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SUBSTATION PLANNING
By
D.Chethan.
Asst. Executive Engineer (Ele),
Planning Section, KPTCL.
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SUBSTATION
A Substation is an assembly of
apparatus which transform the
characteristics of electrical energyfrom one form to another.
A Substation is a link between the
generation of power and the
ultimate consumer.
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ALL-INDIA(as on 31-03-2007)
Energy Requirement (MU) 690587
Energy supply (MU) 624495
Energy Shortage 9.6%
Peak Demand (MW) 100715
Peak Demand met (MW) 86818
Peak Deficit 13.7 %
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ALL-INDIA(11thPlan & 12thPlan Period)
Year Energy
Requirement (BU)
Peak
Demand
(MW)
2011-12 1038 1,52,000
2016-17 1470 2,18,200
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POWER SECTOR REFORMS INKARNATAKA
Karnataka Electricity Reforms Act, 1999 was passedand came into force with effect from 01.06.1999.
Karnataka Electricity Board restructured in 1999, new
successor entities
KPTCL and V V N L
incorporated.
Karnataka Electricity Regulatory Commission
established and made functional from November 1999.
Memorandum of Agreement entered into withGovernment of India to implement Power Sector
Reforms.
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Detailed Policy Statement issued in January 2001,which mentions that Distribution Companies will be
privatized.
Independent Power Producers Policy also announced.
Distribution unbundled from KPTCL. Four Distribution
Companies, namely, BESCOM, MESCOM, GESCOM and
HESCOM were formed and made operational from
01.06.2002.
To enable the ESCOMs to start operations with cleanbalance sheets, Government took over Rs. 1050 crores
of long-term loans and Rs. 866 crores of bad and
doubtful consumer receivables of KPTCL.
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MINISTRY OF POWER(JUNE 2006)
1. Andhra Pradesh
2. Gujarat
3. Delhi
4. Karnataka
This is based on a Study made by
CRISIL and ICRA
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PERFORMANCE RATING OF KARNATAKAs POWERSECTOR BY MINISTRY OF POWER(JUNE 2006)
1.
Andhra Pradesh2. Gujarat
3. Delhi
4. Karnataka
This is based on a Study made by
CRISIL and ICRA
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PROBLEMS FACING THE POWER SECTOR
GENERATION
Difficulties faced by KPCL in getting domestic coal
Protests against proposed new power projects by environmentalistsand local people
ALLOCATION OF POWER FROM CENTRAL GENERATING STATIONS
Allocation to Karnataka in CGS power is disproportionately small
Reduction of Karnatakas share in unallocated quota
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TRANSMISSION AND DISTRIBUTION
AT&C losses of 33.2 % and T&D losses of
29.68% are too high
FINANCIAL PROBLEMS
Non-payment of dues by IP set consumers and Gram
Panchayats
Capital expenditure financed solely by borrowings (except
for works under Rajiv Gandhi Grameen Vidyutikaran Yojana)
Unfavourable Tariff Orders passed by KERC
hardly any increase in tariffs
With increasing consumption of power by IP sets and no
increase in IP set tariff, subsidy burden will not come down
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Structure of Power Sector
Generation KPCL IPPS NCE Projects PCKL
KPTCL
400 kV (4 nos)
220 kV (61 nos)
110 kV (233 nos)66 kV (400 nos)
Construction
&
Maintenance
Divisions
BESCOMCESCMESCOMHESCOMGESCOMHUKKERI
33 kV
Substations(283 nos) ,
Lines &
11 KV Lines
Consumers
Operation &
Maintenance
Divisions
Transmission
Distribution
CGS
Inst. Cap. 8154 MWas on 31.08.2007
Handled 40380 MU
in 2006-07
Energy Sales
28454 MUs in
2006-07
1.46 Crs.
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Power Sector Companies in Karnataka
KPCL Karnataka Power Corporation Limited
PCKL Power Company of Karnataka
KREDL Karnataka Renewable Energy
Development Corporation Ltd.
KPTCL Karnataka Power Transmission
Corporation Limited
BESCOM Bangalore Electricity Supply
Company
MESCOM Mangalore Electricity Supply
Company
CESC Chamundeshwari Electricity SupplyCorporation
HESCOM Hubli Electricity Supply Company
GESCOM Gulbarga Electricity Supply Company
Govt. of Karnataka
owned Companies
G i I ll d C i
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Generator-wise Installed CapacityAs on 26.12.2007
NCE18%
IPPs &Others
4%
KPC-
Hydel
42%
CGS
16%
KPC-
Thermal21%
Source Inst.Cap.
