schedule for the r & m of distribution transformers

R&M Final 2 5/12/2006 10:50 AM A-1

Schedule for the R & M of Distribution Transformers

Schedule No. Item to be

inspected

Brief description of work

1.

Connections Check for tightness. Replace and refill old/worn out

thimbles where necessary check for Provision of PVC

sleeves insulating beads on the H.T. connectors, &

replace where necessary.

2.

Oil level Check for proper oil level and top up if necessary.

Check for leakage from the drain valve, gaskets and

tank etc. & attend it if required.

3. Breather Inspect silica gel and recondition/replace, if

necessary.

4. Fuses (HT

and LT)

Check for continuity, tightness and proper rating/

size. Replace if necessary.

5. G.O. Switch Check for proper functioning and sparking & adjust

the settings, if required.

6. Diaphragm Check for cracks & replace if required.

Monthly

7.

Bushing and

arcing horns

Check for cracked and broken bushings. Clean or

replace if necessary. Examine and replace damaged

gaskets. Adjust arcing horns for proper gaps and

alignment.

1. Insulation

resistance

Check the I.R.values with 1 KV meggar. Compare the

values with the values at the time of commissioning.

Quarterly

2.

Voltage and

load

checking

Measure voltage and load during peak load conditions

at the transformers and at the tail end of LT feeders.

Measure load during peak load conditions against its

rated capacity. Balance the load on three phases and

initiate action for augmentation, if necessary.

R&M Final 2 5/12/2006 10:50 AM A-2


inspected


3.

Barbed wire

and danger

plate etc.

Check for proper installations and repaint/replace

where ever necessary.

1.

Oil Observe colour of oil, Check water content and

perform crackle test on the oil samples drawn from

the drain off valve. In case the test indicates

deterioration, perform di-electric strength test. In

case of over contamination, the transformer oil should

be replaced and drained out oil should be separately

dehydrated for its reuse.

Keep records of the test results.

Yearly

2.

Earth

testing

(to be done

during driest

part of the

year)

Check for earth resistance in respect of transformer

neutral, metal parts including body and the lightening

arrester. Ensure that this is less than 2 ohms.

Examine the whole earthing system for tightness of

connections and broken/rusted leads etc. Recondition

or replace where ever necessary.

Keep records of the test results.

1. Conservator

tank

Clean the inspection glass for proper visibility. Check

for leakage from the glass fitting.

Check for proper communication of the conservator

with transformer tank by draining some oil through

the drain valve and watching the oil in the gauge glass

to drop.

In case the oil does not drop, investigate and remove

the sludge or other obstruction(s) after dis

assembling the conservator tank. Two yearly

2. Acidity and

sludge

Check for acidity and sludge formation. In case the

acidity is more than 0.5 mg/KOH/gm, of oil then

recondition the oil.

In case the acidity is more than 1.0 mg/KOH/gm,

reclaim the quality of oil with fuller’s earth or action

of inhibitors.

Once

every 5

years

1.

Complete overhauling of the transformer.

R&M Final 2 5/12/2006 10:50 AM A-3

Schedule for the R & M of Power Transformers

Schedule No. Item to be inspected Brief description of work

1. Ambient Temp Note down the temperature and record the

maximum daily ambient temperature.

2.

Winding/Oil Temp Check that temp rise is reasonable. In case

of any abnormal variation, check the cooling

system of T/F. If the same is not found in

order. Shut down the T/F for further

investigation.

Hourly

3. Load/Voltage Check against rated figures. In case of any

variation, check the TPI.

1.

Oil level in transformer Check against transformer oil level/

temperature. Top up with dry oil, if

necessary.

2 Oil level in bushings Check for any oil leakage.

3. Relief Vent diaphragm Check for cracked or broken. Replace if

necessary.

4.

For internal abnormal noise. Check for any abnormal sound or excessive

chattering. Shut down the T/F in case of

abnormal noise, for further investigation.

5 Heaters in Junction Box Check for proper working, if provided.

Replace, if found defective/damaged.

6

External connection

(Leads/Jumpers)

Check visually for tightness and sparking on

jumpers, bushings etc. on complete

darkness. Attend it, if required.

Daily each shift

7

Bus bar and cable boxes and

cables

Check for any damage and signs of

overheating at their joints. Check for

overheating of back covers and attend, if

found excessive heated.

Monthly

1 Dehydrating breather

(i)Check for condition/colour of Silica gel.

Recondition or replace as necessary.

(ii) Ensure for free air passage

(iii) Tight, lid of the breather for air

tightness to avoid entry

(iv) Check oil level in oil cup and make up oil,

if required.

(v) Remove oil from dash pot and pour in

fresh oil where required.

