3. 3
Unsafe Action By Personnel Causing
Accidents
• Carelessness in job.
• Half knowledge (half-baked) of work
• Tension (Anger) on duty
• Ineffective supervision
• Absence of supervision
• Non-planning before commencing work
• Non-cooperation bet personal
• “I know it all” Attitude (Ego)
4. 4
General Cause Of Accident
• Unsafe action of personnel
• Unsafe status in distribution
5. 5
Unsafe status in distribution
• Snapping of conductor.
• Stay w/o guy shackle becomes live.
• Steel pole w/o proper earthing.
• Damaged pole falling down
• Inadequate ground clearance
• Leaning poles
6. 6
Reason for snapping of conductor
• Line with copper connected to Aluminum conductor
• Due to falling of trees
• L.T.Shackle without metal parts
7. 7
Unsafe Action By Personnel Causing
Accidents
• Non- adoption of safety procedures
• Not exercising with the safety device- gloves, Earth
rod, Waist-belt etc.
• Over confidence
• Drunkenness on duty
• Performing work in disturbed mind
• Hurry in finishing job
• Ignorance (unawareness) of work
9. 9
SODA ACID (9L)
The extinguishers should be taken within 1M offire.
After taking out the safety cup, the extinguisher
should be held and plunger struck against a hard
surface. Now the acid bottle will get broken and
acid on mixing with solution will evolve
carboridioxide gas. The gas pressure will expel
water when cylinder kept inverted. The expelled
water should be directed to the base of the fire.
Upright type; as having discharge tube inside from
nozzle to bottom, should not be used in inverted
position.
10. 10
FOAM TYPE (9L)
The knob should be pulled up, turned clockwise and
pin seated on the groove. This will keep the port of
inner container open and when the-cylinder kept
inverted the two solutions mix together forming
foam. The evolved CO2 gas will expel the foam. The
foam has to be directed on to the fire without force
to cover as a blanket covering the fire. This
prevents entry of oxygen thereby extinguishing fire.
For effective formation of foam the cylinder may be
alternatively kept shaking upright and inverted
quickly 2 to 3 times.
11. 11
DRY CHEMICAL POWDER (DCP)
Remove the safety clip and strike the plunger. The
pin in the plunger will puncture the seal of the co2
cartridge and the gas coming out with pressure will
stir the powder and expel the powder. The powder
coming out through the hose should be directed on
to the fire show as to cover the fire as a blanket and
extinguish the fire.
12. 12
CARBONDIOXIDE CYLINDER
The extinguisher should be taken every close to the
fire. After opening the cylinder value, the gas
coming thro the hose and can may be directed on
to the fire. The gas coming out through the hose
will expand and cover the fire as a shroud and
extinguish the fire.
13. 13
General Precautions
1. The lids of all extinguishers should be checked for tightness. If two
or more threads are exposed out that cylinder should not be used.
The high pressure developed in the cylinder could be withstood only
if the lid is completely screwed on to the body. Other wise the lid
would come out as a blast and cause serious injury to the operator.
2. All extinguishers should be used in the direction of the wind.
3. There are three pin holes on the periphery of the lid. When there
is any block in the cylinder. Nozzle or hose the contents will not come
out while using. Then the cylinder lid may be unscrewed very slowly.
When the holes come up, the pressurized gases will come out thro’
these holes. Only after the gas completely goes out. The lid can be
fully opened. On no account we should think that there is no
pressure inside the cylinder, if contents do not come out during
usage.
4. whenever newly filled, the gas cartridge and CO2 cylinder should
be checked for its correct weight.
14. 14
MAINTENANCE OF EXTINGUISHER
• Monthly cleaning and checking for nozzle block and lid
tightness.
• Quarterly open the lid. Check for free 11; movement of
plunger. Clean the outside of the inner container.
• In foam type the solution should be poured separately in
utensils and stirred. Few drops may be taken out separately
and mixed together for checking proper formation of white
colored foam.
• Once in 6 months the gas cartridge should be checked for
weight. If there is more than 10% loss in weight of gas, the
cylinder may be used in fire mock drill antler refilled.
• Once in two years the cylinder should be checked for pressure
test. Soda acid and foam type should withstand pressure of
17.5 Kg/Sq.cm. for 2.5 minutes.
• All fire extinguishers should be checked for healthiness Once
in a year.
