SECTION -05
OUT DOOR CURRENT TRANSFORMERS
1.0       SCOPE:
1.1       This scope covers for design, manufacture, inspection, testing before
          dispatch, packing and delivery F.O.R (Destination) of 800 KV and 420KV
          Outdoor Current Transformers along with all accessories with its terminal
          box and a common junction box, terminal connector specified herein for
          Protection and Metering services with suitable mounting structure.
1.2       The instrument transformer shall conform in all respects to high standards
          of engineering, design, workmanship and latest revisions of relevant
          standard at the time of offer and TANTRANSCO shall have the power to
          reject any work or material, which, in its judgement, is not in full accordance
          therewith.
2.0       STANDARDS:
2.1       Unless otherwise specified elsewhere in this specifications, the Current
          Transformers shall conform to the latest revisions and amendments thereof
          of the ISS & IEC Standards.
Sl.No.       Standard No.                                     Title
    01.     IS:2705            Current Transformers
    02.     IS:2099            High Voltage Porcelain Bushings
    03.     IS:3347            Dimensions of porcelain for transformer
    04.     IS:2165            Insulation co-ordination for equipments of 110KV and above.
    05.     IS:335             Insulating oil for transformers
    06.     IS:2071            Method of high voltage testing
    07.     IS:2147            Degree of protection provided by enclosure for low voltage
                               switch gear and control
    08.     IEC:60185          Current Transformers
    09.     IEC:60060          High Voltage testing techniques
    10.     IEC :60071         Insulation co-ordination
    11.     IEC:60044(4)       Instrument transformer measurement of P.Ds
    12.     IEC:60270          Partial discharge measurement
    13.     IEC:8263           Method for RIV test on high voltage insulators.
    14.     IEC:60044-1        Current Transformers
                                            357
       Besides the above, the standard minimum safety clearances stipulated in IE
Rules 1956 shall also be complied with and the relevant latest IEC /IS applicable for
the offered Technology.
3.0    PRINCIPAL PARAMETERS & CORE WISE DETAILS:
       The current transformers covered in the specification shall meet the
       technical requirements listed here under:
3.1 PRINCIPAL             TECHNICAL         PARAMETERS           OF       CURRENT
TRANSFORMERS:
A) PRINCIPAL TECHNICAL PARAMETERS OF 800 KV CURRENT
TRANSFORMERS:
Sl.   Item                                 800 KV CT
No
01    Type of CT/Installation              Single Phase, Dead/Live tank, oil filled/ SF6
                                           gas filled, hermetically sealed, self cooled
                                           outdoor type
02    Type of mounting                     Pedestal/structure mounting type
03    Suitable for system frequency        50 Hz
04    Highest system voltage               800 KV (rms)
      Number of CT secondary               6 Nos.
      Number of cores per CT               6 Nos.
05    Current ratio A/A                        (a) Core 1 & 2  3000-2000-1000/1A
                                               (b)Core3& 4  3000-2000-1000-500/1A
                                           (c) Core 5&6- 3000-2000-1000/1A
06    Ratio Taps                           On Secondary side.
07    Method of Earthing system where Solidly earthed.
      the Current Transformer will be
      installed.
08    Rated continuous thermal Current 120% for higher two ratio taps and 200%
      (A).                             for lower ratio taps.
09. Acceptable limit of temperature As per IS- 2705.
    rise above the specified ambient
    temperature      for    continuous
    operation at rated Current.
10. Acceptable partial discharge level Less than 5 pico coulombs.
    at 1.2 Um /root 3
11. Max. Radio interference voltage at 2500 micro Volts.
    1.1 times the maximum rated
    Voltage/Root 3
                                        358
12. 1.2/50 micro second Lightning 2100
    Impulse withstand Voltage (KV
    peak) Dry.
13    Switching    impulse    withstand 1550
      voltage(250/2500 micro second)KV
14. 1    minute    power     frequency 970
    withstand voltage on primary (Dry)
    KV(rms)
15. Power frequency over voltage 5
    withstand    requirement     for
    secondary winding(KV rms) for 1
    min.
16. Min.    creepage    distance        of 20000
    porcelain housing (mm).
17. Rated short time withstand Current 50
    for 1 second duration(KA rms).
18. Rated dynamic withstand Current 125
    (KA peak)
19. Visual corona extinction voltage 508
    (KV RMS)
20. Number of terminals in control All contacts and control circuit to be wired
    cabinet.                       up to control cabinet plus 20% extra
                                   terminals exclusively for purchasers use.
21. Seismic acceleration(Horizontal)       0.3g.
22. Maximum dielectric          dissipation 0.002
    factor at Um/root3
23. Primary    to     earth     insulation Min 20,000 M ohms
                    0
    resistance at 30 C
24. Cantilever strength Kg                 500
B) PRINCIPAL TECHNICAL PARAMETERS OF 420 KV CURRENT
TRANSFORMERS:
Sl.   Item                                 420 KV CT
No
01    Type of CT/Installation              Single Phase, Dead/Live tank, oil filled,
                                           hermetically sealed, self cooled outdoor type
02    Type of mounting                     Pedestal/structure mounting type
03    Suitable for system frequency        50 Hz
04    Highest system voltage               420 KV (rms)
      Number of CT secondary               6 Nos.
