Conductor marking lights
Encyclopedia
Conductor marking lights are a particular type of non-standard aircraft warning lights
designed for overhead power lines.
A simple and cost effective solution to this problem is installing the marking lights directly on the wires.
Nevertheless there are significant technical difficulties to a low-cost extraction of power from a distribution system which carries high voltages and wide range AC current.
Moreover the warning system should not add to the existing power distribution lines the burden of additional cabling, with its potential serious isolation problems. These facts rule out the recourse to conventionally powered light sources.
The first approach takes advantage of the high electric potential gradient
between conductors, but a
strong enough capacitive coupling
is requested to allow capacitive extraction of the power required from the warning light. This means that long conductors must be suspended parallel to the line using glass/ceramic isolators: in fact several meters of suspended conductor are generally required, total length being inversely proportional to the line voltage.
The second approach is based on Faraday's law of induction
involving magnetic flux
flowing through a circuit which powers the warning light.
surrounding the power distribution wire and uses an electronic circuit integrated in a compact clamp-on warning light.
The operating principle is very simple; basically the circuit powering this type of warning light is based on Rogowski coil
principle and can be thought as a current transformer
.
This solution is usually intended for medium and high voltage lines up to 440 kV. However inductive coupling devices are able to work on any AC
at 50 Hz or 60 Hz, from 15 up to 2.000 Amps.
Aircraft warning lights
Aircraft warning lights are high-intensity lighting devices that are attached to tall structures and are used as collision avoidance measures. Such devices make structures more visible to passing aircraft and are usually used at night, although they may be used during the day as well...
designed for overhead power lines.
Background
Power distribution on overhead wires, often suspended to widely spaced masts, represents an almost invisible obstacle to low flying aircraft, requiring the installation of warning beacons on the masts themselves.A simple and cost effective solution to this problem is installing the marking lights directly on the wires.
Nevertheless there are significant technical difficulties to a low-cost extraction of power from a distribution system which carries high voltages and wide range AC current.
Moreover the warning system should not add to the existing power distribution lines the burden of additional cabling, with its potential serious isolation problems. These facts rule out the recourse to conventionally powered light sources.
Implementation principles
The ideal warning light must be able to power itself while clamped to a single wire of the line. Two approaches are, then, possible for facing this problem:- extracting energy from the Electric FieldElectric fieldIn physics, an electric field surrounds electrically charged particles and time-varying magnetic fields. The electric field depicts the force exerted on other electrically charged objects by the electrically charged particle the field is surrounding...
surrounding the power line; - extracting energy from the Magnetic FieldMagnetic fieldA magnetic field is a mathematical description of the magnetic influence of electric currents and magnetic materials. The magnetic field at any given point is specified by both a direction and a magnitude ; as such it is a vector field.Technically, a magnetic field is a pseudo vector;...
surrounding one of the power line wires.
The first approach takes advantage of the high electric potential gradient
Gradient
In vector calculus, the gradient of a scalar field is a vector field that points in the direction of the greatest rate of increase of the scalar field, and whose magnitude is the greatest rate of change....
between conductors, but a
strong enough capacitive coupling
Capacitive coupling
In electronics, capacitive coupling is the transfer of energy within an electrical network by means of the capacitance between circuit nodes. This coupling can have an intentional or accidental effect...
is requested to allow capacitive extraction of the power required from the warning light. This means that long conductors must be suspended parallel to the line using glass/ceramic isolators: in fact several meters of suspended conductor are generally required, total length being inversely proportional to the line voltage.
The second approach is based on Faraday's law of induction
Faraday's law of induction
Faraday's law of induction dates from the 1830s, and is a basic law of electromagnetism relating to the operating principles of transformers, inductors, and many types of electrical motors and generators...
involving magnetic flux
Magnetic flux
Magnetic flux , is a measure of the amount of magnetic B field passing through a given surface . The SI unit of magnetic flux is the weber...
flowing through a circuit which powers the warning light.
Inductive coupling device
This beacon is based on the second approach described in the previous paragraph: it's powered by magnetic fieldMagnetic field
A magnetic field is a mathematical description of the magnetic influence of electric currents and magnetic materials. The magnetic field at any given point is specified by both a direction and a magnitude ; as such it is a vector field.Technically, a magnetic field is a pseudo vector;...
surrounding the power distribution wire and uses an electronic circuit integrated in a compact clamp-on warning light.
The operating principle is very simple; basically the circuit powering this type of warning light is based on Rogowski coil
Rogowski coil
A Rogowski coil, named after Walter Rogowski, is an electrical device for measuring alternating current or high speed current pulses. It consists of a helical coil of wire with the lead from one end returning through the centre of the coil to the other end, so that both terminals are at the same...
principle and can be thought as a current transformer
Current transformer
In electrical engineering, a current transformer is used for measurement of electric currents. Current transformers, together with voltage transformers , are known as instrument transformers...
.
This solution is usually intended for medium and high voltage lines up to 440 kV. However inductive coupling devices are able to work on any AC
Alternating current
In alternating current the movement of electric charge periodically reverses direction. In direct current , the flow of electric charge is only in one direction....
at 50 Hz or 60 Hz, from 15 up to 2.000 Amps.