15. 15
Introduction to Substation and
equipments
• In Power System network, in order to transmit and distribute
the generated power, it is necessary to install “SUBSTATIONS”
at strategic points to work at required voltage level since
“HIGH VOLTAGE TRANSMISSION” is resorted to. The Sub
stations are classified as “GRID” or “RADIAL” Substations. The
Grid station is installed in Grid network to reduce the voltage
level from 230KV to 110 KV. The radial Station with in
Distribution net work to reduce the voltage from 110 KV to
11KV or 22KV or 33KV).
• In essence the substation provides
• (a) Transfer of voltage level
• (b) Transmission of the required Power and
• (c) Adjustment of voltage variations caused by the system
voltage regulation.
16. 16
110/11KV SUB STATION :
CLASSIFICATION OF EQUIPMENTS
• Sl. No Classification Equipments Purpose
• 1. Functional
• a) Bus Bar
• b) Transformers
• c) Earthing System To carry Power feeding To
transmit Power from one voltage to other To ensure
effective grounding for safety & Protective
operation.
17. 17
110/11KV SUB STATION :
CLASSIFICATION OF EQUIPMENTS
• 2. Isolation & Control
• a) Isolation
• b) Breakers Isolate feeding equipments from source
of supply (Potential ) Breaking the Current (Power
flow) for normal maintenance; and for isolation of
faulty section)
18. 18
110/11KV SUB STATION :
CLASSIFICATION OF EQUIPMENTS
• 3. Protection from internal disturbances
• a) Earth Mast
• b) Surge Diverter
• c) ROD GAP To prevent damage to equipment from
direct stroke of lightning. Protecting the transformer
from the impact of surges. Back up Protection for
Surge Diverters.
19. 19
110/11KV SUB STATION :
CLASSIFICATION OF EQUIPMENTS
• 4. Protection & Metering
• a) Potential Transformer (PT)
• b) Current Transformer (CT)
• c) Relays Metering (Voltage and Energy) Metering
(Current & Energy) Protection For sensing the fault
and give command to breakers to isolate the faulty
circuit. For
• i) Indication of Status
• ii) Annunciation of the fault
• iii) Operation of breaker for isolation of faulty
circuit.
20. 20
110/11KV SUB STATION :
CLASSIFICATION OF EQUIPMENTS
5. A.C.System for LT 3phase, 400V supply
a) Station Transformer 11KV/400V.
b) b) A.C.Panel To feed L.T-3Ph. 400V Supply for
c) i) Auxiliaries of breakers & Transformers.
d) ii) Yard & Control room lighting
e) iii) Supply to battery charge Control of A.C.Supply
21. 21
110/11KV SUB STATION :
CLASSIFICATION OF EQUIPMENTS
6. Housing
a) Yard & Structures
b) Control room To house equipments with required
horizontal and vertical clearances. To house indoor
equipments like D.C. System, D.C. & A.C. panels
etc.,
22. 22
LAYOUT OF SUBSTATION
• A single line diagram called the Schematic layout of Sub-
Station should be available, showing the arrangement of the
above equipments.
• A typical layout of a 230 / 110KV Grid station and that a
110/11KV Radial station are shown in Fig. 1 & 2 below.
• Based on this single line diagram detailed Electrical layout,
drawn to scale showing the Plan and Elevation of the Sub
Station arrangement is prepared.
• A civil layout for the lands acquired for the installation of the
substation will also be prepared, wherein the Electrical layout
will be incorporated in the specified location, showing, Road,
control room, Quarters and other civil amenities.
• In this detailed Electrical layout, the required clearances,
Height of structures, space occupied by equipments etc., will
be clearly marked so that the Erection Engineer will carryout
erection works and installation of equipments accordingly.
26. 26
FUNCTIONAL EQUIPMENTS
• BUS BARS
• The Purpose of bus bar is to receive the Power and
feed to the concerned equipments. Types : Strung
Bus & Regid Bus
• Strung Bus : The Conductor (ACSR) Strung
between the two ends of Sub Station through Disc.
insulators and Gripper sets.
• Regid Bus : Aluminum tubes erected and
Pedestal insulators over pedestal support structure.
28. 28
BUS BARS
• Points:
• The Main Bus will be of strung bus and the feeding
arrangement to equipments will be Regid bus.
• The insulators should be cleaned and checked for
any breakage, cracks and to be replaced.
• Since the bus bars are heavy current carrying
parts, tightness of the clamps to be checked and
avoid glow.
• The Pedestal Insulators may be Polycone insulator
for 110KV and above and post type insulators 33 KV
and below.
29. 29
POWER TRANSFORMER
• This is the Main Equipment of Substation.
The Purpose of Transformer is Transmission of
Power from one voltage level to the other required
voltage level, with negligible losses.
