Even minor voltage spikes or surges can damage or disrupt the performance of expensive electronic devices such as computers, phones, fax machines, TVs, and other household appliances. With the increasing use of sensitive computer chips, surge protection has become more important than ever. Installing a power surge protector is essential to safeguard your equipment from potential damage caused by electrical surges.
First, choosing the right current capacity
1) Understanding Lightning Protection Zones and Equipotential Bonding
Objects in the LPZOA area are at risk of direct lightning strikes. This means they may conduct lightning currents, and the electromagnetic field remains strong. In the LPZOB area, objects are unlikely to be struck directly, but the electromagnetic field is still strong. In LPZ1, no object is struck directly, and the current on conductors is reduced further compared to LPZOB. The electromagnetic field may also be attenuated depending on shielding measures. For LPZ2 (subsequent protection zone), additional protection is needed if further reduction of current or electromagnetic field is required. The selection of this zone depends on the system's specific requirements.
2) Selecting the Current Capacity for Building Power Systems
The current capacity should be selected based on the lightning protection level specified in GB50057-94 "Code for Lightning Protection Design of Buildings." The LPZOA area uses a 10/350μs waveform to discharge lightning energy effectively.
Second, selecting the maximum continuous operating voltage (Uc)
The Uc value of zinc oxide varistor surge arresters (like TPSB65, TPSC40) is crucial for their stable operation. When selecting this value, it’s important to consider not only standards but also normal grid fluctuations and possible fault voltages. According to IEC61643-2, in a TT AC power supply system, the highest continuous fault voltage between phase and ground can reach 1.5 times the nominal voltage (UN), which could be up to 330Vrms. In areas with unstable power, it's recommended to choose a TOWE surge protector with a Uc of 385Vrms.
In DC systems, there isn’t a fixed ratio between Uc and the normal operating voltage (Un), but it's typically between 1.5 and 2 times.
Third, considering residual voltage (Ures)
Lower residual voltage is generally better, but it's not the only factor to consider. Different products must specify the test current magnitude and waveform for meaningful comparison. Residual voltage is usually measured at 20KA (8/20μs). A lower residual voltage often means a lower Uc, which can lead to overvoltage issues in unstable environments. It's important to balance Uc and residual voltage, as both are critical for protection. From past experience, a residual voltage below 2kV (20KA, 8/20μs) is sufficient for most user equipment.
Fourth, choosing an alarm function
To monitor the status of the arrester, it's important to have an alarm system that alerts users when it's damaged. There are three options available for TOWE lightning protection devices: a sound and light alarm (AS) for manned environments, a remote signal alarm (S) for unattended settings, and a remote signal with voltage detection for advanced monitoring in unattended locations.
Fifth, designing a backup air switch for protection
To ensure electrical safety, any component connected in parallel to the power supply should be protected with a short-circuit device like an air switch or fuse. This prevents faults from causing damage or hazards.
Sixth, special design considerations for poor power environments – 3+1 structure
In areas with unstable power, using a 3+1 surge arrester is recommended. This configuration includes a varistor module between phase and neutral, and a discharge gap module between neutral and ground. Compared to traditional designs, the 3+1 structure offers better reliability. In TT systems, high grounding resistance can prevent fuses from tripping during faults. However, the 3+1 design ensures a low-impedance path, allowing the fuse to trip and isolate the arrester safely, even in poor grounding conditions.
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