FEWA-PL-SS-E-0054 REV.0
TECHNICAL SPECIFICATION
(AUXILIARY TRANSFORMER)
08 - FEWA-PL-SS-E-0054 REV.0, AUX. TRAFO.
TABLE OF CONTENTS
Page
1.0
DESIGN REQUIREMENTS ..................................................................................... 3
2.0
TYPE OF TRANSFORMERS .................................................................................. 3
3.0
VOLTAGE CONTROL ............................................................................................. 3
4.0
ELECTRICAL CONNECTIONS ............................................................................... 3
5.0
COOLING SYSTEM ................................................................................................ 3
6.0
FITTINGS ................................................................................................................ 3
7.0
TESTS .................................................................................................................... 4
7.1
TYPE TESTS .......................................................................................................... 4
7.2
ROUTINE TESTS.................................................................................................... 4
VOL IV
AUX. TRANSFORMER
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08 - FEWA-PL-SS-E-0054 REV.0, AUX. TRAFO.
1.0
DESIGN REQUIREMENTS
The transformers shall be designed to ensure satisfactory continuous operation under the
site and system conditions specified in Volume II, in which the maximum oil and winding
temperature rise shall not exceed 45oC and 50oC respectively above site ambient
temperature of 50oC.
The transformers shall comply with International Standards and requirements specified for
power transformers in section 3.1 as appropriate, for the type and fittings specified herein.
2.0
TYPE OF TRANSFORMERS
The transformers shall be outdoor, oil immersed, ONAN core type, either with conservator or
hermetically sealed type. The rating of the transformer shall be as per the schedule of
requirement and scope of supply.
The transformer shall be capable of carrying their full rated power specified at all taps
continuously under the maximum temperature conditions encountered in UAE.
3.0
VOLTAGE CONTROL
The transformer shall be provided with OFF - CIRCUIT taps of range ± 5% in steps of 2.5%
on the HV windings. The voltage rating for HV and LV windings shall be as per the schedule
of requirement and scope of supply.
4.0
ELECTRICAL CONNECTIONS
Cable boxes shall be provided on HV and LV sides suitable for heat shrinkable terminations
of XLPE cables. The minimum size of cable to be connected on HV side is 185 mm 2 and on
LV side is 2x800 mm2 copper/XLPE cable.
5.0
COOLING SYSTEM
The transformers shall have radiators welded to the tank. Cooling tubes and radiators shall
be so designed as to avoid pockets in which moisture, dust or sand may collect. They shall
withstand the pressure tests appropriate to the main tank.
6.0
FITTINGS
The transformer fittings shall include the following:
i)
Conservator vessel with oil filling hole and cap.
VOL IV
ii)
Over pressure relief valve with contact for control/indication.
iii)
Breather designed for local 100% humidity conditions.
iv)
Magnetic oil level gauge.
v)
Main tank drain valve and plug
vi)
Dial type thermometer with maximum reading pointer for measuring oil
temperature with contact for alarm purpose.
AUX. TRANSFORMER
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08 - FEWA-PL-SS-E-0054 REV.0, AUX. TRAFO.
vii)
Thermometer pocket for measuring oil temperature.
viii)
Rating and diagram plates as per the latest relevant IEC requirements.
ix)
Lifting eyes for lifting of core.
x)
Tank earthing terminals.
xi)
Lifting lugs for lifting of whole transformer.
The above fittings and accessories shall comply with the relevant clauses detailed elsewhere
in section 3.1.
Each 33/0.415 kV and 11/0.415KV transformers shall also include an outdoor type CT
connected into the neutral earth conductor for 415V restricted earth fault protection. The CT
requirements shall be based on detailed design and shall be co-ordinated with the
requirement arising from the control and protection system design requirements prepared by
other contractor.
7.0
TESTS
7.1
Type Tests
Test certificates shall be presented for :
-
Temperature rise test
-
Impulse-voltage withstand (full wave).
If type test certificates pertaining to the same or similar transformers are not submitted along
with the offer, the Authority reserves the right to request the contractor to carry out the above
tests in the presence of the Authority’s Engineers without any extra cost.
7.2
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Routine Tests
-
Measurement of winding resistance
-
Ratio, polarity and phase relationships
-
Measurement of loss
-
Short duration power frequency voltage withstand test
-
Induced over voltage withstand test
-
Insulation resistance of each winding.
-
Oil leakage test.
AUX. TRANSFORMER
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