Restoration Procedure for West Region
In case of total blackout in Western region, assistance could be availed from neighbouring regions in addition to utilising black start facilities within the region. The various possibilities of availing start up power from outside sources are described below:
9.2.1 Scenario #1: From NR
Through 400kV HVDC bypass at Vindhyachal Back-to-Back Station and/or through 132kV Vindhyachal-Rihand and 132kV Vindhyachal-Singrauli lines
In case of tripping of all the units at VSTPS and tripping of both Vindhyachal-Jabalpur D/C and Korba-Vindhyachal lines, supply of start up power from Western region to VSTPS would be difficult as charging of 400kV lines may not be possible. The requirement of start-up power of VSTPS is approximately 35 MW for starting station auxiliaries and reviving one unit of 210 MW. The requirement for startup for 500 MW unit is 50 MW. This assistance could be availed through 400kV HVDC bypass or 132kV Vindhyachal-Singrauli-Rihand lines in case of non availability of 400kV HVDC bypass. VSTPS would make use of 35 MW to provide survival power for all the units at VSTPS and starting of one unit. Once one unit at VSTPS starts generating, other units can be started. If power is available, revival of multiple units can be attempted depending on the available quantum of power. Depending upon the voltage levels and availability of machines, 400kV lines from VSTPS can be charged to evacuated the generation from VSTPS with at least two units synchronized at VSTPS and closing of Vindhyachal-Jabalpur line should then be attempted.
UTILISATION OF AC BY-PASS LINKS
Inter-regional tie points especially strong inter-connections enable import of substantial amount of power which can be used to provide start-up power to several power plants in the shortest possible time. Based on the quantum of assistance, power supply to some essential loads could also be restored. Other advantage over black start facilities would be stable operation of the restored part since the same would be connected strong healthy external system. Two such major options are through bypass AC links at HVDC back to back stations at Vindhyachal & Bhadravati. The start up power could be availed within 30 minutes. Further, experience of restoration from these tie points has been highly encouraging. The core approach has been followed rather than island approach. The operational procedures for closing and opening of bypass links are discussed in ensuing paragraphs.
of A.C. Bypass link
the event of a total blackout in the Western Region, start up power would be
obtained from the Northern Region on Vindhyachal A.C bypass link.
per the existing arrangement with Northern Region, Western Region can draw 200
MW power from Northern Region (100MW for VSTPS and 100MW for KSTPS) on this link
consequent to a total blackout. The
quantum of power can be increased subsequently on mutual consent.
this link connects the two regions using line isolators only, due care is to be
taken before its operation while connecting or disconnecting the two regions.
The schematic diagram depicting the set up of 400kV Vindhyachal A.C
bypass link is shown at Exhibit-I. The
sequence of operation of this link is as follows:-
back-to-back shall initiate action to extend start up power to VSTPS through
the A.C. bypass link as soon as it receives a request from VSTPS.
However, the A.C bypass link shall be closed
after receiving confirmation from either of RLDCs.
VSTPS shall open breakers AWL2-Q and AWL1-Q and confirm the
same to HVDC Vindhyachal.
Vindhyachal shall isolate HVDC Block-I and Block 2 by opening breakers Nos.
BIQ11-Q, BIQ21-Q, B211-Q and B2Q21-Q.
Vindhyachal shall open breaker ARI-Q of reactor if it is connected to HVDC
Bus I B.
Vindhyachal shall ensure that North
Vindhyachal shall bypass interlocking scheme of D11 & D21 isolators of
Vindhyachal shall close D21 isolator of bypass link.
D11 isolator manually.
Vindhyachal shall intimate VSTPS to draw start up power by one of the HVDC
feeders to bus 1B.
case of any problem in opening of VSTPS end breakers of HVDC-VSTPS feeders,
VSTPS shall request HVDC to open AWL3Q.
This procedure shall be followed only under exceptional conditions.
Breaker AWL3-Q shall be opened by HVDC station after getting
clearance from NRLDC. After
opening AWL3Q, HVDC station shall close isolators D21 followed by D11
(manually after bypassing interlock). Close
AWL3Q thus charging North bus 1A and West Bus 1B.
Then VSTPS shall be asked to take one feeder on West bus 1B and draw 100 MW start up power.
shall extend startup power to KSTPS by charging 400kV Vindhyachal-Korba S/C
of bypass link
the VSTPS-KSTPS part system of WR connected to NR grid is running with the
synchronization of two generating units ( with one
preferably 500 MW set) in KSTPS/VSTPS, it shall be disconnected from N.R by
disconnecting bypass links. Active
power flow on the bypass link should be brought to floating condition to the
extent possible before opening. Reactive
power import from N.R should also be reduced to bare minimum (by increasing MVAR
generation on KSTPS/VSTPS units) before disconnecting the bypass link.
For making the line floating, generation of KSTPS/VSTPS shall be
modulated and if required Vaidhan loads can be connected on VSTPS.
In case N.R is drawing power on the bypass link from WR, WRLDC shall take
the help of NRLDC for controlling flow on the bypass link alongwith generation
reduction on KSTPS/VSTPS units.
Vindhyachal shall obtain permission from NRLDC and WRLDC for disconnection
by opening breaker AWL3Q.
station shall open isolator D21 followed by D11.
station shall close AWL3Q.
island after separation from N.R shall be quickly connected to the rest of the
132kV Gandhisagar-R.P.Sagar line
220kV Ujjain-Kota D/C
9.2.2 Scenario #2 : From S.R
a) Through 400kV HVDC bypass Chandrapur-Ramagundam line
The detailed procedures for using AC bypass at Bhadravati HVDC Back-to-back station are available with HVDC Bhadravati Station.
b) Through 220kV Kolhapur-Chikodi D.C
The detailed procedures to be followed for the other modes listed above have been explained under restoration schemes for various constituents in detail under Chapters 4 to 8
9.2.3 Scenario # 3: From ER
a) Through 220kV Budhipadar-Korba (E) T/C lines. The detailed procedure is described under Section 6.3.
b) Through 400kV Rourkela-Raipur D/C lines. The detailed procedures are described under Section 6.3.