Vacuum circuit breakers, as crucial electrical protection and control devices in power systems, must meet a series of strict basic requirements to ensure the safe, reliable and stable operation of the system. These requirements cover multiple aspects such as electrical performance, mechanical characteristics, environmental adaptability and safety regulations, specifically as follows:
Current-carrying Capacity
Peak Withstand Current: It must be capable of withstanding the electromagnetic force generated by the rated peak withstand current (dynamic stability current) and maintaining the integrity of the mechanical structure.
Breaking and Making Capacity
Rated Short-circuit Breaking Current: It must be capable of reliably breaking the maximum short-circuit fault current that may occur in the system (usually expressed as the symmetrical RMS value and including asymmetric components).
Breaking Time: The time from the issuance of the protection signal to the extinction of the arc should be extremely short (the full breaking time is typically 2-3 cycles) to limit the damage caused by the fault.
Making Capacity: It must have a short-circuit making capacity matching the breaking capacity (the peak current is usually more than 2.5 times the breaking current) to handle the pre-breakdown at the moment of closing.
Breaking Small Current Capacity: It must be capable of reliably breaking capacitive currents (such as capacitor banks, unloaded lines) and inductive currents (such as unloaded transformers, motors) without generating overvoltage or re-ignition.
Service Life Requirements
Electrical life: To complete the standard number of operations at the rated current and specified breaking current without significant performance degradation.
Mechanical life: Generally, tens of thousands of mechanical operations (such as 10,000 to 30,000 times) without failure are required.
Mechanical and Operational Characteristics
1.The type of mechanism can be a spring mechanism, permanent magnet mechanism or hydraulic mechanism, and it must meet the following requirements:
- Opening/closing speed: The movement speed of the contacts must be within the set range to ensure reliable arc extinguishing and medium recovery.
- Operating power: It should provide sufficient energy to overcome resistance and complete the opening and closing operations.
- Anti-jump function: Prevent multiple opening and closing operations.
- Interlocking and locking: It should have electrical and mechanical interlocking to prevent misoperation (such as interlocking of grounding switches).
2. Mechanical characteristic stability
Parameters such as contact travel, overtravel, and simultaneity (time difference for opening and closing of three phases) should remain consistent, and the variation after long-term operation should be within the allowable range.
Safety and Protection Functions
1. Safety Design of the Main Body
Enclosure Protection: Prevents personnel from coming into contact with live parts.
Pressure Relief Channel: Directed pressure relief in case of internal faults to avoid explosion risks.
2. Condition Monitoring and Intelligence
Modern vacuum circuit breakers often integrate monitoring functions, such as vacuum degree monitoring (indirectly judged through coupling capacitors or sensors), mechanical characteristic monitoring (opening and closing speed, travel curve), and contact electrical wear monitoring (estimated through cumulative breaking current).
Economy and Reliability
1. Life-cycle cost
Under the premise of meeting performance requirements, it takes into account manufacturing cost, maintenance cost and long service life.
2. Operational reliability
It features a high mean time between failures (MTBF), low failure rate, and meets the high reliability requirements of the power system.
The design, manufacture and selection of vacuum circuit breakers need to comprehensively balance the above requirements to ensure the core functions of safe isolation of faults, rapid current interruption and long-term stable operation in the power system. With the development of smart grids, higher demands have also been placed on the intelligence, integration and environmental friendliness (such as SF₆-free) of vacuum circuit breakers.
ZN85-40.5 vacuum circuit breaker
The new generation ZN85-40.5 vacuum circuit breaker produced by Shaanxi West Power Tongzhong Electrical Co., Ltd. is an upgrade product based on the 35kV vacuum circuit breaker with the 3AV3 mechanism as the main body. It has been fully optimized and upgraded in terms of mechanical transmission, mechanism body, secondary circuit, and other aspects. This product is an indoor switchgear with a rated voltage of 40.5kV and AC 50Hz.
Shaanxi West Power Tongzhong Electrical Co., Ltd.
Our address
Nanpo Village, Chencang Avenue Jintai District Baoji City, Shaanxi Province, China.
Phone Number
+86-18091765882(whatsapp )
