Telecommunications is a very important means of operation for electrical center, especially if the central electrical work within the system interconnect. Telecommunications facilities that are commonly used in power plants are:
1. Payphones, including: Facsimile, telex, and electronic mail.
2. Power line carrier, for voice and for data transmission, including for the protection of the system.
3. Fibre optics can take over the functions of a public telephone or power line carrier.
If the power station operates in system interconnect, the communication between the operational power stations with a central regulator of load (system operator) is very important. If the tool or system supervision is commonly referred to as supervisory control and the data aquisition (SCADA) of the central regulator of load using a computer, then the power station there should be a microprocessor that can communicate with the SCADA computer. This microprocessor is equipped with a variety of modems and peripherial called remote terminal unit (RTU).
RTU record various data and events from the mains to be reported to the SCADA computer that is in the center of the load regulator. Central regulator of load through the SCADA computer may request data and information on various events experienced electrical center.
Central regulator of load can also send an electric signal to the center setting, for example a signal to open or close the PMT or signals to regulate the load generating units in order to burden sharing in the context of economic and system settings or frequency.
Power Line Carrier (PLC) is a telecommunications system that uses a transmission line as a signal transmission medium. Modulation used is single side band amplitude modulation (AMSSB) with carrier frequency (carrier) around 4.00 kilo Hertz.
The principle of the arrival of the PLC telecommunications schematically illustrated by Figure II.106. Telecommunication circuits plane relationship of SSB to the high voltage line is done through coupling capacitor (coupling capacitor) after the first through line matching unit (LMU) to generate maximum power.
To prevent telecommunications signal frequency is much power in the base frequency (50 Hertz) into the power measurement circuit, the voltage at the end of finggi in the GI tract before entering the electric power measuring devices installed coils which in English is called wave trap.
Power line carrier (PLC) generally have a channel for communication and for the data channel. Channel is normally used for SCADA and protection relays intertripping. Remote terminal unit (RTU) as illustrated by Figure II.107 consists of a microprocessor is equipped with a read only memory (ROM) and random access memory (RAM).
Figure II.106 Schematic working principle of PLC Description:
TX = Transmitter Unit SSB;
RX = Receiver Unit SSB;
LMU = Line Matching Unit
At the input there are analog inputs derived from the current transformer and voltage transformer having first through a transducer and an analog to digital converter. While in the digital input signal is derived from the position of the circuit breaker (PMT) to open or close. At the output of existing analog RTU output to adjust the position of governor of the generating unit. While its digital output is to open or close the PMT.