Pre-com­mis­sion­ing test­ing of 720MW Mangdechhu Hy­dro­elec­tric Project

Bhutan Times - - Front Page - Sonam Pen­jor

The 720MW Mangdechhu Hy­dro­elec­tric Project Au­thor­ity (MHPA) will start to pre-com­mis­sion­ing test­ing units I, II, III and IV and also the test­ing of aux­il­iary equip­ment in the un­der­ground power house in Oc­to­ber this year.

The above re­ferred test­ing shall be car­ried out by slowly fill­ing the pres­sure shafts by wa­ter from iden­ti­fied ex­ter­nal source.

The test­ing will en­sure the per­fec­tion of the unit align­ment and also the re­sponse of the aux­il­iary equip­ment in the power house.

The di­ver­sion tun­nel and head race tun­nel (HRT) of Mangdechhu Project would be plugged by end of Oc­to­ber 2018.

Ac­cord­ing to the sta­tus re­port as of June 30th 2018 of MHPA, the over­all phys­i­cal progress of C-1 pack­age as on 30th June 2018 is 99.81 per­cent with an av­er­age progress of 0.25 per­cent per month dur­ing the sec­ond quar­ter of 2018.

The re­port states that the con­struc­tion of 114 meters (m) high con­crete grav­ity dam has been com­pleted. The to­tal con­crete quan­tity 4, 83,140 Cum has been done dur­ing the sec­ond quar­ter of 2018. “All ma­jor works in dam com­plex in­clud­ing un­der­ground works have now been com­pleted and clean­ing works are in progress.”

The plug­ging of the di­ver­sion tun­nel is planned from 15th Septem­ber 2018 on­wards when dis­charge in the Mangdechhu river will be man­age­able, states the re­port.

The re­port fur­ther stated that the var­i­ous in­stru­ments in­stalled in the dam body and its ap­pur­tenant struc­tures showed de­for­ma­tion in the early stage of in­stal­la­tion. How­ever, de­for­ma­tions ob­served are in­signif­i­cant dur­ing the quar­ter. All the in­stru­ments are func­tion­ing prop­erly.

The con­tact and con­sol­i­da­tion grout­ing works of the HRT was also be­ing done in par­al­lel so that plug­ging of the tun­nel is achieved, soon af­ter com­ple­tion of overt and in­verts lin­ing. Out of 13,505.19m of pro­posed con­tact grout­ing in HRT, 5,617.7m has been com­pleted. About 2,902m has been done in this quar­ter of which 78m, 1,174m, 286m, 250m and 1,114m has been done, stated the re­port.

About 1,208m of con­sol­i­da­tion grout­ing has been com­pleted in this quar­ter of which 28m, 129m and 1,051m has been done in face-2, face3 and face-9 re­spec­tively.

The bal­ance works for HRT in­clud­ing plug­ging of tun­nel shall be com­pleted by Septem­ber or Oc­to­ber next month, stated the re­port.

The re­port also stated

that ma­jor civil works of the un­der­ground power house have been com­pleted. The con­crete lin­ing of Tail Race Tun­nel (TRT) and surge shaft have also been com­pleted. Clean­ing or fin­ish­ing works of the un­der­ground power house in­clud­ing con­trol room is un­der progress. Mon­i­tor­ing of un­der­ground power house and trans­former hall cav­erns Geotech­ni­cal in­stru­ments in­stalled in the cav­erns were mon­i­tored reg­u­larly. As such no sig­nif­i­cant de­for­ma­tion is ob­served in this quar­ter.

Sta­tus of elec­tro-me­chan­i­cal, trans­mis­sion line and its works, the re­port states that out of four units 180 MW each, unit-1, 2 & 3 have been boxed up. The unit-4 is ex­pected to be boxed up in this month. All four MIVs have also been in­stalled. The erec­tion of one But­ter­fly Valve in BVC has been com­pleted and the erec­tion of sec­ond But­ter­fly Valve is near­ing com­ple­tion. Lay­ing of All Di­elec­tric Self Sup­port­ing (ADSS) ca­bles started from June month.

And in­stal­la­tion of Unit Tap-off Trans­former (UTT) for unit 1 & 2 has been com­pleted and in­stal­la­tion for unit 3 & 4 is in progress. In­stal­la­tion of Unit Aux­il­iary Board (UAB) is com­pleted and in­stal­la­tion Sta­tion Aux­il­iary Board (SAB) in con­trol room is in progress. The in­stal­la­tion works of 33/11kV switchgear is un­der progress. Fin­ish­ing works of the con­trol room is in ad­vance stage and the con­trol room shall be ready in all re­spect by Septem­ber 2018.

