MEDIUM-VOLTAGE DRY DISTRIBUTION TRANSFORMERS
PART I -GENERAL
1.01 RELATED DOCUMENTS:
A. Drawings and general provisions of Contract, including Conditions of
contract and Division-1 Specification Sections, apply to section.
1.02 DESCRIPTION OF WORK:
This section covers the work of distribution dry type transformers as required
by the contract and includes the following items:
1.03 SUMMARY:
A. This section includes distribution and power transformers with
medium-voltage primaries.
B. Related Sections include the following:
1. Division 16 Section "Basic Electrical Materials and Methods"
2. Division 16 Section "Enclosed Bus Assemblies Conductor and Cables"
for busway and LV cables connections between transformers and
secondary distribution equipment.
3. Division 16 Section "Earthing"
4. Division 16 Section "Main Distribution Boards"
5. Division 16 Section "Medium – Voltage Cables" for cable terminations at
transformers.
6. Connection to BMS system, including interface elements such as relays,
transducers, etc. as detailed in Division 15 specifications, BMS schedules
and/or shown on the drawings.
1.04 Quality Assurance:
A. Manufactures Qualifications: Engage a firm experienced in manufacturing
transformers similar to those indicate for this project and with a record of
successful in-service performance.
B. Standards: Equipment and component parts are to comply with the
following standards.
1. Common Clauses for HV switchgear and control gear standards: IEC 694.
2. Power transformers: IEC 76, 354, 726.
3. NFPA 70 National Electrical Code (NEC).
2
1.05 SUBMITTALS:
A. Product Data: Including full technical data on features, components, ratings
foundation data and performance for each type of transformer specified.
Include dimensioned plans, sections, and elevation view show minimum
clearances and installed devices and features. Submit Manufacturer's
catalogues.
B. Wiring Diagrams: Detail wiring and identify terminals for tap changing and
connecting field-installed wiring as well as fabrication drawings &
installation drawings.
C. Product Certificates: Signed by manufacturers of transformers certifying
that the products furnished comply with requirements.
D. Type Test certificates: submit to verify compliance of main equipment with
the relevant IEC standards and in general are to include lightning impulse
with standard, power frequency voltage, temperature rise, short time current
withstand and enclosure protection to IEC 529.
E. Routine Tests:
1. Each transformer unit is to undergo tests at the manufacturer's works in
accordance with the relevant standards. Submit routing test reports, prior
to shipping equipment indicating ambient test conditions and guaranteed
rating of equipment under site conditions. Routine tests for power
transformers are to include measurement of winding resistance, voltage
ratio, check of polarity/vector group, impedance voltage, load loss,
no-load loss, no-load current, induced over voltage withstand test and
separate source voltage withstand test. The following routing tests
specified in IEC 60726 shall be carried out at the manufacturer's works on
each and every transformer:
a. Short circuit impedance.
b. Partial discharge measurement as per IEC 60726 (special test).
c. Routine Tests on Magnetic Circuit.
2. The magnetic circuit of the transformer shall be pressure tested for 1
minute at 2000 volts a.c. between the core and earth with the link
connecting core and tank removed. Alternatively, the test may be
performed with a 2,500 volt megger and the transformer can be
considered to be satisfactory, provided a reading in excess of 5 mega
ohms is obtained, between the core and earth.
a. Secondary wiring high voltage test at 2 kV for 1 minute (if applicable).
3. Acceptance test certificate of each transformer shall necessarily indicate
but not be limited to the following:-
a. All the routine tests conducted on the transformer and the
measurements made.
b. Guaranteed values of losses, impedance etc.
c. Calculated values of losses, impedance etc. reference temperature
where applicable, based on measurements.
3
F. Shop and Construction Drawings: Submit drawings for approval including,
but not limited to the following:
1. Plans and elevations, with dimensions and weights.
2. Arrangement of equipment and general layouts.
3. One-line diagram of power system.
4. Foundation details grouting holes and installation details.
G. Sound-Level Test Reports: Certified copies of manufacturer's sound-level
tests applicable to equipment for this project.
H. Field Test Reports: Indicate and interpret test results for compliance with
performance requirements.
I. Maintenance Data: for transformers to include in the maintenance manuals
specified in Division 1.
J. After engineer's approval and prior to fabrication, submit foregoing
including approved transformer shop drawings utility co. for approvals.
