tanesco tanzania - specification s24 mv load break fuse cutouts with arc chutes (2000)

AMG/TANZANIA/SPECS/S24

TANZANIA ELECTRIC SUPPLY COMPANY LIMITED

SPECIFICATION S24

DISTRIBUTION MV LOAD BREAK FUSE CUTOUTS WITH ARC CHUTES

DROP OUT TYPE

AUGUST 2000.

TANZANIA ELECTRIC SUPPLY COMPANY LIMITED

Samora Avenue, P.O. Box 9024, Dar es Salaam, Tanzania.

Telephone: +255-22-2111041/4 or 2114045/6

Facsimile: +255-22-2113836 or 2114981or 2110825

PECS/S24

Specification S24 - Distribution MW Fuse Cutouts

TABLE OF CONTENTS

PART 1: GENERAL 1. SCOPE................................................................................................ S24-1

2. STANDARDS ................................................................................... S24-1

3. SERVICE CONDITIONS................................................................. S24-4

4. SYSTEM CONDITIONS.................................................................. S24-5

5. INSPECTION, TESTING AND QUALITY ASSURANCE ......... S24-6

5.1 Inspection ........................................................................................... S24-6 5.2 Testing ................................................................................................ S24-6 5.3 Quality Assurance.............................................................................. S24-8

6. SPARE PARTS.................................................................................. S24-8

7. PACKING AND SHIPPING ............................................................ S24-8

7.1 Packing ............................................................................................... S24-8 7.2 Shipping.............................................................................................. S24-9 7.3 Hazardous Substances ..................................................................... S24-10

8. SUBMITTALS ................................................................................ S24-10

8.1 Submittals required with the Bid..................................................... S24-10 8.2 Submittals required after tender award ........................................... S24-12

PART 2: TECHNICAL 9. GENERAL ....................................................................................... S24-13

9.1 Design............................................................................................... S24-13 9.2 Guarantee ......................................................................................... S24-14

ii

PECS/S24


10. RATED FREQUENCY................................................................... S24-15 11. RATED VOLTAGE........................................................................ S24-15

12. INSULATION LEVEL ................................................................... S24-15

13. CURRENT RATING ...................................................................... S24-16

14. RATED INTERRUPTING CAPACITY ....................................... S24-16

15. LOW CURRENT INTERRUPTION ............................................. S24-16

16. TEMPERATURE RISE LIMITS ................................................... S24-17

17. FUSE LINK RANGE AND CLASS.............................................. S24-17

18. INTERCHANGEABILITY ............................................................ S24-17

19. INSULATORS................................................................................. S24-17

20. RADIO INFLUENCE VOLTAGE ................................................ S24-18

21. CLEARANCES ............................................................................... S24-18

22. CREEPAGE DISTANCE ............................................................... S24-18

23. MAIN ASSEMBLY ........................................................................ S24-19

24. FUSE TUBE ASSEMBLY ............................................................. S24-20

25. FUSE LINKS................................................................................... S24-20

26. OPERATING TOOLS .................................................................... S24-22

27. TESTS .............................................................................................. S24-23

27.1 Routine Tests.................................................................................... S24-23 27.2 Type Tests ........................................................................................ S24-23 27.3 Corrosion Performance Tests .......................................................... S24-24

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PECS/S24


28. SCHEDULES .................................................................................. S24-25 28.1 Technical Data Schedule: Load Break Fuse Cutouts..................... S24-25 28.2 Technical Data Schedule: Fuse Links............................................. S24-28 28.3 Non Compliance Schedule .............................................................. S24-29 28.4 Test Certificates Schedule ............................................................... S24-30

PART 3: INSTALLATION

29. INSTALLATION ............................................................................ S24-31

APPENDICES

Figure 1: Porcelain Distribution MV Load Break Fuse Cutout with arc chute ................................................................................... S24-32

Figure 2: Fuse Links ........................................................................ S24-33

Figure 8 of Specification S13: Type X Extended Bracket ........ S24-34

Figure 3: Typical 11kV Surge Arrester ......................................... S24-35

Figure 4: Typical 33kV Surge Arrester ......................................... S24-36

ivi

Specification S24 - Distribution MV Fuse Cutouts

PART 1: GENERAL

1. SCOPE

This specification covers the design, manufacture, testing, supply, delivery and performance requirements of dropout, expulsion type, distribution MV Load break fuse cutouts and fuse links for use in the networks of the Tanzania Electric Supply Company Limited.

Any departure from the provisions of this specification shall be disclosed at the time of tendering in the Non compliance schedule, in part 2 of this document.

