Switchgear Selection Guide: MV/LV Ratings, Internal Arc and IP Checks for EPC Projects

Introduction

Switchgear selection starts with voltage level, fault current, load current, protection philosophy, installation environment and operation requirements. Overseas projects should specify both technical ratings and documentation requirements clearly.

This guide is written for overseas buyers, EPC contractors, consultants and local utility reviewers. It uses IEC 62271 for medium-voltage switchgear, IEC 61439 for low-voltage assemblies and local utility or consultant requirements as the main technical language, with the final acceptance route defined by the project specification and local approval process.

1. Buyer Decision Points

Decision point	What to check before RFQ
Voltage class	Separates MV switchgear from LV assemblies and defines standards
Rated current	Must match continuous load and future capacity
Fault level	Determines breaking capacity and short-time withstand rating
Internal arc	Important for operator safety and room layout
IP rating	Must suit indoor, outdoor, dust, humidity and corrosion conditions

2. RFQ Data to Provide

• Single-line diagram and feeder list.
• Rated voltage, current and short-circuit level.
• Protection relay and metering requirements.
• Internal arc classification if required.
• Cable entry, enclosure IP and installation environment.
• FAT witness and document submission requirements.

3. Supplier Documents to Request

• Panel arrangement drawing.
• Single-line and schematic drawings.
• Datasheet and technical schedule.
• IEC type test references where required.
• Routine test report and FAT checklist.
• Installation and operation manual.

4. Engineering Review Checklist

Review item	Why it matters
Fault rating	Must exceed calculated system fault level
Protection scheme	Relay and CT/VT details affect coordination
Cable entry	Top/bottom entry must match site layout
Arc classification	May be required by owner or utility
Documentation	Needed for consultant review before shipment

5. Reference Standards and Local Approval

Use IEC 62271 series for MV switchgear and IEC 61439 for LV assemblies. Local utility rules may add metering, labeling, relay brand or enclosure requirements.

Buyer Recommendation

Do not buy switchgear from a model name alone. Freeze the single-line diagram, ratings, protection scheme, enclosure, cable entry and FAT documents before production.