Introduction
Switchgear selection is one of the most consequential decisions in electrical system design. The wrong choice — a fixed-type cabinet where a withdrawable type is needed, or a low-voltage panel where medium voltage is required — can result in costly redesign, safety hazards, or regulatory non-compliance.
This guide compares four switchgear types commonly used in industrial substations and distribution systems: KYN28A-12 (medium voltage, metal-clad), MNS (low voltage, drawer-type), GCK (low voltage, drawer-type MCC), and GGD (low voltage, fixed-type). We explain the key differences, applicable standards, and how to select the right type for your application.
The Fundamental Distinction: Medium Voltage vs Low Voltage
Before comparing specific models, the most important distinction is voltage level:
- KYN28A-12: Medium voltage (MV) switchgear, rated 3.6–12kV. Used at the primary distribution level, typically receiving power from the utility at 6kV, 10kV, or 11kV.
- MNS, GCK, GGD: Low voltage (LV) switchgear, rated up to 1000V AC. Used at the secondary distribution level, after the step-down transformer.
In a typical industrial substation, the KYN28A-12 is installed on the MV side of the transformer, and the MNS/GCK/GGD is installed on the LV side. They are not interchangeable.
KYN28A-12: Metal-Clad Armored Withdrawable Switchgear (3.6–12kV)
Design and Construction
The KYN28A-12 is a metal-clad, armored, withdrawable medium voltage switchgear. Key design features:
- Metal-clad construction: All live parts are enclosed in grounded metal compartments, providing maximum safety for operators
- Withdrawable circuit breaker: The vacuum circuit breaker (VCB) is mounted on a withdrawable truck that can be moved to service, test, or isolated positions without de-energizing the busbar
- Three-position isolation: Connected, test (secondary circuits connected, primary isolated), and isolated positions provide safe working conditions
- Arc-resistant design: Internal arc fault energy is directed through pressure relief flaps to protect operators
- Compartmentalization: Busbar compartment, circuit breaker compartment, and cable compartment are physically separated
Applications
- Primary distribution in industrial plants, mines, and large commercial buildings
- Feeder protection for step-down transformers
- Motor feeders for large MV motors (above 1MW)
- Tie breakers and bus couplers in ring main or double busbar systems
- Renewable energy collection systems (wind farm, solar farm MV collection)
Standards
- IEC 62271-200: AC metal-enclosed switchgear and controlgear for rated voltages above 1kV and up to and including 52kV
- IEC 62271-100: High-voltage alternating-current circuit breakers
- GB/T 3906: Chinese national standard for 3.6–40.5kV AC metal-enclosed switchgear
MNS: Low Voltage Drawer-Type Switchgear
Design and Construction
The MNS (originally developed by ABB, now a widely adopted open standard) is a modular, drawer-type low voltage switchgear system. Key features:
- Modular drawer system: Functional units (feeders, motor starters, bus couplers) are mounted in standardized drawers that can be withdrawn for maintenance without de-energizing adjacent drawers
- High packing density: Multiple drawers per panel, with drawer heights in multiples of 25mm (E/2 module system)
- Busbar system: Horizontal and vertical busbars rated up to 6300A
- Form 4b separation: Per IEC 61439-1, terminals for external conductors are in a separate compartment from the functional units
- Standardized interfaces: Drawers from different manufacturers are interchangeable within the MNS system
Applications
- Main LV distribution boards (MLVDB) in industrial plants
- Motor control centers (MCCs) for large numbers of motors
- Power distribution in data centers, hospitals, and large commercial buildings
- Applications requiring high availability where individual feeders must be maintained without system shutdown
Standards
- IEC 61439-1: General rules for low-voltage switchgear and controlgear assemblies
