Srldc 28 May2013_congestionEnergy & Power Meet

1. Congestion Management
Workshop organized at SRPC
28th May 2013
Bengaluru

2. Outline
• Congestion definitions
• Congestion Management in different time horizons
– Long term
– Medium term
– Operational Planning
– Real time
• CERC procedure on congestion charges in real time

3. Pillars of Market Design
Sally Hunt – ‘ Making Competition Work in Electricity’

4. Congestion in Power System
“Congestion is a situation where the demand
for transmission capacity exceeds the
transmission network capabilities, which
might lead to violation of network security
limits, being thermal, voltage stability limits or
a (N-1) contingency condition.”
CIGRE_WG_C5.04_TB_301
4

5. Indian Electricity Grid Code 2010
• ‘Congestion’ means a situation where the
demand for transmission capacity exceeds the
Available Transfer Capability;
First formal definition of congestion in power
system in our statute wef 3rd May 2010!!!

6. 6

7. Visibility of congestion
• Visible to the market players
– “If for a given interconnection, there is more demand for
cross border capacity than commercially available, the
interconnection is also treated as congested, meaning no
additional power can be transferred. This congestion is
visible for market players as a limit on their cross-border
transactions.”- CIGRE_WG_C5.04_TB_301
• Invisible to the market players
– “It is possible that even though the available commercial
interconnection capacity is not fully allocated to market
players, some lines, being internal or cross-border, become
overloaded. This physical congestion is a problem of the
System Operator and has to be dealt with by this entity.”
CIGRE_WG_C5.04_TB_301
7
To be handled before-the fact
To be handled in real-time

8. Congestion visible to the market
• “The more transactions and the more meshed
the network, the higher the chance for
mismatch between commercial exchange and
physical flows.” CIGRE_WG_C5.04_TB_301
 Congestion
 Sign of growth and vibrant market
 Natural corollary to Open Access
 Existing transmission system was not planned with
short-term open access in mind
 Security margins have been squeezed
 ‘Pseudo congestion’ needs to be checked
8

9. Real-time Congestion types
• Internal congestion (Intra-zonal)
– Within a single System Operator’s control area
• Cross-border (Inter zonal)
– Also called seams issue
– Several System Operators involved
Was not experienced
-Regional grids were small
-Trades were limited
9
Experienced occasionally under
- Grid Contingencies
- Skewed conditions in grid
Aggressive Open Access trades

10. Open Access Theory & Practice
Forum of Regulators report, Nov-08
“For successful implementation of OA,
the assessment of available transfer
capability (ATC) is very important. A
pessimistic approach in assessing the
ATC will lead to under utilisation of the
transmission system. Similarly, over
assessment of ATC will place the grid
security in danger.”
10

11. Declaration of Security Limits
• “In order to prevent the violation of security
limits, System Operator SO must define the
limits on commercially available transfer
capacity between zones.” CIGRE_WG_C5.04_TB_301
• “System Operators try to avoid such
unforeseen congestion by carefully assessing
the commercially available capacities and
reliability margins.” CIGRE_WG_C5.04_TB_301
11

12. Cross border capacity available for trade
• “Physical capacity connecting zones A and B is
sum of 1-3 and 2-3 physical line capacities.
However, the cross border capacity available
for commercial trade would be less or at most
equal to the sum of capacities of cross border
lines individually.” CIGRE_WG_5.04_TB_301
1
2
3
A B
12

13. 13
Intra-day STOA
Day-ahead STOA
Collective (PX) STOA
First Come First Served STOA
Advance Short Term Open Access (STOA)
Medium Term Open Access (MTOA)
Long Term Open Access (LTOA)
Reliability Margin (RM)
Available Transfer Capability is
Total Transfer Capability less Reliability Margin
TTC ATC
RM

