Difference between AC & DC
Single Phase AC
Three Phase AC
Resistance, Reactance and Impedance
Facets of Energy
Sources of Generation
Generation of Electricity
Constructional Features of PT
Net & Gross Metering
Fuse Wire Table
Size of Earth lead
Size of Earth lead
Station Battery Maintainence
Calculation of VR
11KV UG cable VR
Calculation of Power loss and VR
Basic checks of Relays
BEE Star Labels
What is SCADA?
SCADA means Supervisory Control and Data Acquisition.
A Scada system is one which facilitates an operator to control a remote system and acquire real time information from a remote location.
Control and data acquisition can be from a single point or from multiple points.
Where SCADA is used?
Power Generation, Transmission and Distribution.
Civic bodies – viz Control of street lights.
Benefits of SCADA:
Scada for Power Transmission:
The Load dispatch center is the hub for load dispatch and control.
LDC requires data with respect to available generation and load to be attended as such,
Real time Data is required from all Generating stations
Real time Data is required from Receiving stations
Real time Data is required from Interface points (Feeders) from where power is delivered to Distribution companies or Consumers.
LDC has to exercise control over the receiving stations, and consumers and if necessary the Generators also as such,
Supervisory control is required to shed loads by opening a breaker.
Supervisory control is required switch off or switch on a consumer.
Supervisory control is required to control the generation as and when control is extended.
What is a transducer ?
A transducer is a device, usually electrical, electronic, or electro-mechanical, that converts one type of energy to another for the purpose of measurement or information transfer. In a broader sense, a transducer is sometimes defined as any device that senses or converts a signal from one form to another.
An Electrical transducer in our case, is one, which is used to change an electrical quantity such as voltage, current, power or frequency into a proportional dc output.
AC voltage and/or Current--------> Transducer-------->DC current.
AC Transducer inputs
Current,Voltage,Power (watts, Vars, VA),Frequency,Power Factor.
AC Transducer outputs
Industry standards:4-20mA,0-10mA.Others available: 0-1mA, 0-10V, ...
Transducer outputs are load independent
Simplified transmitting of data over long distances.
Several indicating instruments can be connected to the same transducer without any adjustments.
Adjustment of instrument wire resistance is not required.
Use of thin wires makes wiring simple and inexpensive.
Instruments can be easily connected or disconnected without affecting the measuring value of other instruments in the circuit.
The transducer can be open-circuited or short-circuited without causing any problems.
What is a RTU ?
The SCADA RTU is
small ruggedized computer
provides intelligence in the field,
allows the central SCADA master to communicate with the field instruments.
stand alone data acquisition and control unit.
Its function are
to control process equipment at the remote site.
acquire data from the equipment.
transfer the data back to the central SCADA system.
Software functionality in an RTU:
Real time operating system.
scanning the inputs,
monitoring the communications ports.
Driver for the communications system.
Device drivers for the I/O system (field devices).
scanning of inputs
processing and storing of data
responding to requests from the SCADA master
RTU – Basic operation:
The RTU will operate scanning its inputs normally at a fairly fast rate
Responds to Master when polled
Some processing changes such as,
Change of state
Time stamping of changes
Storage of data awaiting polling from Scada master
Reporting to Scada Master
SCADA Components in Energy Sector:
RTUs at stations, Generating stations and control centers
Communication media by VSAT
SCADA Master control system at LDC
Utilization of SCADA functions:
REAL TIME DATA ACQUISITION FROM ALL RTUs
PROCESSING OF ACQUIRED DATA.
DATA EXCHANGE BETWEEN CONSTITUENTS
LIMIT / STATUS MONITORING & ALARMING.
SEQUENCE OF EVENT RECORDING.
INFORMATION STORAGE & RETRIEVAL.
DATA RETRIEVAL FOR ABT FUNCTIONS.
DATA RETRIEVAL FOR RMMI FUNCTIONS.
Dynamic trends of key analog data against time are set for LDC
DISTURBANCE DATA COLLECTION
Reports are generated from stored data
CONTINUOUS RECORDING DATABASE
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