ZW7-40.5 outdoor vacuum CT with an external current transformer is particularly suitable for scenarios with high requirements for power supply reliability, measurement accuracy, and protection performance, such as county-level power supply networks, the main step-down stations of large industrial and mining enterprises, and the transmission lines of new energy booster stations.
DO you know the advantages of the ZW7-40.5 outdoor vacuum CT with an external current transformer ?
The main advantage of the design with an external CT lies in "specialized division of labor" and "flexibility". The circuit breaker focuses on its core function - interrupting and closing currents, while the measurement and protection functions are handled by independent and dedicated CTs. This enables both to achieve optimal performance in their respective fields.
1. High measurement and protection accuracy, superior performance
Independent magnetic circuit, no interference: The external CT is an independent device with its own dedicated core and windings. The core material can be optimized according to its function: The CT for measurement focuses on accuracy under normal current, while under short-circuit current, it is prone to saturation to protect the instrument; the CT for protection focuses on maintaining a certain degree of linearity under short-circuit large current to ensure the reliable operation of the protection relay. The magnetic circuit of the built-in CT is similar to that of the circuit breaker, and may be interfered with by the magnetic field generated when the circuit breaker is opened.
Higher accuracy level: The external CT can easily achieve higher accuracy, for example, the measurement accuracy can reach 0.2S level, 0.5S level, and the protection accuracy can reach 5P20, 10P20, etc., meeting the requirements of metering and advanced protection. The built-in CT is limited by installation space and electromagnetic environment, and its accuracy is usually lower.
2. Extremely flexible and configurable
Flexible winding configuration: An external CT can easily be equipped with multiple secondary windings (for example, 4 cores: 2 for protection, 2 for measurement/), which can be provided to different devices (protection devices, measurement and control devices, energy meters, etc.) for use, without affecting each other. Inbuilt CT is limited by space, and the number and capacity of windings are usually limited.
Easy expansion and renovation： If the future load of the line increases or new functions (such as differential protection) are needed, only the external CT needs to be replaced or increased, without the need to replace the entire circuit breaker, greatly saving costs and construction time.
3. Enhancement of Safety and Reliability
More secure during maintenance and repair: When it is necessary to calibrate or replace the CT, the external structure makes the operation very simple. Just disconnect the secondary wiring and isolate the CT. The connection with the circuit breaker body is minimal, and the safety measures are easier to implement. While maintaining an internal CT, it is equivalent to opening the cover and disassembling the circuit breaker body, which is a complex procedure with a large power outage area and high risks.
Clear fault isolation: CT and circuit breaker are two independent devices. If the CT fails (such as a secondary open circuit or insulation damage), it can be dealt with separately without affecting the mechanical performance and insulation performance of the circuit breaker. Conversely, a failure of the circuit breaker body will not affect the CT.
4. More economical
Reduce the total life cycle cost:
Initial investment: Although the total price of "circuit breaker + external CT + installation bracket" may be slightly higher than that of a circuit breaker with an internal CT at the initial purchase, it is more economical in the long run.
Verification cost: The disassembly and submission for inspection of the external CT are very convenient, and the verification cost is low, with short power outage time.
5. Good standardization and interchangeability
The external CT is a standard component. CTs with the same parameters produced by different manufacturers can be basically interchanged. This makes the management of spare parts simpler, the procurement channels wider, and it is not restricted by the manufacturer of the circuit breaker.
Shaanxi West Powder Tongzhong Electrical Co., Ltd. has been dedicated to the research, development, promotion and application of new products and new technologies in the power distribution system; the development, production, sales and maintenance and debugging services of high and low voltage power equipment. This outdoor vacuum circuit breaker with an external current transformer, ZW7-40.5, is our best-selling product, and it has received high user recognition and satisfaction.
For more information ,pls contact me
Shaanxi West Power Tongzhong Electrical Co., Ltd.
Contact: Ms.Grace Liu (Director of Sales Department)
Email:xdtz04@westpowerelectric.com
Tel: +86 917 3661109 Fax: +86 917 6739416
Mobile: +86 18091765882(WhatsApp/Wechat/skype )
Website:https://www.xdtzelectrical.com
Add: Nanpo Village, Chencang Avenue Jintai District Baoji City, Shaanxi Province, China.