1.06 SPARE PARTS TOOLS AND INSTRUMENTS:
A. Spare parts provide spare parts as recommended by the manufacturer for
one year maintenance as expected under local conditions and to allow for
emergency replacement due to accidental breakage or failure.
B. Tools and instruments provide tools instruments required for normal
routing inspection, testing operation and maintenance recommended by the
manufacturer.
C. Tools and instruments for oil transformer are to include oil sampling kit.
1.07 WARRANTY:
A. Manufacturers Warranty: Submit a written warranty signed by the
manufacturer agreeing to repair, restore or replace any defective equipment
specified in this section during the specified warranty period.
1. Warranty Period: 1 year from date of substantial completion.
1.08 DELIVERY STORAGE AND HANDLING:
A. Temporary Heating: for indoor, dry-type transformers apply temporary heat
according to manufacturer's written instructions within the enclosure of each
ventilated-type unit throughout periods during which equipment is not
energized and isn't in a space that is continuously under normal control of
temperature and humidity.
1.09 COORDINATION:
A. Coordinate layout and installation of transformers with other construction.
B. Coordinate size and location of concrete or mounting bases. Concrete,
reinforcement and formwork requirements are specified in Division 3
Section "Cast-in-Place Concrete"
4
PART 2 –PRODUCTS
2.01 MANUFACTURERS:
A. Available Manufacturers: subject to compliance with requirements,
B. For approved Manufacturers refer to the approved manufacturers list.
2.02 DRY TYPE CAST RESIN POWER TRANSFORMER:
A. Type: 3 phase, indoor type with environmental class (E1) climatic class
(C1) and fire class (F1) two winding solventless cast epoxy resin, vacuum
pressure impregnated windings, with minimum class F insulation on inner
LV cores and class B on outer MV cores, rated for continuous operation
under worst site ambient conditions at full load and complying with IEC
60726. temperature rise isn't to exceed 100 deg. C over an average ambient
of 40 deg. C for class B insulation and 80 deg. C over an average ambient of
40 deg. C for class F insulation.
B. Insulation and Encapsulation: Humidity resistant, explosion and
fire-resistant, self-extinguishing tropicalized, giving non-toxic gases in the
event of fire.
C. Tapping is to be provided on MV side by means of re-connectable links
(off-circuit), giving +/- 2.5% +/-5% +/-7.5% tapping on transformers.
D. Rubber sound isolation pads are to be provided between core and coil
assemblies, and between base and housing.
E. Cooling fans are to be provided to permit 30% increase in rated power.
F. Mounting and Handling: Transformer base and structure are to have lifting
hooks or lugs, towing and lashing eyes or lugs and provision for roller
wheels.
G. Temperature monitoring is to be provided by externally mounted tripping
units giving alarm and trip at two stages with about 20 deg. C temperature
difference, actuated by three embedded thermistor sensors in LV windings
(hot-spot). Additional thermal monitoring/control is to be provided for
cooling fan operation.
H. Terminals: Arranged as described in paragraph (2.02) hereof and/or as
shown on the Drawings and are to be compatible for copper or aluminum
cable termination.
I. Earthing bolts or copper pads are to be provided on main frame of
transformer. Earthing busbars are to be provided on LV and MV sides of
housing.
J. Housing: Sheet steel construction IP 31 for indoor installation.
K. Characteristics:.
1. Rated Power (net without fans) : as shown on the drawings
2. Frequency : 50 Hz
3. Rated Voltage:
a. MV Side (primary) : 10.5 kV
b. LV Side (secondary) : 400 V
5
4. Winding Connections : Dy11 neutral insulated and
brought out
5. Impedance Voltage at Rated Current: 6%
6. Rated Power Frequency withstand-voltage: 50kV
7. Lighting Impulse withstand-voltage : 75kV
8. Short –Circuit Apparent Power of the System at Lovation: 500 MVA
9. Duration of Short-Circuit- Withstand: 2 seconds
10. Terminal Connection System:
a. MV Side : cable sealing ends bolted from below.
b. LV Side : busbar termination box.
11. Low Losses Type.
L. Accessories are to include the following:.
1. Earthing switch, fault-making type, on MV side of housing interlocked
with door visible from outside the enclosure, with trip contact for
tripping MV circuit breaker before closing earthing switch.