2. STANDARDS

The equipment shall comply with the latest editions of, and amendments to, the international standards listed below. Where any provision of this specification differs from those of the standards listed below, the provisions of this specification shall apply:

ANSI American National Standards Institute:

o C37.40: Service conditions and definitions for high-voltage fuses,

distribution enclosed single-pole air switches, fuse disconnecting switches, and accessories.

o C37.41: Design tests for high-voltage fuses, distribution enclosed

single-pole switches, fuse disconnecting switches and accessories.

o C37.42: Specifications for distribution cutouts and fuse links.

BSI British Standards Institution:

o BS 729: Specification for hot dip galvanized coatings on iron and steel articles.

European Union Commission:

o SI 426: European Communities (dangerous substances)

(classification, packaging, labelling and notification) regulation, 1992

S24-1


IEC International Electrotechnical Commission:

o IEC 60: High-voltage test techniques.

o IEC 60-2: High-voltage test techniques. Part 2: Measuring systems.

o IEC 282: High-voltage fuses

o IEC 282-2: High-voltage fuses. Part 2: Expulsion and similar fuses.

o IEC 383: Insulators for overhead lines with a nominal voltage above 1000 V.

o IEC 437: Radio interference test on high-voltage insulators.

o IEC 507: Artificial pollution tests on high-voltage insulators to be

used on a.c. systems.

o IEC 694: Common clauses for high-voltage switchgear and controlgear standards.

ISO International Organization for Standardization

o ISO 9000: Quality management and quality assurance standards -

Guidelines for selection and use.

NEMA National Electrical Manufacturers Association:

o SG2: High-voltage fuses.

S24-2


Associated specifications (to be used by Tanesco employees only):

o S01: General technical requirements of 33kV, 11kV and LV

networks.

o S13: Crossarms and associated steelwork.

o S15: Line fittings.

o S16: Bare and PVC covered conductors.

o S35: Bolts, nuts and washers.

The bidder may propose alternative standards, provided it is demonstrated that they give a degree of quality and performance equivalent to that of the referenced standards. Acceptability of any alternative standard is at the discretion of Tanesco.

S24-3


3. SERVICE CONDITIONS

The service conditions shall be as follows:

o altitude (above sea level) 1,600m

o maximum outdoor temperature 40 C

o minimum outdoor temperature 10 C

o maximum monthly mean temperature 35 C

o annual mean temperature 22 C

o maximum relative humidity 60 % to 96 %

o isokeraunic level tropical

o maximum wind velocity 58km/h

o prevailing wind direction SE and NW

o type of atmosphere coastal

Environmentally, the region where the work will take place is a coastal area, subject to an overall medium relative humidity, which can give rise to condensation. Onshore winds are frequently salted laden. On occasions, the combination of salt and condensation may create pollution conditions for outdoor insulators.

Therefore, outdoor material and equipment shall be designed and protected for use in exposed, polluted, salty, corrosive and humid coastal atmosphere.

Indoor material and equipment shall be designed and protected for use in buildings, which occasionally may be wet and damp.

S24-4


4. SYSTEM CONDITIONS

The equipment shall be suitable for installation in supply systems of the following characteristics:

o frequency

o nominal system voltages

50Hz

33kV 11kV

400/230V

o maximum system voltages: 33kV 11kV

36kV 12kV

o maximum LV voltage 440/253V

o minimum LV voltage 374/215V

o nominal short circuit levels 33kV 11kV

16.5kA 25kA

o insulation levels:

1.2/50s impulse (Positive and negative polarity) 33kV 170kV

11kV 75kV

Power frequency (one minute withstand, wet33kV 70kV

11kV LV

28kV 3kV

o neutral earthing arrangements: 33kV effectively earthed 11kV effectively earthed

LV effectively earthed

o creepage distance 30mm/kV (of maximum system voltage)

S24-5


5. INSPECTION, TESTING AND QUALITY ASSURANCE

5.1 Inspection

The manufacturer shall submit a detailed program covering the design, manufacture and testing of the equipment within one month of receipt of the tender award.

Reports shall subsequently be submitted to Tanesco at intervals, outlining progress and, if necessary, explaining deviations from the program.

The Tanescos representative 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 Tanescos representative, without charge, all reasonable facilities to satisfy himself or herself that the equipment being furnished is in accordance with this specification.

5.2 Testing

The equipment shall successfully pass all the type tests and routine tests referred to in part 2 and those listed in the most recent edition of the standards given in clause 2 of this specification.

The Tanescos representative 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 Tanesco. Routine tests shall be carried out at the manufacturer's works.

Type tests may be dispensed with at the Tanesco's discretion if the manufacturer furnishes evidence to Tanesco's satisfaction that the relevant tests have already been performed on identical equipment. In this case test certificates shall be submitted with the bid for evaluation.

