What are the functions of outdoor high-voltage vacuum circuit breakers? What are the installation requirements?

Outdoor high-voltage vacuum circuit breakers are critical protection and control devices in power systems, particularly in 10kV-35kV distribution networks. They integrate numerous important functions, far exceeding the simple act of a switch.

The following are their main functions, categorized as core and additional:

I. Core Functions

1.Control Function

Normal Switching: Safely connects and disconnects high-voltage circuits as needed during normal power system operation. For example, operators can remotely or locally operate the circuit breaker to open or close the circuit breaker for line maintenance, switching operating modes, or adjusting the grid structure.

Automatic Reclosing: This is a key function of modern circuit breakers. Most line faults (such as lightning strikes or branches hitting wires) are instantaneous. After the circuit breaker trips, it automatically recloses after a very short delay (e.g., 0.3-0.5 seconds). If the fault has resolved, power is restored, significantly improving power supply reliability.

2.Protection Function (Most Important and Core Function)
Circuit breakers, in conjunction with relay protection devices, can automatically detect faults and quickly operate to disconnect the faulty circuit, protecting the entire power grid and equipment. Key protection types include:

Overcurrent Protection (Short-Circuit Protection): When a short-circuit fault occurs in a line, generating a significant current, the circuit breaker trips immediately (or after a set delay), shutting off the current.

Instantaneous trip protection: This type of overcurrent protection triggers an instantaneous trip without delay to protect equipment when the short-circuit current is abnormally high.

Overload protection: When the line current exceeds the safe operating value but does not reach a short-circuit level, the circuit breaker trips after a delay to prevent damage from prolonged overheating.

Zero-sequence protection (ground fault protection): Detects whether a single-phase ground fault has occurred in the line. If so, the protection device issues a signal or trips the circuit breaker.

II. Additional and Supporting Functions

To achieve the core functions described above and adapt to harsh outdoor environments, modern outdoor high-voltage vacuum circuit breakers also possess the following features and functions:

1.Arc Extinguishment

This is the origin of the name "vacuum circuit breaker." Its core component is the vacuum interrupter. When a circuit is disconnected (especially a high-current circuit), a high-temperature arc is generated between the contacts. The vacuum interrupter utilizes the high dielectric strength and extremely strong arc-extinguishing capability of the high vacuum environment to quickly and silently extinguish the arc, ensuring safe and reliable circuit disconnection.

2.Measurement and Monitoring Functions

Integrated or external current transformers (CTs) measure line current in real time and provide signals to protective devices and metering instruments.

Intelligent circuit breakers (such as the ZW32) also feature an intelligent control unit that collects data such as voltage, current, and power, and enables communication.

3.Communication and Remote Control

This is key to smart grids (distribution automation). Circuit breakers are typically equipped with electric operating mechanisms and communication modules (such as 4G/5G, wireless public networks, and fiber optics).

This enables the "three remote" functions:

Telemetry: Remotely measures current, voltage, and other data.

Telesignaling: Remotely reports circuit breaker status (closed/open), energy storage status, and fault information.

Remote Control: The dispatch center can remotely control the opening and closing of circuit breakers, achieving fault isolation and automated power restoration to non-faulty areas without the need for on-site personnel.

4.Suitable for Outdoor Environments

Fully Sealed, Fully Insulated Construction: The enclosure is typically constructed of stainless steel or high-quality steel plates with an anti-corrosion treatment. It offers excellent sealing performance, effectively protecting against moisture, condensation, salt spray, and corrosion, and is resistant to wind, sunlight, and harsh climates.

Visible Isolation: Many models (such as the ZW32) are equipped with an isolation switch. When the circuit breaker is tripped, the isolation switch creates a visible, safe electrical isolation gap, providing a double layer of safety for maintenance personnel.

In short, the outdoor high-voltage vacuum circuit breaker is a highly intelligent device that integrates control, protection, arc extinguishing, measurement, and communication. It serves not only as a "switch" for the power grid but also as its "automatic bodyguard," playing an irreplaceable role in ensuring power supply reliability, improving the level of grid automation, and ensuring equipment and personal safety.

Ⅲ.Installation Requirements

Outdoor high-voltage vacuum circuit breakers are generally used outdoors, so the installation requirements are higher during installation. So what should be paid attention to when installing outdoor high-voltage vacuum circuit breakers?

1. Check the distance between the poles. The distance between the upper and lower leads must comply with relevant professional technical regulations.
2. All rotating and sliding parts must move freely, and any friction points must be lubricated.
3. Before installation, perform an external and internal inspection of the vacuum circuit breaker. The vacuum interrupter, components, and assemblies must be complete, qualified, undamaged, and free of foreign matter.
4. After the overall installation and commissioning are completed, clean and wipe the unit clean. Mark all adjustable connections with red paint, and apply anti-corrosion grease to the lead terminals.
5. Strictly adhere to the installation process regulations. The specifications of the fasteners used for each component must comply with the design specifications.
6. Tools used must be clean and meet assembly requirements. Do not use adjustable wrenches when tightening screws around the interrupter.

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