2. Fans control for extra rating of transformer.
3. Four re-orientable roller rim wheels and attachment accessories.
M. Permissible overload capacity without undue heating shall be 20% for 1-1½
hours.
N. Winding temperature rise by resistance shall not exceed 100OC.
O. Each transformer shall be of double wound type with both the HV and LV
windings individually encapsulated in rigid steel mould. The coils shall be
impregnated with quartz filled epoxy resin and cast under vacuum, to
produce a smooth finish without voids and undulations.
P. The size and spacing of the conductors used in the windings shall be such
that the coils are self-supporting prior to impregnation and where
applicable, shall allow the epoxy resin to fill all of the space in and between
adjacent layers and turns.
Q. The coefficients of expansion of the windings and epoxy resin shall not
differ by more than 15%.
R. The windings shall be made of Aluminum.
S. A visible warning notice shall be fixed adjacent to the tapping links and
worded as follows:
" WARNING-OFF LOAD TAP CHANGING LINKS – ISOLATE HV
AND LV SUPPLIES TO TRANSFORMER BEFORE OPERATION"
T. Each distribution transformer shall be equipped with the following
accessories:
- Lifting lugs for complete transformer.
- Skid base with jacking and pulling provisions.
- Seismic ZA bolt down/chuking and anti-sway bracing.
- Two grounding pads on diagonally opposed sides for the base with bolt
type cable clamp adjustable for copper ground cables ranging from
95mm2 to 240mm2 for chassis grounding. One of the pads shall be
located at the side where the secondary neutral bushing is mounted.
6
- Fully enclosed cable end box on high voltage.
- Diagrammatic weatherproof stainless steel engraved or etched
nameplate. The nameplate shall show full rating of transformer, voltage
and tap ratios, impedance, weight vector diagram temperature class and
temperature rise, etc… and shall bear a connection diagram showing
studs, tap changers and other parts. Nameplate shall be in English.
- In addition to items listed hereinbefore, provide relaying and protection
as required in coordination with LV and MV circuit breakers.
- Forced ventilation fans.
- Transformer enclosure to suit the location and anticipated
environmental conditions. This shall provide a degree of protection not
less than IP 31 in compliance with IEC 60529.
-
2.03 TECHNICAL REQUIREMENTS
The requirements for Voltage other than 10.5 kV shall be modified as needed.
IEC Compliance 160076-11"Dry Type Transformers"
HV Supply System 3300V/6600V/10500V
- Number of Phases 3 Phase
- Fault Level (nominal design) 500 MVA
LV Supply System
- No-load Voltage 400V/3300V
- Number of Phases 3 Phase
- System Neutral 4 wire/3 wire
- Rating As shown on drawings
Supply Frequency (HZ) 50 Hz
HV Winding Connection Delta/Star
LV Winding Connection Star
Vector Group Reference As shown on drawings
Impedance at 75OC 6%
HV Tapping (%of no-loads volts) ±2.5%,±5%±,7.5%±
Method of cooling Forced for 40% extra rating
Secondary Voltage at:
- Full Load 400V/3300V
- No Load 400V/3300V
HV Insulation Level 12 kV
- Impulse kV peak 75 Bill (at 11 kV)
- Power Frequency (kV rms) 28 kV (at 11 kV)
Paint Finish Colot Manufacturer Standard
HV Conductor and Type Top entry xple cables
LV Conductor and Type Top entry busbar
Indoor or Outdoor Installation Indoor
Space Limitations Refer to layout drawings
Coil Material (HV) Aluminium
Coil Material (LV) Aluminium
7
PART 3- EXECUTION
3.01 INSTALLATION:
A. Locations and Layout: Exact locations and physical layout of equipment and
components may be varied as required to suit manufacture's design and as
approved, provided the required functions and operations are accomplished,
follow the identification of the units indicated on drawings exactly to ease
checking and building maintenance procedures.
B. Equipment Bases: Ensure that concrete bases and foundations provided for
installation of equipment are constructed in accordance with approved shop
and construction drawings and equipment manufacturer's drawings and that
holes for fixing bolts and provisions for passage of cables etc. are provided as
required.
C. Cable Trenches: Ensure that trench construction and covers provided for
installation of power and control cables are in accordance with approved shop
and construction drawings.
D. Built –In Items: Ensure that equipment supports, fixings and the like, and
sleeves for passage of feeders and cables which are to be built into concrete
foundations, bases, cable trenches or building structure are provided as and
when required and that they are properly installed.
