Kawaradduka Tushen Kirki na Maimakon Zafi | PLCC

A cikin kalmomi wired wireless, Power Line carrier Communication (PLCC) ya zama da tarihi mai yawa daga amfani a matsayin metering a wurare na gaba zuwa amfani a ranar da za ake yi a cikin home automation, high speed internet access, smart grid, kuma wasu. A farkon shekarun 20th, masu company ta power sun amfani da telephones domin magana a kan voice messages don takarda, maintenance, control, kuma haka a matsayin hanyar inganta a wurare. Lissafi telephones suka zama sallama ne a kan lissafi power lines. Wannan ya ba da nau'o'i da dama:

• Amfani da telephone circuits a wurare da damu ko a wurare da damu masu abubuwa kamar duwatsu ita ce ta fiya.

• Noise interference saboda currents sake zama a parallel power lines a kan telephone circuits.

• Kammalwa da telephone cables a lokacin da harsh weather conditions kamar snows a rabi, storms, kuma wasu ya ba su da inganci.

Wannan ya haɗa a fadada wajen bincike hanyar inganci da kuma karfi. Amfani da power line a matsayin hanyar telephony ya zama fikirar da ake yi a kan lokaci, kuma aiki aikinsu ta shahara ta shahara a Japan a shekarar 1918. Kuma bayan nan, commercialization ta ya faru a shekarun 1930s.

Power Line Carrier Communication

Figure 1 ta nuna basic PLCC network da ake amfani a power substations. Power line carrier Communication (PLCC) ta amfani da infrastructure na power da ke tsakanin a kan sending to receiving end. It works in full duplex mode. PLCC system ta rage da uku parts:

1. The terminal assemblies include the receivers transmitters and protective relays.

2. The coupling equipment is the combination of line tuner, coupling capacitor and the wave or line trap.

3. The 50/60 Hz power transmission line serves as path for relaying data in the PLCC bandwidth.

Coupling Capacitor

It forms the physical coupling link between transmission line and the terminal assemblies for the relaying of carrier signals. Its function is to provide high impedance to power frequency and low impedance to carrier signal frequencies. They are usually made up of paper or liquid dielectric system for high voltage application. The ratings of coupling capacitors range from 0.004-0.01µF at 34 kV to 0.0023-0.005µF at 765kV (source: IEEE).

Drain Coil

As shown in the figure 1 the purpose of drain coil is to provide high impedance for carrier frequency and low impedance for power frequency.

Line Tuner

It is connected in series with the coupling capacitor to form a resonant circuit or carrier signal frequency high pass filter or band pass filter. Its function is to match the impedance of the PLC terminal with the power line in order to impress the carrier frequency over the power line. In addition it also provides isolation from power frequency and transient overvoltage protection.

Line Trap or Wave Trap

It is a parallel L-C tank filter or band-stop filter connected in series with the transmission line. It presents high impedance to carrier signal frequencies and very low impedance to the power frequency. It consists of

1. Main coil

   An inductor that is connected directly to the high voltage power line carries power frequency.

2. Tuning device

   It may be a capacitor or a combination of capacitor, inductor and resistor, connected across the main coil in order to tune the line trap to the desired blocking frequency.

3. Protective device

   It is usually a gap type surge arrester used to protect the line trap from damage due to transient over-voltages.

The line trap or wave trap prevents unwanted loss of carrier signal power and also prevents carrier signal transmission to adjacent power lines. Line traps or wave traps are available for narrow-band and wide-band carrier frequency blocking applications.

Power Line Channel Characteristics

• Characteristic Impedance

  The characteristics impedance of transmission line is given by :
  
  Where, L is the inductance per unit length in Henry(H).
  C is the capacitance per unit length in Farad(F).
  It varies in the range of 300-800 Ω for power line communication.

• Attenuation

  It is measured in decibels(db). Attenuation losses can be due to the impedance mismatching, resistive losses, coupling losses and various other losses that occur in the line trap, line tuner, power line etc.

• Noise

  The signal-to-noise ratio(SNR) must be high at the receiving end, other wise the carrier frequency shows erratic patterns at the receiving end. The noise level limit the attenuation that PLCC channels can tolerate.

• Bandwidth

  The wider bandwidth means faster the channel, but it also leads to the accentuation of noise. For relaying purpose, AM channel bandwidth is around 1000Hz to 1500Hz and for FSK bandwidth it is 500Hz to 600Hz (source: IEEE).

Sada