Communication Systems in Power Applications

1. Communication SystemsinPower Applications

2. Overview • Introduction • Communication Needs of Power System • Communication Technologies • Existing Communication Systems • Challenges • Future Trends

3. Introduction • Communications is the enabling technology for Power System • No single communication technology as being best suited for all power system needs • Requirements must consider type, source, amount, frequency, and delivery requirements of data/voice transmitted

4. Communication Needs of Power System • Reliability • Cost effectiveness • Capacity to handle data rates • Adequate to meet response requirements • Ability to reach identified areas of power system • Ease of operation and maintenance • Security (of data and of control actions)

5. Communication Reliability Reliable communication with respect to: • Exposure to severe environment • Electromagnetic Interference (EMI) • Transient EMI (lightning, faults) • Outage of transmission lines • Power outages • Radio paths obstructed or attenuated (by buildings or foliage)

6. Cost Effectiveness • Communication system costs are significant • High cost of communication system may become an impediment • Evaluate both first cost and lifetime operation and maintenance costs • Look for best trade-off between total costs and overall performance

7. Capacity to handle data rates • Perform data rate audit of present & upcoming schemes • Analyze each function • Determine bit rate required to perform the function • Consider worst case scenarios • Each communications system has a bandwidth limit • There should be at least enough bandwidth along each path to meet data requirements • A good margin allows for future growth and increased system flexibility

8. Ability to meet response requirements Response requirements (measured in sec.) are distinct from data rate requirements (measured in kb/s or Mb/s), and must be met independently. Different functions have vastly different requirements for the delivery of the information; for example:

9. Ability to Reach Areas of Power System • Difficult Terrain • Communications that rely on the power line may have difficulty • During outage of line • Extreme weather conditions • Terminal equipment in outage areas may require backup power for long durations

10. Ease of Operation and Maintenance • A communications system is a complex combination of transmitters, receivers, and data links • Manpower not trained and not familiar with communications equipment • Personnel trained for new skills involved ? • New tools acquired ? • Use standardized components and communication protocols

11. Security of data and control actions Power System communication Data & Voice have critical importance. Communication security is a necessity.

12. Security of data and control actions Your substations are an element of the country’s critical infrastructure – are you sure that you are in complete control?

13. Security of data and control actions Maintaining the security of communications between the control center and field devices is one of the most urgent problems facing today’s control environment.

14. Communication Technologies

15. Power Line Carrier Communication(PLCC) • Power Lines used for point to point communication • Terminal equipments used to send/receive data/voice • Works on audio band width 20 to 20 KHz • Carrier 30 KHz to 500 KHz

16. CKT-I E/W E/W R Typical PLCC Arrangement for S/C LINE PHASE-GROUND COUPLING R Y Y B B CVT/CC CVT/CC CD CD PLCC PLCC PLCC PLCC

17. Coupling Types in PLCC System • Line Trap, Coupling Device & CC/CVT known as Coupling Equipment • CD consists of Surge Arrester, Drain coil, Matching transformer, Earth switch • Functions of Coupling Equipment -Inject carrier signal to EHV line without loss -Decouple carrier equipment from EHV line

18. PLCC---Uses • Voice communication • Tele-control • Tele-protection • SCADA data from RTU

19. PLCC---Pros • Easy availability • Cost effective • Ease of operation & maintenance

20. PLCC--- Cons • Limited bandwidth(4 KHz) • Data speeds up to only 1200 Bauds possible • Prone to Noise & Interference • Effect of weather conditions-frost, high pollution etc • Depends on physical connectivity of power lines • Needs government approval for carrier freq selection • Not suitable for today’s needs of automation like SAS, remote control etc.

21. Fiber Optic Communication Fiber optic cable functions as a "light guide," guiding the light introduced at one end of the cable through to the other end. The light source can either be a light-emitting diode (LED) or a laser. Using a lens, the light pulses are funneled into the fiber-optic medium where they travel down the cable. • The light (near infrared) is most often are used : • 850nm for shorter distances • 1300nm for longer distances on Multi-mode fiber • 1310-1320nm for single-mode fiber • 1,500nm is used for longer distances.

