DESIGN CONCEPTS OF 33/11kV NEW SUBSTATION by HC120211191714

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									DESIGN CONCEPTS
 OF 33/11kV NEW
  SUBSTATION
    Planning 33/11kV Sub-Station
   A- Decision of location
   a-The location should be best suited at the load
    centre of the 11kV net-work
   b-Load density and voltage-regulation.
   c-Capacity of the substation should be decided
    keeping in view the future growth of the load
    for at least next 5years without needing any
    augmentation.
                      Cont’d
   d- Selection of the site of sub-station
   (i) Site should be free from all obstructions
    with the convenience of terminating H.V.
    lines.
   (ii) Site should not be in a low-lying area
    otherwise it may get flooded during rainy
    seasons.
   (iii) Site should be as near to the main roads as
    possible and easily approachable in all the
    seasons.
                   Cont’d
   (iv) As far as possible it should be near a
    town and away from garbage dumping
    ground to avoid vulture faults. Site should
    have drinking water facility. It should not be
    within 3 km from aerodrome. It should not
    be near military or police shooting ranges.
                   Cont’d
 There should have adequate land keeping in
(v)


  view the requirements for installation of
  required equipments-
   Land for 2x3MVA is approx 50x40metres
   For staff quarters Approx 3 acres
(vi) Land should be in level and should not have
  any nallah or road crossing on it.
(vii) The site should be selected so as to
  accommodate the length of 11kv outgoing
  feeder to connect the existing net work. It
  should be possible to be taken out 4-5 numbers
  of 11kV feeders.
    Orientation of the Sub-Station

   It should be such that the incoming and
    outgoing feeders are easily accessible to the
    sub-station structures.
    Scope must be kept for future extension for
    additional feeders in future
            Planning the Layout

   Should be economical
   Ease of operation and maintenance
   Safety of operating professional
         Substation Equipments

   Structures
   Power transformers
   Circuit Breakers
   H.T. Fuses
   Isolating Switches
   Bus bar Arrangement
   Insulators
   Lightning Protection equipments-LAs
                       Cont’d
    Instrument transformers -Current and Voltage
     transformers for –
 (i) Protection System
 (ii)Metering system

       CONTROL Panels with Various types of relays
       and instruments
      Control room
      Cables-
(i)    Power cables
(ii)   Control cables
                    Cont’d
   Batteries for D.C. supply
   Station transformer
   Fencing / boundary wall, approach road,
    security hut etc.
   Earthing system

Facilities:
(i) Lighting
(ii) Fire-fighting equipment
(iii) Staff quarters
                     Structures

   Incoming – outgoing gantries
   Mounting structures for Power Transformers, Station
    Transformers, breakers, isolators, HT fuses, insulator
    supports ( For Post Insulators), C.Ts & P.Ts.
   Bus-bar structures to provide entry from the overhead
    line to the s/s and to extend required number of
    feeders (Bays). Similarly other structures required to
    mount the operating and other accessories. Minimum
    clearance from ground level and from any live part is
    to be maintained as per I.E. Rules.
                    continue
   Structure are fabricated from steel sections or
    rail and joist are used. P.C.C. poles cast in
    reduced length (up to 7 meters) with strength
    of 400kg are also being used for economy
    purposes.
           Power transformers

  Power Transformers with different capacities are -
(i) 630kVA 33/11 step-down (Delta/Dy11)
(ii)1600kVA
(iii)3150kVA
(iv)5000kVA
  Most of the Transformers are provided with off-circuit
   tap Changers.However On Load Tap Changers are
   being provided in the Power Transformers with
   capacity of more than 5MVA
          Protecting Devices
A Circuit Breakers
 (i) 33kV

 Oil type circuit breakers. Now being
  replaced with vaccum/SF6 circuit
  breakers
 Normal current - 630Amps voltage 36kV

 Rated short circuit current 25 kA for 3
  Sec
 Metering and protection panel gets
  signals through 11kV/110V PTs and CTs
  which are provided with separate cores
  for metering and protection System.
                   Cont’d
 (ii) 11kV
 Oil type circuit Breakers- Now being replaced
   with SF6 or Vacuum Circuit Breakers
 Normal current-400Amps and 800Amps