E. Equipment: Install on concrete bases etc. and assemble completely plumb and
level, before grouting in holding-down bolts.
F. Supports and Terminations: Install all incoming and outgoing cable supports,
cable ends and termination fittings required for MV, LV and control cables
G. Relays: Set in accordance with manufacturer's instructions and the local
power authority requirements.
H. Earthing: ensure that earthing installation is as described in Division 16
Section "Earthing" of the Specification and/or as shown on the Drawings.
I. Temporary Lifting provisions: Remove temporary lifting eyes, channels
brackets and temporary blocking of moving parts from switchgear units and
components.
3.02 IDENTIFICATION.
A. Identify transformers and install wiring signs according to Division 16
Section "Basic Electrical Materials and Methods".
B. The power supply for the cooling fans shall be provided from the particular
transformer via a suitably fused switch. This switch shall bear the inscription
in yellow letters on a black background in both English and Arabic.
" WARNING - SUPPLY FOR TRANSFORMER COOLING FANS – DO
NOT SWITCH OFF"
8
3.03 CONNECTIONS:
A. Tighten bus joint, connector and terminal bolts according to manufacturer's
published torque-tightening values. If manufacturer's torque values are not
indicated, use those specified in applicable Standards.
3.04 FACTORY TEST:
1. The Contractor shall be responsible for performing the Dry type
transformer factory test.
2. The Dry type transformer factory test shall be performed at the country of
origin the presence of the Client's, Electrical Consultant and Engineer's
representatives team. the team will comprise three representatives all
expenses are to be borne by the Contractor.
3. the contractor shall provide to the engineer a certified factory test report.
3.05 FIELD QUALITY CONTROL:
A. Equipment: Inspect equipment upon delivery to site and report any damage
to Engineer.
B. Components: Check component ratings, types, sizes and wiring connections,
including current and voltage transformers, fuses, switches instruments and
relays.
C. Manufacturer's instructions are to be followed under all circumstances.
Carry out and record measurement and tests recommended by the
manufacturer.
D. Test Objectives: To ensure transformer is operational within industry and
manufacturer's tolerances, is installed according to the contract Documents,
and is suitable for energizing.
E. Test Labeling: On satisfactory completion of tests for each transformer,
attach a dated and signed "Satisfactory Test" label to tested component.
F. Schedule tests and provide notification at least 7 days in advance of test
commencement.
G. Report: Submit a written report of observations and tests. Report defective
materials and installations.
H. Test: Include the following minimum inspections and tests according to
manufacturer's written instructions.
1. Inspect accessible components for cleanliness, mechanical and electrical
integrity and damage or deterioration. Verify that temporary shipping
bracing has been removed. Include internal inspection through access
panels and covers for dry-type transformers.
2. Inspect bolted electrical connections for tightness according to
manufacturer's published torque values.
3. Insulation Resistance: Perform meg-ohmmeter tests of primary and
secondary winding to winding and winding to ground.
9
4. Duration of Each Test: 10 minutes.
5. Temperature Correction: Correct results for test temperature deviation
from 20 deg C standard.
6. Turns Ratio: Measure between windings at each tap setting. Measured
ratios deviating more than 0.5 percent from calculated or measured ratio
for an adjacent coil is not acceptable.
7. Winding Resistance: Measure for windings at nominal tap setting.
Measured resistance, deviating more than 1 percent, from that of
adjacent windings is not acceptable.
8. Test Failures: Compare test results with specified performance or
manufacturer's data. Correct deficiencies identified by tests and retest.
Verify that transformers meet specified requirements.
9. Any other tests required by the electrical power authority.
3.06 GROUNDING:
A. Comply with Division 16 Section "Grounding and Bonding" for materials
and installation requirements.
3.07 CLEANING:
A. On Completion of Installation, inspect components. Remove paint splatters
and other sports, dirt and debris. Repair scratches and mars on finish to match
original finish. Clean components internally using methods and materials
recommended by manufacturer.
3.08 ADJUSTING:
A. After installing and cleaning touch up scratches and mars on finish to match
original finish.
B. Adjust transformer taps to provide optimum voltage conditions at utilization
equipment throughout normal operation cycle of facility. Record primary and
secondary voltages and tap settings and submit with test results.