S24-6


Tanesco shall have the tests witnessed by a representative, if desired. In order to facilitate this, the supplier in collaboration with the manufacturer shall give Tanesco a minimum of four weeks notice that the material is ready for testing. If Tanesco does not indicate her intention to participate in the testing, the manufacturer shall carry out the tests and the supplier shall furnish the results thereof to Tanesco one month before delivery of the materials.

Full details of the proposed methods of testing, including connection diagrams, shall be submitted to Tanesco by the manufacturer in collaboration with the supplier for approval, at least one month before testing.

All costs in connection with the testing shall be borne by the manufacturer who shall provide the Tanescos representative with all the test facilities, which the latter may require, free of charge. The Tanescos representative shall have the right to select the samples if he or she so desires and shall also have the right to satisfy himself or herself that the testing apparatus is correct.

The manufacturer in collaboration with the supplier shall submit to Tanesco five signed copies of the test certificates, giving the results of the tests as required. No materials shall be dispatched until the Tanescos representative has received the test certificates and the supplier 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.

The Tanescos representative shall have the equipment inspected after reception and he or she shall have the right to select the samples if desired. The supplier shall cooperate with this inspection and shall provide the Tanescos representative, free of charge, all the facilities, which the latter may require.

In the case of components for which specific type tests or routine tests are not called for in part 2 or in the quoted standards in clause 2 of this specification, the supplier shall include a list of all tests he or she proposes the manufacturer to carry out.

S24-7


5.3 Quality Assurance

The supplier shall provide current certification showing the manufacturer's compliance with ISO 9000 or equivalent national standard.

6. SPARE PARTS

The bid shall include, if any a comprehensive list of all consumable and non consumable spare parts and accessories, necessary for five years of normal operation as specified by the manufacturer.

The bidder shall give an assurance that spare parts will continue to be available through the life of the equipment.

The spare parts shall be clearly identified and related to the specific equipment item. Spare parts shall be delivered suitably packed and treated for long periods in storage. Each pack shall be clearly and indelibly marked with its contents, including a designation number corresponding to the spare parts list in the operation and maintenance instructions. All spare parts shall be stored in Tanesco Central Store.

7. PACKING AND SHIPPING

7.1 Packing

Each single-phase cutout shall individually be packet in a strong box and totally sealed in polythene bags to avoid deterioration by seawater, moisture or ingress of foreign matter.

After that the individual cutouts shall be packed and securely clamped against movement in robust, wooden, non-returnable packing cases to ensure safe transit from the manufacturer's works to the Tanescos Central Store.

The packing shall provide suitable protection against all climatic conditions prevailing during transport and on site.

All accessories shall be carefully packed so that they are fully protected during transport and handling operations and in storage.

S24-8


Internal surfaces of loose accessories shall be sealed off by means of gaskets and blanking off plates. Equipment and surfaces liable to deterioration due to condensation shall be protected by packs of silica gel or other approved desiccant.

Each packing case shall be indelibly marked, in two adjacent sides and on the top, with the following:

o individual serial number; o client's name, that is Tanzania Electric Supply Company Ltd.; o tender number; o name and address of manufacturer's agent in Tanzania; o manufacturer's name; o description of contents; o country of origin; o case measurements; o gross and net weights in kilogrammes; and o all necessary slinging and stacking instructions.

Each case shall contain a fully detailed packing list in a sealed waterproof envelope. Five copies of each packing list shall be sent to Tanesco prior to dispatching the equipment.

7.2 Shipping

The manufacturer in collaboration with the supplier shall be responsible for the shipping of all plant and equipment supplied from abroad to the ports of entry and for the transport of all goods to Tanesco Central Store; and for all the costs and expenses resulting from it, including customs clearance, offloading, warehousing and insurance.

All transport accessories, if any such as riding lugs, jacking pads, blanking off plates, etc. shall become the property of Tanesco.

All items of equipment shall be securely clamped against movement to ensure safe transit from the manufacturer's facilities to the Tanesco Store.

All accessories shall be carefully packed so that they are fully protected during transport and handling operations and while in storage.

S24-9


The supplier shall advise, if requested, the storage required for any plant and equipment that may be delivered to the Tanesco's stores. The supplier shall be required to accept responsibility for the advice given, in so far as these arrangements may have a bearing on the behaviour of the equipment in subsequent service.

7.3 Hazardous Substances

The manufacturer in collaboration with the supplier shall submit safety data sheets for all substances used with the equipment. These substances shall be classified in accordance with the European Union SI 426: European Communities (dangerous substances) (classification, packaging, labeling and notification) regulation, 1992, or any subsequent amendment.

The manufacturer in collaboration with the supplier shall give an assurance that there are no other substances classified as hazardous in the equipment supplied. The manufacturer in collaboration with the supplier shall accept responsibility for the disposal of such hazardous substances, should any be found.