14. Diagram- Europe
POWERGRID 14
NTC map for season:
Winter 2008/2009

15. Gross Transmission Capacity (GTC) vis a vis
Net Transmission Capacity (NTC) in Europe
Corridor GTC NTC Difference NTC/GTC (%)
France to United Kingdom 2000 2000 0 100%
United Kingdom to France 2000 0 2000 0%
Denmark (East) to Sweden 2010 1700 310 85%
Sweden to Denmark (East) 2010 1300 710 65%
Italy to Slovenia 2017 480 1537 24%
Slovenia to Italy 2017 380 1637 19%
Austria to Hungary 2124 500 1624 24%
Hungary to Austria 2124 200 1924 9%
Sweden to Finland 2230 1800 430 81%
Finland to Sweden 2230 1600 630 72%
Czech Republic to Austria 2249 600 1649 27%
Austria to Czech Republic 2249 0 2249 0%
Italy to Austria + Slovenia 2274 0 2274 0%
Lituania to Kaliningrad 2287 700 1587 31%
Slovakia to Hungary 2492 1100 1392 44%
Hungary to Slovakia 2492 200 2292 8%
Poland to Slovakia 2504 750 1754 30%
Slovakia to Poland 2504 750 1754 30%
Courtesy:
ENTSOE 15

16. NTC Vs GTC Among EU Countries
For Corridors Up to 1000 MW

17. NTC Vs GTC Among EU Countries
For Corridors Up to 5000 MW

18. NTC Vs GTC Among EU Countries
For Corridors Up to 16000 MW
Gross Total Capacity & Net Transfer Capability Among EU Countries
y= 0.21x
0
2000
4000
6000
8000
10000
12000
14000
16000
0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 11000 12000 13000 14000 15000 16000
Gross Total Capacity(MW)
NetTransferCapability(MW)
~ 21%

19. NTC As % of GTC Among EU Countries

20. Transmission Capacity ( TC ) vis-à-vis
Available Transfer Capability ( ATC ) in Brazil
TRUNK
TC
( MW )
ATC
( MW )
ATC/TC
(%)
North - Southeast/Midwest
Interconnection
( from North to Southeast)
4200
n-1 3400 81
n-2 1700 40
WITH SPS 4100 98
North - Southeast/Midwest
Interconnection
( from Southeast to North )
n-1 3000 71
Foz do Iguaçu – Ivaiporã
765 kV trunk
6450
n-2 3600 56
WITH SPS 5300 82
Southeast/Midwest - South
Interconnection
17180 n-2 9500 55
440 kV trunk
feeding São Paulo
14500
n-2 9600 66
WITH SPS 10200 70
20Courtesy: ONS Brazil

21. Handling congestion in different time horizons
• Long term planning……….3-5 years time frame
– Several scenarios and uncertainties to be factored
– Probabilistic vs deterministic
– High Impact Low probability events
– Operational feedback by NLDC/RLDCs as per
section 4j of NLDC Rules 2005.
http://www.posoco.in/documents/operational-
feedback

22. Handling congestion in different time horizons
• Medium term planning……….0-3 years time
frame
– Network augmentation difficult
– Temporary re-configuration of network possible
– Pro-rata still the main method in Medium Term
Open Access (MTOA)
• Auctions another possibility

23. Lanco Amarkantak (2 x 300 MW)
400 kV Lanco to Sipat section used to constraint West to East TTC

24. Lanco Amarkantak (2 x 300 MW)
Contingency
Arrangement
Implemented
in May 2010

25. Contingency arrangement at CGPL Mundra in 2011
Single line sketch showing proposed bunching arrangement for Bhachau to Vadavi & Chorania D/C TL
D/C
CGPL
Mundra
400 kV
Bhachau S/S
PGCIL
S/C S/C
400 kV 25 km 400 kV
Chorania S/S D/C Bunching point D/C Vadavi S/S
GETCO 192 kms 257 kms GETCO

26. 400 kV Maithon-Koderma arrangement
• Final arrangement
– 400 kV Maithon- Gaya D/C (Quad)
– 400 kV Koderma-Gaya D/C (Quad)
– Forest clearance and ROW problem near Gaya
• Interim arrangement
– 400 kV Maithon-Koderma D/C

28. Benefit
• Reduction in flow of 400 kV Kahalgaon-
Biharsariff D/C and Kahalgaon–Banka-
Biharshariff D/C, which is a constraint for ER-
NR TTC
• Enhancement of ER-NR TTC.

