TRANSMISSION CONSTRUCTION STANDARD
TCS-P-104.03, Rev. 0
TABLE OF CONTENTS
1.0
SCOPE
2.0
GENERAL REQUIREMENTS
3.0
SAFETY REQUIREMENTS
3.1
3.2
3.3
3.4
3.5
3.6
3.7
3.8
4.0
MATERIALS
4.1
4.2
4.3
5.0
Materials for Backfill
Materials for Pavements
Sand or Special Backfill
EXECUTION
5.1
5.2
5.3
5.4
5.5
5.6
5.7
5.8
6.0
Safety Rules and Regulations
Shoring or Bracing
Roads and Highways
Residential Gateways
Restricted Areas
Housekeeping
Signboards
Clearance from Underground Utilities
Excavation
Protection of Underground Construction
De-watering
Compaction
Restoration
Repair Work
Field Quality Control
Completion
CABLE DUCTS REQUIREMENTS
6.1
6.2
6.3
6.4
6.5
6.6
6.7
General Requirements
Specific Requirements
Installation
Reinforced Concrete Cable Trench
Conduit Hangers or Spacers
End Bells
Duct Sealing Requirements
TCSP10403R0/YM
Date of Approval: June 25, 2008
PAGE NO. 2 OF 30
TRANSMISSION CONSTRUCTION STANDARD
TCS-P-104.03, Rev. 0
LIST OF FIGURES
FIGURE 1:
Minimum Trench Dimensions and Amount of Backfill Required to
Reduce Soil Thermal Resistivity to an Average Value of 120°C
cm/W (Typical).
FIGURE 2:
Restoration of Asphalt Pavement at Trenching Crossings
FIGURE 3:
Typical Conduit Hangers or Spacers
FIGURE 4:
Typical End-Bell
TCSP10403R0/YM
Date of Approval: June 25, 2008
PAGE NO. 3 OF 30
TRANSMISSION CONSTRUCTION STANDARD
1.0
TCS-P-104.03, Rev. 0
SCOPE
This standard sets forth the construction requirements for cable trenches and cable
ducts including protection, support, maintenance and reconstruction of existing
utility facilities affected by such construction in the 69 kV and above transmission
system of Saudi Electricity Company, (SEC).
This Standard does not cover Thrust Boring Pipes and Horizontal Directional
Drilling.
2.0
GENERAL REQUIREMENTS
High voltage underground cable circuits shall be installed directly buried, in ducts,
in underground vaults or in a combination of these. In addition to meeting the
physical requirements of the trenches and duct installations, all necessary
precautions to insure the safety of personnel working in the trenches and the
safety of the general public must be ascertained.
All backfilling and restoration work of the cable trenches and ducts shall be
performed in a manner, which will not damage the cable installation. The
replacement of all backfilling material and final restoration shall be equal to or
better than the original condition that existed prior to the trenching operation.
3.0
SAFETY REQUIREMENTS
3.1
Safety Rules and Regulations
The construction of cable trenches and ducts shall conform to the rules and
regulations pertaining to safety established by the concerned Government
agencies, Municipalities, concerned companies and SEC Accident
Prevention and Construction Safety Manuals.
3.2
Shoring or Bracing
Where cable trenches and ducts are excavated to a depth of 0.90 meter or
more, shoring or bracing shall be installed to prevent cave-ins of unstable
soil and to prevent rock debris falling from top and walls of the trench.
Where the trench walls are sloped at a 35o angle or less from horizontal,
shoring or bracing may be omitted.
3.3
Roads and Highways
Where cable trenches and ducts cross or are in close proximity to vehicular
traffic roads and highways, all necessary barriers, steel plates, warning
lights and signs shall be installed to protect the general public from any
hazards associated with the open trenches.
TCSP10403R0/YM
Date of Approval: June 25, 2008
PAGE NO. 4 OF 30
TRANSMISSION CONSTRUCTION STANDARD
3.4
TCS-P-104.03, Rev. 0
Residential Gateways
Where cable trenches and ducts block residential gateways, stable and safe
bridges shall be provided with all necessary barriers.
3.5
Restricted Areas
In restricted areas, the work shall be carried out under the Work Permit
Procedure and as per the right-of-way approval and conditions.
Mechanized trenching equipment are prohibited in areas within the
proximity of energized cables, flammable liquids/gas pipelines, up to 1.5
meters outside substations where grounding grid is present and under
overhead transmission lines.
3.6
Housekeeping
Good housekeeping shall be strictly observed. Materials/equipment being
used shall be arranged so as not to cause obstruction to traffic or to the
public.
3.7
Signboards
The contractor shall provide cable trenching signboards on every
trench/road crossing and 200 meters on straight run.
(The contractor may consult the drawing # SB-036883 as an example of a
typical case).
3.8
Clearance from Underground Utilities
It is a requirement to take clearance for excavation on designated cable
routes from all Underground Utilities like Water, Telephone etc.
4.0
MATERIALS
4.1
Materials for Backfill
4.1.1
Backfill materials shall be as per the requirements of TCS-Q113.02.
4.1.2
Maximum particle size shall be 50 mm at its greatest dimension.
4.1.3
No organic materials, debris or other deleterious materials shall
be permitted.
TCSP10403R0/YM
Date of Approval: June 25, 2008
PAGE NO. 5 OF 30
TRANSMISSION CONSTRUCTION STANDARD
4.2
TCS-P-104.03, Rev. 0
Materials for Pavements
4.2.1
Asphalt concrete shall be hot-mixed and shall be as per the
requirements of TCS-Q-113.01.
4.2.2
Physical Requirements
The physical requirements for Asphalt concrete shall be as per the
SEC Standard TCS-Q-113.01.
