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PLC Line Traps

Overview

Line Traps are essential components of Power Line Carrier (PLC) communication systems used in high-voltage transmission and distribution networks. Installed in series with transmission lines, they block high-frequency carrier signals while allowing power-frequency current to pass with minimal impedance. Line Traps enable reliable teleprotection, voice communication, remote control, and supervisory monitoring between substations, ensuring secure and efficient operation of modern power systems. Their robust design provides dependable performance under continuous load and fault conditions.

Features

  • Designed and manufactured in accordance with IEC 60353, IEEE Std C93.4, and IEEE Std 643
  • Engineered to meet specified short-circuit withstand requirements
  • Lightweight design for easy transportation and installation
  • Cooling spacers improve heat dissipation and reduce winding temperature
  • Replaceable tuning unit for easy frequency adjustment without dismantling the coil
  • Suitable for installation on capacitive voltage transformers (CVTs), support structures, insulators, or suspension mounts
  • Low stray capacitance and high quality factor (Q) for superior PLC performance
  • Corona grading spheres available for system voltages above 245 kV
  • Compatible with a wide range of conductor terminal designs
  • Available with DIN or NEMA terminal configurations
Two PLC line traps on top of tall insulator columns at an outdoor substation, with a lattice gantry behind

Selection Information

  • Required inductance (mH)
  • Rated current (A) at 50 Hz or 60 Hz
  • Short-circuit current (kA) and fault duration
  • Blocking frequency range (kHz)
  • System voltage (kV)
  • Required blocking impedance (Zb)
  • Resistive component of blocking impedance (Rb)
  • Mounting arrangement (CVT pedestal, support structure, or suspension type)
  • Terminal configuration (DIN or NEMA)
  • Bird barrier requirement (optional)
PLC line trap coil shown from above with suspension and lifting brackets

Standard Ratings

Standard Ratings
Nominal Current (A)Standard Short Circuit Currents (kA/1 second)Inductance (mH)
40010–160.10 / 0.20 / 0.315 / 0.4 / 0.50 / 1.00 / 2.00
63016–20
80020–25
100025–31.5
125031.5–40
160040–50
200050–63

Band Limits of Wide Band Line Traps

Blocking Impedance Ω
Tapping Loss dB
LAL1C1L2C2R2TDLT
L1
Main coil
Zb
Blocking impedance (Ω) of LT
Rb
Blocking resistance (Ω) of LT
At
Tapping loss
Ab
Blocking attenuation
f′1, f′2
Frequency limits of impedance blocking
f1, f2
Frequency limits of resistive blocking impedance
At=20 log⁡10(1+Z12 Zb) (dB)A_{\mathrm{t}} = 20\,\log_{10}\left(1 + \dfrac{Z_1}{2\,Z_{\mathrm{b}}}\right)\ \text{(dB)}
Ab=20 log⁡10(1+Z12 Rb) (dB)A_{\mathrm{b}} = 20\,\log_{10}\left(1 + \dfrac{Z_1}{2\,R_{\mathrm{b}}}\right)\ \text{(dB)}
Blocking Resistance Ω
Tapping Loss dB
LAL1C2R2TDLT
fr
Resonance frequency
LA
Surge arrester
TD
Tuning device
Z1
Network impedance (normally 400 Ω for bundled conductors and 600 Ω for single conductors)
fr=f1⋅f2f_{\mathrm{r}} = \sqrt{f_1 \cdot f_2}

Blocking Bandwidths of Tuning Devices

Upper Band Limit (f2) kHz
  • For line characteristic impedance ZL = 400 Ω (at bundled conductors)
  • Blocking resistance Rb ≥ 570 Ω
  • Tapping loss At ≤ 2.6 dB
k
fr (kHz)k
200.75
400.80
600.85
800.88
1000.90

15-minute overload capacity

15-minute overload capacity
Ambient Temperature (°C)× In
+401.4
01.5
−401.6

In : Nominal Current (A)

Resistive component of blocking impedance

Rmin=k π L1 f2⋅f1f2−f1  [Ω]R_{\text{min}} = k\,\pi\,L_1\,\dfrac{f_2 \cdot f_1}{f_2 - f_1}\ \ [\Omega]

Minimum value of blocking impedance

Zmin=2⋅Rmin  [Ω]Z_{\text{min}} = \sqrt{2} \cdot R_{\text{min}}\ \ [\Omega]

Connection and Mounting Dimensions

10mm 50mm 25mm25mm 25mm 50mm Ø13mm Iₙ < 750 A
10mm 100mm 25mm50mm25mm 25mm 50mm Ø13mm 750 A ≤ Iₙ < 1600 A
10mm 150mm 25mm50mm50mm25mm 25mm 50mm Ø13mm 1600 A ≤ Iₙ < 2000 A
10mm 200mm 25mm50mm50mm50mm25mm 25mm 50mm Ø13mm 2000 A ≤ Iₙ < 3150 A

Consult Hilkar for NEMA, DIN norms or others.

Standard pedestal fixation dimensions

Ø14 mmØ18 mmØ297 mmØ127 mm
PEDESTAL500 mmØ400 mm

For other pedestal fixation dimensions, consult Hilkar.