KYN28-12 Switchgear: Technical Specifications & Features

The KYN28-12 is one of the most widely used medium voltage switchgear models in the world. You will find it in substations, factories, data centers, solar plants and commercial buildings that run on 3.6kV to 12kV networks.

This guide explains what KYN28-12 switchgear is, how it is built, what its main technical parameters are, and how to choose the right configuration for your project.

What Is KYN28-12 Switchgear?

KYN28-12 is an indoor, AC, metal-clad, withdrawable-type switchgear for three-phase systems with a rated voltage of up to 12kV and a frequency of 50Hz. It is often sold as KYN28A-12, which is the improved version of the original design.

Each letter in the model code has a meaning. K stands for metal-clad, Y for removable (withdrawable) type, N for indoor use, 28 for the design series number, and 12 for the maximum rated voltage in kV.

The cabinet is used to receive, distribute and protect electrical power. It also controls, monitors and isolates circuits in a safe and compact way.

KYN28-12 Technical Specifications

The table below summarizes the typical parameters. Exact values can vary slightly by manufacturer, so always confirm them against the type test report for your order.

Parameter	Typical Value
Rated voltage	12kV (3.6kV, 7.2kV and 12kV systems)
Rated frequency	50Hz (60Hz on request)
Rated current of main busbar	1250A, 1600A, 2000A, 2500A, 3150A, 4000A
Rated current of feeder	630A, 1000A, 1250A, 1600A, 2000A, 2500A, 3150A, 4000A
Rated short-circuit breaking current	16kA, 20kA, 25kA, 31.5kA, 40kA
Rated short-time withstand current (4s)	16kA to 40kA
Rated peak withstand current	40kA to 100kA
Power frequency withstand voltage (1 min)	42kV
Lightning impulse withstand voltage	75kV
Degree of protection	IP4X for the enclosure, IP2X with the door open
Typical cabinet size (W x D x H)	800 x 1500 x 2300 mm or 1000 x 1500 x 2300 mm

Normal Service Conditions

Standard KYN28-12 switchgear is designed for an ambient temperature between minus 15°C and plus 40°C. The altitude should not exceed 1000 meters, and the daily average relative humidity should stay below 95 percent.

For higher altitudes, heavy pollution, or extreme cold and heat, the insulation design and enclosure need to be adjusted. Tell your supplier about site conditions early.

Applicable Standards

KYN28-12 switchgear is built and tested to Chinese national standard GB/T 3906. Most export models also follow IEC 62271-200 for metal-enclosed switchgear, together with IEC 62271-100 for the circuit breaker.

Ask for a valid type test report from an accredited laboratory. It should cover dielectric tests, temperature rise, short-circuit withstand, mechanical endurance and internal arc performance.

Structure: The Four-Compartment Design

The cabinet is divided by grounded metal partitions into four independent compartments. This is the core of its safety record.

Busbar Compartment

The busbar compartment sits at the rear top of the cabinet. It holds the main busbars, which run through all adjacent panels. Busbars are usually copper and covered with insulating sleeves to reduce the risk of phase-to-phase faults.

Circuit Breaker Compartment

The front middle section holds the withdrawable circuit breaker truck. Guide rails allow the truck to move between the test position and the service position. Metal shutters automatically close when the truck is withdrawn, so live contacts stay covered.

Cable Compartment

The rear lower section holds the cable terminations, current transformers, earthing switch and surge arresters. It has enough space for several cables per phase, which is helpful for high-current feeders.

Relay and Instrument Compartment

The upper front section holds protection relays, meters, indicators and control switches. Low voltage components are fully separated from the high voltage parts, so operators can read and adjust devices safely.

Key Features of KYN28-12 Switchgear

Withdrawable Vacuum Circuit Breaker

The most common breaker is the VS1 vacuum circuit breaker, although other brands and models are also compatible. Vacuum interrupters offer long electrical life, low maintenance and fast arc extinction.

The breaker has a spring-operated mechanism. It can be charged by a motor or manually, which means the cabinet still works during an auxiliary power outage.

Five-Prevention Interlock System

A reliable mechanical interlock system protects operators from mistakes. The five functions are:

First, the breaker cannot be moved in or out while it is closed. Second, the breaker cannot be closed unless it is in the test or service position. Third, the earthing switch cannot be closed while the circuit is live. Fourth, the breaker cannot be connected to a live circuit when the earthing switch is closed. Fifth, the cable compartment door cannot be opened while the earthing switch is open.

Pressure Relief for Internal Arc Faults

Every high voltage compartment has a pressure relief flap on top. If an internal arc occurs, hot gas is vented upward in a controlled way and away from the operator. Many designs have been tested for internal arc classification, so check the report for the exact rating and duration.

Compact and Space Saving

The 800 mm width at up to 1250A makes the cabinet efficient for crowded switch rooms. Panels can be lined up side by side, with cable entry from the bottom and operation from the front.

Front Access and Easy Maintenance

Operation, inspection and most maintenance are done from the front of the panel. This allows the switchgear to be installed against a wall, which reduces the room footprint and building cost.

