APDRP SCHEME , WESCO
Technical Specification for 33KV Air Break Switch
PART 1: SCOPE AND CONDITIONS
1.
SCOPE
This specification covers the design, engineering, manufacture, testing, supply, delivery, off-loading
and performance requirements of 33kV, 200 amp, triple pole Gang Operated Air Break (G.O.A.B.)
Switches for outdoor installation on the 33kV distribution lines and substations WESCO.
The equipment offered shall have been successfully type tested and the design shall have been in
satisfactory operation for a period not less than two years on the date of bid opening. Compliance shall
be demonstrated by submitting with the bid, (i) authenticated copies of the type test reports and (ii)
performance certificates from the users.
However where the Bidder offers similar but not identical equipment to that which has been type tested,
the difference shall be stated in Test Certificate Schedule. Acceptance of the offered equipment and the
type test data presented shall be at the discretion of the Project Head
The Air Break Switches shall conform in all respects to highest standards of engineering, design,
workmanship, this specification and the latest revisions of relevant standards at the time of offer and the
Project Manager shall have the power to reject any work or material, which, in his judgement, is not in
full accordance therewith.
2.
STANDARDS
Except where modified by this specification, the Air Break Switches shall be designed, manufactured and
tested in accordance with the latest editions of the following standards.
IEC / ISO/ BS
Indian Standard
IEC 265 - Part 1
IS 9920 - Part 1 to 4
High Voltage Switches for rated voltages above 1kV
and up to and including 52kV
IEC 273
IS 2544
Post Insulators for systems with nominal voltage
above 1,000V
IEC 168
ISO 1460, BS 729
Title
Tests on indoor and outdoor post insulators of ceramic
materials or glass with nominal voltages greater than
1,000V
IS 2629, IS 4736
Hot Dip Galvanising
IS 2633
Method of testing uniformity on zinc coated articles
The Bidder may propose alternative standards, provided it is demonstrated that they give a degree of
quality and performance equivalent to or better than the referenced standards. Acceptability of any
alternative standard is at the discretion of the Project Head. The bidder shall furnish a copy of the
alternative standard proposed along with his bid. If the alternative standard is in a language other than
English, an English translation shall be submitted with the standard. In the case of conflict the order of
precedence shall be 1) IEC or ISO Standards, 2) Indian Standards, 3) other alternative standards.
This list is not to be considered exhaustive and reference to a particular standard or recommendation in
this Specification does not relieve the Contractor of the necessity of providing the Goods complying
with other relevant standards or recommendations.
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APDRP SCHEME , WESCO
Technical Specification for 33KV Air Break Switch
3.
SERVICE CONDITIONS
The service conditions shall be as follows:
•
maximum altitude above sea level
1,000m
•
maximum ambient air temperature
50°C
•
maximum daily average ambient air temperature
35°C
•
minimum ambient air temperature
•
maximum temperature attainable by an object exposed to the sun
60°C
•
maximum yearly weighted average ambient temperature
32°C
•
maximum relative humidity
100%
•
average number of thunderstorm days per annum (isokeraunic level)
•
average number of rainy days per annum
•
average annual rainfall
•
maximum wind pressure
4.
SYSTEM CONDITIONS
0°C
70
120
150 cm
94.3 kg/m²
The equipment shall be suitable for installation in supply systems of the following characteristics:
•
Frequency
•
Nominal system voltages
•
Maximum system voltages:
•
Minimum LV voltage
•
Nominal short circuit levels:
•
Insulation Levels:
50Hz
33kV
11kV
400/230V
33kV System
11kV System
LV System
36.3kV
12.1kV
476V
340V
1.2/50 µs impulse withstand voltage
(positive and negative polarity):
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33kV System
11kV System
25kA
12.5kA
33kV System
170kV
APDRP SCHEME , WESCO
Technical Specification for 33KV Air Break Switch
•
•
Power frequency one minute withstand
voltage (wet and dry) rms
Neutral earthing arrangements:
11kV System
75kV
33kV System
11kV System
LV System
70kV
28kV
2kV
33kV System
11kV System
LV System
solidly earthed
solidly earthed
solidly earthed
PART 2 : TECHNICAL
5.
