Integrated Power System Spreads over thousands of square kilometers Hundreds of Generating Units Thousands of Circuit Kilometers of Lines Tens of Thousands of Devices SINGLE LARGEST COMPLEX MACHINE 100% Reliability IMPOSSIBLE

NORMAL A L E R T EMERGENCY RESTORATIVE

RESTORING NORMAL SYSTEM OPERATION AS QUICKLY AS POSSIBLE SYNCHRONISING OF AT LEAST ONE UNIT AT ALL POWER STATION RESTORING ESSENTIAL LOADS ESTABLISHING ALL INTERCONNECTIONS STARTING ECONOMIC DISPATCH STARTING ALLOCATION OF C. S SHARE MINIMIZING AMOUNT OF UNSERVED ENERGY RESTORATION OBJECTIVES

IMPAIRED COMMUNICATIONS, LIMITED INFORMATION. RE-ASSEMBLING TIE ELEMENTS OF POWER SYSTEM. UNFAMILIARITY WITH THE SITUATION (DOES NOT OCCUR REGULARLY) TIME CONSTRAINTS INFORMATION TO BE FURNISHED TO AUTHORITIES- PRESSURE ON OPERATOR RESTORATION PROBLEMS

EXTENT OF BLACK OUT AND ACTUAL REQUIREMENT IDENTIFICATION OF BOUNDARIES OF ENERGISED AREAS ASCERTAINING FREQUENCY & VOLTAGE OF ENERGISED AREA STATUS OF GENERATING PLANTS(HOT/COLD/HOUSELOAD ) NON AVAILABILITY OF ELEMENTS(LC/FAULT ETC) OVERLOADING OF ELEMENTS LOADS INTERRUPTED BY UNDER- FREQUENCY RELAY OPERATION OR DIRECT TRIPPING STATUS OF BREAKERS SYSTEM STATUS DETERMINATION

 CONSIDERATION OF TIME-CRITICAL BOILER- TURBINE START-UP CHARACTERISTICS (FOR PREDOMINANTLY THERMAL SYSTEMS)  SURVIVAL POWER SUPPLY TO THE PLANTS AT THE EARLIEST WITH AVAILABLE ARRANGEMENT (DG SETS) FOR Turbine emergency oil pump.Jacking oil pumps.Barring gear of the turbine.Lubricating oil pumps.Emergency lighting.Battery charger Compressor for CB PLANT SURVIVAL AND START UP THUMB RULES

ALL DG/GT’S TO RUN TO PROVIDE START UP POWER. ESTIMATION OF TOTAL START UP POWER REQUIRED TO RUN AT LEAST ONE MACHINE OF EACH POWER STATIONS. TAKING CARE NOT TO LOAD THE GENERATOR SUPPLYING START-UP POWER BEYOND 80% OF ITS CAPACITY. RELEASING AUXILIARY POWER IN STEPS. THE CAPACITY (I.E. FAULT LEVEL) OF ISLAND (SUPPLYING START UP POWER) TO SUSTAIN- STARTING CURRENT 0F BFP ETC. TO BE CHECKED. PLANT SURVIVAL AND START UP

CLEARING ALL DE-ENERGISED BUSES GLOBAL OPENING OF ALL THE BREAKERS ELSE:-SELECTIVE BREAKER OPERATION AFTER CAREFUL CONSIDERATION SECTIONALISING A SYSTEM INTO SUB-SYSTEMS TO ENABLE PARALLEL RESTORATION OF ISLANDS AUTOMATICALLY SWITCHED CAPACITORS AND UNDER FREQUENCY RELAYS MAY HAVE TO BE KEPT OUT OF SERVICE AT THE INITIAL STAGE NETWORK PREPARATION

NETWORK ENERGISATION IDENTIFY THE IMPORTANT AND ESSENTIAL LOADS TO BE RESTORED FIRST AT EVERY STAGE WE SHOULD BE ABLE TO SATISFY –REACTIVE POWER BALANCE –LOAD GENERATION BALANCE –PROTECTION AND PLANT CONTROL SYSTEM REQUIREMENTS HVDC IMPORT – ONLY WHEN MIN FAULT LEVEL IS AVAILABLE. AVOID PARALLELING ISLANDS THROUGH WEAK LINKS THUMB RULES