• Reduction to the required voltage level.
• The drop in voltage in the system is compensated
by tapings.
31. 31
INTERNAL ACCESSORIES
• The transformer mainly comprises of Magnetic core
and windings wounded for the 3 phase. Each phase
will have a Primary and Secondary winding, wound
according to the voltage for which it is put into use.
The core and winding Units are placed in a Main
tank and filled with Transformer oil.
• The transformer oil is for insulation and cooling
purpose.
• The leads from the winding are brought out through
the bushings for external system connections.
• The three phase windings on Primary will be
connected in DELTA & the Secondary in Star as
shown below:
35. 35
EXTERNAL ACCESSORIES
• Main tank with value & cooling arrangement
• Bushings with C.Ts.
• Conservator
• Tap switch
• Air release Plug
• Equalizer pipe
• Explosive vent
• Temperature indicators
• Breather
• Buchholz relay
38. 38
Item of Inspection or Maintenance
• Checking for unusual noise
• Checking oil level in the conservator and bushings
• Cleaning of bushings
• Inspection and cleaning of breather.
• Reconditioning or replacement of silica gel .
• Examination of relief diaphragms to ensure that they are not
cracked or broken
• Checking up or temperature alarm for correct operation
• Measuring insulation resistance of windings
• Testing of oil from tank and conservator for dielectric strength
on all transformer.
• Checking up gap settings on bushings of transformer horn
gaps
• Testing of transformer oil for acidity
• Testing of oil in oil filled bushing of dielectric strength and
acidity
39. 39
periodical maintenance
• The following periodical maintenance are recommended for
Power Transformers:
• Annual inspection and maintenance of power transformer
should be carried out thoroughly.
• The following should be checked.
Operation of Buchholz relay by pumping air.
Oil level in the conservator tank using a dip stick.
Check for any cracks is the foundation.
Tightening of all loose bolts and nuts.
Measuring rod gap.
Release of air in tank and bushings.
Polarization index value test with power operated megger.
Checking the stop block in the rail.
Check relief diaphragm.
Clean Bushings
40. 40
periodical maintenance
• Calibrate temperature indicators and check up operation if
temperature alarms and trips.
Lubricate all moving parts in on load tap changer mechanism.
Check and tighten all connections.
Check the resistance of the transformer windings.
Recording Insulation values of winding by meggering with
1000 Volts Power megger, after removing neutral Earth
connection – HV to Earth, LV to Earth and HV to LV and check
the continuity of winding.
• Oil sample testing : Dielectric strength, Acidity content of oil is
to be tested. In addition , the other tests conducted are
• a) Resistivity
• b) Interfacial tension
• c) tan delta
• d) Dissolved gas analysis (DGA)
41. 41
EARTHING SYSTEM
• The Solidly grounded system ensures speedy & accurate
sensitive of fault and isolate the faulty section. Neutral of
Transformer secondary is grounded All other metallic parts
associated with Electrical equipments should be grounded.
• Surge diverter should be grounded. Double Earthings should
be ensured for each grounding All the groundings should be
interconnected.
• The Earthing system comprises of
1) Earth conductor,
2) Earth connection,
3) Earth Pipe,
4) Earth pit and
5) Earth interconnection.
43. 43
EARTH INTER CONNECTION
In order to interlink all the individual Earth
Electrodes, it is in practice to lay an
earth Mat under the ground level of Substation
yard.
The Earth Electrodes, in Earth pit are connected to
this Earth Mat, running nearby under the Ground,
so that the combined Earthing system is formed.
45. 45
EARTHING SYSTEM
• The soil in Earth pit should be kept well packed
homogeneously. The soil in Earth pit should be kept
wet by pouring water. Earth Connections are
checked for tightness. Earth pipe to be maintained
intact without corrosion.
• For improving the Earthing system Charcoal, Ash,
pentonite powder, Salt etc., may be filled in the
Earth pit and Watered.
• Earth Resistance value to be measured and
effectiveness checked, by using Earth Megger. The
values are 1) Individual Electrode : < 25 ohms.
• Combined Earth Resistance : less than one ohm.
47. 47
EARTHING SYSTEM
This should be tested by removing all connection
from Electrode.
2) Combined Resistance:
< 1 ohm.
This should be linked by providing all Earth
connection.
49. 49
ISOLATORS
These are Potential Isolating Switches to isolate the
equipments from the source.
This should not be used for current breaking. In
Sub-station , only “Double break” (or Center
rotating type as it is called) switches are used.
