There’s no shortage of options when it comes to surge protection. It may be difficult to tell the difference among products and systems, and what type of surge protection device (SPD) is right for the application. Here are a few and notes to help sort what’s out there.
Key Takeaways
- Surge protectors defend equipment from short-duration voltage spikes, not long-term overvoltage or outages.
- Not all surge protectors are equal — specifications like clamping voltage, joule rating, and response time directly impact protection quality.
- Surge protectors degrade over time and may stop working without obvious failure, making status indicators and periodic replacement critical.
- Proper grounding and installation are just as important as the surge protector itself for effective energy diversion.
- RF and communications systems require specialized surge protectors that preserve signal integrity while handling high surge currents.
What Is a Surge Protector and Why Does It Matter?
A surge protector is a protective device designed to shield electrical and electronic equipment from sudden voltage spikes, also known as transient surges. These spikes can occur due to lightning strikes, utility grid switching, equipment startup, or nearby electrical faults. Even though these events last only microseconds, they can cause immediate or cumulative damage to sensitive components. Surge protectors work by detecting excess voltage and safely diverting it away from connected equipment, usually toward ground. In critical environments such as data centers, RF systems, industrial automation, and telecom infrastructure, surge protection is essential to prevent equipment failure, downtime, and costly repairs.
Key Surge Protector Specifications You Should Understand
Not all surge protectors offer the same level of protection, which is why understanding key specifications is important. Clamping voltage indicates the voltage level at which the protector activates—lower values mean faster protection. Surge current rating and joule rating describe how much energy the device can absorb before it degrades. Response time determines how quickly the protector reacts to a spike, often measured in nanoseconds. For RF and communication systems, additional parameters such as insertion loss, VSWR, and frequency range are critical to ensure that the protector does not degrade signal quality while providing effective surge suppression.
Why Surge Protectors Degrade Over Time
Surge protectors are not permanent devices; they wear out as they absorb repeated surge events. Each time a protector clamps excess voltage, its internal components such as MOVs, gas discharge tubes, or suppression diodes—experience stress. Over time, this stress reduces their effectiveness until they can no longer provide adequate protection. Unlike fuses, surge protectors often fail silently, meaning equipment may be unprotected without obvious signs. This is why many quality surge protectors include status indicators and why regular inspection and replacement are recommended, especially in environments prone to frequent electrical disturbances.
1. Technology Matters
Manufacturers utilize several different technologies in surge protection. Silicon avalanche suppressor diode (SASD) designs generally provide more reliable, long-lasting protection. Differentiating between Type 1, Type 2 and Type 3 SPDs is also significant, as described below.
2. MOV
Metal oxide varsitor (MOV) SPDs are non-linear variable resistors with semiconductor properties that were originally designed to protect electrical motor windings against wiring insulation breakdowns. There are two advantages associated with MOVs in regard to surge suppressors: They are inexpensive and they divert reasonably high values of transient current.
However, there are several downsides to MOV technology. Primarily, this type of SPD degrades significantly with use. Also, an MOV-based suppressor device cannot maintain a stable VPL as it conducts increasing current values, leading to potential equipment damage. Finally, varistors create “thermal runaway” conditions when their initial clamp points or VPLs are set too close to the nominal AC line voltage.
3. SASD
Compared to other suppression technologies, the advantages associated with the use of SASDs are numerous. Like the components within the sophisticated circuitry of modern electronic equipment that they are intended to protect, SASDs are true solid state semiconductors. Unlike MOVs, SASD-based surge suppression components do not degrade or cause thermal runaway conditions. As long as their energy dissipating capabilities are not exceeded, they will function perpetually.
Also, SASDs turn on faster than MOVs and respond more rapidly to transient overvoltages. A SASD-based transient suppressor can be reasonably expected to function with an in-circuit response time of five nanoseconds or less. Finally, quality SASD-based suppressor products maintain a stable VPL at any location upon the AC power system while conducting maximum current values.
4. Specifics are Key
Generally, the difference between Type 1, 2 and 3 SPDs revolves around the current rating of each. Type 1 SPDs have a higher rating and are typically used in service-sector and industrial buildings, and are engineered to protect against direct lightning strikes. Type 2 SPDs are the primary protection system for low-voltage installations. Type 3 SPDs have a low discharge capacity and are generally used as a supplementary solution for Type 2 applications.
In addition to the type of SPD, it is critical to address specific voltage requirements in the application for the best fit. Furthermore, ensuring the SPD meets all critical standards for performance, reliability and safety is elemental.
5. Filters Are Not Enough
A filter’s operational characteristics, by definition, are frequency dependent. It cannot adequately protect critical electronic loads from lightning-induced transient surges, nor can the filter protect against transients generated from non-lightning sources. It is designed to attenuate noise occurring within a band of repeating frequency ranges at relatively low voltage and current amplitudes.
Filtering technology (as well as built-in surge protection) typically is a good fit as a supplement to a high-quality SPD.
FAQs: Surge Protectors Explained
1. What does a surge protector actually protect against?
A: A surge protector guard’s equipment against transient voltage spikes caused by lightning, utility switching, or large electrical loads turning on and off. These spikes occur in microseconds and can permanently damage sensitive electronics if not diverted safely to ground.
2. Is a power strip the same as a surge protector?
A: No. A basic power strip only provides additional outlets. A surge protector includes internal protective components that clamp or divert excess voltage. Always verify surge ratings and protection indicators before assuming a device offers surge protection.
3. How do I know when a surge protector needs to be replaced?
A: Many surge protectors include an LED or status indicator labeled Protected. If this indicator turns off or changes state, the unit should be replaced. Even without visible signs, surge protectors should be replaced after major surge events or every few years in high-risk environments.
