JN15-12 Indoor Earthing Switch 12kV 31.5kA | 80kA Short-Circuit Making | HV Switchgear Grounding

Product Overview

The JN15-12 is an indoor high-voltage earthing switch for three-phase 50 Hz systems rated 12 kV and below, with performance to GB 1985-89 and IEC 129. It is the protective earthing element of high-voltage switchgear cubicles of various types: once the feeder is isolated and proved dead, its three earth knives bond the circuit to earth for maintenance, and the mechanism can be interlocked with the switchgear or cubicle door against mal-operation. The compact three-pole assembly carries 31.5 kA for 4 s, makes 80 kA peak short-circuit current, and comes with 210, 230, 250 or 275 mm phase centres.

Product Display

JN15-12 Indoor High-Voltage Earthing Switch 31.5 kA - display

JN15-12 Indoor High-Voltage Earthing Switch 31.5 kA - poster_display

Model Designation

JN15-12 Indoor High-Voltage Earthing Switch 31.5 kA - model

Model format: J N 15 – 12 / □ – □

J – earthing switch
N – place of use: indoor
15 – design sequence number
12 – rated voltage, kV
□ – rated short-time withstand current, kA (e.g. 31.5)
□ – phase-center (between-pole) distance, mm
Example: JN15-12/31.5-210 is the 31.5 kA type with 210 mm phase centres

Service Conditions

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

Construction

The three earth knives are carried on support insulators above a common frame and are driven through a transmission shaft by a manual operating mechanism, so all three poles make or break the earth connection together with a fast, positive action. The contacts are dimensioned to close reliably onto a short-circuit current, and the compact three-pole assembly mounts inside or on high-voltage switchgear cubicles.

The operating mechanism can be interlocked with the associated switchgear or with the cubicle door to prevent mal-operation, so the knives cannot be closed while the circuit is live nor the circuit re-energised while it is earthed. The frame is bonded to the earth network to complete the protective path, and the simple structure makes installation, commissioning and adjustment straightforward.

Technical Data

No.	Item	Unit	Data
1	Rated voltage	kV	12
2	Rated frequency	Hz	50
3	Rated short-time withstand current	kA	31.5
4	Rated short-circuit duration	s	4
5	Rated peak withstand current	kA	80
6	Rated short-circuit making current	kA	80
7	Phase-center (between-pole) distance	mm	210 / 230 / 250 / 275
8	1 min power-frequency withstand voltage	kV	42 / 48
9	Lightning impulse withstand voltage	kV	per technical agreement
10	Standard	—	GB 1985-89; IEC 129

Selection note: Check that the network voltage does not exceed 12 kV and that the prospective short-circuit current at the installation point is within the 31.5 kA 4 s short-time and 80 kA peak ratings. Then select the phase-centre distance, 210, 230, 250 or 275 mm, to match the cubicle busbar layout, and state the full model, rated voltage, short-time withstand current and phase-centre distance when ordering, together with any accessory or interlock requirement; special requirements are settled between user and manufacturer.

Standards

Performance of the JN15-12 complies with GB 1985-89 for AC high-voltage disconnectors and earthing switches and with IEC 129. The lightning impulse withstand voltage is not fixed in the catalogue and is confirmed by the technical agreement for the ordered arrangement.

Technical note: Values are taken from the type datasheet; the lightning-impulse withstand level and any special service conditions are confirmed with the technical agreement and the nameplate of the delivered switch, and the certified dimensional drawing governs for the ordered phase-centre distance.

Installation & Dimensions

Installation Diagram

JN15-12 Indoor High-Voltage Earthing Switch 31.5 kA - installation

Fix the earthing-switch frame to the cubicle mounting plane through the C10 x 19 oval holes at the selected phase-centre distance, keeping the earth knives and contacts clear of obstructions. Couple the three poles to the manual operating mechanism through the transmission shaft, then verify simultaneous and full contact seating of all three poles, correct interlock action and bonding of the frame to the earth network before energising. Dimensions are taken from the catalogue outline drawing and are for cubicle preparation only; confirm the certified dimensional drawing for the ordered phase-centre distance before installation.

Model	L (mm)	E (mm)	C (mm)
JN15-12/31.5-210	655	210	516
JN15-12/31.5-230	710	230	556
JN15-12/31.5-250	760	250	596
JN15-12/31.5-275	810	275	646

Safety notice: The JN15-12 may only be closed onto a circuit that has been isolated and proved de-energised; it is interlocked with the associated disconnector or circuit breaker so that it cannot be closed onto a live circuit nor opened while the circuit remains earthed. It withstands and makes short-circuit current but breaks no load current, and installation and maintenance must be performed by qualified personnel with the frame bonded to the earth network.

FAQs

J marks an earthing switch and N the indoor place of use, 15 is the design sequence number and 12 the rated voltage in kV. The fields after the slash give the rated short-time withstand current in kA, typically 31.5, and the phase-centre distance in mm.

It is the protective earthing element used with high-voltage switchgear cubicles of various types in 12 kV and below, 50 Hz systems. Once the circuit is isolated and proved dead it bonds the de-energised circuit to earth, protecting personnel during inspection and maintenance.

Rated voltage 12 kV at 50 Hz, rated short-time withstand current 31.5 kA for 4 s, and both rated peak withstand and short-circuit making current of 80 kA. The 1 min power-frequency withstand voltage is 42/48 kV; the lightning impulse level follows the technical agreement.

Both belong to the same JN15 design family and share the 31.5 kA 4 s and 80 kA ratings, but the JN15-12 serves 12 kV systems with 42/48 kV power-frequency insulation and fixed phase-centre distances of 210-275 mm, while the JN15-24/31.5 is the 24 kV version with 65/125 kV insulation and phase spacing stated at ordering.

Four variants: JN15-12/31.5-210, -230, -250 and -275, giving overall lengths L of 655, 710, 760 and 810 mm respectively. Select the distance that matches the busbar layout of the cubicle.

Yes. The contacts are dimensioned to close reliably onto a short-circuit current up to the 80 kA rated making current, and the frame is bonded to the earth network to complete the protective path. It carries fault current but breaks no load current.

JN15-12 Indoor High-Voltage Earthing Switch 12kV 31.5kA | 80kA