                                         359
     Number of cores per CT            6
05   Current ratio A/A                    (b) Core 1 & 2  3000-2000-1000/1A
                                          (b)Core3 &4 3000-2000-1000500/1A
                                          (c) Core 5 & 6 - 3000-2000-1000/1A
06   Ratio Taps                        On Secondary side.
07   Method of Earthing system where Solidly earthed.
     the Current Transformer will be
     installed.
08   Rated continuous thermal Current 120% for higher two ratio taps and 200%
     (A).                             for lower ratio taps.
09. Acceptable limit of temperature As per IS- 2705.
    rise above the specified ambient
    temperature      for    continuous
    operation at rated Current.
10. Acceptable partial discharge level Less than 5 pico coulombs.
    at 1.2 Um /root 3
11. Max. Radio interference voltage at 2500 micro Volts.
    1.1 times the maximum rated
    Voltage/Root 3
12. 1.2/50 micro second Lightning 1425
    Impulse withstand Voltage (KV
    peak) Dry.
13. Switching    impulse    withstand 1050
    voltage(250/2500 micro second)KV
14. 1    minute    power     frequency 630
    withstand voltage on primary (Dry)
    KV(rms)
15. Power frequency over voltage 3
    withstand    requirement     for
    secondary winding(KV rms) for 1
    min.
16. Min.    creepage    distance    of 10500
    porcelain housing (mm).
17. Rated short time withstand Current 63
    for 1 second duration(KA rms).
18. Rated dynamic withstand Current 157.5
    (KA peak)
19. Visual corona extinction voltage 320
    (KV RMS)
20. Number of terminals in control All contacts and control circuit to be wired
    cabinet.                       up to control cabinet plus 20% extra
                                   terminals exclusively for purchasers use.
                                     360
        21. Seismic acceleration(Horizontal)           0.3g.
        22. Maximum dielectric           dissipation 0.002
            factor at Um/root3
        23. Primary    to     earth       insulation Min 20,000 M ohms
                            0
            resistance at 30 C
        24. Cantilever strength Kg                     500
        B.       PRINCIPAL TECHNICAL PARAMETERS OF 800 KV C T
        3.2 CORE WISE DETAILS OF CURRENT TRANSFORMERS:
        (A) REQUIREMENT FOR 800 KV CTs (3000-2000-1000-500/1-1-1-1-1-1A)
No.         co    Applicatio   Current   Output Accu-          Min.      Max.       Max.        Remarks
of          re    n            Ratio     Burden racy           Knee      CT.sec.    Exciting
cores       No                           (VA)   class as       point     winding
                                                per IEC-       voltage   resistance current
                                                60044-1        (VK)                 @ Knee
                                                                         (ohms)
                                                               (Volts)
                                                                                      point
                                                                                      voltage
                                                                                      Vk
                                                                                      (mA)
6           1     Main-I       3000/       ---    PS           3000/     15/          20mA      In case of
                  Protection                                                          on        dead tank
                               2000/                           2000/     10/
                  /Transfor                                                           3000/1    CTs,       3
                               1000/
                  mer                                          1000      5            Tap       cores shall
                  Backup       1A                                                               be fixed on
                                                                                      30mA
                  protection                                                                    one     side
                                                                                      on
                                                                                                and
                                                                                      2000/1
                                                                                                remaining 3
                                                                                      Tap
                                                                                                cores shall
                                                                                      60mA      be fixed on
                                                                                      on        the    other
                                                                                      1000/1    side.
                                                                                      Tap
            2     Main-II    3000/         ---    PS           3000/     15/          20mA
                  Protection 2000/                                                    on
                                                               2000/     10/
                  /                                                                   3000/1
                  Transfor    1000/                            1000      5
                                                                                      30mA
                  mer        1A                                                       on
                  Differenti                                                          2000/1
                  al                                                                  Tap
                  protection
                                                                                      60mA
                                                  361                                                                                    
                                                                                  on
                                                                                  1000/1
                                                                                  Tap
           3   Metering    3000/     20       0.2S      N.A                       N.A.
               Main        2000/     20       0.2S
                           1000/     20       0.2S
                           500/1A    20       0.2S
           4   Metering    3000/     20       0.2S      N.A                       N.A.
               Main        2000/     20       0.2S
                           1000/     20       0.2S
                           500/1A    20       0.2S
           5   Bus Diff.   3000/                        3000      15              20 mA
                                                                                  on
               Main        2000/     ----     PS        2000      10
                                                                                  3000/1
                           1000/                        1000      5               Tap
                           1A                                                     30 mA
           6   Bus Diff.   3000/                        3000      15              on
                                                                                  2000/1
               Check       2000/     ----     PS        2000      10              Tap
                           1000/                        1000      5               60mA
                           1A                                                     on
                                                                                  1000/1
                                                                                  Tap
       NOTE: (i) The parameters like Vk, RCT, Im specified shall be proportional to ratios.
