Grid Event Analysis In Indian Power System

Grid Event Analysis
Chandan Kumar
Senior Engineer
Western Regional Load Despatch Centre, Mumbai
POSOCO

Grid Events and
Reporting Protocol
215-02-17 WRLDC,POSOCO

What is a Grid Event ?
IEGC Clause 5.9.5 Reportable Events
• Any of the following events require reporting by RLDC/ Users, SLDC, STU, CTU:
• Violation of security standards
• Grid indiscipline.
• Non-compliance of RLDC’s instructions.
• System Islanding/System Split
• Regional Black Out/Partial System Black Out
• Protection failure on any element of ISTS, and on any item on the “agreed list “of the intra-
State systems.
• Power System Instability
• Tripping of any element of the Regional grid.
• Sudden load rejection by any User
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*Apart from these the System Protection Scheme Operation is also an Event

Category of Grid Event
CEA Grid Standard 2010
• Grid Incident (Less Severe) and Grid Disturbance (More Severe)
• “Grid Disturbance” means tripping of one or more power system elements of the grid like a
generator, transmission line, transformer, shunt reactor, series capacitor and Static VAR Compensator,
resulting in total failure of supply at a sub-station or loss of integrity of the grid, at the level of
transmission system at 220 kV and above (132 kV and above in the case of North-Eastern Region).
• “Grid Incident” means tripping of one or more power system elements of the grid like a generator,
transmission line, transformer, shunt reactor, series capacitor and Static VAR Compensator, which
requires re-scheduling of generation or load, without total loss of supply at a sub-station or loss of
integrity of the grid at 220 kV and above (132 kV and above in the case of North-Eastern Region).
Note :
• Loss of Integrity: It can be used for system instability, several tripping, cascade tripping, system insecurity, system separation
etc.
• Total loss of Supply to Sub-station: Tripping of all the elements at the sub-station at all voltage level in a sub-station

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• Category GI-1- Tripping of one or more power system elements of the grid like a generator,
integrity of the grid at 220 kV (132 kV in the case of North-Eastern Region)
• Category GI-2- Tripping of one or more power system elements of the grid like a generator,
integrity of the grid at 400 kV and above (220 kV and above in the case of North-Eastern Region).
Category of Grid Incident

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Category GD-1- When less than ten percent of the antecedent generation or load in a regional grid is lost;
Category GD-2- When ten per cent to less than twenty percent of the antecedent generation or load in a
regional grid is lost.
Category GD-3- When twenty percent to less than thirty percent of the antecedent generation or load in a
regional grid is lost;
Category GD-4- When thirty percent to less than forty percent of the antecedent generation or load in a
regional grid is lost;
Category GD-5- When forty percent or more of the antecedent generation or load in a regional grid is lost.
Explanation: For the purpose of categorization of grid disturbances, percentage loss of generation or load,
whichever is higher shall be considered.
Category of Grid Disturbance

Why it is required to inform WRLDC
• WRLDC has to Operate and Coordinate with all SLDCs/NLDC in secure and reliable Grid Operation
• WRLDC has to overview the impact of any event on Western Grid.
• WRLDC has to inform NLDC who will look for impact on National Grid.
• WRLDC to coordinate with several affected entities for Faster Restoration.
• WRLDC has to categorize the event as per CEA Grid Standard.
• WRLDC has to take corrective action and maintain grid stability for next contingencies.
• WRLDC has to prepare report based on Event analysis for preventive/corrective action.
• WRLDC has to perform root cause analysis on the event.
• WRLDC has to perform Statistical analysis of event for long term suggestion to utility.
• WRLDC/NLDC has to provide operational feedback to CEA and CTU.
• WRLDC has to provide such issues for discussion at Appropriate forum like OCC/PCM/TCC
meeting.
• WRLDC inform utility in case of any Non-compliance of standard to correct the same.
• Mandatory as per Regulations.