The manufacturer in collaboration with the supplier shall also be responsible for any injury resulting from hazardous substances.

8. SUBMITTALS

Some technical documentation is required as set out in clauses 8.1 and 8.2 below:

8.1 Submittals required with the Bid

The following shall be required:

o completed technical data schedule, this is non-negotiable;

o descriptive literature, including original brochure giving full

technical details of equipment offered. Specifically, the bidder shall completely describe the composition of the fusible element and of the tube surrounding it and its resistance to compression, collapse or twisting when being installed, and degree of swelling when wet;

S24-10


o outline dimension drawing for each major component and general

arrangement drawing showing component layout and connections and the dimensioned requested in page S24-32;

o time-current characteristics of fuse links for the ratings offered and

information on the extent that the time-current characteristics change over time, making fuse links unreliable on overload;

o general drawing showing the distribution MV load break fuse

cutout with arc chute mounting arrangement in a single pole and a double pole line;

o comment on whether it is an accepted good practice among utilities

to apply the fuse cutouts for load breaking duties listed in clause 9 of this specification. Should any of these applications be forbidden the bidder shall make this clear;

o information on the precautions to be taken to avoid damage to the

fuse link;

o a sample of a fuse link;

o safety data sheets for all substances used with the equipment;

o type test certificates, where available, and sample routine test reports;

o guarantee of the products;

o detail drawing of the bracket offered;

o detailed reference list of customers already using equipment

offered with particular emphasis on units of similar design and rating;

o International or national certificate of manufacturer's quality

assurance; and details of manufacturers quality assurance standards programme; and

o deviations from this specification. Only deviations approved in

writing before award of tender shall be accepted.

S24-11


8.2 Submittals required by Tanesco after tender award:

The following shall be required:

o program for production and testing;

o detailed assembly instructions within each packing case for each fuse cutout;

o a training video, incorporating installation, operation and

maintenance of the plant item; and

o five bound folders with records of the technical particulars relating to the equipment. The folder shall contain the following information:

* general description of the equipment and all components,

including original brochures;

* technical data schedule, with approved revisions;

* detailed dimension drawing for all components and general arrangement drawing showing detailed component layout and connections;

* time-current characteristics of fuse links for the ratings offered

* statement drawing attention to all exposed points in the

equipment at which aluminium or aluminium alloy parts are in contact with or in close proximity to other metals and stating clearly what protection is employed at each point to exclude air and moisture;

* inspection and test reports carried out in the manufacturer's

works;

* detailed installation and commissioning instructions; and

* operation and maintenance instructions, as well as trouble shooting charts.

S24-12


PART 2: TECHNICAL

9. GENERAL

9.1 Design

This specification covers the design, manufacture, testing, supply, delivery and performance requirements of 33kV and 11kV pole mounted, single pole, rod operated, field renewable, dropout, expulsion type, distribution MV fuse cutouts and fuse links for use in the 33kV and 11kV lines of Tanzania Electric Supply Company Limited.

The fuse cutouts shall be capable of being opened on load by means of a built in load-breaking device of an arc chute type. Figure 1 illustrates a typical MV load break fuse cutout with Arc Chute type interrupter.

In general, the fuse cutouts will be installed at branch poles or for the protection of distribution ground mounted and pole mounted transformers and for the protection of small power factor correction pole mounted capacitors. The fuse cutouts offered shall be class 2 as defined in IEC 282-2.

The size of ground mounted transformers in Tanescos networks varies between 315kVA and 1,250kVA. The size of pole mounted transformers varies between 50kVA and 315kVA (three phase) and between 5kVA and 25kVA (single phase). The maximum load current of branch lines is 153A and the standard size of pole mounted capacitor banks is of 600kVAr.

The bidder shall confirm or otherwise that it is an accepted good practice among utilities to apply the fuse cutouts offered for the load breaking duties listed above. Should any of these applications be forbidden the bidder should record this on the technical data schedule.

The distribution MV load break fuse cutouts offered shall be in accordance with IEC 282-2 or ANSI C37.41 and C37.42. Other equivalent standards may also be considered.

For easy mounting of the fuse cutout and surge arrester on a standard auxiliary crossarm, the complete mounting assembly, shall include the type X extended N.E.M.A bracket c/w bolts, nuts and washers; with an additional extension above, to give enough clearance between the mild steel crossarm & the arrester.

S24-13


The X extended N.E.M.A bracket is a little bit longer (65mm) than the N.E.M.A type B bracket. Figure 8 in TANESCO specification S13: Crossarms and associated steelwork represents a typical type X extended N.E.M.A bracket with an additional extension above. The same figure is also attached in this specification for easy reference, see page 34.