52. 52
ISOLATION & CONTROL OF EQUIPMENTS
• Isolator with Arcing horns: Used before
transformer to break magnetizing current.
• Isolator without Arcing horns: Used in other
places of Sub-station
53. 53
ISOLATION & CONTROL OF EQUIPMENTS
• Tandem Operation for simultaneous operation for the three
phases should be ensured.
• The contact pressure should be adequate to withstand load
current. This is ensured by spring & tempered contact leaves.
Contact pressure will be > 0.25 Kg. per ampere of normal
current rating.
• The Operation should be free by proper lubrication and by
treating the fixed and moving contacts with Petroleum Jelly.
• The close/open should be done from Ground level. The
operating Rod should be earthed safely.
• The isolator may be hand operated (or) it can be motor
operated using A.C. Motor with reduction gear & can
arrangement with limit switches, to stop the motor at the end
of closing/opening without overshoot.
• The Motor operated mechanism will also have the de-linking
arrangement to de-link motor & gear mechanism and perform
the hand operation in case A.C. Supply fails.
54. 54
BREAKERS
• The main purpose is: To break the load current or
fault current It should be capable of quenching the
arc quickly & effectively arising due to interruption
of heavy current.
• The rating of the breaker should be well above the
FAULT LEVEL of the substation, so that the breaker
is capable of breaking the maximum fault current
due to 3phase FAULT that may occur near. The
rating is defined in MVA and is called as
“RUPTURING CAPACITY”
• The time of opening should be fast. Modern
breakers are as fast as to open in 2 cycles (ie) in
0.04 secs. TYPES OF BREAKERS: The breakers
are classified according to the Medium by which arc
is quenched.
55. 55
BREAKERS
• OIL CIRCUIT BREAKER ( OCB) :
Oil is used for quenching as well as for insulation
since metal tank is used.
• MINIMUM OIL CIRCUIT BREAKER ( MOCB) :
Oil of small quantity is used for arc quenching only.
• VACUUM CIRCUIT BREAKER ( VCB) :
Arc extinguished in VACUUM
• GAS CIRCUIT BREAKER ( GCB) :
SF6 gas is used as the medium for quenching arc.
57. 57
BREAKERS
• Rated Breaking Capacity: It is the current (rms) that a breaker is capable
of breaking at a given recovery voltage and under specified condition i.e.
PF,RRRV
• Rated Making Capacity: The peak value of current including d.c. component
during the first cycle of current wave after the closure of circuit breaker is
known as making capacity Rated Short-time Capacity: It is the period for
which the circuit breaker is capable to carry fault current while remaining
closed.
• Rated Normal Current Rating: It is the rms value of current which the
circuit breaker is capable of carrying continuously at its rated frequency under
specified conditions with temperature rise of various parts within specified
limits.
• Relay Time: The time elapses between the instant of fault & the closure of
trip circuit. Circuit Breaker Time: The time elapses between the closure of
trip circuit & the final arc
• extinction Total Break Time: It is the summation of Opening Time and
Arcing time. Opening Time: The time interval lapses from the energisation
of trip coil to the instant of
• contact separation. Arcing time: The time from separation of contact to the
extinction of arc is called the arcing time
• Fault Clearing time: The time elapsed between the instance of the
occurrence of a fault and the instant of final arc extinction in the circuit
breaker i.e F.C.T.=Relay time + Circuit breaker time Total Break time)
59. 59
BREAKERS
• The Breaker has two operation :CLOSE / OPEN
• The OPEN operation is also called : “TRIP” These 2 operation are
speedily performed by using operating mechanisms of the following
kind:
• a) Spring actuated : Use of spring & leavers this can be operated
by hand (or) AC Motor
b) Hydraulic actuated : Using hydraulic fluid like “AERO- shell oil”
c) Pneumatic Actuated : using air comprised system Any type of
mechanism can be employed to any type of breaker.
• Details of maintenance procedure:
• Stationary contact: Visually inspect, when contact surface is found
uneven, remove it and polish with sand paper. then measure the
dimension of stationary contact. When the wear becomes 3 mm or
over replace the contact with a new one. Apply thin coat of Vaseline
to the contact.
• Moving contact: When it is deteriorated by large current
interruption remove it and polish with sand paper. Apply thin coat of
Vaseline to the contact.
61. 61
QUARTERLY “CARE”
Q.1. External Cleaning of Insulator Prior to monsoon and as &
when Shutdown is available or deposits are too thick. Dust /
Dirt to be removed.
Q.2. Switch cubicle cleaning: Open the switch cubicle & Remove
webs/ dust.