            (ii) All the ratios shall be made available with secondary tapping only so
            that the same can be adopted simultaneously in different cores.
       (B) REQUIREMENT FOR 420 KV CTs (3000-2000-1000-500/1-1-1-1-1A)
No.    Core Applicatio     Current   Output    Accu-   Min.      Max.            Max.        Remarks
       No. n               Ratio     Burden    racy    Knee      CT.sec.         Exciting
of
                                     (VA)      class   point     winding         current
Core
                                               as      voltage   resistanc       @
s
                                               per     (VK)      e               Kneepoint
                                               IEC-    (Volts)                   voltage
                                                                 (ohms)
                                               6004                              Vk
                                               4-1                               (mA)
                                               362
       
                                                                      
6   1    Main-I       3000/           ---    PS    3000/    15/            20mA on In case of
         Protection                                                        3000/1  dead tank
                      2000/                        2000/    10/
         /Transfor                                                         30mA on CTs,       3
                      1000/
         mer                                       1000     5                      cores shall
                                                                           2000/1
         Backup       1A                                                           be fixed on
                                                                           Tap
         protection                                                                one     side
                                                                           60mA on and
                                                                           1000/1  remaining
                                                                           Tap     two cores
                                                                                   shall     be
                                                                                   fixed     on
                                                                                   the    other
                                                                                   side.
    2    Main-II    3000/             ---    PS    3000/    15/            20mA on
         Protection 2000/                                                  3000/1
                                                   2000/    10/
         /                                                                 30mA on
         Transfor    1000/                         1000     5
                                                                           2000/1
         mer        1A                                                     Tap
         Differenti
         al                                                                60mA on
         protection                                                        1000/1
                                                                           Tap
    3    Metering     3000/      20         0.2    N.A                     N.A.
         Main         2000/      20         0.2
                      1000/      20         0.2
                      500/1A     20         0.2
    4    Metering     3000/      20         0.2    N.A                     N.A.
         Main         2000/      20         0.2
                      1000/      20         0.2
                      500/1A     20         0.2
    5    Bus Diff.    3000/                        3000     15             20 mA on
                                                                           3000/1
         Main         2000/       ----      PS     2000     10
                                                                           Tap
                      1000/                        1000     5
                                                                           30 mA on
                      1A                                                   2000/1
    6    Bus Diff.    3000/                        3000     15             Tap
         Check        2000/       ----      PS     2000     10             60mA on
                                                                           1000/1
                      1000/                        1000     5              Tap
                      1A
    NOTE:(i)     The parameters like Vk, RCT, Im specified shall be proportional to
                 ratios.
                                            363
    
                                                                   
      (ii)   All the ratios shall be made available with secondary tapping only so
             that the same can be adopted simultaneously in different cores.
4.0 GENERAL TECHNICAL REQUIREMENTS:
4.1 Current Transformers should have the following requirements:
      (a)    Current Transformers shall have single primary either ring type, or
hair pin type and suitably designed for bringing out the secondary terminals in a
weather proof (IP 55) terminal box at the bottom. These secondary terminals shall
be terminated to stud type non disconnecting terminal blocks inside the terminal
box. The primary winding should be housed in rigid metallic shell. The winding
assembly should be held firmly and for this purpose suitable clamping arrangement
at the bottom shall be provided and explained through a sketch. Firm clamping
arrangement is a must and holding of winding using nylon rope etc. shall not be
acceptable. In case Bar primary inverted type current transformers are offered
the manufacturer will meet the following additional requirements.
             (i)     The secondaries shall be totally encased in metallic
                     shielding providing a uniform equipotential surface and ensure
                     even electric field distribution.
             (ii)    The lowest part of the insulation assembly shall be properly
                     secured to avoid any risk of damage due to transportation
                     stresses.
             (iii)   The upper part of insulation assembly resting on primary
                     bar shall be properly secured to avoid any damage during
                     transportation due to relative movement between insulation
                     assembly and top dome.
             (iv)    Nitrogen if used for hermetic sealing (in case of live tank
                     design) should not come in direct contact with oil.
             (v)     Bidder/Manufacturer shall recommend whether any special
                     storage facility is required for CT.
      (b)    Different ratios specified shall be achieved by secondary taps only
              and primary reconnection shall not be accepted.
      (c)    Core lamination shall be of cold rolled grain oriented silicon steel or
             other equivalent better alloys. The cores used for protection shall
             produce undistorted secondary current under transient conditions at
             all ratios with specified CT parameters.
      (d)    The expansion chamber at the top of the porcelain insulators should
             be suitable for expansion of oil.
      (e)    Facilities shall be provided at terminal blocks in the marshalling box
             for star delta formation, short circuiting and grounding of CT
             secondary terminals.
