Tips to protect your equipment from Lightning surge.
This is my personal opinion getting from basic information to protect equipment from lightning surge.
Home /Concept /CounterMeasureThink about lightning protection
There is No 100% sure ways to protect
equipment from lighting surge. On the other hand, you may have serious damage by it.
・Understand that there is No 100% perfect method for the protection from lightning surge.
*You may have bigger lightning than ever before and have more frequently and bigger lightning.
・Size, frequency and Area of lightning
*Check IEC and Meteorological Agency in your country about of them.
・Understand feature of lightning rod and SPD.
*Lightning rod protects buildings but not equipment in them and SPD protects equipment.
・Select equipment for protection
*Select important equipment,
not noly price, but also key equipment on your Fabs to protect from lighting surge.
・Check Drwaings whether there are some indication about protection of equipment from lightning surge and ask designers of facilities.
*Description of the protection may be the same even importance or size of facilities are different. Check requirments whether those are too much requirments or Not.
・Cost and Performace
*Select equipment for protection. Huge money is required if you try to protect ALL equipment in a facility.Think about
damage when you have lightning and installation cost. We recomennd you take countermeasures based on IEC procedures.
・In the case of No description about SPD on drwaings, we recomend you install SPD following IEC standards.
Point of Striking of Lightning
Why breakdown happens
Lightning surge creates high voltage which is the cause of dieelectric breakdown. Unit of lightning surge is "kA" and amount of it will be 100kA or more sometimes. It is not realistic to consume the current to change thermal using resistors or so. Going through the surge current to low potential area, such as earth using SPD(Surge Protective Device) is one of common methods.
Impedance of SPD is Nomally High, but changes to Low impedance when suge current comes. Surge current goes to low potential area and equipment will be saved from dielectric breakdonw by the lightning surge.
Typical Devices are:
Gap：
Discharge current when voltage between the electrode higher than designed volatege.
Varistor：
Impedace becomes rapidly low, in case of high voltage difference between terminals of the device and surge currnet goes through it.
Ziner Diode：
Voltage is controlled desined voltage of the device.
It can not go through high amount of current and use for SPD signal lines.
Equipotential bodding
Surge current
SPD by-pass surge current
Many wires, such as power, signal and earth are connectd to equipment. Surge current has chances to goes into from line to line and it may cause of dielectric breakdown.
Reducing the voltage difference is called to have "Equipotential bonding".
Using big wire to connect earth bar is one of it. Unfortunately, we can not directly connect wire to power, signal lines and earth lines. It is good iead to install SPD for this purpose. SPD is normally high impedance between the earth and No affection for them, but becomes low impedance when surge current comes and make equipotantial condition.
Again contents in this Web site is my Personal Opnion. I did my best for the contents of this site, but may have some mistakes. We applogize if such things happen. Please remember that we will Not Take Any Resposibilties, even if you take countermeasures for lighting surge following on this contents and have any damage directly on your equipment and/or some other seconday damages.Please do any lightning protection based on your own resposibilty.