Overview
The JN22-40.5/31.5 is an indoor high voltage earthing switch (grounding switch) for 40.5kV, 50 Hz three-phase power systems. It is matched with KYN61-405 and other types of high voltage metal-enclosed switchgear, and provides the protective earth for high voltage equipment during inspection and maintenance.
Under voltage but without load it bonds the de-energised circuit to earth for maintenance safety, and can close onto a short-circuit current. It is rated 31.5 kA for 4 s short-time withstand current with 80 kA peak and short-circuit making current, and is supplied with phase-center distances of 280, 300, 350, 360 and 400 mm to suit different cubicles.
Model Designation
The type is designated JN 22 – 40.5 / 31.5 – □ and decoded as follows:
- JN — indoor earthing switch
- 22 — design number
- 40.5 — maximum voltage in kV
- 31.5 — 4 s thermal-stability (short-time withstand) current in kA
- □ — phase-center distance in mm
Construction and Operation
The JN22-40.5 carries its three earth knives on support insulators above a common frame, driven through a transmission shaft by the operating mechanism so that 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 cubicle door to prevent mal-operation. The compact three-pole assembly mounts inside 40.5 kV metal-enclosed switchgear, and where the phase-center distance is below 360 mm an insulation board is added between the phases; the frame is bonded to the earth network to complete the protective path.
Technical Parameters
Rated Parameters
| Item | Unit | Data |
|---|---|---|
| Rated voltage | kV | 40.5 |
| Rated frequency | Hz | 50 |
| Rated short-time withstand current | kA | 31.5 |
| Rated short-circuit duration | s | 4 |
| Rated peak withstand current | kA | 80 |
| Rated short-circuit making current | kA | 80 |
| Phase-center distance | mm | 280 / 300 / 350 / 360 / 400 |
| 1 min power-frequency withstand voltage (phase to earth and phase to phase) | kV | 95 |
| Lightning impulse withstand voltage (phase to earth and phase to phase) | kV | 185 |
Operating Conditions
- Altitude: not above 1000 m
- Ambient temperature: upper limit +40℃, lower limit −25℃
- Seismic: intensity not above 8 degrees
- Site: installed in locations free from fire, explosion hazard, severe dust, chemical corrosion and violent vibration
Installation & Wiring
Installation and Mounting
Fix the earthing-switch frame to the cubicle mounting plane through the mounting holes at the selected phase-center distance, keeping the earth knives and static contacts clear of obstructions. Couple the three poles to the 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.
Outline & Mounting Dimensions
| Model | E (mm) | G (mm) | L (mm) | D (mm) |
|---|---|---|---|---|
| JN22-40.5/31.5-280 | 280 | 290 | 1010 | 656 |
| JN22-40.5/31.5-300 | 300 | 340 | 1100 | 696 |
| JN22-40.5/31.5-350 | 350 | 340 | 1200 | 796 |
| JN22-40.5/31.5-360 | 360 | 320 | 1200 | 816 |
| JN22-40.5/31.5-400 | 400 | 340 | 1300 | 896 |
E is the phase-center distance. Where the phase-center distance is below 360 mm an insulation board is added between the phases.
Selection & FAQs
Ordering Information
- When ordering, state the full model, rated voltage, rated short-time withstand current and phase-center distance, together with any accessory requirement.
- Select the phase-center distance (280 / 300 / 350 / 360 / 400 mm) to match the cubicle busbar layout; below 360 mm an inter-phase insulation board is fitted.
- Any special requirement is to be settled between the user and the manufacturer.
Frequently Asked Questions
Q1: What does the type designation JN22-40.5/31.5 mean?
JN is the indoor earthing switch and 22 the design number; 40.5 is the maximum voltage in kV, 31.5 the 4 s short-time withstand current in kA, and the trailing figure the phase-center distance in mm.
Q2: What is the JN22-40.5 used for?
It is an indoor high voltage earthing switch for 40.5 kV, 50 Hz systems, matched with KYN61-405 and other high voltage metal-enclosed switchgear to provide protective earthing during equipment inspection and maintenance.
Q3: What are the rated values?
Rated voltage 40.5 kV at 50 Hz, rated short-time withstand current 31.5 kA for 4 s, rated peak withstand current 80 kA and rated short-circuit making current 80 kA.
Q4: What is the insulation level?
1 min power-frequency withstand voltage 95 kV and lightning impulse withstand voltage 185 kV, both phase to earth and phase to phase.
Q5: What phase-center distances are available?
Five types — 280, 300, 350, 360 and 400 mm, with overall length L of 1010, 1100, 1200, 1200 and 1300 mm respectively; below 360 mm an insulation board is added between the phases.
Q6: Where can I see related products?
See the high voltage earthing switches range for related models.