3.09 DEMONSTRATION:
A. Train Employer's maintenance personnel to adjust, operate, and maintain the
system installation
END OF SECTION 16350
PART I -GENERAL
1.01 RELATED DOCUMENTS:
A. Drawings and general provisions of Contract, including Conditions of
contract and Division-1 Specification Sections, apply to section.
1.02 DESCRIPTION OF WORK:
This section covers the work of distribution dry type transformers as required
by the contract and includes the following items:
1.03 SUMMARY:
A. This section includes distribution and power transformers with
medium-voltage primaries.
B. Related Sections include the following:
1. Division 16 Section "Basic Electrical Materials and Methods"
2. Division 16 Section "Enclosed Bus Assemblies Conductor and Cables"
for busway and LV cables connections between transformers and
secondary distribution equipment.
3. Division 16 Section "Earthing"
4. Division 16 Section "Main Distribution Boards"
5. Division 16 Section "Medium – Voltage Cables" for cable terminations at
transformers.
6. Connection to BMS system, including interface elements such as relays,
transducers, etc. as detailed in Division 15 specifications, BMS schedules
and/or shown on the drawings.
1.04 Quality Assurance:
A. Manufactures Qualifications: Engage a firm experienced in manufacturing
transformers similar to those indicate for this project and with a record of
successful in-service performance.
B. Standards: Equipment and component parts are to comply with the
following standards.
1. Common Clauses for HV switchgear and control gear standards: IEC 694.
2. Power transformers: IEC 76, 354, 726.
3. NFPA 70 National Electrical Code (NEC).
2
1.05 SUBMITTALS:
A. Product Data: Including full technical data on features, components, ratings
foundation data and performance for each type of transformer specified.
Include dimensioned plans, sections, and elevation view show minimum
clearances and installed devices and features. Submit Manufacturer's
catalogues.
B. Wiring Diagrams: Detail wiring and identify terminals for tap changing and
connecting field-installed wiring as well as fabrication drawings &
installation drawings.
C. Product Certificates: Signed by manufacturers of transformers certifying
that the products furnished comply with requirements.
D. Type Test certificates: submit to verify compliance of main equipment with
the relevant IEC standards and in general are to include lightning impulse
with standard, power frequency voltage, temperature rise, short time current
withstand and enclosure protection to IEC 529.
E. Routine Tests:
1. Each transformer unit is to undergo tests at the manufacturer's works in
accordance with the relevant standards. Submit routing test reports, prior
to shipping equipment indicating ambient test conditions and guaranteed
rating of equipment under site conditions. Routine tests for power
transformers are to include measurement of winding resistance, voltage
ratio, check of polarity/vector group, impedance voltage, load loss,
no-load loss, no-load current, induced over voltage withstand test and
separate source voltage withstand test. The following routing tests
specified in IEC 60726 shall be carried out at the manufacturer's works on
each and every transformer:
a. Short circuit impedance.
b. Partial discharge measurement as per IEC 60726 (special test).
c. Routine Tests on Magnetic Circuit.
2. The magnetic circuit of the transformer shall be pressure tested for 1
minute at 2000 volts a.c. between the core and earth with the link
connecting core and tank removed. Alternatively, the test may be
performed with a 2,500 volt megger and the transformer can be
considered to be satisfactory, provided a reading in excess of 5 mega
ohms is obtained, between the core and earth.
a. Secondary wiring high voltage test at 2 kV for 1 minute (if applicable).
3. Acceptance test certificate of each transformer shall necessarily indicate
but not be limited to the following:-
a. All the routine tests conducted on the transformer and the
measurements made.
b. Guaranteed values of losses, impedance etc.
c. Calculated values of losses, impedance etc. reference temperature
where applicable, based on measurements.
3
F. Shop and Construction Drawings: Submit drawings for approval including,
but not limited to the following:
1. Plans and elevations, with dimensions and weights.
2. Arrangement of equipment and general layouts.
3. One-line diagram of power system.
4. Foundation details grouting holes and installation details.
G. Sound-Level Test Reports: Certified copies of manufacturer's sound-level
tests applicable to equipment for this project.
H. Field Test Reports: Indicate and interpret test results for compliance with
performance requirements.
I. Maintenance Data: for transformers to include in the maintenance manuals
specified in Division 1.
J. After engineer's approval and prior to fabrication, submit foregoing
including approved transformer shop drawings utility co. for approvals.
