Title of Invention	"IN-SITU REPAIR OF HYDRO GENERATOR STATOR WINDING"
Abstract	An in-situ process for repair of hydrogenerator stator winding bars in particular overhang stator winding bars, involving partial dismantling of the hydrqgenerator, comprising the steps of dentifying the failed winding zone and the fused copper conductor; removing deposits from the affected zone in the identified copper conductors by cleaning and cutting characterized by; brazing the elementary conductors by making 45° joint; as herein described, grinding the brazed joints; staggering the joints of the conductors by placing the joints in different tires to achieve the pre-repairing bar conductor stack height; bending manually the conductor's edge after brazing wherein the step of bending comprises a step of annealing the copper conductors to make the conductors bendable such as to match the intricate profile of the overhang portion, insulating the brazed joints of the elementary conductors by inter stand insulation of the Fig.1

Title of Invention

"IN-SITU REPAIR OF HYDRO GENERATOR STATOR WINDING"

Abstract

An in-situ process for repair of hydrogenerator stator winding bars in particular overhang stator winding bars, involving partial dismantling of the hydrqgenerator, comprising the steps of dentifying the failed winding zone and the fused copper conductor; removing deposits from the affected zone in the identified copper conductors by cleaning and cutting characterized by; brazing the elementary conductors by making 45° joint; as herein described, grinding the brazed joints; staggering the joints of the conductors by placing the joints in different tires to achieve the pre-repairing bar conductor stack height; bending manually the conductor's edge after brazing wherein the step of bending comprises a step of annealing the copper conductors to make the conductors bendable such as to match the intricate profile of the overhang portion, insulating the brazed joints of the elementary conductors by inter stand insulation of the Fig.1

