The core of checking for air leakage (vacuum degradation) in a vacuum circuit breaker is a four-step process: "Initial visual inspection → Electrical withstand voltage test → Vacuum degree instrument test → Auxiliary verification." Prioritize safe and quick visual inspection and power frequency withstand voltage test, then use professional instruments for quantitative confirmation.
Initial Judgment During Operation (Without Power Outage/Simple Observation)
1. Listen to the Sound
Normal: Only a crisp metallic clanging sound when opening and closing.
Air Leakage: Hissing airflow sound, muffled discharge sound, high-frequency whistling sound, especially noticeable when opening.
2. Observe the Arc and Appearance (Glass-Shelled Arc Extinguisher)
When breaking, the arc appears white, elongated, and glaring (normal is pale blue/purple, short and concentrated).
The inner glass wall appears white, fogged, condensed, the metal plating discolored/peeled, and the getter (mirror surface) appears white/disappears (normal is a bright mirror surface).
3. Infrared Thermometry (Auxiliary): Localized overheating in the middle of the arc-extinguishing chamber (temperature rise > 40K) may be caused by internal discharge.
Power Outage Safety Measures (Required Before All Offline Inspections)
Disconnect the upstream and downstream isolating switches of the circuit breaker and verify that there is no voltage on all three phases.
Close the grounding switch, ensure reliable grounding, and release the energy storage spring.
Hang a "Do Not Close" sign and ensure proper insulation protection (insulating gloves and shoes).
Offline Inspection Methods (Ranked by Priority)
1. Visual Sealing Inspection (Most Basic):
Ceramic/Glass Shell of Arc-Extinguishing Chamber: No cracks, damage, or discharge marks.
Sealing Welds, Bellows, and Flanges: No oil stains, dust accumulation, cracks, or deformation (air leaks will attract dust).
Moving Contact Rod: Should automatically spring back after being manually pulled (if external atmospheric pressure is normal, weak/no springback will occur if vacuum fails).
2. Power Frequency Withstand Voltage Test (Most commonly used, used to determine severe gas leakage)
Wiring: With the circuit breaker open, apply a high power frequency voltage (e.g., 42kV/1min for a 10kV circuit breaker) between the contacts.
Criteria:
Pass: No breakdown, no flashover, stable current.
Leakage: Instantaneous breakdown, continuous flashover, and a surge in current indicate that the vacuum level is below 10⁻³Pa, requiring replacement.
Caution: After the test, slowly reduce the voltage to zero to ensure complete discharge and avoid residual voltage causing injury.
3. Vacuum Degree Tester (Magnetic Controlled Discharge Method, Quantitative Detection)
Principle: Magnetic field + electric field excites residual gas to ionize; the vacuum level is calculated by measuring the ion current.
Standard: Normal ≥1×10⁻⁴Pa; ×10⁻³Pa requires replacement.
Advantages: Does not damage the arc-extinguishing chamber, accurate quantitative measurement, can be tested both live and offline, making it the preferred choice for precise on-site testing.
4. Spark Test Method (For Glass Shells, Simple Qualitative Analysis)
Move a high-frequency spark tester along the glass surface:
Normal: No spark / faint blue dot.
Leakage: Bright spark, travels along the inner wall; the lower the vacuum, the stronger the spark.
5. Contact Resistance / Insulation Resistance (Supplementary Reference)
Contact Resistance: Abnormally increased (compare with historical values), possibly due to vacuum deterioration or contact oxidation.
Insulation Resistance: Main circuit to ground below 1000MΩ (2500V megohmmeter); further confirmation with withstand voltage testing is required.
Common Misconceptions and Precautions
Relying solely on appearance: Ceramic shell arc-extinguishing chambers cannot be judged by appearance alone; withstand voltage or instrument testing is necessary.
Risk of Withstand Voltage Test: Severe vacuum deterioration may cause breakdown and damage to the contacts; it is recommended to perform instrument testing first, then withstand voltage testing.
Judgment and Handling Procedure
Abnormal noise/arc during operation → Power off and visual inspection → Power frequency withstand voltage test → Vacuum degree tester confirmation.
Vacuum degree **≥1×10⁻⁴Pa**: Normal, periodic re-inspection.
1×10⁻⁴Pa ~ 1×10⁻³Pa: Warning, shorten the testing cycle.
＜1×10⁻³Pa: Leakage failure, replace the arc-extinguishing chamber immediately.
ZW7-40.5 Outdoor Vacuum Circuit Breaker
ZW7-40.5 outdoor vacuum circuit breaker is a three-phase AC 50Hz outdoor equipment with 40.5kV rated voltage. This product can be used for making and breaking load current, overload current, and short-circuit current. The product features a rational structure and easy maintenance, with the option to equip current transformers, enabling multiple configurations and windings to meet various metering, measuring, and protection needs.
Technical parameters:
1. Rated Voltage: 40.5kV
2. Operating Mechanism: Modular operating mechanism.
3. Installation Method: Fixed installation with outdoor support.
4. Product Compliance with Standards: GB/T1984-2014, GB/T11022-2011.
5. Product Advantages: E2-C2-M2 performance, convenient maintenance, standardized outdoor design, wide range of applications.
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contact us
Shaanxi West Power Tongzhong Electrical Co., Ltd.
Contact: Ms.Grace Liu (International Sales Manager)
Mobile: +86 18091765882(WhatsApp/Wechat/facebook/telegram)
Email:xdtz04@westpowerelectri.com
Website:https://www.xdtzelectrical.com
