Obra (Hydel), District : Sonebhadra, Uttar Pradesh

Installed capacity - 99 MW (3x33MW)

No. of units - 3

Sailent Features

Location	Obra(District - Sonebhadra)
Name of River	Rihand / Renuka
Name of Dam	Obra Dam
Location of Dam	11km. upstream of confluence of Rihand/Renuka river with Sone river
DAM
Type	Earth and rock filled dam with spillway
Length on the Top & Top Width	2 km. & 10 M
Crest Length
Main dam	450 M
Left dyke	577 M
Right dyke	575 M
Maximum height of dam above river bed	29.23 m.(excluding camber of 1.57 M)
No. & size of gates	15 nos, 10.4 M / (H) x 22.2 M (W)
Reservoir
Capacity at Normal Reservior Level	211 x 106 Cubic.M
Maximum reservoir level	193.30 M
Minimum reservoir level	192.65 M
Intake Structure	Sluice Gate- 3 nos., each size 6.54M x 10.78 M)
Water Conductor system	Penstock (3 Nos. pipes, each I.D. 7.925 M)
Power House & Control Room
Location	Right Flank
Type	Surface
Size	L - 100 M., W - 23.11 M., at Top and 31.48 M at base
Height	Above turbine floor - 21.30 M
Net / Rated / Design Head	20.4 M
Discharge of each machine at rated head	194 cumecs
Installed Capacity	3x33 MW - 99 MW
Turbine
Type	Vertical Kaplan
HP	45300
Normal Speed	115.4 rpm
Specific Speed	572
Runner Dia	5.17m.
Efficiency	92.2 % at 75 % output
Governing System
Make	H.E.(I) Ltd.
Type	Hydro Mechanical
Designed Sensitivity	.01 %
Governing System
Type	Vertical Umbrella
KVA	36.67
Phase	3
KV	11
Hz	50
Power Factor	0.9 at 115.4 rpm.
Full Load Efficiency	97.06 %
Excitation	Dynamic (Response Ratio 1.0)
Rating	296KW at 185V.
Tailrace
Type	Open Type (Channel, Size - 5.2 M.x5.75 M)
TWL	173.28 M
Firm Power	33000 KW
Annual Design Energy	279 MU
Generating Voltage	11 kV
Transmission Voltage	132 kV
Switchyard
Incomers	3 Nos.
Outgoing Feeders	8 Nos.(132 kV)
Unit Transformers	3 Nos. (37.5 MVA, 11/132 kV), BHEL make
Auxiliary Transformers	3 Nos. (400 KVA, 11/0.4 kV), EMCO make
Station Transformers	2 Nos. (400 KVA, 11/0.4 kV), EMCO make
Name Plate Details of Turbine & Generator
Turbine of Unit No. 1, 2 & 3
Make	HE(I) Ltd.
Type	Vertical Kaplan,
Output	45,300 BHP
Speed	115.4rpm
Runway speed	213/259,
Year of Mrf.	1965
Generator of Unit No.-1
Make	Associated Electrical Industries Ltd.
KVA	36,667
Volts	11 kV
Type	ADV 360/55,
kW	33000
Amperes	1925
RPM	115.4
HZ	50
Volt Range	11000+10% - 5%
Year	1966
P.F.	0.9
Phase	3
Excitation Volt	135
Amperes	1343
Specification	BS2613 1957:Class:B
Stator Connections	Star
Generator of Unit No.-2 & 3
Make	Heavy Electricals Ltd.
KVA	36,667
Volts	11 kV
Type	ADV 360/55,
kW	33000
Amperes	1925
RPM	115.4
HZ	50
Volt Range	11000+10% - 5%
Year	1966
P.F.	0.9
Phase	3
Excitation Volt	135
Amperes	1343
Specification	BS2613 1957:Class:B
Stator Connections	Star
Note: In Unit No.- 3 Generator winding of B class has been replaced with F class in 1996 - 1998
Cost Of the Project	2423.06 lacs
RENOVATION & MODERNIZATION SCHEME S.No. Activity No. Brief Description of R&M Activity Original Sanction Cost 1 1 Renovation of Turbine of all the three units by way of (i) Replacement of existing shaft gland system with new BHEL make LIP type Turbine rubber shaft seal assembly (ii) Replacement of existing Hydro Mechanical Governor with latest Electro Hydraulic Governor Rs. 200.00 Lacs 2 2 Replacement of old existing amplidyne of all the Three machines with new latest static Automatic Voltage Regular. RS 111.00 Lacs 3 3 Replacement of Slip ring of all the three units with new BHEL make slip rings RS 11.00 Lacs 4 4 Renovation of 132KV MOCBs of all the three units, 8 outgoing feeders & bus coupler with new SF-6 breakers RS 308.00 Lacs 5 5 Reinsulation of Generator Stator Coils and Rotor Poles Coils with 'F' Class Insulation RS 962.00 Lacs