SCADA SYSTEM IMPLEMENTATION PROCEDURES
What are the different ways in implementing the SCADA system?
What are the different ways in implementing the SCADA system?
There are many different ways in which SCADA systems can be implemented. Before a SCADA or any other system is rolled out, you need to determine what function the system will perform. Depending on whether you are a utility company or a telecommunications provider, you have a number of options in creating your systems.
There may be a need to employ different methods that are complimentary to each other. The way in which SCADA systems are connected can range from fiber optic cable to the use of satellite systems. The following sections will present some of the common ways in which SCADA systems are deployed.
Twisted-Pair Metallic Cable
Twisted-pair telecommunications cable is the most popular medium used by utilities and has existed in its present form for many years. The cables are essentially the same as those used by the Telephone Company and contain a number of pairs of conductor.
Twisted-pair telecommunications cable is the most popular medium used by utilities and has existed in its present form for many years. The cables are essentially the same as those used by the Telephone Company and contain a number of pairs of conductor.
Coaxial Metallic Cable
Coaxial cable is constructed of a center copper conductor, polyvinyl chloride (PVC) insulation, a braided or extruded copper shield surrounding the center conductor and PVC insulation, and a plastic jacket cover. Coaxial cable can transmit high frequency signals up to several MHz with low attenuation compared to twisted pair wires used for telephone service. Methods of installation used for existing systems in Europe and the USA are underground, direct burial, overhead, and on existing power line structures.
Coaxial cable is constructed of a center copper conductor, polyvinyl chloride (PVC) insulation, a braided or extruded copper shield surrounding the center conductor and PVC insulation, and a plastic jacket cover. Coaxial cable can transmit high frequency signals up to several MHz with low attenuation compared to twisted pair wires used for telephone service. Methods of installation used for existing systems in Europe and the USA are underground, direct burial, overhead, and on existing power line structures.
Fiber Optic Cable
Optical fibers consist of an inner core and cladding of silica glass and a plastic jacket that physically protects the fiber. Two types of fibers are usually considered: multi-mode graded index and single-mode step index fiber. Single-mode fiber supports higher signaling speeds than the multi-mode fiber due to its smaller diameter and mode of light propagation. Communication services usually supported by optical fiber include voice, data (low speed), SCADA, protective relaying, telemetering, video conferencing, highspeed data, and telephone switched tie trunks. Optical fiber cables have similar characteristics to twisted-pair communications cables in that aluminum tape or steel-wire armors and polyethylene outer jackets can protect them. However, the inner core is constructed to accommodate the mechanical characteristics of the fibers.
Optical fibers consist of an inner core and cladding of silica glass and a plastic jacket that physically protects the fiber. Two types of fibers are usually considered: multi-mode graded index and single-mode step index fiber. Single-mode fiber supports higher signaling speeds than the multi-mode fiber due to its smaller diameter and mode of light propagation. Communication services usually supported by optical fiber include voice, data (low speed), SCADA, protective relaying, telemetering, video conferencing, highspeed data, and telephone switched tie trunks. Optical fiber cables have similar characteristics to twisted-pair communications cables in that aluminum tape or steel-wire armors and polyethylene outer jackets can protect them. However, the inner core is constructed to accommodate the mechanical characteristics of the fibers.
Power Line Carrier
Power Line Carrier (PLC) was one of the first reliable communications media available to electric utilities for critical communications channels that could not be subjected to the intolerance and unreliability of leased (common carrier) telephone circuits. PLC uses the power transmission lines to transmit radio frequency signals in the range of 30 kHz to 500 kHz. The physical security of this communications is very high since the power line carrier equipment is located within the substations. PLC systems are used to provide voice, telemetry, SCADA, and relaying communications on portions of the 220/230 kV, 110/115 kV, or 66 kV interconnected power transmission network.
Power Line Carrier (PLC) was one of the first reliable communications media available to electric utilities for critical communications channels that could not be subjected to the intolerance and unreliability of leased (common carrier) telephone circuits. PLC uses the power transmission lines to transmit radio frequency signals in the range of 30 kHz to 500 kHz. The physical security of this communications is very high since the power line carrier equipment is located within the substations. PLC systems are used to provide voice, telemetry, SCADA, and relaying communications on portions of the 220/230 kV, 110/115 kV, or 66 kV interconnected power transmission network.
Satellites
The use of satellites has been investigated for a number of years. The satellites are positioned in geo-stationary orbits above the earth’s equator and thus offer continuous coverage over a particular area of the earth. Satellites contain a number of radio transponders which receive and retransmit frequencies to ground stations within its “footprint,” or coverage, on the earth’s surface. A network facility on the ground tracks and controls the satellite. Earth stations are comprised of an antenna pointing at the satellite, a radio transceiver with a low-noise amplifier, and baseband equipment. Satellites use both the C-band and the Ku-band. Very Small Aperture Terminal (VSAT) technology has advanced to the point where a much smaller antenna (down to about one meter) can be used for Ku-band communications. This has resulted in the Ku-band being preferred for sites with modest communications requirements. VSAT technology is advancing steadily, and the capital costs have dropped substantially. Continual time-ofuse charges must be considered in the use of satellite communications.