1.06 SPARE PARTS TOOLS AND INSTRUMENTS:
A. Spare parts provide spare parts as recommended by the manufacturer for
one year maintenance as expected under local conditions and to allow for
emergency replacement due to accidental breakage or failure.
B. Tools and instruments provide tools instruments required for normal
routing inspection, testing operation and maintenance recommended by the
manufacturer.
C. Tools and instruments for oil transformer are to include oil sampling kit.
1.07 WARRANTY:
A. Manufacturers Warranty: Submit a written warranty signed by the
manufacturer agreeing to repair, restore or replace any defective equipment
specified in this section during the specified warranty period.
1. Warranty Period: 1 year from date of substantial completion.
1.08 DELIVERY STORAGE AND HANDLING:
A. Temporary Heating: for indoor, dry-type transformers apply temporary heat
according to manufacturer's written instructions within the enclosure of each
ventilated-type unit throughout periods during which equipment is not
energized and isn't in a space that is continuously under normal control of
temperature and humidity.
1.09 COORDINATION:
A. Coordinate layout and installation of transformers with other construction.
B. Coordinate size and location of concrete or mounting bases. Concrete,
reinforcement and formwork requirements are specified in Division 3
Section "Cast-in-Place Concrete"
4
PART 2 –PRODUCTS
2.01 MANUFACTURERS:
A. Available Manufacturers: subject to compliance with requirements,
B. For approved Manufacturers refer to the approved manufacturers list.
2.02 DRY TYPE CAST RESIN POWER TRANSFORMER:
A. Type: 3 phase, indoor type with environmental class (E1) climatic class
(C1) and fire class (F1) two winding solventless cast epoxy resin, vacuum
pressure impregnated windings, with minimum class F insulation on inner
LV cores and class B on outer MV cores, rated for continuous operation
under worst site ambient conditions at full load and complying with IEC
60726. temperature rise isn't to exceed 100 deg. C over an average ambient
of 40 deg. C for class B insulation and 80 deg. C over an average ambient of
40 deg. C for class F insulation.
B. Insulation and Encapsulation: Humidity resistant, explosion and
fire-resistant, self-extinguishing tropicalized, giving non-toxic gases in the
event of fire.
C. Tapping is to be provided on MV side by means of re-connectable links
(off-circuit), giving +/- 2.5% +/-5% +/-7.5% tapping on transformers.
D. Rubber sound isolation pads are to be provided between core and coil
assemblies, and between base and housing.
E. Cooling fans are to be provided to permit 30% increase in rated power.
F. Mounting and Handling: Transformer base and structure are to have lifting
hooks or lugs, towing and lashing eyes or lugs and provision for roller
wheels.
G. Temperature monitoring is to be provided by externally mounted tripping
units giving alarm and trip at two stages with about 20 deg. C temperature
difference, actuated by three embedded thermistor sensors in LV windings
(hot-spot). Additional thermal monitoring/control is to be provided for
cooling fan operation.
H. Terminals: Arranged as described in paragraph (2.02) hereof and/or as
shown on the Drawings and are to be compatible for copper or aluminum
cable termination.
I. Earthing bolts or copper pads are to be provided on main frame of
transformer. Earthing busbars are to be provided on LV and MV sides of
housing.
J. Housing: Sheet steel construction IP 31 for indoor installation.
K. Characteristics:.
1. Rated Power (net without fans) : as shown on the drawings
2. Frequency : 50 Hz
3. Rated Voltage:
a. MV Side (primary) : 10.5 kV
b. LV Side (secondary) : 400 V
5
4. Winding Connections : Dy11 neutral insulated and
brought out
5. Impedance Voltage at Rated Current: 6%
6. Rated Power Frequency withstand-voltage: 50kV
7. Lighting Impulse withstand-voltage : 75kV
8. Short –Circuit Apparent Power of the System at Lovation: 500 MVA
9. Duration of Short-Circuit- Withstand: 2 seconds
10. Terminal Connection System:
a. MV Side : cable sealing ends bolted from below.
b. LV Side : busbar termination box.
11. Low Losses Type.
L. Accessories are to include the following:.
1. Earthing switch, fault-making type, on MV side of housing interlocked
with door visible from outside the enclosure, with trip contact for
tripping MV circuit breaker before closing earthing switch.
2. Fans control for extra rating of transformer.
3. Four re-orientable roller rim wheels and attachment accessories.
M. Permissible overload capacity without undue heating shall be 20% for 1-1½
hours.