RATINGS.
The air break switches shall have the following ratings:
Non Load
Break Switch
Load Break
Switch
Rated voltage
36kV
36kV
Normal continuous rating.
400A
400A
Short time rating: current rms (1 second)
16kA
16kA
40kA
40kA
Power frequency withstand voltage, one minute, dry and wet,rms
i) across isolating distance
ii) between phases and to earth
80kV
70kV
80kV
70kV
Impulse voltage withstand level, peak (1.2/50 µs wave)
i) across isolating distance
ii) between phases and to earth
195kV
170kV
195kV
170kV
1.3 times the
actual flash
over voltage
1.3 times the
actual flash
over voltage
Mainly active load breaking capacity
10A
400A
Transformer off-load current breaking capacity
6.3A
6.3A
Line charging current breaking capacity
6.3A
6.3A
Cable charging current breaking capacity
10A
10A
To be stated
by Contractor
40kA peak
peak
Power frequency puncture withstand voltage
Short circuit making capacity
6.
GENERAL CONSTRUCTIONAL FEATURES.
The air break switches shall have triple pole construction and shall be suitable for horizontal having a
three porcelain insulator manually operated rocking type arrangement. Alternative offers for rotating
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APDRP SCHEME , WESCO
Technical Specification for 33KV Air Break Switch
insulator type switches will also be considered. The recommended phase spacing is 1200mm centre to
centre.
6.1.
Operating Mechanism.
The operating mechanism shall be suitable for manual operation from ground level by one person with
ease and shall be so designed that all the three phases open or close simultaneously. The switches shall
be robust in construction and shall be protected against over travel or straining that may adversely affect
any of its parts. The load break switch shall be fitted with self-contained arc extinguishing devices e.g.
interrupter heads with independent manual operation.
An operating rod consisting of galvanised iron pipe of 30mm diameter and of about 6000 mm length
shall be provided for closing and opening operations.
6.2.
Galvanising.
All ferrous parts except springs shall be hot dip galvanised with heavy coating as specified in the
section on Surface Treatment in this specification.
6.3.
Contacts.
All the current carrying parts shall be made of tin plated electrolytic copper of 99.98% purity. The
contacts shall be silver plated to thickness of not less than 30 microns. The fixed (female) contacts shall
be spring loaded pressure type so as to ensure firm contact and proper alignment. The springs shall,
however, not carry any current.
Arcing contacts with spring assisted operation shall be provided. The arcing contacts shall open after
the main contacts and close before the main contacts.
6.4.
Base and Mounting.
A rigid base of galvanised steel channel of size approximately 75 x 40 x 6mm. shall be provided with
suitable holes, clamps and bolts for mounting firmly on steel structure. It shall be suitable for both
horizontal and vertical mounting.
6.5.
Padlocking
Suitable padlocking or other approved locking arrangement shall be provided for locking the operating
handle both in the ON and in the OFF position.
6.6.
Earthing Terminal.
Two earthing terminals having clamping bolts with a minimum diameter of 12mm, with nuts, washers
and spring washers shall be provided on the frame of each pole. The earthing terminals shall be of
electroplated brass and of adequate size to carry full short circuit current.
6.7.
Other Features.
• Live parts shall be designed to avoid sharp point edges and other corona producing surfaces as
far as possible.
• The switch blades shall be so assembled that all three phases operate in synchronism. Fixed guides
shall be provided for proper seating of the contacts even when a blade is out of alignment to a minor
extent.
• There should not be any play or backlash to produce non-uniform travel of the blades of the three
phases and all the three phases shall make simultaneous closing with good electrical contact.
• A suitable arrangement for accelerating the opening of contacts shall be provided to avoid excessive
sparking.
