How to choose the surge protective device(SPD)?
1) Power supply SPD installation location:
According to the regulations of relevant standards and the analysis of lightning accidents, all power lines that pass through different spaces must be installed with power SPDs when entering the space to eliminate overvoltage hazards that propagate along the power lines.
For a residential area or a factory, the different spaces through which the power line passes include:
1. The output cable of the distribution transformer enters the distribution room from the air to the distribution cabinet (the first space);
2. The power distribution cable from the power distribution room to each building goes from the air to the distribution box of each building, the cable lead-out point of the power distribution room and the cable lead-in point of the power distribution box (the second space);
3. Cables from the distribution box of each building to the distribution box on the floor (the third space);
4. Floor distribution box to each room distribution box (the fourth space).
5. If underground cable is used for power supply, SPD is not required.
2)SPD model selection and installation location in each space:
1. The output cable of the distribution transformer enters the distribution room from the air to the distribution cabinet (the first space)
Choose SPD products printed with Iimp and T1 logos and install them between the switch and load equipment of the switchboard in the power distribution cabinet.
Choose the Iimp value according to the local lightning frequency. If the lightning activity is frequent, you can choose a product with an Iimp value of 25kA. If there is less lightning activity, you can choose a product with a lower Iimp value.
2. The cables from the power distribution room to each building are routed from the air to the distribution box of each building, the cable lead-out point of the power distribution room and the cable lead-in point of the power distribution box (second space)
Choose SPD products printed with In and T2 logos and install them between the switch and load equipment of the switchboard in the distribution box, and the output cable end of the distribution cabinet.
SPD of 80kA~40kA can be selected for In .
3. Cables from the distribution box of each building to the distribution box on the floor (the third space)
Choose SPD products printed with In and T2 logos and install them between the switch of the switchboard and the load equipment in the distribution box.
SPD of 40kA~20kA can be selected for In.
4. Floor distribution box to each room distribution box (the fourth space)
Choose SPD products printed with In and T2 logos and install them between the switch of the switchboard and the load equipment.
SPD of 10kA can be selected for In.
5. If underground cable is used for power supply, SPD is not required. Connect the armor at the end of the cable to the grounding device.