Overvoltage protection for industrial production equipment

In modern manufacturing companies, a high degree of automation and sensitive electronic equipment make power supply stability a critical factor. One of the biggest threats – overvoltages – can cause costly damage, production downtime, and significant losses.

What is an overvoltage?

An overvoltage is a sudden and short-term increase in electrical voltage in the network that can seriously damage or completely destroy electronic devices. It can occur in various ways – from lightning strikes to power supply disturbances or switching on large loads in the electrical network.

An overvoltage is a sudden, short-term increase in electrical voltage in the network that can:

• damage or destroy electronic equipment;
• affect data transmission and control systems;
• reduce the lifecycle of equipment.

Main causes of overvoltage:

• Lightning discharges (direct or indirect);
• Switching of large motors or transformers;
• Power network interruptions and restoration;
• Static electricity or electrostatic discharges (ESD).

Lightning – an unpredictable but destructive threat

One of the most dangerous causes of overvoltage is lightning strikes. Even if lightning does not directly strike a building, a nearby discharge or a strike on power lines can cause massive voltage surges in the network, damaging all connected equipment within a fraction of a second. In industrial zones, where there are many metal structures and electrical connections, lightning-induced overvoltages can result in massive losses.

What consequences can overvoltages cause?

• Damage or destruction of expensive production equipment
• Production stoppages and downtime
• Loss of data in automated systems
• Increased maintenance and repair costs
• Insurance refusal if protection is not ensured

Protection system levels and products

1. Level 1 – Type 1 (T1) – primary protection. Type 1 overvoltage protection is the highest-level solution designed for direct lightning strikes and very strong impulses. It should be installed at the main power supply entry point, especially in sites with a lightning protection system (LPS).

What can Type 1 protection handle?

• Designed to discharge large lightning-induced currents – from 25 kA up to 100 kA (depending on the device)
• Can withstand a 10/350 µs waveform impulse corresponding to a lightning discharge
• Dissipates the lightning impulse directly to earth, preventing it from entering the network and damaging equipment

Level 2 – Type 2 (T2) – secondary protection. Type 2 devices are the most commonly used protection type, designed to suppress medium-level overvoltages in distribution boards and substations.

Where do these overvoltages occur?

• Indirect lightning effects (strikes on nearby power lines)
• Load switching (motor, transformer switching on/off)
• Voltage “reflections” in industrial zones with varying loads

What can Type 2 protection handle?

• Can discharge medium-level impulses – typically 5–40 kA
• Operates with an 8/20 µs waveform (switching and indirect lightning effects)
• Protects electrical consumers, cables, automation, and sub-equipment

Level 3 – Type 3 (T3) – local protection. Positioned closer to sensitive electronic devices (PLCs, HMIs, I/O modules, computers, sensors), which can be damaged even by small voltage spikes.

What can Type 3 protection handle?

• Protection against residual overvoltages that reach the end device
• Discharges impulses < 2.5 kA with voltage levels up to 1 kV
• Effective protection for precision and expensive control electronics

Combined solutions – Type 2+3 and signal protection
In addition to T1–T3 protection, modern equipment also requires protection for control circuits and data signals (e.g., 0–10V, 4–20 mA, Ethernet/PoE).

Where is additional protection used?

• Signal lines – analogue and digital inputs/outputs (PLC)
• 24V DC power circuits – for sensor systems, HMIs, relays
• Data transmission networks – Ethernet (Cat5e, Cat6), PoE, RS485, Modbus

Benefits of combined protection:

• Integrated protection in compact enclosures (less space and installation work)
• Compatibility with industrial power configurations (3+1, 2+0)
• Reduced voltage levels to < 55 V in signal circuits

How to choose the right protection combination?

• Assess the building location and risk of lightning strikes
• Determine whether a lightning protection system (LPS) is installed
• Measure the distance from the main entry point to sensitive equipment
• Combine T1 and T2 at the entry level, especially if external lightning protection is present
• Pay attention to earthing resistance and quality (below 10 Ω)
• Choose devices with remote signalling (remote contact) to SCADA
• Regularly inspect SPD status (many devices have status indicators)
• Consult a certified electrician or factory design engineer

SIA “ZTF Lāsma” offers overvoltage protection solutions from well-known brands such as Schneider Electric, Schrack Technik, and Seneca. The table below shows the main product series and codes according to their application.

Comparison

By using industrial-grade overvoltage protection solutions, it is possible to build an effective, three-level protection system that safeguards electrical equipment and infrastructure across different risk levels:

1. Type 1 – withstands direct lightning-induced impulses and safely discharges them to earth;
2. Type 2 – protects against commonly occurring medium-level overvoltages caused by network disturbances;
3. Type 3 – provides localised protection for sensitive electronic devices such as control systems, sensors, and computers.

This structured protection approach guarantees:

• long-term operational stability of the system,
• reduced risk of damage and maintenance costs,
• compliance with international safety standards (e.g., IEC 61643, IEC 62305),
• fulfilment of insurance requirements for critical infrastructure sites.