29. Congestion in Operational Planning horizon
• Priority based rules
• Pro-rata rationing
• Auctioning
– Explicit Auction…………e-bidding under STOA
– Implicit Auction…………Power Exchange Day Ahead
– Hybrid
• Market splitting
• Market coupling
29

30. Congestion Management
Lessons learnt in Indian context
• Firmness in STOA schedules
– “Use it or Lose it”
• Valuing transmission instead of pro rata
• Market splitting
30

31. Congestion Management in real time
– Classical
– Compliance to Standards and Grid Code
– Topology change
– Re-dispatch
– Curtailment
– Market based
– Commercial signals (Congestion Charge)
– Ancillary Market
• Out of merit generation scheduled to pool
• Reactive power charge- synchronous condenser operation
31

32. Congestion Management in real time
• Counter trading
• Re-dispatching (Out of merit generation)
• Locational Marginal Pricing (LMP)
λnode = λ deviation price + λcongestion charge + λlosses
• Transmission Loading Relief (TLR)
All these methods would result in significant rise in
total cost.
“Price for system security”
32

33. Regulatory initiatives
• Modifications in Grid Code & other regulations
– Frequency band tightening
– Cap on UI volume, Additional UI charge
– Inclusion of new definitions (TTC, ATC, Congestion)
• Congestion Charge Regulation
– Congestion Charge Value, Geographical
discrimination
– Procedure for Assessment of Transfer Capability
– Procedure for Implementation of Congestion Charge
33

34. Congestion charges in real time……..CERC orders
• Order dated 7th Nov 2007 in petition no 116/2007
– Congestion charges @300 paise/kWh for Northern region
– Flexibility given to NRLDC
– Irrespective of frequency
– Applied on two occasions in NR.
• Regulations dated 22nd Dec 2009 on congestion charges
in real time
– Procedure approved by CERC vide order dated 11th June 2010
– Modified procedure ordered on 22nd April 2013

35. Imposition of Congestion Charge in NR on 31st Jan-08
1400 hrs0945 hrs 1930 hrs

36. Antecedent condition
31st Jan-08
Morning hours
Congestion Charge
1400 hrs0945 hrs 2000 hrs
Improvement in voltage profile
subsequent to imposition of
congestion charge
31st Jan-08, 1400 hrs- 1830 hrs

37. Imposition of Congestion charge in NR
15th September 2008, 0300 hrs to 0800 hrs
Exactly a week later, NTPC Dadri complex plus HVDC Rihand Dadri bipole tripped
During night hours. Low load conditions in NR averted a major blackout.

38. Comments on congestion charge
procedure submitted to CERC in
Jan/Feb 2010

39. Congestion alleviation
Gen: G2
Load: P2
Gen: G1
Load: P1
Downstream system
Upstream system
Line flow = (G1 – P1) OR (P2 – G2)
For congestion alleviation
viz. reducing flow
on the lines connecting the two systems
both upstream and downstream actions
are required for maximum benefit
considering the
frequency dependence on load

40. Congestion alleviation –only upstream actions
Gen: G2
Load: P2
Gen: G1
Load: P1
Downstream system
Upstream system
Line flow = (G1 – P1) OR (P2 – G2)
For a reduction of generation ∆ P
in upstream system,
the line flow would reduce by
∆ P ( P2 )
(P1 + P2)