                                        364
       (f)    Current Transformers guaranteed burdens and accuracy class are to
              be intended as simultaneous for all cores.
       (g)   For 765/420 kV Class CTs, the rated extended primary current shall be
             200 % of rated primary on all except 3000/1A tap ration. On
             3000/1A tap ratio the extended primary current shall be 120% .
             However at 3000/1A ratio the CT shall be thermally rated for 200%
             for 15 minutes and 120% continuous
       (h)    For 765/420 kV Current Transformer, characteristics shall be such as
              to provide satisfactory performance of burdens ranging from 25% to
              100% of rated burden over a range of 10% to 100% of rated current
              in case of metering CTs and up to the accuracy limit factor/knee point
              voltage in case of relaying CTs.
       (i)    The Current Transformer shall be suitable for horizontal
              transportation. It shall be ensured that the CT is able to withstand all
              the stresses imposed on it while transporting and there shall be no
              damage in transit. The contractor shall submit the details of packing
              design to the purchaser for review.
       (j)    For 765 kV CTs the instrument security factor at all ratios shall be less
              than ten (10) for metering cores and 420 kV CTs the instrument
              security factor at all ratios shall be less than five (5) for metering
              core.
       (k)    The wiring diagram plate for the interconnections of the three single
              phase CTs shall be provided inside the marshalling / junction box.
       (l)    Suitable for mounting lattice support structure to be supplied along
              with the Current Transformers
       (m)    The CT shall be designed as to achieve the minimum risks of
              explosion in service. Bidder/Manufacturer shall bring out in his offer,
              the measures taken to achieve this.
       (n)    765/420 kV Current Transformers shall be suitable for high speed
              auto reclosing.
4.2.   The insulation of the current transformer shall be designed such that the
       internal insulation shall have higher electrical withstand capability than the
       external insulation. The designed dielectric withstand values of external and
       internal insulations shall be clearly brought out in the guaranteed technical
       particulars. The dielectric withstand values specified in the specification are
       meant for the fully assembled Current Transformers.
4.3.   PORCELAIN HOUSING:
       The details of location and type of joint, if provided on the porcelain shall be
furnished by the Bidder along with the offer. The housing shall be made of
homogeneous, vitreous, porcelain of high mechanical and dielectric strength,
                                         365
glazing of porcelain shall be of uniform brown or dark brown colour with smooth
surface arranged to shed away rain water or condensed water particles (fog). The
profile of porcelain shall be aerodynamic type as per IEC-815. Details of
attachment of metallic flanges to the porcelain shall be brought in the offer .
4.4. The bushings shall have ample insulation, mechanical strength and rigidity for
the condition under which they shall be used and shall be designed to prevent
accumulation of explosive gases and provide adequate oil circulation to remove
the internal heat. Cast metal end caps     for the bushings shall be of high strength,
hot dip galvanized malleable iron. They shall have smooth          surface to prevent
discharge taking place between the metal parts and porcelain as a result of
ionization. The insulation of bushings shall be coordinated with that of the Current
Transformer such that the flashover, if any will occur only external to the Current
Transformer. End shields should be provided for distribution of stresses. Corona
shields for bushings, if required should be provided.
4.5. TANK : The metal tanks shall have a bare minimum number of welded joints
so as to minimize possible locations of oil leakage. The metal tank shall be made
out of mild steel/stainless steel/ aluminium alloy, depending on the requirement.
Welding in horizontal plane is to be avoided as welding at this location may give
way due to vibrations during transport resulting in oil leakage. Supplier has to
obtain specific approval from purchaser for any horizontal welding used in the
bottom tank.
4.6.   HOT DIP GALVANISING AND WEATHER PROOFING:
       All exposed Ferrous parts including Tank of the Current Transformer.
Structural steel, pipes, rods, levers, linkages, nuts & bolts used etc shall be hot dip
galvanized as per IS: 2629 and IS 2633.
4.7. CORE:
(a)    The grade M4 toroidal core shall be of high-grade non-ageing electrical
silicon laminated steel of low hysterisis loss and high permeability to ensure high
accuracy. The instrument transformer core to be used for metering shall be of
accuracy class specified or appropriate class suitable for commercial and industrial
metering.
                                          366
4.8.   INSULATING MEDIUM (OIL/ SF6 Gas)
A) Insulating oil/SF6 gas required for first filling of the CT shall be covered in
Bidders scope of supply. The oil/ SF6 gas shall meet the requirements of latest
edition of IS/IEC.
4.9 PREVENTION OF OIL LEAKAGES AND ENTRY OF MOISTURE:
4.9.1 The supplier shall ensure that the sealing of current Transformer is
        properly achieved. In this connection the sealing arrangement provided by
        the supplier at various locations including the following ones shall be
        described, supported by the sectional drawings.
       (i) Locations of emergence of primary and secondary terminals.
       (ii) Interface between porcelain housing and metal tanks.
       (iii) Cover of the secondary terminal box.