4.2.3
Prime Coat and Tack Coat Materials
Prime Coat and Tack Coat Materials shall be as per the
requirements of the SEC Standard TCS-Q-113.01. The type and
the rates of application are as specified in TCS-Q-113.01.
4.2.4
TCSP10403R0/YM
Marl Bases
a.
Marl bases shall be uniformly graded with material passing
the 100 mm sieve and less than 15 percent passing the 75 µm
sieve and as specified in the SEC Standard TCS-Q-113.02.
b.
The soaked California Bearing Ratio (CBR) of the Marl as
determined by ASTM D1883 at the optimum moisture
content for maximum dry density using ASTM D1557,
Procedure C, shall not be less than 50 for base material and
not less than 15 for subbase material. Marl shall be sampled,
tested by independent testing laboratory and approved by
SEC.
c.
When work falls within the jurisdiction of Ministry of
Transportation, Municipality and/or other government
agencies, the materials and methods used shall also conform
to the Specifications of Ministry of Transportation and/or
Municipality.
Date of Approval: June 25, 2008
PAGE NO. 6 OF 30
TRANSMISSION CONSTRUCTION STANDARD
4.3
TCS-P-104.03, Rev. 0
Sand or Special Backfill
4.3.1
To improve heat dissipation and to provide protective mechanical
cushion around the cables, clean quartz sand or special backfill
shall be used around cables or ducts. This quartz sand or special
backfill, also called as “thermal sand backfill” has special
characteristics and the supplier shall provide all the required
information and test reports for SEC review and approval.
4.3.2
The clean sand to be furnished shall conform to SEC Standards
TCS-Q-113.02, along with the following requirements:
4.3.3
a.
The sand may contain clay or Marl in an amount not more
than 3%.
b.
Random samples shall be taken under the supervision of SEC
and shall be tested by an independent testing laboratory
approved by SEC. The sample shall be from each 25 m3 or
portion thereof loaded during a day's shipment. A suitable
size sample shall then be obtained for a clay test and standard
sieve analysis.
c.
Samples for moisture content tests shall be taken from each
day's shipment. Moisture content shall be determined before
and after drying. Certified results of all these tests shall be
forwarded to the SEC within one week indicating loading
dates.
The Thermal Resistivity characteristics of the sand shall comply
with the values as given in the table below.
Max. Thermal
Resistivity
(oC cm/W)
Minimum
Density
(kN/m3)
Minimum
Specific
Gravity
Sandy Soil (Dry)
120
14.75
1.46
Sandy Soil (Wet)
50
18.50
1.86
Materials
TCSP10403R0/YM
Date of Approval: June 25, 2008
PAGE NO. 7 OF 30
TRANSMISSION CONSTRUCTION STANDARD
5.0
TCS-P-104.03, Rev. 0
4.3.4
The minimum trench dimension around a pipe or cable to reduce
the soil thermal resistivity to an average value of 1200C cm/W
shall be determined from Figure-1.
4.3.5
Irrespective of field conditions encountered, the installation shall
be controlled by the "Dry" backfill condition parameters as given
in the table under clause 4.3.3.
4.3.6
SEC shall be provided with daily logs covering the pertinent field
excavation conditions.
EXECUTION
5.1
Excavation
5.1.1
Excavation shall be sheeted, braced and shored, as necessary, to
prevent caving-in or sliding, and to provide protection for existing
structures and facilities. Sheeting, bracing and shoring shall be
designed and built to withstand all loads caused by any earth
movement or pressure and shall be rigid, maintaining shape and
position under all circumstances.
5.1.2
Bottoms of excavations shall be firm, level, smooth and free of
loose earth, soft/loose sand, mud, gravel, rocks and debris. Any
soft spots shall be compacted per TCS-Q-113.02 requirements. In
case of sabkhah and high water table areas, a minimum of 150
mm layer of sand bedding shall be provided and compacted per
TCS-Q-113.02.
5.1.3
Soil and wastes from excavation shall be disposed-off properly to
a municipality designated dumping area.
5.1.4
Excavations shall not be done below the bottom level of adjacent
existing foundations unless underpinning and shoring has been
done after approval by SEC.
5.1.5
Sides of unshored excavation shall be sloped back to the angle of
natural repose of the soil to avoid sliding or caving. The angle of
repose shall be the angle of internal friction for the material.
5.1.6
Construction materials or heavy machinery shall not be placed
near the top of excavations or slopes within twice the depth of the
excavation.
TCSP10403R0/YM
Date of Approval: June 25, 2008
PAGE NO. 8 OF 30
TRANSMISSION CONSTRUCTION STANDARD
TCS-P-104.03, Rev. 0
5.1.7
Where excavated trench blocks the access of municipality
watering trucks to trees/grass, the trees/grass shall be watered and
maintained in accordance with the Municipality requirements.
Any repairs, fines and damages during execution shall be at no
cost to SEC. Pedestrians and traffic guide/signs shall be placed for
a clear passage.
5.1.8
All repairs of damages to the existing underground and/or
overhead facilities shall be at no cost to SEC.
5.1.9
Precautions shall be taken to maintain the condition of the
trenches prior to the installation of the cables. Maintenance shall
include prevention of cave-ins or sloughing of the trench walls,
de-watering of the trenches and putting barriers for vehicles or
cable laying equipment.
5.1.10 Excavations shall be done by observing continuity of traffic flow
per latest revision of Ministry of Transportation, Traffic Control
Guide on Work Area and shall follow Traffic Police Department
requirements as per Work Permit issued.
5.1.11 Sidewalks for use by the public during excavations shall be
protected by guardrails or fences.
5.1.12 Structures/Equipment adjacent to excavations shall be braced to
prevent settlement and lateral movement.
5.1.13
5.2
At SEC facilities where grounding grid is provided, care shall be
taken to avoid cutting. If cutting is unavoidable, it shall be done
after providing temporary grounding conductor under SEC
supervision. Permanent joint shall be provided and filling shall be
done only after approval by company representative.