R&M Final 2 5/12/2006 10:50 AM A-4


2

Bushing and gaskets Examine for cracks, Paint and dirt deposits

and gap settings. clean or replace it. Check

gaskets for leakage.

3 Cooler fan and pump

bearings, motors and

operating mechanism

Lubricate bearings, check gear box.

Examine Contacts, Check Manual control and

interlocks. Replace burnt or worn out

contacts or other parts.

4

On load tap changer driving

mechanism

Lubricate bearings, Check gear box oil level

and examine contacts. Clean/Replace burnt

or worn out contacts

5

On load tap changer

automatic control

Check all circuits independently. Check

step by step operation including limit

switches. Attend if found faulty.

6

Insulation resistance Check the I.R.values with 2.5KV rating

meggar. Convert it at 70 0 C and compare

the values with the value taken at the time

of commissioning.

7

Relays alarms, temperature

alarm and their circuits

Examine relays and alarm contacts and their

operation, fuses etc. Check for relays

functioning clean or replace the contacts if

required.

8 Arcing Horns Set the rods for alignment and for proper

gap adjustment.

9 Measuring/Protection CT’s Check for sparking and tightness of

connection and oil level.

10 Remote/Manual Switch Check for proper functioning

11 Fire fighting equipments Examine them and ensure that these are in

order.

12 Bucholtz’s relay Note the oil level in the inspection glass of

Bucholtz’s relay.

1

Oil in T/F and tap changer Check for dielectric strength. Dehydrate

the oil, if necessary. Keep continuous

record of test results.

2 Ventilators Check that air passages are free.

Quarterly

3

Bucholtz’s relay

Check proper operation by loweringthe oil

Monthly

R&M Final 2 5/12/2006 10:50 AM A-5


4 Forced cooling system (ii) Megger testing of motors(pumps)

(iii) Checking transformer ground

connections for

tightness.

5 Thermo Syphen Filters

Check for its normal working order.

6

Earth Resistance (i) Check for tightness of earth

connections.

(ii) Measure earth resistance of the (a)

T/F body, neutral and other body

parts, (b) Keep proper record of test

results. (Earth testing to be done

during driest part of the season)

1

On load tap Inspect all moving parts, contacts, brake

shoes, motor etc.clean, adjust or replace as

required.

Half Yearly

2 Oil in T/F Check acidity, PPM & BDV & compare with

standard results.

1

Oil in T/F Check Tan delta,, Sp.Resistively , sludge

contents, DGA test, compare it with

standard results.

2 Oil filled bushing Test oil for dielectric strength Dehydrate

or replace the oil, if necessary.

3 Cable box Check for sealing arrangements for filling

holes. Examine compound for cracks.

4 Surge diverter and gaps Examine for cracks and dirt deposits. Clean

or replace if necessary.

5

Gasket joints Check for tightness of bolts to avoid uneven

pressure. Replace damaged gasket.

6 Pipe connections Check oil pipes valves and plugs for

tightness and proper functioning.

7 Foundations Check for cracks, if any and setting.

Yearly

8 Bushings Test the bushings with a Hipet bushing

tester and compare with previous figures.

Quarterly

R&M Final 2 5/12/2006 10:50 AM A-6


9 Temperature indication Pockets holding thermo-meter should be

checked. Oil to be replenished, if required.

10 Dial type oil guage Check pointer for free operation. . Adjust,

if required.

11 Paint work Should be inspected

12

Conservator tank (i) Check for proper communication of

the conservator with T/F tank by

draining some oil through drain off

valve and watching the oil in gauge

glass to drop.

(ii) In case, the oil does not drop,

investigate and remove the sludge or

other obstructions after dis-

assembling the tank.

(iii) Check for leakage of oil from glass

side. Clean the inspection glass.

Yearly or

after

5,000

operations

1

Diverter switches for tap

changer having non-arcing

selector switch

Check for worn out contacts. Filter oil

irrespective of all test. Replace worn out

parts.

1 Oil conservator Internal inspection Clean the conservator

thoroughly

Two years

-

2 Buchholtz relay Mechanical inspection. Adjust floats,

switches etc. if required.

3 years or

after

15,000

operations

1

Non-arcing selection switch

of on load tap changer

General inspection. Replace worn out parts

and filter the oil.

7 to 10

years

1

Overall inspection including lifting of core

and coils

Major overhauls (complete) of

transformers.

Once in 7 years

once in 10 years.

1 3000KVA and below (once in 7 yrs.)

Above 3000KVA (once in 10 yrs.)

