air x

2»

Comments

  • MisterBMisterB Solar Expert Posts: 156 ✭✭✭✭✭
    Re: air x

    Yeah, in 1995 I spent about a week in Stockholm and our Swedish hosts gave us a car tour of their neighborhood and I asked why every house had a huge statue-- usually some kind of cherub holding a big bronze globe in it's hands--in it's front yard and the answer was lightning protection. In the summer, Stockholm has massive thunderstorms.

    I read about the theory of it years later but I can't remember where.
  • Truth SquadTruth Squad Solar Expert Posts: 126 ✭✭
    Re: air x

    I hate to burst some bubbles, but I've seen several Airs that were struck by lightning. It enters through the blade tip, which is taller than the tower after all. It takes out the blades, circuit, and face bearings. Not cheap repairs.
  • peterakopeterako Solar Expert Posts: 144 ✭✭
    Re: air x

    I Have a whisper 200 running after several modifications. it's hit around 4 to 7 times a year. By proper grounding and protection on the generator cables i do not demage the electronics. i see damage on the bronze swing bushing. If not diconnected on time other dicharges on the telephone network in the surounding, burns out my ADSL modem.

    Greetings from Greece
  • MisterBMisterB Solar Expert Posts: 156 ✭✭✭✭✭
    Re: air x
    I hate to burst some bubbles, but I've seen several Airs that were struck by lightning. It enters through the blade tip, which is taller than the tower after all. It takes out the blades, circuit, and face bearings. Not cheap repairs.

    I've always considered the Airs poor design and most of the ones around here are poorly installed as well. There is always a risk of lightning but if you do your grounding properly, it is at least minimized and possible strikes are diverted to where they do the least damage--electricity always flows through the path of least resistance and if there is a large shunt to ground from the tower, that is where it is going to go.

    And electrostatic energy that can damage electronic circuits doesn't always reach to point of a lightning strike. Putting the control circuits on the windgen itself is exrtemely poor design. They could be damaged by a static discharge from the weather that passes unnoticed until the controller fails and starts to overcharge or not charge batteries at all. Not that an Air X at 20-30 feet high is likely to produce enough energy to fry a battery bank.
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: air x

    side comment-
    even if they had a better design and the thing gets a proper grounding it can be induced into it from your wiring. picture this if you would, you have a turbine on a tower and the tower has a proper ground wire going down to an 8ft rod. your wiring also is coming down that tower and it is parallel to the tower. this causes an induced voltage to appear on all wires parallel to that tower. this has been a cause of radio equipment blowing out too and all of the wires need to be addressed to dissipate that potential before it reaches any circuitry be it in a turbine or in a house.
  • MisterBMisterB Solar Expert Posts: 156 ✭✭✭✭✭
    Re: air x
    niel wrote: »
    side comment-
    picture this if you would, you have a turbine on a tower and the tower has a proper ground wire going down to an 8ft rod. your wiring also is coming down that tower and it is parallel to the tower. this causes an induced voltage to appear on all wires parallel to that tower. this has been a cause of radio equipment blowing out too and all of the wires need to be addressed to dissipate that potential before it reaches any circuitry be it in a turbine or in a house.

    My experience with my wind turbine in this situation is that this is not a problem as long as the circuit is connected. The only time I had a problem was when I took the turbine down and left the cables on the tower in an open circuit. If the turbine is connected, there is a path to ground through all wires even if there is is electrical resistance in the the path. If there is an isolated cable on the tower, it acts as a capacitor and can accumulate a charge relative to the tower and other wires. Another thing to consider is that a wind turbine alternator is a very simple and rugged piece of equipment while a radio transmiter is not. A circuit board designed to work on say 100-500 milleamperes of current is not going to withstand the same electrical forces as an alternator wound to produce 20-100 amperes or more of current. That is why it is bad design to place electronic control circuits on the turbine. If the turbine consists of just an alternator, it is going to take a lot more electrical force to damage it. The controller on my Windseeker 250 was dead even before I got it while the alternator worked on without a controller for almost 20 years.
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: air x

    granted electronics are more sensitive to blowout and connecting may help dissipate a small charge that develops, but the point is it can develop high enough charges to blow out the alternator on the one side of the circuit and the electronics on the other side of the circuit inside the house as well unless it is dealt with. do not assume because radio equipment is more sensitive that you are safe from it.
  • MisterBMisterB Solar Expert Posts: 156 ✭✭✭✭✭
    Re: air x