Protection of Underground Construction
5.2.1
TCSP10403R0/YM
Underground facilities and other underground construction, which
may be uncovered or otherwise affected by the work shall be
located, protected, shored, braced, supported, and maintained. The
facilities shall be exposed either by hand tools or methods
acceptable to the respective Ministry/Utility Departments. All
protective covers, warning tapes, position markers, etc.,
pertaining to existing underground utilities shall be preserved
during excavation and shall be restored in position during the
backfilling phase of the cable trenches.
Date of Approval: June 25, 2008
PAGE NO. 9 OF 30
TRANSMISSION CONSTRUCTION STANDARD
TCS-P-104.03, Rev. 0
5.2.2
If existing active utility lines are encountered and get damaged,
all steps necessary to report damage(s) to concerned authority for
immediate repair shall be done. No utility damage shall be
repaired unless otherwise authorized by the concerned
Ministry/Utility Departments. If existing utilities are found to
interfere with the construction operations, SEC shall be
immediately notified in writing, requesting instructions. Work
shall not proceed until written instructions from SEC are received.
5.2.3
When utility lines that are not made known or indicated, are
encountered within the area of operations, the concerned
Ministry/Utility Departments shall be notified immediately about
their presence for necessary measures to be taken to prevent
interruption of the service, where service is to be maintained.
5.2.4
During the tie-in phases, utilities to adjacent buildings may be
affected. In such cases, the work shall be coordinated through the
concerned Ministry/Utility Departments and SEC, so that
interruption of utilities will be minimal or eliminated altogether.
5.2.5
During all operations, the access to residences and buildings shall
remain fully functional. Supports, covers, trench crossing means,
services connections, etc., shal1 be provided as necessary to
maintain functions within the existing residences, industries and
other buildings uninterrupted, and to the satisfaction of SEC.
5.2.6
Open excavations shall be barricaded and warning lights shall be
installed. Warning lights shall operate from sunset to sunrise each
day or as required by the Municipality and Traffic Police. The
power supply generator to the warning lights shall not create
excessive noise, which might disturb the residents.
5.2.7
Existing structures, utilities and other facilities shall be protected,
from damage caused by settlement, lateral movement,
undermining and other hazards created by trenching operations.
5.2.8
Minimum interference shall be ensured with streets, walkways
and other adjacent facilities, occupied or used, while engaged in
operations or in the removal of debris.
5.2.9
Operations shall be conducted in such a manner so as to prevent
injury to persons, property in general, structures, other facilities
and utilities.
TCSP10403R0/YM
Date of Approval: June 25, 2008
PAGE NO. 10 OF 30
TRANSMISSION CONSTRUCTION STANDARD
5.3
5.4
TCS-P-104.03, Rev. 0
5.2.10
In case of utility damage, the repairs shall be done at no cost to
SEC.
5.2.11
Dust shall be controlled within populated areas of the construction
operations to the satisfaction of the SEC, by thoroughly
moistening all surfaces as required to prevent dust being a
nuisance to the public and to personnel working on the site or
along transport routes.
De-watering
5.3.1
In areas where high water table causes the trench to become
flooded, the trench shall be kept in dry either by pumping or
installation of a well point system depending upon the actual site
conditions until cable laying and backfilling operations are
completed. Trenches subject to high water table must be shored to
minimize trench-wall sloughing. The water removed from the
trench shall be disposed of in a proper manner either by pumping
to a storm water system or water tank trucks. If water is to be
pumped in to municipal sewage water system, prior approvals
must be obtained from the Municipal Sewage Authority.
5.3.2
Grading in the vicinity of excavations shall be controlled to
prevent surface water running into excavated areas. Any water
accumulated in the excavations shall be removed by pumping or
other means approved by SEC.
Compaction
5.4.1
Backfill materials shall be placed in uniform layers not exceeding
200 mm of uncompacted thickness. The method of compaction
shall be subject to the approval of SEC. Field density tests shall
be carried out to verify the degree of compaction and the results
shall satisfy the requirements of SEC Standards TCS-Q-113.02.
5.4.2
For static load up to 320 kPa, trench backfill shall be compacted
to not less than 70% relative density for noncohesive materials
(ASTM D4253, D4254) or 95% modified Proctor for Marl or
cohesive materials (ASTM D1557) unless otherwise specified by
the concerned Municipality.
5.4.3
For static load over 320 kPa, trench backfill shall be compacted to
not less than 85% relative density for noncohesive materials
(ASTM D4253, D4254) or 95% modified proctor for marl or
cohesive materials (ASTM D1557) unless otherwise specified by
the concerned Municipality.
TCSP10403R0/YM
Date of Approval: June 25, 2008
PAGE NO. 11 OF 30
TRANSMISSION CONSTRUCTION STANDARD
TCS-P-104.03, Rev. 0
5.4.4
All backfills located more than 3 m away from buildings and
other structures shall be mechanically compacted. Hand tampers
or small vibratory compactors shall be used within 3 m of
buildings and other structures.
5.4.5
For non-cohesive materials, compaction of backfill by saturating
with water may be used if proven to SEC that the required
compaction can be achieved with this method.
5.4.6
Warning tapes shall be buried 300 mm below finished grade level
(i.e., in lawn areas just below sweet sand, in paved areas, just
below the base course, etc.). The warning tapes shall have the
words “CAUTION-POWER CABLES BELOW, CONTACT
SEC”, in Arabic and English lettering in Traffic Black (RAL
9017) alternatively and with the following requirements:
Color
Width of tape
Thickness
5.4.7
Flame Red (RAL 3000)
450 mm
200 microns
Red concrete or calcium silicate tile cable covers shall be
provided for each cable being protected. The minimum spacing
between the cable and the tile cable cover shall be as shown in
Figure-2. The tiles shall cover the entire width of trench and
should satisfy the following requirements:
Dimensions
Min. Compressive Strength
Density
390 mm x 200 mm x 80 mm
28.0 MPa
17 kN/m3
5.4.8
PVC coated steel wire mesh shall be provided above the tile
cover. The steel wire mesh shall be 2.5 mm diameter and shall
cover the entire width of trench. The minimum depth between the
cable cover tiles and the PVC coated steel wire mesh shall be per
Figure-2.