Full Text	FIELD OF INVENTION The present invention emanates from the field of repair technology involving hydrogenerator stator winding. The invention in particular relates to a process of in-situ repair of hydrogenerator stator winding in particular the overhang stator bars involving partial, dismantling of the hydrogenerator. BACKGROUND OF THE INVENTION Winding is very important part of Hydro-generator. The bars are made of large number of insulated rectangular copper conductors of small section interposed in slot portion to reduce eddy and circulating currents. The over hang part is tied with bandage rings after placing insulating spacers between them. The bars are coated with semi-conducting varnish to avoid corona and flash over. According to the prior art method whenever a fault in stator winding bar of a hydrogenerator stator occurs near the upper or lower bar head cover, the repair method comprises replacing the winding bar after removing the poles, upper fan segments, upper air baffle segments; and turning of rotor and removing the bar head covers; debrazing of bar head joints and removing the damage winding bars; and replacing the defective winding bars with new winding bars. This process takes a long time for bringing the machine back ob grid and further proves to be expensive. In grist, the following steps are involved in the prior art process. a. Removing Rotor upper fan segments. b. Removing upper air baffle and lower air baffle segments. c. Turning the rotor and removing the poles. d. Removing and replacing the failed lower and upper stator winding bars. e. Testing electrical parameters of the repaired stator winding. f. Assembling the poles and the rotor parts. The disadvantages of the prior art process include : • Involving of heavy amount of work, and increase in time cycle of rectification of machine. • Loss in power generation and exponential increase in repair cost in particular due to high replacement cost of stator winding bars. OBJECTS OF THE PRESENT INVENTION It is the object of the invention to propose an in-situ process for repair of Hydro generator stator winding bar in particular the stator winding bars disposed at overhang portion without removal of poles, upper fan and upper air baffles. Another object of the present invention is to provide an in-situ process for repair of hydrogenerator stator windings bars without complete dismantling and reassembly of the stator components. Yet another object of the present invention is to provide an in-situ process for repair of hydrogenerator stator windings bars which reduce the time and cost of the repair cycle. Still another object of the present invention is to provide an in-situ process for repair of hydrogenerator stator windings bars, which comprehensively reduces the power generator loss. A further object of the present invention is to provide an in-situ process for repair of hydrogenerator stator windings bars, which improves the quality of repair and enhances the life of the hydrogenerators, in particular old generators. SUMMARY OF THE INVENTION Accordingly there is provided an in-situ process for repair of hydrogenerator stator winding bars in particular overhang stator winding bars involving partial dismantling of the hydrogenerator, comprising the steps of: - identifying the failed winding zone and the fused copper conductor; - removing deposits from the affected zone in the identified copper conductors; - brazing the elementary conductors by making 45° joint; - grinding the brazed joints; - staggering the joints of the conductors; - bending manually the conductors' edge after brazing; - insulating the brazed joints of the elementary conductors; - carrying out tests for the brazed joints and tests for electrical parameters of the hydrogenerator stator winding; - the step of brazing comprises scarf brazing of the identified conductors on overhang position, - the step of staggering comprises placing the joints in different tires to achieve the pre-repairing bar conductor stack height, - the step of bending comprise3s a step of annealing the copper conductors to make bendable such as to match the intricate profile of the overhang portion, and - the step of insulation comprises inter stand insulation of the brazed joints. BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES Fig. 1 - shows the stator winding bars of a hydrogenerator including the winding bars in overhang position. Fig. 2 - cutting and brazing of elementary conductor bars. Fig. 3 - staggering of joints of elementary conducts. DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION The process of vin situ repair of hydro generator stator winding' involves removal of damaged conductors, brazing new elementary conductors and insulating, dressing them to the shape of bars. STEPS ADOPTED IN THE PROCESS a. Identification ad separation of fused copper conductors (1). Failed zone (2) of the winding (1) is to be identified and cleaned by cleaning agent. Burnt brazing are cut off and damaged insulation is removed. Fused melted copper conductors are separated. b. Removal of melted copper conductors/deposits from affected portion. Cleaning the rectification zone (2). Cutting the brazing and removing the distance spacers. Gently, bending the conductors (lc) of upper bar in such a way that the lower bar zone 1(d) is clearly visible. Cutting and removing the melted conductors. c. Brazing of elementary conductors in situ bv making 450 scarf joint Providing equivalent fresh elementary conductors (6) of the bars. These new conductors (6) should be of same size as that of the elementary bar conductors and should have same electrical properties. Cutting of the conductors (6) in taper at about 45° and brazing new conductors at corresponding angle. Matching of the new conductor is required before brazing. Perfect leveling of both conductors. d. Grinding of brazed joints. After brazing the joints of the new conductors (6) and the elementary conductors (1), removing the extra brazing material deposited on the joints. Testing the joints ultrasonically. e. Staggering and brazed joints in different tiers. Staggering the joints of conductors (16) in different tiers to improve the strength of joints and simultaneously maintaining the bar conductor stack height. f. Forming of conductor ends after gas torch annealing. After brazing, manually bending the conductors (1,6) edge wise. Annealing the conductors (1,6) before bending. g. Inter-strand insulation of brazed joints of elementary conductors. Removing the damaged / brunt insulation followed by taper cutting of body insulation. Cleaning the zone very thoroughly. Placing insulation sheet (3) between the tiers including m.s. strip (4) and forming manually the stack to required shape. h. Dressing and forming of conductors matching with the old conductors of bars. Carrying out the dressing and forming of conductors (6) matching with the old conductors bars (1) by tightening of the conductors (1,6) to form the head. Carrying out, taping of over hang portion, brazing of bar heads and fixing of insulation covers (30), pouring of compound. QUALITY ASSURANCE In order to ensure the healthiness of the winding after repairing according to the novel process, various tests are carried out. The details are as herein under: A. Ultrasonic Examination : To assess the healthiness of brazed joints of stator winding ultrasonic test is to be performed as well as D.C. resistance of all 3 phases to be measured. To assess the electrical healthiness of stator winding, the following tests are to be carried out: a. Insulation Resistance of stator winding. b. Absorption factor. c. Polarization index. WE CLAIM: 1. An in-situ process for repair of hydrogenerator stator winding bars in particular overhang stator winding bars, involving partial dismantling of the hydrogenerator, comprising the steps of:- - identifying the failed winding zone and the fused copper conductor; - removing deposits from the affected zone in the identified copper conductors by cleaning and cutting characterized by; - brazing the elementary conductors by making 45° joint; as herein described, - grinding the brazed joints; - staggering the joints of the conductors by placing the joints in different tires to achieve the pre-repairing bar conductor stack height; - bending manually the conductor's edge after brazing wherein the step of bending comprises a step of annealing the copper conductors to make the conductors bendable such as to match the intricate profile of the overhang portion, - insulating the brazed joints of the elementary conductors by inter stand insulation of the brazed joints. 2. An in-situ process for repair of hydrogenerator stator winding bars as substantially described herein with reference to the accompanying drawings.