Typical 11 kV and 33 kV surge arresters intended to be used by Tanesco are represented in page 35 and page 36 respectively. Both 11kV and 33kV surge arresters will also be mounted horizontally on the bracket mentioned above. However, 33 kV surge arresters may preferably be installed vertically on a crossarm parallel to the MV load break fuse Cutouts.

The distribution MV load break fuse cutouts described in this specification are intended to correspond to typical, expulsion type fuse cutout devices, similar to those already used in TANESCO's networks in order to take advantage of the familiarity of the Tanescos staff with this kind of equipment.

However, the bidder is free to propose alternative equipment provided there is no reduction in the operating characteristics required. Indeed Tanesco may be well disposed to alternatives with enhanced operating characteristics, such as load break fuse cutouts, which would avoid the necessity of operators having to use load breaking tools; or fuse cutouts in which all three fuse tubes drop at the same time when one or two fuse elements melt as a result of an earth fault or a two phase short circuit.

However, since the price might be a critical element in bid evaluation, the bidder shall present the basic offer separately with an alternative offer.

A small number of distribution MV fuse cutouts may be installed in locations at an altitude between 1,000m and 1,600m. The bidder shall take this into account, in accordance with IEC 282-2, when considering the basic impulse level and the rated maximum voltage required.

A de-rating of the continuous current rating of the load break fuse cutouts due to altitude, along the lines of IEC 282-2, will be acceptable, but the de- rating factor shall be given in the technical data schedule.

9.2 Guarantee

All products shall be guaranteed in writing, against all defects arising from faults in design, material and workmanship. The guarantee period

S24-14


shall not be less than twelve (12) months from commissioning date or eighteen (18) months from the delivery date. This period shall be extended to five (5) years to cover all defects attributable to inadequate corrosion protection.

The manufacturer in collaboration with his local agent shall rectify all defects notified within the above periods entirely at their own expenses. If a faulty equipment has to return to works for repair under the above guarantee clause, the manufacturer in collaboration with his local agent shall cover the cost of transport from site to works and back again to site. Should any design fault become apparent to Tanesco after the expiry of the above guarantee periods, the manufacturer in collaboration with his local agent shall deliver components necessary to correct the fault, together with any necessary instructions and specialist assistance, free of charge.

10. RATED FREQUENCY

The rated frequency of the distribution MV fuse cutouts shall be 50Hz. Cutouts manufactured for 60Hz systems may also be acceptable but the bidder shall indicate the de-rating that may be appropriate, if any, when operated in a 50Hz system.

11. RATED VOLTAGE

The distribution fuse cutouts shall have a rated maximum voltage of 36kV and 12kV respectively. Equivalent North American practice voltages, in accordance with table V of IEC 282-2, shall be acceptable.

12. INSULATION LEVEL

The insulation level of the 33kV fuse cutouts shall be:

o 1.2/50s impulse wave: 170kV; and

o 50Hz, one minute, withstand voltage level (wet and dry): 70kV.

S24-15


The insulation level of the 11kV fuse cutouts shall be:

o 1.2/50s impulse wave: 75kV; and

o 50Hz, one minute, withstand voltage level (wet and dry): 28kV.

13. CURRENT RATING

The continuous current ratings of the distribution MV load break fuse cutouts shall be:

o 33kV: 100A; and

o 11kV: 100A.

The bid shall indicate the cutout's capability to break load equal to its continuous current rating and to make on a fault.

14. RATED INTERRUPTING CAPACITY

The rated interrupting capacity of the distribution MV load break fuse cutouts shall be:

o 33kV: 4kA, rms (symmetrical) prospective current, confirmed by 6

tests of test series number 1 with the characteristics given in table IVA of IEC 282-2. Or, alternatively, confirmed by 6 tests of test series number 1 with the characteristics given in table 3 of ANSI C37.41.

o 11kV: 8kA, rms (symmetrical) prospective current, confirmed by 6 tests of test series number 1 with the characteristics given in table IVA of IEC 282-2. Or, alternatively, confirmed by 6 tests of test series number 1 with the characteristics given in table 3 of ANSI C37.41.

15. LOW CURRENT INTERRUPTION

The fuse cutouts shall meet the requirements of test series number 5 in table IVA of IEC 282-2 or, alternatively, test series number 5 in table 3 of ANSI C37.41.

S24-16


16. TEMPERATURE RISE LIMITS

The assemblies shall be rated 105C for normal circuit conditions. The complete load break fuse cutouts shall be able to carry continuously its rated current without exceeding the temperature rise limits set out in IEC 282-2, or equivalent

17. FUSE LINK RANGE AND CLASS

The 33kV load break fuse cutouts shall be suitable in all respects for all standard fuse links within the range 1A to 100A as per IEC and NEMA standards.