Yearly

R&M Final 2 5/12/2006 10:50 AM A-7

Schedule for the R & M of Isolators and Earth Switches.


inspected


1

Insulators

Check for cracked or broken porcelain and

excessive dirt film and to undertake repair of

chipped spots by painting with lacquer such as red

clay paint.

2 Blades and

contacts

Check that blades are properly seated in the

contacts..

3 Blades and

latches and

stops

Check that blade latches where provided are

engaged. Weekly

4 Locks and

inter locks

Check that switches are properly locked in the

open or closed position as required by padlocks or

other key type locks or interlocks.

Quarterly 1 Bolts, Nuts &

Jumpers

Check bolts, nuts and jumpers for tightness.

Apply petroleum jelly on male and female contacts.

1 I.R,value and

earth

resistance

Check IR, value with 2.5KV megger and earth

resistance. Check that double earthing is provided.

2 Auxiliary &

limit switches

Check condition of contacts and refinish with fine

file if burnt or corroded. Check contact spring

operating rod and lever. Check closing and opening

position with respect to main switch contacts or

travel or motor mechanism.

Half yearly

3 Manual

operating Rod

To check for proper engagement of emergency

operating handle and further its operation is

smooth and satisfactory.

1 Line & ground Check and tighten line and bus terminal and

operating handle ground connections. Check that

ground cable is not broken.

Annually

2 Blades and

contacts

Operate the isolator several times and see that

the blades are properly aligned to engage.

R&M Final 2 5/12/2006 10:50 AM A-8

Schedule for the R & M of CURRENT/POTENTIAL T/F


inspected


1 Insulator Check for any crack or damage of the porcelain

insulator.

2 Oil Check for oil leakage and oil level

3 Earth

connections

Check that earth connections are properly made

4 Jumpers Nut

Bolts etc.

Check that jumpers, nuts, bolts, clamps are

properly tight and are of proper size.

Monthly

5 Secondary

winding

Check that secondary winding terminal wiring is

properly made and routing is not disturbed. The

connections in the panel are intact.

1 I.R.Value Check I.R.values of primary and secondary

windings with 2.5KV & 500 V rating meggar

respectively.

2 Earth

resistance

Check earth resistance.

Half yearly

3 Secondary

taps

Check secondary taps for tightness to avoid

overheating.

1 Oil test Check dielectric strength of oil and toping of oil.

Yearly

2 Tap setting Check tap setting and adjustment at terminal

beard to see that they agree with diagrams.

R&M Final 2 5/12/2006 10:50 AM A-9

Schedule for the R & M of Lightening Arrestors.


inspected

Brief description of work Daily

1

Surge Counter Note and record operation indicator reading

alongwith leakage current.

1 Base & support Usual inspection to detect cracking setting or

shifting of base of supports.

Monthly

2 Surge Monitor Check that surge monitor is properly connected

and is in working order and shows a leakage

current.

1 Jumpers and

clamps

Check jumpers and clamps for tightness.

2 Porcelain

shells and

insulators

Clean porcelain insulators and arrestor unit shells.

Repair chipped spots on porcelain with lacquer

such as red clay paint.

3 Grading rings Check and tighten grading rings on high voltage

arrestors.

Half Yearly

4 Gaps Check external gaps. Smooth off burnt spots and

readjust spacing.

1 Weather

sheds and

hooks

See that weather sheds and hooks of oxide film

arrestors are securely fastened in place, repaint if

necessary.

2 Line and

Ground

connection

Check and tighten line and ground connections.

Check ground lead for corrosion or damage below

ground line. Check ground resistance. See that all

leads are as short and direct as possible.

Annual

3 Operation

tests (Surge

generating

equipment

under

procurement)

To check the general working of lightening

arrestors by M&P Divisions.

R&M Final 2 5/12/2006 10:50 AM A-10

Schedule for the R & M of Batteries and Battery Charger.


inspected


1 Battery room

and ventilation

See that battery room entrance doors are kept

closed and that ventilation to out side air are open

and air is circulated by running of the exhaust fan.

2 Operation Check charging rate hourly. Check and record pilot

cell specific gravity, temperature and floating

voltage.

3 Bulb for dry

rectifier

element

Check for burnt bulb and replace when necessary.

Daily

4 Operations Checking specific gravity and voltage of each cell

of lead acid cells. (before and after charging)

(weekly when trickle charge exists)

Daily(

each

shift)

1 Leakage test Perform leakage test by lamp or voltmeter

method.

Wee

kly 1 Cleaning of terminals, applying Vaseline and topping

up with distilled water. (for lead acid batteries)

1 Cell Jars and

covers

Check for cracked or leaking jars or covers and

replace when necessary. Keep jars and covers

clean.

2 Plates Inspect plates(in case of transparent containers

only) carefully for signs of deterioration due to

improper charging. Note quantity, colour and

texture of sediment.

