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POWER GRID CORPORATION
OF INDIA LTD.
SRLDC,BANGALORE
EXCERPTS FROM CERC ORDER
DATED 26.06.2002
“In the interest of security and safety of the
regional grid, we, therefore, feel that some parts
of the States indulging in overdrawals have to be
isolated/islanded and supplied from the State's
own resources at whatever frequency they want
to operate at the risk of their own machinery &
equipment; but not through the Inter-State
Transmission System or Inter-State Generation
System.”
EXCERPTS FROM CERC ORDER
DATED 26.06.2002
“We, therefore, consider that a Committee
……… may go into the technical and
commercial aspects of isolating/islanding
some parts of the system, without
damage to the Regional grid, in detail .”
VIEW THE
ORDER
SECTION 55
ELECTRICITY (SUPPLY) ACT, 1948
AMENDED 1998
2)
The Regional Load Despatch Centre shall give
the apex body to ensure integrated operation of the
power system in the concerned region.
3)
The Regional Load Despatch Centre may give
such directions and exercise such supervision and
control as may be required for ensuring integrated
grid operation and for achieving the maximum
economy and efficiency in the operation of the power
system in that state
IEGC-Chapter - 3 Clause - 3.5
(i)
As a general rule, the ISTS shall be capable
of withstanding and be secured against the following
contingency outages without necessitating load
shedding or rescheduling of generation during
Steady State Operation : Outage of a 132 kV D/C line or
 Outage of a 220 kV D/C line or,
 - Outage of a 400 kV S/C line or,
 - Outage of single Interconnecting Transformer, or
 - Outage of one pole of HVDC Bipole line, or
 - Outage of 765 kV S/C line.

IEGC-Chapter - 6 Clause - 6.2
System Security Aspects:
a ) All Regional constituents shall endeavor to
operate their respective power systems and
Power Stations in synchronism with each
other at all times, such that the entire system
within a Region operates as one synchronised
system.
IEGC-Chapter - 6 Clause - 6.2
System Security Aspects:
b) No part of the grid shall be deliberately isolated from the rest of the
Regional Grid, except
(I) under an emergency, and conditions in which such isolation would
prevent a total grid collapse and/or enable early restoration of power
supply
(II) when serious damage to a costly equipment is imminent and such
isolation would prevent it
(III) when such isolation is specifically instructed by RLDC. Complete
synchronisation of grid shall be restored as soon as the conditions again
permit it. The restoration process shall be supervised by RLDC, as per
operating procedures separately formulated.
IEGC Chapter - 6 Clause - 6.2
C ) No important element of the Regional grid shall be
deliberately opened or removed from service at any time, except
when specifically instructed by RLDC or with specific and prior
clearance of RLDC. The list of such important grid elements on
which the above stipulations apply shall be prepared by the
RLDC in consultation with the constituents, and be available at
RLDC/SLDCs. In case of opening/ removal of any important
element of the grid under an emergency situation, the same shall
be communicated to RLDC at the earliest possible time after the
event.
EXCERPTS FROM MANUAL ON
TRANSMISSION PLANNING
CRITERIA - CEA


2. PLANNING PHILOSOPHY &
GENERAL GUIDELINES
2.1 The transmission system shall be
planned on the basis of regional selfsufficiency with an ultimate objective of
evolving a National Power Grid.
GENERAL ISSUES

MODUS OPERANDI
INITIATION OF THE SCHEME AND
NORMALISATION
YARDSTICK FOR INITIATING
ISOLATION/ISLANDING
 HOW LONG SHOULD SUCH ISOLATION LAST?
 SYSTEM CONSTRAINTS?
 WHO DECIDES?

GENERAL ISSUES CONTD…..

MODUS OPERANDI
LOAD CONTROL /SWITCHING TO BE DONE
BY STATE SYSTEM – LOGISTICS?
WHO DECIDES WHAT LOADS ARE TO BE
ADDED/REMOVED?
 VARIATIONS OF LOAD INVOLVES MANY
SWITCHING OPERATIONS – WHO WILL COORDINATE THE SAME?
 INNUMERABLE HYPOTHETICAL COMBINATIONS
POSSIBLE FOR ISLANDING

GENERAL ISSUES CONTD….

