MODULE 1 and 2 Flashcards
Steps to program PLC/RTU
- Control Strategy/Narrative
- Tags, I/O
- Controller type
- Program
- Test and Download
number of physical SCADAPACK 32 AI
8 30001-30008 Input
number of physical SCADAPACK 32 DI
16 10001-10015 Status
number of physical SCADAPACK 32 DO
12 1-12 Coil
What are the Coil registers in a SCADAPack 32 and type of I/O
00001-04096
DO
What are the Status registers in a SCADAPack 32 and type of I/O
10001-14096
DI
What are the Input registers in a SCADAPack 32 and type of I/O
30001-39999
AI
What are the Holding registers in a SCADAPack 32 and type of I/O
40001-49999
AO
Which type of I/O are readable only and which types are read//write
Read Only - AI/DI
Read/Write - AO/DO
For timers what are:
The preset value
The accumulated value
The time base
The preset value
(Which is the constant number of seconds the timer times to, before being
energized or de-energized)
The accumulated value
(Which is the number of seconds which records how long the timer has been
actively timing)
The time base
(Which indicated the accuracy in seconds to which the timer operates e.g. 1
second, 0.1 seconds and even 0.01 seconds)
What is a retentive timer?
Accumulator holds value even if input goes to low
3 Types of timers
ON delay
Off Delay
Retentive
3 Types of Counters
CTU - Count up
CTD - count down
CTUD - count up down
5 Parts of a SCADA system
- Feild devices
- RTU
- Communications
- MTU
- User Interface
Describe the function of SCADA
- Display
- Trend (history)
- Alarms
- Reporting
- Animation
Describe the function of SCADA
- Display
- Trend (history)
- Alarms
- Reporting
- Animation
5 Parts of a SCADA system
- Field-level instruments
- Marshalling terminals and RTUs
- Communications
- Master Station
- Commercial data processing system
Describe the function of SCADA
- Alarm management and areas of responsibility
- Trending and plotting
- Reporting
- Event recording (Audit Trails)
- Display Building
difference between RS232 RS485
RS232 is only point to point
RS485 is point to multipoint
Max Distance for 4-20mA
1.2km
Max Distance for 1-5V
15m
Max Distance for RS232
15m
Max Distance for Rs485
1.2km
Ethernet
100m
What is the function of WDT
Watch dog timer
Ensure the CPU of the system has not frozen
What is a sink or source in terms of a modules
Sink - Draws from a source
Source - Outputs
What are the horizontal and vertical lines of ladder logic called
Horizontal - Rung
Vertical - Rail
Define SCADA
A system containing a number of RTUs that collect
field data and which are connected to the Master
station, using a communications system
Define DCS
The data acquisition and control functions performed
by a number of microprocessor-based units,
distributed by the devices being controlled
Define PLC
A programmable logic controller that uses ladderlogic software and solid state electronic modules for
both input and output
Additionally:
• Most PLCs now also offer function block programming
Define PLC
A programmable logic controller that uses ladder logic software and solid state electronic modules for
both input and output
Additionally:
• Most PLCs now also offer function block programming
What does OPC stand for
OLE for Process Control
What does OLE stand for
Object Linking and Embedding
What is an Isolated card and what are the types
Input kept separate from the card
Optical, Relay and Transformer
What is CSMA
Carrier select multiple access
What is CSMACD
Carrier select multiple access, Collision detection
AI_1 unity pro address
%IWO.4.0 - %IWO.4.5
DO_1 unity pro address
%QO.3.0 - %QO.3.14
HMI Parta
- Display
- Enter value
- alarm
- trend
- animation
Modbus may have ___ salve adress
247
ISO/OSI means
international standards society/ open systems interconnect
field bus protocol includes
digital signals using digital transmitter
if FF comms fail loop fails
token passing protcol with a large number data transfer is:
relatively slow
advantage of fiber optiocs
noise immunity
the shield on belden cable must be grounded at
the receiver
most common form of digital communication
serial
most common form of digital communication
serial
modbus uses what method for media access
polling
ACSII means
american standard code for information interchange
demodulation is what?
separation of data from a carrier signal
a byte is?
