Tutorial 6: Communication Power System I & II

Transcription

1 TUTORIAL 6: SOLUTION SCHEME Q1. Give 5 example of information to be communicated in transmission network? S1. Examples of information to be communicated as follow: Direct Telephone Talk(Voice Communication) Facsimile (FAX), Transmission of Documents Protection Signalling SCADA (Supervisory Control and Data Acquisition) Control Signal Data Transmission, Electronic Mail Teleconferences, Video conferences Q2. With the aid of figure, explain briefly 2 types of communication technique used for data transmission in power system operation. S2. Types of communication technique: A. Fixed Cable Simple to connect and use Possible in urban areas where data transmission lengths are short Expensive in rural areas High capacity Used mainly between control room and primary substations In some cases between control room and readable fault indicators B. Public Telephone Low investment cost (existing data channel) Quite high operating costs Capacity problems Time needed for opening the connection System over loadings during rushing hours (during disturbance) Reliability problems Not widely used in automation applications Possible in simple data collecting applications C. Radio Link Very high capacity Expensive, not possible for customer level automation Used mainly for data transmission between control room and primary substations D. VHF Broadcast Radio VHF radio is mainly used for speech transmission (very important in network operation) VHF radio can be used also for remote control of line disconnector E. Distribution Line Carrier (DLC) Data transfer via distribution network Data channel is cheap and is connected to every customer ( existing distribution conductors) 1

2 Q3. Explain 4 methods that are available for laying the fiber optic cable with transmission line. S3. Four methods are available for laying the Fibre Optic Cable with transmission lines: Within a hollow tube carried inside overhead earth wire Wrapped around existing line conductor A separate Self supporting cable Laid in underground duct Q4. Draw the diagram with a label of power line carrier communication (PLCC) for transmission link and explain the functions of each main component inside the power line carrier communication (PLCC) system. S4. Line trap unit It function to prevent the high frequency signals from entering the neighboring line.the carrier currents flows only in the protected line. Coupling capacitor It function to allows carrier frequency signal to enter the carrier equipment but does not allow 50 Hz power frequency currents to enter the carrier equipment. Line turner It function is associated coupling capacitors and line traps provide an efficient means to couple power line carrier (PLC) signal onto a high voltage transmission line or power cable. It also used in carrier bypass circuit to route a PLC signal around discontinuities such as transformers, breakers and disconnect switches. Transmitter/Receiver To transmit a carrier frequencies signal that are generated in oscillator/to receive a carrier frequencies signal arriving from remote end and feeds to carrier receiving relay unit. 2

3 Q5. Based on figure 1 below, what are no 1, 2 3,9,10 and 11 referred to? S5. Figure 1 Q6. Based on Figure 1, explain the function of element 9, 10 and 11. S6. No 11: The purpose of the drain coil is to ground the capacitor terminal opposite the line terminal and at the same time offer high impedance at the carrier frequency. No 9: The grounding switch is used to by pass the drain coil, providing a means of directly grounding the capacitor during inspection and maintenance of the coupling and tuning equipment. No 10: The spark gap protects the drain coil from excessive surge voltages during normal operation. Q7. Explain 3 kinds of application of power line carrier. S7. Carrier Communication The person in power stations and receiving stations can communicate with each other by using this facility. Carrier Protective Relaying / Carrier Telemetering Telemetering is the indicating or recording of quantities at location remote from the point. Quantities telemetered on power system (KV,KVARS,V, Tap Changer position, CB position etc). In carrier telemetry by impulse rate system, frequency or rate of pulse varies according to the magnitude of telemetered quantity. Load and Frequency Control The control of output of group of generators on a system in such a way as to maintain the system frequency and regulate the interchange of power between parts of the system according to the predetermined plan. The two types of impulses to be transmitted one for increase in power and other for decrease. Carrier Supervisory Control SCADA Controlling the operations of the equipment from a central location. 3

4 Q8. Draw the typical SCADA system architecture S8. Q9. Give one example of SCADA application and shows its architecture. S9. Electrical Generating Plant SCADA System 4

5 Q10. Define Remote Terminal Unit (RTU). S10. An RTU (sometimes referred to as a remote telemetry unit) as the title implies, is a standalone data acquisition and control unit, generally microprocessor based, which monitors and controls equipment at some remote location from the central station. Q11. Draw the typical RTU hardware structure S11. Q12. Give 5 types of typical RTU hardware modules. S12. Typical RTU hardware modules include: Control Processor And Associated Memory Analog Inputs Analog Outputs Counter Inputs Digital Inputs Digital Outputs Communication Interface(s) Power Supply Q13. What is the different between traditional power station with modern power station which equipped with SCADA system. S13. In traditional power station / substation controls the three functions : Protection Control Monitoring were not integrated fully. In modern Automatic SCADA systems, the functions are interlinked by means of digital processing devices and power line carrier/ radio links. 5