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APDRP SCHEME , WESCO
Technical Specification for 33KV Air Break Switch
• The G.O.A.B. switches shall be capable of withstanding in their closed position the dynamic and
thermal effects of the short circuit current specified in the section on Ratings. The switches shall be
so constructed that the blades do not open or close under the influence of a short circuit, gravity,
wind pressure, vibration, shocks or accidental breaking of the operating shaft.
7.
POST INSULATORS
High strength porcelain insulators shall be used for supporting and insulating the fixed contacts and the
moving blades. They shall be made of homogeneous material, with uniform glazing, free from cavities
and other flaws and have a high quality smooth finish. They shall withstand the maximum expected
static and dynamic loads to which the isolator may be subjected during its service life. They shall
conform to IEC 273 or IS 2544 and shall be subjected to all the tests provided in these standards and in
IEC 168.
The creepage distance of the insulators shall be suitable for the atmospheric conditions described in the
section on Service Conditions, but shall not be less than 25mm / kV. The protected creepage distance
shall be at least fifty percent of the total.
The Bidder shall quote the make, type of insulation material, metal fittings, creepage distance, protected
creepage distance along with cantilever, torsion, tension and compression strengths.
8.
TERMINATIONS
The equipment shall be supplied with electrical connection terminals of a size and rating appropriate for
all the duties, including overload duty specified for the equipment. The terminals shall be of the bimetallic type, suitable for connection of all aluminium alloy conductor (AAAC) or aluminium
conductor steel reinforced (ACSR). In general connections using palm type solderless sockets shall be
preferred. The proposed method of connection shall be stated in the offer and shall be subject to
approval by the Project Manager. Where the terminals are of the clamp type, they shall be suitable for
taking a range of conductors appropriate to the rating of the equipment.
All nuts, bolts, washers and spring washers required to complete the connection shall be supplied with
the equipment.
9.
TEMPERATURE RISE
The temperature rise shall not exceed the following figures when the switches are in continuous
operation, over ambient temperature of 50 deg.C
Part
Temperature Rise
Total Temperature
Copper Contacts
55oC
105oC
Terminals
40oC
90oC
Metal Parts
40oC
90oC
10.
TESTS
Type tests and routine tests shall be carried out and results given along with certification as appropriate
in the Technical Data Schedule and Test Certificates Schedule of this specification.
10.1.
Type tests.
The following type tests are required:
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APDRP SCHEME , WESCO
Technical Specification for 33KV Air Break Switch
• Visual examination;
• Verification of dimensions;
• Visible discharge test;
• Dielectric test (impulse and one minute power frequency withstand test, dry and wet);
• Temperature cycle test;
• Short time current and peak current withstand test;
• Mainly active load breaking capacity test;
• Transformer magnetising current breaking capacity test;
• Line charging current breaking capacity tes;.
• Cable charging current breaking capacity test;
• Short circuit making capacity test;
• Mechanical strength tests for post insulator as per IEC 168 / IS 2544;
• Operational and mechanical endurance test;
• Tests for galvanisation of ferrous parts;
• Porosity test on post insulators.
10.2.
Routine tests.
The following routine tests shall be conducted on each set and results are to be furnished for
consideration:
• Power frequency voltage dry test;
• Measurement of resistance of main circuit;
• Tests to prove satisfactory operation and mechanical strength;
• Dimension test;
• Visual Inspection test;
• Millivolt drop test.
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APDRP SCHEME , WESCO
Technical Specification for 33KV Air Break Switch
PART 3 : GENERAL PARTICULARS AND GUARANTEES
11.
COMPLIANCE WITH SPECIFICATION
The Air Break Switches shall comply in all respects with the requirements of this specification. However,
any minor departure from the provisions of the specification shall be disclosed at the time of tendering
in the Non Compliance Schedule in this document.
12.
COMPLIANCE WITH REGULATIONS
All the equipment shall comply in all respects with the Indian Regulations and Acts in force.
The equipment and connections shall be designed and arranged to minimise the risk of fire and any
damage which might be caused in the event of fire.
13.
