The KYN28A-12 medium-voltage switchgear, officially known as an indoor metal-clad withdrawable switchgear, is a common type of high-voltage switchgear in China. Its rated voltage ranges from 3.6kV to 12kV. The vacuum circuit breaker is centrally located, meaning it's situated in the middle of the front panel, freeing up space below for future expansion or as a cable compartment. In this model number, K represents metal-clad, Y represents withdrawable, N represents indoor, 28A is the industry-issued serial number, and 12 represents a rated operating voltage of 12kV. Other similar medium-voltage switchgear models in China include KYN28, KYN96, and KYN44.
In the metallurgical industry, metallurgical production involves a large number of high-power equipment, such as electric arc furnaces and rolling mills. These devices have extremely high requirements for power stability and reliability. The KYN28A-12 central power switchgear boasts a high protection level, employing an armored aluminum-zinc coated steel shell with an IP4X protection rating, effectively preventing dust and debris from entering and ensuring stable equipment operation. Simultaneously, its strong load capacity can meet the significant load demands of metallurgical equipment. For example, a large steel plant's rolling mill production line uses the KYN28A-12 central power switchgear for power distribution and control, ensuring continuous and stable operation of the production line and improving production efficiency.
The petrochemical industry also has stringent requirements for power supply, as various reaction units and conveying equipment in petrochemical production require reliable power support. The KYN28A-12 medium-voltage switchgear features comprehensive five-proof interlocking functions, preventing safety accidents caused by misoperation and ensuring the safety of petrochemical production. For example, in the refinery of a large petrochemical enterprise, the KYN28A-12 medium-voltage switchgear is used in the high-voltage power distribution system to monitor and protect the circuits, ensuring power safety during the production process.
Commercial venues such as shopping malls, airports, and subways have high population density and extremely high requirements for power reliability and security. The KYN28A-12 central switchgear can serve as a device for receiving and distributing high-voltage network power, ensuring the normal operation of these venues. For example, in large shopping malls, lighting, air conditioning, and elevator systems all rely on a stable power supply. The KYN28A-12 central switchgear can effectively control and protect circuits, ensuring the normal operation of various equipment within the mall. Airport navigation equipment, terminal lighting and air conditioning systems, as well as subway train operations and station lighting all depend on reliable power support, and the KYN28A-12 central switchgear plays a crucial role in these locations.
The KYN28A-12 medium-voltage switchgear is also widely used in urban residential buildings, schools, hospitals, and other locations. Residential buildings require a stable power supply to meet daily needs such as lighting and appliance use. School teaching equipment and laboratory instruments rely on electricity, and hospital medical equipment has extremely high requirements for power reliability. The KYN28A-12 medium-voltage switchgear can provide safe and reliable power distribution and control for these locations, ensuring the normal lives of residents, the teaching order of schools, and the medical services of hospitals. For example, in critical areas such as operating rooms and intensive care units of a hospital, the use of the KYN28A-12 medium-voltage switchgear ensures a stable power supply, safeguarding the lives of patients.
In power plants, the KYN28A-12 central switchgear can be used for power transmission from small and medium-sized generators, enabling power control, protection, and monitoring. In wind farms, with the increasing number of wind turbines, the requirements for centralized power management and distribution are also rising. The KYN28A-12 central switchgear can adapt to the special environment and power demands of wind power generation, ensuring the stable operation of the wind farm. For example, a wind farm uses the KYN28A-12 central switchgear to collect and distribute power from various wind turbines, improving power generation efficiency and the stability of power transmission.
The cabinet is constructed entirely of powder-coated aluminum-zinc coated steel or stainless steel, with a thickness of at least 1.5mm. This material offers strong corrosion resistance, ensuring long-term use of the cabinet in various environments. Except for the main frame, all other cabinet components are sheet metal, resulting in a lightweight and aesthetically pleasing design.