3 Separators See that the separators remain in place and are

keeping the plates properly spaced(in case of

transparent containers only)

4 Electrolyte Check electrolyte level and add distilled water

when required.

5 Acid and

distilled water

storage

See that enough distilled water and acid are kept

in storage to meet current needs. Check

containers for cleanliness.

6 Operation Check and record specific gravity and voltage of

each cell.

Monthly

7 Transformer

or reactor

Check general condition and operating temperature

of transformer or reactor used in bulb or dry type

rectifiers.

R&M Final 2 5/12/2006 10:50 AM A-11


inspected


Quar

terly

1 Connections Checking all connections of charger and battery

for tightness.

1 Discharging

and charging

cycle

This is required to be carried out as prescribed by

the manufacturer in order to prolong the life of

the battery.

2 Bulb or dry

rectifier

element

See the copper oxide or selenium rectifier

elements are not operating too hot, this will

shorten their life. Half yearly

3 Rheostat Check that sliding mechanism of the rheostat is in

order and clean the sliding contacts, if required.

Check contact heating and spring pressure.

1 Battery room

and ventilation

Check metallic structures/parts located in the

room for corrosion and clean and paint as

necessary, check ventilation system fan etc. for

proper operation to make sure that no explosive

gases are being accumulated in the battery room

due to excessive gassing or poor ventilation.

2 Base or rack Inspect concretes base or wooden racks for

deterioration. Repair and repaint with acid

resistant paint as necessary.

3 Case pad Check base pad of sheet rubber, or other material

for deterioration from acid or other causes.

4 Inter cell

connectors

and terminals

Clean acid corrosion from connectors and

terminals should be lead coated. Tighten terminals

and apply petroleum jelly for exposed surface.

5 Hydrometer

and thermo

meter

Check condition of hydrometer and thermometers

used for daily and monthly readings against spare

units held in reserve.

6 Sink funnel

and filters

See that the sink, funnels, fillers and other

distilled water and acid handling facilities kept

clean and in good useable conditions.

7 Water still Check still for proper operation, adequacy and

purity of distilled water delivered. See that

equipment is kept clean

Annual

8 Complete overhauling of the battery. (as

recommended by manufacturer)

R&M Final 2 5/12/2006 10:50 AM A-12

Schedule for the R & M of Oil and Air Circuit Breakers.


inspected


1 General

cleanliness

Examine that switchgear premises doors, circuit

breaker etc. for general cleanliness.

2 Oil Check oil leakage, if so level be also ascertained.

3 Tank Check for temperature by touch and for any

unusual noise and smell.

4 Alarms and

lamp indication

circuit etc.

Test the alarm circuit for continuity and lighting

circuit and earthing system.

5 Draining and blowing down of main air receivers,

checking all air pressures and air conditioning flow

meters.

6 Safety aids Check safety aids for proper operation/condition.

7 Load Check for load conditions on 3 phases, adjust relay

setting. If necessary.

Daily

8 Indicating and

measuring

instruments

Check, indicating and measuring instruments for

correct reading and being in proper working order.

1 Auxiliary

fuses

Check that auxiliary fuses are in tact.

2 Oil level and

gauges

Check oil level in gauges of the tank/poles/oil

filled bushing. Replenish oil if found below normal.

3 Bushing or

insulators

Check for chipped or broken insulator, excessive

dirt film.

4 Closing

solenoid of air

cylinder,

motor or

spring

Visual inspection to see that equipment is in

operating conditions Drain condensation from air

cylinder.

5 Latch and trip

mechanism

Visual(or otherwise)inspection to see that

mechanism is in operating condition.

6 Tripping

solenoid

Visual inspection to see that solenoid trip device is

in operating condition.

Weekly

7 Cabinet lights

and heaters

Check cabinet heaters and see that they are in

service during cold weather. Replace burnt out

lamps.

R&M Final 2 5/12/2006 10:50 AM A-13


inspected


8 Power supplies

and wiring

See that all power control circuit switches are

closed

9 Breathers and

vents

Check for external obstructions to breathers and

vents and condition of silica gel.

1 Nuts, bolts &

Jumpers etc.

Check whether nuts and bolts are tight and

jumpers are properly connected.

2 Drain plug Check that drain plug is tight.

Monthly

3 Operation

counter

Observe and record reading of operation counter.

1 Local remote

operation

Check that breaker can be operated locally and in

remote control operation.

2 Exhaust pipes Check and clean the exhaust pipes.

3 Dash pot Check the working of dash pot.

4 Shutter

mechanism and

trolley

alignment for

11KV breakers

To check for proper working of shutter mechanism

and to verify the alignment of trolley.