22. Fiber Optic Communication(Contd..) • Two types of fibre- Multi mode > 50micron core– Upto 2 Kms Single mode < 10 micron core—more than 20 Kms • Selected on the basis of distance & bandwidth needs • Wave Division Multiplexing Used

23. Fiber Optic (Contd..)Pros: • Fast becoming common in utilities for voice and data transmission • Offer many advantages • extremely high data transmission rates • immunity from electromagnetic interference • Free from licensing requirements • Cost effective for very high data transmission rates in a point-to-point configuration

24. Fiber Optic (contd..)Cons • Not as cost effective for applications, with • point-to-multipoint configuration • Modest data transmission speed requirements • Prone to cable cut in underground configuration • Repair & restoration specialized work

25. VSAT Communication Geo-synchronous satellite 36,000 km Earth Station User site

26. VSAT(contd..) • Very small aperture terminals (VSATs) used for EMS/DMS • For data comm. most frequently uses a shared channel, to lower costs • Communications routed through a third-party network management center SATELLITE NETWORK MANAGEMENT CENTER UTILITY CONTROL CENTER SHARED HUB VSATs

27. VSAT (contd..) • Various frequency bands: • C-band (4/6 GHz), Ku-band (12/14 GHz),Ka-band(30/20 GHz) • Advantages • Near-universal coverage • Good reliability • Fast installation • Disadvantages • Cost • Transmission delays • Blackout periods due to eclipses • Attenuation in heavy rain (Ku band)

28. Mobile Communication • Several competing technologies • Use of control channel on analog AMPS (Advanced Mobile Phone Service), 800 MHz • CDPD (Cellular Digital Packet Data) • The field is rapidly evolving (“2G”  “”3G”) • Currently, most applications are for AMR • Recently also being offered for applications in feeder automation • Potentially holds the promise of economical and wide-spread coverage

29. Tele-Control Protocols • IEC 60870-5-101 protocol (from RTU to Control Center communication • IEC 60870-6-502 ( ICCP) protocol (between two Control Canters) • IEC 60870-5-103 protocol (for communication between IEDs in a Substation) • IEC 60870-5-104 protocol • MODBUS Protocol ( MFTs) • DNP 3.0 Protocol (Serial)---Master Station • DNP 3.0 Protocol (TCP/IP)---Master Station • IEC 61850 protocol (for Substation Automation)

30. Tele-Control Protocols • The Present SCADA systems use • IEC 60870-5-101 for data acquisition from RTUs/SAS • IEC 60870-6-502 for data exchange between control centres

31. IEC–60870–5-101 Physical Layer : Information bit : 8 bit Stop bit : 1 Parity bit : Even Unbalanced Request Message (User Data, Confirm Expected) Data Link Layer Standard Frame Format : FT 1.2 Maximum Frame Length : 255 bytes [P] [S] Slave Master Transmission Layer ( Station address field Length : 1 or 2 bytes ) Unbalanced Mode : Transmitted messages are categorized on two priority classes( Class 1 & Class 2 ) Balanced Mode : All the messages are sent, No categorization of Class 1 and Class 2 (Acknowledgment) Response Message [P] Network Layer : Not defined as 870-5-101 is not IP based Selection of ASDUs ASDU 1 : Single point information ASDU 2 : Single point information with time tag ASDU 3 : Double point information ASDU 4 : Double point information with time tag ASDU 9 : Measured value, Normalised value ASDU 10 : Measured value, Normalised value with time tag ASDU 11 : Measured Value, Scaled value ASDU 12 : Measured value, Scaled value with time tag ASDU 100 : Interrogation Command ASDU 103 : Clock Synchronisation Command ASDU 120 - 126 : File transfer Command (Request User Data) Application Layer The length of the header fields of the data structure are: Station address 1 or 2 byte ( User defined ) ASDU Address : 1 or 2 bytes Information Object address : 2 bytes Cause of Transmission : 1 byte [S] (Respond User Data or NACK) [P] = Primary Frame [S] = Secondary Frame

32. ICCP Protocol Associations An application Association needs to be established between two ICCP instances before any data exchange can take place. Associations can be Initiated, Concluded or Aborted by the ICCP instances. Bilateral Agreement and Table, Access Control A Bilateral Agreement between two control-centers (say A and B) for data access. A Bilateral Table is a digital representation of the Agreement. Data Values Data Values are objects that represent the values of control-center objects including points (Analog, Digital and Controls) or data structures. Data Sets Data Sets are ordered-lists of Data Value objects that can be created locally by an ICCP server or on request by an ICCP client Information Messages Information Message objects are used to exchange text or other data between Control Centers. Transfer Sets Transfer Set objects are used for complex data exchange schemes to transfer Data Sets (all elements or a subset of the Data set elements) etc. Devices Devices are the ICCP objects that represent controllable objects in the control center.