41. Congestion alleviation – only downstream
actions
Gen: G2
Load: P2
Gen: G1
Load: P1
Downstream system
Upstream system
Line flow = (G1 – P1) OR (P2 – G2)
For a reduction of load ∆ P
in downstream system,
the line flow would reduce by
∆ P ( P1 )
(P1 + P2)

42. Congestion alleviation – both upstream and
downstream actions
Gen: G2
Load: P2
Gen: G1
Load: P1
Downstream system
Upstream system
Line flow = (G1 – P1) OR (P2 – G2)
For a reduction of generation and load ∆ P
each in upstream and downstream system,
the line flow would reduce by
∆ P

43. Relative size of systems
Downstream system
Upstream system
If upstream system is very small
compared to the downstream system
maximum benefit accrues from
generation reduction upstream
viz. actions in the smaller sub-system

44. Relative size of systems
Downstream system
Upstream system
If downstream system is very small
compared to the upstream system
maximum benefit accrues from
load reduction downstream
viz. actions in the smaller sub-system

45. CONGESTION MANAGEMENT
PROCEDURES ::
-REV-1 DTD.22/04/13
• Deviations w.r.t Procedure:
-Rev-0 Dtd.05/04/10
• Congestion charge procedure:
- Declaration
- Applicability

46. Areas under which modifications have been carried out
• Methodology for assessment of TTC/TRM/ATC
• Declaration of congestion in real time
• Applicability of congestion charge

47. Declaration of Congestion in real time-Procedures
• 5.1. SLDCs/ RLDCs/ NLDC shall have a display available in their web-sites
showing TTC, TRM, ATC declared in advance. Real time power flow in the
corridor for which TTC has been declared shall be displayed alongside for
comparison. The voltage of the important nodes in the grid
downstream/ upstream of the corridor shall also be displayed(Format II)
• 5.2. A corridor shall be considered congested under the following
circumstances:
• 5.2.1. Grid voltage in the important nodes downstream/ upstream of the
corridor is beyond the operating range specified in the IEGC and/or
• 5.2.2. The real time power flow along a corridor is such that n-1 criteria
may not be satisfied.
• 5.2.3. One or more transmission lines in the corridor are loaded beyond
the normal limit specified in CEA Manual on Transmission Planning
Criteria.

48. Declaration of Congestion in real time-Procedures
• 5.3. Whenever actual flow on inter/ intra regional link/ corridor exceeds ATC and
security criteria as mentioned in clause 5.2 above are violated RLDC, NLDC may
issue a warning notice. In case SLDC observes congestion within the intra State
grid it shall inform the respective RLDC which in turn shall inform the NLDC. The
notice for congestion shall be communicated to all the Regional entities
telephonically or through fax/ voice message/ e-mail and through postings on
website and making the same available on the common screen at NLDC/ RLDCs/
SLDCs. The format of the notice is enclosed as Format III.
• 5.4 If the power flow on the corridor is as per the schedule, but the congestion
has been caused by forced outages of a transmission line in the corridor, which
occurs after the drawal schedule has been fixed, then open access transactions
shall be curtailed in the priority given in the Central Electricity Regulatory
Commission (Grant of Connectivity, Long-term Access and Medium-term Open
Access in inter-State Transmission and related matters) Regulations, 2009
followed by revision of TTC, TRM and ATC.

49. Declaration of Congestion in real time-Procedures
• 5.5 If the power flow on the corridor is as per the schedule and the
corridor is congested due to either of the circumstances mentioned in
clauses 5.2.1 and 5.2.3 of this procedure then TTC, TRM and ATC shall be
revised accordingly.
• 5.6 If violation of TTC limits persists for 2 time-blocks not counting the
time-block in which warning notice was issued by RLDC and no
affirmative action is taken by the defaulting agency, NLDC/ RLDC(s) shall
issue a notice for application of congestion charge. This notice shall be
communicated to all the concerned Regional entities telephonically or
through fax message and through postings on website and the same
shall also be made available at the common screen at NLDC/ RLDCs/
SLDCs. The format is enclosed as Format-IV.

