Wave Trap Working Function & Purpose of Line Trap:
Wave trap is used to create a high impedance to the carrier wave high-frequency communication entering into unwanted destinations typically substation.
Carrier wave communication uses up to 150kHz to 800kHz frequency to send all the communication. These high-frequency damages the power system components which are designed to operate 50 or 60 Hz. Wave traps are also called line traps.
It consists of an inductor coil which is connected in series with the high voltage power system. Please refer to the figure.
Construction of Wave trap circuits:
Wave trap circuit consists of three major components such as..
- Main Coil
- Tuning Device
- Protective Device
Main coil:
Main Coil is nothing but an outer part of the wave trap circuits and which is made from the standard aluminum cable.
If the application of more than one layer is necessary, the separation between layers is required to provide a cooling duct between them to avoid overheating.
The cooling duct is created with spacer bars made out of epoxy resin and fiberglass. The coil carries rated continuous power frequency currents, therefore this is the power inductor in this system. It provides a low impedance path for the electricity flow.
The total current carrying capacity of the transmission system will be calculated, and the trap coil is designed according to that.
That’s why the coil becomes a bigger size as you can see in High voltage transmission.
When the frequency increases, the inductive reactance will get increases.
That’s why it creates high impedance for high-frequency signal and low impedance for low-frequency signal. This unit prevents the high-frequency carrier signal from entering the power circuits.
Coupling Capacitor:
A coupling capacitor is used to receive a high-frequency communication signal. As the capacitor principle of capacitor creates low impedance for a high-frequency signal.
As the frequency increases, the impedance value decreases and the frequency decreases the impedance increases.
Tuning Device of Wave Trap:
The next major component is the tuning device. This device is securely installed inside the main coil.
It adjusts blocking frequency or bandwidth and consists of coils, capacitors, and resistors.
The tuning device is connected in parallel with the main and protective device. It provides blocking impedance over a specified frequency range.
It can be sing band tuned or multiple bands. The tuning circuit is enclosed in weatherproof enclosures filled with resin/foam to protect from weather conditions.
Protective Device:
The last main component is the protective device, which is parallel with the main coil and the tuning device.
The protective device ensures the protection of the tuning device and main coil against surge voltages. Also, It protects the main coil and the tuning device by lowering the over-voltage levels.
The bandwidth of a line trap is the frequency range over which the line trap can provide a certain specified minimum blocking impedance or resistance.
Line traps are connected in series with the power lines and thus their coils are rated to carry the full line current.
The impedance of a line trap is very low at the power frequency and will not cause any significant voltage drop.
Inside of Wave trap :