The 11kV load break fuse cutouts shall be suitable in all respects for all standard fuse links within the range 1A to 100A as per IEC and NEMA standards.

18. INTERCHANGEABILITY

The fuse holder of a distribution MV load break fuse cutout shall be dimensionally compatible with a universal fuse tube of a corresponding rating and with the corresponding range of universal fuse links.

19. INSULATORS

The insulators supporting the load break fuse cutouts shall be rated for operation at a maximum voltage of 36kV and 12kV respectively. The insulators shall be of the solid core glazed porcelain of high strength and arc resistivity type and shall be bird proof. Other type of insulator material may be considered provided that it will meet the performance characteristics of the solid core glazed porcelain. They shall meet the electrical and mechanical characteristics specified in IEC 383.

The support insulators for the 33kV load break fuse cutouts shall withstand for one minute, dry and wet 50Hz test voltages of not less than:

o 70kV to earth and between poles; and o 80kV across the isolating distances, in accordance with IEC 60-2.

S24-17


The support insulators for the 11kV load break fuse cutouts shall withstand for one minute, dry and wet 50Hz test voltages of not less than:

o 28kV to earth and between poles; and o 32kV across the isolating distances, in accordance with IEC 60-2.

The bidder shall also give the following information in the technical data schedule:

o the minimum dry flashover voltage value; o the minimum wet flashover voltage value; and o the 50Hz puncture voltage of insulators.

20. RADIO INFLUENCE VOLTAGE

The maximum radio influence voltage shall be 250V measured at 1MHz and in accordance with IEC 437.

21. CLEARANCES

The bidder shall give the following information in the technical data schedule for both, 33kV and 11kV distribution MV load break fuse cutouts:

o minimum phase to phase clearance; and

o minimum phase to earth clearance.

22. CREEPAGE DISTANCE

The minimum creepage distance to ground for the distribution MV load break fuse cutouts shall be:

o 33kV: 720mm; and

o 11kV: 300mm.

S24-18


23. MAIN ASSEMBLY

For easy mounting of the fuse cutout and surge arrester combination on a standard auxiliary crossarm, the complete mounting assembly shall include the type X extended N.E.M.A bracket c/w bolts, nuts & washers, with an additional extension above to give enough clearance between the mild steel crossarm & the arrester. The X extended N.E.M.A bracket is a little bit longer (65mm) than the N.E.M.A type B bracket. For easy reference see drawing attached on page 34.

Top and bottom contact subassemblies and mounting fittings shall be potted into the porcelain insulators. The upper fixed contact assembly shall be shielded and positively latch.

All contacts shall be designed to give permanent current carrying capacity at rated current, after exposure to a marine climate for up to 20 years. All current carrying components shall be of copper or copper alloy. Terminals shall be of copper or heavily tinned bronze, suitable for both copper and aluminium conductor up to 100sq mm ACSR and compressed palm lugs. Contacts shall be heavily silver clad on each side of each interface. Embossed surfaces with wiping action are preferred.

The upper contact shall have safety latch to prevent upper contact from dropping due to vibration and mounted with stainless steel back up spring to ensure the contact pressure between stationary contact and the movable contact of the fuse.

The lower contact shall house a stainless steel back up spring to ensure high contact pressure with positive contribution to release of the toggle connection.

Ferrous components shall be made preferably of stainless steel or galvanized to BS 729. The manufacturer shall state the mass and thickness of zinc coating on the technical data schedule.

The load break fuse cutout shall be designed such that the fuse tube can be closed without using undue care even when the closing force is applied at an angle. The angle of fuse tube relative to the vertical shall be stated in on the attached technical data schedule and it shall be less than 20. ... The cutout insulators shall preferably be marked with the rated voltage and with the basic impulse level insulation.

S24-19


24. FUSE TUBE ASSEMBLY

The fuse tubes in the 33kV load break fuse cutouts shall be capable of accepting IEC or NEMA fuse links up to a maximum continuous current rating of 100A and that in the 11kV load break fuse cutouts up to a maximum continuous current of 100A.

The toggle mechanism shall provide a locking action to protect the fuse link from shock. A stainless steel spring-assisted flipper shall assist arc interruption by withdrawal of the fuse tail.

The fuse tube cap may be of the expendable type. The arc shortening rods, if provided, shall be permanently attached to the fuse tube cap. The Fuse tube shall be made of high strength synthetic fiber to lessen moisture absorption inside the tube and to extend the life of the fuse holder. Fuse tube shall be heavily coated with enamel to provide protection against ultra violet rays.

A lifting eye shall be provided on the fuse tube and designed for use with a standard operating rod.

The fuse tubes shall be permanently marked with the following: o name of manufacturer and/or trade mark; o TANESCO's name and logo; o model; o rated voltage; o continuous current rating; and o rms, symmetrical, rated interrupting capacity.