5

Manual

operating

device

Check that manual operating lever or jack is kept

on hand and is in visible condition. See that

breaker is closable with it.

6 Latch and trip

mechanism

Observe mechanism during general tripping

operations to see that every thing is in working

order. Check pins, bearings and latch for wear,

binding and misalignment. Clean and lubricate the

moving parts. Check latch carefully to see that it

is not becoming worn so as to unlatch from

vibration or stick or fail to trip. Tighten bolts and

screws.

7 Tripping

solenoid

Observe operation during electrical tripping. See

that full energy, snappy action of plunger is

obtained. Check plunger for sticking in guide Check

oil and insulation resistance.

Quarterly

8

Check and adjust oil level in jacks.

Weekly

R&M Final 2 5/12/2006 10:50 AM A-14


inspected


9 Indicating and

measuring

instruments

Check for satisfactory operation, adjust where

necessary

1 IR values Check IR value in ON and OFF positions between

contacts in off position. Check IR value of control

cable with 500V megger.

2 Earth

resistance

Check earth resistance of body.

3 Slow closing

test

This test may be conducted and also check that all

the three contacts are made simultaneously.

4 Adjustment of

gap (for

MOCB)& other

type to check

the prescribed

items by the

manufacturer

The gap may be checked and adjusted to the

required value.

5 Wiring

connections

Check and tighten wiring connection at terminal

points. Inspect wiring for open circuit, short

circuit and damaged insulation.

6 Aux.Switches Check condition of contacts and refinish with fine

file if burnt or corroded. Check contact springs,

operating rods and levers. Check closing and

operating position with respect to main contacts

while breaker is slowly closed and opened manually.

7 Control and

protection

chamber of

11KV switch

To check for alignment of front door

opening/closing for loose fitting, loose wiring of

opening in 11KV switchgear.

8 Insulated,

jumpers CT

and PT in 11KV

switchgear

To check for tightness of connections, proper

insulation and proper geometry.

Half yearly

9 11KV cable

connections

Check for overheating and proper connection and

insulation.

Quarte

rly

R&M Final 2 5/12/2006 10:50 AM A-15


inspected


1 Foundation Check foundation for cracks and settings.

Settings of the breaker tank may break bushings

or cause misalignment of contacts or bindings of

operating mechanism.

2 Oil valves and

plugs

Check condition of paint. Inspect oil valves and

plugs. Flush out oil and clean the oil

tank/quenching chambers.

3 Oil levels and

gauges

Clean dirty gauge glasses and connections into

tank. Drain out and replace bushing oil if found

dirty or discoloured.

4 Breathers and

Vents

Check to see that screens and baffles in vents or

breathers are not obstructed or broken.

5 Panels and

cabinets

Check air circuit breaker or other panels of

insulating material for cracks and cleanliness.

Check condition of enclosing cabinets including

hinges, latches, locks door gaskets and paint.

6 Bushings or

insulators

Clean porcelain with water, chloroethene or other

suitable cleaner. Repair chipped spots by painting

with lacquer such as red clay paint. Inspect

gaskets for leaks, tighten bolts. Check insulation

resistance with contacts closed and (Tan delta for

condenser type). Check oil sample from bottom of

bushing for dielectric strength and moisture.

Replace or replenish oil if necessary. Check and

clean interior at least once every five years.

7 Main terminals

and ground

connections

Tighten all nuts and ground connections. Refinish

joint mating surface, if they have been

overheated. Inspect ground cable to see that it is

not loose or broken.

8 Main contacts Remove the tanks or drain out oil, so that the

contacts can be inspected, dress contacts, if

rough with a fine file. Check contacts voltage drop

with millivolt meter after inspecting reasonable

current. Frequency of contact maintenance should

be based on numbers and severity of faults

interrupted, rather than a definite period. Check

adjustment of gap when required.

Annual

9 Contact

pressure

spring

Check for loss of temperature damage or other

deterioration.

R&M Final 2 5/12/2006 10:50 AM A-16


inspected


10 Flexible shunt Check flexible shunts of contact hinges for

overheating or damages. Tighten connections.

11 Magnetic, air

or oil below

out devices

Check arc-rupturing blow out coils, magnetic

cirlcuit arc chutes, de ion grids, oil blasts or other

interrupters for proper operations.

12 Cross heads Check contact cross head for misalignment breaks

bends or looseness on lift rods.

13 Lift rods and

guides

Check contacts for lift rods or brakes, weakening

or wrapping and pulling out at ends. Checks

adequacy of guides.

