Sistema Scada

DEFINITION OF SCADA SYSTEM. 

SCADA STANDS FOR SUPERVISORY CONTROL AND DATA ACQUISITION (SUPERVISORY CONTROL AND DATA ACQUISITION). 

A SCADA IS A COMPUTER-BASED MONITOR AND CONTROL THAT ENABLES REMOTE INSTALLATION OF ANY SYSTEM. UNLIKE DISTRIBUTED CONTROL SYSTEMS, THE CONTROL LOOP IS CLOSED BY THE OPERATOR GENERALLY. DISTRIBUTED CONTROL SYSTEMS ARE CHARACTERIZED BY PERFORMING CONTROL ACTIONS AUTOMATICALLY. TODAY IT IS EASY TO FIND A SCADA SYSTEM PERFORMING TASKS AUTOMATIC CONTROL IN ANY LEVEL, BUT THEIR MAIN TASK IS MONITORING AND CONTROL BY THE OPERATOR. TABLE NO. 1 SHOWS A COMPARISON OF THE MAIN FEATURES OF THE SCADA SYSTEMS AND DISTRIBUTED CONTROL SYSTEMS (DCS) IS SHOWN (THESE FEATURES ARE NOT LIMITING TO ONE TYPE OR SYSTEMS ARE TYPICAL).

THE FLOW OF INFORMATION ON SCADA SYSTEMS IS AS FOLLOWS: THE PHYSICAL PHENOMENON WHAT IS THE VARIABLE THAT WE WANT TO MEASURE. DEPENDING ON THE PROCESS, THE NATURE OF THE PHENOMENON IS VERY DIVERSE: PRESSURE, TEMPERATURE, FLOW, POWER, CURRENT, VOLTAGE, PH, DENSITY, ETC. THIS PHENOMENON SHOULD LEAD TO A VARIABLE THAT IS INTELLIGIBLE TO THE SCADA SYSTEM, IE, AN ELECTRICAL VARIABLE. TO THIS END, SENSORS OR TRANSDUCERS ARE USED. 

SENSORS TRANSDUCERS OR CONVERTING VARIATIONS OF THE PHYSICAL PHENOMENON IN PROPORTIONAL VARIATIONS OF AN ELECTRICAL VARIABLE. THE ELECTRICAL VARIABLES MOST COMMONLY USED ARE: VOLTAGE, CURRENT, CHARGE, RESISTANCE OR CAPACITANCE. 

HOWEVER, THESE VARIOUS TYPES OF ELECTRIC SIGNALS MUST BE PROCESSED TO BE UNDERSTOOD BY THE DIGITAL COMPUTER. THIS USED SIGNAL CONDITIONERS, WHOSE FUNCTION IS TO REFERENCE THESE ELECTRICAL CHANGES ON THE SAME SCALE CURRENT OR VOLTAGE. IT ALSO PROVIDES ELECTRICAL ISOLATION AND FILTERING OF THE SIGNAL IN ORDER TO PROTECT THE SYSTEM FROM TRANSIENTS AND NOISE ARISING IN THE FIELD. 

ONCE FITTED THE SIGNAL, IT IS CONVERTED INTO AN EQUIVALENT DIGITAL VALUE IN THE BLOCK DATA CONVERSION. GENERALLY, THIS FUNCTION IS PERFORMED BY A CIRCUIT FOR ANALOGUE / DIGITAL CONVERSION. THE COMPUTER STORES THIS INFORMATION, WHICH IS USED FOR ANALYSIS AND DECISION MAKING. SIMULTANEOUSLY, THE INFORMATION IS DISPLAYED TO THE USER OF THE SYSTEM IN REAL TIME. 

BASED ON THE INFORMATION, THE OPERATOR CAN MAKE THE DECISION TO PERFORM A CONTROL ACTION ON THE PROCESS. THE OPERATOR COMMANDS THE COMPUTER TO DO IT, AND AGAIN MUST BECOME DIGITAL INFORMATION INTO AN ELECTRICAL SIGNAL. THIS ELECTRICAL SIGNAL IS PROCESSED BY AN OUTPUT CONTROL, WHICH FUNCTIONS AS A SIGNAL CONDITIONER, WHICH SCALE TO MANAGE A GIVEN DEVICE: A RELAY COIL, SETPOINT OF A CONTROLLER, ETC. 

NEED A SCADA SYSTEM. 

TO ASSESS WHETHER A SCADA SYSTEM IS NEEDED TO HANDLE A GIVEN INSTALLATION, THE PROCESS CONTROL MUST MEET THE FOLLOWING CHARACTERISTICS: 

A) THE NUMBER OF PROCESS VARIABLES THAT NEED TO BE MONITORED IS HIGHER. 

B) THE PROCESS IS GEOGRAPHICALLY DISTRIBUTED. THIS CONDITION IS NOT RESTRICTIVE, SINCE IT CAN INSTALL A SCADA FOR MONITORING AND CONTROLLING A PROCESS CONCENTRATED IN ONE LOCATION. C) THE REQUIRED PROCESS INFORMATION AT THE TIME THAT THE CHANGES IN THE SAME, OR IN OTHER WORDS, THE INFORMATION IS REQUIRED IN REAL TIME. 

D) THE NEED TO OPTIMIZE AND FACILITATE PLANT OPERATIONS AND DECISION MAKING, BOTH MANAGERIAL AND OPERATIONAL. 

E) THE PROFITS IN THE PROCESS JUSTIFY THE INVESTMENT IN A SCADA SYSTEM. THESE BENEFITS MAY BE REFLECTED AS INCREASED EFFECTIVENESS OF PRODUCTION, SAFETY STANDARDS, ETC. 

F) THE COMPLEXITY AND SPEED OF THE PROCESS ALLOWS MOST OF THE CONTROL ACTIONS ARE INITIATED BY AN OPERATOR. OTHERWISE, IT WILL REQUIRE AN AUTOMATIC CONTROL SYSTEM, WHICH IT MAY CONSTITUTE A DISTRIBUTED CONTROL SYSTEM, PLC'S, CONTROLLERS CLOSED-LOOP OR A COMBINATION THEREOF. 

FUNCTIONS. 

AMONG THE BASIC FUNCTIONS PERFORMED BY A SCADA SYSTEM ARE THE FOLLOWING: 

A) COLLECT, STORE AND DISPLAY INFORMATION CONTINUOUSLY AND RELIABLY, LEDS LIGHT FIELD: DEVICE STATUS, MEASUREMENTS, ALARMS, ETC. 

B) IMPLEMENT CONTROL MEASURES INITIATED BY THE OPERATOR, SUCH AS OPENING OR CLOSING VALVES, STARTING OR STOPPING PUMPS, ETC. 

C) ALERT THE OPERATOR CHANGES DETECTED IN THE PLANT, BOTH THOSE THAT ARE NOT CONSIDERED NORMAL (ALARMS) AND CHANGES THAT OCCUR IN THE DAILY OPERATION OF THE PLANT (EVENTS). THESE CHANGES ARE STORED IN THE SYSTEM FOR LATER ANALYSIS. 

D) APPLICATIONS IN GENERAL, BASED ON THE INFORMATION OBTAINED BY THE SYSTEM, SUCH AS REPORTS, TREND GRAPHS, HISTORY VARIABLES, ESTIMATES, FORECASTS, LEAK DETECTION, ETC.