The use of satellites has been investigated for a number of years. The satellites are positioned in geo-stationary orbits above the earth’s equator and thus offer continuous coverage over a particular area of the earth. Satellites contain a number of radio transponders which receive and retransmit frequencies to ground stations within its “footprint,” or coverage, on the earth’s surface. A network facility on the ground tracks and controls the satellite. Earth stations are comprised of an antenna pointing at the satellite, a radio transceiver with a low-noise amplifier, and baseband equipment. Satellites use both the C-band and the Ku-band. Very Small Aperture Terminal (VSAT) technology has advanced to the point where a much smaller antenna (down to about one meter) can be used for Ku-band communications. This has resulted in the Ku-band being preferred for sites with modest communications requirements. VSAT technology is advancing steadily, and the capital costs have dropped substantially. Continual time-ofuse charges must be considered in the use of satellite communications.
Leased Telephone Lines
Leased telephone circuits have long been used to meet communications needs. Most organizations use standard telephones connected to the Public Switched Network (PSN) for office communications and for routine voice traffic to stations. Leased dedicated circuits are used for dedicated communication requirements, such as telemetry and SCADA. Wideband channels may be available for high speed data signaling. Circuit characteristics can often be conditioned for many other uses, including voice and various types of low and medium speed data.
Leased telephone circuits have long been used to meet communications needs. Most organizations use standard telephones connected to the Public Switched Network (PSN) for office communications and for routine voice traffic to stations. Leased dedicated circuits are used for dedicated communication requirements, such as telemetry and SCADA. Wideband channels may be available for high speed data signaling. Circuit characteristics can often be conditioned for many other uses, including voice and various types of low and medium speed data.
Very High Frequency Radio
by utilities for mobile radio, although point-to-point links have been implemented in this band. Advances in data transmission on mobile radios have been made, particularly for joint voice and data use, such as in taxi and police dispatching systems. Such systems could be used for maintenance vehicle dispatching. SCADA systems can use adapted VHF radios for communications; however a SCADA system would need exclusive use of the frequencies. Frequency assignments in this band are usually reserved for mobile services.
by utilities for mobile radio, although point-to-point links have been implemented in this band. Advances in data transmission on mobile radios have been made, particularly for joint voice and data use, such as in taxi and police dispatching systems. Such systems could be used for maintenance vehicle dispatching. SCADA systems can use adapted VHF radios for communications; however a SCADA system would need exclusive use of the frequencies. Frequency assignments in this band are usually reserved for mobile services.
Ultra High Frequency Radio
The Ultra High Frequency (UHF) band extends from 300 to 3000 MHz. The bands typically considered for UHF radio are in the 400 MHz and 900 MHz range. Most of the suitable radio products for SCADA applications available in the U.S. operate in the 900 MHz frequency range. In the U.S., the Federal Communications Commission (FCC) regulates the use of radio frequencies and has designated the 928 to 952 MHz range specifically for use by utilities for data communication applications. These UHF systems can be Point-To-Point (PTP), Point-To-Multipoint (PTM), Trunked Mobile Radio, or spread spectrum systems. The PTM systems are also referred to as Multiple Address Radio Systems (MARS). Spread spectrum systems are the basis for many wireless applications including 802.11 a/b/g networks. These types of UHF systems are described in the following subsections.
The Ultra High Frequency (UHF) band extends from 300 to 3000 MHz. The bands typically considered for UHF radio are in the 400 MHz and 900 MHz range. Most of the suitable radio products for SCADA applications available in the U.S. operate in the 900 MHz frequency range. In the U.S., the Federal Communications Commission (FCC) regulates the use of radio frequencies and has designated the 928 to 952 MHz range specifically for use by utilities for data communication applications. These UHF systems can be Point-To-Point (PTP), Point-To-Multipoint (PTM), Trunked Mobile Radio, or spread spectrum systems. The PTM systems are also referred to as Multiple Address Radio Systems (MARS). Spread spectrum systems are the basis for many wireless applications including 802.11 a/b/g networks. These types of UHF systems are described in the following subsections.
Microwave Radio
Microwave radio is a term used to describe UHF radio systems operating at frequencies above 1 GHz, although multi-channel radio systems operating below 1 GHz are sometimes referred to as microwave systems. These systems have high channel capacities and data rates, and they are available in either analog or digital transmission technologies. Analog transmission was the first microwave technology available. It is the most mature method of transmission.
Microwave radio is a term used to describe UHF radio systems operating at frequencies above 1 GHz, although multi-channel radio systems operating below 1 GHz are sometimes referred to as microwave systems. These systems have high channel capacities and data rates, and they are available in either analog or digital transmission technologies. Analog transmission was the first microwave technology available. It is the most mature method of transmission.
source: National Communication System, Technical Information Bulletin 04-1
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