N. Winding temperature rise by resistance shall not exceed 100OC.
O. Each transformer shall be of double wound type with both the HV and LV
windings individually encapsulated in rigid steel mould. The coils shall be
impregnated with quartz filled epoxy resin and cast under vacuum, to
produce a smooth finish without voids and undulations.
P. The size and spacing of the conductors used in the windings shall be such
that the coils are self-supporting prior to impregnation and where
applicable, shall allow the epoxy resin to fill all of the space in and between
adjacent layers and turns.
Q. The coefficients of expansion of the windings and epoxy resin shall not
differ by more than 15%.
R. The windings shall be made of Aluminum.
S. A visible warning notice shall be fixed adjacent to the tapping links and
worded as follows:
" WARNING-OFF LOAD TAP CHANGING LINKS – ISOLATE HV
AND LV SUPPLIES TO TRANSFORMER BEFORE OPERATION"
T. Each distribution transformer shall be equipped with the following
accessories:
- Lifting lugs for complete transformer.
- Skid base with jacking and pulling provisions.
- Seismic ZA bolt down/chuking and anti-sway bracing.
- Two grounding pads on diagonally opposed sides for the base with bolt
type cable clamp adjustable for copper ground cables ranging from
95mm2 to 240mm2 for chassis grounding. One of the pads shall be
located at the side where the secondary neutral bushing is mounted.
6
- Fully enclosed cable end box on high voltage.
- Diagrammatic weatherproof stainless steel engraved or etched
nameplate. The nameplate shall show full rating of transformer, voltage
and tap ratios, impedance, weight vector diagram temperature class and
temperature rise, etc… and shall bear a connection diagram showing
studs, tap changers and other parts. Nameplate shall be in English.
- In addition to items listed hereinbefore, provide relaying and protection
as required in coordination with LV and MV circuit breakers.
- Forced ventilation fans.
- Transformer enclosure to suit the location and anticipated
environmental conditions. This shall provide a degree of protection not
less than IP 31 in compliance with IEC 60529.
-
2.03 TECHNICAL REQUIREMENTS
The requirements for Voltage other than 10.5 kV shall be modified as needed.
IEC Compliance 160076-11"Dry Type Transformers"
HV Supply System 3300V/6600V/10500V
- Number of Phases 3 Phase
- Fault Level (nominal design) 500 MVA
LV Supply System
- No-load Voltage 400V/3300V
- Number of Phases 3 Phase
- System Neutral 4 wire/3 wire
- Rating As shown on drawings
Supply Frequency (HZ) 50 Hz
HV Winding Connection Delta/Star
LV Winding Connection Star
Vector Group Reference As shown on drawings
Impedance at 75OC 6%
HV Tapping (%of no-loads volts) ±2.5%,±5%±,7.5%±
Method of cooling Forced for 40% extra rating
Secondary Voltage at:
- Full Load 400V/3300V
- No Load 400V/3300V
HV Insulation Level 12 kV
- Impulse kV peak 75 Bill (at 11 kV)
- Power Frequency (kV rms) 28 kV (at 11 kV)
Paint Finish Colot Manufacturer Standard
HV Conductor and Type Top entry xple cables
LV Conductor and Type Top entry busbar
Indoor or Outdoor Installation Indoor
Space Limitations Refer to layout drawings
Coil Material (HV) Aluminium
Coil Material (LV) Aluminium
7
PART 3- EXECUTION
3.01 INSTALLATION:
A. Locations and Layout: Exact locations and physical layout of equipment and
components may be varied as required to suit manufacture's design and as
approved, provided the required functions and operations are accomplished,
follow the identification of the units indicated on drawings exactly to ease
checking and building maintenance procedures.
B. Equipment Bases: Ensure that concrete bases and foundations provided for
installation of equipment are constructed in accordance with approved shop
and construction drawings and equipment manufacturer's drawings and that
holes for fixing bolts and provisions for passage of cables etc. are provided as
required.
C. Cable Trenches: Ensure that trench construction and covers provided for
installation of power and control cables are in accordance with approved shop
and construction drawings.
D. Built –In Items: Ensure that equipment supports, fixings and the like, and
sleeves for passage of feeders and cables which are to be built into concrete
foundations, bases, cable trenches or building structure are provided as and
when required and that they are properly installed.