50. Declaration of Congestion in real time-Relevant Modifications
• 5.2.2:The real-time power flow along a corridor exceeds the ATC for that
corridor for continuously one time block of 15-minute
-deleted under points for consideration of corrridor congestion
• The real time power flow along a corridor is such that n-1 criteria may not be
satisfied.
-modified clause
• 5.6:If congestion persists for 2 time-blocks not counting the time-block in
which warning notice was issued by RLDC and no affirmative action by the
defaulting agency is taken, NLDC/ RLDC(s) shall issue a notice for application
of congestion charge. This notice shall be communicated to all the
concerned
-deleted under applicability of congestion where ATC was meant
• If violation of TTC limits persists for 2 time-blocks not counting the time-
block in which warning notice was issued by RLDC and no affirmative action
is taken by the defaulting agency, NLDC/ RLDC(s) shall issue a notice for
application of congestion charge.
-inserted clause

51. Applicability of Congestion Charge-Summary
• 6.1. Congestion Charge –Rs.5.45/- per unit(not defined in the procedures)
• 6.2. Congestion charge would be levied for
• a) over drawal or under-injection in the importing control area and
• b) under drawal or over-injection in the exporting control area.
• 6.3. Congestion charges may also become applicable for an intra-regional corridor
of one region, if the congestion is attributable to other regional entities of other
region.
• 6.4. Congestion charge shall be applicable only after two time blocks from the
time of issuing the notice, not counting the time block in which notice is issued.
• 6.5. Congestion charge shall be withdrawn after the power flow on the affected
transmission link/ corridor has come down to the ATC and remains at this level
for one time block. NLDC/ RLDC shall communicate to all concerned Regional
entities telephonically or through fax message/ e-mail and through postings on
website and making available the same on the common screen available at
NLDC/ RLDCs/ SLDCs for lifting of congestion charge. The format of the notice is
enclosed as Format-V.

52. Applicability of Congestion Charge-Relevant Modifications
• 6.2:At frequency below 50 Hz, congestion charge would be levied for
over drawal or under-injection in the importing control area and at
frequencies above 50 Hz, congestion charge would be levied for under
drawal or over-injection in the exporting control area
-deleted under applicability of congestion charge
• 6.2:Congestion charge would be levied for
a) over drawal or under-injection in the importing control area and
b) under drawal or over-injection in the exporting control area.
-inserted
• Minor changes in format-I

53. Methodology for TTC/RM/ATC computation-Relevant Modifications
• 3.6.9:Normal operating limit for an Inter connecting transformer shall be 90 % of its
Maximum Continuous Rating (MCR)
-deleted
• 3.6.9Permissible Normal and emergency limits for transmission elements shall be
as defined in the (CEA Manual on Transmission Planning Criteria).
-final clause
• 3.9During assessment of Total Transfer Capability it shall be ensured that:
• 3.9.1. All transmission element loadings in the base case are within normal
operating limits and the voltages remain within operating range defined in the
IEGC.
• 3.9.2. All transmission element loadings after a credible contingency are within
emergency ratings and grid voltage is within the operating range as defined in the
IEGC.
-deleted
• 3.9:During assessment of Total Transfer Capability it shall be ensured that the
conditions specified in CEA Manual on Transmission Planning Criteria are met after
credible n-1 and n-1-1 contingencies.
-final clause

54. Methodology for TTC/RM/ATC computation-Relevant Modifications
• 3.10.4: Stability under n-1-1 contingency of a temporary single phase to
ground fault on a 765 kV line close to the bus or a permanent single
phase to ground fault on a 400 kV line close to the bus
• 3.10.5:Angular difference of 30 degrees between adjacent buses under
n-1 contingency
-additional insertion
• 3.11.2: Single largest anticipated in feed into the control area/ group of
control area (which could be a combination of States for the purpose of
Power Exchange and for others)/ region.
-deleted under basis of TRM computation

55. Thank You