What is vibration and dance of power transmission lines and how to deal with them

Hello dear guests and subscribers of my channel. You've probably seen high voltage power lines and understand that large poles are designed to hang wires above the ground.

Directly near the supports, the wires are fixed quite rigidly, but in the spans between the supports, the wires can oscillate quite freely.

So, under certain weather conditions, extremely unpleasant effects can occur: dancing or vibration of wires, which can simply destroy the lines.

Today I want to tell you about these phenomena and how to deal with them in more detail.

What is vibration and dance

So, first, let's understand what is meant by dancing and vibrating wires.

The dance of wires is their vertical movement, the frequency of which lies within 0.2-2 Hz. In this case, the amplitude of such fluctuations can reach from 0.3 to 5 meters. And with significant spans of 500 meters, the dance can reach 14 meters.

Absolutely all classes of power transmission lines are subject to this phenomenon, but in lines with a voltage of 6-10 kV due to the fact that the distance between the wires is insignificant, this effect is neglected.

But the vibration of the wires is the same movement of the wires in a vertical plane, only their amplitude lies within a few centimeters. And their frequency ranges from 3 to 150 Hz.

So how does vibration differ from dancing

At its core, the vibration and dance of wires are one physical phenomenon. The only difference is that these phenomena have different oscillation frequencies. And vibration has a significantly lower vibration amplitude.

What causes these phenomena

There are three main factors that contribute to the manifestation of vibration and dance, namely:

• Wind. In fact, the most common and most dangerous cause of occurrence. This is because prolonged exposure can cause an increase in amplitude and frequency.

• Switching and related transients. When the voltage is turned on or a powerful load is connected, a jump in the electromagnetic field occurs. This sets the wires in motion.
• Various kinds of mechanical stress.

I want to emphasize that the switching of mechanical action is mainly of a one-time nature, which means that the resulting oscillations gradually begin to fade away on their own. Therefore, the main cause of the phenomenon is the effect of air flow.

Why dance and vibration of wires are dangerous

In fact, these two phenomena carry the following danger for power transmission lines:

1. Fluffing. This is damage to individual strands of wires or steel cables due to the loss of mechanical strength.
2. Phase-to-phase short circuit due to overlapping of the air gap. This factor occurs when the individual phases of the line vibrate with different amplitudes.
3. Twisting of wires, which also leads to a phase-to-phase short circuit.
4. Broken wires. It can occur both due to short circuit and due to mechanical breakage.

As you can see, all of the above factors lead to disruption of the normal operation of the power system, therefore it is quite logical that this phenomenon is being actively combated.

How to deal with dance and vibration of wires

So, in order to prevent such an undesirable phenomenon, specific measures have long been developed, which are detailed in RD 34.20.182-90. In particular, special devices are used to dampen the resulting vibrations and dances.

There are three types of vibration dampers, namely:

1. Loopback. They are mainly used on 6-10 kV lines and represent a flexible strut.
2. Spiral. Considered best for damping both low frequency and high frequency vibrations. But due to their high cost, they are rarely used.
3. Bridge. The design uses specialized weights, which transmit vibration from the wire and are also damped in them. Easy to install and operate.

As you can see, at first glance, a very simple power transmission line turns out to be a complex engineering structure. If you liked to learn something new and useful, then do not forget to rate the material with a like, a subscription and a comment. Thanks for reading to the end!