What is the basic principle of medium voltage cabinet?
Medium voltage switchgear is basic principles and functions can be summarized as follows:
I. Basic principles
Voltage conversion function
Medium voltage switchgear realizes voltage level conversion through high and low voltage isolation8. For example, 10kV high voltage electricity is switched to 35kV busbar through circuit breaker, or vice versa. This conversion is achieved through a dual-circuit switching mechanism to ensure stable operation of the system.
Circuit switching and protection mechanism
Main circuit: connects power supply and load, and realizes power on and off control through circuit breaker.
Protection function: equipped with current transformer, differential protection device, etc., monitors abnormal current (such as overcurrent, short circuit) and cuts off the circuit in time to prevent equipment damage.
Auxiliary circuit: provides power for measurement, control and signal transmission, such as connecting a multimeter for voltage measurement.
Neutral point grounding method
According to system requirements, medium-voltage switchgear can be directly grounded (such as 10kV system) or grounded through arc suppression coils to balance the system capacitance current and reduce arc grounding faults.
2. Core components and functions
Cabinet structure
It consists of a metal shell, insulating parts, conductive circuits and secondary terminals to provide physical isolation and safety protection.
Circuit breaker
The core control component has overload and short-circuit protection functions and uses high insulation performance materials to ensure safety.
Current transformer
Measurement group: used to connect instruments to display system status (such as voltage and current)
Protection group: cooperate with differential protection devices to detect fault current.
Other devices
Including fuses, load switches, disconnectors, etc., to meet the circuit switching requirements of different scenarios.
3. Workflow example
Normal operation: After the power supply is connected, it automatically switches to the main bus power supply through the control circuit.
Fault handling: If an abnormal current is detected, the protection device will disconnect the corresponding circuit and alarm at the same time.
Maintenance operation: Equipment status monitoring and adjustment can be performed through the secondary circuit.
4. Precautions
Voltage level division: China's power system adopts the standard of 10kV or less as low voltage and 10kV-66kV as medium voltage.
Standard specification: It must comply with national standards such as GB3906-1991 to ensure insulation performance and mechanical strength
Selection suggestion: Select the appropriate circuit breaker model according to parameters such as load capacity and short-circuit current.
KYN28-12 indoor armored metal-enclosed switch equipment (hereinafter referred to as KYN28-12 switchgear)by Shaanxi West Power Tongzhong Electrical Co., Ltd is suitable for three-phase AC 50HZ, 7.2~17.5kV single busbar and single busbar sectionalized power system, with perfect "five-proof" function. The removable part of the switchgear cabinet can be equipped with extractable vacuum circuit breaker or vacuum contactor, isolation trolley, PT trolley and other components.
It has many advantages :
1.Perfect structure: the cabinet is fully assembled, aluminum-zinc-plated multiple folding process structure;
2.Extremely safe: the cabinet is divided into four independent compartments as a whole, which is safe and reasonable;
3.Convenient and concise maintenance: the cabinet is equipped with a center-mounted handcart circuit breaker, which is convenient for overhaul and maintenance;
4.Complete five-proof interlock.
a.The handcart can be moved from the test/isolating position to the operating position when the circuit breaker and the earthing switch are in the open position. Reverse movement is also possible in this tripping condition (mechanical interlocking).
b.The circuit breaker can only be closed (mechanical and electrical interlocking) when the handcart is already fully in the test or operating position.
c.When the handcart is in the test or running position and there is no control voltage, the circuit breaker cannot be closed and can only be manually opened (electrical interlocking).
d.When the hand truck is in the run position, the control wire plug is locked and cannot be unplugged.
e.The earth switch can only be closed when the handcart is in the test/isolation position or removed (mechanical interlocking).
f.The handcart cannot be moved from the test/isolation position to the operating position when the earth switch is closed (mechanical interlocking).
g.Additional interlocking devices, such as latching solenoids, can be fitted to the trolley and/or earth switch actuating mechanism.
5.KYN28-12 indoor armored metal-enclosed switch equipment widely range of application: the serialized products cover a wide range, from rated current 630A to rated current 5000A, and from rated breaking current 20KA to 50kA; cover all environments within 4500 meters above sea level; cover the use environment of -40℃~40℃; the circuit breaker in the cabinet can be equipped with domestic and foreign withdrawable vacuum circuit breakers;
6.Support intelligent customization：
a.Wireless temperature intelligent monitoring program with self-powered design can be added, safe and maintenance-free.
b.Mechanical characteristics monitoring program, when monitoring the circuit breaker operation data, hidden problems early detection, early solution;
c.Motorized entry solution for remote operation to ensure personal safety.
d.Local inspection allows real-time detection of original deterioration.
