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MAIN CHARACTERISTICS AND TECHNICAL DATA - hhi Technical data.pdf  Transformer manufacturer...

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  • MAIN CHARACTERISTICS AND TECHNICAL DATA

    740 ENGEA-

    Sofia Bulgaria

    2008

    ON-LOAD TAP-CHANGERSOF HHI-B

  • EA-740/08 ENG

    2

    Contents

    Main characteristics and technical data. General .................................................................................4

    1. Application and operating principle

    1.1 Electrical diagrams and operating sequence .....................................................................5 1.2 On-load tap-changer basic units and transformer tank building-in method .....................7 1.3 Basic regulation schemes .................................................................................................8

    2. Technical characteristics of the on-load tap-changers ...............................................................9

    3. Insulation system of the on-load tap-changers

    3.1 Design characteristics .....................................................................................................10 3.2 Insulation system requirements ......................................................................................10

    4. Current-carrying system of the on-load tap-changers

    4.1 Design characteristics and general requirements ............................................................11 4.2 Temperature rise of contacts ...........................................................................................12 4.3 Short-circuit current test .................................................................................................12 4.4 Use of parallel current carrying paths .............................................................................13 4.5 OLTC overloading ..........................................................................................................13

    5. Switching system of the on-load tap-changers

    5.1 Admissible switching duties ...........................................................................................13 5.2 Special switching duty ....................................................................................................14 5.2.1 Switching with contact sets, connected in parallel .........................................................14 5.2.2 Switching at winding with coarse tap .............................................................................15 5.3 Switching problems at changing-over of tapped or coarse winding ...............................16 5.4 Transition resistors .........................................................................................................17

    6. Mechanical system of the on-load tap-changes

    6.1 Basic mechanisms in the tap-changer .............................................................................18 6.2 Motor-drive units and accessories ..................................................................................18

  • 3

    7. Operating conditions and protection of on-load tap-changers

    7.1 The most important about the operation .........................................................................20 7.2 Protective devices ..........................................................................................................21

    8. Mounting of the on-load tap-changers and motor-drive units to the transformer

    8.1 Basic mounting diagrams ...............................................................................................21 8.2 Connection of the on-load tap-changer to the motor-drive unit .....................................22

    9. Type and routine tests of the on-load tap-changers

    9.1 Type tests ........................................................................................................................23 9.2 Routine tests ...................................................................................................................23 9.3 Quality control ................................................................................................................23

    10. Selecting the on-load tap-changer ............................................................................................24

    11. Appendix ....................................................................................................................................26

  • EA-740/08 ENG

    4

    GENERAL

    Operating principle of the manufactured by Hyundai Heavy Industries-Bulgaria on-load tap-changers (OLTCs), technical parameters and data, that refer to all them and application methods are given in this general specification. The specific data for each type of OLTCs are represent in the particular type specifications.

    Transformer manufacturer could select the necessary OLTC from the general specification and the particular type specifications.

    For proper OLTC selection, the transformer manufacturer should fill up an order specification, which should be confirmed by Hyundai Heavy Industries-Bulgaria (HHI-B). After transformer manufacturer has already done the order according to agreed specification, he is responsible for the correct OLTC selection. HHI-B keeps their rights to make changes in the general and particular type specifications for the manufactured by HHI-B OLTC.

    The data in the general specification are referred to OLTC types: RS5, RS6, RS7, RS9, RS12, RS16 and RS18, which operate by the classical resistor type of tap-changer diagram of switching and for RS21, RS22, RSV5, RSV9 and, RSV20 which are provided with vacuum diverter switches.

    Note:Drawings, diagrams and technical data in this brochure are subject to changes without prior notice.

  • EA-740/08 ENG

    6

    The operating sequence of the OLTC con-tact elements from Fig. 1 can be represented by cyclogram or circle diagram as shown on Fig. 3.

    The circle diagrams are used when the cycle of one tap-change operation is counted within one revolution. To follow up the operation of the change-over selector on Fig. 3a a tap change operation from 10-th to 11-th position is represented. The corresponding angles are: 1 N1 starts moving; 2 N1 opens; 3 N1 closes; 4 N1 stops moving; 5 diverter switching start; c operating angle of divert-er switch (represented enlarged); p angle of operation of the change-over selector.

    When reversing (Fig. 3b), only switching of diverter switch (c) is carried out. This is accomplished by a connector with death zone of action for angle 0 in the kinematic chain between diverter switch and tap selector.

    The HHIB motor-drive unit (MDU) makes 33 revolutions of the driving shaft for a tap-change operation from one tap to adjacent one. In this case the opening and closing of the contact elements, read as rotation number n, can be represented by the cyclogram on Fig. 3c. The cyclogram is taken for every manufactured OLTC and the results are recorded in the routine test certificate.

    The HHIB diverter switches are high-speed resistor type with arc-quenching in transformer oil. They oper-ate according to the flag cycle diagram. Operating sequence of the contact elements represented by switch-ing cyclogram and phasor diagram is shown on Fig. 4.

    Fig. 3a operating sequence shown by circle diagramFig. 3b circle diagram at reversingFig. 3c linear showing of operation by cyclogram

    -

    +

    K1'

    N1

    K1

    N2

    Fig. 3c

    n

    C

    4 3

    1

    5

    + 1

    Fig. 3a

    2

    1 5

    - p

    +p

    P

    Fig. 4Operating sequence of resistor type diverter switch

    Fig. 3b

  • 7

    Switching duration for different types of diverter switches is within the range of 2845 ms. Switching oscillograms in both directions are given in routine test certificates. The phasor diagram is represented for given power factor (cos ) and reflects the cases of tap-change operation at raising and lowering, where Uc step voltage, Ip through current; Ic circulating current.

    HHIB produces also OLTCs with diverter switches using vacuum interrupters (VIs). The basic scheme is with three VIs, one resistor R and a switching unit S (Fig. 5).

    Main VIs (V1 and V2) interrupt the through current and transition VI (V3) interrupts the circulating current which is limited by the resistor R to be smaller than the through current. Thereby the electrical wear resistance of the diverter switch is increased. Diagrams with special design of S and such with two VIs are applied. They are represented in the technical materials of on-load tap-changers for which they are related to.

    1.2. On-load tap-changer basic units and transformer tank building-in method

    The HHIB OLTCs are designed for trans-former tank installation (Fig. 6). The OLTC is immersed in the transformer tank (10) oil (11), close to transformer active part (16) so that the leads between tap winding and tap se-lector are as short as possible.

    R2UI cc =

    Fig. 5Basic scheme of diverter switch with VIs

    Fig. 6 OLTC built in the transformer tank

  • EA-740/08 ENG

    8

    The basic units of the OLTC are: diverter switch oil vessel 1, diverter switch 3, tap selector 5, change-over selector 6 and MDU 7. The MDU is side mounted to the tank 10 wall. The MDU motion is trans-ferred by means of cardan coupler 8, vertical shaft 9, bevel gear 12 and horizontal shaft 13 to the worm gear 14 on the tap-changer carrying flange. Further the motion is transferred to the vertical insulation shaft 2 and the mechanism 4, which coordinates the operation of the diverter switch, tap selector and change-over selector.

    The diverter switch has three main components: transition resistors 3.1, contact system 3.2 and spring energy accumulator 3.3.

    The diverter switch oil vessel 1 is protected by oil-flow protective relay 15, connected by a p

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