Procurement of 10kV Load Switches: Three Major Assessment Zones and Hardcore Testing Standards for Used Equipment

2025-08-28 15:56:27

>Purchasing second-hand Load switches is like buying a retired police car. It may not have a high mileage and an attractive price, but you must figure out: what kind of violent driving has it experienced? Which key components have reached their lifespan limit? Will hidden faults cause it to completely collapse on the next high-speed drive?

Choosing second-hand equipment is not simply a matter of "trying to power it on", but rather a systematic risk assessment based on professional knowledge. Here are the three deadliest minefields and their corresponding on-site detection methods.

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Minefield 1: Unknown History - The Deadly Blind Spot of Equipment's' Life '

Core risk: The device you have purchased may be a "critically ill" device that has been excessively overdrawn from a frequently faulty line.   

Evaluation criteria and testing methods:

1. Traceability and consultation (mandatory):

-Request for files: The seller is required to provide the factory test report (original version), installation and operation date, and last maintenance record. Without archival equipment, the risk level is directly adjusted to the highest.   

-Inquire about key information:

-Operation frequency: Is it used for frequently operated line segmentation points, or for isolation points that remain stationary all year round? The former consumes a significant amount of mechanical life.   

-Fault history: Have you ever disconnected short-circuit current? What are the number of disconnections? This directly determines the lifespan of the arc extinguishing chamber and contacts.   

2. Nameplate decoding (on-site verification):

-Model interpretation: Confirm the model (such as FKN12-12D). 'F' represents load switch, 'K' is vacuum type, and '12' is 12kV.

-Key parameters: Verify the rated current (630A? 1250A?), rated short-time withstand current (thermal stability) (16kA/3s? 20kA/4s?), and rated short-circuit closing current (dynamic stability). Ensure that it matches the system short-circuit capacity of your site. Mismatch is the biggest security risk.   

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Minefield 2: Aging of Insulation and Arc Extinguishing Systems - Invisible Performance Degradation

Core risk: Decreased insulation performance may lead to relative ground or phase to phase breakdown during operation; The decline in arc extinguishing ability may lead to reignition or explosion during disconnection.   

Hardcore testing standards (requiring professional testing equipment):

1. Main circuit insulation resistance test:

-Standard: Use a 2500V or 5000V megohmmeter for measurement. Qualified line: ≥ 1000 M Ω. If it is lower than this value, it indicates that the insulation is damp or deteriorated, and the next step of the test must be carried out.   

2. Power frequency withstand voltage test (key item of handover test):

-Standard: Apply a power frequency voltage of 42kV between the fracture surfaces (dynamic and static contacts) and relative ground, and maintain it for 1 minute.   

-Result judgment: No breakdown, no flashover, and stable leakage current are considered qualified. This is a veto item for verifying the strength of the main insulation.   

3. Vacuum degree detection of vacuum arc extinguishing chamber (core item of Vacuum switch):

-Method: Use a magnetron discharge method vacuum degree tester. This is the only reliable quantitative detection method.

-Standard: The vacuum degree value must be ≤ 10 ? 2 Pa (or according to the manufacturer's standard, but usually better than this value). Any qualitative 'pressure resistance method' is unprofessional and requires quantitative data.

4. SF6 gas leak detection (such as SF6 load switch):

-Method: Use SF6 gas leak detector to scan the sealing surface and interface in all directions.   

-Standard: Zero leakage is a basic requirement. Any leakage point means that the equipment has failed and must be overhauled.   

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Minefield Three: Mechanical Characteristics and Mechanism Wear - The Foundation of Action Reliability

Core risks: Institutional jamming, inadequate opening and closing, spring fatigue, resulting in load misoperation or failure to move, leading to accidents.   

Hardcore testing standards:

1. Mechanical characteristic testing (requires specialized testing equipment):

-Opening/closing time: It should comply with the manufacturer's standard (usually several tens of milliseconds), and the three-phase synchronicity (time difference) should be ≤ 2ms. Different periods may cause excessive arc time.   

-Opening/closing speed: The average speed and initial opening/closing speed are key parameters. Low speed can cause arc extinguishing failure.   

-Circuit resistance test: Use a micro ohmmeter (100A or above) to measure the resistance of the main circuit. The three-phase values should be balanced and comply with the factory values (usually<50 μ Ω). Excessive resistance indicates contact erosion or aging of the compressed spring.   

2. Manual operation and visual inspection:

-Operating force sensation: Manual energy storage and opening/closing operations should be smooth, without any jamming or abnormal noise.   

-Appearance inspection: Check whether the insulation rod has cracks or cracks; Are there severe wear and tear on metal components such as gears and shaft pins; Are the fasteners loose.   

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The ultimate advice for the purchaser

1. Price reconstruction: The total cost of second-hand equipment=purchase price+comprehensive testing fee+possible major repair fee+spare parts fee+risk cost. Only when the total is much lower than the new device, is it worth considering.   

2. Agreement binding: It must be clearly stated in the procurement agreement that final payment is subject to professional testing and qualification. Transfer commercial risks to the seller.   

3. Seek professional support: Hire a third-party power testing team for testing, which usually costs only 5% -10% of the equipment price, but can avoid 100% of major risks.   

Conclusion:

Second hand load switches cannot be purchased, but can only be purchased by professionals for informed systems. For teams that are unable to perform the above verification, choosing a brand new, legitimate product with warranty is the lowest cost and least risk option.