A A PRESENTATION PRESENTATION

ON ON DISRUPTION OF POWER DISRUPTION OF POWER

GENERATIONGENERATION DUE TO NATURAL DISASTERSDUE TO NATURAL DISASTERS – –

EXPERIENCE OFEXPERIENCE OF 6 X 250 MW NATHPA JHAKRI6 X 250 MW NATHPA JHAKRI

HYDRO POWER STATIONHYDRO POWER STATIONOFOF

SJVN LIMITEDSJVN LIMITED 1

1500 MW NATHPA JHAKRI POWER STATION IS THE LARGEST OPERATING ROR PROJECT ON RIVER SATLUJ IN HIMACHAL PRADESH AND IN COMMERCIAL OPERATION SINCE OCT-2003.

BRIEF INTRODUCTION OF NATHPA JAHKRI HYDRO POWER STATION

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BRIEF DESCRIPTION OF NATHPA JHAKRI PROJECT DIVERSION DAM

TYPE - CONCRETE GRAVITY HEIGHT- 62.5 M, LENGTH – 185.45 MDESIGN FLOOD – 5660 CUMECS

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LIVE STORAGE- 303 HAM (at EL 1495.5m) , AREA = 23.45 HA RESRVOIR LENGTH= 2.5 KM

LIVE STORAGE- 111 HAM (at EL 1485.0m), AREA= 14.22 HA

RESRVOIR LENGTH= 1.1 KM

BRIEF DESCRIPTION OF NATHPA JHAKRI PROJECT- NATHPA RESERVOIR

Crest level of Nathpa Dam has been raised from EL 1485.5 m Crest level of Nathpa Dam has been raised from EL 1485.5 m to EL 1492.5 m which is the final levelto EL 1492.5 m which is the final level

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NUMBER - FOUR NUMBER,

OPENING SIZE - 6.0 M X 5.25 M

BRIEF DESCRIPTION OF NATHPA JHAKRI PROJECT-CONTD. INTAKE STRUCTURE

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FOUR NUMBER UNDER GROUND EGG SHAPED, EACH 525 M LONG, 16.31 M WIDE & 27.5 M HIGH {One of the {One of the

largest Desilting Chambers in the World}largest Desilting Chambers in the World}

BRIEF DESCRIPTION OF NATHPA JHAKRI PROJECT-CONTD. DESILTING CHAMBERS

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CROSS SECTION - 10.15 M CIRCULAR, CONC. LINED LENGTH- 27.4 KM.

LOW COVER REACHES - STEEL LINED 8.5 M DIA NEAR MANGLAD & DAJ CREEKS

BRIEF DESCRIPTION OF NATHPA JHAKRI PROJECT-CONTD. HEAD RACE TUNNEL

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TYPE - RESTRICTED ORIFICE WITH POND AT TOP AND A LOWER EXPANSION GALLERY

HEIGHT - 301 MDIAMETER - 21.6 M FOR 210 M HEIGHT - 10.2 M FOR CONNECTING SHAFT 86 M

HIGH

BRIEF DESCRIPTION OF NATHPA JHAKRI PROJECT-CONTD. SURGE SHAFT

TYPE - RESTRICTED ORIFICE WITH POND AT TOP AND LOWER EXPANSION GALLERY

HEIGHT - 301 MDIAMETER - 21.6 M FOR 210 M HEIGHT - 10.2 M FOR CONNECTING SHAFT 86 M

HIGH

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BRIEF DESCRIPTION OF NATHPA JHAKRI PROJECT-CONTD. POWER HOUSE-MACHINE HALL

SIZE - 222 M (L) X 20 M (W) X 49 M (H)6 X 250 M.W VERTICAL AXIS FRANCIS TURBINE

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BRIEF DESCRIPTION OF NATHPA JHAKRI PROJECT-CONTD. TRANSFORMER HALL & SWITHGEAR

SIZE - 196 M X 17.5 M X 27.4 M EQUIPMENT HOUSEDGENERATOR TRANSFORMERS, 800 KV SWITCHGEAR & DRAFT TUBE GATES

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BRIEF DESCRIPTION OF NATHPA JHAKRI PROJECT-CONTD. LINE SWITHGEAR

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BRIEF DESCRIPTION OF NATHPA JHAKRI PROJECT-CONTD. TRT OUTFALL & TAIL RACE TUNNEL

TAIL RACE - 10.15 M DIA CIRCULAR, CONC. LINED TUNNEL, 982 M LONG

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• RIVER SATLUJ HAS A TOTAL CATCHEMNT OF 49,820 SQ. KM AT DAM SITE.