MODUS OPERANDI
CONCURRENT APPLICABILITY TO OTHERS
SYSTEMS?
IN CASE OF OVERDRAWALS BY TWO OR THREE
CONSTITUENTS AT LOW FREQUENCY-WOULD THE
SCHEME BE APPLIED SIMULTANEOUSLY?
 THIS WOULD REQUIRE CO-ORDINATION OF
MANY SWITCHING OPERATIONS.

ISOLATION OF GRID
ISSUES INVOLVED





OPERATION ISSUES
SCHEDULING ISSUES
PROTECTION ISSUES
COMMERCIAL ISSUES
STABILITY ISSUES



SHORT CIRCUIT LEVELS
L-INDEX – VOLTAGE STABILITY
ANGULAR STABILITY
REPORT OF HIGH COURT
APPOINTED COMMITTEE
OPERATIONAL ISSUES
A PART OF LOAD(400-3000MW SAY)
ISOLATED.


STABILITY ISSUES
LOWER SHORT CIRCUIT LEVELS IN BOTH
PARTS LEADING TO VOLTAGE EXCURSIONS
LOWER INERTIA - LEADING TO FREQUENCY
EXCURSIONS
47.7 HZ

51.5 HZ

.............CONTD
OPERATIONAL ISSUES

OPERATIONAL FLEXIBILITY LOST








DIVERSITY WILL REMAIN UNUTILISED
TRANSITION BETWEEN PEAK AND OFF-PEAK DIFFICULT TO MANAGE
LINE LOADINGS – A PROBLEM DURING LOAD
CHANGE OVER IN AP – HYDRO FLEXIBILITY
UNAVAILABLE
FREQUENCY RISE DIFFICULT TO CONTAIN IN BOTH
BLOCKS
PREDOMINANT THERMAL – LOWER INERTIA
Df/dt WILL BE SHARP
VOLTAGE AND FREQUENCY EXCURSIONS –EXTREME
COMPLEXITY INVOLVED IN SWITCHING
PROTECTION ISSUES
 DRASTIC
REDUCTION IN SC
LEVELS- OCR SETTINGS?
 FREQUENCY AND VOLTAGE
EXCURSIONS- v/f SETTINGS?
 LOAD ENCROACHMENT PROBLEMS
– LOW VOLTAGE - LOADING
 POWER SWING
ISSUES TO BE EXAMINED FOR ISOLATION

SCHEDULING PROBLEMS




CONTRACTION/EXPANSION OF ISLAND TO
BE DONE WITH CHANGING SCHEDULES
COMPLEXITY INVOLVED IN SWITCHING
FORCED OVERDRAWALS – A QUANDRARY
THAT MAY BE UNAVOIDABLE
STATE SYSTEM – INABILITY TO DRAW
ENTITLEMENT
LOAD MANAGEMENT/SWITCHING
OPERATION – STILL IN STATE PURVIEW
ISSUES TO BE EXAMINED FOR ISOLATION
CONTD....

SCHEDULING PROBLEMS
DRAWAL PATTERN VARIATION –:(MIN/MAX IN %)
STATE SYSTEM
MIN/MAX IN %
3D LOAD
ANDHRAPRADESH
75-85%
PROFILE
KARNATAKA
KERALA
TAMILNADU
55-65%
55-60%
80-85%


CONTRACTION AND EXPANSION OF ISLAND
COMMERCIAL IMPLICATION- OD/UD
COMMERCIAL ISSUES

INABILITY TO DRAW AS PER
ENTITLEMENT DUE TO INSUFFICIENT
LOAD IN ISGS/ISTS BLOCK :

STATE MAY BE FORCED TO UNDERDRAW
FROM ISGS AND FORCED TO GENERATE AT
COSTLY IPP’S/DEPLETED HYDRO –
COMMERCIAL IMPLICATION?.
OVERDRAWAL MAY CONTINUE FORCING
OTHER CONSTITUENTS TO COMMIT
COSTLY GENERATION
SHORT CIRCUIT LEVELS –
RELEVANCE TO GRID OPERATION




