Arrangement of Arc-Extinguishing Chambers (Integral Structure)
This type of description is sometimes referred to as "horizontal" or "vertical," mainly referring to the arrangement direction of the three-phase arc-exting chambers within the enclosure.
1. Horizontal (Horizontal) Arrangement
Structural Features: Three vacuum arc-exting chambers are arranged horizontally and parallel within a sealed enclosure. This is the most classic and common structure in the ZW7 series.
Advantages: Stable structure, low center of gravity, good wind load and seismic resistance; easy to ensure phase-to-phase insulation distance; mature manufacturing process.
Appearance: The circuit breaker is generally a horizontally oriented cylindrical or elliptical cylindrical enclosure.
2. Vertical (or "Center-Mounted," but note the difference) Arrangement
Structural Features: Three vacuum arc-exting chambers are arranged vertically or at an angle. This structure is relatively less common in 40.5kV voltage levels and more prevalent in higher voltage levels.
Note: Strictly speaking, the typical "center-mounted" concept of the ZW7, as an outdoor pole-mounted circuit breaker, is more often used in indoor switchgear (such as KYN28). In outdoor products, the term "center-mounted" typically refers to the operating mechanism being located in the middle below the arc-extinguishing chamber, forming a compact, vertical layout, rather than the traditional horizontal, elongated tank.
By Current Transformer Integration Method
This is a key configuration option affecting circuit breaker function, installation, and maintenance.
Built-in CT Type
Built-in: This means the current transformer is integrated inside the circuit breaker body, becoming an integrated component rather than a separate external device.
Specific Structure: Typically, the toroidal core (the sensing part of the CT) is directly mounted on the insulating shell of the circuit breaker's arc-extinguishing chamber (vacuum chamber), or placed below the circuit breaker bushing. The primary conductor (high-voltage conductor) passes through the center of the toroidal core, naturally becoming the primary side of the CT. The secondary coil leads are connected to a dedicated junction box.
Key Advantages
The "built-in CT" design represents a significant technological advancement in high-voltage switchgear such as the ZW7-40.5, offering numerous advantages:
1. Compact Structure, Space Saving: Integrating the CT within the circuit breaker body eliminates the need for a separate CT mounting bracket and saves considerable space, significantly reducing the overall footprint of the switchgear. This is particularly suitable for space-constrained compact substations and prefabricated substations (panel-type substations).
2. High Reliability, Maintenance-Free: The built-in CT resides within a sealed gas chamber filled with SF6 gas (serving as insulation and arc extinguishing medium). SF6 gas provides excellent insulation and a moisture-proof, dust-proof, and corrosion-resistant environment, ensuring the CT remains unaffected by external weather conditions (such as rain, snow, condensation, dirt, and salt spray). This results in excellent stability and essentially maintenance-free operation throughout its entire lifespan.
3. Superior Insulation Performance: The CT's insulation is provided by the SF6 gas within the circuit breaker body and high-quality epoxy resin and other solid insulation materials. This results in high and stable insulation strength, eliminating the insulation aging and moisture-related problems that can occur with traditional dry-type or oil-immersed CTs, thus enhancing safety.
4. Excellent Electrical Performance: Due to the fixed structure of the primary conductor (high-voltage side), its relative position to the CT is precise and constant, resulting in better electromagnetic interference resistance, smaller angle and ratio differences, and higher measurement accuracy and protection action precision.
The excellent arc-extinguishing and insulation properties of SF6 gas also enable the built-in CT to withstand the steep wave impact generated when the circuit breaker interrupts short-circuit current.
5. Simple Installation and Short Construction Period: Users only need to install the circuit breaker body and connect the primary cable; there is no need to separately install, adjust, and fix an independent CT. This greatly reduces on-site installation workload, connection points, and commissioning time, improving construction efficiency and reducing installation costs.
6. Fully Sealed and Strong Environmental Adaptability: The overall sealed design allows it to adapt to harsh environments such as high temperature, low temperature, high altitude, high humidity, coastal salt spray, and industrial pollution, expanding the equipment's application range.
External CT type
"External" means that the current transformer (CT) exists as an electrical device completely independent of the circuit breaker.