• AROUND ONE FOURTH CATCHMENT AREA IS IN INDIA AND REMAINING THREE FOURTH IS IN TIBET/CHINA.

• BECAUSE OF FRAGILE GEOLOGY AND STEEP SLOPES, SOIL EROSION RATE IS HIGH DURING SNOWMELT.

• RIVER BLOCKADE ON ACCOUNT OF AVALANCES AND LANDSLIDES ARE COMMON BECAUSE OF STEEP BANKS

CATCHMENT AREA CHARACTERSTICS

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WHEN THESE BLOCKADES GIVE WAY FLASH FLOODS ARE CAUSED AND SILT CONCENTRATION INCREASES BECAUSE OF INCREASED EROSIONS OF THE BANKS.

RIVER SATLUJ ORIGINATES IN TIBET AND ENTERS THE INDIAN TERRITORY AFTER TRAVELLING ABOUT 300 KMS IN TIBET. RIVER SPITI JOINS IT AT KHAB IN INDIA.

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CATCHMENT AREA OF SATLUJ BASIN

KHAB

SUMDO

INDO-TIBETAN BORDER

SPITI RIVER

SATLUJ RIVERNATHPA JHAKRI POWER STATION

MANSAROVER

BHAKRA DAM

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FLOOD WARNING

DURING JULY 2004, FLOOD WARNING WAS ISSUED BY ARMY AUTHORITIES ON ACCOUNT OF ARTIFICIAL LAKE FORMATION DUE TO GLACIERS/ LANDSLIDES IN SPITI/ SATLUJ BASIN.

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MEASURES ADOPTED

TO SAFEGUARD THE PROJECT ON ACCOUNT

OF ABOVE FLOOD WARNING

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SJVN CONTACTED VARIOUS EXPERTS IN THE FIELD:

NRSA, HYDERABAD WAS REQUESTED TO LOCATE THE EXACT POSITION OF THE ARTIFICIAL LAKE THROUGH SATELLITE IMAGERIES. THE INCREASE IN THE SIZE OF THE LAKE WAS CONTINUOUSLY MONITORED THROUGH NRSA.

COMPUTATIONS & PROBABILIY OF BURSTING WERE ALSO REQUESTED FROM SURVEY OF INDIA, DEHRADOON, BASED ON PAST EXPERIENCES OF SIMILAR BLOCKADES IN ALAKNANDA RIVER.

THE DEPTH OF THE LAKE WAS ESTIMATED AND IT WAS ALSO ESTIMATED AT WHAT LEVEL THE WATER WOULD RISE AT VARIOUS LOCATIONS IN THE RIVER UNDER WORST CONDITIONS. THE TIME TAKEN BY WATER TO REACH DAM SITE AT NATHPA AND POWER HOUSE SITE AT JHAKRI WAS ALSO ESTIMATED FROM ADVANCE WARNING STATIONS AT KHAB AND SUMDO.

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CONTINGENT PREPAREDNESS TO COPE WITH SUDDEN LAKE BURSTING

Project authorities instructed all concerned living within 100 feet above the river level to shift to safe heights.

Adequate food supplies were stored in Project area.

The communication system was kept upgraded and maintained in proper working condition.

In front of the Power House MAT, on the valley side, a masonry wall was constructed up to a height of 4 m to prevent water from entering into the Power House.

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Mock Drill was conducted regarding the steps to be

taken in the event of warning regarding flood. Based on the mock drill, it was established that the maximum time required for complete shutdown of the Power Station was two hours and twenty minutes considering that each Unit will take ten minutes to fully close it. In unison with it, the SFT Gates and Intake gates were to be closed. All five Radial Gates were to be fully opened and dogged.

