GN27-40.5 Disconnector (indoor, 35 kV)

The GN27-40.5 indoor AC disconnectors are intended for off-load switching of network sections at 35 kV (Um = 40.5 kV, 50/60 Hz) and for safe earthing of de-energized circuits. The GN27-40.5 series are three-pole vertical-rotary (knife-type) devices with a flat layout, available as C (through-wall) and D (with integral earthing switch) variants, compatible with CS6-2/CS6-1 manual operators and the CX6 motor operator. The equipment complies with IEC 62271-102 for disconnectors and earthing switches.

Application and use cases

The GN27-40.5 provides visible isolation and operational earthing within 35 kV switchgear and is used for:

sectionalizing and isolating feeders in 35 kV indoor switchgear (incoming lines, OH/UG feeders, tie/transfer sections, bus couplers);
maintenance isolation of vacuum circuit breakers, instrument transformers, surge arresters and auxiliary circuits with visible isolation (off-load switching);
installation in metal-clad / metal-enclosed switchgear, modular substations and MV rooms with limited depth (flat layout simplifies integration);
use at renewable generation sites (PV, wind - sectionalizing of 35 kV collector buses, taps to step-up transformers);
industrial facilities in oil & gas, mining, metallurgy, data centers and other critical infrastructure (reliable maintenance isolation, cabinet/CB interlocking interface);
traction substations: sectionalizer/incoming disconnector on the 35 kV side with the integral earthing option (GN27-40.5D);
operation in polluted and humid indoor environments per IEC pollution class II (extended creepage distances and reinforced insulation).

Technical data and key insulation levels (IEC)

Rated voltage, kV	35
Rated maximum voltage (Um), kV	40.5
Rated current, A	630; 1250; 1600; 2000; 2500*
Short-time withstand current (4 s, kA rms)	20; 31.5; 40**
Peak withstand current, kA peak	50; 80; 100**
Power-frequency withstand (1 min), kV	95 (to earth/between phases); 115 (across open contacts)
Lightning impulse withstand (LI), kV	185 (to earth/between phases); 215 (across open contacts)
Mechanical endurance, O-C cycles	≥ 2000 (per IEC 62271-102)
Environmental / installation category	Indoor; IEC pollution class II

Typical values per manufacturer documentation for GN27-40.5 (40.5 kV; 630/1250 A; 20/31.5 kA; 95/115 kV and 185/215 kV insulation levels), with extended versions up to 2000–2500 A and 40/100 kA. ** - for 2000–2500 A ranges; * - availability depends on the manufacturer.

Service conditions

The GN27-40.5 is designed for indoor switchgear under service conditions typical for MV/HV equipment:

Installation: indoor (switchgear rooms, metal-clad/metal-enclosed cabinets, bus compartments);
Ambient temperature: -25 °C to +40 °C (typical) without condensation; other ranges subject to project/manufacturer specification;
Altitude: up to 1000 m (typical) or up to 2000 m with insulation corrections;
Relative humidity: daily average up to 95 %, monthly average up to 90 %; pollution class - II;
Seismic/wind impacts: per project specification; certain versions are qualified up to 8-degree seismic and winds ≈ 34 m/s.

Design and construction

The GN27-40.5 is a three-pole disconnector on a common base frame with vertical-rotary blades and a multi-finger contact system (self-cleaning, low contact resistance). Increased creepage distances (pollution II), high-strength support/rotary insulators, and bearing-supported shafts reduce operating torque and increase life. Available as with integral earthing switch (D/D2); horizontal/vertical/angled mounting is supported. Operators: CS6-2/CS6-1 manual or CX6 motor operator with auxiliary position switches.

Assembly	Function	Key features
Base frame	Support for three poles and operator	Welded; high stiffness; adjustment points
Support/bushing insulators	Dielectric insulation and mechanical support	Porcelain/epoxy; extended creepage (pollution II)
Rotary blade	Provides visible isolation	Knife-type; bearing-supported shafts; high dynamic strength
Contact system	Reliable current path in CLOSED/EARTHED	Multi-finger contacts; self-wiping; low transition resistance
Earthing switch (D option)	Operational earthing of the isolated section	Mechanical interlock with main blade
CS6-2/CS6-1/CX6 operator	Positions “CLOSED/OPEN/EARTHED”, status contacts	Sealable; limit switches; key/mechanical interlocks

Mechanical interlocks prevent incorrect sequences: closing the main blade with the earthing switch engaged (and vice versa) is blocked; cabinet and breaker interlocks are available to meet safety practices per IEC 62271-102.

Variants and options

The GN27-40.5 is supplied for diverse applications and markets (China, Africa, Asia, Europe, USA):

GN27-40.5 (without earthing switch), GN27-40.5C/C2 (through-wall), GN27-40.5D/D2 (with earthing switch) - left/right operator mounting;
operators CS6-2/CS6-1 (manual), CX6 (motor) with OPEN/CLOSED/EARTHED auxiliary contacts;
connection options: bus bars, cable lugs, flexible bars;
position sensors/limit switches for SCADA and protection I/O;
extended current ratings up to 2000–2500 A for heavily loaded sections.

Option	Description	Purpose/notes
Integral earthing switch (D)	Earthing blade with hard interlocking	Operational earthing; visible earthing point
Through-wall (C/C2)	Fixed/moving side through a partition	Optimized layout of bus/cable compartments
Motor operator (CX6)	Three-position electric drive	Remote control and interlocking via SCADA
Auxiliary limit switches	Dry contacts for OPEN/CLOSED/EARTHED	Status signalling, logic interlocks
Connection variants	Bus bars / lugs / flexible bars	Project/market-specific unification

Standards compliance

Design and manufacture of GN27-40.5 follow IEC 62271-102 (AC disconnectors and earthing switches) and IEC 62271-1 (common specifications). For North American projects, application and testing may reference IEEE/ANSI C37.30.1 (requirements for AC high-voltage air switches), IEEE/ANSI C37.32 (preferred ratings) and IEEE C37.34 (test code).

Contracting & partnership

We cooperate with 35 kV switchgear manufacturers and integrators across China, Africa, Asia, Europe and the USA: design package transfer, adaptation to local components and practices, assistance with type tests (per IEC 62271-102) and commissioning.

Documentation offered

Available: inquiry forms, specifications, 3D models (STEP/IGES), drawings (DWG/DXF), I/O and interlock diagrams, assembly/adjustment instructions and test programs; documentation can be tailored to project needs (connection dimensions, operator type, limit-switch placement, etc.).

Benefits of working with us

- A ready-to-manufacture package for GN27-40.5 with minimal rework.
- Serial launch experience, support during tests and commissioning.
- Guidance on insulation levels (95/115 kV; 185/215 kV), current ratings and interlocking to meet IEC/IEEE requirements.