Medium Voltage Metal Enclosed Switchgear: Spec, Safety & Selection

What “metal enclosed” means in medium voltage switchgear

In the IEC 62271-200 framework, “metal enclosed” describes switchgear where primary components are contained within a grounded metal enclosure, using segregation and internal partitions to manage safety, serviceability, and fault containment. In practical engineering terms, metal enclosed MV switchgear is designed to:

• Separate busbar, breaker/functional unit, cable termination, and control/relay compartments to reduce the probability that a single issue propagates across the lineup.
• Provide defined access rules through mechanical/electrical interlocks (for example, preventing door access to live parts or preventing closing onto an earthed circuit).
• Support maintainability (inspection windows, removable modules, and test/isolated positions for withdrawable devices).

Metal enclosed vs. metal clad: why the distinction matters

Owners often use “metal enclosed” and “metal clad” interchangeably, but the procurement consequences can be significant. Metal-clad designs usually imply a higher level of compartmentalization and defined withdrawable circuit breaker construction, while metal-enclosed covers a broader set of architectures. In either case, the correct approach is to specify the performance requirements (fault rating, insulation, IP, interlocks, and internal arc strategy) and then validate that the offered design meets them under the applicable standard.

Key ratings you must specify (with practical ranges and examples)

A switchgear project typically succeeds or fails based on whether the electrical ratings are aligned with the upstream source capability and the downstream load profile. In MV systems, two common “late-stage surprises” are (1) underestimated short-circuit duties and (2) insulation levels that do not match the service environment or surge expectations.

A quick sanity check that avoids redesign

Before freezing the lineup design, validate these three items together: the utility/transformer source impedance (available fault kA), protective device clearing times (seconds), and the specified short-time withstand rating. The short-time rating is not a “paper parameter”—it directly influences busbar sizing, bracing, internal barriers, and pressure relief design, which can affect footprint and cost.

Safety engineering: interlocks, earthing, and internal fault management

Medium voltage metal enclosed switchgear is purchased primarily to control risk: risk to personnel, risk to uptime, and risk to adjacent equipment. A robust safety concept should be visible in the design features and in the routine test documentation.

Practical “must-haves” for safer operation

• A defined earthing switch strategy and interlocking logic that prevents closing the breaker onto an earthed circuit.
• Shutters or barriers for primary stabs when withdrawable devices are in test/isolated positions.
• Door-open protection rating for compartments that may be accessed during maintenance (commonly IP2X for the breaker compartment when opened).
• A pressure relief path (duct/channel) designed so that, in an internal event, energy is directed away from operators and adjacent panels.

Remote operation and visibility reduce exposure

Where the operating philosophy allows, adding remote switching, condition indication, and relay visibility reduces the need for front-of-panel interaction under energized conditions. Even basic design elements—inspection windows, clear mimic diagrams, and segregated control rooms—help operators confirm status without bypassing procedures.

Functional lineup design: feeders, bus schemes, and space-optimized solutions

A specification for MV metal enclosed switchgear should describe the functional units needed—not just “a lineup.” Common lineups include combinations of:

• Incoming feeders (utility/transformer incomers) with protection, metering, and isolation.
• Outgoing feeders to distribution transformers, MV drives, or plant substations.
• Bus sectionalizers for maintenance flexibility and fault isolation.
• Motor feeders (where MV motors are present) using contactor-based control or breaker-based protection, depending on duty and starting method.

When a compact lineup is the constraint, not an optimization

Many projects do not have the luxury of a large switchroom. In these cases, the correct design is the one that preserves segregation and maintainability while fitting the physical envelope. For example, our P/V-12(D)-W550 removable AC metal-enclosed switchgear is built for 12 kV class indoor systems and is intended for smaller space environments by integrating two vacuum circuit breakers into a single equipment configuration, while maintaining compartmentalized construction and a dedicated pressure relief channel.

In practical terms, compact switchgear should still provide the same fundamental outcomes: clear isolation boundaries, safe earthing operations, defined cable termination access, and a protection/relay scheme that is testable without unsafe workarounds.

Footprint and installation: dimensions, cable routing, and expansion planning

For most MV projects, installation constraints are the hidden cost driver. Floor loading, aisle clearances, trench locations, rear access needs, and cable bending radii can force late layout changes. Your RFQ should therefore include mechanical and routing assumptions—not just electrical ratings.

What to ask for in a layout drawing package

• General arrangement (GA) with lineup length, section widths, and depth, including rear clearance requirements.
• Cable entry/exit method (top/bottom), gland plate details, and minimum bending radius assumptions.
• Pressure relief direction and any ducting requirements.
• Future extension plan (space claim, bus extension method, and shutdown requirement).

As a reference point for indoor, withdrawable MV switchgear lineups, typical section height is often around 2200 mm, with common widths of 800–1000 mm and depth around 1500 mm depending on busbar current and cable routing. Some configurations require additional rear cabinet depth for up/down cable routing or busbar in/out transitions, which should be captured explicitly in the GA package to avoid site clashes.

Supplier evaluation checklist: what serious buyers verify

Medium voltage metal enclosed switchgear is not a commodity purchase. Beyond the datasheet, buyers should confirm the manufacturer’s engineering controls, process discipline, and ability to support commissioning. The objective is to reduce technical risk and lifecycle cost—not to optimize only first price.

Request these documents with your quotation package

1. Applicable standards list (IEC/GB/utility requirements) and declared conformance scope.
2. Type test evidence relevant to your configuration (dielectric, temperature rise, short-circuit, and internal arc approach where applicable).
3. Routine test plan for the specific lineup (wiring checks, interlock verification, primary injection or equivalent, relay functional checks as applicable).
4. GA drawings and wiring diagrams with revision control, plus a commissioning checklist.
5. Spare parts and maintenance recommendations, including operating mechanism service intervals.

If you need a concise overview of our manufacturing scope and product lines for internal stakeholder alignment, you can use the downloadable materials on our support page as a starting reference.

Conclusion: a practical path to specifying the right MV metal enclosed switchgear

A well-specified medium voltage metal enclosed switchgear lineup is one that is aligned to your fault-level study, insulation coordination, operating practices, and site constraints. The most persuasive “value” is not a feature list—it is verified performance under the standards, safer maintenance boundaries, and a layout that installs without compromises.

If you share a single-line diagram (including source data and protection philosophy), a qualified manufacturer can quickly propose an optimized configuration—often improving footprint while maintaining key ratings such as 4-second short-time withstand, appropriate IP protection, and clear interlocking/earthing logic. If you would like an engineering review for your project, you can reach our team via the contact page.