5.4.9
Any of the work performed or installed shall not be covered up or
enclosed by other work prior to inspection and approval by SEC.
5.4.10 Before backfilling, the cables in position shall be inspected and
certified by SEC. Any of the work enclosed or covered up before
it has been inspected by SEC, shall be uncovered at no cost to
SEC.
TCSP10403R0/YM
Date of Approval: June 25, 2008
PAGE NO. 12 OF 30
TRANSMISSION CONSTRUCTION STANDARD
TCS-P-104.03, Rev. 0
5.4.11 The trench backfill shall be made level with adjacent surfaces to a
95% minimum compaction using modified Proctor density.
Should any material such as marl, gravel, etc., be contaminated
while excavating, new uncontaminated materials shall be
provided for backfilling. Excavated materials shall be tested and
approved by SEC prior to use as backfill.
5.4.12
5.5
The backfill material shall be compacted immediately after
placing. Each rolling operation shall follow the preceding
operation as early as possible. In areas too small for roller a
vibrating plate compactor or hand tamper may be used to achieve
through compaction.
Restoration
If the work is carried out on an area falling within the jurisdiction of a
Municipality, the Ministry of Transportation and/or restricted areas like
defense, navy, etc., then the materials and methods used shall conform to
the specifications of the appropriate governmental authority. Otherwise,
the following requirements shall apply:
5.5.1
TCSP10403R0/YM
Pavements
a.
Restore street pavements as per the requirements of SEC
Standards TCS-Q-113.02 such that the thickness shall not be
less than the existing. Reinstatement of asphalted surfaces
over duct banks at road junctions shall be completed within
three days of backfilling.
b.
A prime coat shall consist of the initial application of liquid
asphalt onto the surface of a non-asphalt base course. The
base shall be surface dry, free from dust and compacted
before the prime coat is applied. If the base has a high clay
content, a light application of water may be applied to the
surface of the base course prior to application of the prime
coat to facilitate penetration of the liquid asphalt into the
base. After the base has been prepared, and when in a warm,
surface dry condition, the prime coat shall be applied
uniformly to the surface of the base using a pressure
distributor.
c.
The priming material shall be applied to a width 300 mm
greater on each side of the roadway than the specified width
of the finished surface. Where there is a concrete curb at the
edge of the asphalt pavement, the curb face shall be primed
by means of a spouted water can or hand sprayer and
shielding to prevent spillage on exposed concrete surfaces.
The prime coat shall be permitted to cure until penetration
Date of Approval: June 25, 2008
PAGE NO. 13 OF 30
TRANSMISSION CONSTRUCTION STANDARD
TCS-P-104.03, Rev. 0
into the underlying surface, but at no time shall the curing
period be less than 24 hours.
TCSP10403R0/YM
d.
Pools of liquid asphalt occurring in depressions shall be
broomed or squeezed over the surrounding surface the same
day the prime coat is applied. At no time during the period of
curing shall traffic be allowed upon the primed surface of the
road. At locations where the prime coat has failed, it shall be
repaired to the satisfaction of SEC. If the primed surface is
damaged by equipment and personnel, it shall be repaired and
rolled prior to placement of binder course. The prime coat
shall be maintained at all times until the binder course is laid.
If required by SEC, the primed surface shall be swept prior to
laying binder. Care shall be taken to prevent over priming.
The prime coat shall be fully set and cured before placing an
asphalt mixture on the base.
e.
The tack coat shall be very thin and uniformly applied over
the entire surface of the area to be covered. A tack coat
application shall be made to all cold butt joints in both
asphalt base and asphalt surface courses of the paving. The
temperature of the liquid asphalt at the time of application
shall range from 40o to 80oC. If a sand storm occurs between
the application of a tack coat and the initiation of paving, the
excess sand blown by the wind shall be removed and a new
tack coat shall be applied.
f.
Unless otherwise indicated, restore grades to conditions
existing prior to excavation.
g.
Pavement markings and striping, if existing prior to the start
of any work, shall be replaced with the application of white
or yellow, reflectorized or non-reflectorized traffic zone
paint, to match existing conditions, or as directed by SEC.
h.
The work site shall be cleared after completion of the job.
Debris should be hauled to the dump area approved by the
Local Municipality.
i.
The work site shall at all times be kept neat, clean and free of
waste material or rubbish. Any surplus equipment and
material not required for further performance of the work
shall be promptly removed from the work site. Upon
completion of the work, all equipment, temporary structures,
rubbish and unused materials shall be removed from the work
site.
Date of Approval: June 25, 2008
PAGE NO. 14 OF 30
TRANSMISSION CONSTRUCTION STANDARD
j.
5.5.2
TCS-P-104.03, Rev. 0
All existing vegetation such as trees, shrubs and grasses on or
adjacent to the work site which are not to be removed and
which do not unreasonably interfere with the work shall be
preserved and protected.
Traffic Protection
a.
Traffic protection devices and methods of protection shall be
provided and shall comply with the requirements of the
Municipality or the concerned Traffic Police of the area
where the work is carried on. Steel sheets or wooden planks
shall be provided in order to permit safe crossing of the
trenches.
b.
The traffic flow shall be maintained as required in the
vicinity of the work site. At substation yards and entrances,
the trenches shall be covered with steel sheet covers to have a
free access during and after working hours.
c.