Role of Various Organizations
Reporting of Event to RLDC
• Various regulations have defined the role of User/Entities/Users for reporting of
any grid event to SLDC/RLDC/NLDC .
• IEGC Clause 5.2.d defines the reporting for System Security Aspects:
• IEGC Clause 5.6.2 defines on reporting of event in the state system
• IEGC Clause 5.9.4.b defines the event Information Responsibility for All Users, STU, CTU and
the SLDC
• CEA Grid Standard 12 defines the Responsibility of information sharing by User to appropriate
LDC in the prescribed format

Reporting Format
• Flash Report : Preliminary information on event like Location of Fault, Elements Tripped, Sub-station Blackout,
Amount of approximate Load/Generation Loss. (In Flash Report Format) : In Real Time during/after Restoration
• Other Information: FIR from Sub-station/Circle, DR/EL logger, Single Line diagram indicating fault, Probable
reason of event, Relay/flag indication. (Within 24 Hours)
• IEGC 5.9.6.c : Written Report by NLDC, RLDC, ,a User, STU,CTU ,SLDC, as the case may with following
Information
1. Time and date of event
2. Location
3. Plant and/or Equipment directly involved
4. Antecedent conditions of load and generation, including frequency, voltage and the flows in the affected area at the
time of tripping including Weather Condition prior to the event
5. Duration of interruption and Demand and/or Generation (in MW and MWh) interrupted
6. All Relevant system data including copies of records of all recording instruments including Disturbance Recorder, Event
Logger, DAS etc.
7. Sequence of tripping with time.
8. Details of Relay Flags.
9. Remedial measures

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Format of Flash Report
It’s a flash report : One Operator sharing information with other.

Protection as per
Regulation

Protection In Power System
• Protection is an important aspect of power system as it isolate the faulty part of the system so as to save the
rest of the system.
• Any power system protection must have following aspect :
• Accuracy : Refers to accuracy in measurement of quantity as observed by the protection system
• Dependability : Degree of Certainty with which it will operate correctly.
• Reliability : Operate during situation for which it is designed.
• Security : Degree of certainty with which relay will not operate incorrectly irrespective of nature
of operating state of power system
• Selectivity : It is the ability to correctly locate and classify the fault.
• Sensitivity : It is the ability of the relay to pick up even on smallest possible faults.
• CEA Technical Standard for Construction of Electrical Plants and Electric Lines defines the various protection
to be provided at any sub-station for various power system elements. Other standard also defines few
aspects to some capacity.
• There are two guidelines available : Ramakrishna Committee and CBIP.

Protection adopted in Indian Grid as per CEA Technical Standard
for Construction of Electrical Plants and Electric Lines
• It states that “Adequately Sectionalized and graded protective relaying system shall be provided for
transmission lines, transformers and bus bars so as to automatically isolate the faulty equipment and, thus,
minimize the damage to the equipment in the event of faults and abnormal conditions. All main protection
relays shall be of numerical type and communication protocol shall be as per IEC-61850/Relevant is.”
Element Type of Protection
Transmission
Line
Carrier aided distance protection, Directional IDMT earth fault protection, Two stage over
voltage protection, Auto reclosing.
Transformer Differential protection, Restricted Earth Fault (REF) protection, Over flux, Backup Differential O/C
and Earth Fault protection, Impedance protection, Overload alarm, Buchholz , Winding
Temperature indictor(WTI), Oil temperature indictor(OTI), Pressure release device(PRD),Oil surge
relay (OSR) ,Magnetic oil gauge(MOG), Surge Arrestor (SA)
Reactor Impedance type or Definite time over current protection , Earth fault protection, Buchholz ,
Winding Temperature indictor(WTI), Oil temperature indictor(OTI), Magnetic oil gauge(MOG),
Surge Arrestor (SA)
Bus Bar Bus bar differential protection, Local breaker back up protection
Generator Class A ,B and C Protection

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Fault Clearance Time : As per CEA Grid Standard 2010 , Protection System should
isolate any fault at 400 kV and above level within 100 ms and 220 kV and 132 kV
faults at 160 ms.
Here “fault clearance time” means the maximum fault clearance times as
described above provided that in the event of non-clearance of the fault by a
circuit breaker within the time limit specified above, the breaker fail protection
shall initiate tripping of all other breakers in the concerned bus-section to clear
the fault in the next 200 milliseconds.

