When engineers and procurement managers search for medium voltage switchgear, they rarely start with a blank slate. Most already have a voltage level in mind, a facility type they are designing for, or a maintenance philosophy they need to accommodate. What they need is a clear breakdown of how the major product types actually differ, which specifications truly matter for their application, and what questions to ask a manufacturer before committing to a purchase order.
This guide covers all of that. It focuses on the three configurations that appear most often in industrial and utility projects worldwide: Metal Enclosed Switchgear, AC Metal Clad Switchgear, and ARMORED Drawout Switchgear. Understanding how these three relate to one another is the foundation of any sound selection decision.
Electrical substation switchgear room
What Medium Voltage Switchgear Actually Does
Medium voltage switchgear is the layer of equipment that sits between a high-voltage transmission source and the distribution circuits feeding buildings, motors, transformers, and other loads. Its primary jobs are controlling power flow, isolating faults quickly, and allowing maintenance to be carried out safely.
The term "medium voltage" covers a wide band. The voltage range is commonly understood to mean distribution systems above 1 kV and generally up to and including 52 kV. In practice, most commercial and industrial MV switchgear is specified in the 3.3 kV to 36 kV range. Below that sits low-voltage gear rated under 1 kV, used in residential and small commercial buildings. Above it sits high-voltage transmission equipment, which requires fundamentally different insulation and clearance strategies.
The distinction between MV and LV switchgear is not just a voltage number. MV switchgear balances cost, maintenance over time, and size, making it suitable for small to large industrial facilities, substations, and utility distribution networks. That balance is why the category is so broad and why the choice between construction types carries real consequences for both upfront cost and long-term operating expense.
The Three Major Construction Types
Metal Enclosed Switchgear
Metal Enclosed Switchgear is the broader, more inclusive category of the three. Metal enclosed switchgear does not require full compartmentalization of internal components. All primary components, including circuit breakers, bus bars, and cable connections, may share a single enclosure rather than being separated by grounded metal barriers between each functional zone.
This construction approach has practical advantages. Metal enclosed switchgear is typically less expensive, has a smaller footprint, and can offer a wider variety of bussing and connection options compared to metal clad switchgear. For projects where fault current levels are moderate and the environment is relatively stable, this design delivers solid performance without the cost premium associated with fully compartmentalized gear.
Metal enclosed switchgear is often selected for its cost-effectiveness and is suitable for applications with lower fault current levels. It meets both ANSI and IEEE standards, ensuring reliability for specific environments.
Where Metal Enclosed Switchgear fits best: secondary substations, smaller commercial facilities, applications where space is limited and fault current is manageable, and projects where budget discipline is a primary constraint.
AC Metal Clad Switchgear
AC Metal Clad Switchgear represents the higher tier of medium voltage construction. The defining characteristic is compartmentalization. Each functional component, including the circuit breaker, busbars, and cable compartments, is isolated within its own grounded sheet metal enclosure. These compartments are fully segregated to prevent accidental contact and contain potential faults.
The safety implications of this design are significant. From a safety standpoint, metal clad switchgear offers superior protection. The compartmentalization limits the spread of faults, reduces the risk of arc flash propagation, and allows maintenance to be performed on one section while adjacent sections remain energized.
The circuit breakers used in AC Metal Clad Switchgear are drawout types as a standard requirement, not an optional feature. The drawout nature of its breakers allows for simplified maintenance and testing. A breaker can be physically moved through connected, test, and disconnected positions without de-energizing the entire lineup. Spare breakers can be pre-tested, and breakers can be swapped with minimal disruption to electrical service. Control systems and protective relays can be tested in the TEST position without impacting the associated power distribution feeder.
Metal clad switchgear adheres to rigorous industry standards such as IEC 62271-200 and ANSI/IEEE C37.20.2. Voltage ratings typically run from 4.76 kV up to 38 kV on the high end, covering the majority of industrial and large commercial applications.
Where AC Metal Clad Switchgear fits best: mission-critical facilities such as hospitals, data centers, and manufacturing plants where uptime requirements are high; environments with elevated fault current levels; and projects where maintenance flexibility over the life of the installation justifies the higher initial investment.
ARMORED Drawout Switchgear
ARMORED Drawout Switchgear is a term that appears frequently in project specifications written to IEC standards and in Chinese-manufactured switchgear exported under GB 3906 frameworks, though the underlying engineering concept maps closely to what North American standards define as metal clad. The name itself communicates the design intent: the enclosure provides a physical armor around each compartment, and the circuit breaker is withdrawable rather than fixed in place.
Armored switchgear features a four-compartment structure covering the busbar zone, breaker zone, cable zone, and control zone. This structure ensures that a fault developing in one zone is contained there, protecting both personnel and adjacent equipment. The breaker, typically a vacuum circuit breaker in modern designs, can be racked between positions while remaining within the enclosure, eliminating the need for personnel to be near live conductors during routine operations.
Armored removable AC switchgear is designed to offer enhanced safety and durability, ensuring a reliable power supply in harsh environments. Its sturdy construction resists external impacts, making it ideal for challenging site conditions. The modular nature of the design also facilitates easy maintenance and future upgrades.