Flagmen, barricades, warning signs and warning lights shall
be provided as required.
d.
Also, during restoration operations, traffic cones, barricades,
lights and other protective devices required to protect traffic
and workmen shall be furnished, installed and maintained.
These shall be removed when restoration work is complete
and area is ready to receive traffic.
e.
All materials, equipment and safety items shall be placed or
stored in an orderly manner at suitable locations to avoid
traffic hazard.
f.
All energized lines used for temporary lights and power for
construction equipment shall be properly guarded/insulated.
5.5.3
Parking areas and driveway pavements shall be restored to the
lines, grades, thickness and construction existing prior to
excavation.
5.5.4
Sidewalks and Curbs
TCSP10403R0/YM
a.
Asphalt and concrete or tile sidewalks and curbs shall be
restored as directed by the Municipality or SEC, using new
asphalt and concrete of equal quality to the existing and to
match the lines, grades, thicknesses and construction existing
prior to removal.
b.
Surfaces damaged during work shall be repaired/reinstated as
directed by the Municipality or SEC at no cost to SEC.
Date of Approval: June 25, 2008
PAGE NO. 15 OF 30
TRANSMISSION CONSTRUCTION STANDARD
5.5.5
5.5.6
TCS-P-104.03, Rev. 0
Signs and Markers
a.
Temporary sign shall be provided for each permanent sign
removed. These shall be removed on completion of
construction and replaced with the permanent signs as before.
b.
Survey monument markers, survey control markers, elevation
bench markers, utility markers and right-of-way monuments
shall be removed and replaced at the original location and
elevation as before.
Landscaping
After completion of operations related to the work covered under
this Standard, all grassed areas and all landscaping in general
shall be brought up to a condition similar to or better than that
existed before and as approved by the Municipality or SEC.
5.6
5.7
Repair Work
5.6.1
No-objection certificates shall be obtained from all the related
authorities of the underground facilities like water, sewerage,
telephone, etc., before excavation or backfilling.
5.6.2
Backfills that settle or erode pavements, structures and any other
facilities damaged by such settlement or erosion shall be repaired.
5.6.3
If soil tests indicate that proper compaction has not been obtained,
it shall be re-compacted. Tests for compaction shall be performed
by SEC approved laboratory under the supervision of SEC.
Field Quality Control
5.7.1
TCSP10403R0/YM
Allowable Tolerances
a.
The finished grade shall not vary by more than 10 mm above
or below the adjacent grade or elevation.
b.
The moisture content of the fill materials shall be maintained
within plus or minus two percent (±2%) of the optimum
moisture content of the material as determined by ASTM
D1557 to facilitate compaction.
Date of Approval: June 25, 2008
PAGE NO. 16 OF 30
TRANSMISSION CONSTRUCTION STANDARD
5.7.2
Compaction
a.
5.8
TCS-P-104.03, Rev. 0
One (1) composite sample of asphalt mix shall be taken for
each production day from the first truckload of mix delivered
to the site for laboratory testing. The sample shall be taken by
the SEC approved Laboratory and tested per SEC Standards
TCS-Q-113.01, and the test reports for the following shall be
submitted:
i.
Gradation
ii.
Flow test
iii.
Stability
iv.
Asphalt cement
b.
The degree of compaction for asphalt pavement placed in the
field shall be equal to or greater than 96% of the laboratory
Marshall density determined for the material being used in
accordance with ASTM D1559.
c.
One (1) core sample of the compacted asphalt pavement shall
be taken for each 100 linear meters of road reinstated and
tested per ASTM D1559.
Completion
Following completion of all construction, the work site shall be cleaned of
all debris and leftover materials from excavation and construction
operations.
6.0
CABLE DUCTS REQUIREMENTS
6.1
General Requirements
6.1.1
TCSP10403R0/YM
Cable ducts shall be installed in those areas where access to the
cables for maintenance or repair is restricted. Such locations
include areas beneath existing or future roads and highways, areas
in near proximity to structures or footings where future
excavations would be difficult and areas where additional
physical protection to the cables is required and inside the
substation also.
Date of Approval: June 25, 2008
PAGE NO. 17 OF 30
TRANSMISSION CONSTRUCTION STANDARD
TCS-P-104.03, Rev. 0
6.1.2
All non-metallic ducts and/or metallic conduit shall be installed
with all elbows, bends, couplings, end bells, spacers and nonmetallic duct to metallic conduit adapters as required for the
underground electrical systems.
6.1.3
Underground ducts smaller than 50mm in size, shall be rigid
metallic conduit. Underground ducts, 50mm and larger, shall be
PVC ducts, except as otherwise specified.
6.1.4
Underground ducts shall be installed to ensure a minimum cover
of 600mm with respect to final grade except for high tension
cables which shall have a minimum cover of 750mm.
6.1.5
Duct lines shall be installed so that a minimum pitch of 75mm per
30 meters is maintained. Where elevations or slopes are not
otherwise determined, duct lines shall be installed so as to drain
into manholes.
6.1.6
Plastic spacers shall be installed with a maximum horizontal
interval of 1.5 meter so that minimum horizontal and vertical
separation between outside diameter or ducts is as follows:
a
b
c
Duct banks (below 600 volts) 50mm
Duct banks (above 600 volts) 75mm
Between communication and adjacent power ducts75mm
6.1.7
Duct banks shall be installed so as to clear all underground
piping, concrete footings, rock ledge, etc. with a minimum
separation of 150mm. A cushion of stone free sand shall be used
at such crossing points.
