We all know and have seen DP structures in Rural as well as Urban Infrastructure in India. The following is an indicative photograph for the same.
The arrangement consists of following components:
1) Lightning Arrestor
2) Air Break Switch
3) Dropout Fuse
The structure looks shabby and becomes an eyesore in the era of plush residential and commercial complexes. Moreover, it has lot of shortcomings which we shall discuss here. All the factors combined make it an obsolete solution which needs to be replaced asap. We shall discuss the product which should replace it and bring in better aesthetics and protection, Load Break Switch.
A load break switch combines an on load isolator with snap action mechanism with main contacts and arcing contacts. It consists of incoming and outgoing busbars with arc chutes. The switch is operated through stored energy mechnaism through spring charging.
The protection is provided through HT HRC fuses of suitable rating. The switch is normally provided with Fuse trip mechanism which opens all 3 phases in case of any fault. The product can have additional accessories like Shunt trip, Earth Switch and Interlocks.
The switch is generally fitted inside either Indoor or Outdoor Enclosure as below.
It can be clearly observed that Load Break Switch is a more compact, aesthetically better and safer solution as compared to a Double Pole Structure. The following table lists the clear advantages and differences between the two
DP Structure | Load Break Switch | |
Installation | Only Outdoor | Indoor as well as Outdoor versions available |
Labor | More labor needed | Comparatively much less labor needed |
Time | At least a week needed for Installation | Installation can completed within a day |
Operation | Emergency off facility is not available | Emergency off facility is available |
ON/OFF can only be verified physically | ON/OFF indication is through bright LED lamps | |
Closing/Opening time may vary phase-to-phase | Same closing/opening time for all phases | |
Closing/Opening time depends on operator | Same closing/opening time irrespective of operator | |
Safety | Arcing may occur in air which endangers operator | Arc is extinguished inside arcing chamber thus ensuring operator safety |
Fuse flashover may lead to fire hazards | Completely enclosed assembly eliminates any fire hazards | |
Blowing of a fuse causes single phasing | Fuse trip mechanism opens all three phases in case of fuse blowing thus eliminating single phasing |




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