Wave traps (high-frequency stoppers)
Wave traps or line traps (high-frequency stoppers) are maintenance-free parallel resonant circuits, mounted inline on HV AC transmission power lines to prevent the transmission of high frequency (40 kHz to 1000 kHz) carrier signals of power line communication to unwanted destinations. Line traps are cylinder-like structures connected in series with HV transmission lines.
The wave trap acts as a barrier or filter to prevent signal losses. The inductive reactance of the line trap presents a high reactance to high-frequency signals but a low reactance to mains frequency. This prevents carrier signals from being dissipated in the substation or in a tap line or branch of the main transmission path and grounds in the case of anything happening outside of the carrier transmission path.
The line trap is also used to attenuate the shunting effects of high-voltage lines.
The reactor coil, depending on the device, can be made up of several aluminum wires, allowing equal distribution amongst the parallel wires. 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.
This smaller coil is attached to both ends of the main coil.
Its purpose is to create a blocking circuit which provides high impedance. There are three types of tuning devices: wideband tuning, single frequency tuning, and double frequency tuning. The tuned circuit is usually a dual-circuit broadband type.
If the traps are self-tuned, they do not require the use of any tuning devices. With the use of a tuning device, a line trap can be tuned to a frequency of 1000 Hz. The last main component is the protective device, which is parallel with the main coil and the tuning device. 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.
In order to separate power from messages being sent, different frequencies are used. Electrical power has a frequency of 50 Hz or 60 Hz in most places, and the communication waves use frequencies such as 150 kHz and 200 kHz. Line traps consist of filter circuits that allow only power frequency waves to travel to that of electrical equipment.
They also stop communication waves from traveling to equipment. Communication is crucial for substations.
|Title:||132 kV, 220 kV and 400 kV networks and substation equipment – Ankur Paul at Department of Electrical Engineering, Girijananda Chowdhury Institute of Management and Technology (GIMT)|
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