33. ICCP Protocol(Contd..) Conformance Blocks ICCP divides the entire ICCP functionality into 9 conformance block subsets. Implementations can declare the blocks that they provide support for, thus clearly specifying the level of ICCP supported by the implementation. Any ICCP implementation must necessarily support Block 1ca Block 1 – Basic Services Association, Data Value, Data Set, Data set transfer Block 2 – Extended Data Set Condition Monitoring Data Set Transfer Set Condition Monitoring Object Change condition monitoring, Integrity Timeout condition monitoring Block 3 – Blocked Transfers Transfer Reports with Block data Block 4 – Information Message Information Message objects, IMTransfer Set objects Start Transfer Stop Transfer Data Set Transfer Set Condition Monitoring Block 5 – Device Control Device objects Select, Operate, Get Tag, Set Tag, Timeout, Local Reset, Success, Failure Block 6 to Block 9 are not generally implemented

34. Communication Channel for Information flow RLDC Wide Band Commn (MW / FO) Wide Band Commn (MW / FO) SLDC SLDC Wide Band Commn Wide Band Commn Sub-LDC Sub-LDC Wide Band / PLCC Commn RTU RTU RTU

36. RTU RTU SCADA : Data communication architecture TFE computer TFE computer TFE computer TFE computer TFE computer Panel Multi-port Stallion Adapters Panel multi-Port Stallion adapters Splitter Modem Modem Modem Modem Modem Modem Modem Modem RTU

37. INTER-SITE communications • Protocol management • ICCP within Open Access Gateway • Data acquisition and transfer to other center(s) • Indirect remote control (from / to other control centers) SCADA/ ICCP Server ICCP Other Sites/ICCP Server

38. RTU Connectivity Critical RTU Normal RTU LAN-B LAN-B LAN-A LAN-A CFE CFE CFE CFE S M M M M M M RTU RTU

39. Interface for RTUs reporting to Control Centre Through PLCC LINK . Control Centre RTU Location Data (FSK) Data (FSK) Modem PLCC PLCC Modem Analog Analog Modem RTU Modem Modem speech speech

40. Interface for RTU reporting to Control Centre via Tandem PLCC/Wideband Link & Wideband Links RTU Location Wideband Node Data(Fsk) Data(Fsk) Modem PLCC PLCC Analog Analog RTU Speech Primary Mux 1 2 3 -- - 29 30 Control Centre Speech Speech 1 2 3 -- 28 29 30 Primary Mux Radio Radio Require Modem Modem Modem 64 kbps Sub Mux Radio Link Sub Mux Modem 4 x E-1 4 x E-1 RTU at Wideband Node

41. RTU Through MICROWAVE RTU RADIO TX / RX MUX RADIO TX / RX CFE MUX MUX RTU Through FIBER OPTIC SYSTEM RTU MUX OLTE OLTE MUX CFE CONTROL CENTRE SUBSTATION/ GEN STN SIDE

42. Popular communication technologies in Indian Power systems: Technology %Usage • Power Line Carrier 50 • Analog/digital Micro wave 15 • Fiber Optic 30 • GSM/GPRS <1 • V-sat 5

45. Challenges • Indian Power networks growing faster, larger & more complex. • Data communication needs to be much faster catering to smart grid initiatives being taken up. • With faster, smarter & innovative technologies, data security to be addressed adequately. • All radio communication to be replaced with fibre optic network by Dec.,2011 as per GOI decision.

46. Future Trends • Smart grid technologies driving communication needs. • High speed fibre optic networks need of the hour. • Increasing use of internet as the mechanism for data communication. • Main thrust on security issues with use of web based technologies. • Introduction of Service oriented architecture(SOA) will need high band width networks.

47. Future Trends (contd..) • Growing insistence on adherence to communication standards. • Possible application of cellular digital packet data radio technologies.

48. Thank You Thank You Devendra Kumar DGM,ERLDC