RFQ Number | Items Required | Qty | Date Posted | Closing Date | Closing time |
PR10241263
RQ2211297 |
Stay Rod 3/4 |
33
|
07/12/2022 | 12/12/2022 | 10:00 am |
|
Stay Bow 3/4
|
33 | |||
Stay Plate 3/4
|
33 | ||||
Stay Washer 3/4
|
33 | ||||
Stay Insulator 36kV | 33 | ||||
KINDLY FIND DETAILED SPECIFICATIONS ON OUR ZETDC WEBSITE |
1. Introduction-This Specification covers the manufacture, supply and delivery of line hardware and accessories for electrical distribution system. 2. Standards- Except where otherwise specified or implied, IEC Recommendation or British Standards (BS) where they amplify IEC, shall apply throughout. Any other standard provided the supplier can provide documentary evidence that the standard is equal to or better than the above standards. All tenderer’s correspondence and all descriptions upon drawings, illustrations or instructions shall be in the English language. SI unit of measurements shall be used throughout. The line hardware shall be manufactured to high quality standards. The companies manufacturing the units shall have ISO 9001 or 2 or Standard Association of Zimbabwe Certification and shall submit documentary proof thereof. 3. Detailed Specification General- All the line hardware specified herein shall be of a design suitable for 100mm2 ACSR conductors. Care shall be taken to ensure that all hardware and fittings supplied constitute complete assemblies. The minimum factor of safety for line hardware incorporated in insulator strings and other related to the guaranteed breaking load shall be 2.5kN. All materials, whether fully specified herein or not, shall be of first class quality and shall conform with the best modern practice and comply in all respects with these Specifications. All material shall be free from folds, cracks and other exterior and interior defects, which can affect its strength, ductility, durability or ability to function. All materials shall be inspected and tested in full to prove compliance with the requirements of the specifications. The testing shall be carried out according to the relevant standards like: BS 3288 Insulator and conductor fittings for overhead power lines. Part 2: Specifications for a range of fittings. ASTMA 153 Zinc coating (hot-dip) on Iron and Steel Hardware All iron and steel hardware shall be hot-dip galvanised to British or IEC standards. All bolts and nuts shall be made of stainless steel . Type test Certification shall be submitted for all major components certified by an internationally recognised test institute or laboratory, if the Supplier fails to submit such test certificates, the bid is liable to be rejected. 4. Part –1 Conductor Assessories 4.1 Conductor Ties (Wraplock Type)- The conductor ties should be equivalent in all respects to the respective products made by preformed and include a neoprene centre section and groove pad. They shall be suitable in all respects for the indicated usage, to tie conductors to the specified pin insulators. 4.2 Conductor Splices- Conductor splices shall be suitable for joining ACSR Conductors. Splices for conductor size 100mm2 shall be of the twisting or preform type. The failing load of the splice shall be at least 90% ultimate tensile strength of the conductor. 4.3 Conductor Armour Rods The Armour rods shall be of the preform type and will be used for reinforcing conductors at the supports. Armour rods for conductor 100mm2 ACSR shall be suitable for reinforcing conductors supported on pin insulators. 5. Part 2 –Clamps & Conductor Attachments 5.1 Parallel Groove (PG) Clamps The PG clamps are to be used for connecting 100mm2 ACSR conductors. The clamps are to be made of Aluminium Alloy with bolts nuts and washers of galvanised steel. The clamps shall be provided with two or more M12 bolts to provide good (tight) connection for conductor temperatures varying between – 100C and 800C. The clamps shall have a layer of oxide inhibiting grease on the inside the groves that will accommodate the conductor. 5.2 Strain Clamps The strain clamps shall be manufactured from malleable cast iron. They shall be suitable for 100mm2 ACSR conductors. The weight of each unit shall not exceed 3.1kg. The clamps shall be provided with a clevis for attachment to the disc insulators. Stainless steel pins and split pins and galvanised washers are to be provided for securing the clamp to the insulator. The clamps shall be rated for a minimum failing load of 70kN. The clamps shall unless otherwise preferably be of the wedge type with 3 sets of bolt clamps for securing the conductor. Due consideration shall be given to cold flow characteristics and contact area requirements of connectors and conductors. Bolts shall be used as clamping devices only and not as current carrying parts. All bolts nuts and washers shall be of high strength stainless steel. When installed, the assembly shall develop a holding force not less than 95% of the ultimate strength of the conductor without causing clipping, or damage to the conductor or any part thereof in accordance with BS 3288. The current carrying capacity of the tension clamp shall be equal to, or better than that of the conductor. The clamps shall be greased to prevent damages to the conductor against corrosion. The clamps shall preferably be suitable for a range of conductor sizes, in order to minimise the number of different varieties. 