6.1.8
Non-metallic ducts shall be free from all substances which may
injuriously affect any wire or cable sheath or jacket. The duct
shall have a dense, uniform and homogeneous wall with a smooth
interior surface free from obstructions, rough or flaky areas. The
duct shall be non-magnetic, resistant to corrosive action,
unaffected by electrolysis and shall not soften, deform or
deteriorate when exposed to maximum safe operating temperature
of cables or upon immersion for long periods of time in ground
water. The bore of the duct shall be straight and circular in cross
section.
6.1.9
Elbows, bends, fittings and couplings shall be made of the same
grade material as straight lengths, except that plastic coupling
may be used in place of non-metallic coupling on non-metallic
duct.
TCSP10403R0/YM
Date of Approval: June 25, 2008
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TRANSMISSION CONSTRUCTION STANDARD
TCS-P-104.03, Rev. 0
6.1.10 The duct and fittings shall be of the tapered sleeve joint type. A
coupling shall be provided for each joint of conduit and for each
bend or elbow. Joints for plastic conduit shall be made with
solvent cement after the conduit has been cut square, deburred,
cleaned and dried. The joints shall be manufactured so that they
are sufficiently tight to prevent water, silt or concrete from
entering the duct.
6.1.11 The length for each size duct shall be standard with the
manufacturer. Each length shall be marked with the
manufacturer's name or trade-mark.
6.1.12 Plastic ducts shall be composed of high impact Polyvinyl
Chloride (PVC). Plastic ducts shall be light wall type where
encased in concrete and heavy wall type where direct buried.
Plastic ducts shall be from the approved manufacture.
Plastic ducts shall be used to protect the cables at point where the
cables cross in close proximity to other underground utilities &
duct banks
6.1.13 Underground ducts which are installed below the building
structure, or encased to form part of the building structure or are
within 1.5 meters of the building structure shall be heavy duty
galvanized steel.
6.2
6.3
Specific Requirements
6.2.1
All cable ducts/conduits, couplings and accessories shall be
installed in strict compliance with the manufacturer’s instructions.
6.2.2
The conduit material, size, class and type shall conform to 23TMSS-01. The system or manner of burial will depend on
required physical protection or loading of structures above the
ducts, which shall be specified by SEC.
6.2.3
The construction of direct buried or concrete duct banks shall
include conduit hangers or spacers. Refer to Figure-3.
6.2.4
Both ends of all conduit runs shall have end-bells to prevent
damage to the cables during installation. Refer to Figure-4.
Installation
6.3.1
Clean the ducts with swab.
6.3.2
After the ducts are laid and concrete encased or back-filled, they
shall be rodded by the contractor. A flexible mandrel, 6mm less in
diameter than the bore of the duct shall then be drawn through
followed by a wire brush cleaner 6mm larger in diameter than the
TCSP10403R0/YM
Date of Approval: June 25, 2008
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TRANSMISSION CONSTRUCTION STANDARD
TCS-P-104.03, Rev. 0
bore. All foreign matter shall be removed. If obstructions are
found which cannot be removed by cleaning so as to pass the
mandrel, the ducts shall be removed and re-laid at the expense of
the contractor.
6.3.3.
The testing and cleaning of a concrete encased duct shall be done
on the day after the concrete has been poured to remove any
concrete splash or spills in the ducts. Construction drawings,
which indicate duct line length and routing shall be verified and
field noted in conjunction with duct testing operations.
6.3.4
Install a pull rope for future cable installation. The pull rope shall
be of nylon with 13 mm diameter.
6.3.5
Plug the ends with ducts Seals. Duct sealing unit shall be as per
23-TMSS-02. The installation and removal of any duct sealing
unit shall comply with the manufacturer’s recommendations.
6.3.6
For the selection of the type of conduits to be used, the following
factors shall be considered:
a
b
c
d
The lower coefficient of friction available. Refer to
TES-P-104.05.
Heat transfer ability of the material
Resistance to deformation and fusion when cables
are short-circuited
Dimensions of the conduit shall be according to
NEMA.
6.3.7
Duct banks shall be run as straight as possible from termination to
termination. Ducts shall be laid in the excavated trenches in
continuous alignment and in the formation required.
6.3.8
Ducts shall be laid horizontally so that the butt joints of adjacent
ducts are not opposite each other. Changes in direction elevation
shall be made with the largest practical radium using bends,
sweeps, curved segments and/or deflection couplings as required.
Fittings shall be selected so that the minimum numbers of joints
occur in each change of direction. Joints shall be tight and well
fitted. All field cuts shall be square reamed and the ends of nonmetallic ducts properly tapered with tools designed for the task
and waterproofed in accordance with the manufacturer's
recommendations.
6.3.9
Ducts entering manholes and vaults shall terminate in end bells.
Vertical risers from underground duct banks shall utilize concrete
encased long radius rigid steel elbows, coated as specified herein.
Expansion joints shall be installed as required.
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Date of Approval: June 25, 2008
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TRANSMISSION CONSTRUCTION STANDARD
TCS-P-104.03, Rev. 0
6.3.10 During duct installation, both the completed and uncompleted
units of all duct sections shall be closed with suitable tight
fittings, caps or plugs to prevent the entrance of mud or foreign
matter into the duct bore. Wood plugs may be used for closing the
non-metallic ducts.
6.3.11 Concrete Encased Duct Bank – Ducts shall be installed as a self
supporting structure before pouring the concrete. The ducts shall
be securely fastened in place with heavy twine or steel wire and
anchored so as to maintain accurate position during the concrete
pour. Concrete shall be placed as soon as practicable after ducts
have been secured in place, checked for alignment and grade, and
approved by SEC. The ducts shall be protected so that they are
not damaged during the pour.
6.3.12 Concrete for encasement shall attain a 20N/mm2 strength at
28days (SEC spec. # 70-TMSS-03) and shall be colored with tile
– red cement color.
