closest to the pole and then the phase IPC’s shall
follow.
4. Where a pole-top box and streetlight is fitted on the same pole, the streetlight IPC’s (neutral
and line) shall be put up last i.e. furthest from the pole The same spacing distance as in 1 &
2 above shall be valid for streetlight IPC’s.
NOTE - Streetlights are generally maintained from a bucket-truck and therefore distance from
the pole is not a problem.
•
The service distribution box and streetlight fitting cables (and thus IPC’s) shall be distributed, as
far as reasonably practicable, evenly on both sides of intermediate and strain poles.
NOTE - This is to assist ease of maintenance, as it is done from a ladder.
•
At terminal poles all service distribution box and streetlight fitting cables will be connected to the
ABC on the tension side of the strain clamp.
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Annex I
(Continued)
•
All IPC’s shall be positioned in such a manner that the tightening bolt is in a vertical position, with
the torque-shear nut on top. This ensures that the grease, enhancing water-tightness, does not
run out.
•
As far as is practically possible the ABC bare neutral conductor should be positioned in such a
way that it does not lie adjacent to the mouth of the phase IPC.
•
Cable Ties are applied in the following manner:
1. The service distribution box neutral cable shall not be cable tied to the ABC.
2. Phase service distribution box cables shall be cable tied, to that specific ABC phase
conductor to which it is connected, only. These cable ties shall be positioned in the centre
point between adjacent phase IPC’s.
3.
No cable ties shall be allowed between the two neutral IPC’s.
4. Cable ties around all phases and neutral conductors of the ABC shall only be used after the
last IPC; at a distance of ≥ 300mm away from the last IPC.
2. Shearing of IPC torque shear nuts
•
Problem
The Eskom buyers guide drawing D-DT-3039 for IPC’s requires the supplier/manufacturer to provide
a plastic hexagonal ring spanner within each package of 12 IPC’s. Field experience has shown that
the ring spanner is incapable of shearing the torque shear nuts on the IPC’s if either the spanner or
IPC become too hot from sunlight exposure. As a result of this there are a number of Electrification
projects where the IPC torque shear nuts have not been sheared and are therefore incorrectly
torqued. The use of a ring spanner also tends to twist the IPC during the shearing process often
resulting in the IPC being badly applied onto the ABC conductor.
A further problem is that it is not standard practice to physically remove the torque shear nut from the
IPC once it has sheared. This makes it impossible for the Clerk of Works to check from the ground
whether the IPC’s are correctly torqued.
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Annex I
(Continued)
•
Recommendation
The following actions are recommended:
•
Personnel working on ABC networks shall be equipped with a 13-mm tube spanner with Tbar or a 6-sided (hexagon) socket, to be used with a ratchet. See photographs 4 and 5.
NOTE - The performance of the tube spanner or socket is not affected by the temperature of
the IPC and appears to consistently shear the torque shear nut as required.
•
During installation of IPC’s it shall be ensured that the IPC is held securely in order to prevent
it from twisting.
•
A standard 24-sided socket or 13mm spanner as shown in photograph 6 shall not be used.
Photo 4: Tube spanner with T-bar used on IPC’s
Photo 5: 6-sided socket.
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Annex I
(Continued)
Photo 6: Standard socket and 13mm spanner.
•
Sheared IPC torque shear nuts must be removed from the IPC and the Clerk of Works are to
perform a visual inspection to check that all torque shear nuts are removed.
3. Jointing of ABC neutral after failures
•
Problem
In order to maintain continuity of supply on ABC networks where the neutral conductor has failed, the
field staff are resorting to the use of two IPC’s and a new section of bare neutral conductor to make
the joint. See photograph 7. This practice is not according to the Eskom drawing D-DT-0302 and is
totally unacceptable as it poses a safety risk to Eskom operational staff as well as the public and is
a contravention of the Occupational Health and Safety Act.
•
Recommendation
The following action is recommended:
•
Any joints made in this manner shall be replaced immediately with a midspan compression joint
as per Eskom drawing D-DT-0302.
•
In areas where there are problems with obtaining the required compression tool it is
recommended that an automatic line splice that is suitable for the ABC neutral conductor
diameter is used. See photograph 8. Further information on this product can be obtained from
Distribution Technology. Staff are to be trained and certified before using the product.
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Annex I
(Continued)
Photo 7: Broken ABC neutral conductor jointed with IPC’s
Photo 8 : Automatic line splice suitable for neutral conductor of 35 to 70 mm2 ABC
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Annex J - ABC connectors
Arial Bundle Conductor networks have a number of connectors for which there is a requirement for standard
tooling and accessories in the field. The tables below intend to cover all connectors for Low voltage arial
bundle conductor systems and give the required information.
Table 1: Connectors for overhead arial bundle conductor
1
Type
2
35-95 mm IPC
Bimetallic clamp
2
Al/Cu 6-25 mm
2
35-95 mm IPC
Bimetallic clamp
2
Al/Cu 35-95 mm
Bare Neutral 35-95
2
mm Bimetallic
clamp Al/Cu 6-25
2
mm IPC
2
35-95 mm IPC
Bimetallic clamp
Bare Neutral Al/Cu
2
35-95 mm
4-15 mm dia.
