What is the difference between SCADA & DCS?

Answer 1

#DCS is process oriented: it looks at the controlled process (the chemical plant or whatever) as the centre of the universe, and it presents data to operators as part of its job. SCADA is data-gathering oriented: the control centre and operators are the centre of its universe. The remote equipment is merely there to collect the data--though it may also do some very complex process control!

A DCS operator station is normally intimately connected with its I/O (through local wiring, FieldBus, networks, etc.). When the DCS operator wants to see information he usually makes a request directly to the field I/O and gets a response. Field events can directly interrupt the system and advise the operator.

SCADA must operate reasonably when field communications have failed. The 'quality' of the data shown to the operator is an important facet of SCADA system operation. SCADA systems often provide special 'event' processing mechanisms to handle conditions that occur between data acquisition periods.

There are many other differences, but they tend to involve a lot of detail. The underlying points are:

SCADA needs to get secure data and control over a potentially slow, unreliable communications medium, and needs to maintain a database of 'last known good values' for prompt operator display. It frequently needs to do event processing and data quality validation. Redundancy is usually handled in a distributed manner.

DCS is always connected to its data source, so it does not need to maintain a database of 'current values'. Redundancy is usually handled by parallel equipment, not by diffusion of information around a distributed database.

These underlying differences prompt a series of design decisions that require a great deal more complexity in a SCADA system database and data-gathering system than is usually found in DCS. DCS systems typically have correspondingly more complexity in their process-control functionality.

#To put in very simplistic terms, a SCADA system is event driven, while a DCS is process state driven. A DCS is primarily interested in process trends, a SCADA system in process events.

Answer 2

There is enough details already on the answers so I would avoid repeatation & try to high light only.
A SCADA is a link between the system (PLC OR DCS) known more popularly as HMI(Human & Machine Interface). The machine works in machine language and needs to be translated into a scheme where man can interpret the result and give his inputs/commands. Even if a scada fails the plc or dcs will continue to operate as per the last commands.
A scada is a program. suppose you have a temp. control loop, you need to set range and set point of the loop. You need to define control action which is understood by the dcs. This is the job of a scada.
A dcs or plc can operate on different scada softwares.

Answer 3

SCADA is a control layer above a DCS/RTU system.

The elements of a DCS system can perform SCADA, but SCADA doesn't perform DCS. Consider a union job site foreman as the SCADA, his workers are the DCS. The DCS does the actual work, the forman issues commands and takes reports from the workers.


SCADA = Supervisory Control And Data Acquisition. (Supervisor as in foreman)
The acquision part can incorporate analysis, however it is the collection of data and storage(database) that is the primary function of DAQ (Data AcQuisition).

SCADA provides several functions to a system:
1.) Control - Remote operation of the system. Local control is done with a physical switch next to a pump for example. SCADA provides a means to turn that pump On/Off without having to use the physical switch on the plant floor. This is done by communicating that request to a device which can control that pump.
SCADA provides virtual control buttons and adjustment dials that can be access via the computer (or across the web). SCADA may make automated adjustments such as changing a setpoint . SCADA doesn't provide regulation of control variables a local PLC would handle that(See DCS)
2.) Monitoring - collection of data readings from across the system, displaying them in a central location. Operators do not have to travel to a physical loaction of a gauge to read a pressure or temperature.
3.) usually an Alarm system to alert when a process variable has an excursion beyond preset levels.
4.SCADA is not directly connected to the pumps and equipment that it controls.


DCS (Distributed Control System) - Simply means that there is more than one computer control (PLC for example) across the process and are not in one location. Consider a network of smaller PLC's exchanging data.

Controllers in a DCS system handle the high speed adjustments to keep the process variable at the set point. These controllers receive commands from a SCADA or Local input to change to a new setpoint. It is these controllers which ensure that deviations from setpoint are detected and compensated for if possible.

Answer 4

This Site Might Help You.

RE:
What is the difference between SCADA & DCS?

Answer 5

Scada - is Supervisery Control And Data Analysis.
This is used in electrical installations for monitoring and remote operation of control and protective systems.
DCS is Distributed control systems- (would like to know myself).

Answer 6

wts dis?