Q.3 Check wiring connection in switch cubicle Check wiring
connection Tightly secured. Check healthiness of the relay
operations.
Q.4. Compressor Check: Compare the Running Time.
Q.5. Compressed Air Plant Maintenance to be carried out as per
instruction manual check for any leakage, check oil leakage,
check for alarm, non Return valve to be opened & Cleaned,
Verify motor thermal overload is working or not.
Q.6. Pressure switch in switch cubicle: Check the pressure valve
by reducing the pressure and filling the pressure .
Q.7. Verification of SF6 Alarm Healthiness of alarm can be
verified by shorting electrical circuit, not by draining SF6 Gas.
62. 62
Trouble shooting chart for SF6 circuit
Breaker
• Type of Condition Possible Cause
A. Gas Alarm
CHECK :
1) Electrical Circuit
2) Gas pipe Braze Joints
3) Gas pipe Couplings.
4) Insulator joints.
5) Lip seal Assembly.
64. 64
PROTECTION FROM EXTERNAL
DISTURBANCES
• Protection from Direct Stroke of lightning.
• To protect all the equipments from the direct Stroh
of lighting earth mast is used.
• Earth mast is a metal spike with sharp end
• Height of mast is so chosen that all equipments
comes under the protective zone, defined as 45
degree cone with top of Spike as the APEX of the
cone.
• Effectively grounded to permit the lightning
discharge.
66. 66
PROTECTION
• This will travel on the line up to the transformer
winding and shatter it therefore the surges are is be
prevented from entering the Transformer.
• “SURGE DIVERTORS” are provided before and after
the transformer.
70. 70
Potential Transformer
• The Secondary rating of PT is 110volts 11 KV / 110
VOLT is shown, In Radial stations, P.T. used for
metering only P.T. will have only a small burden (in
VA).
71. 71
Current Transformer
• Each Breaker is associated with a set of C.Ts for
Protection & metering
• Secondary Current: 1 Amps
• Separate
72. 72
Current Transformer
• secondaries will be available for protection of
metering.
• C.T. Ratios of say 600, 300, 150/1Ampere or 5
Ampere are available for usage.
• It is defined as : Ratio available : Ratio set at :
• C.T. will also have a small burden (say 30 VA) to
connect meter or Relay loads.
• C.T. Secondary should never be open – circuited.
73. 73
RELAYS
• 3 O/L and 1 O/L Relay Scheme for Transformers and
Breakers and Differential Relay for Transformer only
76. 76
D.C. SYSTEM
• Points:
• 2 Sets of 110V battery are used, one set for control
of feeders and the other set for protection of
Transformers and group control breakers.
• At Normal condition charger will supply small DC
loads & feed charging current to Battery Heavy trip
coil currents supplies by battery.
• The battery should be kept on wooden stand over
insulated pedestal.
77. 77
D.C. SYSTEM
• Maintenance
• The cell voltage should be around 2 VOLTS &
Specific gravity of Electrolyte 1200/27 degree.
• Battery should be on trickle charge continually.
• If drained due to continuous tripping it should be
put on quick charge & brought to the level.
• To be tested daily for leakage is detected & for
catering of load.
• If positive or negative leakage is detected, the
faulty section to be isolated & rectified.
• Battery room should be free of dust ,fire etc &
properly ventilated.
78. 78
D.C. SYSTEM
• Breaker is in closed condition feeding a 11KV feeder. If any
fault occurs on the feeder, the breaker should trip. Cutting off
supply to the feeder. The sequence is as follows:
• Fault occurs on the feeder & heavy current flows thro the
circuit
• The C-T Senses the fault current & high secondary current
flows through the Relay coil.
• The relay contact closes & D.C circuit is closed.
• With breaker kept on Auxiliary Contacts 4-4’& 3-3’ are N/c &
hence D-C + Ve & - Ve juice is supplied to the trip coil
• Trip coil energized & the plunger is moved up & trigger the trip
latch.
• The Breaker is tripped of Aux Switch moves of the contacts 4-
4‘& 3-3’ are now N/o & hence the trip coil current is cut off.
• Since faulty section is isolated, the current in secondary is
zero & hence relay moves back to its normal position,
breaking the relay contact.
79. 79
TRANSFORMER PROTECTION
• The transformers are controlled by group control
breaker on 110 KV side & independent L.V. breakers
on 11KV side. If a fault occurs on transformers
these breakers should be tripped.
