Central Control Room with Host Computers/workstations/Task servers .
Multiple Remote Terminal Units (RTUs) or Programmable Logic Controllers (PLC)
SCADA SYSTEM COMPONENTS
DAC: overview Load Despatch Control Centre Generation: Data & Control Transmission Transmission: Data & Control Generation Power Plant Boiler Turbine Generator Substation Switchyard Trans former Breaker CT, PT, CVT, Optical sensor Power plant Control Room
The main task of the load dispatcher is to ensure quality and reliable power at an economical rate. To fulfill this commitment, LD must have upto date and reliable information of power stations and important EHV sub-stations under control.
Now a days with the increasing capacity of the integrated power system day by day, the complexity has also increased and controlling and monitoring of the power system has become a cumbersome task due to dynamic variations of system parameters such as active power, reactive power, voltage, frequency etc. which needs close monitoring .
SCADA is the powerful tool to monitor the system parameters in real time mode and give readymade solutions to LDs for taking corrective measures to maintain stability/ security.
Major Applications of SCADA for Power System Management
Substation Automation & Controls
RTU 1 RTU 2 RTU 21 SCADA SYSTEM AT ALDC AMBAZARI SCADA SYSTEM AT SLDC KALWA RTU 1 RTU 2 RTU 44 EMS SYSTEM WRLDC 64 KBPS Leased line 200 Baud PLCC Links 200 Baud PLCC Links
S upervisory C ontrol A nd D ata A cquisition Overview of SCADA System MPEB GEB GOA DC DC Sinaut Spectrum SCADA, Kalwa Sinaut Spectrum SCADA, Ambazari 13 RTU’s GPS . . Sinaut Spectrum EMS MMI Chandrapur – Padge HVDC SCADA TCI1 TCI2 ICCP1 MMI COM ADM .. ICCP2 . . . . . . . . . ICCP1 ICCP2 TCI1 TCI2 MMI COM ADM . . . . . . . . . .. Data Links 2 X 64 Kbps . . ULDC SCADA at WRLDC ICCP 6 x 64 Kbps OPF Link 9 IEC RTUs 1 IEC RTU Ethernet Hub / Switch Ethernet Hub / Switch . . . . . . . . . GPS 26 RTUs 4 Nos . 10 RTUs 7 RTU’s CSEB NA GCS MMI
Real time Data Requirements at LD Centre • Analog measurands • Active power MW • Reactive power MVAR • Current amps • Bus Voltages • Frequency • Transformer tap positions • Status Indications • CB • Isolator • Alarms • CB Trip • Bus protection • Station Battery failure • Communication failure Above data for own Network elements, interstate tie lines and important neighbouring state elements
S upervisory C ontrol A nd D ata A cquisition Highlights of SCADA system ➲ Sinaut Spectrum SCADA functions are distributed among 64 Bit, RISC, SUN Ultra 10 Servers on LAN. ➲ 10 Nos. of IEC RTU are integrated in the system ➲ System supports Sinaut 8FW RTU protocol as well as internationally accepted IEC -870 - 5 -101 protocol. ➲ ICCP protocol based on international standards for data exchange between SLDC, Kalwa and ALDC, Ambazari as well as RLDC, Marol ➲ Huge memory capacity, faster speed and response. ➲ 200 % additional capacity for future expansion The Front End processor is capable of acquiring data from 35 Direct RTUs, However, with the usages of Data Concentrator 560 RTUs can be connected to each system.
