PRACTICES ADOPTED IN NLDC & RLDCs
These are in addition to S.O.P
S. No.
Function
Frequency
control
management
SRLDC
High frequency
 Surrender by constituents at ISGS on meritorder basis, surrendering
LTA/MTOA in consultation with Trader/Generators
 Other than ISGS, suggesting constituents to backdown own generation
on merit order basis.
 In extreme case suggesting states to surrender and re-allocation to
other states as per frequency conditions and same is applicable to
RLDCs example URS power at IGSTPS at present.
 Kadamaprai, Srisailam Pump storage hydro units can be run into pump
mode, in consultation with SLDCs TNEB, AP.
1
Low frequency
 If any unit of Kadamaparai Pump storage is operating in pump mode
and if the concerned beneficiary is over drawing, SRLDC shall advise
the concerned SLDC for discontinuing the pump operation.
 Load shedding to be carryout by O/D constituents.
 Issuing messages like operational messages /frequency violation
messages including ACE correction.
 Revision of ISGS backdown schedule in case of large unit tripping in
contingency allowing with in two time blocks
Power flow
management
2
Power Flow which will critically load a circuit during probable N-1 outage
needs regulation in addition to deterioration of other grid parameters like
voltage etc.
 Based on line constients like Hiriyur-neelamanagala/Kolar-Hosur D/c
suggesting constituents Karantaka/TNEB/KSEB to maintain their
schedule/regulating generation and loads of drawl points.
 Modulation of HVDC power order in consultation with NLDC
 Generation Rescheduling
 In case of congestion in S1-S2 corridor, followinfg actions may be
taken, regulation of inform power, removal of Pump operation,
maximization of generation at kadamparai, Kundah complex,Mettur,
Load re- arrangements at Chennai area, regulation of NCTPS
generation
 In case of congestion actions may be taken as per procedure of
“Measures to relieve congestion in real time operation”
 5.3 .issuing of Congestion warning message ,
 5.4 curtailment transactions followed by ATC revision,
 5.5 Revision of ATC,
 5.6 Notice for application of congestion charge.
 Pre studied congested nodes like violation of Flow gates, S1-S2, KolarHosur D/C etc are closely monitored.
Contingency
handling
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3
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Voltage control
and reactive
power
management
4
Deviation
control
5
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Test charging in consultation with SLDC/CTU.
Necessary revision in schedule should be carried out.
Modulation of HVD C set points in coordination with RLDCs/NLDC
Regulation of Hydro/Thermal generation.
Example in case of tripping of Kolar-Hosur S/C actions taken in real
time: modulation of HVDC points/load shedding by TNEB,KSEB as well
as generation backdown of NCPTS/Vallur , No under drawl by S1
Constituents
Preparation of FIR report to aware grid situation in real time
In case of Block out/ islanding immediately informing to RLDCs/NLDC
heads and constituents regarding situation and actions to be taken.
Extending startup power to thermal generators , formation islands and
extending supply to essential services
Switching operation of bus reactors, line reactors.
Absorption of MVAr near High voltage areas as per capability curve.
Running of SSLM units in condenser mode of operation
After detailed study suggestion of tap changing of ICTs/GTs
Modulation of HVDC set points
Opening of Long and lightly loded lines
Switching operation of HVDC filter
Issuing Voltage control messages
All constituents ,ISGS and regional Entities has to maintain schedule.
Issuing of Alert ,Emergency, Compliance messages as follows.
Alert- If the deviation > 150 MW or 12 % schedule whichever is less for 5
minutes Emergency- If the deviation > 250 MW for 5 minutes or > 150 MW
for 10 minutes. Non complianceZero crossing –messages Alert, Emergency, Non compliances follows
If drawal is >schedule
Congestion
management
6
Defence
mechanism
7
Scheduling
8
Reporting
system
9
Monitoring of flow gates :Flow gate -I ( allowable limit≈ 850MW) 400kV KolarHosur D/C
Scenarios:
•
High drawl by S2 constituents
•
Injection from S1
S1-S2 Flow gate –II ( allowable limit≈ 2400 MW) lines under S1-S2 flowgate.
 NLR-SPDR
 NLR-ALM
 KLR-HSR-D/C
 SMN-HSR
 CTR-THVLM D/C
 NLR-THVLM D/C
 CTR- SPDR
 KLR-THVLM
 220 kV inter state lines(S1-S2)
In congestion of congestion constituents has to maintain schedule. Issuing of
congestion warring message As per congestion relieving procedure.
Regulation of infirm power from S1 to S2.
 Automatic and Under Frequency Load Shedding Scheme
 Special Protection schemes
 Power Demand Over (PDO) ride at Gazuwaka and Talcher
 Islanding schemes
 HVDC frequency controllers


