REHABILITATION PROJECT

Introduction

Warsak Power Station is a monument of the friendship of Canada and Pakistan.Warsak Power Station was built in two phases as co-operative effort between the two Governments. Construction of 1st phase started in 1951 and in 1960-61, four generating units of 40 MW capacity each were commissioned. The 2nd phase began in 1975 and two more 41.48 MW units were commissioned respectively in 1980-81. The total installed capacity thus amounted to 242.96 MW. With time the power generating capacity was reduced to 150 MW. The following two main causes/problems were identified for the accelerated deterioration/reduction in output:

  • Structural deformation of the powerhouse.
  • Rapid erosion in the hydraulic equipment due to quantity and abrasive nature of the silt carried in the Kabul River.

As far as the problem No.1 is concerned, WAPDA has been closely monitoring it. Since early seventies when cracks in the Power House building started appearing besides the problem of misalignment of the generating units/turbines. In the beginning, the problem was attributed to seismic effects, uplift pressures and geological changes in the vicinity of Power House Building. It took about 20 years to diagnose the problem of Power House building movement/structural deformation being Alkali Aggregate Reactivity (AAR). The AAR is a strong chemical reaction, which occurs when concrete, is made with cement having high contents of Alkali and Aggregate containing silicon particles. Favorable condition for the reaction is wet and humid environments which causes expansion, swelling and cracking resulting in considerable displacement of concrete mass.

Project Objective

The main objective of Rehabilitation Project is to attack the above mentioned problems n an attempt to rehabilitate the power Plant, thus increasing its service life and prolonging its ability to provide much needed power to the National Grid. To achieve this objective the Govt. of Pakistan and the Govt. of Canada have again joined hands. This being one of the more visible of Canada's Development Projects in Pakistan. Despite it relatively small size, the Warsak Plant is very important to WAPDA's system because:

  • it provides important peaking power.
  • it is the earliest of all hydro-electric plants in the country to start generating after the dry season.
  • it relieves the extreme low voltage problem at Peshawar, Kohat, Parachinar and adjoining areas.

OUTLINE OF THE  WORK REQUIREED

Modification to Mitigate the Effects of AAR

Nothing practical can be done to stop the AAR. Hence steps must be taken to Ensure that continuing expansion of the sub structure concrete will not compromise the stability of the powerhouse and that it will have the minimum effect on the operation of equipment. We have already carried out the following treatment to attack the AAR problem on first four units:-

  • Cutting of slots at appropriate locations in the concrete sub structure to relieve existing stresses and to accommodate future expansion.
  • Steel anchors have been installed, primarily to help maintain the structural integrity of the badly cracked concrete mass.
  • Refurbishing of butterfly valves of the units.
  • Shifting of the stators of units 2 & 4.

The above mentioned works have proved successful resulting in a considerable increase in the generating capability of the Power House by generating 231 MW on September 30, 1994 against the previous highest recorded generation of 225 MW.

Scope of Work under Rehabiliation Process

  1. Civil Works
    • Re-alignment of Power House crane rails and replacement of cracked or badly worn out crane wheels were completed.
    • Provision of 2 overhead cranes with tandem operation facility to lift the maximum weight of the rotor were completed.
    • Repair of roof leaks.
    • Repair of roof structural steel.
    • Repair of Power House concrete floors and walls including patch of cracks and reinforcing bars.
    • Treatment of substructure concrete of units 5 & 6.
    • Downstream column alignment.
    • Modification to trash racks with automatic sill cleaning device(50% completed).
    • Repairs in the spillway sill beams and spillway gates.
  2. Mechanical and Electrical Works
    • Re-alignment of Power House crane rails and replacement of cracked or badly worn out crane wheels were completed.
    • Refurbishing of the butterfly valves of units 1-6 were completed.
    • Installation of slip joints units 1-4 were completed.
    • Refurbishing of the damaged mechanical components of all the six units.
    • Rectification of defects in the draft tube gates and gentry crane mechanism.
    • Alignment of turbine/generator units is in progress.
    • Provision of by-pass valve and replacement of seal and sill beam of intake/draft tube gates (by pass valve installed).
    • Replacement of stator windings with the provision of one winding as spare.
    • Replacement of the main circuit breakers of switchyard was completed.

 Remedial Measures To Reduce The Amount Of Sediment To Power Tunnel

The work to attack the 2nd main problem i.e. sedimentation in the approach channel of the intake of the powerhouse is in its preliminary stage. M/s LASSALLE Consulting Group Inc is carrying out model studies at Quebec in Canada. for suggesting the most beneficial solution for minimizing the abrasive silt entry in the Power House resulting in rapid deterioration of turbine parts. (Works not possible).

Importance Of The Project

Warsak is so located that it has to play an important role in establishing voltage in Peshawar and further in Kohan, Parachinar, and Bannu. As such, its fullest capacity has to be restored.

First Rehabilitation Project (1996-2006)
Phase-I Rehabilitation was carried out due to two major reasons, firstly Structural deformation due to Alkali Aggregate Reaction (AAR) and secondly, severe erosion of the hydraulic equipment due to abrasive nature of silt carried in the Kabul River. Governments of Pakistan and Canada jointly carried out the Rehabilitation Project under CIDA Grant of CD 27 million during 1996~2006. As a result of the rehabilitation works completed in this phase, the Civil Structures became stable, besides, the reduced capacity of Power Station increased from 150 MW to about 220 MW.

Second Rehabilitation Project (Planned)
The aging problems of E&M equipment aggravated further with the passage of time, resulting in consequently the generating capacity reduced to 193 MW and reliability of the station also reduced. Second (2nd) Rehabilitation of Warsak Hydroelectric Power was planned with the objective to overcome the aging problems, regain the capacity loss of 50 MW with reliable annual energy generation of 1,144 GWh, upgrade and modernize the old system and achieve another life cycle of 30 to 40 years. Feasibility Study was carried out in 2013 by engaging the Consultants RSWI-DCE JV. Based on the most viable option detailed design and tender documents have also been prepared by the same Consultants. Cost Benefit Ratio and EIRRare3.65 and 26.9% respectively.

Contracting Strategy
Following Works will be carried out in the Rehabilitation Project:

  • Package I

Trash Rack Cleaning and Handling Machine and associated Civil Works

  • Package II

New wire rope Spillway hoist and associated Civil Works

  • Package III

Stator Windings for Unit 3

  • Package IV

Civil Works

  • Package V

Powerhouse Rehabilitation Works

(Turbine Generator, Excitation &Governor System, Protection, Control & Instrumentation)

  • Package VI

Transformers

Project Cost:  (Million PKR)

     Local              FEC              Total

10,970.717      11,283.518    22,254.235

Completion Period 

Seven (7) years.

Present Status

  • Feasibility Study, Tender Documents and Detail Design were completed by the consultants RSWI-DCE JV.

  • PC-I of the Project amounting to PKR 22,254.235 Million was approved by ECNEC in its meeting held on 9.7.2015.

  • AFD / KfW / EIB (EDPs) board has approved a loan of Euro 130 Million to provide following finances for the Project:

                   KfW 40 M Euro

                   AFD 40 M Euro

                   EIB 50 M Euro

                   Euro 4.5 Million Grant for Community Development

 

In Pictures