A professional selection guide for JN15 series grounding switches

2025-08-12 13:25:27

This article is a professional selection guide for JN15 series Grounding switches, combining core parameter analysis, 3D selection matrix, and engineering cases to help accurately match application scenarios.   

1、 Key parameter analysis: the technical cornerstone of selection

1. Rated short-time withstand current (31.5kA/s)

-Definition: The ability of a switch to withstand a short-circuit current of 31.5kA within 4 seconds without damage, directly reflecting the thermal stability of the equipment.   

-Selection significance:

If the usage scenario is in industrial heavy-duty scenarios such as steel mills, ports, etc., the rated short-time withstand current needs to be ≥ 31.5kA, and new energy stations can choose the 31.5kA basic version. If the system expects a short-circuit current exceeding 40kA, it needs to be upgraded to JN15-12/40 type (withstand current of 40kA).   

2. Rated short-circuit closing current (80kA)

-Definition: The maximum peak current that a switch can withstand at the moment of closure, testing its dynamic stability and arc extinguishing ability.   

-Selection significance:

In scenarios with high short-circuit current, 80KA must be met to avoid contact fusion welding. Equipped with a fast spring mechanism to ensure a closing speed greater than 2m/s and reduce arc damage.   

3. Power frequency withstand voltage (42kV) and impulse withstand voltage (75kV)

-Definition: Evaluate the insulation strength of equipment under power frequency overvoltage and lightning overvoltage respectively.   

-Selection significance:

In areas with pollution level III or above (such as coastal and chemical areas), additional verification of creepage distance ≥ 20mm/kV is required.   

The altitude of this product shall not exceed 1000m, and the test voltage shall be adjusted according to GB/T 11022 for high altitudes (>1000m).   

  2、 Three dimensional selection matrix: matching logic of voltage, load, and environment

>  Key points for matching KYN28A-12 switchgear:

>- Phase spacing matching: 650mm wide cabinet → 150mm grounding switch, 800mm cabinet → 210mm, 1000mm cabinet → 275mm.

>- Lockout requirement: The outgoing cabinet must be equipped with grounding interlock and guide rail interlock to prevent live grounding knives.   

  3、 Core component material selection: the key to lifespan and reliability

1. The function of copper aluminum transition joint (contact resistance<200 μ Ω) is to connect the grounding busbar and the switch contact blade to avoid electrochemical corrosion.   

-Selection principle:

-Copper aluminum composite transition plates must be selected for aluminum busbar systems to reduce contact surface oxidation.   

-Torque tightening (recommended 35N · m)+conductive paste coating to ensure temperature rise<65K.

2. Silicone rubber seals (with a lifespan of ≥ 10 years)

-Function: Protect the flange gap of the pillar insulator, block moisture and corrosive gases.   

-Selection principle:

-Choose acid resistant silicone rubber (resistant to H ? S and SO ?) for the chemical industry zone.   

-Sulfur modified materials are used in high and low temperature scenarios (-40 ℃~+120 ℃) to prevent hardening and cracking.   

4、 Practical case: Anti corrosion selection for chemical industrial parks

project background

In the 10kV distribution room of a coastal chemical industrial park, the original JN15-12 grounding switch experienced corrosion caused by chloride ions, resulting in rusting and sticking of the moving contact blade, creeping marks on the surface of the epoxy insulator, and condensation intrusion caused by the hardening of the sealing ring in just 2 years

Minrong Upgrade Plan

1. Substrate protection: The moving contact knife is coated with 316L stainless steel coating (thickness 50 μ m), which is resistant to salt spray for more than 1000 hours.

2. Sealing upgrade: Use fluorosilicone rubber sealing rings to withstand pH 2-12 chemical media.   

3. Insulation strengthening: RTV anti fouling flashover coating is added to the pillar insulators, increasing the creepage distance by 30%.   

Effect: Extended from 2 years to 8 years (with 4 years of continuous operation without faults) and reduced annual maintenance costs by 72%.   

5、 Selection Summary: Precise Matching of Three Elements

1. Rigid parameter matching: The short-circuit current and insulation level must not be lower than the maximum value of the system.   

2. Space compatibility: The phase spacing and installation dimensions (such as L × E × C) strictly correspond to the switchgear.   

3. Environmental adaptation:

-Hot and humid areas → choose TH suffix (such as JN15-12/31.5-210TH);   

-Corrosion zone → strengthened coating+sealing;   

-Intelligent scenario → equipped with electric operation module (supporting remote opening and closing).   

>Selection avoidance reminder: When placing an order, it is necessary to clearly label "voltage/short-time current- phase spacing" (such as JN15-12/31.5-210TH) to avoid parameter omissions and mismatches.