4.9.2 Nuts and bolts or screws for fixation of the interfacing porcelain bushings for
        taking out terminals, shall be provided on flanges cemented to the
        bushings and on the porcelain.
4.9.3 For gasketed joints, wherever used, Nitryl Butyl rubber gaskets shall be used.
        The gasket shall be fitted in properly machined groove with adequate
        space for accommodating the gasket under compression. Ageing             -tests
        shall be conducted on the gaskets and the test certificates produced for
        verification.
4.9.4. During inspection each CTs will be subjected to a pressure test at
        0.7 kg/sq. cm for 8hrs.
4.10 OIL LEVEL INDICATORS:
       Current Transformers supplied with Nitrogen cushion for compensation of oil
volume variation shall be provided with prismatic type oil sight window at suitable
location so that the oil level is clearly visible to naked eye for an observer standing
at ground level. If metal bellow is used for the above purpose a ground glass
window shall be provided to monitor the position of metal bellow.
                                         367
4.11. EARTHING:
      Metal tank of Current Transformer shall be provided with 2 Nos. separate
      earthing terminals for bolted connection to 65 x 10 mm MS flat for
      connection to station earth-mat.
4.12. LIFTING ARRANGEMENTS:
      Current Transformers shall be provided with suitable lifting arrangement to
      the entire unit. The lifting arrangement shall be clearly shown in the general
      arrangement drawing. Lifting arrangement (lifting eye) shall be positioned in
      such a way so as to avoid any damage to the porcelain housing or the tanks
      during lifting for installation/transport. Necessary string guides supplied shall
      be of removable type.
4.13. NAME PLATE:
      The Current Transformer shall be provided with, legible name plate with the
      information specified in relevant standards, duly engraved/punched on it,
      including the capacitance and tan delta value.
4.14. TERMINAL CONNECTOR:
      The Terminal Connectors (TC) required for connection of the Current
Transformer is 4.5 Aluminium bus bar for 800KV CT and 4 Aluminium bus bar for
420 KV CT.
4.14.1 The Terminal Connectors shall meet the following requirements
      (i)     Terminal connectors shall be manufactured and tested as per IS-
               5561.
      (ii)    All casting shall be free from blow holes, surface blisters, cracks and
              cavities. All sharp edges and corners shall be blurred and rounded off.
      (iii)   No part of a clamp shall be less than 16mm thick
      (iv)    All Ferrous parts shall be galvanized conforming to IS-2633
      (v)     For bimetallic connectors, copper alloy liner of minimum thickness of
              2mm shall be provided.
      (vi)    Flexible connectors if used shall be made from tinned copper.
      (vii)   All current carrying parts shall be designed and manufactured to have
              minimum contact resistance and the required current density.
                                         368
        (viii)   Connectors shall be designed to be corona free in accordance with
                 the requirements stipulated in IS: 5561. The sharp edges shall be
                 rounded of.
4.15. Enamel, if used for conductor insulation shall be either polyvinyl acetate type
        or amide type and shall meet the requirement of IS: 4800. polyester enamel
        shall not be used.
4.16. The temperature rise on any part of equipment shall not exceed the
        maximum temperature rise specified below under the conditions specified in
        test clauses. The permissible temperature rise indicated is for a maximum
        ambient temperature of 50C.
Sl.No    Nature of the part or of the Liquid                Temperatu         Maximum value
                                                            re                of Temp. rise at
                                                                              a max. ambient
                                                                              air temp. not
                                                                              exceeding 50C
01       Contacts in air, silver-faced copper, copper 105                     55
         alloy or aluminium alloy (see Notes (i) & (ii)
         Bare copper or Tinned aluminium alloy              75                25
02.      Contacts in oil.
         Silver faced copper, copper            alloy   or 90                40
         aluminium alloy (see Note ii)
         Bare copper or tinned aluminium alloy.             80                30
03.      Terminals to be connected to external 105                            55
         conductors by screws or bolts silver-
         faced(see note-iii).
         Bare copper or Tinned aluminium alloy.
                                                            90                40
04.      Metal parts acting as springs                      See note-iv       See note-iv
05.      Metal parts in contact with insulation of the
         following classes.
         Class-Y : (For Non-impregnated materials)          90                40
         Class-A: ( For materials immersed in oil or 100                      50
         impregnated)
                                                     120                      70
         Class-E: In Air
                                                     100                      50
                   In oil
                                                            130               80
                                          369
       Class-B: In Air                                     100              50
                     In oil
                                                           155              105
       Class-F: In Air                                     100              50
                     In oil                                100              50
       Enamel : oil base                                   120              70
                     Synthetic, in air                     100              50
                     Synthetic, in oil
06.    Any part of metal or of insulating material in 100                   50
       contact with oil except contacts
07.      Oil                                               90               40
NOTES:
      (i) When applying the temperature rise of 55C care should be taken to
               ensure that no damage is caused to the surrounding insulating
           materials.
      (ii) The quality of the silver facing shall be such that a layer of silver
                remains at the point of contact after the mechanical endurance test.