14 Operating

rods shafts

and bell cranks

Check for loose locknuts, set screws, keys, bearing

bent rods or twisted shafts etc. clean moving

parts of rust, dirt and accumulated grease and oil,

wash out bearings, pivots and gears with

chloreethene or other suitable cleaner and

operate breaker several times to work out dirt and

old lubricant. Lubricate with new grease or oil.

15 Closing

solenoid air

cylinder,

meter or

spring

Observe mechanism during several operations to

see that every thing is in proper working order.

Check solenoid plunger for sticking in guides.

Check coil resistance and insulation resistance.

Dismantle air cylinder and clean and lubricate.

Check spring for proper tension and closing energy.

16 Solenoid

valves

Check for condition of valve, and refit as

necessary. See that moving parts are free to

operate. Check resistance and insulation

resistance of solenoid coil.

17 Operation

counter

Check that the operation counter is properly

registering the breaker operations.

18 Position

indicator

Check that position indicator is properly

registering the breaker operations.

19 Dashpots Check for proper setting and adjust as necessary.

Clean out and replenish liquid in liquid dashpot.

20 Mechanism

cabinets

Check condition of metal and hardware. Repaint as

necessary. See that door gaskets are tight and

properly dust and vermin proof.

Annual

21 Power supply

and wiring

Inspect fuses of circuit breakers in all power and

control supply circuits, check in insulation

resistance of wiring with devices connected.

R&M Final 2 5/12/2006 10:50 AM A-17


inspected


22 Oil dielectric

test and

acidity test

dependent on

actual tripping

Check dielectric strength of the insulating oil in

the main tanks and oil filled bushings. Oil should

be filtered or replaced if dielectric strength is

found to below 25 KV, or if there is a noticeable

amount of carbon in suspension on the bottom of

the tanks. Also check ratio and phase angle

adjustments, the acidity of the oil.

23 Operation Some breakers particularly those carrying high

values of current have a tendency to develop

contact heating if left closed for long periods.

Operating and closing the breakers several times

at intervals, as system operation permit, may

alleviate the heating by wiping the oxide from the

contact surfaces, as well as demonstrate that the

breaker is in operating condition.

24 Bushing

current

transformers

and potential

devices

Check tap setting and adjustments at terminal

board to see that they agree with diagrams. Check

insulations resistance of wiring with devices

connected. Check of potential devices if changes

have been made in secondary connection and

burden. Tighten connections, including potential

devices top into bushing.

1 Testing of oil in oil filled bushings

2 Cleaning blast tube intemally and checking clamping

down nuts.

Once in two

years

3 Overhaul and checking efficiency of main

compressor.

Five yearly

1 Complete overhaul of the O.C.B.

(The period can be changed depending upon the lead

cycle of the equipment and manufactures

recommendations).

Annually

R&M Final 2 5/12/2006 10:50 AM A-18

Schedule for the R & M of H.T. Lines (33 KV & 11 KV including G.O. Switches)


inspected


1 Poles

i) Steel

ii) Wood

iii) Cement

Check for the following in case of all the 3 types of

poles:

i) Damages/broken poles or for ground level

erosion and corrosions where the pole is not

capable of safely supporting its load.

ii) Bowed or leaning poles due to improper guying

or overloading.

iii) Unauthorized attachments such as fencing,

aerial wires etc.

iv) Poles which are very much exposed to

hitting/striking of animals and bumping and

scrapping by vehicles

v) If the pole Number plate is still distinct

vi) Check the condition of foundation and attend

it, if necessary.

vii) Examine if pole requires painting/creeseting

of ascue in case of steel/wood poles.

2 Stays Check for the following:

i) Correct direction and proper angle of the stay

ii) Loose broken or any other damage done to

stays

iii) Whether stay insulator is intact/whether stay

is properly earthed

iv) If stay rods are corroded. Attend the same

if required.

Quarterly

3 Cross arms and

pole top steel

works

Check for the following:

i) If the cross-arms/clamps/knee bracings

has/have slipped.

ii) Bending of cross arms due to uneven tension

iii) Excessive rusting of the cross arms bracings

etc.

iv) Cracked or splitting or the wooden cross-

arms.

v) Loose or damaged bracings. Attend the same,

if required.

R&M Final 2 5/12/2006 10:50 AM A-19


inspected


4 Insulators and

fittings


i) Broken or chipped procelain flashover marks

ii) Tilted insulators

iii) Excessive deposit of dust/salt/coal and other

pollution clean the same.

Excessive rusting of fittings, replace the same, if

required.

