Overvoltage protection with SPDs: Tips for protecting systems and equipment from surges

With increasing industrial automation, the number of products susceptible to interference is also growing. Technical systems are becoming more and more complex and contain devices that are getting smaller and more powerful and, due to their increasing functionality, also more vulnerable. For example, power supplies, such as the switching power supplies used in industrial systems, can dissipate the high pulse energy caused by surges only poorly or not at all. Many failures due to defective power supplies can be traced back to transient overvoltages.

• temporary disruption to operations / undefined system operation
• data or transfer errors, program crashes, erasure of memory contents
• destruction of hardware caused by electrical breakdown
• destruction of bonding wire connections or circuit paths
• in case of hardware breakdown: additional service costs, system downtime
• with smaller surges: negative influence on installed electronic components, premature ageing, shortened operational lifetime.

Protecting facilities against failures and avoiding potentially expensive interruptions to operations is essential. Effective protection is offered by a surge protection device, or SPD, a device designed to protect against voltage spikes.

• Based on varistors or gas-filled spark gaps, or a combination of both (optimal).
• Withstands the maximum discharge current of an 8/20 ìs pulse without being destroyed.
• If an overvoltage occurs, discharges the energy and reduces the maximum residual voltage to a defined protection level.

• Protection level is matched to the dielectric strength of the unit to be protected: coarse, medium or fine protection. Specifications according to IEC standard 60364: protection level of max. 2.5 kV for surge protection devices at the input of 230V or 400V networks.
• In networked systems, additional protection of data and control wiring.
• Protects the unit regardless of the overvoltage level: If the energy surge exceeds the discharge capacity of the protective element, the end system will still be protected.
• Equipped with an internal and an external disconnection device: in case of a fault, offers the best possible protection for connected electrical applications.
• Some models available with remote signalling for monitoring integration in modern networked industrial systems.

• Type 1 Lightning conductor: Depending on the design, used upstream of the meter or directly behind it, where the highest currents have to be discharged if lightning strikes directly.
• Type 2 Overvoltage protection: Used in the main or sub-distribution of the electrical installation; protects the downstream wiring and electrical applications by suppressing energy pulses as quickly as possible.
• Type 3 Overvoltage protection: Used in the immediate vicinity of sensitive electrical and electronic terminal equipment. Cuts the reduced overvoltage, already decreased by the Type 2 arrester, to a level acceptable for commercially available terminal equipment.
• Combination arresters: Cover several categories and are also available: Type 1+2 and Type 2+3 are also used on or very close to terminal equipment, while Type 1+2+3 unites all three categories in a single SPD.

At Schukat electronic, we offer a selection of SPDs from manufacturer Citel direct from stock. Citel develops overvoltage protection components such as gas-filled spark gaps, gas arresters and surge protection devices. With its test laboratories in France and China, surges of up to 100kA can be simulated, and products can be checked and tested accordingly.

The Schukat technical sales team is here to answer any questions you may have on the topic of power supplies.