               Otherwise, the contacts shall be regarded as bare.
      (iii) The values of temperature and temperature rise are valid whether or
               not the conductor connected to the terminals is Silver-faced.
       (iv)The temperature shall not reach a value where the elasticity of the
               material is impaired. For pure copper, this implies a temperature limit
               of 80C.
5.0    CURRENT TRANSFORMER :
      5.1 The CT shall be of Dead/ Live tank design and shall be so
                constructed that it can be easily transported to site within the
                allowable transport limitation and in horizontal position if the
                transport     limitations so demand. The precautions if any, for
                horizontal transportation may be indicated in the name plate itself.
      5.2.      For compensation of variation in the oil volume due to ambient
                variation, Nitrogen cushion or metal bellows shallbeused,
                 rubberdiaphragms shall not be permitted for this purpose.
      5.3.      The CT secondary terminals shall be brought out in a weather proof
                terminal box. The terminal box shall be provided with removable
                                            370
           gland plate and glands suitable for 1100 Volts grade, PVC insulated,
           PVC sheathed multicore 4 sq .mm or 6 sq mm stranded                   copper
           conductor cable. The terminal blocks shall be stud type and provided
           with ferrules indelibly marked or numbered and these identifications
           shall correspond to the designations on the relevant wiring diagram.
           The terminals shall be rated for not less than 10 amps.
                  The terminal box shall be dust and vermin proof. Suitable
           arrangement shall be made for drying of air inside the secondary
           terminal box. The dimensions of the terminal box and its openings
           shall be adequate to enable easy access and working space with use
           of normal tools and measuring instruments such as tong type
           milliammeters.
    5.4.   Polarity shall be indelibly marked on each primary and secondary
           terminal. Facility shall be provided for short circuiting and grounding
           of the C.T. secondary terminals inside the terminal box.
    5.5.   The C.T. shall be provided with a rating plate with dimensions and
           markings as per I.S : 2705. The markings shall be punched and not
           painted.
    5.6.   The Current Transformer shall be vacuum dried and filled with oil
    after processing and thereafter hermetically sealed to eliminate breathing
            and to prevent air and moisture from entering the tanks. Oil filling
            and/or oil sampling cocks, if provided to facilitate factory processing
            should be permanently sealed before despatching the C.T.
    5.7.   The castings of base, collar etc., shall be die cast and tested
            before assembly to detect cracks and voids if any.
    5.8.    The instrument security factor of metering core shall be low enough
            and not greater than 5. This shall be demonstrated on all the ratios
            of the metering core, in accordance with procedure specified in IEC-
            60044-1 or IS:2705. In case the instrument security factor of 5 or
            less is not possible to be achieved on higher ratios, auxiliary CTs of
            ratio 1/1 & 5/5 and 0.2 accuracy class shall be deemed to be
            included in the suppliers scope of supply.
     This shall also be specifically brought out by the supplier in the offer.
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6.0. PRIMARY WINDING:
         Primary winding shall be made out of suitably insulated copper
    conductor of 99.9% conductivity.     Conductors used for the primary winding
    shall be rigid or housed in rigid aluminium shell. Unavoidable joints in the
    primary winding shall be welded type. The details of such welded joints shall be
    indicated in the drawings submitted with the offer. For primary winding current
    density shall not exceed 1.5A/ Sq.mm for copper primary winding. The design
    density for short circuit current as well as conductivity of the metal used for
    primary winding shall meet the requirement of IS: 2705.
7.0. SECONDARY WINDINGS:
    Suitably insulated Copper wire of electrolytic grade shall be used for secondary
    windings. Type of insulation design, suitable for tappings shall be provided on
    the secondary winding.
8.0. The maximum excitation current of the CT at Vk shall not exceed 60 milli
      amps at lowest tap. The Bidder shall furnish along with his offer the
      magnetization curve/s for all the core/s.
9.0     PRIMARY TERMINALS:
         The primary terminals shall be of heavily tinned electrolytic copper of
      99.9% conductivity. The minimum thickness of tinning shall be 15 microns.
      The primary terminal on either side of the tank shall be not less than 80mm
      length and 30mm dia copper.
10.0. SECONDARY TERMINALS:
       The secondary terminals shall be brought out in a weather proof terminal
box. Firstly the connections will be terminated in an internal Board and then the
same shall be brought out in a secondary terminal box. The terminal box shall be
provided with removable gland plate and glands suitable for 1100 volts grade PVC
insulated PVC sheathed multi core 4 or 6 sq.mm for CT.
    The terminal box shall be dust and vermin proof. Suitable arrangement shall be
made for drying of air inside the secondary terminal box. The dimensions of the
terminal box and its openings shall be adequate to enable easy access and working
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space with use of normal tools and measuring instruments such as tong type
milliammeters. The outer cover of secondary terminal box shall have provision for
sealing by way of insertion of wire in the bolt hole. A drawing indicating the above
arrangement may please be furnished along with the offer.