6.3.13 Underground Ducts and Conduit without Concrete Encasement
TCSP10403R0/YM
a
Excavate trenches for all direct buried conduits in locations
indicated on the contractor's approved drawings. Excavate
trenches to allow for 150mm sand bed, and 600mm minimum
cover over top of conduits. Grade the bottom of trenches
reasonably free from stones and other sharp objects which
could injure the conditions.
b
Conduits shall be laid on a 150mm sand bed with a minimum
separation between conduits of 50mm.
c
Backfill with sand and approved backfill as soon as the
conduit has been installed and the installation approved by
SEC. Place a 150mm sand layer, by hand, directly above and
on each side of the conduit and hand tamp to compact.
Backfill the balance of the trench above the sand with
approved backfill in 300 mm maximum layers. Compact each
layer (as per SEC standard # TCS-Q-113.02) with power
tampers to the density of adjacent undisturbed materials.
d
Bricks, planks and other supports shall not be used in lieu of
sand to bring ducts to grade. Multi-level duct runs shall be
installed in layers 150mm apart with sand backfill
surrounding and above each level placed and tamped before
the next level is laid.
e
Install a 150mm wide yellow warning tape marked
"Electrical" directly over the buried conduits 300 mm below
the finished grade.
Date of Approval: June 25, 2008
PAGE NO. 21 OF 30
TRANSMISSION CONSTRUCTION STANDARD
6.4
TCS-P-104.03, Rev. 0
Reinforced Concrete Cable Trench
The Contractor is responsible for the construction of cable trench, duct
banks and manhole where necessary. It should conform to the applicable
established standards. The specification is intended for use within the
substation also.
e underground system shall be either an open trench or backfilled trench
and are classified as direct-buried or concrete encased.
The reinforced concrete cable trench shall be designed to provide natural
ambient air cooling to the cables. The cable trench shall be provided with
cover that will not impede the natural air circulation and offer easy access
to cables during maintenance/ inspection procedures.
Reinforced concrete cable trench shall be used for the substation as
follows:
6.4.1
Inside the building – reinforced concrete cable trench with
removable checkered steel plate cover painted according to TESH-107.01 shall be provided inside the building whereever
required.
6.4.2
Outside the building – reinforced concrete cable trench with
removable precast concrete cover or fabricated steel grill cover
painted according to TES-H-107.01 shall be provided outside the
building to route the Power, Control and NFOC cables.
Reinforced concrete cable trench shall be designed and
constructed with adequate size and strength suitable for the
following features:
TCSP10403R0/YM
a
Sufficient space to accommodate the required cables, cable
ducts and associated accessories.
b
Space for maintenance and operations.
c
Provide Steel ladder rung, painted according to TES-H107.01, at proper location for maintenance.
d
Cable trays, supports and other associated accessories.
e
Provide drain holes of sufficient size and spacing throughout
the trench length. At the bottom of drain holes, sufficient
amount of graded gravel shall be provided to drain water, this
shall be done prior to pour trench floor.
Date of Approval: June 25, 2008
PAGE NO. 22 OF 30
TRANSMISSION CONSTRUCTION STANDARD
TCS-P-104.03, Rev. 0
f
Provide at least 0.5% slope for the trench floor to allow the
water to flow towards the drain holes and away from the
building cable cellar.
g
Heavy traffic rated trench cover (precast reinforced concrete
or fabricated steel) shall be provided at the heavy traffic area,
i.e. road crossing, etc. The Contractor may also provide
concrete encased duct bank for this portion.
h
Trench shall be provided with natural ventilation for cooling
the power cables.
i
Provide 75mm thick lean concrete prior to pour trench floor.
j
Provide 200 microns polyethylene sheet prior to pour lean
concrete.
k
Necessary concrete protective coating shall be provided.
l
Concrete works for the trench shall conform to 70-TMSS-03
and TCS-Q-113.03.
m Trenching and earthworks shall conform to TCS-Q-113.02.
6.5
Conduit Hangers or Spacers
In the assembly of a duct bank, the conduits shall be supported in air by
hangers or spacers, which hold the conduits in place during the backfilling
of inter-conduit space with sand, or cement. The material of spacer shall be
polypropylene plastic.
Spacers for supporting conduits shall be installed at intervals not
exceeding 1.5 meters. Spacers shall be with interlocking lugs and matching
holes for field assembly and into multiple units.
Base spacers with pads shall be provided in sandy or soft soil condition or
where the number of vertical tiers is grater than two. Intermediate spacers
shall be used as the base unit in good soil and in conduit banks of two (2)
or less tiers.
Figure-3 shows typical conduit hangers for a 4x3 conduit arrangement.
However, a suitable conduit hanger or spacer can support any number of
conduit arrangements.
6.6
End-Bells
An end-bell is a flared opening for easy pulling of cables. End-bell
eliminates sharp corner that might damage the cable jacket as cable is
pulled in conduit or duct. It also protects the cable sheath as the cable
TCSP10403R0/YM
Date of Approval: June 25, 2008
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TRANSMISSION CONSTRUCTION STANDARD
TCS-P-104.03, Rev. 0
moves longitudinally due to thermal load cycling. End-bells shall be
installed on all cable conduits.
The beveled radius feature provides a smooth surface over which the cable
passes when it is pulled into the duct. The beveled radius also minimizes
elongation of the cable caused by frictional drag between cable and duct
interface.
6.7
Duct Sealing Requirements
The duct sealing units shall be of the manufacturer’s standard design and
shall meet or exceed the requirements mentioned in SEC specification #
23-TMSS-02. Cable duct sealing units shall be designed for the expected
cable jacket temperature in addition to the service conditions specified in
01-TMSS-01
The duct sealing units shall be designed and constructed to maintain
sealing efficiency for a period of 20 years under a constant pressure of 69
kPa (10 psig, 7.05 m of water head) under service conditions.
