This article will delve into the working principle of the ZW7-40.5 series outdoor high-voltage vacuum circuit breaker, revealing how it stably performs its power mission of opening and closing in the face of wind, frost, rain, and snow.
How high voltage circuit breaker works? The working principle can be divided into the following three key processes:
This is the essence of vacuum circuit breaker technology. When the moving and stationary contacts separate within the arc-extinguishing chamber:
Metal Vapor Arc Formation: At the instant of separation, the strong electric field and high temperature cause the metal on the contact surface to evaporate, forming high-density metal vapor, which ignites a plasma arc in the vacuum.
Current Zero-Crossing Extinguishing: Benefiting from the natural zero-crossing point of the alternating current. At the instant the current crosses zero, the arc is temporarily extinguished due to the interruption of the energy supply.
Rapid Recovery of Dielectric Strength: Simultaneously, the incandescent metal vapor particles diffuse and condense at extremely high speed towards the surrounding shielding. The vacuum level within the arc-extinguishing chamber recovers rapidly within microseconds, and the dielectric insulation strength rises sharply, far exceeding the rate of increase in the recovery voltage between the contacts, thus completely preventing arc reignition and completing the breaking process.
Energy Storage: The operating mechanism pre-compresses the closing spring (or excites the electromagnet), storing mechanical energy.
Release Execution: Upon receiving the closing command, the tripping device releases the stored energy. The spring quickly relaxes (or the electromagnet actuates), and through a four-bar linkage, the rotational motion is converted into a vertical upward linear motion of the moving contact, allowing it to contact the stationary contact at high speed and smoothly, completing the circuit connection.
Opening Process:
Interlocking Energy Storage: During the closing process, the opening spring is usually compressed, and energy is stored simultaneously.
Triggering Tripping: When the protection relay sends a trip signal or manual tripping occurs, the tripping device actuates.
Rapid Separation: The tripping device releases its latch, the energy of the opening spring is rapidly released, driving the moving contact to move downward at extremely high speed, separating from the stationary contact, and immediately initiating the aforementioned vacuum arc extinguishing process.
The overall design philosophy of the ZW7-40.5 is to proactively withstand environmental challenges:
Fully Sealed Design: The arc-extinguishing chamber is sealed, and the mechanism enclosure has a high protection rating (typically IP54 or higher), effectively isolating moisture, dust, and salt spray, ensuring that internal components remain unaffected even in environments with an average daily humidity of 95%.
Wide Temperature Range Materials: All materials (seals, grease, metals) are selected based on models capable of operating normally in extreme temperatures ranging from -40℃ to +40℃, avoiding low-temperature embrittlement or high-temperature aging.
Mechanical Stability: The ceramic column structure possesses extremely high bending and seismic strength, capable of withstanding 34m/s winds (700Pa wind pressure) and earthquakes of intensity 8, ensuring the precision of mechanical operation.
The working principle of a circuit breaker revolves around two core actions:
Closing (closing): Connecting the circuit to allow current to flow normally.
Breaking (opening): Rapidly separating the contacts and interrupting the current upon triggering a command or protection signal. Especially when breaking short-circuit currents of thousands of amperes, it is essential to reliably and quickly extinguish the strong power generated between the contacts.
The ZW7-40.5, as an outdoor vacuum circuit breaker, achieves its core technological breakthrough by utilizing “vacuum” as the arc-extinguishing and insulating medium, perfectly solving the breaking challenges in outdoor environments.
Core Component Analysis
The ZW7-40.5 outdoor high-voltage vacuum circuit breaker uses a fully sealed vacuum interrupter as its core breaking component, achieving instantaneous and reliable current interruption through a high vacuum environment. Simultaneously, it employs a high-strength ceramic column structure to provide robust insulation support and, in conjunction with an intelligent operating mechanism, enables flexible electric and manual control, forming a complete and reliable three-phase protection system.
How often should a high-voltage circuit breaker be maintained?
Thanks to the sealing and long lifespan of the vacuum interrupter, the ZW7-40.5 is a low-maintenance device. Every 1-3 years, check the lubrication and tightness of the mechanical components; test the reliability of the secondary control circuit and auxiliary switches; clean the porcelain insulator surface; and measure the main circuit resistance and mechanical characteristics (such as opening and closing time and speed).
Can it still be used if the installation site’s altitude exceeds 2000 meters?
Yes, but special attention is required. Because at higher altitudes, the air is thinner, and the insulation strength will decrease. In this case, the altitude should be clearly specified when ordering, and the manufacturer will accordingly improve the equipment’s insulation class (e.g., using longer creepage distances and larger air gaps) to ensure safe operation at high altitudes.
What does “ZW7-40.5” in the high voltage circuit breaker model name mean?
This is the naming convention for high-voltage circuit breakers in China:
Z: Represents “vacuum” interrupter medium.
W: Represents “outdoor” use.
7: Design series serial number.
40.5: Rated voltage, in kilovolts (kV), corresponding to a system voltage of 35kV (40.5kV is the maximum operating voltage of the equipment).
What environmental conditions can the ZW7-40.5 circuit breaker be used?
The ZW7-40.5 is designed for harsh outdoor environments, suitable for the following conditions:
Temperature range: -40℃ to +40℃.
Altitude: ≤ 2000 meters (special design required for altitudes exceeding this).
Ambient humidity: Daily average ≤95%, monthly average ≤90%.
Pollution resistance: Suitable for industrial, coastal, and other dusty/salt-spray areas with pollution level IV.
Mechanical strength: Can withstand wind speeds of 34 m/s (approximately a Category 12 typhoon) and earthquakes of intensity 8.
Caution: Installation sites should avoid flammable, explosive, chemically corrosive, and violently vibrating environments.
The ZW7-40.5 High voltage circuit breaker works by utilizing the characteristic of rapid diffusion and condensation of metal vapor in an electric arc when the current crosses zero in a high vacuum environment. This allows the arc to be irreversibly extinguished within tens of milliseconds, thus reliably interrupting the fault current.
If you are looking for a reliable protection solution for your 35kV outdoor power system, the ZW7-40.5 vacuum circuit breaker is the ideal choice. Inquire now for detailed technical information and a customized quote. Let us safeguard the safety of your power grid.
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