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Thread: Lightning Point of Injection to Transmission system

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    Lightning Point of Injection to Transmission system

    How does lightning really hit the transmission lines? Does it hit initially hit a single wire then spread it from there? But won't the wire melt. Or does lightning first strike the soil and it goes up to the transmission lines?


    So the primary reason poles are grounded is for lightning strike to dissipate the energy into ground? What if a pole is not grounded. Would it damage the insulation inside the transformers? Has this actually happened elsewhere?

    Please give me examples or incidents of transmission lines damages from lightning with and without grounding. Thanks.

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    You really love the simple easy to answer questions, don't you?

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    Quote Originally Posted by GoldDigger View Post
    You really love the simple easy to answer questions, don't you?
    It's not that easy. I'm looking for actual experiences of lightning strike to power lines.. like what did you see?

    Did you see direct lightning strike to the transformers?

    My utility pole nearby my house has insufficient grounding. If a thief steals the pole ground rod.. and it's floating (let's say all other grounding lines not functioning property). And lightning hit it.. what would happen to the transformer in the pole and where would the energy dissipate.. inside the house?

    But what is usually the lightning point of injection? How do they estimate the injection current in Surge Protection Device?

    Many are not sure to these answers hence it's not as easy question.

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    Lightning is not a thing sent down by Thore!
    It’s mearly the arc created between two large electrical charges.

    We need to stop thinking of it as some mythical bullet. And just accept that it is a very complex event with enormous voltage/current/high frequency elements that is extremely difficult to control or expect consistent results.

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    It seems that solidly-grounded systems might actually suffer greater damage than floating systems, but lightning isn't really consistent enough to generalize like that.
    Code references based on 2005 NEC
    Larry B. Fine
    Master Electrician
    Electrical Contractor
    Richmond, VA

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    Quote Originally Posted by tersh View Post
    How does lightning really hit the transmission lines? Does it hit initially hit a single wire then spread it from there? But won't the wire melt. Or does lightning first strike the soil and it goes up to the transmission lines?


    So the primary reason poles are grounded is for lightning strike to dissipate the energy into ground? What if a pole is not grounded. Would it damage the insulation inside the transformers? Has this actually happened elsewhere?

    Please give me examples or incidents of transmission lines damages from lightning with and without grounding. Thanks.
    It can hit various ways. There is no single mechanism.

    Small wire might melt but there is usually not enough energy in the strike itself to melt the wire. The follow current from the power system through an established arc has enough energy to cause more damage so we cut the power to clear the arc then restore power (very quickly).

    The insulation in the transformer is protected by arresters. Imagine a 1,000,000 volt strike/induced voltage. The wire is at 1,000,000 volts. The arrester shunts around the transformer so there is a drop across the arrester and transformer winding of 30,000 volts, just to pick a number. So the top of the transformer with the wire is at 1,000,000 volts and the bottom of the transformer/ground at 1,000,000 - 30,000 or 970,000 volts. The transformer never sees the full voltage if properly protected. It only sees 30,000 volts for this example.

    One reason to ground is to dissipate lightning into the earth.

    If the transformer were not grounded, the lighting would find the next closest path to earth. The arrester still clamps the voltage across the winding.
    BB+/BB=?

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    Quote Originally Posted by mivey View Post
    It can hit various ways. There is no single mechanism.

    Small wire might melt but there is usually not enough energy in the strike itself to melt the wire. The follow current from the power system through an established arc has enough energy to cause more damage so we cut the power to clear the arc then restore power (very quickly).

    The insulation in the transformer is protected by arresters. Imagine a 1,000,000 volt strike/induced voltage. The wire is at 1,000,000 volts. The arrester shunts around the transformer so there is a drop across the arrester and transformer winding of 30,000 volts, just to pick a number. So the top of the transformer with the wire is at 1,000,000 volts and the bottom of the transformer/ground at 1,000,000 - 30,000 or 970,000 volts. The transformer never sees the full voltage if properly protected. It only sees 30,000 volts for this example.

    One reason to ground is to dissipate lightning into the earth.

    If the transformer were not grounded, the lighting would find the next closest path to earth. The arrester still clamps the voltage across the winding.
    In studies made anywhere. How often does lightning:

    1. Hit the primary wires
    2. Hit the secondary wires
    3. Hit the transformer itself
    4. Hit the pole itself
    5. Hit the ground rod
    6. Lightning inducing EMP to hit the entire primary and secondary, does this occur?

    And when it hits the primary or secondary. Does it hit per phase, or simultaneously all phases?

    If the poles are not grounded. Can the lightning energy goes into the homes instead and destroy the equipments?


    What are the best references for any in depth studies of lightning effects on the power grid?

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    Quote Originally Posted by tersh View Post
    In studies made anywhere. How often does lightning:

    1. Hit the primary wires
    2. Hit the secondary wires
    3. Hit the transformer itself
    4. Hit the pole itself
    5. Hit the ground rod
    6. Lightning inducing EMP to hit the entire primary and secondary, does this occur?

    And when it hits the primary or secondary. Does it hit per phase, or simultaneously all phases?

    If the poles are not grounded. Can the lightning energy goes into the homes instead and destroy the equipments?


    What are the best references for any in depth studies of lightning effects on the power grid?
    How often IDK, but all those things you mentioned likely do happen. Every event has it's own conditions that lead to the results. Voltage level pre-strike and resistances of potential current paths is going to dictate where and how much current flows.

    Direct strike may be at an object near your home, you may still see damages in your home as a result of rise in voltage along a path between the main strike and your home.

    Whether or not current flows on one phase, multiple phases, primary, secondary, etc. all depends on current paths and overall impedance of those paths at that instant in time. Each path involved will carry a different level of current depending on how much voltage is across the path and the impedance of the path.
    I live for today, I'm just a day behind.

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