24 hrs advance Advance warning systems were established at Sumdo and Khab. The stations were equipped with manpower, wireless sets and telephones including satellite phones.

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Portable DG sets were provided at both the Stations for standby power round the clock.

SJVN advised higher officials to visit different sites regularly to monitor the system working.

Liasioning was done with Army establishment. A communication channel was established with the Army officials, ITBP officials and District administration.

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ON 26.06.2005, SUDDEN INCREASE IN THE FLOW OF PARCHEU WAS NOTICED BY ITBP DEPLOYED ON THE INDIAN BORDER.

IMMEDIATELY A FLOOD ALERT WAS ISSUED BY STATE ADMINISTRATION.

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AT DAM SITE, NATHPA All SFT Gates were closed.

SFT Outfall Gate was closed.All Intake Gates were closed in close association with stopping of all machine at Jhakri.

All Radial Gates were fully opened and dogged.

The reservoir was depleted to free flow conditions with water level at 1465 m.

The Gantry Crane for stop logs was locked on left bank extreme.

Adit 2 Gate for Desilting Complex was closed.SJVN manpower was put on high alert and moved from vulnerable areas.

Video and still photography was planned to be done from safe distance for reference and R&D purpose.

IMMIDIATE STEPS TAKEN

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AT POWER HOUSE SITE, JHAKRI

All TRT Gates were closed.

Closing action on Draft tube Gates was taken up immediately in view of the fact that at least two hours are required for closing of each Draft Tube gate.

Head count of manpower deployed in Power House complex was done. All Shift staff including CISF personnel were shifted to GIS-I floor at EL 1053 m after information regarding flood water having reached Nathpa was received.

Escape route through cable tunnel to Pot Head Yard at EL 1173 m was planned for any exigency.

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All Dewatering and Drainage pumps were put on auto mode

of operation.

Entry to Power House was banned after information regarding flood water having crossed Nathpa was received.

It was decided to monitor the water level at TRT Outfall from a safe place for complete flood cycle.

Video and still photography was planned to be done from safe distance for reference and R&D purpose.

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OBSERVATIONS FLOODING INCIDENT ON 26.06.2005.

The first information about the rise in water level of river Pracheu to the order of 40 to 50 feets was received in Power House at 1000 hrs.

The information that water had crossed Sumdo was received at 1030 hrs. The increase in the water level was reported to be around 60 to 70 feet at Sumdo.

The water reached Nathpa Dam site at about 1540 hrs and the level in the Nathpa reservoir increased from 1465 to 1482 m. 27

The flood water reached Jhakri at about 1645 hrs and the river level at TRT Outfall increased from 1009 m to 1020.5 m.

The silt content in the river at TRT Outfall as per sample taken at 1820 hrs was of the order of 1,51,000 ppm.

Subsequent to the flood, the water level in the reservoir and the TRT outfall area started receding. The water level was observed as 1464 m at Nathpa Dam and 1009.7 m at TRT outfall on 27.06.2005.

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AFTERMATHS OF THE FLOOD

The monitoring of the flood was continued even after the flood had crossed the Project area.

The water level and silt measurements were continued. It was observed that the peak volume of water passed was of the order of 47 lac cumecs and total volume of flood water passed was of the order of 467 lac cumecs.

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Thus, it will be noted that on account of the effective Disaster Management Plan which was in place and the timely action taken by NJHPS Management,

There was no human loss in the Project area because of above incident.

There was no damage to any of the major components of the Project.

The unprecedented silt load was not allowed to enter into the water conductor system of the Project.

The generation which was suspended on account of above incident was restored as soon as the silt level reached within permissible limit.

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FOR FIRE INCIDENTS

Fire Fighting system- Fire hydrant system. Fire detection and alarm enunciation system.

Emulsifier system for transformer hall.

Portable fire extinguishers.

CO2 Systems for generators.

Fire Tenders.

A special fire wing of CISF equipped with latest state of art fire fighting equipments for Power House and outside area.

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