Protection Aspect for Transmission Lines
CEA Technical Standard for Construction of Electrical Plants and Electric Lines
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• Crosscheck and revise setting with new elements
• Revise setting based on the experience during
event after discussion at STU/CTU/PCM
• Always do the Zone 3 setting coordination with
help of STU/CTU.
• Inform about any setting revision and its reason to
remote end sub-station.
• Auto-Reclosing : Mandatory
• 220 kV lines Auto-Reclosure is also required.
• Over voltage grading : Time & Voltage.
• Check for CVT errors on regular basis to avoid mis-
operation of O/V.
• Directional Earth fault should be set properly
specially for lines passing through forest area.

Protection Aspect for Transformer
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• Crosscheck and revise setting with new elements
• Always do the Zone 2/3 setting coordination with
help of STU/CTU for Lines and ICTs.
• Always monitor Buchholz relay/WTI/OTI operation
: Several Mal-operation has been reported which
led to grid under Alert State.
• Monitor the load trimming scheme where ICTs are
not complying N-1 : Several Mal-operation has
been reported leading grid to Alert state with
large load loss event.

Protection Aspect for Reactor
Protection Aspect for Bus Bar protection
CEA Regulation: Measures relating to Safety and Electric Supply 2010
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• REF mal-operation
has been reported
several time.
• Large event at Sipat
in 2012.
• Its Mandatory and it
has to be there from
132 kV onwards.
• Several mal-
operation has been
reported in past.
• Do cross check it with
new elements.
• Check its
performance at
scheduled interval.

Auto-Reclosure Facility
• This helps in improving line availability during transient fault.
• What do we have in regulation on Auto-Reclosure
• CEA Technical Standard for Construction of Electrical Plants and Electric Lines 43.4.C
• Single Phase and Three phase Auto-Reclsoure : 765 kV, 400 kV and 220 kV Lines
• Three phase Auto-Reclosure : 132 and 66 kV Lines
• CEA Transmission Planning Criteria : ISTS network has been planned for “The system shall be able to survive a
temporary single phase to ground fault on a 765 kV line or 400 kV line close to the bus. Accordingly, single pole
opening (100 ms) of the faulted phase and successful re-closure (dead time 1 second) shall be considered”
• In Several cases, this violation has been reported by WRLDC to utility for corrective action based on
observation from Synchrophasor measurements.
• There after several cases of successful Auto-Reclosure in Western region has improved the system reliability.
• Example : JP Nigrie, JPL, Essar Hazira, Korba, 220 kV Inter-regional Lines.
• Many time A/R is bypassed for OPGW/RTAMC/PID and other Work and Brought back after a large delay.
• It impacts security as in case of transient single phase fault element is lost
• Case of 765 kV lines tripping in WR-2, All lines from Parli S/s.

Time Synchronization
• Indian Electricity Grid Code 4.6.3 : Refer to ISTS lines where Data Acquisition System/Disturbance
Recorder/Event Logging Facilities/Fault Locator should be GPS time synchronized.
• CEA Technical Standard for Construction of Electrical Plants and Electric Lines 43.4.D.: Each 765 kV,
400 kV and 220 kV Line shall be provided with facility for disturbance recording, distance to fault
locator and time synchronization equipment (TSE). Event logger either stand alone or as a part of sub-
station or switchyard automation system shall be provided for each 220 kV and higher voltage class
sub-station or Switchyard.
• CEA Regulation: Measures relating to Safety and Electric Supply 2010 45.2. VIII : Refer to all 220 kV
and above elements.
• Timesynchronised Information helps in sequencing of event and recreation of any event for root
cause analysis.
• Example : Incident of Blackout at CGPL and AKola2 & Akola where few non-time synchronized DR
resulted in lot of difficulty in creating sequence of event.
• Violation Observed : Many cases where in Audit report, it is mentioned all DR/EL time synchronized
however during event analysis same is not observed.

Other Aspects
• Delay in Restoration Due to Non-Availability of Spare Parts
• CEA Grid Standard 2010 -28.1: Inventory control and spare part management. The required spare parts shall be kept in
stock, to ensure speedy the maintenance of the equipment.
• Example
• Non-Availability of CVT at Solapur Resulted in Separation of NEW Grid and SR Grid.
• Non Availability of Spare SPS Module at Gwalior for NR-WR SPS scheme.
• Availability of SCADA and SOE
• Indian Electricity Grid Code 4.6.2
• Indian Electricity Grid Code 5.2.q
• CEA (Technical standards for connectivity to the Grid) Regulation (2007) General connectivity conditions 6.3
• CEA (Technical standards for connectivity to the Grid) Regulation (2007) General connectivity conditions 6.5
• CEA grid standard 15.1
• Example :
• Many a time Event occurred but non-observable in the system. State Estimation also not converge causing non
detection.
• Event on 19 May 2015 for Multiple Tripping in Madhya Pradesh and No SCADA data. Large Event avoided due to
real time security desk at WRLDC.

