JN17-12/40 Combined Indoor High-Voltage Earthing Switch for 3-10 kV

Product Overview

The JN17-12/40 is a combined indoor high-voltage earthing switch for 3-10 kV, 50/60 Hz systems, rated 12 kV, that bonds de-energised switchgear circuits to earth for maintenance. Three earth knives on support insulators over a common frame couple through one shaft, interlocked with the disconnector, breaker or cubicle door. It carries a 40 kA short-time withstand current, and its short-circuit making capacity protects other cubicle equipment; the combined type can include a live-voltage indicating device. Five frames cover phase-centre distances of 210-275 mm; G marks the high-altitude type.

Product Display

Model Designation

Model format: J N 17 – 12 (G) / 40 – □

• J – earthing switch
• N – place of use: indoor
• 17 – design number (also built as the JN15-12G/40 variant)
• 12 – rated voltage, kV
• (G) – high-altitude type, optional suffix
• 40 – rated short-time withstand current, kA
• □ – phase-centre (between-pole) distance, mm: 210 / 220 / 230 / 250 / 275
• Example: JN17-12G/40-230 is the high-altitude type at 40 kA with 230 mm pole spacing

Service Conditions

• Altitude: not above 1000 m
• Ambient air temperature: upper limit +40 °C, lower limit -10 °C
• Seismic intensity: not above 8 degrees
• Site free from flammable or explosive hazard, severe dust, chemical corrosion and violent vibration

Construction

The switch uses a combined three-pole arrangement in which the earth knives are mounted on support insulators above a common frame and coupled through a transmission shaft to the operating mechanism, so all three poles make or break the earth connection together. The knives engage static contacts sized to close reliably onto a short-circuit current, and the mechanism can be interlocked with the associated switchgear or with the cubicle door to prevent mal-operation.

As a combined type the assembly can be furnished with a live-voltage indicating device that shows the energised state of the busbar. A flexible earth conductor, standard length 240 mm unless otherwise agreed, links the switch to the earthing network, and the frame itself is bonded to that network to complete the protective path; five phase-centre distances allow the frame to match cubicles of different makers.

Technical Data

Standards

The source datasheet names no specific product standard for the JN17-12/40; the ratings follow the order technical agreement and the nameplate of the delivered switch. Only the rated voltage, the 50/60 Hz frequency, the 40 kA rated short-time withstand current and the five phase-centre distances are published, while short-circuit duration, rated peak withstand current, rated short-circuit making current and the rated insulation level are fixed by agreement.

Installation & Dimensions

Installation Diagram

Fix the earthing-switch frame to the cubicle mounting plane at the selected phase-centre distance, keeping the earth knives and static contacts clear of obstructions. Couple the three poles to the operating mechanism through the transmission shaft and connect the flexible earth conductor, standard length 240 mm unless otherwise agreed. Before energising, verify simultaneous and full contact seating of all three poles, correct interlock action with the associated switchgear or cubicle door, and reliable bonding of the frame to the earth network.

FAQs