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Chapter 1 of 12 • Page 1 of 248🔒 Protected PDF • Watermarked
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Which is not a type of isolator?
Vertical brake
Horizontal brake
Horizontal pentograph
Vertical pentograph
Horizontal pentograph
Quick Summary: Isolators are mechanical switching devices used for isolating a circuit or equipment from the power source for maintenance or safety purposes. They are designed to operate only under no-load conditions. The 'Horizontal Pantograph' is not a standard configuration because the pantograph mechanism is inherently designed for vertical movement to reach overhead busbars while maintaining a compact footprint.
Isolators are mechanical switching devices used for isolating a circuit or equipment from the power source for maintenance or safety purposes. They are designed to operate only under no-load conditions. The 'Horizontal Pantograph' is not a standard configuration because the pantograph mechanism is inherently designed for vertical movement to reach overhead busbars while maintaining a compact footprint.
Vins≥1.1×Vline — Minimum insulation level requirement for isolator design
Pantograph isolators are used in high-voltage substations where space is a constraint. The mechanism uses a scissor-like linkage system that expands vertically to bridge the gap between the ground-mounted isolator base and the overhead busbar. A horizontal pantograph configuration is mechanically unstable and impractical for high-voltage dielectric clearances.
Isolators are 'off-load' devices and must never be operated under current load.
Pantograph isolators are ideal for EHV (Extra High Voltage) substations due to vertical busbar arrangements.
Vertical break isolators are the most common type used in distribution systems.
Horizontal break isolators require more horizontal clearance compared to pantograph types.
Pantograph types provide significant space savings in the substation yard.
Reduced busbar heights possible in layout design.
Pantograph mechanisms are more complex and require higher maintenance.
Not suitable for high-current applications due to mechanical link stress.
EHV Substations (400kV and above)
Switching of busbar sections in congested yard layouts
Standard classifications: Vertical Break, Horizontal Break, Pantograph, and Center Break.
The term 'Horizontal Pantograph' is technically non-existent as the pantograph design relies on vertical expansion for busbar engagement.
C is correct — Horizontal pantograph is not a recognized configuration as the pantograph isolator is specifically designed for vertical motion to engage overhead busbars.
Always remember that isolators lack arc-quenching chambers and must only be operated after the associated circuit breaker has successfully interrupted the load current.