High-voltage Isolation Switch
Outdoor isolation switches from 10 kV to 126 kV, in single or three-pole form, with or without earthing blades.
- Rated voltage
- 10–126 kV
- Rated current
- 200–2000 A
- Operation
- Manual or motor
- Earthing
- None, one side or both
An isolation switch does not break load current. It opens a visible gap so that a section of line or a transformer can be worked on, and it is operated only after the circuit breaker has cleared the circuit.
Three series are made: GW9 for 10–20 kV pole-top work, GW4 for 40.5–126 kV, and GW5 for 40.5–126 kV in a V arrangement with a smaller footprint. All are three-phase units built from single poles.
The same frame can be supplied with earthing blades on one side or on both. That decides whether the earthing switch is part of the same operation or a separate one.
Reading the Type Code
The type reads as switch, location, design, voltage and current, with suffixes for earthing and site conditions:
- G
- Isolation switch; HG for a composite-insulated version
- W / N
- Outdoor / indoor installation
- 9
- Design number of the series
- 10 / 630
- Rated voltage, kV / rated current, A
- D / DD
- Earthing blade on one side / on both sides
- G / W
- High-altitude version / anti-pollution version
Specifications
GW9 series, 10 kV to 20 kV. Insulation values are power-frequency and lightning impulse, to earth and across the open gap.
| Type | Rated voltagekV | Maximum operating voltagekV | PF withstand to earthkV | PF withstand across gapkV | Impulse withstand to earthkV | Impulse withstand across gapkV |
|---|---|---|---|---|---|---|
| GW9-10 | 10 | 12 | 40 | 47 | 105 | 120 |
| GW9-15 | 15 | 17.5 | 45 | 50 | 105 | 120 |
| GW9-20 | 20 | 23 | 50 | 60 | 125 | 145 |
Rated current for the GW9 series is 200, 400, 630 or 1 250 A; the 4 s thermal current 6.3, 12.5, 20 or 31.5 kA; the dynamic current 16, 31.5, 50 or 80 kA, in the same order. The catalogue does not give a creepage figure for this series. GW4 and GW5 switches are made for 40.5 kV, 72.5 kV and 126 kV; their parameter sheets are not reproduced here.
Choosing a Type
Three Series
GW9 covers 10–20 kV on poles; GW4 and GW5 cover 40.5–126 kV in substations, the GW5 in a V arrangement that takes less depth.
Earthing Blades
D adds an earthing blade on one side, DD on both. The earthing switch carries residual current; it is not a load-breaking device.
Operating Mechanism
Manual CS-type mechanisms are standard; CJ and CX motor mechanisms are fitted where the switch is operated from a control room.
Every switch is routine-tested before it is packed, and each type is type-tested before it is offered for supply.
Ask about High-voltage Isolation Switch
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