5.3 Suspension Clamps These will be used for conductors with diameters ranging from 11mm to 22mm. They shall be suitable for 100mm2 ACSR conductors. They shall be manufactured from malleable cast iron alloy. The minimum failing load shall be at least 70kN. The weight of each clamp shall not exceed 3.0kgs. 5.4 Wide Angle Suspension Clamps The suspension clamp attachments shall be the same as for the tension clamps. The same conductor cross-section as for the tension clamp shall also apply for the suspension clamp. The suspension clamp shall be light and free to pivot in the vertical plane. The pivoting centre shall be close to the conductor axis. The conductor groove shall be bell-mouthed at both ends. The groove shall be free of burrs and edges. It shall be tailored to suit the conductor for a turning angle of at least 25%. Clamping pressure on the conductor shall not be applied near the ends of the supporting groove of the clamp where conductor-bending stresses are high. Clamping bolts shall be provided with locking devices. The wide-angle clamps shall be suitable for use for conductor angles between 0 degrees and 25 degrees measured from the straight through axis and have a minimum failing load of 70 kN. 5.5 York Plates The York shall be suitable for both strain and suspension points. The york plates shall be manufactured from malleable cast iron or mild steel. They shall be hot- dip galvanised. The minimum failing load shall be at least 70kN and the weight of each unit shall not exceed 1.5kgs. 5.6 Clevis Adapters The clevis adapters shall be made of malleable cast iron to BS310. The minimum failing load shall be at least 70kN. The weight of each Unit shall not exceed 1.2kgs. 5.7 Arcing Horns/Arcing Horn Adapters The arcing horns shall be suitable for 33kV line and be of mild steel and have the necessary dimensions to reduce, as far as possible, damage when flash-over occurs. The arcing horn on the live end shall have sufficient diameter to prevent the cause of visible corona and/or radio interference. The arcing horn on the live end of the suspension sets shall withstand a mass of 150kg applied at the tip. The arcing horn adapter shall consist of an extended clevis tongue with single mounting hole suitable for the connecting of 25mm strap arcing horn by means of a single 12 mm bolt. The adapter shall be supplied with a stainless steel pin, washer and split pin. The arcing horns and mounting bolts shall be included included in the scope of supply. The adapters shall be rated for a minimum load of 70kN. The arcing horn adapters shall be made from castings and those made through any welding process will not be accepted. 6. Part 3-General Pole Top Hardware 6.1 Shackle Straps- The 5/8 twisted shackle straps shall be galvanized and shall be manufactured to relevant British Standards. 6.2 Steel Bracing-They shall be manufactured from flat steel and be hot-dip galvanised. 6.3 Wood Pole Washers-The M22 wood pole washers shall be manufactured from Malleable cast iron or mild steel. They shall be dip hot galvanised. The weight of each unit shall not exceed 0.3kgs. 6.4 Cross-arms-All parts shall be hot-dipped galvanised after all burrs are removed. 6.5 Fibre Glass Bracing-They shall be made of flame retardant resin. The ultimate tensile strength shall be at least 20 kN (2000 Kg force). 6.6 Spindles- All spindles and related parts shall be hot dip galvanized 6.7 Pole Top Brackets-These shall be used for 33kV lines. The dimensions are as shown on attached drawing. The pole top brackets shall be manufactures from flat bar cold bending during manufacture is not permissible. The pole top brackets shall be hot-dip galvanised to SABS 763 7. Part 4 Stays & Accessories 7.1 General The stay shall be 3/4” stay complete Stays shall be supplied complete with the following a) Stay plate b) Stay washer c) Stay rod d) Stay thimble e) Stay bow The complete stays shall be made according to the latest revision of relevant British Standard Specification were available. The stay rods, stay bows, base-plates and washers shall all be made of mild steel. All parts shall be hot-dipped galvanised after all burrs are removed. 7.2 Base Plate- Base plates shall be manufactured from mild steel plates and be hot dip galvanised. The thickness of each plate shall be at least 6mm. 7.3 Stay Washers- These shall be made of mild steel plate and be galvanised. The plate thickness shall be at least 6mm and each side shall be 150mm. The weight of each washer shall not exceed 1.0kg. 7.4 Stay Rods-These stay rods shall be manufactured to BS 16 Pattern 2. They shall be made of mild steel of Malleable cast iron to BS 309. They shall be hot dip galvanised. 7.5 Stay Thimble-The thimbles shall be made according to B.S 464 and shall be Hot-Dipped galvanized. 7.6 Stay bracket –The stay bracket shall be hot dip galvanized and be made of mild steel flat bar. Cold bending during manufacture is not permissible. |
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SPECIFICATION FOR INSULATORS |