(MW)
%
KPC-Hydel 3392 41
KPC-Thermal 1598 20
CGS (alln. Only) 1315 16
NCE 1543 19
IPPs & Others 346 4
Total 8194 100
Break-up for NCE Projects (MW)
Wind 838
Co-gen. 355
Mini-Hydel 253
Bio-Mass 97
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7620
7353
70076
085
6085
5939
12
00
85
8
1431
47
3
64
0
1134
0%
10%20%
30%
40%
50%
60%
70%
80%
90%
100%
02-03 03-04 04-05 05-06 06-07 07-08
MWs
Unrestricted Demand Shortage
Demand shortage
16%10%
7%
17%10% 16%
84% 90% 93% 83% 90% 84%
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7620
7353
70076
085
6085
5939
12
00
85
8
1431
47
3
64
0
1134
0%
10%20%
30%
40%
50%
60%
70%
80%
90%
100%
02-03 03-04 04-05 05-06 06-07 07-08
MWs
Unrestricted Demand Shortage
Demand shortage
16%10%
7%
17%10% 16%
84% 90% 93% 83% 90% 84%
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41075
40379
34641
33110
31210
29279
5651
3634
5533
4515
3439
4538
0
5000
10000
15000
20000
25000
30000
35000
40000
45000
50000
02-03 03-04 04-05 05-06 06-07 07-08
MUs
Energy Met / Estimated Shortage
Energy shortage
13%10%
12%14%
8% 12%
87% 90% 88% 86% 92% 88%
Capacity Addition Programme (
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Capacity Addition Programme (Projects in KARNATAKA)
KPCL Projects Capacity (MW)
1 BTPS unit I & II - Thermal project 1000
2 RTPS 8thUnitThermal Project 250
3 Varahi IIHydel Proejct 230
4 GundiaHydel Project 400
5 Bidadi Combined Cycle Plant 1400
6 Kalgurki _ Thermal Project 1000
7 YermarasThermal Project 10008 AnnechakanahalliThermal Project 1000
9 YadgirThermal Project 1000
10 EdlapurThermal Project 500
11 BTPS unit IIIExpansion Project 500
12 Kudathini - Thermal Project 1500
PCKL Projects
13 Chamalapura 1000
14 Jewargi 1000
15 Ghataprabha 1000
TOTAL 12780
During 11thPlan PeriodFY2008FY 2012
NOTE: Above capacity addition doesnt include share in CGS Projects
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Capacity Addition Programme
IPPs Capacity (MW)
16 Nagarjuna 1015
17 Euro India Power Canara 500
TOTAL 1515
GRAND TOTAL 14295
S b t ti & T Li
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As on 01.01.2008
Voltage Level No. of stationsTr. Line in
CKMs
400 kV 4 1978220 kV 63 8656
110 kV 242 7606
66 kV 415 8306
33kV 285 7468
Total 1009 34014
Substations & Tr Lines
T&D L R d ti
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T&D Loss Reduction
27.21
38.02
35.50
35.86
31.95
30.88
29.44
29.38
29.68
25
30
35
40
99-2000 2000-01 2001-02 2002-03 2003-04 2004-05 2005-06 2006-07 2007-08
(in%)
projected
A T & C L
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A T & C Loss
42.3
36.38 36.99
32.3
43.31
25
30
35
40
45
50
2002-03 2003-04 2004-05 2005-06 2006-07
(in%)
Overall
SECTOR
B
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Revenue & Expenditure Growth
8773
7933
69406295
10550
9475
79917918
3000
4000
5000
6000
7000
8000
9000
10000
11000
12000
2003-04 2004-05 2005-06 2006-07
(Rs.Crs.)
Revenue Expenditure
KPTCL & ESCOMs
ompany w se apex
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ompany-w se apex
0
100
200
300
400
500
600
700800
900
1000
KPTCL BESCOM MESCOM HESCOM GESCOM
(Rs.Crs.)