NETWORK ENERGISATION PLANT CONTROL SYSTEM CHARACTERISTICS A) MECHANICAL CONSIDERATIONS REGULATION OF RATE OF CHANGE OF TEMPERATURE TO BE KEPT MANUAL CONTROL FEED WATER WITH THE SOLE OBJECTIVE OF MAINTAINING DRUM LEVEL AT SET POINT PLANTS HAVING FEED WATER REGULATING VALVES PREFERABLE TO THOSE HAVING TURBINE-DRIVEN FEED PUMPS TWO FUEL SUPPLY SYSTEMS - ONE (OR NONE) AUTOMATIC AND ONE (OR BOTH) IN MANUAL.

NETWORK ENERGISATION B) ELECTRICAL CONSIDERATIONS VOLTAGE REGULATOR TO BE SWITCHED TO AUTOMATIC CONTROL (FROM MANUAL) ONLY WHEN THE UNIT REACHES A MIN. OPERATING POINT AND A SUFFICIENT VAR GENERATION 1S ESTABLISHED PROTECTIVE RELAYS SUCH AS VOLTS PER HZ, OUT OF STEP, UNDER EXCITATION, DISTANCE, FREQUENCY & FIELD. FORCING CAN INITIATE AN UNDESIRABLE REGULATOR RESPONSE OR GENERATOR TRIP DURING START UP

NETWORK ENERGISATION STRUCTURAL SYSTEM SIZE METROPOLITAN OR RURAL COMPACT OR EXTENSIVE GENERATION TRANSMISSION VOLTAGE LEVELS TYPES AND SIZES OF LOAD BLOCKS AVAILABILITY OF INTERCONNECTION ASSISTANCE

NETWORK ENERGISATION DYNAMICS REACTIVE CAPABILITIES OF GENERATORS /SYNCHRONOUS CONDENSERS UNDER NORMAL AND EMERGENCY OPERATING CONDITIONS. SHUNT REACTOR AND CAPACITOR SIZES, LOCATIONS AND MODES OF CONTROL. CHARGING CURRENTS AND MAXIMUM SUSTAINABLE OVERVOLTAGE, TRANSFORMER REACTANCES, TAP RANGES AND MODES OF CONTROL GENERATOR MAXIMUM AND MINIMUM OUTPUTS UNDER DIFFERENT CONDITIONS

REACTIVE POWER BALANCE SOURCEGENERATIONABSORPTION GENERATOR YES LINE CHARGINGYES SHUNT CAPACITORYES SHUNT REACTORYES SYN CONDENSORYES STATIC VAR COMPENSATOR YES NETWORK ENERGISATION THUMB RULES

LOAD GENERATION BALANCE TYPE OF THE LOAD –PEAK OR OFF PEAK –COLD LOAD INRUSH GENERATOR CAPACITY MINIMUM LOADING OF GENERATOR RESPONSE TO SUDDEN LOAD PICKUP TIME ELAPSED(HOT START) NETWORK ENERGISATION

LOAD RESTORATION DURING RESTORATION EFFECT OF EACH RESTORATION ACTION ON FOLLOWING TO BE CONSIDERED –GENERATOR LOADING –TRANSMISSION LINE LOADING –LOAD ANGLE –RATE OF LOADING –RESPONSE OF THE GEN TO LOAD CHANGE –CHANGE IN SYSTEM FREQ AND OPERATION OF UFR’S –FLUCTUATING LOADS- EX. TRACTION, FURNACE ETC. THUMB RULES

RESTORATION STRATEGIES BUILD DOWN OR SEQUENTIAL STRATEGY BUILD UP OR PARALLEL STRATEGY

 RE-ENERGIZATION OF BULK POWER NETWORK BALANCED STEP-BY-STEP RESTORATION OF LOADS AND GENERATION SUITABLE FOR SMALL SYSTEMS NOT HAVING LONG EHV LINES OR PREDOMINANTLY HYDRO SYSTEMS WITH HIGH REACTIVE ABSORPTION CAPABILITY OR FOR LARGE SYSTEMS WITH VERY COMPACT SERVICE TERRITORIES USUALLY SELECTED WHEN STRONG NEIGHBOURING INTERCONNECTION ASSISTANCE 1S AVAILABLE INTERCONNECTION STATUS IS TO BE ASSESSED, HENCE TIME CONSUMING AND TASKING. BUILD DOWN OR SEQUENTIAL STRATEGY

