Powerline communication

i am working with powerline communication and facing problem to design coupler circuit,,,,,,,,,if anyone know pls help.

i am confused over that
1. my frequency range is 400khz that what should be the value of coupler capacitor
2. what is the turn ratio of transformer
3.what should be the power level to transmit signal over kilometers
4. is there no any solidstate technology like photocoupler to directly coupled with ac power line . ??????????

Hi, Captain.

The coupling capacitor needs a high voltage rating, to not be destroyed by the mains voltage you are connecting to.
The capacitance value has these concerns:
Should be a low impedance for the RF frequency.
Should be a high impedance so as to not put much mains current into your transformer.

For example, a 0.1uF capacitor would be about 4 ohms to your RF while seeming to be over 26K ohms to 60 Hz.
Look for a voltage rating many times your mains voltage.

The turns ratio for the transformer will depend on the mains wiring, which is not designed for RF.
You may have to experiment.

It seems unlikely to me that you will be able to go several km.
Power line transformers tend to block RF, and you will probably encounter one or more on that length run.

I am not aware of a better way to couple to the mains than a coupling capacitor and fuse on each lead into your rf transformer.

LETHAL VOLTAGES!!!!!
Be extraordinarily careful!!!!!!

captainshahid said:

i am working with powerline communication and facing problem to design coupler circuit,,,,,,,,,if anyone know pls help.

i am confused over that
1. my frequency range is 400khz that what should be the value of coupler capacitor
2. what is the turn ratio of transformer
3.what should be the power level to transmit signal over kilometers
4. is there no any solidstate technology like photocoupler to directly coupled with ac power line . ??????????

Click to expand...

When selecting components, and designing all the mechanics, you should also look to overvoltage (transient) and pollution degree. The level of these overvoltages (surges) depends on the installation and where you are in that installation (indoor, outdoor). A search on: installation category creepage clearance pollution may give you useful info.

Safety standards describe minimum insulation strength, clearance, creepage, etc. Most information technology equipment overhere use EN60950 as safety standard.

thank's guys but is there no any solid state coupling device ?
like optocouplers..

Opto couplers, and their higher speed magnetic and capacitive IC cousins, work well to connect a low power ground referenced signal to an isolated circuit. The problems you would face using them as your interface include:
1) They are not linear
2) The 400kHz devices of which I am aware are small signal level and need a power supply on both sides of the isolator
3) You would probably need a floating power supply for the floating RF power amplifier
4) They do not handle impedance transformation, so you will probably need a power circuit for that function in any case. This could be a transformer, or it could be an LC matching network.

Hello Shahid,

"Designing" a PLT system isn't a simple task when talking about a range of kms. You need to take al radio related issues into account. Some things: S/N ratio, datarate, spectral efficiency, data coding, error correction, attenuation of the mains distribution system (including power transformers?), interference, unwanted emission (EMC regulations), etc.

Besides this, you have the safety related issues mentioned previously.

Regarding optical solutions; if you are able to provide sufficient optical power through a fiber to power all the mains electronics, you could design an optically isolated system. Of course first you need to know the power requirements.

Other option may be deriving the power from the power line itself and have a bi-directional radio link that provides isolation between your application and the mains.

Is this for low voltage mains (230Vac) or medium to high voltage installations?

thanks wimRFP
please see the link below


am i going write or this product can not meet my requirment

---------- Post added at 19:46 ---------- Previous post was at 19:42 ----------

if i will use digital encoding methods to send or receive data will it be useful over analog modulation techniques?

There are many forms of digital encoding. But if you mean things like NRZ, AMI, MLT, etc, it will very likely not work on the mains network.

Besided good data coding to cope with the errors caused by interference/noise, you need some form of modulation (PSK, FSK ASK, QPSK, MSK, (C)OFDM, etc). What method is best depends on many factors.

Regarding the optocouplers, based on the info provided I can't give feedback about this.