 Short circuit current-25kA for 3Secs
                   Continue
   Breaker panel is provided with motor operated
    spring charging mechanism which operates at
    230V single phase AC supply.
   Circuit breakers for Transformers of more than
    5MVA capacity are being provided. For lower
    capacity Transformers protection through HG
    fuses, on 33kV side are provided.
   Outdoor type CTs and PTs are provided for
    33kV system.
   CTs and PTs are supplied with 11kV breaker
    Panel
                    HT Fuse
   Normally drop out fuse cut outs for current
    rating of upto100Amps are being used. Fuses
    have insulated base / fitting arrangements with
    creep-age distance to earth not less than
    320mm
               Isolating Switches
Isolating Switches
-Switches are Used to isolate equipment for
  maintenance purposes

   33kV:
   For 33kV system horizontal type isolating switches
    are used. Rated normal current - 630A at 36kV.

   11kV:
    Two type IS Are being used
   (i) suitable for horizontal mounting
   (ii)suitable for vertical mounting ating
   Normal rating- 400amps- At 12kV
                 Bus Bars
 Two types of bus bars - Rigid and Strain
  type
 In rigid type- Pipes are used for bus-bar and
  also for making connections. These are
  supported on bus post insulators and requires
  large space.As the bus bars are rigid the
  clearance remain constant.
 Minimum ground clearance 3660mm from
  ground. Since the clearance is not high, the
  maintenance is easy.
 The strain type Bus bars are over head system
  of wires betn. Two supporting structures.
 Material-ACSR Racoon for 33kV and 11kV
  bus-bars
                     Cont’d
   33kV&11kV outgoing and incoming feeders
    kept at 6400mm for ground clearance. The
    other levels of live point in the s/s area are
    different heights but a minimum of 3660mm is
    to be maintained.
   11kV jumpers are kept at 4500mm height for
    ground clearance.
                 Insulators

  Adequate insulation is required for reliability
  of supply, safety of personnel and equipment
  etc.
 Number of insulators is kept minimum for
  aconomy reasons at the same time ensuring
  reliability and security of supply.
 Special insulator with higher leakage
  resistance to be used, where problem of
  insulator pollution is expected
           Lightning protection

   Metal oxide lightning arresters are used as they
    have gapless construction and respond to over-
    voltage without any time delay. They have
    longer life and higher energy handling
    capacity.
   Rated voltage 30kV for use on 33kV system
    and 9kV for use on 11kV. Nominal discharge
    current rating 10 & 5kA
      Instrument Transformers
  Current Tranformers are required for protection &
  metering system
 Standard ratings for 33/11kV S/S are

 300-150/5-5 or 5-5-1 Amps.
 200-100/5-5 Amps.

 100-50/5-5         Amps.
 50-25/5-5 Amps.
 Accuracy class for protection - 5P10 and for
  metering Class 1
 Oil filled or Resin cast CTs are being used depending
  upon application
                     Cont’d
   The CTs and PTs can be either Oil filled or
    resin cast depending upon the application
   Standard voltage ratio for PTs is 33kV / 110V
    or 11kV / 110V .
        Control and Relay Panels

