Switchgear Selection Guide

Switchgear Selection Guide for MV and LV Projects

Switchgear selection is a protection and continuity decision, not only a cabinet purchase. For utility substations, industrial plants, solar farms, data centers, and EPC projects, the selected switchgear must match the system voltage, load current, short-circuit level, installation environment, control philosophy, and operator safety requirements.

This guide consolidates the former MV/LV switchgear selection content into the official switchgear article slug. The legacy swgr-selection-guide URL should redirect here to avoid duplicate content.

1. Define the Electrical System First

• Voltage level: Confirm whether the project requires LV switchgear up to 1 kV, MV switchgear such as 12 kV / 24 kV / 36 kV, or a combined substation lineup.
• Rated current: Size busbar and incoming feeders based on continuous load, diversity, motor starting, and future expansion.
• Short-circuit level: Use a fault study to define the required breaking capacity and short-time withstand current.
• Installation environment: Indoor, outdoor, dusty, coastal, high-humidity, or high-altitude conditions affect enclosure and insulation choices.

2. Medium Voltage Switchgear

Medium voltage switchgear is typically used for utility incoming feeders, transformer protection, solar step-up substations, and industrial distribution networks.

Series	Typical Voltage	Typical Current	Application
KYN28	12 kV	630-3150 A	Industrial feeders, transformer incomers, utility distribution
KYN61	40.5 kV	1250-3150 A	Higher-voltage substations and grid interconnection
RMU	12-24 kV	630 A class	Compact distribution, box substations, ring networks

3. Low Voltage Switchgear

Low voltage switchgear distributes power from transformer secondary terminals to motors, MCCs, production lines, building services, UPS systems, and downstream distribution boards.

Series	Configuration	Typical Use
GCS	Withdrawable LV switchgear	Motor control centers and industrial plants requiring maintainability
GGD	Fixed LV distribution cabinet	General distribution where simple operation and cost control are priorities
MNS	Modular low-voltage assembly	Large industrial or infrastructure projects requiring modular layouts

4. Protection and Control Requirements

Switchgear must coordinate with transformer impedance, cable length, generator contribution, grid fault level, and downstream breaker settings. For MV systems, common relay functions include overcurrent, earth fault, transformer differential, under/over voltage, arc-flash detection, and communication to SCADA. For LV systems, ACB/MCCB selection should be coordinated with short-time delay, instantaneous trip, and downstream selectivity.

5. IEC Standards

• IEC 62271-1: Common specifications for high-voltage switchgear and controlgear.
• IEC 62271-100: AC circuit breaker requirements.
• IEC 62271-200: Metal-enclosed AC switchgear for rated voltages above 1 kV and up to 52 kV.
• IEC 61439: Low-voltage switchgear and controlgear assemblies.
• IEC 60909: Short-circuit current calculation for equipment rating verification.

6. RFQ Checklist

1. Single-line diagram and system voltage.
2. Incoming transformer or grid capacity.
3. Rated current and short-circuit level.
4. Number of feeders, breaker type, metering, and relay requirements.
5. Indoor/outdoor installation, IP rating, ambient temperature, altitude, and humidity.
6. Cable entry direction, busbar arrangement, interlocking, and communication protocol.
7. Required standards, inspection plan, test reports, and project documentation language.

Conclusion

The correct switchgear specification reduces downtime, improves operator safety, and prevents costly project changes during commissioning. For EPC and overseas projects, send the single-line diagram and fault level assumptions before finalizing the quotation so the switchgear lineup can be engineered correctly.