GW4 Porcelain Disconnecting Switches
Center-Break – 11-40.5kV – 630-1250A – Visible Gap Isolation
Outdoor AC high-voltage disconnector with porcelain insulators and center-break contact configuration per IEC 62271-102. Self-cleaning silver-plated copper contacts, manual or motorized operation, optional earthing switch. For substation busbar isolation and equipment disconnection.
OEM / ODM – Low-MOQ samples – Type-test reports
Overview
The GW4 series center-break disconnecting switch is the most widely deployed medium-voltage outdoor isolator in Chinese substations and distribution networks. Its defining characteristic is the double-column, horizontal-rotation design: two porcelain insulator columns per phase mount on a galvanized steel base, each carrying a copper contact arm. When the mechanism rotates both columns outward (91 degrees each), a clear, unambiguous visible isolation gap opens in the center — satisfying the fundamental safety requirement that line crews can visually verify de-energized equipment before working on it.
Key design principle: the switch does not interrupt current. It provides isolation only after the circuit has been de-energized by an upstream circuit breaker. Attempting to open a standard GW4 under load will draw a dangerous arc that can flash across phases. For load-breaking capability, the RH-B load-break variant (see our Load-Break sub-page) adds expulsion-type interrupters.
The self-cleaning contact design uses a multi-finger silver-plated copper jaw with a defined wiping action during rotation — each operation scrapes oxidation off the contact surfaces, maintaining low contact resistance over decades. No external springs in the current path (a common failure point) — current flows exclusively through copper.
Best for: Substation busbar section isolation, transformer disconnection for maintenance, feeder incoming isolation in RMUs. For outdoor pole-top installations in polluted environments, see Polymer/Composite GW4 series.
Technical Specifications
| Rated Voltage | 12 kV (Um=12) / 40.5 kV (Um=40.5) |
|---|---|
| Rated Current | 630 A, 1250 A (2000 A/2500 A on request) |
| Rated Short-Circuit Withstand (3s) | 16-31.5 kA rms |
| Peak Withstand Current | 40-80 kA |
| BIL Phase-Ground | 75 kV (12kV) / 185 kV (40.5kV) |
| BIL Across Open Contacts | 85 kV / 215 kV |
| Power Freq Withstand Dry | 42 kV / 80 kV |
| Power Freq Withstand Across Gap | 48 kV / 90 kV |
| Creepage Distance (Std) | 625 mm |
| Creepage (Anti-Pollution) | 875 mm |
| Contact Material | Silver-plated copper, multi-finger self-cleaning |
| Insulators | High-strength glazed porcelain |
| Base Frame | Hot-dip galvanized steel |
| Opening Angle | 91 per column, 182 total visible gap |
| Operation | Manual linkage or motorized (remote) |
| Mechanical Endurance | 2,000 operations |
| Temperature / Altitude | -30/+40 C / <=1000m (3000m on request) |
| Standards | IEC 62271-102 / GB 1985 |
Range
| Model | Voltage | Current | SC Withstand | Peak | Weight (3-pole) |
|---|---|---|---|---|---|
| GW4-12/630 | 12 kV | 630 A | 20 kA | 50 kA | ~145 kg |
| GW4-12/1250 | 12 kV | 1250 A | 31.5 kA | 80 kA | ~165 kg |
| GW4-40.5/630 | 40.5 kV | 630 A | 20 kA | 50 kA | ~170 kg |
| GW4-40.5/1250 | 40.5 kV | 1250 A | 31.5 kA | 80 kA | ~195 kg |
Single-grounded and double-grounded (earthing switch) variants available. Manual (CS17 mechanism) or motorized (CJ6 mechanism) options.
Key Features
Both insulator columns rotate outward, creating a 182-degree total open gap. Instant visual confirmation that equipment is safely isolated — no instruments required.
Multi-finger silver-plated copper jaw with wiping action removes oxide buildup during every operation. Consistent low contact resistance (typically <40 microohm) over 30+ year service life without maintenance.
Load current flows exclusively through copper conductors. All mechanical springs are outside the current-carrying path — eliminating the most common thermal failure mode of older designs.
CS17 manual mechanism for local operation with interlock. CJ6 motorized mechanism for remote control from SCADA. Both with position indication and padlock points.
Single-side or double-side grounding options. Earthing switch interlocked with main blades: cannot close earthing switch unless main blades are fully open.
Full type-test suite: dielectric, short-circuit withstand, mechanical endurance, temperature rise. Reports available for substation tender submission.
Applications
Individual busbar sections isolated for maintenance without de-energizing the entire substation. The visible gap provides positive assurance.
On both HV and LV sides of power transformers. Allows safe access to transformer for testing, oil sampling, and bushing replacement.
Incoming feeder disconnection in ring-main units and compact substations. Manual operation with ground-level linkage.
Overhead line sectionalizing for maintenance and fault isolation. Pole-mounted with gang-operated manual mechanism.
Frequently Asked Questions
Can I open a GW4 under load?
What is the difference between GW4 and GW5?
How often should contacts be inspected?
Why porcelain over composite for indoor substations?
What is the earthing switch for?
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