BY A.MANOJ CHOWDARY AM.EN.U4EEE12001 M.KIRAN NAYAK AM.EN.U4EEE12128

Power line carrier communication (PLCC)

Introduction Basic principle of PLCC Specification Basic Arrangement Tuning capacitor Wave trap Types of coupling Battery charger Fault Traction Advantages Disadvantages Conclusion

CONTENTS

POWER LINE CARRIER COMMUNICATION is the technology which is used

to communicate between electric substations through existing electrical cables.

POWER LINE CARRIER COMMUNICATION is mainly used for

telecommunication, tele-monitoring and tele-protection between electric

substations through power lines at high voltages. The data can be transfer at

9.6Kbits/sec over many miles of electrical cable.

It’s equipment are used to send/receive speech/data/teleprotection signals.

It is the most economical and reliable method of communication for medium or

long distance

INTRODUCTION

Since telephone communication system can not be directly connected to the high voltage lines, suitably designed coupling devices have to be employed.

Coupling devices consists of high voltage capacitors in conjunction with suitable line matching units(LMU’s) for line impedance matching to that of the co-axial cable connecting the unit to the PLC transmit-receive equipment.

Carrier currents used for communication have to be prevented from entering the power equipment used in GSS as this would results in complete loss of power system.

BASIC PRINCIPLE OF PLCC

The signals that can be transmitted over the PLCC can include:

1)Speech signal(300-2000Hz) 2)Data signal(2000-3000Hz)

SIGNALS FOR PLCC

PLCC SYSTEM

PLCC station Line matching circuit CVT/CC Earth switch Lightening Arrestor Wave Trap Co axial Cable

EQUIPMENTS USED

It is the station where (modulation)Transmission, Receiving(Demodulation), Amplification and Filtration are performed.

Frequency Range : 40 – 500 KHz Audio Bandwidth : 4 KHz Output Power : 10 – 80 W

ABB PLCC TERMINAL ETL-41

PLCC station

PLCC PANEL TRANSMITTER/RECIEVER

TRANSMITTER RECEIVER

For impedance matching between line and coaxial cable, includes high voltage protection devices like drainage coil(20mH), lightening arrestor(500V) and an earth switch.

LINE MATCHING UNIT

It is connected between the line matching unit and the power lines to block the high voltage entering to PLCC equipment.

It couples high frequency carries with power line.

CONTROL VOLTAGE TRANSFORMER/COUPLING CAPACITOR(CVT/CC)

Earth Switch: This is used for the maintenances of LMU. The main function of Earth switch is to ground the trapped charges. Lightning Arrestor: This is used for arresting any A.C. high

voltages spike entering to the line matching unit.

Co- Axial cable: This is used for interconnection between PLCC Station and LMU for carrying high frequency signal.

WAVE TRAP OR LINE TRAP

Wave traps – (WT’s) are used between the transmission line and the power stations to avoid carrier power dislocation in the power plant and cross talk with other power line carrier circuits connected to the same power station.

WT’s also ensure proper operating conditions and signal levels at the PLCC transmit receive equipment irrespective of switching conditions of the power circuits and equipment in the station.

A wave trap must satisfy the following requirements:  1)     It must block the carrier currents. By blocking, we mean that the

track should attenuate the H.F. signals by at least 8 to 10 dB. 2)  It must carry the power frequency current safely during normal

operation as well as during short circuit fault conditions.

WAVE TRAP

The power frequency and radio frequency are sorted by this arrangement

Carrier currents are prevented to enter station bus by wave trap & power frequency current is blocked by coupling capacitor, from the PLC equipment.

Hence we get the power current at the bus & carrier current at PLC equipment.

BASIC COUPLING ARRANGEMENT

TYPES OF COUPLING

Phase to ground coupling

Phase to phase coupling

Inter line or Inter circuit coupling

PLCC work on rectified AC or main supply, when supply goes off, it make use of a device for proper functioning of PLCC called Battery Charger.

This is the device that provide supply to the PLCC equipment for uninterrupted working.

It provide DC to the panel by battery.

BATTERY CHARGER

FAULT analysis In fault analysis the faulty devices are checked in this serial or

manner1. Telephone or tale operation signal2. Cabling low frequency circuit or DC power supply3. PLC equipment.4. HF transmission path.

Maintenance and Fault tracking

PLCC Unit Provide Five type of operation:

1:TELEPHONE FACILITES2:COMPRESSOR & EXPANDER3:EMERGENCY CALL4:SIGNAL BOOSTING5:SUPERVISION & ALARMS

APPLICATIONS

1. No separate wires are needed for communication purposes, as the power lines themselves carry power as well as communication signals. Hence the cost is less.

2. Power lines have appreciably higher mechanical strength compared with ordinary lines. They would normally remain unaffected under the conditions, which might seriously damage telephone lines.

3. Power lines usually provide the shortest route between the power stations.

4. Power lines have large cross-sectional area resulting in very low resistance per unit length. Consequently carrier signals suffer much less attenuation than when they travel on telephone lines of equal lengths.

5. Power lines are well insulated to provide only negligible leakage between conductors and ground even in adverse weather conditions

6. Largest spacing between conductors reduces capacitance, which results in smaller attenuation at high frequencies. The large spacing also reduces the cross talk to a considerable extent.

ADVANTAGES

1. Proper care has to be taken to guard carrier equipment and persons using them against high voltages and currents on the lines.

2. High voltage lines have transformer connections, attenuate carrier currents. Sub-station equipments adversely affect the carrier currents.

3.  Noise introduced by power lines is far more than in case of telephone lines. This is due to the noise generated by discharge across insulators, corona and switching processes.

4. The noise is also introduced in the signal due to bad weather conditions.

DISADVANTAGES

Power line carrier communication has been found to be the most economical and reliable method for communication in a medium and over long distance in a power system.

CONCLUSION

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