    I don't take anything for granted--especially with a new wind generator with 3 phase coming from the generator instead of DC. A lightning storm always makes me nervous and I shut of the wind generator and my inverters when one approaches and I installed a 3 phase switch box with a custom brake switch I made on the base of the tower so I can isolate the tower and brake the wind generator during the summer stormy period when I least need the energy or if I'm going to be away for an extended period of time.
  • dwhdwh Solar Expert Posts: 1,341 ✭✭✭
    Re: air x

    Addendum to the lightning discussion:

    In reviewing the TLG page the other day, I noticed that he has a page about tower grounding in his Tips & Tricks section:

    http://www.tlgwindpower.com/grounding.htm
  • MisterBMisterB Solar Expert Posts: 156 ✭✭✭✭✭
    Re: air x

    Reading and posting on this forum has caused me to think a bit about my grounding system and reflect on why I, with the highest object in the neighborhood, have been so lucky in the last 20 years with lightning and some of my much lower neighbors have not. I have downloaded some of the white papers on lightning and grounding and here is something from one about grounding techniques

    Grounding Techniques
    The NEC allows a single-point grounding system to be connected to the earth in seven different ways.
    The two most common (described in detail below) are rod and pipe electrodes and ring ground. The
    other legal, but much less prevalent are:
    • Concrete-encased electrode (metal bars encased in concrete, buried in the earth


    The base of my tower consists of 3 11 1/2 inch diameter steel pipes set 3 feet into the earth in concrete. That is a lot more surface area than a typical grounding rod and I lay 3 sections of copper pipe of the same diameter as a grounding rod along side the steel pipes and tried to position them so they would be at the edge of the concrete and touch the earth and concrete at the same time. The legs of the tower are spaced 10 feet apart in a triangle. Here is a bit from another white paper about grounding rods and ground saturation:

    Ground Rod Theory Installation
    Ground Saturation
    The statement that rods should have a separation, “greater than the sum of their lengths apart,” originates
    from theory, and the fact almost all ground rods will saturate the soil to which they connect. A ground
    rod connects to localized, irregularly sized, three-dimensional electrical clumps. Depending on the soil
    make-up (layering, etc.), the volume of earth a ground rod can dump charge into can be generalized as
    the radius of a circle equal to the length of the rod at the circle’s center. This is known as the sphere of
    influence of the rod. The sum of the driven depths of two rods should be, theoretiin homogeneous soil,
    the closest that ground rods can be placed. Anything closer will cause the soil (clumps) connected in
    common to saturate even faster.


    At 3 feet down, the minimum separation of the grounding rods is 6 feet and I am 4 feet over that.

    I went out this morning with an ohm meter and checked continuity. The entire tower is made of metal and bolted to the base and a continuity check confirmed that all parts of the tower are a dead short to each other and the connection to all the bare copper wire I buried is also a dead short which is bonded at the house to the battery negative and the AC ground though both my inverters. When I unbonded the copper pipes I read around 2k ohms from 2 to the tower and 20k ohms on the third

    The conclusion is that my tower base is an active part of the single point grounding system and the tower itself is one big grounded object which includes the chasis of the wind generator which is bolted to the tower.

    And the conditions for the grounding system in the TLG page are vastly different than mine. There is no water table here really. There is some moisture in the soil but at times the soil is very dry and there might be an aquafer somewhere beneath hundreds of feet of basalt but drilling a well around here is extremely expensive and no results guaranteed.
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: air x

    i am having some difficulty picturing how you describe your ground setup to be. if you are relying on pipes in concrete to make a good ground this won't be the case. i do know they allow this in cases where there isn't a better way of going about it like for skyscrapers. any dissimilar metals touching such as copper to steel will start galvanic reactions and cause corrosion. this will create a high resistance point sooner or later. a good way to join dissimilar metals can be using stainless steel as this will not react on differing metals.

    as to towers, it is advisable to ground each leg of a tower to its own copper ground rod in the soil with at least #6 bare copper wire and not with the ground rod or wire in concrete, which is a resistance to the soil around it, and intertie the rods with at least #6 buried in the soil. although the nec wouldn't be as meticulous about much of this, it is good practice and you can even take it one step further by starting each ground wire up at the turbine with binding the ground wire with proper connections on each tower section on their way down until they are at the bottom section where they shall go out towards their prospective ground rods.

    in dry areas there are other methods that can also be employed such as large ground screens or even longer and more numerous rods spaced out even farther and one could even use multiple methods to achieve a better ground.
Sign In or Register to comment.