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System Protection Scheme
IEGC 5.2.O : On SPS Scheme
• All Users, STU/SLDC,CTU/RLDC and NLDC, shall facilitate identification, installation and commissioning of System Protection
Schemes (SPS) (including inter-tripping and run-back) in the power system :
• to operate the transmission system closer to their limits
• to protect against situations such as voltage collapse and cascade tripping, tripping of important corridors/flow-gates
etc.
• Such schemes would be finalized by the concerned RPC forum, and shall always be kept in service.
• If any SPS is to be taken out of service, permission of RLDC shall be obtained indicating reason and duration of anticipated
outage from service.
Western Region SPS :
• Generators : CGPL, Sasan, Sipat, APL, APML, JPL, Balco, Essar Mahan
• Load Entity : Essar Hazira
• Corridor : WR-NR Corridor, WR-SR corridor are all having SPS schemes.
• HVDC : APL Mundra-Mohindergarh Bipole
• Regular SPS testing is compulsory so that its healthiness to be ensured.
• Non-operation or Wrong operation may causes widespread event : CGPL Blackout. Excess load tripping for APL Mundra
Bipole.15-02-17 WRLDC,POSOCO

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Role of CTU/STU/RPC
CEA Grid Standard 3.e :
• Provide standard protection systems : Reliability, selectivity, speed and sensitivity
• Isolate fault within the specified fault clearance time
• Provide protection coordination as specified by the Regional Power Committee.
CEA Connectivity Regulation 6.6 :
• For interconnection studies User shall submit required data to STU/CTU.
• STU/CTU to perform interconnection study and provide modification required in existing grid.
• Study may also involve Protective relaying.(Several number of studies involved depending on
requirement)
CEA Connectivity Regulation Part I ,6.6 : Protection coordination issues shall be finalized by Regional
Power Committee.

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New Element Charging : Be Cautious
• Grid in development stage
• Commissioning of new element is important.
• At the same Time, Grid should be ready to adapt the new element.
• Protection is the most important aspect while first charging as well as after commissioning.
• So, Preparatory step should start with intimating other nearby station and their agency regarding
which element is being charged.
• CTU/STU must study the impact of the new element and accordingly issue the revision in
protection scheme ( mandatory as apart of CEA connectivity Regulation).
• RLDC/SLDC must confirm whether the protection at nearby stations has been revised or not.
• Specially ask the Generator Entity as they in general don’t have a study group.
Example of large event when such activities are neglected: Akola2,Akola and RIPL Blackout on 29
March 2015.
• One New 400 kV line was charged. Its protection has failed and utility violated several protocol.
• SLDC has to check the duration up to which it was allowed along with all necessary compliance.
• No intimation to nearby station for revision of protection scheme.

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Analysis & Outcome

Why operator do Analysis ?
• Its not only about reporting of compliance , Its about Power System Security.
• Operator Analyse the event to look for Operational and Protection issue for faster remedial action.
• Operator has DR/EL, Grid Details from SCADA, Synchrophasor Data from PMU, SOE data.
• All must be analyzed to interlink the complete event to form a better chronology.
• Few Stats on large Event Analysis at WRLDC
Type of Data
Akola Incident on
29 March 2015
CGPL on 12
March 2015
Disturbance Recorder 77 50
Event logger 4 5
SOE 1 1
PMU Data 16 Nodes All India
Reports from Entity 4 2
• Event on 19 May 2015 : 19 tripping of 765 and 400 kV lines (Total 34 Tripping)
• Near Miss event for Sasan and Vindhyachal Complex ( 765 kV Lines was charged in 17 Minute span to based
on PMU data analysis )
• Based on Site information and PMU data , Faster Restoration
Several Corrective
Actions and Lesson learnt