8 bits of data
8 bit extended ascii consists of
256 distinct characters
4 areas of improvement in SCADA
Rapid improvement in LAN technology for master stations
Man machine interface
Remote terminal units
Communications
The twelve golden rules
- KISS, keep it simple stupid
- Response time within correct levels
- Redundancy
- use open systems
- scale-able
- asses from view of max traffic
- clearly defined
- thorough tsting
- confrim operation of components in actual envrioments
- well documented
- good training
- simple operator screen
how to connect shield?
connect only 1 end
What is Function code 01
read discrete output
What is Function code 05
write single discrete output
What is Function code 15
write multiple discrete outputs
What is Function code 02
read discrete input
What is Function code 04
read input register
What is Function code 03
read analog output
What is Function code 06
write single analog output
What is Function code 16
write multiple analog output
What 5 components make up an analog in
Input multiplexer Input signal amplifier Sample and hold circuit A/D converter Bus interface and board timing system
Analog output module typical has
8 analog outputs
Resolution of 8 or 12 bits
Conversion rates of 10 microseconds to 30 milliseconds
Outputs range from 4.20 mA +- 10 volts
typical analog input has
8 or 16 analog inputs Resolution of 8 or 12 bits Range of 4-20mA Input resistance of 240 Kohms to 1 Mohm Conversion rates of 10 microseconds to 30 milliseconds Inputs are generally single ended
what is a dry contact card
card has power supplied from the terminal strip on the card.
what is an isolated card
card has power supplied from an external power supply
Describe the operating and safety conditions for power sources
- Operating Temp: -40 to + 75 C.
- Use rechargable lithium battery to provide more reliable clock backup.
- Some RTUs have multiple auxiliary voltage outputs to provide power to communication modems and sensors, some of these outputs are adjustable via RTU application.
- Heat convention cooling help maitaining the internal tempreture in the power supply and hence boost its operating reliability.
- Controlled powerline to DO modules enables centralized inhibiting of all relay outputs in the selected DO modules.
- Short current limit on the outputs help protecting the power supply and backup battery in case malfunction of the connected devices.
- Status LED’s in the front panel helps simple and visyual indication of the power supply out put connections and detecting some types of malfunctions.
- Automatically switches the power suppply operation to the backup battery when the main power source fails
- Upon main power’s availability(reconnection) the power supply provides automatic switchjover to main power and start recharging the backup battery.
- Optimized temprature compensated charging provides over charging protection and over disharge and overheating protection of the backup battery.
Summarize the causes of leaks in a pipeline
- Pipeline corrosion and wear
- Operation outside of design limits
- Unintentional third party damage
- Intentional damage
Failure to detect leaks can be broken into 4 loss categories
Loss of life and property
Loss of product and downtime to fix pipeline
Environmental impact
Fines and legal suits
Describe the main methods used in detection of gas and/or oil leaks in a pipeline
Physical inspection of the area Add an odorant Line flow calculations Line pressure measurement Noise detection
what is pipeline leak Physical inspection of the area
Involves walking the pipelines and looking for evidence of a leak by looking at the vegetation in the area etc.
what is pipeline leak Add an odorant
Involves walking the pipelines and looking for evidence of a leak by looking at the vegetation in the area etc.
what is pipeline leak Line flow calculations
Check if the amount received is the amount expected and if there is a difference this could indicate a leak
Does not allow for expedient detection of leaks
what is pipeline leak Line pressure measurement
Detect pressure drops at various points in the line
Allows for quicker detection
what is pipeline leak Noise detection
There is an increase in noise of the pipeline when there is a leak
Describe the main methods used in detection of gas and/or oil leaks in a pipeline
Pigging
Computer based
Computer based pipeline leak detectin
Uses pipeline modelling to assist in the detection
Allows for data gathering and analysis
Pig tracking
Back tracking of fluid
Accounting
Flow compensation
Rapid detection of leaks and quicker response
Pigging
Pigs can carry surveillance and monitoring equipment to assist in the detection of leaks
This will be covered more in the next objective.
Describe the purpose of ‘Pigging’ a pipeline.
Utility pigs – clean the pipeline of debris or seal the pipeline
Cleaning – remove solids or semi-solid deposits
Inspecting
Monitoring
Batch separation
Pipelines with butterfly valves cannot be pigged because
because the valve size is smaller than the pipe size because it creates an obstruction.
Types of pigs
Steel Urethane Urethane and neoprene Spheres (foam, solid, inflatable) Gel
AGA No. 3 and AGA No. 7
are methods of calculation gas flow.
AGA reports are used to describe
how to measure the flow of natural gas.
AGA 8 was published in
1985 and revised in 1992
AGA Report No. 7
Measurement of gas by axial-flow turbine meters
Characteristics which affect the performance of a turbine meter
Swirl - Velocity profile Fluid drag - Non-fluid drag Accuracy - Linearity Pressure loss - Min/Max flow rate Pulsation
AGA Report No. 3
Orifice Metering of Natural Gas and other hydrocarbon fluids
1985 version
Developed for pipe-tap orifice meters
1992 version
Developed only for flange-tap orifice meters
Calls for use of AGA No. 8 to calculate supercompressibility
AGA Report No. 8 – 1985 Version
Allows for variations in gas compositions
Gas analysis should fall into a range of values provided in the report.
