How to Select Surge Protection Devices
When you select a surge protection device, it is important to pay attention to the parameter below,
a. The voltage should be ≤ Uc;
b. Up<maximum impulse withstands;
c. Different protectors should be selected according to various grounding system and protection mode.
According to different systems the surge arresters protected, different parameters should be pay attention to,
1. For surge arresters for protection of power supply systems, and photovoltaic surge arresters,
The operating voltage (Uc): The choice of operating voltage is vital when selecting a SPD. When choice the Uc value, besides meet relevant standard, the fluctuation of the network or the Max. continuous fault voltage also should be taken into consideration.
The protection level (Up): The Up value of the surge protection devices (surge arresters) is chosen according to and should be less than the impulse withstanding voltage of the equipment to be lightning surge protected. But it does not mean that the lower of the Up, the better of the surge protection devices (surge arresters, SPD) protection effect. Usually for the equipment connected to the network of 220V/380V, its withstanding impulse voltage can meet the requirement of 2000-2500V. So the SPD with Up<2500V can protect the equipment efficiently.
The alarm indicator : In order to monitor the operating condition of the surge protectors, when surge protectors damaged, the user should know it and change the damaged surge protectors module immediately. In order to realize the monitoring function, it should chose the surge protectors with indicator.
Choice of the associated switching element: All surge protection devices (surge arresters, SPD) are fitted with a built-in thermal disconnector. However, they must be equipped with an upstream protection element for protection against short-circuit currents.
2. For surge arresters for protection of signal systems, the parameters below,
Maximum operating voltage: The maximum operating voltage must be selected according to the rated voltage of data line, which is an essential parameter for an appropriate signal surge protection devices (surge arresters, SPD) selection.
But there is no standard in practical application. The maximum operating voltage of the signal surge protection devices (surge arresters, SPD) must be 1.2 times of the data line rated voltage.
Transmission frequency: Different communication system has different data transmission speed, when signal surge protection devices (surge arresters, SPD) installed on the data line, the transmission speed carried by the data line must be not less than the transmission speed of the communication system, otherwise, it will cause the signal interrupt or error, which influences the ordinary working of the communication system.
Insertion loss: When surge protection devices (SPD) is installed on the signal line, there is some insertion loss due to the influence of the additional capacitance in the case of high frequency. The insertion loss should not over take the value of the standard stipulated in the choice of the signal surge protection devices (SPD).
Connector type: The signal surge protection devices (surge arresters, SPD) is installed in the line in series. In order to match the impedance and keep minimum contact resistance, the connector must be selected the same type as the data line. The RJ and SD connector must be installed in line-to-line match, and coaxial connector should. Be installed in Female to male match.
When selecting antenna surge protection devices , besides the above mentioned parameters, the following parameter
also should be taken into consideration,
VRSWR should be: <1.2 or meet the relevant standard;
Working frequency: within the scope of radio frequency;
Wave resistance: the wave resistance of coaxial surge protection devices must consist with that of cable.
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