Wave Trap: Learn the Purpose, Cost, and Lead Time to Procure

wave trap
Wave trap. Image credit: Ohio Edison – Lisbon substation.
Table Of Contents

Purpose of wave trap

A wave trap, also known as line trap, is a band-stop or notch filter. It blocks the high-frequency carrier signal and allows 60hz power frequency. A wave trap, CCVT, line tuner, and carrier relays – work hand-in-hand implementing Power Line Carrier pilot protection.

The trap is mounted either horizontally or vertically. It is sized to handle the continuous load current and the mechanical stress generated by the high magnitude fault current for a short time period.

The GIF below shows how the carrier frequency is contained using the wave traps. The frequency that travels on the line is chosen from a range of 30kHz to 500kHz. So, while the trap is tuned to block this frequency, it allows the 60hz power frequency through.

Power line carrier - PEguru
Wave traps restricts the carrier frequency to the line it is meant to travel in.
Wavetrap and CCVT for Power Line Carrier implementation
Wavetrap and CCVT for Power Line Carrier implementation. Image credit: First Energy – Penn power.

One additional item factored into the trap design is how the inductance of the trap reacts with the capacitive elements in the substation. Because of capacitance in various equipment, shown in the image below, a series resonant circuit is formed with the inductance in wavetrap. This mini-circuit diminishes the inductive impedance leading to more carrier signal leaking through the trap.

One way to combat this issue begins by introducing a resistor into the wavetrap’s tuning hardware (one that contains the capacitor). Although adding this resistance (typically 400 ohms, matching t-line characteristic impedance) decreases the peak impedance offered to the carrier signal, it limits the resonance. This logic, however counter-intuitive, is a worthwhile trade-off.

High Q Low Q Wave Traps
High Q Low Q Wave Traps. With the addition of resistance, the reactive impedance (quadrature axis) is lowered.

Cost of wave trap

  • 69kV 1200Amp wave trap: ~$12,000 each
  • 138kV 2000Amp wave trap: ~$12,000 each
  • 230kV 2000Amp wave trap: ~$25,000 each
  • 345kV 3000Amp wave trap: ~$30,000 each

Note: The cost of any support structure is not included.

Lead time to procure wave trap

~20 weeks

Information on cost and lead time is for your general knowledge only. Contact vendor with your equipment specifications for actual figures.

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Wave Trap: Learn the Purpose, Cost, and Lead Time to Procure 1

Substation Major Equipment

It’s only stupid-simple, let’s begin.

What’s the purpose of a conventional power transformer?
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An industrial facility is plagued with voltage flicker (due to harmonics) and poor power factor at the service entrance. Which device would you install to fix both issues?
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For which event should a surge arrester operate? Check all that apply.
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A transformer develops an internal fault. Which device would you install on the transformer high-side to interrupt fault current?
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Which combination of devices would you use to implement power line carrier?
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You are building an interconnect station, tying wind farm generation to the power grid. At the substation, the sources are tied through a tie-breaker. Which device would you install to make sure the sources are synchronized?
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In a distribution substation, the available ground-fault current on the low side of the step-down transformer is excessive, over-dutying the switching equipment. What is your cost-effective solution to reducing the fault current?
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