The works for EM-2 pack­age has been com­pleted in all re­spect. Elec­tro-Me­chan­i­cal pack­age EM-3 (420 kV GIS) by Hyosung Cor­po­ra­tion. The works for EM-3 Pack­age has been com­pleted in all re­spect. The HV Test of 420 kV GIS com­pleted on the month of May this year. Erec­tion of Light­ning Ar­resters (LAs) has been com­pleted and vac­u­um­ing and gas fill­ing is in progress.

Elec­tro-Me­chan­i­cal pack­age EM-4 (400 kV XLPE Ca­bles), the re­port states that the works for EM-4 pack­age has been com­pleted in all re­spect. Cable ter­mi­na­tion works com­pleted at pot­head yard end and is un­der progress at GIS end. The four num­bers of 67 MVA ICT trans­form­ers have been placed in the ICT Build­ing.

The con­struc­tion of trans­mis­sion lines within the Bhutan por­tion from the Mangdechhu Pot­head Yard to Jig­melling sub­sta­tion has been com­pleted. The line was test charged on 23rd June 2018 from Jig­melling sub­sta­tion to the Mangdechhu Pot­head Yard.

The trans­mis­sion line works in West Ben­gal por­tion is pro­gress­ing smoothly and the line shall be com­mis­sioned match­ing the com­mis­sion­ing sched­ule of the Mangdechhu Project. How­ever the re­port states that the trans­mis­sion line in As­sam por­tion has been de­layed due to de­layed wildlife clear­ance from As­sam Govern­ment for about 47kms stretch near Indo-Bhutan bor­der in As­sam. “The Govern­ment of As­sam has re­cently granted the Wildlife Board Clear­ance and now the fi­nal clear­ance is un­der process in the Min­istry of En­vi­ron­ment, For­est and Cli­mate Change, Govern­ment of In­dia (GoI).”

Re­port fur­ther states that the de­lay in com­ple­tion of As­sam por­tion of the trans­mis­sion line, will not pose prob­lem for evac­u­a­tion of power from Mangdechhu Project, as the Mangdechhu Project power would be get­ting evac­u­ated to In­dia at 400kV Sub­sta­tion Alipur­d­uar (West Ben­gal) through the trans­mis­sion lines of Pu­natshangchhu–I & II Hy­dro­elec­tric Projects which has al­ready been com­mis­sioned.

The qual­ity of work at site was main­tained by su­per­vi­sion at batch­ing plants, place­ment sites, check­ing of qual­ity of ma­te­ri­als and work­man­ship. The con­crete poured in dif­fer­ent struc­tures was tested in its fresh and hard­ened state at batch­ing plants. Fresh con­crete prop­er­ties like slump value, air con­tent and tem­per­a­ture were de­ter­mined be­fore dis­patch of con­crete from batch­ing plant. Hard­ened con­crete was tested by cast­ing cubes and tested at 7 & 28 days for com­pres­sive strength.

To­tal 1066 sets of cubes of con­crete were cast and tested for com­pres­sive strength. The strength test re­sults were sta­tis­ti­cally an­a­lyzed to as­sess their con­form­ity with the ac­cep­tance cri­te­ria given in IS 456:2000.

Mean­while, the first Re­vised Cost Es­ti­mate (RCE) was ap­proved by the GoI for Nu./Rs. 40,206.30 Mil­lion(M) as on March 2014 price level, an in­crease of Nu./ Rs.11,243.30M from the ini­tial ap­proved cost of Nu./Rs.28,963.00M as on March 2008 price level.

While the sec­ond RCE for Nu./Rs.46,723.85M as on March 2016 price level has been ap­proved by the GoI. As on 30th June 2018, the MHPA has re­ceived a to­tal amount of Nu./Rs.45,668.50M.

Of the to­tal re­ceipts, Nu./Rs.44,697.60M has been spent till 30th June 2018 in­clud­ing ad­vances for var­i­ous ac­tiv­i­ties, rep­re­sent­ing fund uti­liza­tion of 97.8 per­cent against to­tal fund re­ceipt from GoI.

All set for go: The test­ing will en­sure the per­fec­tion of the unit align­ment and also the re­sponse of the aux­il­iary equip­ment in the power house

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