erection & commissioning of trfr.-sh.c.p.deshmukh

7/28/2019 Erection & Commissioning of Trfr.-sh.c.p.deshmukh

1/25

INSTALLATION

COMMISSIONING

OPERATION AND

MA INTENANCE OF

TRANSFORMERS

by

C.P.DESHMUKHSR.DGM BHEL BHOPAL


2/25

ERECTION AND COMMISSIONING

OF TRANSFORMERS

Site establishment. Infrastructures and T/P mobilization.

Receipt storage and inspection.

Placement on plinth and installation.

Erection of fittings and accessories.

Dry out & pre-commissioning checks.

Commissioning. Monitoring performance.


3/25

AVAILABILITY OF SITE FRONT Identification and allotment of land

for Site establishment &

construction of stores. Documents like shipping list,

drawings and leaflets for sitereference.

Infrastructures and T/P mobilization.

Extensive site co-ordination.


4/25

RECEIPT HANDLING STORAGE &

INSPECTION

Receipt of material, unloading and properstorage.

Physical inspection of material and tank for

shortages / damages if any. Shortages identification for re-plenishment

Indoor Storage of sensitive instrumentaccessories in well protected store.

Storage of accessories outdoor oncompacted land to prevent againstrusting.


5/25

INSPECTION OF TRANSFORMER ON RECEIPT

AT SITE

Check N2 pressure.

Identify external damages/ dents on various

locations.

Internal inspection to check movement of core andwinding during handling / shunting / unloading en

route transportation.

Discrepancy if any to be reported to manufacturer.

Healthiness of core and winding to be ascertainedby testing if necessary.

After inspection transformer tank to be pressurized

to 2.0 psi and maintained till erection is taken up.


6/25

INFRASTRUCTURE TOOL &

PLANTS

Long boom crane for bushing mounting. Vinch and pulley for dragging.

High vac filter machine (4000lph min. cap.)

Oil storage tank (20kL cap.)

Current injection kit for CT testing.

Testing instruments for LV test on the trfr.

Vacuum pump suitable for 1mm vacuum. Dew point meter if required.

Oil BDV and PPM testing kit.

Tan delta / Cap. Testing kit.


7/25

ERECTION/ INSTALLATION

Ensure healthiness of transformerfittings and accessories.

Clean oil storage tank and filter

machine to remove old /

contaminated oil / dirt in it.

Availability of site front near /

around transformer plinth.

Requisite power supplier near

foundation.


8/25

LONGER STORAGE OF

TRANSFORMER

If storage without oil more that 6 monthsdryness of winding insulation must be

assessed.

Dry nitrogen (-55C) to be used todetermine dew point of insulation.

Higher dew point indicates moistureingress in solid insulation.

Nitrogen purging to remove moisture till

desire dew point achieved.


9/25

DESIRED DEW POINT IN

TRANSFORMERTrfr temp. Dew point( C)25 -24

31 -19

33 -1736 -15

Use pure and dry N2 (-55 C) dew point.

Pressurize tank upto 2.0 psi

N2 filling after vacuuming for 48 hrs. Measure dew point after 24hrs of filling.


10/25

PLACEMENT OF TRANSFORMER

ON PLINTH Inspection of plinth as per center line of

main tank and cooling bank/ pockets.

Placement of main tank on plinth.

Start cooling bank erection after installationof A frame / headers after correct marking

as per drawing.

All the pipe works and fittings to ensure in

healthy condition.

Welding rectification /painting of pipe work.


11/25

TURRET ERECTION

Turret CTs to be cleaned and dried withheater to remove moisture if any. Turret CT testing for IR value, mag. Current,

ratio and polarity.

Results to be compared with works values.

Variations in test results to be reported andconcurred by manufacturer.

Turrets erection to be carried out as per

reference mark to ensure correct

installation.


12/25

BUSHING HANDLING

Make bushings vertical on a temporarystand.

Observe leakages if any.

Clean porcelain with dry cloth.

Tighten oil filling plugs and test tap

assembly for adequacy.

Check oil loss if any from MOG & re-

tighten.

If oil loss is from porcelain/ flanges joint

manufacturer to be consulted.

Bushings mounting after testing for tandelta / cap. Values.


13/25

BUSHING TESTING AND

ERECTION Capacitance and Tan delta testing at 10kV. Tan delta value < 0.007.

Capacitance to be comparable with factory

results.

Adequacy of oil in the bushing.

Minor damages on the bushing despite

good test results to be shared with

manufacturer.

Bushing to be erected with immense care.

Lead orientation inside the bushing tube

and terminal connection must be welltighten.


14/25

TRANSFORMER TESTING

BEFORE OIL FILLING

Polarity, vector group and ratiomeasurement on all tap positions. winding resistance measurement on

normal, minimum and maximum tap

positions.

Isolation test between core, end frame andtank.

Continuity during tap change operation.

magnetization current.

Note: Consult manufacturer if results do not

match with works values for corrective action.


15/25

VACUUM PULLING

Erection of all fittings and accessories.

Internal inspection to remove all the dirt and dust

from the transformer tank.