• The fault on the transformer is identified by:
a) Over current relay
b) Differential Relay
c) Bucholtz relay
d) Winding temp relay
e) Pressure Release Valve Relay
81. 81
TRANSFORMER PROTECTION
• Closing of these contacts by actuation of relay in
case of fault initiates the trip circuit of the
controlling breaker thro’ a common relay called
“MASTER RELAY”
82. 82
L.T.A.C. SUPPLY SYSTEM
• A Station transformer of 100KV 11KV/400V as connected to
the 11KV Bus. provide A-C supply (Alternative supply) either
fed from another substation (or) from a generator will be
provided for emergency.
• The LT A-C supply / Alternative supply is fed to the A-C panel
in control room from which it is supplied to the following
requirements with power control arrangements.
• To A.C motors of breaker mechanism, Air compressor
systems,
• To cooling fans of pump motors of power transformer& OLTC
operation to battery charger Yard lighting and control room
lighting
83. 83
TAP OPERATION
• Since the sub section in the sending end of power
to the load pockets, it is necessary to maintain
constant voltage at the secondary, irrespective of
voltage received on HV side. This is done by
providing On Load Tap Changer.
• A diagram of tapping coil arrangement with Main
primary coil with pre selector AND Selector contacts
and also its On load operational features sequence
are shown in the two figures enclosed.
85. 85
STANDARD CLEARANCES ADOPTED IN
PRACTICE
• b) SECTIONAL CLEARANCES in “MM”
• 1. 230 KV -4270 MM
• 2. 110 KV -3350 MM
• 3. 66 KV -3050 MM
• 4. 33 KV & 22 KV -2740 MM
• 5. 11 KV -2590 MM
• c) BAY WIDTH “IN METRES”
• 1. 230 KV -12.2
• 2. 110 KV -9.5
• 3. 66 KV -7.0
• 4. 33 KV -4.5
• 5. 22 KV -3.8
• 6. 11 KV -3.5
86. 86
CONCLUSION
• The sub station forms part & parcel of the power of
the power system net work. The essential
equipments installed in a sub station, with the
operation and control features are explained in
detail which will provide practical utility information
87. 87
SUB STATION EQUIPMENTS AND ITS
FUNCTIONS
• Bus Bars:
Various incoming and outgoing circuits are
connected to bus bars.
Circuit Breaker:
Switching, automatic interruption
Isolator, also called disconnecting switch:
Disconnection under no load condition.
Earthing switch:
Discharging the voltage on the lines to earth for
safety.
88. 88
SUB STATION EQUIPMENTS AND ITS
FUNCTIONS
Lightning arrester:
Diverting the high voltage surges to earth and
protect insulation
Current Transformer:
Stepping down current for measurement protection
and control.
Voltage Transformer:
Stepping down voltage for purpose of protection
and control
89. 89
SUB STATION EQUIPMENTS AND ITS
FUNCTIONS
Series reactor:
To limit short circuit current level. Used in
approximate location.
Tap-changer:
Used for voltage control, stepping up and stepping
down voltages.
Shunt reactors:
Used for long EHV transmission line to control
voltage during low load period. To compensate
shunt capacitance of transmission line.
90. 90
SUB STATION EQUIPMENTS AND ITS
FUNCTIONS
Shunt capacitors:
Power factor improvement, switched in during low
power factor loads and less voltage.
Series capacitors:
Used with EHV transmission lines to increase the
power transferability.
Coupling capacitors and line traps:
For carrier current equipment.
94. 94
Over current relay
Over current relay responds to increase in current.
When the current in the operating coil increase
above certain value the relay picks up.
101. 101
General safety methods
• While execution of any work, that part of equipment
or line is to be isolated from the supply.
• Using discharge rods, charging, current if any is to
be discharged.
• Using Earth rods, all phases/conducting paths are to
be property earthed by securing good Earthing.
• When even opening an AB switch or removing of
fuse, it is also advisable and preferable to wear
rubber gloves.
• Use of belt rope is another safety method to be
adapted to work on elevated places.
102. 102
Line clearance (LC)
• For Grid feeders and Stations, the authorized officer for issue
of line clearance is S.E. (L.D. Centre), Madras, for 110 KV, 66
KV, radial feeders SE/ concerned and for 33 KV EE/O&M are
the approving authorities. Without obtaining proper approval
from the competent authority, no L.C. should be issued nor
availed by anybody.
• Hence, after getting proper approval, line clear is to be
issued to the requested party. Both should have knowledge
about equipments. The line clear issuing person should
clearly record the following:
• a) Which breaker is tripped?
• b) Which A.B. switches were opened?