25. FUSE LINKS

The fuse links are required to give protection against short circuits. They shall conform to IEC, NEMA and ANSI standards or equivalent and they shall be so rated; and shall have such melting characteristics as to be suitable for selective operations with the fuse links at present in use on the system, namely type K - fast fuse links and type T slow fuse links, in conformity with NEMA SG-2 and ANSI C37.42.

S24-20


In addition, the fuse links shall be suitable for use on both 33kV and 11kV systems on outdoor, single vented, drop out fuse tubes with or without arc shortening rods. They shall be compatible with all universal fuse tubes.

The preferred rating of fuse links shall be:

11kV: 2A, 4A, 6A, 10A, 16A, 25A, 31.5A, 40A, 50A and 80A; and

33kV: 2A, 4A, 6A, 10A, 16A, 25A, 40A and 50A.

The rated current of the fuse link is the maximum current, which it will carry continuously without deterioration and undue heating. The bidder shall state on the technical data schedule the maximum temperature in C attained by the fuse link after continuous operation at maximum rating.

The time-current characteristics shall conform to NEMA type K and type T. The bidder shall submit with the bid the time-current performance characteristics of all the distribution fuse links on offer. The performance characteristics of the fuse links shall include:

o melting time-current characteristics; and o total clearing time-current characteristics.

The time-current characteristics shall be presented as curves.

The bidder shall state the minimum and maximum melting currents required to melt the fuse links at the three appropriate time points (0.1s, 10s and 300s or 600s) used in table 6 (melting-currents for type-K (fast) fuse links) of ANSI C37.42.

Fuse links shall be of the removable button head type. The Fusible element shall be of silver (as distinct from silver-copper alloy) and never of tin. The bidder shall completely describe the composition of the fuse link and of the fusible element.

The diameter of the button head cap on the fuse link shall be 19.1mm up to 100A. Removable type button heads are preferred for use with 11kV fuse cutouts.

The minimum overall length of the fuse links shall be: o 11kV: 533 mm o 33kV: 787 mm.

S24-21


Figure 2 illustrates the typical fuse links both type K and T; and the dimensions of the same for fuse links from 150 Amps and from 65100 Amps.

Fuse links shall be capable of withstanding a tension pull of 44.5N when tested cold (20C to 25C) without mechanical or electrical damage to any part of the fuse links.

The bidder shall completely describe the composition of the fuse tube surrounding the fusible element, its resistance to compression, collapse or twisting when being installed and the degree of fuse tube wall swelling when wet.

The bidder shall also provide information on the precautions to be taken to avoid damage to the fuse link and to what extent the time-current characteristics change over time, making fuse links unreliable on overload.

Each fuse link shall be legibly and indelibly marked with the following information:

o manufacturers name or trade mark;

o TANESCO's name and logo;

o type designation (K or T); and

o continuous current rating.

A sample of the fuse links offered shall be provided with the bid.

26. OPERATING TOOLS

The load break fuse cutouts will be operated by means of standard operating rod. The load break fuse cutouts offered shall not impede this means of operation.

S24-22


27. TESTS

27.1 Routine tests

Routine tests for fuse cutouts shall be selected from the type tests listed in IEC 282 or ANSI C37.41. The bidder shall include, with the bid, sample test reports of routine tests to be carried out and shall list them in the test certificates schedule.

27.2 Type tests

The following type tests shall be carried out on the fuse cutouts:

o dielectric tests;

o interrupting tests;

o radio interference tests;

o temperature rise tests in accordance with IEC 60;

o load break tests to ANSI C37.41;

o time-current tests;

o porosity test; and

o corrosion performance tests.

Where fault making tests have been performed on the model being offered, the test certificates shall also be attached.

The following tests shall be carried out on the fuse links:

o interrupting tests;

o temperature rise tests; and

o time-current tests.

S24-23


To confirm the interruption capacity of the fuse links, four tests of test series number 5 shall be carried out with the characteristics set out in table IVA of IEC 282-2 or, alternatively, four tests of test series number 5 with the characteristics of table 3 of ANSI C37.41. The test load shall have the X/R ratio given in table 6 of the same ANSI standard.

The temperature rise of the cutouts, containing the fuse links being tested in accordance with ANSI C37.41, shall not go above the limits set out on table 2 of C37.40 For the time-current tests, comprising melting time-current tests and total time-current clearing tests, the minimum melting-current characteristics of any fuse link shall agree with the values set out in table 6 of ANSI C37.42.

27.3 Corrosion Performance Tests

Performance shall be tested after the load break cutout has been subjected to 1,000 hours of corrosive salt spray, in conformity with IEC 507. An equivalent field experience in coastal sites shall be acceptable.