 SIMULTANEOUS RESTORATION OF ISLANDS/ SUBSYSTEMS FOLLOWED BY THEIR MUTUAL SYNCHRONIZATION  USUALLY SELECTED IN CASE OF A COMPLETE SYSTEM COLLAPSE AND LACK OF INTERCONNECTION ASSISTANCE  RELATIVELY QUICK PROCESS  REQUIRES SEVERAL OPERATING TEAMS AND ADEQUATE COMMUNICATION FACILITIES FOR MUTUAL COORDINATION BUILD UP STRATEGY

BUILD UP EXAMPLE- AP SYSTEM RESTORATION VTS+GAS NSR+SSLM RyTPP+ CUDDAPAH RADIAL ON TN

SPECIAL CONSIDERATIONS FIRM TRANSMISSION IN THE INTERCONNECTION BETWEEN SUBSYSTEMS AND FIRM GENERATION CAPACITY IN EACH SUB SYSTEM TO BE ENSURED DURING EARLY STAGES OF RESTORATION DEACTIVATION OF AUTOMATIC LOAD SHEDDING AND AUTOMATIC SWITCHED CAPACITORS DURING INITIAL STAGES, RESTORATION OF SMALLER RADIAL LOADS FOLLOWED BY LOW VOLTAGE AC NETWORK LOADS WHILE MAINTAINING REASONABLY CONSTANT REAL TO REACTIVE POWER RATIO PICKING UP SMALL BLOCKS OF LOADS FOLLOWED BY AS LARGE AS POSSIBLE, WITHOUT RISKING DANGEROUS DECLINE OF FREQUENCY, AS RESTORATION PROCEEDS. KEEPING GENERATOR TERMINAL VOLTAGES RELATIVELY LOW INITIALLY, AND ADJUSTING TRANSFORMER TAPS, SUBSEQUENTLY AS RESTORATION PROCEEDS

RESTORATION PLANNING GENERAL GUIDELINES FORMATION OF A PLANNING TEAM PARTICIPATION OF EXPERIENCED/KNOWLEDGEABLE PERSONNEL FROM RESPECTIVE FIELDS LIKE PROTECTION, COMMUNICATION, OPERATIONS, SYSTEM ANALYSIS ETC. REVIEW OF SYSTEM CHARACTERISTICS (RELEVANT TO RESTORATION)

RESTORATION PLANNING COMMON CONCERNS TIME CONSUMING NATURE OF SWITCHING OPERATION START-UP TIMINGS OF THERMAL UNITS FREQUENCY RESPONSE OF PRIME MOVERS TO SUDDEN LOAD PICK UP COLD LOAD INRUSH, POWER FACTORS AND COINCIDENT DEMAND FACTORS AVAILABILITY OF GOVERNOR FACILITIES OF UNITS

FORMULATION OF ASSUMPTIONS WORST POSSIBLE SCENARIO TO BE CONSIDERED USING SYSTEM OPERATORS EXPERIENCE AND JUDGEMENT CONSTRAINTS MAY DIFFER WIDELY FOR PEAK AND LEAN CONDITIONS COORDINATION OF LOAD PICKUP WITH GENERATOR RESPONSE AND ARRESTING FALL OF FRFQUFNCY, BEYOND PRIME MOVER RECOVERY CAPABILITY UNDER PEAK CONDITION BLACK-START FACILITIES MAY NOT BE AVAILABLE DURING WEEK END LEAN PERIOD