PG clamp
2
35 mm Bimetallic
lug
2
2
Buyer guide
drawing #
D-DT-3039
T-off to insulated Cu
Torque Wrench
D-DT-3039
T-off to insulated Al
Torque Wrench
D-DT-3039
Bare neutral T-off to
insulated Cu
Torque Wrench
D-DT-3039
T-off to bare neutral Al
Torque Wrench
D-DT-3058
Bare neutral Al to Al
connections
Al bare neutral
connection to Cu
transformer terminal
Torque Wrench
D-DT-3024
35 mm lug
D-DT-3116
35 mm Full
Tension Joint
2
D-DT-3089
1
Type
2
Buyer guide
drawing #
D-DT-3024
2
50 mm Bimetallic
lug
2
70 mm Full
Tension Joint
2
70 mm lug
3
Application
4
Tool
FFG Hydraulic
Compression toolsBurndy Y35, Siemel
C12, Alcon 12A
Al insulated Terminal lug
FFG Hydraulic
Compression toolsBurndy Y35, Simel
C12, Alcon 12A
Mid Span joint
FFG Hydraulic
Compression toolsBurndy Y35, Siemel
C12, Alcon 12A
3
4
Application
Tool
Al bare neutral
connection to Cu
transformer terminal
D-DT-3089
Mid Span joint
D-DT-3116
Al insulated Terminal lug
FFG Hydraulic
Compression toolsBurndy Y35, Simel
C12, Alcon 12A
FFG Hydraulic
Compression toolsBurndy Y35, Simel
C12, Alcon 12A
FFG Hydraulic
Compression toolsBurndy Y35, Simel
C12, Alcon 12A
5
Accessories
Jointing grease
Hex Die
A/F = 17.3 mm
4E173
Hex Die
A/F = 17.3 mm
4E173
Hex Die
A/F = 17.3 mm
4E173
5
Accessories
Hex Die
A/F = 17.3 mm
4E173
Hex Die
A/F = 17.3 mm
4E173
Hex Die
A/F = 17.3 mm
4E173
NOTE
1. PG Clamps are only to be used on Aluminium to Aluminium connections. Bimetallic connections shall not
be made with PG clamps.
2. The bare neutral connection to the pole top box, which is a Copper to Aluminium connection, shall be
made with two IPC 35-95B to 6-25
3. Duplicate connectors are required on the neutral conductor.
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Annex K - National contract for Low Voltage Aerial Bundled Conductor
with Insulated neutral Conductor
1
Introduction
A national contract has been established for Aerial Bundle Conductor (Insulated Neutral). The
contract period is 01 October 2010 to 30 September 2015. The current LAP listing is also updated with
technically acceptable products. Details regarding the contract and the specific items on contract are
provided in this technical bulletin. The List of accepted Products can either be accessed by following
the hyperlink in the IARC website designated as “Accepted Products” or by typing in the web browser’s
address field:
http://hyperwave.eskom.co.za/IARC_LAP
2
Technical Evaluation
2.1
Applicable specifications
The contract enquiry was issued based on the following list of published Distribution specifications and
drawings:
Spec No.
Rev
DSP 34-1803
0
D-DT-3141
10
2.2
Title
AERIAL BUNDLED CONDUCTORS WITH BARE OR INSULATED
NEUTRAL SUPPORTING CONDUCTOR
LOW VOLTAGE AERIAL BUNDLED CONDUCTOR
Items evaluated
The following table list the items evaluated for this Material Group. Some of these items might not be
submitted by the supplier and will therefore not have an acceptance allocated to it.
Buyer’s Guide
Drawing
Item
SAP No
Description
1
0215201
LV-ABC Ins Neutral 1x35 Ph + 54,6 Ins-N (2000m)
D DT 3141
2
0215202
LV-ABC Ins Neutral 2x35 Ph + 54,6 Ins-N (2000m)
D DT 3141
3
0215203
LV-ABC Ins Neutral 3x35 Ph + 54,6 Ins-N (1500m)
D DT 3141
4
0215204
LV-ABC Ins Neutral 2x70 Ph + 54,6 Ins-N (1000m)
D DT 3141
5
0215205
LV-ABC Ins Neutral 3x70 Ph + 54,6 Ins-N (1000m)
D DT 3141
6
0215206
LV-ABC Ins Neutral 3x35 Ph + 1x25 Ph + 54,6 Ins-N (1000m)
D DT 3141
7
0215207
LV-ABC Ins Neutral 3x70 Ph + 1x25 Ph + 54,6 Ins-N (1000m)
D DT 3141
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Annex K
(Continued)
3
Contract details
The contract has been established as a National contract based upon enquiry number Corp-1469.
3.1
Supplier
Contract Dates
Contract No.