The cabinet has no fasteners on its surface for easy removal, providing excellent anti-theft protection. It boasts an IP3X protection rating and good rainproof performance. The top cover features a double-layered air-insulated structure with ventilation openings. The air inlet is located on the cabinet's surface panel and includes a removable dust filter; the air outlet is located at the top of the cabinet, concealed under the eaves, creating upward air convection for good insulation and ventilation. The top cover also has a 3-degree drainage angle. The cabinet features a sealed floor with a cable inlet to prevent moisture from cable trenches from entering. Doors and lifting lugs are sealed with weatherstripping. Side doors are operable upon request, and the door locks are rainproof. A limit hook ensures the door is securely locked when open.
The KYN28A-12 medium-voltage switchgear uses a handcart-type vacuum circuit breaker, ensuring safe operation. When replacing the circuit breaker, simply pull out the handcart manually and replace it with the new switch; no power outage is required, facilitating maintenance. Vacuum circuit breakers offer advantages such as strong arc-extinguishing capability and long service life, effectively ensuring the normal switching of circuits.
The ZWB is equipped with digital input contacts to determine the circuit breaker's position (closed or open), the trolley's working position, and the trolley's test position. Monitoring these contacts allows for real-time control of the circuit breaker's operating status, ensuring the safe operation of the power system.
In a traditional KYN28A-12 (DC-operated) incoming/outgoing line cabinet, a current transformer 2TA collects the system current signal and introduces it into the current relay KA. Relays 1KA-3KA are instantaneous trip protection relays. When the system current (if any phase) suddenly increases to the limit allowable value, KC activates, immediately sending a signal. The signal relay 1KS operates, and the indicator light displays the instantaneous trip signal. Simultaneously, the normally open contact (1-03) of KC connects the circuit of the intermediate relay KCF, causing the circuit breaker QF to trip. The line switch TQ is energized and activated, and QF trips. Relays 4KA-6KA are overcurrent protection relays. When the system current reaches the overcurrent protection setting value (generally 1.3-1.5 times the rated current), the time relay 1KT activates and begins a delay. When the set time is reached, 1KT (1-07) connects to 2KS, the indicator light displays the overcurrent signal, and simultaneously 1KT connects the circuit of KCF, causing the circuit breaker to trip. KCF is an intermediate relay with both a current coil and a voltage coil, also known as an anti-pumping relay.
The KYN28A-12 (AC/DC operation) incoming/outgoing line cabinet uses the integrated microcomputer protection device ZWB. This device also uses a 2TA current transformer to collect current signals and feeds them into the ZWB. The ZWB can receive or output high-voltage signals (0-5A current signals), then converts them into digital signals that the microcomputer can receive and recognize through analog-to-digital (A/D) conversion. These digital signals are then fed into the calculation and programming system, which issues corresponding signals according to the set program. The integrated microcomputer protection device is a relay protection device specifically developed for this cabinet, based primarily on computer technology.
In the KYN28A-12 incoming and outgoing line cabinet, the small bus voltage signal is connected to the X2-1, X2-2, X2-3, and X2-4 contacts of ZWB via fuse 3-5FU. These signals also need to undergo analog-to-digital (A/D) conversion and be introduced into the calculation and program system, and then the corresponding signals are issued according to the set program.
The KYN28A-12 medium-voltage switchgear can be configured with an electric chassis trolley and an electric grounding switch, featuring automatic mechanical interlocking to meet distribution network automation requirements. The electric chassis trolley enables automatic movement of the handcart, improving operational efficiency; the electric grounding switch automates grounding operations, ensuring operator safety.
In summary, the KYN28A-12 medium-voltage switchgear plays a vital role in power systems due to its wide applicability and comprehensive standard configuration. It can be found in industrial, commercial, residential, and energy sectors. Its standard configuration, from the cabinet structure to the design of each system, fully considers safety, reliability, and convenience, providing strong support for stable power supply and normal equipment operation.