  C&R Panels normally consist of
 Ammeter with selector switch

 Voltmeter with selector switch

 Energy meter

 IDMT Relays

 Differential Relay or REF relay for Transformer

  protection
 Various indications and Annunciations
                Control Room
   While designing control room requirement of
    space for batteries, battery charger, ADLS, one
    small store room should also be considered in
    addition to space for 33kV C&R Panels and
    11kV breaker panels along with sitting space
    for operating staff.
                 CABLES
   Care should be taken to segregate Power
    and control cables on separate racks so
    that in case of fire in power cables,
    control cables are not damaged and vice
    versa.
   The trenches should be designed for easy
    entry of cables and properly sloped so as
    to avoid accumulation of water.
   If possible segregation of AC and DC
    cables should also be considered.
   All cables should be labeled for proper
    identification and sheath should be
    earthed .
          Battery and Charger
   Normally 24/30 Volt, 150 AH lead acid or
    NICAD Battery banks are used.
   The Charger should be Single Phase AC
    operated Float cum Boost type having capacity
    of 5 Amps boost charging and 200 mA float
    Charging and should be fully automatic with
    alarm and indication system.
           Station Transformer
   Station Transformer with a capacity of 63 or
    100kVA capacity is normally sufficient to
    cater the needs of a 33/11kV substation.
   However higher capacity station transformer
    may be considered if supply is considered to
    be provided to the staff Colony.
              Other Facilities
   Boundary wall or Fencing
   Illumination of control room and switch yard
   Provision of Fire Extinguishers
                    Earthing
   Provision of adequate Earthing in a substation
    is a must for safety of operating personnel and
    proper operation of the syetm and protective
    devices.The primary requirements are –
   The earthing resistance should be as low as
    possible preferably less than 1 ohm.
              Earthing - cont’d
   Provision of earthing for following is made in a
    substation –
   Neutral point of each equipment / system such as
    transformer, capacitor bank, PT etc should have two
    independent earthings
   Earthing of equipment enclosures and non current
    carrying parts
   All metal frame works such as fencing wire mesh
    fencing pole illumination pole etc.
   Lightening arresters should also have two
    independent earthings.
             Earthing – cont’d
   Factors considered while designing Earthing-
   Duration of fault
   Magnitude of fault current
   Resistivity of underlying strata
   Resistivity of surface material
   Material of the earth electrodes
                    Conductors
                  Loading Capacity
    kW-km limit for Rabbit, weasel & squirrel
     conductors
                      0.8 P.F.   0.7 P.F.

   a. Rabbit        11970       10800
   b. Weasel        8100        7560
   c. Squirrel      5760        5445
          STANDARDISATION :
WHILE DESIGINING THE 33/11 KV SUBSTATIONS, THE
DESIGNOR HAS TO KEEP IN MIND THE NEEDS FOR
STANDARDISATION.

WHY STANDARDISATION,

     AVOIDING REPETATION OF DESIGN
     REDUCTION IN DRAWING APPROVAL TIME
     UNIFORMITY IN THE PRODUCTS
     REDUCTION IN PROJECT IMPLEMENTATIONTIME
     MINIMUM DOWN TIME
     INTERCHANGEABILITY
     COST EFFECTIVENESS
         STANDARDISATION :
   POTENTIAL AREAS FOR
    STANDARDISATION :
      LAYOUT
      STRUCTURES
      EARTHING
      CABLES & CABLE TRENCH
      BATTERY SIZING
      CLAMPS & CONNECTORS
      BUSBARS
      ILLUMINATION
      CONTROL, PROTECTION & METERING
      CONTROL ROOM
      ALL FOUNDATIONS
             Minimum Clearances
Voltage level Standar    For equipments     Phase to Phase spacing in
    (kV)       d bay        and rigid        isolators and switches
              widths    conductors in air
                (in     Phase    Phase to   Isolator     Switches with
               Mtrs.)    to       earth      (mm)         Arc Horns
                        phase     (mm)                       (mm)
                        (mm)
    132         9.5     1700      1000       2135            3050

    66          7       1220       750       1525            2135

    33          4.6     915        610        765            1220

    11          3.5     560        305        610             915

   0.415        --      380        305         --              --
             Other Parameters

Voltage     Basic       Minimum    Minimum     Section
 level    Insulation    creepage   clearance clearance
 (kV)       Level       distance   to ground    (mm)
          (BIL) kVp       (mm)       (mm)
 132      450 / 550 /      1125       4600   3500 / 4000
             650
 110       450 / 550      3075       4600    3500 / 4000

  66         325         1812.5      4600       3500

  33      145 / 170     560/900      3650    2750 / 3000

  11        60 / 75       300        3200    2600 / 2600
Thank You

								
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