Switchgear Construction: Surge Protection and Protection Concepts
Why is the use of surge protection so important in modern control panel construction?
In the connected industrial sector, automated manufacturing processes rely on an uninterrupted supply of power and data. However, advancing miniaturization makes modern electronics vulnerable to electrical disturbances. The risks posed by transient overvoltages and lightning strikes are often underestimated—even though a single power surge can instantly destroy sensitive components.
Invisible Danger: Indirect Lightning Strikes & Switching Operations
The danger is by no means limited to direct lightning strikes. Far more often, dangerous voltage spikes are caused by indirect strikes within a radius of several kilometers or by internal switching operations. These spikes travel instantaneously through power and data lines all the way to the central switchgear and power distribution panels.
The Consequences of a System Failure
If a main or sub-distribution panel fails, it could lead to a complete production shutdown. In addition to costly repairs to PLCs or frequency converters, the resulting damage is usually even more severe:
Unplanned Downtime & Delivery Delays
Costs That Threaten Business Survival in Just-in-Time Supply Chains
Irreversible Data Loss and Increased Fire Risk
The Solution: A Multi-Stage Lightning and Surge Protection System
Reliable protection requires a systematic, multi-level protection concept based on the principle of lightning protection zones (LPZ). It combines external lightning protection with seamless internal surge protection—from high-performance combined SPDs at the utility connection point to fine-tuned equipment protection installed directly in front of the electrical equipment.
Which surge protective devices (SPDs) should be selected and installed?
In accordance with DIN VDE 0100-443 (Surge Protection) and DIN VDE 0100-534 (Selection and Installation of SPDs), the design of control cabinets requires a cascaded protection concept using SPD types 1, 2, and 3. The selection and arrangement in accordance with the standards depend on the feed-in point, the lightning protection class (LPC), the cable lengths, and the surge category (SC) of the electrical equipment.
Insulation Coordination in Switchgear Construction (Protection Level Concept)
Gradual Reduction of Voltage
Depending on their installation location, electrical equipment must have a specified rated surge voltage in accordance with DIN EN 60664-1 (VDE 0110-1):
Power supply point / transformer: up to 6 kV (OVC IV)
Permanent installation / UV: up to 4 kV (OVC III)
Connections & devices: up to 2.5 kV (OVC II)
Sensitive electronics (PLC): 1.5 kV (OVC I)