2004-05 2005-06 2006-07
Year KPTCL BESCOM MESCOM & CESC HESCOM GESCOM TOTAL
2004-05 472 334 61 213 90 1170
2005-06 479 432 127 199 128 1365
2006-07 870 563 310 307 171 2221
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Capex plan2007-08 to 2009-10
YearTransmission Distribution Total
2007-08 2400 3997 6397
2008-09 2100 1716 3816
2009-10 1600 2171 3771
TOTAL 6100 7884 13984
Rs. Crores
Capex
incurred(till Nov 07)
1067 700 1767
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Purpose & Necessity
Generated power to be evacuated to
load centers for consumption.
Generating stations are far of from loacenters.
The process of
Generation Transmission Consumption
(in 10s kV) (in 100s kV) (in 100s V)
Needs Substation at various points
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Classification
Substations are classified into
Generating Substations.
Grid Substation mainly 400kV &220kV class.
Distribution Substationmainly of
110kV,66kV,33kV class
Generating Substation are step-upstations
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Classification
Grid Substations are mainnodal stations betweenGenerating Substations &Distribution Substation.
Grid Substation may be
Switching Substations
Step-down stations Distribution Substations are
step down stations
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Substation Planning
AIM
To minimize constructional
and operational cost.To minimize loss.
To supply power safely
and reliably to theconsumer
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Substation Planning..
Sub-station planning considers
the location, size,voltage,
sources, loads and ultimatefunction
Lack adequate planning
results in unnecessary andcostly modifications
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Planning Process Long range planning
Detailed load forecasting
Locating load centers
Identifying Substation location and voltage
class Developing upstream network
Detailed Planning
Valid requirements & criteria
Appropriate guidelines Construction drawings & associated
documentation
The planning would test the engineersability to find an acceptable design from
diverse constraints
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Long Range Planning
Long range plan identifies therequirement of sub-station not for
its initial use but also for some
years in future
It will consider ultimaterequirements in the initial design
itself
It would make economic
comparison to discover what
provisions are necessary for ease
of addition
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Planning methods
Substation & associated network
planning method can be classified
into Heuristic
Mathematical Optimization
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Heuristic method
Based on Intuitive analysis i.e.,
Experience and analysis
Not a strict Mathematical Optimization
It is widely used due to its straight
forwardness, flexibility, speed of
computation & easy involvement of
personnel in decision making
Has ability to obtain a comparatively
optimal solution which meets practical
engineering requirements.
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Mathematical Optimization
Formulation of design requirements
as an operational mathematical
planning model and solved by anoptimization algorithm.
It posses more strictness in theory
Very difficult to solve a large scale
planning problem due to largenumber of planning variables and
complex constraints
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Perspective Planning
The present practice is to combine
both heuristic and Mathematical
optimization methods Perspective planning followed in
KPTCL is combination of Heuristic
and Horizon year planning method
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Perspective Planning
The Horizon year is so selected
that projected demand &
generation availability are knownreasonably well
Planning is based on guidelines
prescribed by CEA, Regulatory
Commission and Utilities
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Planning criteria
Substation capacity should not
exceed the limit set
If peak load of the station exceeds90%
New stations are to be proposed
Upgraded to higher voltage
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Table 1 : Substation Maximum Capacity
SL.
No
Voltage Ratio
(kV)
By KPTCL in
MVA
By KERC in
MVA
1. 400/220 1000 1000
2 220/110, 220/66 300 320
3 110/33 40 150*
4 110/11 20 150*
5 66/11 63** 75
6 33/11 10 --
* The combined capacity of 110/33kV and110/11kV levels.