Full Text

FIELD OF INVENTION
The present invention emanates from the field of repair technology involving hydrogenerator stator winding. The invention in particular relates to a process of in-situ repair of hydrogenerator stator winding in particular the overhang stator bars involving partial, dismantling of the hydrogenerator.
BACKGROUND OF THE INVENTION
Winding is very important part of Hydro-generator. The bars are made of large number of insulated rectangular copper conductors of small section interposed in slot portion to reduce eddy and circulating currents. The over hang part is tied with bandage rings after placing insulating spacers between them. The bars are coated with semi-conducting varnish to avoid corona and flash over.
According to the prior art method whenever a fault in stator winding bar of a hydrogenerator stator occurs near the upper or lower bar head cover, the repair method comprises replacing the winding bar after removing the poles, upper fan segments, upper air baffle segments; and turning of rotor and removing the bar head covers; debrazing of bar head joints and removing the damage winding bars; and replacing the defective winding bars with new winding bars. This process takes a long time for bringing the machine back ob grid and further proves to be expensive. In grist, the following steps are involved in the prior art process.
a. Removing Rotor upper fan segments.
b. Removing upper air baffle and lower air baffle segments.
c. Turning the rotor and removing the poles.
d. Removing and replacing the failed lower and upper stator winding bars.
e. Testing electrical parameters of the repaired stator winding.
f. Assembling the poles and the rotor parts.
The disadvantages of the prior art process include :
• Involving of heavy amount of work, and increase in time cycle of rectification of machine.
• Loss in power generation and exponential increase in repair cost in particular due to high replacement cost of stator winding bars.
OBJECTS OF THE PRESENT INVENTION
It is the object of the invention to propose an in-situ process for repair of Hydro generator stator winding bar in particular the stator winding bars disposed at overhang portion without removal of poles, upper fan and upper air baffles.
Another object of the present invention is to provide an in-situ process for repair of hydrogenerator stator windings bars without complete dismantling and reassembly of the stator components.
Yet another object of the present invention is to provide an in-situ process for repair of hydrogenerator stator windings bars which reduce the time and cost of the repair cycle.
Still another object of the present invention is to provide an in-situ process for repair of hydrogenerator stator windings bars, which comprehensively reduces the power generator loss.
A further object of the present invention is to provide an in-situ process for repair of hydrogenerator stator windings bars, which improves the quality of repair and enhances the life of the hydrogenerators, in particular old generators.
SUMMARY OF THE INVENTION
Accordingly there is provided an in-situ process for repair of hydrogenerator stator winding bars in particular overhang stator winding bars involving partial dismantling of the hydrogenerator, comprising the steps of:
- identifying the failed winding zone and the fused copper conductor;
- removing deposits from the affected zone in the identified copper conductors;
- brazing the elementary conductors by making 45° joint;
- grinding the brazed joints;
- staggering the joints of the conductors;
- bending manually the conductors' edge after brazing;
- insulating the brazed joints of the elementary conductors;
- carrying out tests for the brazed joints and tests for electrical parameters of the hydrogenerator stator winding;
- the step of brazing comprises scarf brazing of the identified conductors on overhang position,
- the step of staggering comprises placing the joints in different tires to achieve the pre-repairing bar conductor stack height,
- the step of bending comprise3s a step of annealing the copper conductors to make bendable such as to match the intricate profile of the overhang portion, and
- the step of insulation comprises inter stand insulation of the brazed joints.
BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES
Fig. 1 - shows the stator winding bars of a hydrogenerator including the winding bars in overhang position.
Fig. 2 - cutting and brazing of elementary conductor bars.
Fig. 3 - staggering of joints of elementary conducts.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION
The process of vin situ repair of hydro generator stator winding' involves removal of damaged conductors, brazing new elementary conductors and insulating, dressing them to the shape of bars.
STEPS ADOPTED IN THE PROCESS
a. Identification ad separation of fused copper conductors (1). Failed zone
(2) of the winding (1) is to be identified and cleaned by cleaning agent.
Burnt brazing are cut off and damaged insulation is removed. Fused
melted copper conductors are separated.
b. Removal of melted copper conductors/deposits from affected
portion.
Cleaning the rectification zone (2). Cutting the brazing and removing the distance spacers. Gently, bending the conductors (lc) of upper bar in such a way that the lower bar zone 1(d) is clearly visible. Cutting and removing the melted conductors.
c. Brazing of elementary conductors in situ bv making 450 scarf
joint
Providing equivalent fresh elementary conductors (6) of the bars. These new conductors (6) should be of same size as that of the elementary bar conductors and should have same electrical properties. Cutting of the conductors (6) in taper at about 45° and brazing new conductors at corresponding angle. Matching of the new conductor is required before brazing. Perfect leveling of both conductors.
d. Grinding of brazed joints.
After brazing the joints of the new conductors (6) and the elementary conductors (1), removing the extra brazing material deposited on the joints. Testing the joints ultrasonically.
e. Staggering and brazed joints in different tiers.
Staggering the joints of conductors (16) in different tiers to improve the strength of joints and simultaneously maintaining the bar conductor stack height.
f. Forming of conductor ends after gas torch annealing.
After brazing, manually bending the conductors (1,6) edge wise. Annealing the conductors (1,6) before bending.
g. Inter-strand insulation of brazed joints of elementary
conductors.
Removing the damaged / brunt insulation followed by taper cutting of body insulation. Cleaning the zone very thoroughly. Placing insulation sheet (3) between the tiers including m.s. strip (4) and forming manually the stack to required shape.
h. Dressing and forming of conductors matching with the old conductors of bars.
Carrying out the dressing and forming of conductors (6) matching with the old conductors bars (1) by tightening of the conductors (1,6) to form the head. Carrying out, taping of over hang portion, brazing of bar heads and fixing of insulation covers (30), pouring of compound.
QUALITY ASSURANCE
In order to ensure the healthiness of the winding after repairing according to the novel process, various tests are carried out. The details are as herein under:
A. Ultrasonic Examination : To assess the healthiness of brazed joints of stator winding ultrasonic test is to be performed as well as D.C. resistance of all 3 phases to be measured.
To assess the electrical healthiness of stator winding, the following tests are to be carried out:
a. Insulation Resistance of stator winding.
b. Absorption factor.
c. Polarization index.