Aberdare Cables (Pty) Ltd
01 October 2010 to 30 September
2015
Dx: 4600038543
Wuxi Jiangnan Cable co.Ltd
01 October 2010 to 30 September
2015
Dx: 4600038666
Contract communication
All technical and commercial issues pertaining to the contracts listed below shall be raised with the
following technical, quality and commercial specialists:
Contract Data
TECHNICAL
QUALITY
CONTRACT
MANAGER
3.2
Name
Vinod Singh
Contact No
(011) 629 5086
e-mail address
vinod.singh @eskom.co.za
Name
Andrew Else
Contact No
(011) 629 5137
e-mail address
Andrew.else@eskom.co.za
Name
Kebone Mogase
Contact No
(011) 800 3214
e-mail address
MogaseKK@eskom.co.za
Generic Contract Data
Contract Scope
The manufacture, testing and supply of the estimated quantities of LV ABC
to Eskom’s Distribution division.
Storage
Not included.
Transport & off-loading
TBA
Erection & Installation
Not included.
Commissioning
Not included.
Training
Not included.
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Annex K
(Continued)
3.3
Contract Data
The following tables summarises the contact data for each affected supplier.
Contract Data
Aberdare Cables (Pty) Ltd
Contract No
4600038543
Contract Date
01 October 2010
Valid until
30 September 2015
Supplier Details
Refer to clause 3 above
Warrantee Periods
Fifty two (52) weeks after Delivery of each Purchase Order
Designed work life
25 years from the end of the warranty period of each purchase order
Product lead times
Delivery lead time is 4 weeks but the date on the purchase order will take
precedence
Special conditions
Refer to the Goods Information on the contract documentation page 13.
Tools and spares
As per Distribution specification DSP_34-1803 Rev 0
Contract Data
Wuxi Jiangnan Cable co.Ltd
Contract No
4600038666
Contract Date
01 October 2010
Valid until
30 September 2015
Supplier Details
Refer to clause 3 above
Warrantee Periods
Fifty two (52) weeks after Delivery of each Purchase Order
Designed work life
25 years from the end of the warranty period of each purchase order
Product lead times
Delivery lead time is 5 to 8 weeks but the date on the purchase order will
take precedence.
Special conditions
Refer to the Goods Information on the contract documentation page 13.
Tools and spares
As per Distribution specification DSP_34-1803 Rev 0
4
4.1
4.1.1
Supplier details
SUPPLIER:
Aberdare Cables (Pty) Ltd
MANUFACTURER
Aberdare Cables (Pty) Ltd
Nominated Contact Persons:
Contact Person:
Tel No:
Fax No:
Cell No:
e-mail:
Frank Rook
+27 11 396 8000
+27 11 396 8012
+27 82 895 4877
frooke@aberdare.co.za
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Annex K
(Continued)
4.2
4.2.1
SUPPLIER:
Wuxi Jiangnan Cable co.Ltd
MANUFACTURER
Wuxi Jiangnan Cable co.Ltd
Nominated Contact Persons:
Contact Person:
Tel No:
Fax No:
Cell No:
e-mail:
5
Tony Dong
+27 11 493 1863
+27 11 493 3167
+27 83 4610588
tdong@global.co.za
Product Acceptance
The following tables list only the items and their associated products codes for which the supplier
obtained technical and quality acceptance:
5.1
Aberdare Cables (Pty) Ltd
Item
SAP No
Description
1
2
3
4
5
0215201
0215202
0215203
0215204
0215205
6
0215206
7
0215207
LV-ABC Ins Neutral 1x35 Ph + 54,6 Ins-N (2000m)
LV-ABC Ins Neutral 2x35 Ph + 54,6 Ins-N (2000m)
LV-ABC Ins Neutral 3x35 Ph + 54,6 Ins-N (1500m)
LV-ABC Ins Neutral 2x70 Ph + 54,6 Ins-N (1000m)
LV-ABC Ins Neutral 3x70 Ph + 54,6 Ins-N (1000m)
LV-ABC Ins Neutral 3x35 Ph + 1x25 Ph + 54,6 Ins-N
(1000m)
LV-ABC Ins Neutral 3x70 Ph + 1x25 Ph + 54,6 Ins-N
(1000m)
5.2
Product Code
Wuxi Jiangnan Cable co.Ltd
Item
SAP No
Description
1
2
3
4
5
0215201
0215202
0215203
0215204
0215205
6
0215206
7
0215207
LV-ABC Ins Neutral 1x35 Ph + 54,6 Ins-N (2000m)
LV-ABC Ins Neutral 2x35 Ph + 54,6 Ins-N (2000m)
LV-ABC Ins Neutral 3x35 Ph + 54,6 Ins-N (1500m)
LV-ABC Ins Neutral 2x70 Ph + 54,6 Ins-N (1000m)
LV-ABC Ins Neutral 3x70 Ph + 54,6 Ins-N (1000m)
LV-ABC Ins Neutral 3x35 Ph + 1x25 Ph + 54,6 Ins-N
(1000m)
LV-ABC Ins Neutral 3x70 Ph + 1x25 Ph + 54,6 Ins-N
(1000m)
Product Code
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