4. CERC report
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”
4
5. 2. India National Grid – Hierarchy
Indian Grid -
NLDC
Southern
New Grid Region - RLDC
Northern Western Eastern North-Eastern
SLDC
Region -RLDC Region - RLDC Region - RLDC Region - RLDC
SLDC SLDC SLDC SLDC
SLDC - State Load Dispatch Centre
5
6. Types of Transmission line
• Mostly within the state
220kV
• Long distance (State-State, Region – Region)
400kV
• Long distance state – Region- Region transmission
765kV
• Latest technology for long distance power transmission with minimum losses.
500 kV - • These are much popular in the off-shore wind farm transmission lines in the UK
HVDC
HVDC – High Voltage Direct Current
These systems use direct current for the bulk transmission of electrical power, in contrast with the more common
alternating current systems. For long-distance transmission, HVDC systems may be less expensive and suffer lower
electrical losses. 6
8. What is grid disturbance?
A grid is said to be
disturbed when :
f) there is a power a) there is an under
failure in the grid voltage (U/V)
e) there is a rapid fall
b) there is over
or rise in frequency (
voltage (O/V)
+dF/dT or -dF/dT )
d) there is over c) there is under
frequency (O/F) frequency (U/F)
8
10. 29th July – evening before blackout
The 400 kV Bina- Gwalior-Agra-
2 was under planned shutdown
since 28thJuly 2012 for up-
gradation work to 765kV.
At 10:18pm, 400 kV Zerda- 28th July 2012 At 3:15pm, 29th July - 220
Kankroli Emergency outage kV Kota-Badod Tripped due
for a period of two hours to to operation of distance
take out one Tool & Plant (T protection three phase
& P) which got stuck with Zone-1 indications at Badod
one polymer insulator. end.
10:18pm 3:15pm
At 3:40pm, 220 kV Binmal
9:45pm 3:40pm (PG)- Sirohi - Phase to earth
At 9:45pm, 400 kV Bhinmal-
fault. The two 220 kV
Kankroli Tripped due to
outlets to Bhinmal(RVPNL)
insulator de-capping.
and one to Sanchore were
in service from Bhinmal.
10
13. Reason for blackout -30th July 2012 Summary
400kV Bina-Gwalior-Agra 2
line was under planned
shutdown. This caused stress
Once almost all the 400kV on other lines. Failure in load
lines tripped overnight management and planning
(from WR to NR) and even
many 200kV lines tripped, Large amount of
now the power from WR unscheduled import of
started to flow to NR power by the Northern
though ER. This caused region from western and
power swings in the ER and eastern region.
more lines started tripping
and caused a complete
blackout. Action was not taken to
reduce the Total Transfer
Capability (TTC) after shut
Sipat stage-1 plant was down of Zerda-Kankroli 400
under trial operation and KV line, . The TTC is shown
caused unscheduled as 2000 MW before and
injection of power. after the shutdown of 400
KV line.
Some gas and thermal plants Lack of observation and
where tripped in NR due to coordination!
forced outage and shortage
of coal.
Irregular Maintenance and
lack of monitoring
13
15. Restoration – after blackout 30 th July
• The blackout 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!
15
19. 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.
19
21. 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.
21
22. Reason for blackout 31st July 2012 Summary
Loss 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.
The UFR load shedding
was not adequate to bring Weak Inter-regional
the frequency back to a Corridors due to multiple
safer level of 49.5 Hz and outages
above.
Inadequate Response by
SLDCs to RLDCs’ High Loading on 400 kV
instructions on this day Bina-Gwalior-Agra link
also to reduce overdrawl by -NR utilized Unscheduled
the NR utilities and Interchange (UI) and this
underdrawal by the WR lead to overloading
utilities
22
23. 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.
23
25. 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
25
26. 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
26
27. 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.
27
28. 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.
28
29. 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.
29
30. 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.
30
31. 7. Proposed protection study
• Phasor Measurement Units (PMU)
• These are highly sophisticated instruments to measure change in
Installation voltage/current in milliseconds.
of PMUs :
31
32. Relay Protection
• These connected on the transmission lines
• Distance relays will sense a fault/disturbance in the grid and give a trip command
Distance to the incomer breaker whenever the grid disturbance exceeds a set limit.
Relays: • By opening the incomer breaker, the plant/line is isolated from the grid.
• These perform mathematical algorithms and to offer very high accuracy &
resolution.
Numeric • These help in detection of dF/dT fault (change in frequency)
Relays:
32
33. 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.
33
35. 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.
35
36. Study on effects of : TCSC and SVC
How these compensators affect
What is a compensator? the protection distance relay
operation?
• A compensator is used in transmission • The Distance Relays (DR) use
lines/grid/load for voltage stability, impedance measurement to determine
reducing net losses, limiting short circuit the presence of faults.
currents, damping power oscillations by
compensation of real and reactive • The capacitance cancels or compensates
power. 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.
TCSC – Thyristor Controlled Series Capacitors
SVC – Static VAR Compensator
36
38. 8. Why Smart Grids?
If you can measure it, you can manage it…
To improve efficient
Distribution
To maximize
Generation
cyber safety
To improve communication
between various LDS’
To monitor the loads and shed
loads when stress increase or
frequency decrease rapidly.
To avoid unscheduled transfer
of power and blackouts
38
39. Smart Grid for India
BESCOM has
begun work on
its Rs 87-crore T&D
smart grid Losses
project in the >30%
City.
39
40. Features of Smart Grids
• Smart Metering
• On line monitoring portal – with help of SCADA systems
• Home automation
Local Load level • Public charging stations – for electric cars/bikes
• Smart Distribution
• Load/demand management
• Energy Audit
T & D level • Smart protection controls
• Renewable energy source integration or Distributed Generation
Smart
Generation
Here are some slides on Smart Grid solution from GE
40
45. 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
45
46. 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
46
47. 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.
• Distributed Generation can reduce the overall T&D losses (from HV, MV, to distribution LV).
source: GE
47
48. 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).
48
49. 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)
49
51. Reference and Credits
Concept papers:
TCSC FOR PROTECTION OF TRANSMISSION LINE
P.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
51
