MOV vs. SAD vs. GDT
When evaluating surge protection for your networked devices, its essential to choose the right product to do each individual job. There is more to surge protection than simply hooking up a device – in fact there are several different types of surge protection, each engineered with differing core components performing the “dirty work” of dissipating surges away from your critical devices. The three most commonly found core components are MOVs, SADs, and GDTs; most surge protectors are built around one of these three and are defined by the capabilities of that component. There are also hybrid, multi-stage models available that contain multiple components for better coverage.
Knowing the definitions and differences between these will help you choose the right surge protection solution for your critical systems.
Metal Oxide Varistors
Metal oxide varistors, or MOV, is the most commonly used technology for surge protection devices. This is most often found in the commonly available surge protection strips intended to protect consumer devices plugged into outlets. MOVs are robust surge protection components, capable of taking powerful surges initially, but they degrade over time. While cost-effective and easy to use, MOV-based products have other limitations (see SADs below) and are typically not the best choice for critical data and networked devices.
Silicone Avalanche Diodes
Silicone avalanche diodes, or SADs, are the most commonly used style of surge protection technology for data and networked devices. Unlike MOVs, they do not increase the capacitance of the circuit, allowing data to move freely along the network while still providing robust surge protection, which is essential for any networked device to prevent packet loss and throughput issues. SADs are extremely fast-reacting components, enabling quicker surge protection than an MOV, but are less robust, requiring less of a surge to self-sacrifice and necessitate replacement.
Gas Discharge Tubes
Gas discharge tubes, or GDTs, are traditionally the strongest surge protection component, ideal for protecting externally mounted devices that require lightning surge protection or other installations where massive surges are a possibility. They are also traditionally very small, allowing for easier installation on devices where space is limited. However, they are also the slowest reacting surge protection component, and as such are not ideal for fast travelling, sudden surges.
Hybrid surge protectors come in various configurations, but the most common configuration pairs an SAD with a GDT—allowing the fast response time of the SAD to compensate for the slower GDT that is able to take a much larger surge and divert it away from the network and its devices. Many of these components can be found in both modular and non-modular surge protectors, making it simpler for you to customize your solution to the exact needs of your system.
When choosing surge protection for your critical devices, take into account the core components of the surge protection you are installing. Hybrid designs allow you the best of all worlds, but may be higher in cost. While all of these components provide surge protection, it’s essential to ensure that they provide the kind of protection your devices need to function and be adequately defended from power events.