** - 63MVA in case of Urban areas, 25MVA in
case of Semi-urban and 12.6/16MVA in rural
areas
Pl i it i
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Planning criteria Size & Number of ICTs
Outage of single unit should notoverload the remaining ICTs orunderlying system
Size & Number of HT/EHTTransformer
Outage of single unit should notlimit the supply of 80% station load
By not overloading the remainingtransformer
By interconnection with adjacentsubstations
The distance between twosubstation is dependent on density
of load
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Reactive Power Compensation
Table 2 : Shunt capacitor compensation
MVA at
11kV Bus
Shunt Compensation
MVA MVA
< 30
1 x 5 MVAr (at12.1 kV) for each transformer at
11 kV Bus
MVA > 30 1 x 20 MVAr (at 72 kV) at 66kV Bus , 1 x 20
MVAr (at 121 kV) for 110 kV Bus
Pl i C it i N t k
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Planning Criteria -Network
Addition of Network to avoid overloading Incase the Substation is to be uprated to
higher voltage at a later date the
network be built for that higher voltage
If 110kV or 66kV station be uprated to220kV station at a later date, the
addition line be of 220kV class but
charged on 110kV or 66kV
If three or more circuits of same voltage
class is envisaged Next higher voltage
may be considered
Every station be fed by a D/C line orshall
have provision for alternate feeding
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Voltage limits as per CEATable 3 : Specified Voltage Limits
Voltage Minimum
(pu)
Minimum
(kV)
Maximum
(pu)
Maximum
(kV)
400 kV 0.95 380 1.05 420
220 kV 0.9 198 1.11 244.2
110 kV 0.924 101.64 1.0985 120.835
66 kV 0.924 60.984 1.0985 72.501
33 kV 0.909 29.997 1.09 35.97
11 kV 0.909 9.999 1.09 11.99
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Perspective planning
process Planning process consists of
Preparation of data
Identification of load center andthe substation
Planning upstream network and
grid substation
Planning grid network
Staging study for intermediate
year
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Preparation of Data
Load forecasting
Load forecasting at macro levelwill be carried out by CEA
The micro level shall be carriedout by the utilities
In the absence of loadforecasting, historical demand &
load growth may be considered
The Initial network should beproperly represented
Id tifi ti f l d t
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Identification of load centerand the substation
Peak demand recorded in eachsubstation in a particular year is takenas base and to which load growth beapplied OR the results of the demand
forecast study be used The new substation location is
identified
Based on peak load of the existing
stations Based on Substation planning criteria
The loads of existing substations arere-distributed to the new substation
based on their location & distance
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Sub-transmission Network
Load flow study is conducted in
islanded mode with each grid
substation as a slack bus
Violation of any planning criteria
Network is strengthened
New grid substation is added to
form additional island
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Grid substation Network
The interconnected network tobe represented completely
Generation schedule for the
system peak conditions are
drawn
The load flow study is carriedout by scaling down the load to
match system peak demand
Grid substation Network
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Grid substation Network
The Load flow study is repeatedforDifferent combination of
generation schedule
With change in diversity factor indifferent areas for the samesystem peak like
Diversity factor 1 in north and
increased diversity in other areasto match the system peak
Combination of above
Grid substation Network
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Grid substation Network
The network should not be
overloaded and shall meet theplanning criteria in all the studies
The network should meet the security
guidelines (both steady state and
transient state) Ex:N-1 contingency
checking
Short circuit, Transient and Voltage
stability studies shall be carried out
If any of the criteria not met, the
network expanded with additional
line.
Staging study
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Staging study This is the study for ascertaining
the substation & network additionsfor the intermediate years
For example, if the horizon year is
2008, the staging studies in the
order of 2007,2006,2005,2004shall be carried out
This is done running DC load flow
to identify the substation to be
removed
AC load flow is run to check the
planning criteria
Staging study
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Staging study
In case criteria is not met, then oneor more substations removed is put
back
The study for ascertaining the grid
substation network is for the
System peak condition for that
year is repeated
The process is continued for other
year also
Conclusion
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Conclusion
The proposed approach is being
followed in KPTCL and the resultsare encouraging
The Horizon year selected for thestudy is 2007 (terminal year of 10th
plan) and 2012 (terminal year of11thplan)
The staging studies for the period2007 to 2012 is carried out in detail
The overall network design for theyear 2017 is carried out withoutstaging studies
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Conclusion
The KPTCL network is represented
upto 11kV bus and complete
southern region network (400 &220kV) with real power injection for
HVDC import
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Loss figures in KPTCL
0.001.00
2.00
3.00
4.00
5.00
6.007.00
8.00
Year
2002-03
Year
2003-04
Year
2004-05
Year
2005-06
Year
2006-07
Peak Power Losses
Tr. N.L Loss
33 kV
66 kV
110 kV
220 kV400 kV
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Loss figures in KPTCL
0.001.00
2.00
3.00
4.00
5.00
6.00
7.00
Year
2002-03
Year
2003-04
Year
2004-05
Year
2005-06
Year
2006-07
Energy Losses
Tr. N.L Loss
33 kV
66 kV
110 kV
220 kV400 kV
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Present planning process
The process is based on
The field report to overcome
the overloading and poor
voltage
Demand from local
consumers
Influence from various
quarters
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Present planning process..
Disadvantages
System improvement in
isolated pocketsDelay in execution
Improper upstream
network