12kv, 1250A Disconnecting Switch with Operation Rod Which Is Fixed with Insulator

 
Type IST off-load switchs are suitable for use in tropical zone, with a maximum ambient temperature of approximately 40
degrees Centigrade and an average temperature of approximately 28 degrees Centigrade with high humidity and heavy rainfall.
The preferred operational altitude is up to 1800 m above sea level.
1.0                        Scope & applications
 
1.1       The  pole-mounted Line Sectionalizer / Disconnector are open type, air insulated switch. The make and Break switching operation are performed at "zero system voltage." in "OFF LOAD"     condition, only for the isolation of the faulty circuits for the protection of 11 KV Distribution lines,   Transformers, Capacitors, Cables,  etc, from high transient lightening and surge Voltages.
 
1.2       The assembly of Gang operated three phase Pole Mounted Line Sectionalizer are supplied as a        single unit with single pole mounting arrangement. The unit are facilitate the installation of the   assembly on both sides (left or right) of the pole to operate and install the operating handle in        accordance with site conditions.     
 
2.0       System / conditions
 
i)                    Nominal system voltage                                     11 KV
ii)                  Highest system voltage                                      12 KV
iii)                Highest voltage for equipment                                  12 KV
iv)                BIL                                                      95 KV
v)                  Phases                                                  3 
vi)                Frequency                                            50 Hz
vii)              Rated Short circuit level of the system                      18 KA (1 second)
viii)            System Earthing: 11 KV Star point / Neutral solidly grounded at Pole / PMT:
 
3.0       Climatic conditions
 
i)                    Maximum ambient air temperature                           50oC
ii)                  Maximum daily average temperature                     45oC
iii)                Minimum ambient air temperature                            0oC
iv)                Maximum sun temperature on exposed Horizontal surface   60oC
v)                  Highest solar radiation intensity                                1000 W/m2
vi)                Maximum relative humidity                               95 %
vii)              Annual rain fall:                                                                     20 to 60 mm in 2 to 4                                                             showers
viii)            Altitude                                                           Sea-level
ix)                Location                                                           Sea Coast (Interior is                                                       Semi-Desert).
x)                  Pollution                                             Severe marine pollution on                                                    account of windblown                                                              sand and dust with salt                                                           content and salt laden                                                               spray and mist. Washing                                                    action by rain is negligible,                                                    as rainfall is scanty.
 
4.0      Ratings and characteristics for line Sectionalizer
 
4.1       The Gang Operated pole mounted 11 kv Line Sectionalizer have the following ratings and characteristics based on 50 deg. C ambient temperature:
 
i)                                Nominal voltage                                                    11 KV
ii)                              Maximum design voltage                                                      12 KV
iii)                            Rated continuous current                                                    630  Amps
iv)                            Impulse withstand voltage to ground                               95 KV
v)                              Impulse withstand voltage across gaps                                   110 KV
vi)                            Dry one-minute power frequency withstand voltage to ground           35 KV
vii)                          Dry one minute power frequency withstand voltage across gap           45 KV
viii)   Wet one minute power frequency withstand voltage to ground         30 KV
ix)                            Limits of radio interference 10KV  and 1000 K.C/Sec                 250  uV
x)                              Temperature rise at rated current (max.)                                           30oC at 50oC ambient
 
 
4.2       Polymer insulator
 
The mechanical and electrical characteristics of the Polymeric insulator are as under:
 
 
 
 
 
4.2.1    Dimensions and mechanical values
 
i)                    Leaking distance                                         508 mm  (minimum)
ii)                  Dry arcing distance                                     210 mm  (minimum)
iii)                Cantilever strength                                      400   kg
iv)                Tensile strength                                           1000 kg
v)                  Compressive strength                                         5400 kg
vi)                Tensile proof test load                                       700   kg
                  
4.2.2    Electrical values
 
i)                    Dry power frequency flashover                                85  KV
ii)                  Wet power frequency flashover                               55  KV
iii)                Dry one-minute power frequency withstand                    70  KV
iv)                Wet one-minute power frequency withstand                   45  KV
v)                  Impulse flash over positive                                      115  KV
vi)                Impulse flashover negative                                140  KV
vii)              Power frequency puncture voltage                           150  KV
 
 
5.0       Constructional features
The three pole disconnectors are mainly designed for a vertical mounting. The following elements could be changed or incorporated:
- Fuseholder.
- Earthing connection with locking device to prevent the connection to earth when the disconnector is closed or to close the device when the earth is connected.
- The earthing disconnector can be placed in the entrance or exit of the main switch.
- The earth disconnector is operating by means of an independent control.
- The operating axis could be placed at left or  right side.
- The operating axis could be extending until 250, 420,500, 750 or 1000mm, these extensions includes a support to avoid it bend down.
- The outdoor units are provided with different drills to permit the direct fixing to a post or to a frame previously fix to a post.