E. Equipment: Install on concrete bases etc. and assemble completely plumb and
level, before grouting in holding-down bolts.
F. Supports and Terminations: Install all incoming and outgoing cable supports,
cable ends and termination fittings required for MV, LV and control cables
G. Relays: Set in accordance with manufacturer's instructions and the local
power authority requirements.
H. Earthing: ensure that earthing installation is as described in Division 16
Section "Earthing" of the Specification and/or as shown on the Drawings.
I. Temporary Lifting provisions: Remove temporary lifting eyes, channels
brackets and temporary blocking of moving parts from switchgear units and
components.
3.02 IDENTIFICATION.
A. Identify transformers and install wiring signs according to Division 16
Section "Basic Electrical Materials and Methods".
B. The power supply for the cooling fans shall be provided from the particular
transformer via a suitably fused switch. This switch shall bear the inscription
in yellow letters on a black background in both English and Arabic.
" WARNING - SUPPLY FOR TRANSFORMER COOLING FANS – DO
NOT SWITCH OFF"
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3.03 CONNECTIONS:
A. Tighten bus joint, connector and terminal bolts according to manufacturer's
published torque-tightening values. If manufacturer's torque values are not
indicated, use those specified in applicable Standards.
3.04 FACTORY TEST:
1. The Contractor shall be responsible for performing the Dry type
transformer factory test.
2. The Dry type transformer factory test shall be performed at the country of
origin the presence of the Client's, Electrical Consultant and Engineer's
representatives team. the team will comprise three representatives all
expenses are to be borne by the Contractor.
3. the contractor shall provide to the engineer a certified factory test report.
3.05 FIELD QUALITY CONTROL:
A. Equipment: Inspect equipment upon delivery to site and report any damage
to Engineer.
B. Components: Check component ratings, types, sizes and wiring connections,
including current and voltage transformers, fuses, switches instruments and
relays.
C. Manufacturer's instructions are to be followed under all circumstances.
Carry out and record measurement and tests recommended by the
manufacturer.
D. Test Objectives: To ensure transformer is operational within industry and
manufacturer's tolerances, is installed according to the contract Documents,
and is suitable for energizing.
E. Test Labeling: On satisfactory completion of tests for each transformer,
attach a dated and signed "Satisfactory Test" label to tested component.
F. Schedule tests and provide notification at least 7 days in advance of test
commencement.
G. Report: Submit a written report of observations and tests. Report defective
materials and installations.
H. Test: Include the following minimum inspections and tests according to
manufacturer's written instructions.
1. Inspect accessible components for cleanliness, mechanical and electrical
integrity and damage or deterioration. Verify that temporary shipping
bracing has been removed. Include internal inspection through access
panels and covers for dry-type transformers.
2. Inspect bolted electrical connections for tightness according to
manufacturer's published torque values.
3. Insulation Resistance: Perform meg-ohmmeter tests of primary and
secondary winding to winding and winding to ground.
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4. Duration of Each Test: 10 minutes.
5. Temperature Correction: Correct results for test temperature deviation
from 20 deg C standard.
6. Turns Ratio: Measure between windings at each tap setting. Measured
ratios deviating more than 0.5 percent from calculated or measured ratio
for an adjacent coil is not acceptable.
7. Winding Resistance: Measure for windings at nominal tap setting.
Measured resistance, deviating more than 1 percent, from that of
adjacent windings is not acceptable.
8. Test Failures: Compare test results with specified performance or
manufacturer's data. Correct deficiencies identified by tests and retest.
Verify that transformers meet specified requirements.
9. Any other tests required by the electrical power authority.
3.06 GROUNDING:
A. Comply with Division 16 Section "Grounding and Bonding" for materials
and installation requirements.
3.07 CLEANING:
A. On Completion of Installation, inspect components. Remove paint splatters
and other sports, dirt and debris. Repair scratches and mars on finish to match
original finish. Clean components internally using methods and materials
recommended by manufacturer.
3.08 ADJUSTING:
A. After installing and cleaning touch up scratches and mars on finish to match
original finish.
B. Adjust transformer taps to provide optimum voltage conditions at utilization
equipment throughout normal operation cycle of facility. Record primary and
secondary voltages and tap settings and submit with test results.
3.09 DEMONSTRATION:
A. Train Employer's maintenance personnel to adjust, operate, and maintain the
system installation
END OF SECTION 16350
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