SC LEVELS ARE AN INDICATOR OF THE
‘STRENGTH’ OF THE BUS TO REACTIVE
POWER FLUCTUATIONS
HIGHER SC LEVELS – BUS IS MORE
STABLE – LIMITS VOLTAGE EXCURSIONS
HIGHER SC LEVELS- BUS IS WELL
INTERCONNECTED-PROXIMITY OF
GENERATORS
ESPECIALLY IMPORTANT DURING
RESTORATION.
SHORT CIRCUIT LEVELS –
RELEVANCE TO GRID OPERATION

AN EXAMPLE:

CHARGING A 300 KM LINE FROM A 2000 MVA
400 KV BUS WOULD INCREASE THE VOLTAGE
BY 33 KV
CHARGING A 300 KM LINE FROM A 6000 MVA
400 KV BUS WOULD INCREASE THE VOLTAGE
BY 11 KV
SHRT CKT STUDY
RESULT
L INDEX





INDICATES THE PROXIMITY TO VOLTAGE
COLLAPSE
IF THE INDEX APPROACHES 1 THEN THE BUS
IS INCREASINGLY VULNERABLE TO VOLTAGE
COLLAPSE
DERIVED FROM LOAD FLOW JACOBIAN MATRIX
SHOULD BE GENERALLY WITHIN 0.3 DURING
NORMAL OPERATION FOR SR GRID.
GENERALLY IN LINE WITH WHAT IS OBSERVED
BY THE SYSTEM OPERATORS
L INDEX STUDY
400 KV SUMMARY
L INDEX STUDY
RESULT
L INDEX
GOOTY
0.3126
AP
CUDDAPAH
0.268
AP
HYDERABAD
0.236
AP
KHAMMAN
0.1794
AP
NUNNA
0.1693
AP
RAMAGUNDAM
0.1197
AP
SIMHADRI
0.1177
AP
BANGALORE
0.3431
KAR
HOODY
0.3175
KAR
NELAMANGALA
0.3101
KAR
KOLAR
0.3043
KAR
DAVANGERE
0.2157
KAR
MUNIRABAD
0.1721
KAR
RAICHUR
0.0804
KAR
TRICHUR
0.2262
KER
HOSUR
0.2539
TN
SALEM
0.2011
TN
SCIENTIFIC
SETTLEMENT
SYSTEM?
ISGS
LINKS
SR GRID MAP
KAR ISL CASE3
TN ISL CASE1
AP GRID MAP
KARNATAKA
GRID MAP
KERALA
GRID MAP
TN GRID MAP
SHORT CKT STDY
RESULTS 400 KV
L INDEX STUDY
RESULTS
3D DEMAND SR
JUNE 2002
3D DEMAND SR
MAY2002
3D DEMAND SR
MARCH 2002
SHORT CKT STDY
RESULTS 220 KV
SHORT CKT STDY
RESULTS 230 KV
ISOLATION OF PART OF
KARNATAKA: CASE STUDY



GRID
CASE 1: SOMANAHALLY TRANSFORMER
CONNECTED TO AP-TN-KER GRID AND
MAP
RADIALLY FEEDING 700MW LOAD, KAIGA
EMBEDDED IN KARNATAKA SYSTEM.400 KV
RTPS-N’SAGAR OPEN
CASE 2: CASE 1 WITH KAIGA ISLANDED
CASE 3: SPLIT BUS AT RTPS, KAIGA & 400KV
UNITS OF RAICHUR WITH AP-KER-TN-KOLARSOMANAHALLI-HOODY-GUTTUR SYSTEM.
SOMANAHALLY AND HOODY RADIALLY FEEDING
BANGALORE LOADS EXCEPT PEENYA.
CASE 1 BANGALORE LOADS ON
AP-TN-KER GRID
LOAD 3000
MW
LOW
VOLTAGE
ZONE
ABOUT 700
MW ON APTN-KER GRID
KARNATAKA-SC LEVELS IN MVA
ISLANDING IN KARNATAKA SYSTEM
KARNATAKA
STN_NAME
STATE
BASE CASE
CASE1
CASE2
CASE3
RST4
AP
8760
8378
8371
8194
TPL4
AP
6768
5926
5916
5697
CNP4
AP
5055
4782
4776
4747
GTN4
AP
2936
3027
3018
2789
KOLAR4
KAR
6479
5362
5358
5868
RTPS4
KAR
5859
3962
3692
3149
SOMN4
KAR
5540
4394
4390
4850
HOODY4
KAR
5536
1522
1305
4911
NLMNG4
KAR
4818
1656
1423
3979
DVGRE4
KAR
4349
2545
2120
2890
GDHL4
KAR
3767
2777
2546
2330
ISOLATION OF PART OF KERALA
AND TAMILNADU: CASE STUDY


