GN30-12 Indoor Rotating Contact Knife HV Disconnector Thomas Electric

Product Overview

The GN30-12 is an indoor rotating-contact-knife high-voltage AC disconnector for three-phase 50 Hz systems rated 12 kV, applied in 10 kV class networks. Its three poles share one base frame carrying two sets of insulators and contacts on the upper and lower planes, and the knife rotates between them to open or close the circuit through a clear visible break. It connects, interrupts or transfers circuits under voltage but without load, in a metal-enclosed switchgear cubicle or as a standalone indoor isolator, in four current grades from 400 A to 1250 A; the GN30-12D adds an earthing switch.

Product Display

GN30-12 Indoor Rotating Contact Knife High-Voltage Disconnector - display

GN30-12 Indoor Rotating Contact Knife High-Voltage Disconnector - poster_display

Model Designation

GN30-12 Indoor Rotating Contact Knife High-Voltage Disconnector - model

Model format: G N 30 – 12 (D) / □ – □

G – disconnector
N – place of use: indoor
30 – design sequence number
12 – rated voltage, kV
(D) – with earthing switch
□ – rated current, A
□ – thermal-stable current (4 s), kA
Example: GN30-12D/630-20 is the version with earthing switch at 630 A and 20 kA for 4 s

Service Conditions

Altitude: not above 1000 m
Ambient temperature: upper limit +40 °C, lower limit -10 °C
Relative humidity: daily average not above 95%, monthly average not above 90%
Seismic intensity: not above 8 degrees
Site free from severe dust, chemical corrosion and explosive substances, and from frequent severe vibration

Construction

Each pole has two insulator-and-contact sets on the upper and lower planes of a common three-phase frame, and the moving knife rotates between them to make or break the circuit with a clear visible gap. The shared-frame layout saves panel space while keeping generous insulation distances, and the design is compact, has high insulating strength and is easy to install and adjust.

The D version integrates an earthing switch so the de-energised side can be earthed for maintenance, and it shares the electrical ratings of the corresponding GN30-12 current grade. Operation is by a manual mechanism interlocked with the associated circuit breaker; the disconnector cannot break load or short-circuit current.

Technical Data

Item	Unit	GN30-12/400	GN30-12/630	GN30-12/1000	GN30-12/1250
Rated voltage	kV	12	12	12	12
Rated frequency	Hz	50	50	50	50
Rated current	A	400	630	1000	1250
Thermal-stable current (4 s)	kA	12.5	20	31.5	31.5
Dynamic-stable (peak) current	kA	31.5	50	80	80

Selection note: Select the rated current grade first (400, 630, 1000 or 1250 A); the thermal-stable and dynamic-stable currents rise with the grade. Choose the plain GN30-12 or the GN30-12D with earthing switch according to the maintenance-earthing requirement, and confirm the mechanism position and interlock against the associated circuit breaker. Outline dimensions A, B and C vary with the current grade and the earthing-switch arrangement.

Standards

The GN30-12 design meets GB 1985 for AC high-voltage disconnectors and earthing switches. The GN30-12D version with earthing switch shares the same electrical ratings as the corresponding GN30-12 current grade.

Technical note: Rated electrical data are taken from the catalogue type tables; where a value is fixed by the order, the technical agreement and the nameplate of the delivered switch govern, and the certified dimensional drawing for the ordered current and earthing-switch arrangement governs the installation.

Installation & Dimensions

Installation Diagram

GN30-12 Indoor Rotating Contact Knife High-Voltage Disconnector - installation

Bolt the shared three-phase base frame to the cubicle mounting plane through the four 25 x 13 mm (R6.5) mounting holes at the specified phase spacing, keeping the installation plane clear. Couple the poles to the manual operating mechanism and, on the D version, to the earthing switch, then verify free travel of the rotating knives, correct contact seating and the full visible break before energising, and bond the frame to the earth network.

Type	Rated current	A (mm)	B (mm)	C (mm)
GN30-12	400 / 630 A	≈ 560	—	≈ 315
GN30-12	1000 A	≈ 580	—	≈ 332
GN30-12	1250 A	≈ 580	—	≈ 295
GN30-12D	400 / 630 A	≈ 550	≈ 610	≈ 240
GN30-12D	1000 A	≈ 575	≈ 615	≈ 245
GN30-12D	1250 A	≈ 580	≈ 600	≈ 295

Safety notice: The disconnector has no load or short-circuit breaking capability: the associated circuit breaker must be opened first, the interlock must remain in service and never be bypassed, and the earthing switch may be closed only after the circuit has been isolated and proved de-energised. Installation and maintenance must be performed by qualified personnel with the frame bonded to the earth network.

FAQs

G is the disconnector, N the indoor place of use and 30 the design sequence number; 12 is the rated voltage in kV and D denotes the version with an earthing switch. The trailing figures give the rated current in A and the 4 s thermal-stable current in kA.

Each pole has two insulator-and-contact sets on the upper and lower planes of a shared frame, and the moving knife rotates between them to open or close the circuit with a clear visible break.

Four grades: 400 A with 12.5 kA thermal-stable and 31.5 kA dynamic-stable current, 630 A with 20 kA and 50 kA, and both 1000 A and 1250 A with 31.5 kA and 80 kA.

No. It connects, interrupts or transfers circuits under voltage but without load and provides a visible isolating gap; load and fault currents are handled by the associated circuit breaker.

The 1 min power-frequency withstand voltage is 42 kV phase-to-phase and phase-to-earth and 48 kV across the break; the lightning impulse withstand voltage (peak) is 75 kV and 85 kV across the break.

In 12 kV (10 kV class) three-phase 50 Hz indoor systems, used with a metal-enclosed switchgear cubicle or as a standalone isolator. The design meets GB 1985 for AC high-voltage disconnectors and earthing switches.

GN30-12 Indoor Rotating Contact Knife High-Voltage Disconnector