ESTABLISHMENT OF GOALS LOCAL CONDITIONS LIKE GENERATIOR MIX TYPE OF LOAD AND CONTRACTUAL OBLIGATIONS PLAY A DECISIVE ROLE IMMEDIATE OBJECTIVE (SYSTEM SPECIFIC) COULD BE. RE-ENERGIZING THE BULK POWER NETWORK OR ATTAINING A CERTAIN LEVEL OF ACTIVE AND REACTIVE CAPABILITY OR PICKING UP A DOWNTOWN LOAD OR SUPPLYING TIME-CRITICAL INDUSTRIAL LOADS OR ENERGIZING EHV LINE TO A REMOTE, LARGE GENERATING STATION

VALIDATION OF ASSUMPTIONS PROPER MODELLING OF STEADY STATE AND DYNAMIC BEHAVIOUR OF POWER SYSTEM CONFIRMING THE FEASIBILITY AND SECURITY OF PROPOSED ACTIONS USING A VARIETY OF ANALYSIS AND SIIMULATION TOOLS LIKE STEADY- STATE POWER FLOW, TRANSIENT AND DYNAMIC STABILITY ANALYSIS AND ELECTROMAGNETIC TRANSIENT SIMULATIONS LOAD DATA, GENERATION DATA ETC. TO BE PREPARED CAREFULLY ITERATION TWO ITERATIONS ARE INVOLVED - 1.MODELS HAVE TO BE VALIDATED AGAINST MEASURED AND TELEMETERED DATA 2.THE RESTORATION PLAN (TACTICS) DEVELOPED TO BE CHECKED AGAINST THE INITIAL STRATEGY FOR CONFORMITY AND FEASIBILITY

LOGISTICS AND COMMUNICATION CLOSE AND CONTINUAL CO-ORDINATION AMONG POWER SYSTEM POWER PLANT AND FIELD OPERATORS NEIGHBOURING UTILITIES, AUTHORITIES TO BE INFORMED TIME TO TIME ABOUT THE PROGRESS OF RESTORATION. TO DEPEND MORE ON THE UTILITIES’ OWN COMMUNICATION FACILITIES FALL BACK ARRANGEMENT IN CASE OF COMMUNICATION FAILURE.

EXPERT / COMMANDO GROUP COMMANDO GROUP TO BE FORMED AS THE SYSTEM COMPLEXITY GROWS. GROUP SHOULD CONSIST OF ENGINEERS FROM DIFFERENT FIELDS AND BELONGING TO DIFFERENT UTIILITIES. PERFECT UNDERSTANDING IN THIS CORE GROUP IT ENCHANCES THE MORAL STRENGTH OF FIELD OFFICERS AS WELL AS REDUCES RESTORATION TIME

AUIDITS AND UPDATES A TECHNICAL PERSON OUTSIDE THE RESTORATION TEAM SHOULD AUDIT THE ACTIVITIES. AUDITED RESTORATION PLAN MUST BE UPDATED. DOCUMENTS MUST BE REVISED REGULARLY TO REFLECT THE LATEST CHARACTERISTICS OF THE SYSTEM. CHANGES IN THE SCADA/EMS INSTALLATION OR MAJOR PLANT CONTROL, AVAILABLE TOOLS ALSO TO BE INCORPORATED.

TRAINING INSTRUCTION MANUALS OR AUDIO –VISUAL TAPES, FOR INDEPENDENT STUDY CLASSROOM INSTRUCTIONS LEARNING FROM PAST EXPERIENCE DURING RESTORATION. OPERATOR TRAINING SIMULATOR. ROLE PLAY OPERATOR’ S PROBLEM SOLVING CAPABILITY CAN ALSO BE EXPLORED AND DEVELOPED. ALTERNATIVE, SOURCE OF FINDING NEW IDEAS. DETAILED INTERACTION WITH THE PERSONS INVOLVED IN RESTORATION

DOCUMENTATION PURPOSE: TRAINING- REFERENCE, IMPROVEMENT OF RESTORATION PROCEDURES. SHOULD BE READILY ACCESSIBLE AND EASILY UNDERSTOOD. SHOULD BE STORED IN A CONVENIENT MEDIA FOR QUICK PROCESSING. SHOULD BE ILLUSTRATED WITH FAMILIAR DIAGRAMS AND CHARTS ACTIONS REJECTED AND INCORPORATED IN THE PLAN MUST BE RECORDED