High Interchangeability

Breaker trucks with the same rating are interchangeable between cabinets. This shortens repair time. A spare truck can replace a faulty one in minutes.

Common Panel Types and Functions

KYN28-12 panels can be combined to form a complete medium voltage switchboard. Typical panel functions include:

Incoming feeder panels bring power from the transformer or utility. Outgoing feeder panels supply loads and transformers. Bus coupler panels connect two busbar sections. Voltage transformer panels provide metering and protection signals. Contactor panels control motors. Riser and isolating panels adapt the busbar layout.

Typical Applications

KYN28-12 switchgear is selected where reliable medium voltage distribution is needed.

Power plants and substations use it for station power and 10kV distribution. Industrial plants such as steel, cement, chemical and mining sites use it to feed large motors and transformers. Renewable energy projects, including solar and wind farms, use it as the collector switchgear. Commercial buildings, hospitals, airports and data centers use it for secure power supply. Infrastructure projects such as railways, ports and water treatment plants also rely on it.

How to Select the Right KYN28-12 Configuration

Confirm the System Voltage

Match the switchgear to your network. A 10kV, 11kV or 6.6kV system can usually use a 12kV rated unit.

Calculate Rated Current

Choose the main busbar and feeder current based on the maximum load plus a safety margin. Consider future expansion, because replacing a busbar later is costly.

Check Short-Circuit Level

Obtain the prospective fault current at the installation point from your power study. The breaking current of the breaker should be higher than this value.

Select Protection and Control

Decide on the relays, meters and communication protocols. Many projects ask for IEC 61850 or Modbus compatibility for SCADA integration.

Review Site and Environment

Ask about altitude, humidity, dust and temperature. Heaters, dehumidifiers or special coatings may be added for harsh conditions.

Installation and Maintenance Tips

Good installation protects long-term performance. Make sure the floor is level and the foundation channels are properly aligned. Check that the grounding connections are solid, and torque all bolted connections to the specified values.

For maintenance, inspect the cabinet at least once a year. Clean dust, check the shutter movement, test the interlocks and lubricate moving parts. Review contact wear and the number of breaker operations. Run protection relay tests after any setting change.

KYN28-12 vs Other Medium Voltage Switchgear

Compared with fixed-type switchgear such as the XGN series, KYN28-12 offers a withdrawable breaker and stronger compartment separation. This improves both safety and maintenance speed.

Compared with a ring main unit, it handles much higher current and more feeders. A ring main unit is better for compact secondary distribution, while the KYN28-12 suits main switchrooms and heavy industrial loads.

Compared with gas-insulated switchgear, it uses air insulation, which makes it more affordable and simpler to maintain, although it needs more space.

Optional Configurations and Smart Add-Ons

Many buyers upgrade the basic cabinet with extra devices. These options improve monitoring, safety and ease of operation.

Intelligent Monitoring

Temperature sensors on busbar joints and cable terminals give early warning of loose connections. Partial discharge sensors help detect insulation problems before a failure occurs. Data can be sent to a remote control room through a communication gateway.

Live Display and Voltage Indication

A capacitive live display shows whether the cable side is energized. It can also be linked with the earthing switch interlock, which adds another safety layer for operators.

Heaters and Dehumidifiers

In humid or coastal areas, space heaters with humidity controllers prevent condensation inside the cabinet. This protects insulators and extends service life.

Motorized Earthing Switch

A motorized earthing switch allows remote operation and supports faster, safer switching routines in unmanned substations.

What to Check When Sourcing KYN28-12 Switchgear

Price matters, but quality decides the long-term cost. Use this short checklist when comparing suppliers.

Look at the steel sheet thickness and surface treatment, because aluminum-zinc coated sheet resists corrosion better. Confirm the copper busbar purity and cross-section. Check that the breaker brand and relay brand match your quotation.

Ask for factory acceptance testing before shipment, including power frequency withstand, main circuit resistance and mechanical operation tests. Finally, confirm the warranty period, spare parts supply and after-sales support in your country.

Frequently Asked Questions

What does KYN28-12 mean?

It means a metal-clad, withdrawable, indoor switchgear with a rated voltage of 12kV, and 28 is the design series.

Is KYN28-12 the same as KYN28A-12?

They are very close. KYN28A-12 is the upgraded design, and the two names are often used interchangeably in the market.

Can KYN28-12 be used outdoors?

No. It is designed for indoor use. For outdoor installation, place it inside a prefabricated substation or a dedicated enclosure.

What is the maximum current of KYN28-12?

The common maximum rated current is 4000A, depending on the cabinet size and cooling design.

Which circuit breaker is used?

Most units use a withdrawable vacuum circuit breaker such as the VS1 type.

KYN28-12 switchgear combines safety, flexibility and cost efficiency. Its four-compartment structure, withdrawable vacuum breaker, reliable interlocks and wide range of ratings make it a strong choice for 12kV distribution.

Before ordering, define your voltage, current and fault level, request complete type test reports, and compare configurations from qualified manufacturers. A well-specified KYN28-12 system will provide stable power for decades.