POWER LINE CARRIER CHANNEL & APPLICATION

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POWER LINE CARRIER CHANNEL & APPLICATION

Introduction

POWER LINE CARRIER CHANNEL & APPLICATION

    While the application of Power-Line Carrier is not new to the power utility industry, the people who have historically worked on this type of equipment are leaving the industry, thereby creating a tremendous void in the expertise available. This paper is a tutorial that will present the basic principles of Power-Line Carrier to assist engineers who are new to this field as well as provide some good reference material for those experienced individuals who desire refresher information. It will focus on the application of carrier in Protective Relaying schemes.

AC Power Distribution Systems and Standards

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History of PLC

    Power Line Carrier (PLC) has been around longer than you think. For example, at the turn of the 20th century, a 500 Hz signal on the power line was used to control the street lights in New York City. The transmitters and receivers were originally powered with M-G (motor-generator) sets with a tuning coil 3 feet in diameter. As technology progressed, so did the PLC equipment. There are still many transmitters and receiver sets in use today that utilize vacuum tubes, or discrete transistor logic but these are being replaced with state of the art components such as digital signal processors and other VLSI components.

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Goals

Many factors will affect the reliability of a power line carrier (PLC) channel. The goal is to get a signal level to the remote terminal that is above the sensitivity of the receiver, and with a signal-to-noise ratio (SNR) well above the minimum, so that the receiver can make a correct decision based on the information transmitted. If both of these requirements are met then the PLC channel will be reliable. The factors affecting reliability are:

• The amount of power out of the transmitter.

• The type and number of hybrids required to parallel transmitters and receivers.

• The type of line tuner applied.

• The size of the coupling capacitor in terms of capacitance.

• The type and size, in terms of inductance, of the line trap used.

• The power line voltage and the physical configuration of the power line.

• The phase(s) to which the PLC signal is coupled.

• The length of the circuit and transpositions in the circuit.

• The decoupling equipment at the receiving terminal (usually the same as the transmitting end).

• The type of modulation used to transmit the information, and the type of demodulation circuits in the receiver.

• The received signal-to-noise ratio (SNR).

Read Continually.... 

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