Inspection and testing
The Project Manager shall have free entry at all times, while work on the contract is being performed, to all
parts of the manufacturer's works which concern the processing of the equipment ordered. The
manufacturer shall afford the Project Manager without charge, all reasonable facilities to assure that the
equipment being furnished is in accordance with this specification.
The equipment shall successfully pass all the type tests and routine tests referred to in the section on Tests
and those listed the most recent editions of the standards given in this specification.
The Project Manager reserves the right to reject an item of equipment if the test results do not comply with
the values specified or with the data given in the technical data schedule.
Type tests shall be carried out at an independent testing laboratory or be witnessed by a representative of
such laboratory or some other representative acceptable to the Project Manager. Routine tests shall be
carried out by the Contractor at no extra charge at the manufacturer's works.
Type Test certificates shall be submitted with the bid for evaluation. The requirement for additional
type tests will be at the discretion of the Project Manager.
The Project Manager may witness routine and type tests. In order to facilitate this, the Contractor shall give
the Project Manager a minimum of four weeks notice that the material is ready for testing. If the Project
Manager does not indicate his intention to participate in the testing, the manufacturer may proceed with the
tests and shall furnish the results thereof to the Project Manager.
Full details of the proposed methods of testing, including connection diagrams, shall be submitted to the
Project Manager by the Contractor for approval, at least one month before testing.
All costs in connection with the testing, including any necessary re-testing, shall be borne by the
Contractor, who shall provide the Project Manager with all the test facilities which the latter may require,
free of charge. The Project Manager shall have the right to select the samples for test and shall also have the
right to assure that the testing apparatus is correct. Measuring apparatus for routine tests shall be calibrated
at the expense of the Contractor at an approved laboratory and shall be approved by the Project Manager.
The Contractor shall be responsible for the proper testing of the materials supplied by sub-suppliers to
the same extent as if the materials were completed or supplied by the Contractor.
Any cost incurred by the Project Manager in connection with inspection and re-testing as a result of failure
of the equipment under test or damage during transport or offloading shall be to the account of the
Contractor.
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APDRP SCHEME , WESCO
Technical Specification for 33KV Air Break Switch
The Contractor shall submit to the Project Manager five signed copies of the test certificates, giving the
results of the tests as required. No materials shall be dispatched until the test certificates have been received
by the Project Manager and the Contractor has been informed that they are acceptable.
The test certificates must show the actual values obtained from the tests, in the units used in this
specification, and not merely confirm that the requirements have been met.
In the case of components for which specific type tests or routine tests are not given in this specification,
the Contractor shall include a list of the tests normally required for these components. All materials used in
the Contract shall withstand and shall be certified to have satisfactorily passed such tests.
No inspection or lack of inspection or passing by the Project Manager’s representative of equipment or
materials whether supplied by the Contractor or sub-contractor, shall relieve the Contractor from his
liability to complete the contract works in accordance with the contract or exonerate him from any of
his guarantees.
13.1.
Guarantee
The Contractor shall guarantee the following :
•
Quality and strength of materials used.
•
Satisfactory operation during the guarantee period of one year from the date of commissioning, or
18 months from the date of acceptance of the equipment by the Project Manager following
delivery, whichever is the earlier.
•
Performance figures as supplied by the Bidder in the Technical Data Schedule
•
The offered surface treatment shall protect the treated metal from corrosion for a period of not
less than five years from the date of delivery.
14.
SUBMITTALS
The following shall be required in duplicate :
• completed technical data schedule;
• descriptive literature giving full technical details of equipment offered;
• outline dimension drawing for each component, general arrangement drawing showing component
layout;
• type test certificates, where available, and sample routine test reports;
• detailed reference list of customers already using equipment offered during the last 5 years with
particular emphasis on units of similar design and rating;
• details of manufacturer's quality assurance standards and programme and ISO 9000 series or equivalent
national certification;
• deviations from this specification. Only deviations approved in writing before award of contract shall be
accepted;
• list of recommended spare parts for five years of operation with prices and spare parts catalogue with
price list for future requirements.
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