It is installed outside the circuit breaker (or other primary equipment, such as disconnecting switches, transformer bushings), and connected in series with the primary circuit through conductors, busbars, or cables.
It has its own independent housing (such as epoxy resin casting, porcelain insulators, or SF6 gas insulation), mounting bracket, terminal box, and nameplate. Advantages:
1. Flexible configuration, easy selection and replacement:
Independent selection: The most suitable CT model and parameters can be flexibly selected based on the specific circuit's measurement accuracy requirements, protection winding type, accuracy limit coefficient, capacity, etc., without being limited by the circuit breaker model.
Easy replacement/upgrade: When the system is expanded, the protection scheme changes, or the CT itself fails, the CT can be replaced individually without replacing the expensive circuit breaker body, resulting in low maintenance costs and extremely high flexibility.
2. Convenient maintenance, calibration, and fault handling:
Intuitive visualization: The CT is exposed externally, making its condition (e.g., appearance, oil leakage, porcelain insulator damage) easy to observe.
Easy testing: Wiring and operation are very convenient when performing preventative tests (e.g., insulation resistance, turns ratio, volt-ampere characteristic tests), without requiring complex operations on the circuit breaker body.
3. Fault isolation: If the CT fails (e.g., internal open circuit, short circuit), its impact is usually limited to itself and will not directly endanger the circuit breaker chamber it is located in (especially SF6 circuit breakers), resulting in relatively low maintenance risk.
4. Mature technology, affordable price. Transparency: External CTs are long-established, standardized products with mature manufacturing processes and a highly competitive market. Their initial purchase cost is typically lower than that of circuit breakers with integrated CTs.
Their technical performance, specifications, and testing standards are highly standardized within the industry, offering users a wide range of choices.
5. Versatile Installation Locations and Strong Functionality: External CTs can be flexibly installed in different locations within the system based on the protection range and measurement requirements. For example:
Line CTs: Installed on the line side of the circuit breaker for line protection.
Bus CTs: Installed on the busbar side of the circuit breaker for busbar protection.
Transformer Bushing CTs: Dedicated to transformer protection.
This flexibility allows for more complex and precise protection configurations (such as using different CT windings for main protection, backup protection, and differential protection).
6. Facilitates Expansion and Retrofitting: In substation expansion or retrofitting projects, external CTs can be added or replaced independently of the existing circuit breaker system, making implementation relatively easier.
Comprehensive Structure and Typical Combinations
In actual products, the above forms often appear in combination:
Mainstream Form: Horizontal Layout + Built-in CT. This is the current trend in intelligent, integrated design, especially suitable for applications requiring automated protection (such as pole-mounted switches in distribution network automation).
Economic or Special Forms: Horizontal Layout + External CT. Commonly seen in cost-sensitive projects or traditional projects with existing independent CT installation solutions.
Selection Recommendations: For new automated lines, high reliability, and reduced on-site work, prioritize the "built-in CT type".
For limited budgets or special CT specification requirements, the "external CT type" can be selected.
Regarding the descriptions of "horizontal" or "center-mounted", always refer to the specific structural drawings provided by the manufacturer, paying close attention to whether the installation dimensions and wiring methods meet the site requirements.
In addition, an important and common variation of ZW7-40.5 is "with isolating switch". A combined circuit breaker (often called a "watchdog") integrates a visible disconnector on one or both sides of the circuit breaker, providing maintenance isolation and enhancing safety.
Summary
In summary, these classification terms reflect the product series characteristics developed by ZW7-40.5 to meet diverse engineering needs. When selecting a circuit breaker, the specific requirements of the project regarding installation methods, protection functions, cost budget, and maintenance habits should be comprehensively considered.
xDTZ ZW7-40.5 vacuum circuit breaker
ZW7 -40.5 outdoor vacuum circuit breaker is an outdoor high -voltage switchgear equipmment with a rated voltage of 40.5 kV and three phase AC520(60)Hz.It can be used for breaking and closing load current,overload current and short circuit current.
Shaanxi West Power Tongzhong Electrical Co., Ltd.
Our address
Nanpo Village, Chencang Avenue Jintai District Baoji City, Shaanxi Province, China
86-18091765882
xdtz04@westpowerelectric.com
