Study On The Influence Of Multi-stage Surge Protector Selection And Layout On The Impulse Tolerance Of Electrical Equipment
If the combined voltage of the incoming SPD's Up voltage plus the induced voltage across its leads, as well as the reflected wave effect, is too high compared to the impulse withstand voltage of the remotely protected equipment, a second-stage SPD should be installed at the equipment. Its rated discharge current, In, should not be less than 3kA at 8/20μs. If the incoming SPD is no more than 10m from the protected equipment, and the combined voltage of the SPD's Up voltage plus the induced voltage across its leads is less than 80% of the equipment's Uchoc, a surge protective device installation is generally not necessary at the equipment.
If a distribution board is located between the surge protector terminals installed as described above, and if the combined voltage of the first-stage SPD's Up voltage plus the induced voltage across its leads is insufficient to protect the equipment within the distribution board, a second-stage SPD should be installed within the distribution board. Its rated discharge current, In, should not be less than 8/20μs. 5kA;
When surge protection device is installed at multiple locations on a line, the line length between a voltage-switching SPD and a voltage-limiting SPD should not be less than 10m, and the line length between voltage-limiting SPDs should not be less than 5m. For example, if the protected equipment is close to the power distribution center, additional conductors may be deliberately routed during line installation.
