How to choose the best technology for surge protective devices
The era of networked electronic technology is driving a growing need for risk mitigation of all kinds. Since your organization has undoubtedly made a substantial investment in the various electronic devices that run on your network, it is of vital importance that you take the steps necessary to protect them from threats that could damage or destroy them. One of the most fundamental measures you should take is the deployment of surge protective devices (SPD) to shield your networked electronics from power surges and spikes, also known as voltage transients.
In evaluating and selecting surge protection, it is important to choose the best product for each individual job. It is not as simple as purchasing a single type of SPD and hooking one up to each device you have on the premises. In fact, there are numerous differing types of surge protection technology. The three most commonly found core components are Metal Oxide Varistors (MOV), Silicon Avalanche Diodes (SAD) and Gas Discharge Tubes (GDT). Each of these is engineered with differing core components to perform the “dirty work” of dissipating surges away from your critical devices. Most surge protectors are built around one of these three technologies, and each is typically defined by the capabilities of that component. There are also a hybrid, multi-stage models available that contain multiple components for better coverage.Knowing the definitions and differences between the three technologies will help you choose the right surge protection solution for your important networked electronic devices. Here is a more complete look at these technologies, along with some examples of the best applications for each.
Metal Oxide Varistors
A Metal Oxide Varistor, or MOV, is a bipolar, ceramic semiconductor device used in power supply circuits that are directly connected to and powered by the AC mains. The most commonly used technology for surge protection devices, MOVs are most often found in the widely available surge protection power strips intended to protect consumer devices plugged into outlets. This technology works by varying its resistance based on the voltage moving across it at any given moment. When a high current passes through an MOV, its resistance value decreases, diverting potentially destructive energy to earth ground, protecting vulnerable circuit components and preventing system damage.
This type of surge protection technology does have some shortfalls, particularly when you are considering it for commercial use. Metal oxide varistors cannot handle sustained overvoltage – they can only be used for short duration surge protection. Further, while MOVs are fairly sturdy components, capable of absorbing strong surges at the beginning of life, they do degrade over time. Eventually, they will no longer be able to perform their jobs and must be replaced.
Silicon Avalanche Diodes
Silicon Avalanche Diodes, or SADs, are the most commonly used surge protection technology for high-speed data transmission, low-voltage DC applications and networked devices. With a faster response time than MOVs, SADs are built to experience avalanche breakdown, a type of electric current multiplication that causes a sudden, swift increase in current, and thereby provides protection for the circuit to which it is connected.
In a typical diode, avalanche can cause catastrophic failure. However, since Silicon Avalanche Diodes are engineered to control avalanche, the diodes are able to tolerate the phenomenon and remain undamaged.
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 available. These function by providing a connection between the power line and a ground line, with an inert gas as the conductor between the two lines. When the line voltage is below a certain level, the gas does not conduct electricity. However, when there is a power surge or spike, the gas molecules will break into positive and negative ions. The now-ionized gas becomes an extremely effective conductor and begins passing the current to the ground line, diverting the surge away from the device it is protecting. After the surge passes, the ions recombine to become gas molecules.
GDTs have a number of advantages over other types of surge protection devices. Because of the robust shielding, they offer against very large surges, they are ideal for protecting externally mounted devices and other installations where lightning or other massive power events can be a possibility. In addition, they are typically very small, allowing for easier installation on devices where space is limited. However, on the negative side, they are also the slowest reacting surge protection component. For this reason, they are not ideal for fast traveling, sudden surges.
Hybrid Surge Protectors
Sometimes there is no single best technology choice to ensure your critical devices are protected – rather, the most robust protection can be provided by a combination of methods. In these instances, it is smart to consider a hybrid surge protector.
Hybrid surge protectors come in a number of different configurations. One of the most frequently used combinations is that of a Silicon Avalanche Diode and a Gas Discharge Tube. Pairing these two technologies leverages the advantages delivered by each one individually. While the SAD offers a faster response time, the GDT is able to take a much larger surge and divert it away from the network and all connected devices.
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. You will also find that 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.
While every type of technology mentioned here provides a level of surge protection, you should consider discussing your needs with a knowledgeable provider before making a purchase decision. In this way, you can be certain that you will be installing the right type and level of protection for your devices to function and be sufficiently shielded from adverse power events.
About the author: Michael Molinari has over 19 years’ experience in electrical sales and design, including surge protection and UPS battery backup systems. As Director of Marketing for DITEK, he is responsible for the company’s marketing and communications strategies, as well as overall branding and image. Learn more about DITEK at www.diteksurgeprotection.com.