SCADA System Set up SCADA and EMS SCADA DCs - 4 RTUs IEC–101 Sinaut 8FW RTUs IEC–101 Sinaut 8FW ICCP with PGCIL ICCP on 64 Kbps PLCC Communication Transducers Relays
SCADA Architecture for Control Centres WRLDC TPC & REL Protection Alarms from Numerical Relays GPS 2MBps Links ICCP Links IED IED Transducers
SCADA Functional Requirements • Data Acquisition FEPs, cyclic, spontaneous, Renewal Check old/new comparison, I/ state suppression,Plausibility Check,threshold • Data Processing Measured values, statuses,alarms • Analog value Gradient, limit check, sum, quality flag etc . • Logic operations Calc. rules using logic & functional operators . • Supervisory control Single & sequence switching, Check, interlockings • Tagging Manual updating , Notes for tag • Sequence-Of-Events (SOE) time stamp (msec) at RTU, Buffer • Data storage Archive duration and a storage period , modifications • Data Retrieval Query based application • Disturbance Data Pre- and post-disturbance conditions. ‘ Post Mortem’ • Disturbance triggers Excessive ACE, Freq diff., CB trip, combinations • SQL interface Operational planning, reporting, Excel • Data Exchange With other Control Centres , RDBMS Oracle
RTU Features • Modular, open and technology-independent system structure • Multi-processor system • Binary I/O cards suitable for up to 220VDC interface • Online parameter modification • LED's for indications of all process- and operating conditions • Secured internal communication • Storage of all parameters, configuration • Periodical & Spontaneous processing • time-stamping • Prioritization of Messages • Archiving of data • IEC61850 communication protocol with IEDs • IEC60870-5-103, MODBUS, or DNP3 protocols • High EMC • IEC 101/104 protocol • Auxiliary Supply 48 VDC • data transmission rates from 50 to 38400 bits per second • Support Local MMI over IEC-103 or 61850 • Local User Maintenance Interface
RTU Functions • communication with IEDs using selection of protocols • communication with Master station • General Interrogation Response • Exception Reporting • Message Security • collect analog data • acquire status indications • Sequence Of Event (SOE) Collection • Digital Control Output to field devices Two-state devices, Variable Output Devices • Internal Clock , GPS synchronisation • Availability • Expandability • Maintainability • Life span
SCADA Architecture • Main Backup Configuration disaster management • Dual LAN Configuration • Multisite operation uniform database • Functional Distribution • Redundancy for critical functions • Communication with other Control Centres over ICCP • System Security Firewall • Access Rights user & workstation specific • Online database modifications Test & implement • Remote MMI support • Expandable • Maintainable • High availability • Life Span
User interface Requirements • SLD Display system guide user • Window Environment overlapping multiple windows • Each window supports max min resize menu bar scroll • Panning , Zooming and decluttering • Operator Alarming audible, flashing • Snapshots • Topological Network Coloring de-energised, grounded • Curve Displays and Trending • Help Function • Summaries General, message, system, acknowledge • Notes attached to system elements, Edit store & retrieve • Tabular Displays real time and archieved values • Logs and Reports Periodic,predefined time • Report generation system Modifications, activation events,combination • Hard and soft copies
Software & Hardware Requirements • Administration and diagnostic tools performance, simulation • Time synchronization GPS, Master to all servers • Automatic system re-start/changeover Fault detection, errors,watchdog • Open System Standards • Operating System IEEE Posix Compliant • Application Software C, C++, Java ANSI Standards • Full Graphic User Interface Online data activation , Multi user sessions Undo, Logs, global figures • Servers single family • Workstations UI • TFT Monitors • Hard Copy Devices B/w Color • Cartridge Tape Units 40GB • LAN Switches • Video Projection System • Remote Terminal Units • Data Concentrators • Bay IEDs • Transducers • Local MMI • RTU Maintenance Tool • Comm. Interfaces Hardware At LD Centres At Substations
SCADA is a prerequisite for EMS (Energy Management System) which offers several powerful functions to ease the power system operations, to raise the system security and to facilitate the personal training. All these functions serve to reach the most efficient operations as quick as possible .
SCADA system can be extended by following EMS servers
Network Analysis (NA)
Generation Control & Scheduling (GCS)
Dispatcher Training Simulator (DTS) & Power System Simulator (PSS )
Network analysis functions such as State estimator, on-line load flow calculation, on-line short circuit calculation, contingency evaluation etc. forms an integral part of the network control system in many power utilities.
Proven to be useful aids in operational management of network enabling the timely detection of work points in the network and as decision making aids in difficult situations.
Functions of NA Server Basic functions NA Sequence control NA operation/display routines Case Management External Network modeling Network Status processor Bus scheduler State estimator On-line Load flow Penalty factor calculation On-line Short-circuit Contingency evaluation Optimal power flow Voltage/Var scheduling Voltage/Var dispatch Emergency Constrained dispatch Active power Remedial action Active power Remedial action LAN
The purpose of Generation Control & Scheduling (GCS ) server is
Frequency maintenance & observations of contracts by optimized generation dispatch
Minimization of generation costs
Calculation of demand
Observation of generation costs in comparison with optimized costs
Definition & control of interchange contracts
Wheeling loss calculation
GCS Server Schedule Management System Unit commitment Hydro unit calculation Hydro thermal coordination Water worth Value calculation Interchange Transaction Evaluation Short term Load forecasting Reserve Monitor Economic Dispatch Production costing Interchange Transaction Evaluation Data Acquisition & Control Interchange scheduling Automatic Generation Control AGC Performance Monitor Energy Accounting Historical Data Management Man Machine Interface
Applications and data of interest may include remote access to IED/relay configuration ports, waveform, event data, diagnostic information, video for security or equipment status assessment, metering, switching, volt/VAR management, and others.
Newer microprocessor based relays and other intelligent devices have interfaces such as DNP 3.0 over TCP/IP/Ethernet. Additionally, more utilities are gaining access to fiber optic based communication and /or IP Wireless communication at sub-stations which can greatly enhance sub-station automation possibilities and benefits.