1. Scope- This specification covers the manufacture, testing, supply and delivery of insulators.
2. Standards- All insulator types shall comply with the latest edition of the relevant IEC publication or British Standards where they amplify IEC. The reference standards shall be stated in the Technical Schedules appended to these Specifications.
Relevant IEC Standards are:
- a) IEC Publ. 60 – High voltage testing techniques
- b) IEC Publ. 168-Tests on indoor and outdoor post insulators
- c) IEC Publ. 305 -Characteristics of string insulator units of the cap and pin type.
- d) IEC Publ. 383- Tests on insulators of ceramic material or glass for overhead lines with nominal voltage greater than 1000V.
- e) IEC Publ. 383- Radio interference test on high voltage insulators
- f) IEC Publ. 575 -Thermal-mechanical performance test and mechanical performance test on string insulator units.
- g) IEC Publ. 672-Specification for ceramic and glass insulating materials
- h) IEC Publ. 720 -Characteristics of line post insulators
- i) IEC Publ. 797 -Residual strength of string insulator units of glass or ceramic material for overhead lines after mechanical damage of the dielectric.
- j) ISO/R 1101/1, 1969 -Tolerances of form and position. Part I: Generalities, symbols indication on Drawing
The insulators shall be provided from companies who have ISO 9001/2 certification.
3. General Design
All insulators types shall be brown glazed porcelain of a sound quality, free from defects and thoroughly vitrified so that the glaze is not depended upon for insulation. The glaze shall be smooth, hard of a uniform shade of brown and shall cover the entire exposed part of the insulator. The insulators shall be unaffected by atmospheric conditions due to weather, fumes, ozone’s, acids, alkalis, dust or rapid changes of temperature between minus 100 C and plus 500 C under working conditions.
The porcelain shall not engage directly with hard metal and, where necessary, an approved resilient material shall be interposed between porcelain and end fittings.
All fixing material used shall be of approved quality and shall not enter into chemical action with the metal parts or cause fracture by expansion during service. Where cement is used as a fixing medium, the thickness of cement shall be as small and even as possible and proper care shall be taken to center and locate the individual parts correctly during cementing.
All insulators shall comply with technical requirements listed in table 1. The insulators shall have a design life of at least 40 years when operating under the specified conditions (1.1 and 1.2) This shall be verified through accelerated life cycle tests.
The total creepage distance and the protected creepage distance over the external surface of the insulators shall not be less than the minimum values specified. The protected creepage distance refers to that part of the insulators which is protected against rain at right angles to the axis of the insulator.
The design of insulators and fittings shall be such as to avoid local corona formation and no significant radio interference shall be exhibited. The insulator units conform to the electrical and mechanical design criteria stated in the technical tables in this Specification.
Wherever galvanising is specified, the galvanising shall be by the hot dip process with a minimum zinc layer of 610g/m2. The insulators shall be as per attached drawings.
3.1 Pin Type Insulators
The pin types insulators for 33kV overhead lines shall be of a design which accommodates threaded large steel spindle heads according to British Standard No. 137, Ref. No. 16. Threaded zinc thimbles to fit large steel head pins are to be supplied as part of the complete insulator assembly. Alternatively cast lead-antimony alloy thimbles may be offered. The pin insulators shall be suitable for ACSR and all Aluminium conductors with overall diameters ranging from 5 to 15mm. It shall be possible to secure the conductor on the neck as well as on the top grove.
