|A well known object
In the area around Rotterdam transmission line towers are a standard feature of the landscape.
There are several power-stations and switching stations in the area (Dordrecht, Maasvlakte, Krimpen a/d IJssel) and a lot of heavy industry (Nedstaal, Aluchemie).
The Dutch landscape is flat and they stand out nicely. They soar to amazing heights where the wires cross the river.
|Useful for urban adventure ?
Access looks easy at first sight. Becuse of the high maintenance needs these towers have always a "user-friendly" acces route. Some transmission line towers have ladders running inside their iron sheleton. Others have spikes running along one of the corners.
But in fact they are too dangerous to climb. It's also illegal and possibly lethal.
For some people they are attractive targets. Even for "normal" people. I've asked around in my circle of acquaintances and see what I got:
My boss described it very graphically, so imagine the following situation:
After this discovery they made plans to make a cable car from an old bicycle wheel and to cross the river hanging from the top wire. But they never put it into practice.
It seems that people grow out of this as they get older. Usually they turn to other nerve-wrecking activities. My choir-colleague became a professional photographer. And my boss became a network manager.
The brother of a colleague of mine has climbed transmission line towers and building cranes. I exchanged some short e-mails with him and talked to him over the phone. He acted as if it wasn't such a big deal. Let me quote him:
Looking up at the 110kV transmission line tower near Geleen. On the right you see the backside of a small sign. Usually these say "Mortal danger".
Looking from the side. The small arrows and the numbers show the different viewing directions. You can recognize them in the following pictures. Also notice the spikes along one of the corners leading all the way up.
Looking at the next mast form the top (view number 4). The wire you see is the top (zero, lightning-conductor) cable. You also get a nice view of the undulating countryside around Geleen. It's in Limburg, the southernmost province of The Netherlands.
Looking down from the center (view number 1). You can barely see Ed's brother Ton and his bicycle standing in the grass below. Ed was 18 at the time and Ton was 16. Their mother didn't really approve these activities.
Looking towards the center from the end of the top boom (view number 3). Notice the spikes again.
And finally a look down along the center. It really is high!
The official advice of the electricity company is: DON'T CLIMB THEM. But I wanted a more specific decription of the dangers and I visited the library of the Ministry of Social Affairs. This library has a lot of safety literature. I give you a quick overview of what I found. I cannot guarantee the accuracy however! Correct me if I'm wrong please. The firemen's and policemen's guidelines say: Stay away from live wires. Keep a minimum distance of 5 to 10 meters. But even more detailed instructions exist.
The "basic-distance" is the theoretical safe distance from a live wire. However if you're climbing or working in a transmission tower you cannot control your distance from the wires very precisely. Also the tower and the wires are swinging in the wind.
So in these situations you have to maintain the minimal "boundary distance" from the wires. If you have tools in your hands or if you carry things you have to look out for the extra "reach" this gives you - and for the added exposure.
If you climb up using a ladder you should not add just 1 m to the "basic distance", but 1 ,35 meters. If you use the spikes ("klimpennen") you have to add 1,60 m. So then the boundary distance is even larger than indicated in the table below.
Source: Notitie ter toelichting van het aspect "veilige afstand" bij de werkzaamheden in de hoogspanningsaanleg, Oktober 1987, N.V. KEMA / VDEN
|Nominal voltage||Maximum voltage||Basic distance||Boundary distance|
|50 kV||72,5 kV||0,70 m||1,70 m|
|110 kV||123 kV||1,20 m||2,20 m|
|150 kV||170 kV||1,60 m||2,60 m|
|220 kV||245 kV||2,60 m||3,60 m|
|380 kV||420 kv||3,60 m||4,60 m|
You don't notice that you're too close until it's too late.
People have got killed even by touching cables that were NOT carrying current. However the current in neighboring cables produced an induction current in the unused cable. These induction voltages can get as high as 10 kV. High enough to kill.
Less people get killed by electrocution than by falling from the tower. The towers can be anywhere between 40 m to 160 m high. Falls are caused by mis-stepping, slipping, tripping over something, becoming sick, getting a non-lethal electric shock, being hit by a dropped object. The conclusion is that you have to be secured to the tower at any time. You have to be secured if you work higher than 2,5 meters.
Never use a harness that is secured only around the chest. This can cause a painful death after hanging only 5 minutes. Allways use a harness that supports your weight in the hip-area.
Most of the lethal accidents occur on the descent from the tower. Several "human factors" combine to increase the danger:
BTW: This also applies to rock-climbing and alpine climbing.
20% of all accidents is due to breakage of the support
20% are due to mechanical instabilities of the support
30% are due to the worker unclipping his harness from the support, then changing his position while being unsecured
People over 40 years of age suffer significantly less accidents than younger people. Are they more careful? Or do they move to less risky jobs? There is not enough data to support either hypothesis.
Proximity-detectors for "life" power-cables exist but they cannot tell you if you'e still within a safe distance from a cable.
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© 1999 Ed Stevenhagen, Petr Kazil - 19 April 1999