Quarterly

R&M Final 2 5/12/2006 10:50 AM A-20


inspected


5 Conductors and

earthwire


i) Examine, if securely tied to the

insulator/pole/cross-arms.

ii) Proper sag, set right the same, if required.

iii) Proximity of trees and other objects including

building etc.

iv) Sufficient clearance between conductors and

earthwire and also from the ground.

v) Sufficient clearance from other

electric/telephone lines passing along below or

above it.

vi) Earthwire is properly supported

vii) All the line guards are intact and installed

where necessary

viii) If joints in the jumpers and conductors

appear all right

ix) Broken conductors strands

x) Nicking near insulator neck/or near conductor

clamps

xi) Bindings wire has not become lose and open

xii) Midspan joints have not cracked.

xiii) All joints and jumpers of aluminum conductors

have proper clamps/jointing sleeves. Setright

the same, if required.

Quarterly

6 Jumpers and

other line

accessories


i) Proper supporting and jointing two ends of the

jumpers with suitable clamps.

ii) Sufficient clearance between jumpers on the

3-phases

iii) Sufficient clearance of jumpers from metal

iv) Provision of proper insulation of jumpers

v) Signs of over-heating and burnings on jumpers

and other fittings.

vi) Loose/defective clamps jointing sleeves, bolts

and nuts, and other fittings.

R&M Final 2 5/12/2006 10:50 AM A-21


inspected


7 GO switches Check for the following:

i) For smooth operation

ii) Evidence of over-heating burning,

crossing/pitting on the switch contacts.

iii) Broken on damaged insulators

iv) Proper and tight earth connection

v) Fuse links for continuity, tightness of

connections and correct rating

vi) Proper locking arrangement

vii) Proper alignment of switch contacts

viii) Proper and complete fitting of male contacts

into the female one.

ix) Arcing horns are intact. Attend the same,

wherever reauired.

8 Lightening

arrestors


i) Broken/damaged porcelain

ii) Broken and tight. Line and earth connections

iii) External indication of fused/spark-over

arrestors

9 11KV cable and

cable box


i) Proper supporting of the cable and cable

boxes

ii) Damaged insulators

iii) Oil and compound leaks and that the cable box

is properly topped up with the compound

iv) Proper earthing

v) Overall condition of the cable and joint.

Quarterly

10 Earthing

system

Check for tight and intact earth connections for all

metal works of the line.

R&M Final 2 5/12/2006 10:50 AM A-22


inspected


Half yearly

1 Jumpers and

line

accessories

i) Check for broken or burnt strands of the

jumpers and replace, where necessary.

ii) Check for proper material and size of the

jumpers for the given conductors.

iii) Check for loose connections and signs of over-

heating specially on copper to alumimium

connections

iv) Check for crewaing or jumbling of wires and

jumpers of the Tee-off points and adjust

where necessary.

v) Check for general condition of other line

accessories such as different clamps, jointing

sleeves and other fittings etc. Readjust and

replace where necessary.

vi) Replace the binding wire joints of jumpers by

proper clamps.

vii) Check for the condition of sleeves over the

jumpers and replace, where necessary.

R&M Final 2 5/12/2006 10:50 AM A-23


inspected


2 G.O.

switch(with

fuse unit)

i) Cleanliness: clean all dust and other deposits

with neat and dry cloths.

ii) Switch contacts:

1. Check for alignment, adequate contact

pressure and smooth operation and adjust,

where necessary

2. Examine for burning,over-heating or other

damages. Recondition or replace, where

necessary.

iii) Insulator:

1. Check for cracks. Clipping and other

defects, replace, where necessary.

2. Remove dirt, coal and other pollutions by

wiping with soft cloth. Use acidic solution,

if the deposit has set hard.

iv) Arcing horns: Check if these are intact and

replace if damaged/burnt.

Mechanism: clean, examine and renew worn out

parts. Reduplicate and check for correct operation.

vi) Fuse unit: replace old fuses with new ones of

right type and capacity and proper length

vii) Main connections and Earthing: Proceed as

described under separate heading of jumpers and

earthing devices.

viii) General: Check all hardware and tighten, if

needed

Half- Yearly

R&M Final 2 5/12/2006 10:50 AM A-24


inspected


Half Yearly

3 Tree trimming

and bird's

nests etc.

i) Cut off the trees branches where necessary

to maintain a minimum clearance of 1.8m on

each side of the line

ii) Remove all dead wood.

iii) Remove all bird's nests.

(once before the monsoons or earlier, if necessary)

Annually

1 Poles

1) Steel

2) Wood

3) Cement

The instructions given below are concerned to the 3

types of poles:

i) Replace the damaged/broken poles.

ii) Straighten/make vertically leaning poles by

proper giving

iii) Shift the position of poles exposed to

accidents due to their being near or in

common way.

iv) Reprint the pole No.plate , if defaced

v) Pack and consolidate the foundation soil where

disturbed or erased

vi) Steel poles: Examine for signs of rust, clean

off with wire brush and apply double coat of

suitable paint, where required over a primer

base.

vii) Wood pole:

1. Examine for decay of wood and

creosetting/ascuer treatment may be

done where required.