TAMILNADU : TTPS, BALAJI POWER,WIND,
NILAGIRIS HYDRO, KADAMPARAI HYDRO
IN ISOLATED PORTION. AP-KAR-KER AND
N.TAMILNADU(NEYVELI-MAPS-ETS-NMTPSMTPS – GMR) IN ONE BLOCK
KERALA- SPLIT BUS AT EDAMON AND
THRISSUR WITH LOADS TAKEN RADIALLY
AT BOTH POINTS
TAMILNADU AND KERALA SC LEVELS IN MVA
KERALA
TN
CASE1
STN_NAME
STATE
BASE CASE
CASE1
RST4
AP
8760
8740
8725
CNP4
AP
5055
5014
4987
SOMN4
KAR
5540
5441
5312
KOLAR4
KAR
6479
6537
6526
TRICH4
KER
3838
2724
3239
N2MIN4
TN
10556
10128
9828
NLYEU4
TN
10223
9818
9537
SALEM4
TN
8119
7639
6523
SPBUDUR4
TN
7011
6923
6895
TRICHY4
TN
6661
6266
5654
MADURAI4
TN
5755
5251
4094
HOSUR4
TN
5474
5346
5277
UDMLPT4
TN
5433
4363
4032
OPERATIONAL ISSUES
KARNATAKA

KAIGA REMAINS EMBEDDED IN ISOLATED
PORTION OF KARNATAKA



FREQUENT HOUSE LOADING AND POISONING OUT EXPECTED.
KAPS TO REDUCE GENERATION BY 40-50 MW TO
PREVENT HUNTING
DEPLETED HYDRO POSITION IN ISOLATED
PART:



PEAKING HYDRO TO BE RUN AS BASE STATION
STORAGE POSITION ALREADY CRITICAL
EXTREMELY LOW VOLTAGES TO BE EXPECTED IN
SOUTH KARNATAKA.
DELIVERING CGS ENTITLEMENT TO
KARNATAKA





KPTCL’S CGS ENTITLEMENT WITH FULL
GENERATION AT NTPC,NLY,KAPS AND ONE
UNIT AT MAPS IS AND WITH ALLOCATION OF
156 MW ER AND 100 MW PTC POWER = 1206
MW
GOA’S ENTITLEMENT TO BE WHEELED BY
KPTCL = 94 MW.
TOTAL ENTITLEMENT OF KPTCL = 1310 MW
AS KAIGA GENERATION OF 400 MW IS
EMBEDDED KPTCL HAS TO IMPORT 910 MW
AT 330 KV/400 MVAR IMPORT THE
CAPACITY OF SOMANAHALLI TRANSFORMER
IS 720 MW
DELIVERING CGS ENTITLEMENT TO
KARNATAKA







KPTCL’S CGS ENTITLEMENT WITH FULL GENERATION
AT NTPC,NLY, ONE UNIT AT KAPS AND MAPS IS AND
WITH ALLOCATION OF 156 MW ER AND 100 MW PTC
POWER = 1140 MW
GOA’S ENTITLEMENT TO BE WHEELED BY KPTCL = 94
MW.
TOTAL ENTITLEMENT OF KPTCL = 1234 MW
AS KAIGA GENERATION OF 200 MW IS EMBEDDED
KPTCL HAS TO IMPORT 1034 MW
AT 330 KV/400 MVAR IMPORT THE CAPACITY OF
SOMANAHALLI TRANSFORMER IS 720 MW
DIFFICULTY IN DELIVERING ENTITLEMENT
LOADS AT SOMANAHALLI TO BE REARRANGED
DEPENDING ON KAPS GENERATION