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Year
2012-
2013
2013-
2014
2014-
2015
Number of Grid Events (GD+GI) 80 106 157
Number of Grid Disturbance (GD) 36 47 60
Number of Grid Incidence(GI) 44 59 97
Number of GD with Generation Loss 24 38 21
Number of GD with load Loss 14 18 39
Maximum Gen Loss (MW) in any GD 2388 4030 1845
Maximum Load Loss (MW) in any GD 800 1295 1500
Statistic : Summary of Events from 2012-2015

10-Feb-2017 WRLDC, POSOCO 27
Some Statistic : Be Vigilant About Reality

10-Feb-2017 WRLDC, POSOCO 28
Primary Reason for Grid Event in Western Region

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Protection and Its Impact
Major Mis-operation or Poor Protection Coordination and Its Impact
• Event in Southern Maharashtra on 28th Feb-1st March 2015
• Complete Southern Maharashtra along with Goa Blackout
• Issue of Overvoltage grading
• 23 Lines tripped on O/V and 7 lines opened on high voltage.
• 5 400 kV Sub-Stations dead.
• Event at Akola2 on 29th March 2015
• One Protection non-operation and lack of protection coordination in nearby station
• Tripping of 18 elements (400 and 765 kV level)
• Event at Solapur on 25th May and 31st May 2015
• Issue of Auto-synchronization facility.
• Severe power swing in the grid due to manual synchronization.
• Seismic wave felt in all India Grid
• Complete analysis based on PMU data. (DR/EL missing)

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Non Availability of Adequate Protection System and Its Impact
• Event in Pune Ring Main on 7 May’14
• Multiple line tripping on overcurrent causing blackout in Pune Ring main area.
• 7 220 kV lines on Backup O/C and 3 220 kV Lines on Load trimming scheme.
• Lack of N-1 protection compliance.
• Event at Korba West on 19 Sept’14
• No bus bar protection at 400 kV Bus
• Bus fault resulting in complete blackout
• Severe damage to Generating Unit.
• Event at Aurangabad-Bableshwar on 29 Sept’14
• 200 kV Bus 1 fault at Aurangabad causing cascaded tripping at Bableshwar.
• Widespread outage in the area.
• Event at Birsinghpur on 13 Nov’14
• Bus Fault at 220 kV Bus, No Bus Bar protection
• Protection coordination issue of 400/220 kV ICT
• All 400 kV Lines tripped and complete sub-station blackout

Few Fault Analysis
Based on DR and PMU

Single Phase Fault
• Most common type of fault in power system :
• Four cases of Single phase to ground fault :
• Single phase to earth fault on transmission line with successful A/R
• Single phase to earth fault on transmission line with unsuccessful A/R
• Single phase to earth fault on transmission line with no A/R.
• Single phase to earth fault on Bus bar.
Fig : Voltage of 400 kV Jabalpur bus from Synchrophasor data during single
phase to ground fault on 400 kV Vindhyachal-Jabalpur circuit 4.
Fig : Current through 400kV Vindhyachal-Jabalpur circuit 4 observed from Jabalpur
end

Fig : Voltage of 400 kV Solapur bus and Current through 400 kV Solapur-Parli circuit 1 from
PMU at Solapur.
Fig : Voltage of 400 kV Korba bus and Current through 400 kV Korba-Bhatapara circuit from
PMU at Korba.
Single phase to earth fault on transmission line with
unsuccessful A/R
Single phase to earth fault on transmission line with
no A/R.

Fig : Voltage of 400 kV Boisar bus during single phase to ground fault on 220 kv Padghe Bus II from
Synchrophasor data
How it helps a Grid Operator
Grid operator knows the type of Fault.
Helps in taking decision whether to allow trial
charging or not.
Validates whether A/R has occurred or not.
Analysis of event in real time.
More you know , better equipped you are.
“The difference between being a victim and a survivor is often a low level of situational awareness” Barry Eisler
Single phase to earth fault on Bus bar