WE CLAIM:
1. An in-situ process for repair of hydrogenerator stator winding bars
in particular overhang stator winding bars, involving partial
dismantling of the hydrogenerator, comprising the steps of:-
- identifying the failed winding zone and the fused copper conductor;
- removing deposits from the affected zone in the identified copper conductors by cleaning and cutting characterized by;
- brazing the elementary conductors by making 45° joint; as herein described,
- grinding the brazed joints;
- staggering the joints of the conductors by placing the joints in
different tires to achieve the pre-repairing bar conductor stack height;
- bending manually the conductor's edge after brazing wherein the step of bending comprises a step of annealing the copper conductors to make the conductors bendable such as to match the intricate profile of the overhang portion,
- insulating the brazed joints of the elementary conductors by inter stand insulation of the brazed joints.
2. An in-situ process for repair of hydrogenerator stator winding bars as substantially described herein with reference to the accompanying drawings.

Documents:

1749-DEL-2004-Abstract-(13-10-2010).pdf

1749-del-2004-abstract.pdf

1749-DEL-2004-Claims-(13-10-2010).pdf

1749-del-2004-claims.pdf

1749-DEL-2004-Correspondence Others-(08-11-2011).pdf

1749-DEL-2004-Correspondence-Others-(13-10-2010).pdf

1749-del-2004-correspondence-others.pdf

1749-del-2004-description (complete).pdf

1749-del-2004-description (provisional).pdf

1749-del-2004-drawings.pdf

1749-del-2004-form-1.pdf

1749-del-2004-form-18.pdf

1749-del-2004-form-2.pdf

1749-del-2004-form-3.pdf

1749-del-2004-form-5.pdf

1749-DEL-2004-GPA-(13-10-2010).pdf

1749-del-2004-gpa.pdf

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Patent Number

254461

Indian Patent Application Number

1749/DEL/2004

PG Journal Number

45/2012

Publication Date

09-Nov-2012

Grant Date

06-Nov-2012

Date of Filing

17-Sep-2004

Name of Patentee

BHARAT HEAVY ELECTRICALS LTD

Applicant Address

BHEL HOUSE, SIRI FORT, NEW DELHI-110 049, INDIA

Inventors:

#	Inventor's Name	Inventor's Address
1	SINGH PRMOD KUMAR	C/O BHARAT HEAVY ELECTRICALS LIMITED, HEAVY EQUIPMENT PLANT, RANIPUR, HARDWAR-249403 UTTARANCHAL STATE, INDIA
2	RASTOGI SURENDRA KUMAR	C/O BHARAT HEAVY ELECTRICALS LIMITED, HEAVY EQUIPMENT PLANT, RANIPUR, HARDWAR-249403 UTTARANCHAL STATE, INDIA
3	SHRIVASTAVA RAMESH CHANDRA	C/O BHARAT HEAVY ELECTRICALS LIMITED, HEAVY EQUIPMENT PLANT, RANIPUR, HARDWAR-249403 UTTARANCHAL STATE, INDIA

PCT International Classification Number

H02K

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA