blackout
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TRANSCRIPT
30-31st July, 2012 Power Blackout in India
A review
Compiled from the CERC investigation report
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Contents1. Overview2. Indian Grid System
– Types of Transmission lines– Layout of the Indian Grid– What is grid disturbance?
3. Blackout 30th July 2012– Reasons for Blackout -30th July 2012– Restoration
4. Blackout 31st July 2012– Reasons for Blackout -31st July 2012– Restoration
5. Technical Recommendations (1,2,3 and 4)6. Policy Recommendations (1 & 2)7. Proposed changes8. Need for Smart Grids - Future
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July 30-31,2012 -Biggest Power Blackout in Indian History
1. Overview
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CERC conducted an investigation on the causes
• Full report on grid disturbance (CERC Order in Petition No. 167/Suo-Motu/2012 dated 1st Aug2012).
• CERC released the report titled “Status of action taken on recommendation of the enquiry committee on grid disturbance in northern region on 30th July 2012 and in Northern, Eastern & North-Eastern Region on 31st JULY 2012”
CERC report
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2. India National Grid – Hierarchy
Indian Grid - NLDC
New Grid
Northern Region -RLDC
SLDC
Western Region - RLDC
SLDC
Eastern Region - RLDC
SLDC
North-Eastern Region - RLDC
SLDC
Southern Region - RLDC
SLDC
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Types of Transmission line
220kV
• Mostly within the state
400KV
• Long distance (State-State, Region – Region)
765KV
• Long distance state – Region- Region transmission
500 KV -
HVDC
• Latest technology for long distance power transmission with minimum losses.
• These are much popular in the off-shore wind farm transmission lines in the UK
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Layout – The NEW GRID
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What is grid disturbance? A grid is said to
be disturbed when :
a) there is an under voltage
(U/V)
b) there is over voltage (O/V)
c) there is under frequency (U/F)
d) there is over frequency (O/F)
e) there is a rapid fall or rise in frequency (
+dF/dT or -dF/dT )
f) there is a power failure in the grid
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Blackout - Affected Regions (30 & 31st July)
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29th July – evening before blackout
28th July 2012
10:18pm
9:45pm 3:40pm
3:15pm
The 400 kV Bina- Gwalior-Agra-
2 was under planned shutdown since 28thJuly 2012
for up-gradation work to 765kV.
At 3:15pm, 29th July - 220 kV Kota-Badod Tripped due
to operation of distance protection three phase
Zone-1 indications at Badod end.
At 3:40pm, 220 kV Binmal (PG)- Sirohi - Phase to earth
fault. The two 220 kV outlets to Bhinmal(RVPNL) and one to Sanchore were in service from Bhinmal.
At 9:45pm, 400 kV Bhinmal- Kankroli Tripped due to insulator de-capping.
At 10:18pm, 400 kV Zerda- Kankroli Emergency outage for a period of two hours to take out one Tool & Plant (T
& P) which got stuck with one polymer insulator.
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3. 30th July – 1st blackout
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Frequency profile as captured by IIT Bombay
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Reason for blackout -30th July 2012 Summary
REASON – 30th Jul
400kV Bina-Gwalior-Agra 2 line was under planned
shutdown. This caused stress on other lines. Failure in load
management and planning
Large amount of unscheduled import of power by the Northern
region from western and eastern region.
Action was not taken to reduce the Total Transfer Capability (TTC) after shut
down of Zerda-Kankroli 400 KV line, . The TTC is shown
as 2000 MW before and after the shutdown of 400
KV line. Lack of observation and
coordination! Some gas and thermal plants where tripped in NR due to forced outage and shortage
of coal. Irregular Maintenance and
lack of monitoring
Sipat stage-1 plant was under trial operation and
caused unscheduled injection of power.
Once almost all the 400kV lines tripped overnight
(from WR to NR) and even many 200kV lines tripped, now the power from WR
started to flow to NR though ER. This caused
power swings in the ER and more lines started tripping
and caused a complete blackout.
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After Blackout – 30th July 2:33am
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Restoration – after blackout 30th July
• The Black out happened exactly at time – 2.33am . This affected 8 states and 1 U.T (Rajasthan, Haryana, New Delhi, J&K, Punjab, U.P, Himachal Pradesh, Uttarakhand and Chandigarh)
• Emergency loads like railway station, hospitals, airport were supplied with power by 8am
• By 10am 40% of the loads where restored.
• 100% load was restored by 4pm evening the same day.
Following slides shows how the restoration process was carried out!
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Self supported Islands – After blackout
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Restoration – from Eastern Region
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Restoration – from Western Region
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4. 31ST July Blackout • The Black out happened exactly at time – 1.00pm . This
affected 21 states and 1 Union Territory. This caused much bigger effect than the 30th July Blackout.
• The following states were affected by the grid failure:– States on the northern grid: Delhi, Haryana, Himachal Pradesh,
Jammu & Kashmir, Punjab, Rajasthan, Uttar Pradesh, Uttarakhand
– States on the eastern grid: Bihar, Jharkhand, Orissa, West Bengal– States on the northeast grid: Arunanchal Pradesh, Assam,
Manipur, Meghalaya, Mizoram, Nagaland, Sikkim
• The worst sufferers were 265 miners who got trapped in coal mines in West Bengal and Jharkhand due to the power outage. They were evacuated after hours of agony.
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31st July -2nd blackout
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Frequency shoot up at western region (WR)
In the Western Region due to loss of export to rest of the NEW grid, the frequency shot up to 51.46 Hz and many generating units and transmission lines tripped due to process related issues and high voltage respectively.
The frequency stabilized at around 51.0 Hz. The rise in frequency only illustrates the poor level of primary response.
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Reason for blackout 31st July 2012 SummaryLoss of 400 kV Bina-Gwalior link: Similar to the initiation of
the disturbance on 30th July, 2012, tripping of 400 kV Bina-
Gwalior line on zone-3 protection of distance relay, due to load
encroachment, caused the NR system to separate from the WR
system.
Weak Inter-regional Corridors
due to multiple outages
High Loading on 400 kV Bina-
Gwalior-Agra link-NR utilized Unscheduled
Interchange (UI) and this lead to overloading
Inadequate Response by
SLDCs to RLDCs’ instructions on this day also to reduce
overdrawl by the NR utilities and
underdrawal by the WR utilities
The UFR load shedding was not adequate to bring the frequency back to a safer level of
49.5 Hz and above.REASON – 31st Jul
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Restoration after blackout -31st July
• Total affected load because of Blackout was 48,000MW
• Emergency loads like railway station, hospitals were supplied with power by 3:30pm
• 100% load was restored by 9.30pm evening, the same day.
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Recommendations of the Committee
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5. Technical Recommendations -1 • Review protection schemes along with Immediate review of zone-3
philosophy
• Synchro-phasor measurements from PMUs should be explored for protection systems
• A complete independent audit of time synchronization of DRs, ELs and PMUs
• Frequency band tightening up close to 50 Hz
• Review of UI mechanism
• STUs should immediately enable under frequency and df/dt based load shedding schemes
• Faster algorithm for calculation of TTC.
• The regulatory provisions regarding absorption of reactive power by generating units needs to be implemented
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Technical Recommendations -2• Installation of adequate static and dynamic reactive power
compensators should be planned.
• Functioning of existing PMUs and availability of their output to RLDCs and accuracy of time synchronization should be monitored on daily basis and, if required, corrective actions should be taken on priority basis.
• The Synchro-phasor based WAMS employing PMUs offer a wide applications for real time monitoring and control of the system, specially under the dynamic conditions.
• Adequate number of PMUs should be installed to improve the visibility and real time monitoring of the system.
• Possibility of voltage collapse prediction, sensing global power system conditions derived from local measurements may be explored
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Technical Recommendations -3• Islands: Efforts should be made to design islanding scheme
based on frequency sensing relays so that in case of imminent grid failure, electrical islands can be formed. This will also help in faster restoration of grid.
• The Communication network should be strengthened by putting fiber optic communication system. Further, the Communication network should be maintained properly to ensure reliability of data.
• UPS - RTUs and communication equipment should have uninterrupted power supply with proper battery backup so that in case of total power failure, supervisory control and data acquisition channels do not fail.
• Telemetry facility at all generating station and transmission liens – at the earliest.