    Secondary terminal studs shall be provided with at least three nuts and
adequate plain and spring washers for fixing the leads. The studs, nuts and
washers shall be of brass, duly Nickel plated. The minimum outside diameter        of
the studs shall be 8 mm. The length of at least 15mm shall be available on        the
studs for inserting the leads. The horizontal spacing between centers of the
adjacent studs shall be at least 1.5 times the outside circum dia. of the nuts.
11.0 MEASUREMENT OF CAPACITANCE AND TAN DELTA:
       The Current Transformer shall be provided with suitable test tap for
measurement of capacitance, tan delta as well as partial discharges, in factory as
well as at site. Provision shall be made of a screw on cap for solid and secured
earthing of the test tap connection, when not in use. A suitable caution plate shall
be provided duly fixed on the cover of the secondary terminal box indicating the
purpose of the test tap and necessity of its solid       earthing as per prescribed
method before energizing the Current Transformers.
12.0 TYPE TEST:
12.1The successful tenderer should furnish before the offering of inspection of
the first lot of equipments commencement           of supply, copies of type test
certificates of the offered technology CTs obtained from a Government
/Government recognized Lab. The above type test certificates should accompany
the drawings for the CTs duly signed under seal by the institution who has issued
the type test certificate. The type tests should have been conducted as per IEC
60044-1 of latest version.
In case of instrument transformers, the following type tests should have been
conducted within 5 (five) years prior to the originally scheduled date of bid
opening.
i) Lightning Impulse Test
ii) Switching Impulse Test
iii) Multiple Chopped Impulse Test (For CT)
iv) Chopped Impulse Test (For CVT )
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       The above type test should have been conducted within 5 years as on the
date of tender opening. Original type test report shall be furnished for verification
on request.
12.2. Special Tests :
The following special tests as per IEC 60044-1 of latest version should be
conducted and test reports submitted from a Government / Government recognized
lab before offering of inspection of the first lot of equipments.
     (i)           Chopped Impulse Test on primary winding (Cl. 9.1).
     (ii)          Measurement of capacitance and dielectric dissipation factor (Cl.9.2.)
    (iii)          Mechanical tests (Cl. 9.3) (excluded for SF6 Gas filled CTs).
    (iv)           Multiple Chopped Impulse tests on primary (as per Annexure  B of IEC
                   44-1)
12.3.ACCEPTANCE AND ROUTINE TESTS:
       All acceptance and routine tests as stipulated in the IEC 60044-1 of latest
version shall be carried out by the supplier in presence of TANTRANSCOs
representative. In addition the capacitance and tan delta tests should also be
conducted. The measured values shall be engraved in the name plate.
12.4. Immediately after finalization of the programme of acceptance / routine
testing, the supplier shall give at least fifteen days advance intimation to the
TANTRANSCO, to enable to depute its representative for witnessing the tests.
12.5. The type test reports to be submitted for 800/420 KV Current Transformers
shall be as follows :-
       (1)           Short time current test.
       (2)           Temperature rise test.
       (3)           Lightning Impulse Voltage Test.
       (4)           Wet Test for outdoor type Current Transformers (as per clause 7.4 of
                     IEC 44.1).
       (5)           Determination of errors.
       In addition to the above reports following special tests as per IEC 60044-1
       on the Current Transformers should also be submitted along with techno-
       commercial bid.
       (i)           Chopped lightning Impulse Test as per clause 9.l of (IEC 44-1).
       (ii)          Measurement of capacitance and Die electric dissipation (as per
                      clause 9.2 of IEC 44-1) (excluded for SF6 Gas filled CTs).
           (iii)     Mechanical tests (as per clause 9.3 of IEC 44-1).
       (iv)          Multiple chopped Impulse tests on primary (as per Annexure-B of IEC
                     44-1)
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          It may please be noted that the above test reports should be submiited
          along with offer.
Routine Test: a) Following routine tests shall be carried out in the presence of
                TANTRANSCOs officer.
      (i)    Verification of terminal markings.
          (ii)       Power Frequency with stand test on primary and secondary windings.
          (iii)      Partial discharge measurement (as per clause 8.2.2 of IEC 44-1).
          (iv)       Power frequency withstand test between section (as per clause 8.3
                     of IEC 44-1).
          (v)        Interturn voltage test as per clause 8.4 of (IEC 44-1).
          (vi)       Determination of errors.
12.6 TESTING FACILITIES :
          The bidder should have all the facilities available in house to carry out high
voltage power frequency tests, tan delta and capacitance               measurement as per
specifications for these parameters narrated in various clauses and stipulated in
IEC 44-1 and 44.2. The bidder must have partial discharge measurement facility
suitable for measurement as per IEC 44-1 class 8.22. The instrument used for PD
measurement should be calibrated from Government Lab/Govt. approved lab and
calibration reports must be furnished with the offer. The bidder should furnish a
statement clearly indicating the particulars of testing equipments, their make, year
of manufacture, rating etc.              Please note that offers not complying these
requirements are liable for rejection.