Preparation of dispatch and drawal schedules.
Allocation of URS power on FCFS basisas per SR operating procedure.
Surrenders by beneficiaries on prorate basis up to technical minimum
of ISGS units.
 Revision of STOA transactions in case of UNIT outages of STOA
transactions.
 Curtailment of trasactions in case of Planned shutdowns or in case of
congestion followed by ATC revision.
Following reports prepared from Grid Management
 Power supply position report
 Unit outage report
 Transmission line outage report
 Frequency graph
 NPMC,NPSD reports
 Coal Shortage reports
 Schedule and Drawls report
 Regional graphs
 Loss of Generations report
 SCADA and Actual of drawls comparison
 9 0’clock Flash report
 Peak and off reports


Reservoir levels report
In case of disturbance Flash report
Report will be prepared based on data of SCADA and Constituents.
All the constituents will furnish the Generation, Interstate line flows data
after 00:00 hrs of each day through web based reporting system, Email, Fax,
or telephone for the preparation of Reports.
Operational
security
10
System
restoration
procedures
11
Shutdown &
outage
procedure
12
SCADA/PMU
displays
14
15
Data Exchange/
Communication
System/It Tools





All the constituents/ISGS/Regional entities have to maintain schedules.
All the grid parameters has to be maintained with in the IEGC limits.
All the protections, Defense mechanism to be in service always.
Availability of accurate real time data.
Study to be carried out for shut downs of elements and report to be
prepared.
 Proactive action during real time operation.

o Self starting facilities available in generators will be availed
transmission
o Start up power to be fed to thermal generators by making use of
available transmission networks.
o Avoid consumer plant damage
o Restore essential services
o Conducting Mock drill exercise
o
Procedure for Availing the Outage in Real Time
 Request for outages which are approved by OCC must be sent by the
owner of the transmission asset at least 3 days in advance to SRLDC by
10:00 hours.
 In case the owner is not availing the OCC approved outage, the same shall
be intimated to the SRLDC at least 3 days in advance.
 On the day of outage, the outage availing agency shall seek the code for
availing outage from SRLDC/NLDC (wherever applicable).
 All 400 kV D/C and 765 kV and above elements shut downs to be sent to
outage coordinators for clearances.
In XA 21 widely used picture for real time operation as follows:
SR regional Grid display, Schedule and drawl’s, All constituents Generation
display, regional UI, Constituents UI with frequency trend, drawling checking,
all 400 kV and above Substation SLDC, Mvar absorption of Generators display,
DDC.
In SR PMU workstation following displays widely used for system operation :
all the SR PMU locations frequency , Line flows, Voltages, currents, angles ,
sequence components, Phasor diagram, Modal analysis in real time
Real time Getting from felid RTUs, SASs through communication channels like
FO, microwave, Satellite.
NLDC
NERLDC
ERLDC
DC
SLDC
SRLDC
DC
SLDC
KARNATAKA
(AP)
A
WRLDC
C
NRLDC
SLDC
SLDC
SLDC
(TS)
(TAMILNADU
(of other
states)
DC
DC
DC
SubSLDC
SubSLDC
GUNADALA
CHINAKAMPALLY
By 10.00 hrs.
ISGSs shall advise SRLDC the Station-wise MW and MWh capabilities
By 1100 hrs.
SRLDC shall advise the States / Beneficiaries the Station wise MW &
MWh entitlements
SLDCs/ Beneficiaries shall communicate the Station-wise requisitions
and details of bilateral exchanges to SRLDC.
SRLDC shall convey the ex-power plant despatch schedule to each
ISGS and net drawal schedule to each State / Beneficiary. The details
of unrequisitioned surpluses shall also be intimated.
By 1500 hrs.
By 1700 hrs.
By 2200 hrs.
By 2300 hrs.
ISGSs / States / Beneficiaries shall inform the modifications, if any, for
incorporating in the final schedule
SRLDC shall issue the final despatch and drawal schedule