3.2 Insulator Pins
The insulator pins shall be hot dip galvanised, of the large steel head type and have a minimum failure load of 5kN. The pins shall be complete with galvanised washers and nuts and fit, the pin insulators specified above.
3.3 Disc Insulators
The disc insulators shall be of the Clevis and Tongue and unless otherwise specified in the Schedule of Requirements be fitted with tongue and clevis supplied complete with stainless steel pin, washer and split pin for the clevis.
Cap and clevis shall be made of malleable cast iron, spheroidal graphite cast iron or forged steel. The graphite in malleable cast iron shall only appear in the form of temper carbon and the graphite cast iron shall only be present in spheroidal form.
The tongue shall be made of forged steel. In tensile tests the tongue shall exhibit ductile fractures characterized by a considerable contraction of area.
Cap, clevis and tongue shall be hot-dip galvanised.
The verification of dimensional requirements of the insulator units shall be as stated below. Insulating part, cap and pin shall be concentrically assembled using Portland cement or aluminous cement.
When gripping the insulator between a tongue (dummy) and clevis end (dummy), the radial run-out of the insulating part shall not exceed 3% of the nominal insulator diameter.
With the same arrangement, the axial run-out of the insulating part shall not exceed 4% of the nominal insulator diameter. The axial run-out shall be measured at the periphery of the insulating part. For definitions, see ISO/R 1101/1, 1969.
Assembly shall be performed in such a way that the mechanical properties cannot be affected by the zinc and to ensure that the insulating part is not subject to any mechanical stress due to pressure exerted by the bottom edge of the cap.
Free surface of insulating parts shall be cleaned from cement and other impurities. The verification of the locking system shall be performed in accordance with IEC 383.
3.4 Stay Insulators
The stay insulators shall be used for the purpose of insulating the galvanised steel wire giving mechanical support to the distribution lines. They shall be symmetrical to allow for even load distribution and have rounded heavy sections to protect against damage.
The stay insulators are to allow steel wire ropes with diameters ranging from 10 to 30mm.
4. Testing
The Supplier shall submit type test reports for all insulator types.
The type test reports shall be certified by an international reputable test institute or laboratory.
Electromechanical or mechanical failing load test shall be performed in accordance with IEC 383, amended as follows: The test load shall be increased from an initial value which is equal to about 75% of the specified minimum failing load to a rate of 15 to 30% of this failing load per minute. In the electromechanical failing load test, it is required that puncture shall not occur before mechanical breakdown. Before the electromechanical failing load or mechanical failing load test, the insulators shall have passed the temperature cycle test specified in IEC 383.
Residual strength test in accordance with IEC 797 shall be performed on insulators with a shattered insulating part. The failing load shall be at least 65% of the value obtained at the electromechanical or mechanical failing load test. The Supplier shall provide details of accelerated life cycle tests carried out on the insulators. Type test certificates shall be submitted for any tests carried out.
5. Packing
Insulator units shall be packed in crates.
The crates shall be packed on pallets and each pallet shall contain 20 crates.
The packing shall afford adequate protection for the insulators during ordinary handling and shipping.
The Contractor shall make sure that split-pins operate properly and that they are placed in locking position.
Each package shall be marked with the type designation used by the manufacturer.
33kV Pin Insulators Item | Unit | Value |
Highest system voltage | kV | 36 |
Total Creep age Distance | mm | 650 |
Cantilever Strength | kN | 10 |
Power Frequency Flashover voltage-dry | kV | 110 |
Power Frequency Flashover voltages-wet | kV | 85 |
Impulse Flashover voltage – Positive | kVp | 205 |
Impulse Flashover voltage – Negative | kVp | 225 |
Impulse Withstand voltage – Positive | kVp | 180 |
Impulse Withstand voltage – Negative | kVp | 190 |
Power Frequency Puncture Voltage | kV | 200 |
One minute Power Frequency Withstand voltage – dry | kV | 100 |
One minute Power Frequency Withstand voltage – wet | kV | 80 |
Maximum weight | kg | 8.5 |
END