Allows for an alternate method which uses a partial gas composition.
AGA Report No. 8 – 1992 Version
Allows for wide variations in gas compositions
Gas analysis should fall into a normal range of values or an expanded range of values.
RTUs should be able to handle multiple communication media
RS-232/RS-442/RS-485 Dial-up Microwave Satellite Radio
There are to typical network configurations for wireless telemetry radio-based systems
Point-to-point
Point-to-multi-point
Point-to-point is the
simplest set-up, one stations is setup as the master and the other is the slave to allow for data to be exchanged between two station
Point-to-multipoint is configured with
one device designated as the master until to several slave units
Polled system
Master is in total control and makes regular polls of the data (sends and receives data) to each slave in sequence
Slave responds to the master only when a request is received
Also known as half-duplex
Advantages of hal;f duplex
Data gathering is simple
No collisions can occur on the network
Link failure is easily detected
Disadvantages of half duplex
Interrupt type request from a slave requesting immediate action cannot be handled
Waiting time increases with the number of slaves
All communication between slaves have to pass through the master with added complexity
Interrupt system (Report by Exception)
Slave monitors its inputs and when a significant change is detected or a limit is exceeded the slave initiates communication to the master and transfers data
Advantages Interrupt system (Report by Exception)
System reduces unnecessary transfer of data as in polled systems
Quick detection of urgent status information
Allows slave-to-slave communication
Disadvantages Interrupt system (Report by Exception)
Master may only detect a link failure after a period of time and only when system is polled
Operator action is needed to have the latest values
Collision of data may occur and may cause delay in the communication
Store and Forward
Store and Forward is a technique that simply adds an intermediate device between the source and destination communication device so that it keeps information (store) until such time that it can be sent on to the final destination, to another intermediate device (forwarding).
Used to accommodate changes in physical link or data link connectivity or if there is intermittent connectivity
Mailbox Method
Message frames are simply stored in the intermediate device in a queue until such time as the destination device becomes available
Intermediate Memory Method
Intermediate device decodes the information out of the message frame and stores it in application memory for future retransmission.
Allows the information to be retransmitted using a different data link in addition to a different physical link.
Allows for data consolidation, increasing the overall efficiency of communication
Query and Response
The entity asking the questions (query) is the MTU and the entity providing the answers(response) is the RTU
Media Access Control
Generic term for a technique within a communication protocol that permits or denies access to the physical communication medium
Prevents more than one entity from trying to communicate over the same media simultaneously
Master and Slave
Simple communication protocol technique by which the query and response cycle as well as media access control are implemented together
There can only be a single master device, but there can be multiple slave devices
Only the master device can initiate a query
The slave devices can only respond to a query directed to it by the master
Describe Satellite communication methods
Satellite – fixed services (point-to-point) provide microwave radio technology, consists of two main components, the ground segment which is a fixed or mobile transmission, reception, and ancillary equipment and the space segment which is the actual satellite
Describe Microwave communication methods
Microwave – transmitting data over radio waves whose wavelengths are measured in small numbers of centimetre
Describe Microwave communication methods
Wider bandwidth Faster data speeds Multiple links allow for redundant paths Usually has Txfer/Rxfer redundancy Higher Cost
Describe radio serial communication methods
Radio – common means of communicating with remotes using either UHF/VHF or spread spectrum
Advantages Radio
Low power consumption
Installed inside the RTU/PLC cabinet
Low operating costs
Disadvantages Radio
High development costs
Costly if over a wide area and no existing system is present
Slow data speeds
Ultra high Frequency (UHF)/Very High Frequency (VHF)
most common and is very reliable and licensing is not required
Spread Spectrum
a signal is generated with a particular bandwidth and spread in the frequency domain which gives a signal with a wider bandwidthinterference immunity and there is no licensing
Leased Line and Fiber Optic
One of the more common communications methods
Dedicated leased lines, or dial-up lines through the Public Service Telephone Network
Available bandwidth is very much dependent on the communications companies
Provide reliable communications at up to 38.6 kbps
Implementation cost for leased lines is minimal, however there are monthly leasing costs
Leased lines are highly reliable but are subject to occasional line break, they can often be subject to interference from various environmental conditions such as ice and flooding etc.