Phase to Phase Fault
• Second most common type of fault in power system .
• Such faults are usually due to opening of jumper in transmission line or the kite strings
• Charging allowed without patrolling is dangerous in case of fault near to generators.
• Dip and rise that’s what we need to monitor……..
• Many cases when charging could have resulted in fault feeding were avoided.
Fig : Voltage of 400 kV Dehgam bus during Phase to Phase fault on 400 kV Dehgam-
Gandhar circuit 2 from Synchrophasor data
Fig : Current of 400 kV Dehgam- Gandhar citcuit 2 observed from Dehgam end from
Synchrophasor data

Three Phase Fault
• Such faults are Time bombs for Electrical Grid
• May result in commutation failure of nearby HVDC
• Stalling or tripping of induction motor based loads in the nearby area.
Fig : Voltage of 400 kV Boisar bus during three phase fault on 220 kV Padghe bus 1 from
Synchrophasor data
Fig : Current of 400 kV Boisar-Padghe circuit during the three phase bus fault on 220 kV
Padghe Bus 1 from Synchrophasor data

Conclusion
Must Do :
• Always comply with Regulations on Protection.
• Always report Event with all the details.
• Always perform Root Cause Analysis for All tripping.
• Always share the lessons learnt with SLDC/RLDC/NLDC so in turn everyone can be benefitted from your
experience.
• DR in Comtrade and EL in .pdf/.xls is to WRLDC/WRPC.
• Prior to any new element charging in the system , Nearby station should study and revise their protection.
Appreciate :
• Each element has to be protected.
• Each tripping has to be analyzed.
• Protection is always a collective effort.
• Each Organization has to give its effort in making a better protected system.
• For Faster restoration, preliminary analysis data need to be send to WRLDC.
• Looking forward to your Coordination.
• Email Id : protectionwrldc@posoco.in

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Bibliography
Regulation by CERC
• Indian Electricity Grid Code
• Standards of Performance of inter-State transmission licensees Regulations, 2012
• Grant of Connectivity, Long-term Access and Medium-term Open Access in inter-State
Transmission and related matters
Regulation/Standard by CEA
• CEA Grid Standard 2010
• CEA (Technical standards for connectivity to the Grid) Regulation, 2007
• CEA Technical Standard for Construction of Electrical Plants and Electric Lines
• CEA Regulation: Measures relating to Safety and Electric Supply 2010
State Regulation
• Madhya Pradesh State Electricity Grid Code
• Gujarat Pradesh State Electricity Grid Code
• Maharashtra State Electricity Grid Code
• Chhattisgarh State Electricity Grid Code
• JERC Grid Code
Other
• Ramarkrishna Committee Task Force Report on PSA under contingencies
• CBIP Manual on Protection of 400 and 220 kV Transmission lines
• Enquiry Committee Report on Grid Disturbance on 30th and 31st July 2012

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Few Events in MPPGCL

GD-1 at Tons Rewa Siddhi 23-05-16
• Non-Operation of Bus bar Protection at Tons due to Permanent
Damage in switchyard.
• Bus Bar protection was kept out as the Maintenance work was going on the
Bus 1.
• No Operation of Bus bar caused large blackout in the area and fault feeding
exceeding the specified time of CEA grid Standard.
• Why the Bus bar was out when maintenance activity of one bus is being
carried out.

GI-2 at Astha and Satpura Extension on 6th Oct’16
• 220 kV Bus Fault at Astha S/s where Bus Bar Protection was kept out.
• Fault being fed from 400 kV System through 400 kV Satpura-Astha
D/c.
• Prior to Zone/Zone 3 Protection operation, the earth Fault protection of
Generator Transformer has operated causing tripping of Both the Units.
• Several cases like Shingaji, Amarkantak, Birsinghpur, Satpura has been
observed in the past on the similar issue.
• This need a deliberation at large scale and setting coordination with MPPTCL.
• This is an example how various deficiencies merge up and cause large
tripping.

