How do pilots see transmission lines during night time?

In our previous post, we have read that what are aerial marker balls? Basically these colourful balls are installed on the transmission lines and communication overhead lines at some remote locations to make them visible to the low flying aircrafts. During day time, they are easily visible to the pilots. But, How do pilots see transmission lines during night time?

Before I give you the answer of the above question, I request you to first read about Aerial marker balls, if you haven’t yet. Click here

Generally, aircrafts and helicopters tend to fly in day time, but sometimes they have to fly during night time also. In some locations like, hilly areas, Valleys, Rivers, highways and Runways. Aircrafts tend to fly at low altitudes and it becomes very difficult for pilots to notice Transmission and communication wires during night time.

how do pilot see transmission lines during night

To make these wires visible to pilots, Illuminated lightning balls or Balisor are used on the transmission lines. These are also known as Aircraft Warning lights. Now, we will read about these Aircraft warning lights in detail.

What is Balisor?

Balisor is a system of illuminated Beacons for high voltage power lines using a cold-cathode low pressure neon lamp used as Air craft warning light during night time.

During the day time, brightly coloured balls are placed along the length of the cables are sufficient. But, during night Lightning is necessary. These Illuminated beacons provide this light by glowing red. Red is the standard colour used in aviation for warning beacons.

cold cathode neon lamp Balisor

Now, one question might came in your mind that How these illuminated beacons glow on such wires which are very high from ground? How their maintenance is done? Lets discuss the working principle of Balisor.

Working principle of Balisor

It obtains a power supply directly from the high-voltage cable on which it is mounted. As we know that it is difficult to obtain a very small amount of energy from a line which transports an enormous amount. Hence, its working principle is very interesting because it uses a phenomenon which is usually considered as Weakness.

As we know that, each high voltage cable creates an electric field around itself. This thing is considered as weakness but in the case of Balisor it helps to glow beacons.

A conductor is placed parallel to the High voltage line. As, there is already an electric field  present due to high voltage cable, so it will create a potential difference between high voltage cable and newly placed conductor. However, this conductor is insulated from the main cable.

In series with the conductor, a cold cathode low pressure neon lamp is placed as you can see in the picture below.

The conductor and main cable have some potential difference between them, so they will behave like a capacitor having air gap as a dielectric medium. (see below fig.). This potential difference is sufficient to discharge the Neon lamp.

schematic diagram for Balisor

The beacon glows red which can be clearly seen by the pilots during night to avoid any loss of life and infrastructure.

However, this system will not work when the lines is switched off because there will be no electric field and hence no potential difference to discharge the lamp.

Features of Balisor

It is a combination of cold cathode low pressure neon lamp and Capacitor charged conductor. These are installed with the help of Insulators on the high voltage cable.

They are installed at the range of every 70m on the runways and every 105m on the other places like hilly areas, river etc.

These Balisor or illuminated lightning balls has a life span of 15 to 20 years.

Advantages and Disadvantages

  • Reliable and Robust beacon.
  • Very economical.
  • Long life of around 15-20 years.
  • Will not work when line is switch off.
  • Will not work on HVDC power lines.

So, I hope that now you got the answer of this question, How do pilots see transmission lines during night time?

You can watch our video for better understanding.

You can also take quiz on various subjects of electrical engineering like power system, electrical machines etc. For quiz and test click here

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