TCSP10403R0/YM
Date of Approval: June 25, 2008
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TRANSMISSION CONSTRUCTION STANDARD
TCS-P-104.03, Rev. 0
FIGURE-1
MIN. TRENCH DIMENSIONS
Minimum Trench Dimensions and Amount of Backfill Required to Reduce Soil Thermal
Resistivity to an Average Value of 120°C cm/W.(Typical)
2040
CURVE FOR
MIN. DEPTH
1785
CURVE FOR
MIN. WIDTH
1530
1275
1020
765
510
255
140
150
160
170
180
190
CURVE FOR
MIN. AMOUNT
OF SPECIAL
BACKFILL
AROUND PIPE
OR CABLE
200
ORIGINAL SOIL THERMAL RESISTIVITY IN °Ccm/W
NOTE: FIGURE-1 is for 150 mm diameter pipe or cable buried at a depth of 915 mm
(Typical).
1.
For original soils with Thermal Resistivity (TR) as indicated below, the
following changes shall control:
For TR <140: use min. requirements as outlined in Fig-1 above, i.e., trench
width of 405 mm and depth of 1220 mm. However, this 405 mm minimum
trench width shall be adjusted to 450 mm to accommodate the width of the
terratape cable marker.
For TR >200, for every 10% increase in TR over 200ºC cm/W, both the trench
width and the depth of burial shall be increased by 10%. SEC approval shall be
obtained prior to any alteration of trench dimensions or where increase in depth
of burial is not feasible.
2.
Cable/pipe diameter
For cable/pipe diameter of more than 150 mm, trench dimensions shall be
increased by 20% for every 25 mm over 150 mm of diameter, and the amount of
the special backfill shall be increased as required.
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Date of Approval: June 25, 2008
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TRANSMISSION CONSTRUCTION STANDARD
TCS-P-104.03, Rev. 0
FIGURE-2
RESTORATION OF ASPHALT PAVEMENT AT TRENCH CROSSINGS
IMPORTANT:
SEE NEXT PAGE FOR NOTES AND LEGEND
DWG # TC-0403-0100-00
TCSP10403R0/YM
Date of Approval: June 25, 2008
PAGE NO. 26 OF 30
TRANSMISSION CONSTRUCTION STANDARD
TCS-P-104.03, Rev. 0
LEGEND
1.
Final-Surface course per TCS-Q-113.01
2.
Asphalt Binder course per TCS-Q-113.01. Also see Note 3.
3.
Corners rounded off
4.
Existing pavement thickness varies.
5.
Cable trench in cohesive soil that will have stable vertical trench walls or
when suitably braced as approved by the SEC
6.
Cable Warning Tape (Terratape)
7.
PVC coated steel wire mesh
8.
Red/green concrete or calcium silicate tile cover with dimensions 50 x 200
x 400 mm or 80 x 190 x 390 mm (Red color tiles for electric cables &
green color tiles for communication cables)
9.
Angle of repose (see Note 4)
10.
Cable or Duct. For particular cable or duct arrangement, refer to Figure
Nos. 05-01 to 05-08 of TES-P-104.05.
11.
Backfill with clean sand in 150 mm lifts and compacted per TCS-Q113.02
12.
Cable trench in non-cohesive soil. See Note 4.
13.
Marl (cohesive) material shall be placed on the top of the backfill and
compacted to 95% modified Proctor (ASTM D1557) per TCS-Q-113.02.
14
Loose placing of mix to protrude above pavement by 12 mm to 20 mm for
6A mix
15.
Tamped mix to protrude above the existing pavement by: 6 mm to 12 mm
for 6A mix.
16.
Existing pavement to be straight saw cut only.
17.
Prime coat application per TCS-Q-113.01, on base course of roadways
prior to paving and also on base course of nonroad pavement if asphalt is
not placed within 48 hours.
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Date of Approval: June 25, 2008
PAGE NO. 27 OF 30
TRANSMISSION CONSTRUCTION STANDARD
TCS-P-104.03, Rev. 0
NOTES:
1.
For particular trench dimensions, refer to Figure nos. 05-01 to 05-08 of
TES-P-104.05.
2.
For all cases, saw cutting shall be done for Asphalt pavements. If during
construction the saw cut vertical sides of the existing asphalt pavement are
damaged, the Asphalt shall be cut along a parallel line and asphalting
done.
3.
Traffic shall not be allowed before the tamped surface lift has cooled off
for at least three hours or as directed by SEC.
4.
For unusual conditions or shallow trenches in non-cohesive soil , and
where the use of sheeting is not feasible or justified, the trench walls may
be sloped at the angle of repose.
5.
Open, unbraced trenches shall not be excavated below existing ground
water level without dewatering by means of well points or other methods,
subject to approval of SEC.
6.
In cases where base course is collapsing, SEC shall be informed and the
existing pavement shall be cut further to repair it upon approval. The
additional pavement cut will depend on the severity of the collapsing base
course or as required by the concerned Municipality. In SEC areas, the
COMPANY REPRESENTATIVE shall specify this additional pavement
cut.
TCSP10403R0/YM
Date of Approval: June 25, 2008
PAGE NO. 28 OF 30
TRANSMISSION CONSTRUCTION STANDARD
TCS-P-104.03, Rev. 0
FIGURE-3
TYPICAL CONDUIT HANGERS OR SPACERS
ASSEMBLED CONDUIT HANGERS (TYPICAL)
DWG # TC-0403-0200-00
TCSP10403R0/YM
Date of Approval: June 25, 2008
PAGE NO. 29 OF 30
TRANSMISSION CONSTRUCTION STANDARD
TCS-P-104.03, Rev. 0
FIGURE-4
TYPICAL END-BELL
DWG # TC-0403-0300-00
TCSP10403R0/YM
Date of Approval: June 25, 2008
PAGE NO. 30 OF 30