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11KV/415V Overhead Line Specification as per REC

11KV/415V OVERHEAD LINE SPECIFICATION(REC)

11KV/415V OVER HEAD LINE’S SPECIFICATION AND INSTALLATION (REC):

 11KV LIGHTNING ARRESTER (IS: 3070 (PT-II)).

VOLTAGE RATING FOR LA:

  • The rated voltage of lightning arresters shall be 9 KV (rms). * This will be applicable to the effectively earthed 11 KV systems co-efficient of earth not exceeding 80 percent as per IS: 4004 with all the transformer neutrals directly earthed.

NORMAL DISCHARGE CURRENT RATING FOR LA:

  • The nominal discharge current rating of the lightning arresters shall be 5 KA.

TESTS FOR LA:

  • The following routine and type tests as laid down in IS : 3070 (Part-I) shall be carried out. * Routine Test: Dry Power frequency spark over test. * Type Tests (Confirmation) :
  1. Voltage withstand tests of arrester insulation. 2. Power frequency spark over test 3. Hundred percent 1.2/550 microsecond impulse spark over test 4. Front-of-wave impulse spark over test. 5. Residual voltage test. 6. Impulse current withstand test. 7. Operating duty test. 8. Temperature cycle test on porcelain housing. 9. Porosity test on porcelain components. 10. Galvanizing test on metal parts.

11 KV DROP-OUT FUSE CUTOUTS: (IS: 9385 (PART-I TO III).)

  • The distribution fuse cutouts shall be outdoor, open, drop-out expulsion type fuse cutouts suitable for installation in 50 Hz, 11 KV distribution system. * The rated voltage shall be 12 KV. * The rated current shall be 100 A.

RATED LIGHTING IMPULSE WITHSTANDS VOLTAGE FOR FUSE:

  • To earth and between poles 75 KV (Peak) * Across the isolating distance of fuse base 86 KV (Peak)

RATED ONE MINUTE POWER FREQUENCY WITHSTAND VOLTAGE (WET & DRY) FOR FUSE:

  • To earth and between poles 28 KV (rms) * Across the isolating distance 32 KV (rms)

TEMPERATURE RISE LIMIT FOR FUSE:

  • Copper contacts silver faced 650C * Terminals 500C * Metal parts acting as spring The temperature shall not reach such a value that Elasticity of the metal is changed

RATED BREAKING CAPACITY FOR FUSE:

  • The rated breaking capacity shall be 8 KA (Asymmetrical).

CONSTRUCTION DETAILS FOR FUSE:

  • The cutouts shall be of single vent type (downward) having a front connected fuse carrier suitable for angle mounting. * All ferrous parts shall be hot dip galvanized in accordance with the latest version of IS : 2632. Nuts and bolts shall conform to IS : 1364. Spring washers shall be electro-galvanized.

FUSE BASE TOP ASSEMBLY:

  • The top current carrying parts shall be made of a highly conductive copper alloy and the contact portion shall be silver plated for corrosion resistance and efficient current flow. * The contact shall have a socket cavity for latching and holding firmly the fuse carrier until the fault interruption is completed within the fuse. * The top assembly shall have an aluminum alloy terminal connector. The top assembly shall be robust enough to absorb bulk of the forces during the fuse carrier closing and opening operations and shall not over-stress the spring contact. It shall also prohibit accidental opening of the fuse carrier due to vibrations or impact.

FUSE BASE BOTTOM ASSEMBLY:

  • The conducting parts shall be made of high strength highly conductive copper alloy and the contact portion shall be silver plated for corrosion resistance and shall provide a low resistance current path from the bottom fuse carrier contacts to the bottom terminal connector.

FUSE CARRIER TOP ASSEMBLY:

  • The fuse carrier top contact shall have a solid replaceable cap made from highly conductive, anticorrosive copper alloy and the contact portion shall be silver plated to provide a low resistance current path from the Fuse Base Top Contact to the Fuse Link. * It shall make a firm contact with the button head of the fuse link and shall provide a protective enclosure to the fuse link to check spreading of arc during fault interruptions. * The fuse carrier shall be provided with a cast bronze opening eye (pull ring) suitable for operation with a hook stick from the ground level to pull-out or close-in the fuse carrier by manual operation.

FUSE CARRIER BOTTOM ASSEMBLY:

  • The fuse carrier bottom assembly shall be made of bronze castings with silver plating at the contact points to efficiently transfer current to fuse base. * It shall make smooth contact with the fuse base bottom assembly during closing operation. The bottom assembly shall have a lifting eye for the hook stick for removing or replacing the fuse carrier.

FUSE BASE (PORCELAIN):

  • The fuse base shall be a bird-proof, single unit porcelain insulator with a creepage distance (to earth) not less than 320 mm. The top and bottom assemblies as also the middle clamping hardware shall be either embedded in the porcelain insulator with sulphur cement or suitably clamped in position. * For embedded components, the pull out strength should be such as to result in breaking of the porcelain before …