The bidder shall confirm that the current carrying contacts shall meet the temperature rise requirements after approximately 20 years of coastal exposure and that other metal parts shall retain their mechanical strength.

S24-24


28. SCHEDULES

28.1 Technical Data Schedule: Fuse Cutouts

Description Unit Bid

Type/Model of fuse cutout Manufacturer Country of Origin

Catalogue Number

International standard it complies with

Rated Frequency

Nominal Voltage Rated Maximum Voltage

Basic Impulse Level (1.2/50s):

Phase to Earth Phase to Phase, when open

50Hz, 1 minute, Withstand Voltage, Wet:

Phase to Earth Phase to Phase, when open

Minimum continuous rated current

Current de-rating at 1,600m altitude

Rated interrupting capacity

Lowest overload giving 2s melting time Minimum current interrupted by 6kA fuse Load break rating

Fault making capability

Hz

KV

KV

KV KV

KV KV

A

%

kA(sym)

n*A

A A

kA

S24-25


Description Unit Bid Fuse link range A

1MHz radio interference voltage V

Temperature rise at rated current C

Minimum phase to phase clearance mm

Minimum phase to earth clearance mm

Minimum creepage length mm

Angle to Vertical

Type of Insulators

Insulator Manufacturer/country of origin

Minimum Flashover Voltage:Wet kV Dry kV

50Hz Puncture Voltage kV

Method of attaching insulator to base

Are assemblies potted into porcelain? (y/n)

Fixed load break device fitted? (y/n)

Are duties listed in Clause 9 ok? (y/n)

Fuse tube manufacturer/country of origin

Is fuse tube compatible with universal fuse holder? (y/n)

Fuse tube material Does fuse tube expand when wet? (y/n) Does lining contain fibreglass? (y/n)

S24-26


Description Unit Bid Spring operated flipper available? (y/n)

sq.mm

Locking toggle mechanism supplied? (y/n)

Is fuse cap expendable? (y/n)

Are arc shortening rods provided? (y/n) Are arc shortening rods fixed to fuse tube cap? (y/n)

Material of current carrying parts Conductor range suitable for cutout Contacts material

Are contacts heavily silver clad? (y/n)

Type of contact weather protection

Is upper contact incorporated into insulator shed?

(y/n)

Material of ferrous components

Standard of galvanizing, if applicable

Minimum mass of zinc deposited gm/sq.mm

Minimum average zinc coating thickness Mounting hole bolt diameter um mm

Markings on fuse tube

Length of fuse tube Diameter of fuse tube

mm mm

Weight of fuse cutout kg

Weight of fuse tube Weight of fuse cutout in service

kg kg

NB: please fill in one schedule for each type or model of cutout

S24-27


28.2 Technical Data Schedule: Fuse Links

Description Unit Bid

Type of fuse link Manufacturer Country of Origin Catalogue Number

International standard it complies with

Rated frequency Rated current

Current derating at 1,600m altitude

Max/min melting current: 0.1s 10s

300s/600s Max temperature with rated current and 40 C ambient temperature

Tensile breaking load

Is fuse link compatible with universal fuse tube?(y/n)

Composition of fuse link Composition of fuse element

Type of fuse link button head

Diameter of fuse link button head

Is link button head removable? (y/n)

Fuse link marking

Length of fuse link: 33kV fuse cutouts 11kV fuse cutouts

Hz A

%

A A A

C

N

mm mm

S24-28


28.3 Non Compliance Schedule

On this schedule the bidder shall provide a list of non compliances with this specification, documenting the effects that such non compliance is likely to have on the equipment's life and operating characteristics. Each non compliance shall be referred to the relevant specification clause.

Clause No. Non Compliance

S24-29


28.4 Test Certificates Schedule

On this schedule a list of the test certificates included with the bid shall be provided. This list shall include type test certificates and sample routine test reports. Each certificate listed shall be referred to the relevant specification clause.

Clause No. Type Test Certificate or Routine Test Report

S24-30


PART 3: INSTALLATION

29. INSTALLATION

Tanescos employees shall do the work of installing the MV load break fuse cutouts and fuse links. General guidelines for installation work are given in Specification S01: General technical requirements of 33kV, 11kV and LV networks.

S24-31


S24-33


Figure 1: Typical Distribution MV Load Break Fuse Cutout with Arc Chute

S24-34


Figure 2: Fuse Links

S24-35


Figure 8 of Specification S13: Type X Extended Bracket

S24-36


Figure 3: Typical 11 kV Surge Arrester

S24-37


Figure 4: Typical 33 kV Surge Arrester

S24-38

tanesco tanzania - specification s24 mv load break fuse cutouts with arc chutes (2000)

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