Retightening of cleat nuts and bolts. Re-tightening of on load tap changer leads

connected to the selector.

Blanking all the openings and tightening.

Vacuuming upto 1mm of HG. Checking of leakages and tightening.

Final vacuuming for the period specified (48hrs min).


16/25

OIL PREPARATION & FILLING

Oil supplied to confirm IS:335. Clean oil storage tank using good

oil to remove residual.

Recondition & clean filter machine.

Preparation of oil in separate tank to

achieve BDV more than 60kV.

Evacuation of main tank and

maintaining vacuum up to 1 torr.

For min 48 hrs.

Filling of oil under vacuum.


17/25

OIL FILLING IN CONSERVATOR

Check functioning of MOG with floatarm movement.

Inflating rubber bellow ofconservator for 0.1psi and check

leakages. Topping oil in the conservator from

bottom and releasing air fromvalves .

Pressure testing of transformer for

12 hrs at 5 psi & attend leakages ifany.


18/25

DRY OUT AND TESTING

Oil filtration through high VAC filtermachine under vacuum and 55 Ctemperature of transformer.

Continue dry out till BDV > 70kV and PPM 1.25

IR values comparable with factory results.


19/25

TRANSFORMER TESTING

Measurement of magnetizing current. Resistance measurement of the windings. Ratio test on all tap position.

Magnetic balance test.

IR value of the winding (60 sec and 600 sec)

Isolation of core and end frame.

OLTC manual and electrical operation.

Tan delta and cap. of bushing and wdg.

Dissolve gas analysis of the oil sample.

FRA of the transformer.


20/25

PRE-COMMISSIONING CHECKS

Compare all low voltage test resultsand short out discrepancy if any. Releasing of air from different pockets after

allowing 24 hrs. settling time.

Ensure proper earthing of tank, turret,

bushings flanges and test tap assembly.

Ensure perfect earthing of tank to

mother earthing.

Ensure perfect bushing top terminal

connections to avoid heating.

Commissioning the transformer and

monitoring performance for 24 hrs.


21/25

BENCH MARKING PARAMETERS

Description RemarksRatio, Resistance,

Mag.current &

isolation testing

Bench marking reference

for future testing /

maintenance.

Tan delta and

capacitance ofbushing.

Increase in tan delta

(> 0.007) & increase in

capacitance is warning.

BDV & PPM Increase in PPM and

reduction in BDV indicate

moisture.

DGA of oil Before & after charging.

24hrs and 7 days after

charging & analyze for

incipient fault if any.


22/25

MAINTENANCE SCHEDULE OF

TRANSFORMER

Inspection RemarksTransformer oil Ensure value as per IS: 1866

and filter if required.

Oil conservator Check MOG and air cell

functioning

Buchholz relay Check gas and release if dry

air.

Gasket joints Retighten leaking bolts

On load tap changer

diverter

Draw out diverter, clean and

tighten contacts. Replace oil.Bushing top

connectors

Check contact joints and re-

tighten.

OTI WTI pockets Top up oil in the pockets

O O OG O O G O


23/25

METHODOLOGY FOR OVERHAULING OF

TRANSFORMER IN OPERATION FOR MORE

THAN 7 YEARS

SL

NO

ACTIVITIES

1. DISMANTLING OF BUSHINGS & ACCESSORIES AFTER DRAINING OIL.

2. INTERNAL INSPECTION & TIGHTENING OF BOLTED JOINTS.

3. OVERHAULING OF OLTC/OFF CKT. TAP SWITCH

4. REPLACEMENT OF DAMAGED CLEAT OF TERMINAL GEAR.

5. CLEANING & REMOVAL OF SLUDGE FROM TANK.

6. BOXING TRFR. AFTER REPLACEMENT OF GASKET.

7. ERECTION OF BUSHING, ACCESSORIES & BOXING THE TRFRS.

8. DRY OUT OF TRFR. BY VACUUMING / N2 FILLING & HEATING METHOD.

9.. OIL FILLING, HOT OIL CIRCULATION & PAINTING

10. TESTING & RECHARGING.


24/25

PROBLEMS DURING FIRST

COMMISSIONING AND LIQUIDATION

PROBLEMS CORRECTIVE ACTIONS

Buchholz alarm / tripping due to

accumulation of trapped air

evolution

Release air and identified air ingress

locations from pump flanges. Re-tighten

the flange joints.

OLTC surge relay operation due to

bad / moist oil and moisture indiverter components.

Cleaning of diverter with hot oil and

topping up with high BDV oil.

PRV tripping due to oil blockade or

excessive oil in conservator .

Ensure opening of valves and lower oil in

the conservator upto 35C level.

Oil leakage from bushing top due

to excess oil / plug looseness.

Drain 2/3 liters of oil and tighten the

plugs.

MOG alarm due to float / air cell Check float arm and replace air cell if

found punctual.

Buchholz trip on pump starting

due to low oil in conservator

Pump flanges to be tightened and oil in

conservator to be topped up (35C level).

Introduce time delay between starting of

pumps.


25/25

THANK YOU