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Technical Recommendations -4• A standard procedure for preparatory activities and
sequence of start up may be put in place by the stations to restore units as early as possible particularly in contingencies
• An audit of devices such as HVDC, TCSC, SVC and to ensure their stability features are enabled.
• For smooth operation of grid systems, it is absolutely important that all the power generating and distributing stations are connected on a very reliable telecom network.
(i) A proper network may be built up preferably using MPLS (Multi Protocol Label Switching)
(ii) IT network may be built using dedicated fibres to avoid any cyber attack on the power system.
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6. Policy Recommendations-1
• Implementation of various regulations issued under the Electricity Act, 2003 and look into violation SERIOUSLY.
• Real-time security desk in all the shifts to be manned by engineer capable of carrying out TTC calculations (in NLDC and RLDC).
• LDC and Regulatory Commissions related to non-compliance of regulatory provisions including that for noncompliance of directions and non-payment of UI charges, need review.
• The present organizational set up of Load Dispatch Centres need to be reviewed.
• Training and certification of system operators need to be given focused attention.
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Policy Recommendations-2• There is need to reinforce system study groups in power sector
organizations to analyze the system behavior under different network status/ tripping of lines/outage of generators. Where these do not exist, these should be created.
• Intra-State transmission system needs to be planned and strengthened in a better way to avoid problems of frequent congestion
• Special task force - involving experts from academics, power utilities and system operators, to carry out a detailed analysis of the present grid conditions and anticipated scenarios which might lead to any such disturbances in future.
• Sufficient financial incentives need to be given to certified system operators so that system operation gets recognized as specialized activity.
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7. Proposed protection studyInstallation of
PMUs :
• Phasor Measurement Units (PMU)• These are highly sophisticated instruments to measure
change in voltage/current in milliseconds.
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Relay Protection
Distance Relays
:
• These connected on the transmission lines• Distance relays will sense a fault/disturbance in the grid and
give a trip command to the incomer breaker whenever the grid disturbance exceeds a set limit.
• By opening the incomer breaker, the plant/line is isolated from the grid.
Numeric Relays
:
• These perform mathematical algorithms and to offer very high accuracy & resolution.
• These help in detection of df/dt fault (change in frequency)
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Study of Zone 3 faulty tripping by DR
• Line Fault - Usually any fault in the zone 3 region due to phase-phase fault, phase-ground or other faults will activate the distance relay to open the circuit (Circuit Breaker – VCB/SF6-CB)
• Overloading - If there is overloading this will also create a low impedance on the lines and lead to zone 3 fault alert. Before the far distance relays operate, the local relays should sense this and the appropriate load shedding should be done.
• Failure - If failure of load shedding, the far distance relay operate and this leads to blackout of the entire distribution lines. (This can be a major reason for 30,31st July blackout, So proper considerations should be made for load characteristics)
Please find a example picture in the next slide.
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Distance Relay Operation
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Study of UFR /df/dt under load encroachment conditions
• What really happened – to the protective UFR and df/dt relays? Why didn’t they help in load shedding to improve the declining frequency in Northern region (NR and ER during 31st) on 30th blackout.
• Similarly in the western region the frequency rose up to 51.4Hz, and none of the generators units responded to this frequency hike.
• A separate study has been proposed by the authorities to study regarding the settings of these relays and fix the issues associated.
Study on effects of : TCSC and SVC
What is a compensator?
• A compensator is used in transmission lines/grid/load for voltage stability, reducing net losses, limiting short circuit currents, damping power oscillations by compensation of real and reactive power.
How these compensators affect the protection
distance relay operation?
• The Distance Relays (DR) use impedance measurement to determine the presence of faults.
• The capacitance cancels or compensates some of the inductance of the line and therefore the relay (DR) may perceive a fault to be in its first zone when the fault is actually in the second or third zone of protection.
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TCSC – Thyristor Controlled Series Capacitors
SVC – Static VAR Compensator
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FUTURE?
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8. Why Smart Grids?
To avoid unscheduled transfer of power and blackouts
To monitor the loads and shed loads when stress increase or frequency decrease rapidly.
