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Surge protectors and noise filters are both protective devices for the stability and lifespan of electronic devices.

Surge protectors and noise filters are both protective devices for the stability and lifespan of electronic devices , but their roles and methods of operation have distinct differences and complementary relationships.

Surge Protector

  • Role : Protects electronic devices from **transient high voltages (surges)** caused by lightning, power switching, etc.

  • How it works : When an overvoltage is detected, it absorbs it or diverts it to ground so it does not reach the device.

  • Application examples : Used to protect against lightning and power instability in homes, industrial facilities, and communication equipment.

Noise Filter

  • Role : Prevents malfunction of devices by removing **high frequency noise or electromagnetic interference (EMI)** contained in power lines.

  • How it works : It blocks unnecessary frequency components through a filter circuit and improves power quality.

  • Application examples : Used to prevent signal distortion in medical devices, audio equipment, precision control systems, etc.

Relevance

  • Complementary : Since noise filters are susceptible to surges, using them together with surge protectors can maximize electrical stability.

  • Integrated Products : Some advanced power protection devices combine surge protection and noise filtering functions , providing two types of protection in one device.

Simply put, a surge protector blocks “big shocks” and a noise filter removes “soft interference.” Using the two devices together can make your electronic devices much safer.

KS C IEC 61643-11 is a Korean industrial standard that specifies the requirements and test methods for **surge protective devices (SPDs)** connected to low-voltage power systems, and is consistent (IDT) with the international standard IEC 61643-11 . This standard defines the performance characteristics and test conditions of Class I, II, and III SPDs , but does not directly classify or describe **noise filters or isolating transformers** as Class III SPDs .

However, the connection is often mentioned in the following ways:

  • Class III SPDs are typically installed **at the final load (e.g. near electronic equipment)** and block relatively low energy surges.

  • Noise filters and isolating transformers are used together with Class III SPDs to provide complementary protection through high-frequency noise rejection and electrical isolation .

  • Some technical documentation or manufacturer materials consider them to be auxiliary devices corresponding to a Class III level of protection .

Official reference materials

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