• c) Where Earthing was done?
• d) What is the Safer place / Line to carry on the execution of
work.?
103. 103
Safety arrangements in control room
• Keyboard should be in open condition with keys are orderly arranged to take out quickly
during any urgency. Line clear keyboard should be in locked up condition to prevent
other persons from using the keys inside, before the cancellation of the Line clear
permit.
•
• Rubber mat should be provided on the floor in front of the panel board.
•
• The following details should be clearly displayed in the control room.
• a) Approved operating instructions for all equipment’s.
• b) Break down instructions.
•
• The operator should be fully conversant with the above instructions and the must be
able to act quickly and effectively.
•
• The D.C. cable layout, panel-wiring diagram and earthing layout should be displayed in
the control room. This is necessary to attend the faults immediately after their
occurrence. D.C. Earth leakage test system should be available.
•
• There should not be any defective power plugs, switches and bulb holders in the control
room wiring.
•
• One artificial respirator should be available in ready condition. Stools made of insulating
material should be used for operating HT communication equipment (Telephones).
•
• Adequate number of rubber gloves, belt ropes, discharge rods, and earth rods in good
condition should be available in the control room.
104. 104
Safety arrangements in battery room
• Battery room should be in locked up condition.
• “Naked flame is prohibited inside of the battery room” and “Smoking
prohibited” warnings should be kept written on the battery room
door.
• One exhaust fan should be functioning.
• Accurate D.C. cell testing voltmeters, hydrometers and
thermometers should be available in the battery room.
• Pilot cell voltage, specific gravity and temperature should be taken
every week.
• The specific gravity should not be maintained below 1195 at 15.6°C
and below 1183 at 32. 20°C. The battery should not be allowed to
discharge below 1160.
• Cell voltage should be maintained between 1.95 V to 2.05 V. The
battery should not be allowed to discharge below 1.85 V.
• Battery should be allowed neither to over charge not to
undercharge. It should not also be kept idle.
• Electrolyte level must be checked in every shift. It must be ensured
that the level is 10mm above the top of the plates.
• Weak cells should be rectified then and there.
• While taking specific gravity readings, care must be taken not to
allow the acid to come in contact with the eyes.
105. 105
Safety adopted for transformers
• Transformers are to be maintained periodically as per
schedule. Switches on HV side and LV side are to be isolated
after reducing the Load by tripping the breakers.
• Kiosks and OCB: All the Live parts of the kiosk should have H.
T. insulation tape. To be protected by wire mesh. It should be
vermin proof. Keys are to be kept with interlock. Whenever to
open the door of the kiosk, kiosk should be tripped and link
should be opened by the interlock key. The opening of the
links is to be verified physically. After doing all the above
precautions, the tank should be lowered down. Proper care is
to be taken and it should be kept in mind that supply is
available at the roofing. Oil leak should be arrested. Back
feeding is avoided. Cotton waste should not be used for
clearing purpose.
106. 106
Circuit Breakers
• SF6 breakers are maintenance free comparing to the air blast circuit breakers and oil circuit breakers.
Preventive maintenance avoids premature failure. It shall be done as per manufacturer’s
recommendation.
• Continuous monitoring of gas pressure is essential. If there is gas leakage, top up before gas low
alarm / indication is received. Gas leakage test shall be carried at all leakage sources by availing shut
down.
• If the breaker is pneumatically operated, compressor starting pressure, building up pressure time shall
be checked with respect to pre-commissioning test values.
• Air pressure drop for each operation shall be checked and ensured the values are within limits.
• If the breaker is spring operated mechanism, spring charging time shall be checked with the pre-
commissioning test values. For each closing operation, see that spring is charged fully and indication
received.
• The following breaker operation checks shall be done as per periodicity.
• 1. Breaker opening time & closing time are within limits
• 2. Whether pole discrepancy relay operates.
• 3. Checking of all operational lockout.
• 4. Checking of all pressure settings
• 5. Checking of all inter locks
• Measurement of breaker contact resistance, resistance of close and trip coils and MV drop test across
terminal connectors shall be done periodically.
• Healthiness of operation counter shall be checked.
• Tightness of all cable connections in control cubicle and working of space heater shall be checked.
• Checking of door gaskets, blocking of spare cable entry holes and must be ensured for vermin proof.
• Cleaning of breaker poles and support insulators shall be done with clean Gada cloth. Using cotton
waste shall be avoided. Vacuum cleaners shall be used for cleaning for control cubicle. Ensure that the
terminal connectors are free from corona.