To improve communication between various LDS’
To maximize cyber safety
To improve efficient Distribution Generation
If you can measure it, you can manage it…
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Smart Grid for India
T&D Losses >30%
BESCOM has begun work on its Rs 87-crore
smart grid project in the
City.
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Features of Smart Grids
Here are some slides on Smart Grid solution from GE
Local Load level
• Smart Metering • On line monitoring portal – with help of SCADA systems• Home automation • Public charging stations – for electric cars/bikes
T & D
level
• Smart Distribution • Load/demand management• Energy Audit • Smart protection controls
Smart
Generatio
n
• Renewable energy source integration or Distribution Generation
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Smart Metering
source: GE
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Smart Substation
source: GE
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Smart Solutions
source: GE
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Smart Communication
source: GE
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Distributed Power Generation
• Distributed Generation is nothing but Generation at site. • The most popular source for distributed generation is solar PV• Germany has the largest percentage mix of solar PV DG at LV
level in their total energy mix. Germany has also developed their own grid codes for LV generation and grid connection (recent policy– reactive power control, using solar grid inverter).
Source: BELELECTRIC
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Distribution level voltage issues (LV)
• The voltage level at the end consumer side face voltage drop due to transmission losses, line impedance (R+JXL) and increase in load.
source: GE
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Pros and Cons of Distributed Generation
• Here the voltage level gets stabilized due to the feed in power from solar. This can greatly reduce the stress and disturbance on transmission lines.
• This can also increase the voltage above a certain level when more solar generators are present and the inverters are forced to trip (overvoltage). This is dangerous and can cause blackouts.
• In 2011, Germany came up with some modifications in their grid codes with reactive power controlled solar inverters.
• Distribution Generation can reduce the overall T&D losses (from HV, MV, to distribution LV).
source: GE
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LV level frequency and voltage control
• Recently grid tie solar inverters come with intelligent active and reactive power control to keep the LV grid voltage and frequency under control.
• As shown in the graph below , when the frequency exceed a certain limit - the active power control comes into play and reduces the overall power output to stabilize the local grid.
• Similarly when there is a voltage increase, the reactive power is absorbed by the GT solar inverters and this stabilizes the output accordingly (check image down).
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Summary• In this presentation we had a look at the various events,
issues and recovery process carried out before and after the 2012,July blackout.
• The recommendation from the committee was also discussed.
• Study on the various protection relays and fault tripping
• Study on effects of capacitor compensators (SVC, TCSC) on protection relays
• Required changes for the future – Smart Grids (Smart metering, communication and renewable energy / distribution generation)
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Reference and CreditsConcept papers:
TCSC FOR PROTECTION OF TRANSMISSION LINEP.S.Chaudhari#i, P. P.Kulkarni#2, R.M.Holmukhe#3, Mrs.P.A.Kulkarni #4 #iScientist, DRDO, Pune,
India, #2DRDO, Pune, India #,,3,4 Bharati Vidyapeeth University College of Engineering, Pune, India.
Pictures and other data: • PMU -
http://www.qualitrolcorp.com/Products/Q_PMU9/18/36_Phasor_measurement_units_%28PMU%29/
• www.erlphase.com(http://www.erlphase.com/downloads/data_sheets/L_PRO_4000_line_protection_relay_ds.pdf)
• http://phasormeasurements.blogspot.in/• Distributed Generation – BELELECTRIC• Blackout picture:
http://www.desismartgrid.com/2012/08/indian-power-grid-blackout-reasons-and-future-requirements/
Blackout official data:• Full report on grid disturbance (CERC Order in Petition No. 167/Suo-Motu/2012 dated 1st
Aug2012). • Status of action taken on recommendation of the enquiry committee on grid disturbance in
northern region on 30th July 2012 and in Northern, Eastern & North-Eastern Region on 31st July 2012.
Smart Grid:• GE - http://www.gedigitalenergy.com/communications.htm• GE - http://www.gedigitalenergy.com/multilin/catalog/Transmission.htm#prl • L&T - http://www.larsentoubro.com/lntcorporate/ebg/html/grid_islanding.htm • SMA• BESCOM - http://www.deccanherald.com/content/288701/bescom-ropes-us-firm-smart.html • Indian Smart Grid Task Force