The functional features for Expert System covers all state of the art functionality for following packages
Intelligent Alarm Processor (IAP)
Power System Restoration (PSR)
The Expert System operates in a real time environment and covers on line processing of real time data and IAP as well as automatic creation and update of knowledge base. The PSR is a model based hybrid expert system combining rules and algorithm. PSR supports the load dispatcher sufficiently in case of emergency.
IAP PSR Interlock Fault Identification/ Diagnostic Comments/ Advices/ Switching Sequence User Interface SCADA SYSTEM Input data O/P Report List O/P Report List O/P Result Expert System
Intelligent Alarm Processor (IAP) : This on line tool produces automatically a diagnosis when a fault event occurs in the Energy Network. Typically a fault event creates an alarm inrush and the system operator would have to look up at up to hundreds of alarm messages. Therefore IAP provides information about the fault location in case of network disturbance. It informs to operator the nature and the consequences of the disturbance quickly and exactly.
Input : The input data for IAP that comes from the SCADA for correct output (diagnosis )is :
The topology of the network
The alarms from the automatism
Logical working schema of the automatism.
Output (Diagnosis ) :
The date & the time of disturbance
The faulty equipment (transformer, line, bus bars)
The protection system which clears the fault.
Additional information (e.g. breaker failure, automatic recloser successful / unsuccessful etc. )
The report list shall be invoked on the Basic Signaling Display.
2 ) Power System Restoration (PSR) : This on-line tool, considering all the situations occurring during a power system partial or complete break down, presents restoration plan in all possible scenario. It generates the switching sequence automatically and delivers instructions in form of advices for the emergency situation and therefore :
Avoid critical situations
Assures safe network operation
Gives complete assistance when unexpected critical event occurs
Now let us highlight the major advantage of integration of real time Expert System in SCADA, that could have averted blackout on dt 09.11.2007 in Marathwada area of MSETCL Power System considering the following Case Study.
Date : 09.11.2007 Time : 17:26 Hrs . Total Load shedding Withdrawn Being Diwali. The load of Marathwada Area To the tune of 1200 MW was being catered from following Sources : Total Parly Gen.: 750 MW Loading on Both 400/220 KV 315 MVA ICTs at Giravali s/s : 330 MW (560 Amps) 220 KV Pusad-Parbhani Ckt: 55 MW 220 KV Pusad-Nanded Ckt.: 125 MW NORMAL STATE Advice from Expert System : Watch out for any Gen. loss and ready for implementing conglomerated Load Management Plan for evening peak demand management.
Time : 17:27 Hrs Total Parly Gen.reduced to 570 MW Due to withdrawing of Parly Unit 5. Loading on Both 400/220 KV 315 MVA ICTs at 400KV Girawali s/s reached to: 430 MW (800) Amps ALERT STATE
Advice from Expert System :
Shift the load of 220 KV Dhamangaon s/s being catered from 220 KV Wardha s/s on 220 KV Amravari s/s thus making 220 KV Wardha a strong source for catering the load of 220 KV Pusad s/s.
Shift total load of 220 KV Parbhani s/s on 220 KV Pusad s/s OR shift partial load of Nanded s/s on 220 KV Pusad s/s.
And Likewise steps for reducing the loading on both ICTs at Girawali s/s.
Time : 18:17 Hrs Overload alarms on both ICTs occurred. Stage I alarm occurred at 95% of Full load Stage II alarm occurred at 105% of Full load Time : 18 : 23 Hrs Parly Gen. Unit 6 tripped. Total load on both ICTs reached to 1080 Amps. CRITICAL STATE Advice from Expert System : Carry out Distress load shedding in Nanded, Parbhani, Harangul area to the tune of 200 Amps to control the loading
TOTAL COLLAPSE Time : 18:28:20 Hrs Both 315 MVA ICTs tripped at 400 KV Girawali s/s Causing tripping of remaining gen. units at Parly TPS. Time : 18:30 Hrs 220 KV Pusad, Nanded, Parbhani s/s in dark. Affecting about 1200 MW load in Marathwada area DISTURBANCE Advice from Expert System : Advice for management for remaining existing loads. Switching Sequence for quick restoration
Thus it can be very well seen that integration of real time Expert System in SCADA could have possibly averted such and similar types of partial / complete blackouts by advising load dispatcher through set of instructions / switching sequences, technical support etc under such emergency condition, and avoiding total load throw off to the tune of 1200 MW, a huge revenue loss to the company, law & order problems & as well as embarrassment to the company.
Conclusion . It is emphasized that SLDC institution, which is apex body for the grid operation in the state in coordination with RLDC, has an important and increasing role in operating the State Grid in an economic, reliable and secure manner and maintain coordination with the RLDC and all users of the grid within the State . To take correct decisions from Real Time System up-dation SCADA-EMS is necessary