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Observation Based on the Analysis
of Protection Audit Reports

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Observations:
The protective relay settings shall be coordinated by a central agency,
irrespective of individual utility practice.
The minimum events’ list needs to be standardized by RPCs
All signals in event logger or SCADA system must be clear identified and
should contain at least: time, location, identification/description, type (event,
warming, and alarm), and status (active /inactive).
Pending of budget approval
No reaction even the recommendation was very urgent (DC system earthed)
Implementation Status of Recommendations of Last Protection Audit

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Deficiencies:
Different calculus for different entities
Different settings for line ends
Min or max short circuit current not updated for protection calculus
Setting values not available in substation
Setting values submitted to consultant not matched withactual relays settings
Different rules/norms for general protection function settings (breaker failure, auto
recloser, pole discrepancy)
Different settings between main 1 and main 2 relay
Review of Existing Settings in Substations

45
Recommendations:
Central (national) protection dispatch in charge of protection coordination for all
entities
Protection coordination department for each entities
Last information regarding generation and transmissionsystem and equipment,
functionality scheme etc. available for each entity protection department
Software for protection relay coordination and system study
Protection coordination for new elements has to be performed by central
protection dispatch. This agency will approve new settings or protection system
changes.
Procedure for calculation, approval, implementation and change of protection
settings
Last protection settings available in substation
Norms and regulations for protection system should be available in whole country
and to be accepted and followed by all entities.

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Observations:
Disturbance Recorder (DR) and Event Logger (EL) available in most of substations
DR and EL not time sync for some substation
Analysis report for event not available in most of substation
In most of substation analysis report not include root cause of event and corrective
actions taken
Recommendations:
Compulsoriness of analysis report preparation for each entities
Report contain:
• Event analysis
• Root cause
• Protection system operation (correct, incorrect, unwanted)and time sync
• Corrective action
Event Analyses and Remedial Action

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Observation:
No formal approval for protection change and archival
Communication of changes use simple E-mail
Not method of recording of implemented settings and archiving
Recommendations:
Methodology for approving, implementation and reporting of protection settings
changes
All protection changes in one substation have to be submitted to central
protection dispatch for approval/knowledge and to utilities/entities connected to
that substation
Existing Process for Record of Changes Incorporated
in Relay Settings

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Numerical relay include only main protection function. Rest of protection functions in old relays
Recommendation:
• Numerical relays with included protection functions. Advantages: flexibility of parametrization,
watch dog, wiring.
• Trip circuit supervision, DC supervision, Lock out relays
• Breaker failure protection with different settings (in same SS) and without stage I
• Line differential protection relay for short lines (<30km) with distance protection function included
• Deviations from “Relay settings guide line”
• STUB protection trip time 50ms (actual 100ms)
• Distance protection, reverse zone (zone 4), to be set for50% of shortest line (do not
encroach upper/lower voltage level or zone 2 of shortest line)
• VT fail supervision to be activated in all distance and DEF protections
• Power swing and out of step protection available for all lines
• Overvoltage level grading and time grading implemented in all cases
Other Deficiencies or Observations

49
• Voltage selection scheme for distance protection when bus bar VT are used
• Pole discrepancy time delay to be uniformly set
• Time sync for all numerical relays
• Single Bus Bar Protection (BBP) fed with single DC power
• Single DC power supply for protection panels
• Synchro check trolley not working
• AC power supply from one source; Automatic bus transfer or remotely control of
AC sources
• Protection of battery against short circuits and explosions (circuit breaker,
ventilation)
• Unhealthy DC system (earth fault)
• Unsealed junction boxes

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• Cable trench and trench covers destroyed
• OPGW for new lines
• CT&VT star connection inside junction boxes, VT protectionMCB inside junction box
• Circuit breaker pressure monitor dirty and without limits
• Fire fighting not in service and not connected to trip circuit
• Transformer WTI&OTI and fans broken
• 400kV CVT with big errors (13%) (periodic tests?!?)
• CT, VT, CB not tested (10-15 years)
• Detailed drawings not available in substation

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Differential/Distance protection relay with
protection functions included (Main 1 and
Main 2)
• Same relay configuration
• Redundant communication with remote
end (FO, PLC)
• Dedicated CT coil and VT winding for main
1 and main 2
• Separate DC supply for main 1 and main 2
• Different trip coil for main 1 and main 2
• Back up directional overcurrent protection
Main 1 and Main 2 = Differential
protection relay + technological
protection (Buchholtz, overpressure,
over temperature)
• Dedicated CT coil for each protection
relay
• Separate DC supply for main 1 and
main 2
• Trip signal to both coils of CBs of all
transformer sides
• Back up distance protection relay for
both voltage levels
• Back up non directional overcurrent
protection
Transformer ProtectionLine Protection

52
Thank you !

Grid Event Analysis In Indian Power System

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