13.0. INSPECTION:
    (I)           The TANTRANSCO shall have access at all times to the works and all
                  other places of manufacture, where the Instrument Transformers are
                  being manufactured and the supplier shall provide TANTRANSCOs
                  representative all facilities for unrestricted inspection of the works, raw
                  materials, manufacture of all the accessories and for conducting
                  necessary tests.
    (II)          The supplier shall keep the TANTRANSCO informed in advance of the
                  time of starting and of the progress of manufacture of equipment in its
                  various stages so that arrangements could be made for inspection.
    (III)         No material shall be despatched from its point of manufacture unless the
                  material has been satisfactorily inspected and tested.
    (IV)          The acceptance of any quantity of the equipment shall in no way relieve
                  the supplier of his responsibility for meeting all the requirement of this
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        specification and shall not prevent subsequent rejection if such
        equipment are later found to be defective.
14.0. PACKING AND FORWARDING:
14.1.    The equipment shall be packed in crates suitable for vertical/horizontal
Transport, as the case may be and suitable to withstand handling transport and
outdoor storage during transit. The supplier shall be responsible for any damage to
the equipment during transit due to improper and inadequate packing and
handling. The easily damageable material shall be carefully packed and marked
with the appropriate caution symbols. Wherever necessary, proper arrangement for
lifting, such as lifting hooks etc., shall be provided. Any material found short
inside the packing cases shall be supplied by supplier without any extra cost.
14.2. Each consignment shall be accompanied by a detailed packing list containing
the following information.
        (a) Name of the consignee.
        (b) Details of consignment.
        (c) Destination.
        (d)Total weight of consignment.
        (e) Handling and unpacking instructions.
       (f) Bill of material indicating contents of each package.
15.0. LIST OF DRAWINGS AND DOCUMENTS:
        All drawings shall conform to relevant international standards organization
(ISO) specification. All drawings shall be in ink and suitable for micro filming.
        All dimensions and data shall be in S.S.I units.
15.1.The Bidder shall furnish the following drawings along with his offer.
      (a) General outline and assembly drawings of the equipment.
      (b) Graphs showing other performance of equipments in regard to
          magnetization characteristics.
      (c) Sectional views showing.
      .   (i)General constructional features.
          (ii) Materials/Gaskets/ sealings used.
          (iii) The insulation of the winding arrangements, Method of connection
              of the primary/secondary winding to the primary/secondary
              terminals etc.,
       (d) Schematic drawing.
       (e) Type test reports.
       (f) Test reports, literature, pamphlets of the bought out items and raw
           materials.
15.2. The supplier shall within 2 weeks of placement of order, submit four sets of
all   the above drawings for TANTRANSCOs approval. The TANTRANSCO shall
communicate its comments/approval on the drawings to the supplier within
reasonable time.
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        The Supplier shall, if necessary, modify the drawings for TANTRANSCOs
approval within two weeks from the date of TANTRANSCOs comments. After
receipt of TANTRANSCOs approval, the supplier shall within three weeks, submit 6
prints and two good quality reproducible of the approved drawings for
TANTRANSCOs use.
15.3 Adequate copies of acceptance and routine test certificates, duly approved by
    the TANTRANSCO shall accompany the dispatched consignment.
15.4 The manufacturing of the equipment shall be strictly in accordance with the
    approved drawings and no deviation shall be permitted without the written
    approval of the TANTRANSCO. All manufacturing and fabrication work in
    connection with the equipment prior to the approval of the drawing shall be at
    the suppliers risk.
15.5 The following shall be supplied to each consignee circle along with the initial
    supply of the equipments ordered.
      i)Ten copies of printed and bound volumes of operation, maintenance and
         erection manuals in English along with the copies of approved drawings
         and type test reports etc.
      ii) Three sets of the Manuals detailed in item (i) shall be supplied to the
          SE/Transmission  I within one week from the date of approval of
          drawings.
16.0. ASSEMBLY:
During manufacture strict quality control should be adopted. The equipment
should be dried under vacuum in the hot chamber. Voids should be avoided to
minimize partial discharges. Suitable Transformer oil should be filled up under
vacuum immediately after drying is over. Oil filling and drain plugs may be
provided.
17.0. JUNCTION BOXES:
       Absolutely vermin proof fabricated from MS sheet of thickness 3mm
minimum Junction boxes with IP 55 Degree of protection are to be supplied one
each along with a set of 3( three) numbers Current Transformers. Boxes have to be
provided with belt / rubber beadings and doors opening with wing nuts for
lockings.
       It should be Hot dip galvanized. It should be provided with stud type
terminal blocks with lock nuts and washers. Boxes should have necessary provision
with cable glands for connecting 20 Nos. 4 Sq. mm, 4 core cables and 2 Nos. 4
sq.mm 8 core cables. All sharp corners should be rounded off. Boxes should have
sufficient working spaces for easy working and spaces for easy wiring and using
testing instruments such as tong test milli ammeters. Provision to be made for
double earthing arrangement by through bolts from inside to outside.
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