- IEC 61439-2: Power switchgear and controlgear assemblies
- GB/T 7251.1: Chinese national standard equivalent to IEC 61439-1
GCK: Drawer-Type AC Low Voltage Switchgear (MCC Panel)
Design and Construction
The GCK (also known as GCK2000) is a Chinese-standard drawer-type low voltage switchgear specifically designed as a motor control center (MCC). It is similar in concept to the MNS but follows Chinese national standards and is optimized for motor control applications:
- Drawer-type motor starters: Each drawer contains a complete motor starter (MCCB + contactor + overload relay + control circuit)
- Standardized drawer sizes: 1/4, 1/2, 3/4, and full-height drawers for different motor ratings
- Busbar ratings: Up to 4000A horizontal busbar
- Protection degree: IP30 standard, IP40 optional
GCK vs MNS: Key Differences
| Parameter | MNS | GCK2000 |
|---|---|---|
| Origin standard | IEC 61439 (international) | GB/T 7251 (Chinese national) |
| Primary application | General LV distribution + MCC | Motor control center (MCC) |
| Drawer system | 25mm module (E/2) | Chinese standard module |
| Busbar rating | Up to 6300A | Up to 4000A |
| International interchangeability | High | Limited to Chinese standard |
| Cost | Higher | Lower |
GGD: Fixed AC Low Voltage Switchgear
Design and Construction
The GGD is a fixed-type (non-withdrawable) low voltage power distribution cabinet. Unlike the MNS and GCK, the GGD does not have withdrawable drawers — all components are fixed-mounted and the panel must be de-energized for maintenance.
- Fixed mounting: MCCBs, contactors, and busbars are fixed-mounted. No withdrawable units.
- Lower cost: Simpler construction results in significantly lower cost than drawer-type switchgear
- Higher current ratings: Available up to 4000A busbar rating
- Larger footprint: Fixed mounting requires more space per functional unit than drawer-type
- Protection degree: IP30 standard
When to Use GGD vs Drawer-Type
The GGD is appropriate when:
- The number of outgoing feeders is small (typically fewer than 12)
- Planned maintenance can be performed during scheduled shutdowns
- Budget is the primary constraint
- The application is a simple power distribution board without motor control functions
Drawer-type switchgear (MNS or GCK) is required when:
- High availability is required and individual feeders must be maintained without system shutdown
- A large number of motor starters must be accommodated in a compact footprint
- Future expansion is anticipated (drawers can be added without rewiring the busbar)
Selection Summary
| Application | Recommended Type |
|---|---|
| MV primary distribution (6–12kV) | KYN28A-12 |
| LV main distribution board, high availability | MNS |
| Motor control center (MCC), Chinese standard | GCK2000 |
| Simple LV power distribution, budget-conscious | GGD |
| Mining LV distribution (380V–1140V) | PKD Mine Distribution Box |
Wanlong Electric Switchgear Products
Wanlong Electric manufactures a complete range of switchgear for industrial and mining applications:
- KYN28A-12 — Metal-clad armored withdrawable MV switchgear, 3.6–12kV. Vacuum circuit breaker. IEC 62271-200, GB/T 3906.
- MNS Low Voltage Switchgear — Drawer-type LV distribution panel. Up to 6300A busbar. IEC 61439-1/2.
- GCK2000 MCC Panel — Drawer-type motor control center. Up to 4000A. GB/T 7251.
- GGD Fixed Switchgear — Fixed-type LV power distribution cabinet. Up to 4000A. Cost-effective solution.
- PKD Mine Distribution Box — 380V–1140V mining-rated LV distribution. Explosion-proof options available.
- Intelligent Low Voltage Switchgear — MNS/GCS/GGD type with intelligent monitoring and communication.
All products manufactured under ISO 9001. OEM/ODM available — custom busbar ratings, protection configurations, and enclosure dimensions. For technical specifications or a quotation, contact our engineering team. English-language support, response within 24 hours.
Related: Air Circuit Breaker (ACB) | Molded Case Circuit Breaker (MCCB) | Automatic Transfer Switch (ATS)
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