2. Examine for burning of wood at hardware

attachments points and recondition, where

necessary.

viii) Cement Pole: No. detailed maintenance

required.

R&M Final 2 5/12/2006 10:50 AM A-25


inspected


2 Stays i) Tighten the loose stays.

ii) Replace the broken/damaged stays and stay

bows

iii) Replace the broken stay

insulator/recondition the Earth

iv) Provide sufficient barbed wire/cattle guards

on the stay to avoid rubbing of cattles

3 Cross arms i) Replace the broken/splitted/cracked/bent

cross arms by new ones.

ii) Bring in position the slipped cross

arms/clamps/bracings.

iii) Paint the steel cross arms and bracings etc. If

excessively rusted.

Annually

R&M Final 2 5/12/2006 10:50 AM A-26


inspected


4 Insulators and

fittings

i) Clean and check for cracked/chipped and

punctured insulators. Replace, where

necessary.

ii) Examine for the surface contamination and

remove it by wiping with a soft cloth (do not

use cotton waste). If the deposit has set

hard, a weak acidic solution may be used.

The insulators be checked twice a year preferably

or before and after (monsoons)

5 Conductors and

earthwires

i) Tighten loose bindings and replace damaged

ones.

ii) Examine for corrosion at the joints of

conductors and insulators. Clean and renew,

where necessary.

iii) Examine closely for broken strands

particularly at the clamps and insulators due

to vibration and repair, where necessary.

iv) Examine general condition of the conductor

and earthwires i.e. for kinks, crushed spots

over/under tensioning, etc., and recondition,

where necessary.

v) Examine for any loose/cracked joints of

conductors in the midspan and recondition

where necessary.

vi) Examine for any loose/cracked joints slipping

of conductors from the clamps. Tighten all

clamps and fittings.

Annually

6 Lightening

arrestor

i) Clean and examine insulators for cracks or

flashover. Replace, where necessary.

ii) Perform impulse voltage spark over test and

leakage current test to know the condition of

the arrester; replace in case of

unsatisfactory results.

iii) Keep records of test results.

iv) Check and tighten all line connections and

earth leads.

R&M Final 2 5/12/2006 10:50 AM A-27


inspected


7 11KV cable and

cable boxes

i) Clean and examine for damaged bushings.

ii) Check for compound level, if there is leakage.

iii) Perform insulation resistance test,

recondition or replace, where necessary.

iv) Keep continuous records of insulation

resistance.

8 Earthing

System

Replace all broken earth leads and tighten others.

Measure earth resistance of various earths with

earth. Tester. In case of low values, recondition

them.

9 Anti-climbing

devices and

danger plates

etc.

Recondition the anti-climbing devices such as barbed

wire, locks, etc., paint and reprint the danger plated

if defaced.

Annually

R&M Final 2 5/12/2006 10:50 AM A-28

Schedule for the R & M of L.T. Line


inspected

Brief description of work Four Monthly 1 Poles stays

Cross-arm

conductors

Insulator

Connectors

Cable boxes

etc.

Same as recommended for these items under

schedule of H.T. Lines (Whether cobwebs, kite

strings etc., hanging on the conductor.

M onthly

2 L.T.Switch Check for the following:

i) If the switch with cover is intact.

ii) If the cable/switch running hot.

iii) Broken cut-outs.

iv) Signs of over-heating/burning on contacts.

v) Proper size of fuse wire.

vi) Safety from rain water etc.

Half Yearly

3 L.T.Switch i) Check lead on the L.T. circuit and replace

the L.T. cable/L.T. switch by higher

capacity one, where necessary.

ii) Replace the damaged L,T.cable with new one

of right capacity.

iii) Examine the switch for smooth operation.

iv) Replace the burnt/cracked cut-outs.

v) Recondition the switch contacts.

vi) Replace the old fuses with new ones of right

capacity.

vii) Tighten all connections.

viii) Ensure that the inlet of the cable into the

switch is plugged with plastic compound to

avoid entry of rain water. Refill, where

necessary.

ix) Clean off the cob web and other nests, etc.,

from the inside of the switch.

R&M Final 2 5/12/2006 10:50 AM A-29


inspected


One to two-yearly

4 (a) Poles

(b) Stays

(c) Cross-

arms

(d) Conductor

(e) Insulator

(f) Connector

(g) Cable

boxes etc.

Same as recommended for these items under

Schedule for H.T.Lines.

schedule for the r & m of distribution transformers

Documents