The Rockwill RDS series outdoor high voltage disconnector is available in 420 kV and 550 kV ratings for three-phase AC transmission systems. It adopts a single-column single-arm vertical telescopic structure, where a conductive arm extends vertically upward from the top of a single insulator column to make contact with the upper busbar, and retracts downward when opened to form a visible isolating gap.
This vertical telescopic design is purpose-built for busbar disconnector applications. The entire disconnector mounts directly beneath the overhead busbar, occupying a single foundation position and requiring substantially less substation footprint than horizontal-opening designs. Each phase consists of a galvanized steel base, a single post insulator, a telescopic conductive arm assembly, and a CJ11 motor operating mechanism.
The RDS-420 and RDS-550 are widely used in EHV substations for busbar isolation, bus-transfer current switching, and maintenance disconnection. The vertical telescopic configuration enables direct busbar connection without intermediate structures, simplifying substation layout and reducing overall bay width. A JW10/JW8 earthing switch can be installed at the lower layer for busbar grounding.
Key Features
Single-column vertical telescopic structure：The conductive arm extends vertically from a single post insulator, eliminating the need for multi-column supports and reducing the number of live-part components
Direct under-busbar mounting：Designed to install directly beneath the substation busbar, requiring only one foundation per phase and significantly reducing bay width compared to horizontal-opening disconnectors
Compact substation footprint：The vertical motion path fits within the insulator column envelope, enabling tighter phase spacing and more compact substation layouts in EHV switchyards
Visible isolating gap：When open, the retracted arm and exposed insulator provide a clear visual indication of the disconnection state, meeting safety requirements for maintenance isolation
Integrated earthing provision：The lower-stage earthing switch connects directly to the telescopic arm assembly, enabling reliable busbar grounding within the same bay footprint
Proven EHV insulation coordination：Designed for 420 kV and 550 kV class with power-frequency, lightning impulse, and switching impulse withstand levels meeting stringent transmission substation requirements per IEC 60071-1
Low-maintenance operating mechanism：The CJ11 motor mechanism features grease-sealed gearboxes and corrosion-resistant enclosures, minimizing routine maintenance in outdoor EHV environments
IEC 62271-102 compliant：Fully type-tested in accordance with IEC 62271-102 for disconnectors and earthing switches
Technical Parameters
Item
Unit
420 kV
550 kV
Rated voltage (Um)
kV
420
550
Rated frequency
Hz
50 / 60
50 / 60
Rated normal current
A
4,000
4,000
Rated short-time withstand current (3 s)
kA
63
63
Rated peak withstand current
kA peak
160
160
Rated power-frequency withstand voltage (1 min), phase to earth
kV
520
620
Rated power-frequency withstand voltage (1 min), across isolating distance
kV
520 + 315
620 + 315
Rated lightning impulse withstand voltage, phase to earth
kV peak
1,425
1,550
Rated lightning impulse withstand voltage, across isolating distance
kV peak
1,425 + 445
1,550 + 445
Rated switching impulse withstand voltage, phase to earth
kV peak
1,050
1,175
Rated switching impulse withstand voltage, across isolating distance
CJ11 motor mechanism (single-pole, three-pole linkage supported)
Earthing switch actuator
CJ11 motor or manual
Motor voltage
AC 380 V / DC 220 V
Control voltage
AC 220 V / DC 220 V / DC 110 V
Opening / closing time
12 s ± 1 s
Application Scenarios
EHV transmission substations：Busbar isolation in 400 kV and 500 kV class transmission switchyards where space is at a premium
Substation brownfield upgrades：Direct replacement for existing vertical telescopic disconnectors using the same foundation layout, minimizing outage duration during substation refurbishment
Compact GIS-hybrid switchyards：Vertical telescopic disconnectors serve as the air-insulated busbar disconnector in hybrid arrangements combining GIS and AIS equipment
Hydroelectric and pumped-storage plants：Space-efficient busbar isolation in confined underground substations and powerhouse switchyards
Industrial EHV take-off substations：Busbar disconnection for large industrial loads requiring direct 400 kV or 500 kV transmission access
Order Information
When ordering, specify:
Product model (RDS-420 or RDS-550) and rated current
Voltage class
Insulation level (standard or enhanced)
Creepage distance requirement (standard or heavy-duty)
Earthing switch configuration (none, single, or both sides)
Earthing switch operation (motor or manual)
Upper busbar type (tubular or strain) and terminal connector type
Motor voltage and control voltage
Number of auxiliary switch contacts
Altitude and pollution level (if different from standard)
Main Categories: Medium and High Voltage Switchgear/Power and Distribution Transformers/Instrument Transformers and Sensors/Lightning Protection and Electrical Insulation/Substations and E-Houses/Electrical Panel and Controlgear
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