For medium voltage applications ranging from 1 kV to 35 kV, armored switchgear is ideal for industrial plants, utility substations, and large-scale infrastructure. The KYN28A-12 series is one widely referenced product line in this category, commonly specified for 10 kV distribution projects across Asia, the Middle East, and Africa. At 35 kV, armored drawout configurations are the standard of care for primary substation work.
Where ARMORED Drawout Switchgear fits best: projects specifying to IEC 62271-200 or GB 3906; utility substations and ring network applications in markets where Chinese-manufactured switchgear is prevalent; and facilities requiring robust fault containment in combination with the operational flexibility of a withdrawable breaker mechanism.
GANGHENG XGN17-40.5 Box-Type Fixed AC Metal-Enclosed Switchgear
Key Specifications to Evaluate
Choosing a construction type is only part of the selection process. Every specification package needs to address the following technical parameters before going to a manufacturer for quotation.
Rated Voltage (Ur). This is the maximum continuous operating voltage the equipment is designed to handle. The rated voltage must be selected higher than the highest value of the operating voltage and is associated with an insulation level. Common ratings for industrial projects are 12 kV, 24 kV, and 36 kV. Specifying a rating too close to the actual system voltage leaves no headroom for transient overvoltages.
Basic Insulation Level (BIL). This value defines how well the switchgear withstands lightning impulse events. The lightning impulse withstand voltage covers all events at high frequency, typically overvoltages of external origin. Matching the BIL of the switchgear to the surge arresters and cable terminations in the same circuit is a requirement that engineers sometimes overlook when assembling a specification.
Rated Normal Current. This is the continuous current the main busbars and the circuit breakers must carry without exceeding temperature limits. Standard ratings for MV lineups range from 630 A at the lower end to 3,000 A or higher for main incomer sections in large facilities.
Short-Circuit Rating. The short-circuit rating must state the symmetrical kA value and the duration, typically one second, for breakers, busbars, earthing switches, and disconnects. Making current capability must also be included. Undersizing the short-circuit rating is one of the more serious errors in switchgear specification because it affects both equipment survival during a fault and the safety of personnel nearby.
Standards Compliance. Projects with international buyers or lenders will require clear declaration of the applicable standard. IEC 62271-200 governs metal enclosed MV switchgear under the international framework. ANSI/IEEE C37.20.2 applies to metal clad switchgear in North American markets. Compliance with safety standards drives modern selection practices. For export projects from China, GB 3906 alignment is also common and should be confirmed with the manufacturer.
Environmental Rating. Environmental factors such as humidity and temperature are important considerations when choosing switchgear to ensure reliable performance. Outdoor installations require additional weatherproofing, and tropical or coastal environments may call for anti-condensation heaters and upgraded surface treatments. IP rating requirements should be stated explicitly in the specification.
How to Compare Suppliers
Once the technical specification is clear, the selection process shifts to evaluating manufacturers. A few areas deserve particular attention.
Type test documentation is not optional. A properly tested switchgear lineup will have internal arc classification certificates, short-circuit withstand test reports, and temperature rise test records. Manufacturers who cannot produce these documents are selling on price alone, and the risk profile of that purchase is difficult to justify on any project of significance.
Factory production capability matters more than brochure claims. Established MV switchgear manufacturers maintain dedicated production lines with CNC fabrication for enclosure components, controlled processes for bus bar assembly, and in-house high-potential testing before shipment. Asking for a factory audit or a production inspection arrangement is reasonable for orders of meaningful scale.
Lead time and spare parts availability are often underweighted in the initial evaluation. A switchgear lineup that takes 20 weeks to produce and has no locally stocked replacement breakers creates operational risk for the facility owner. Understanding the manufacturer's standard delivery schedule, available spare breaker inventory, and after-sales support network should be part of the vendor comparison, not an afterthought at the purchase order stage.
Selecting the Right Type for Your Project
The decision between Metal Enclosed Switchgear, AC Metal Clad Switchgear, and ARMORED Drawout Switchgear ultimately comes down to three factors: the level of fault current present in the system, the maintenance philosophy of the facility, and the applicable standards framework.
For projects with lower fault current levels, stable environments, and tighter budgets, Metal Enclosed Switchgear delivers adequate performance at a competitive price point. For mission-critical facilities where arc flash containment and live-bus maintenance capability are non-negotiable, AC Metal Clad Switchgear is the appropriate choice. For projects specifying to IEC or GB frameworks, particularly in utility and infrastructure contexts, ARMORED Drawout Switchgear provides the compartmentalized, withdrawable-breaker design that engineers and utilities in those markets expect.
None of these types is inherently superior. Each is an engineering response to a defined set of requirements. The buyer who arrives at a manufacturer with a clear understanding of those requirements, backed by a detailed specification, will consistently get better pricing, better compliance, and fewer surprises during commissioning than the buyer who leaves the selection to the supplier.
If you are working through the specification for an upcoming project and need technical guidance on rated parameters, type test requirements, or production lead times, the right starting point is a conversation with a manufacturer who can show documentation for all three.