107. 107
Safety in AD switches
Handle of the AB switch is to be earthed properly.
Blades should be kept at opening position. It should
not be closed automatically; proper maintenance is
to be done for this. AB switchblades are to be
opened fully. AB switches are to be kept locked on
both conditions. AB switches are to be opened only
after tripping the breakers.
108. 108
Safety in Lightning arresters
Lightning arresters are used to bypass the sudden
lightning surges and thereby to protect the
equipment’s. Only after proper discharging is done
on lightning arresters, it should be attempted to
attend to maintenance. Fencing is to be provided
around lightning arresters. A door arrangement with
lock is to be provided. Separate earth connections
are to be provided for lightning arresters.
109. 109
Safety in instrument transformers
• Current transformer secondary side is to be short
circuited during maintenance and testing. Before
doing any testing, the current transformers are to
be discharged.
• Potential transformers primary side is to be Earthed
during maintenance and testing. Secondary side is
to be earthed at only one place. Whenever giving
connection, or removing meters on the secondary
side of die potential transformer, the fuses are to be
removed and renewed.
110. 110
Capacitors
Capacitors should be provided inside fencing. Before
attempting to do any work, proper discharging is to
be done. They only it should be attempted for
maintenance work. Proper Earthing should be
provided during the execution of the work. After
completion of the work, Earthing is to be removed.
111. 111
Earth pits
• Sub-station earth connections should be properly maintained
so that the earth resistance is minimum. Water should be
poured in the earth pits daily. Earth connections, must be
capable of protecting the persons working in the electrical
equipment’s and protect in the equipment’s during heavy fault
current. Earth resistance should not exceed the following
limits.
• Grid stations: I Ohm
• Other sub-stations ..2 Ohm.
• Distribution transformers ..5 Ohm.
• They must be a clearance of 5 feet, between the sub-station
fence and the electrical equipment’s / live points. The fence
should be earthed at every 200 feet, separately. Generally the
fence Earthing should not be linked with the sub-station
Earthing. But if the clearance is less than 5 ft. feet fence
Earthing must be linked with the sub-stations Earthing. The
iron gates in the sub-station fence should also be earthed
separately.
112. 112
Fire fighting equipments
The equipments are to be kept on good and working
condition. Proper schedule of maintenance is to be
done for keeping them in good conditions. The
equipments should be kept at an easily accessible
place so as to use them immediately under
emergency. Dry sand heaps are to be available
wherever necessary. Empty buckets are to be
provided.
113. 113
S.S. Yard
• S.S. yard should be provided with fencing.
• Unauthorized persons should not enter into the
yard
• Cable ducks are to be provided with slabs.
• Best illumination is to be provided for the yard.
• A warning board with a display that “Umbrella”
stick Dogs should not be brought inside the yard”
is to be provided at the entrance of the yard.
• A separate room is to- be provided for keeping the
empty drums. At the entrance of the room “No
smoking” Board is to be provided.
114. 114
General causes for accidents in SS
• Mal operation in view of symmetrical designing of
equipments.
• Opening of switch on Load/ working without proper supply
isolation.
• Working without de-energizing and earthing of lines and
equipments.
• Charging the equipment without removing the earth rod.
• Working without knowing the back feeding available in the
equipment.
• Operation without making back feeding and alternate feeding
into oneness (Two phase to Three phase linking)
• Charging the equipment without concurrence on both ends of
supply point (eg. Grid feeders).
• Charging the feeders without considering the total number of
line clears availed in a feeder (e.g. charging after returning
one L.C.)
• Giving L.C. in the feeder, but climbing on the roof top of the
KIOSK (without Bus L.C.)
115. 115
Avoidance of accidences
• Strictly adopting LC procedures and operating instructions in
every operational work though it is minor.
• All operation in the yard in the presence of operator or at
least with the knowledge of the operator.
• Be always keep in mind that “Authorized Person; Approved
Work”
• Through knowledge of equipments and systems,
observational ability, analytical ability and communication
skills are required to the operators.
• Ready to use fire-fighting equipments and operators should
have knowledge in using the same.
• No defective equipments should be put into service.
116. 116
Conclusion
In every sub-station, action should be taken for
adopting safety precautions, so as to avoid
accidents. All staff should be well educated about
the safety rules, precautions and methods.
117. 117
Case study
An operator on shift duty observed tripping of an
11KV Town Feeder with loud noise. He went to the
yard and charged the OCB of the concerned feeder
after resetting the relay with indications of 3 OL and
1 EL. Immediately on charging there was loud burst
and oil with flame from the Breaker engulfed the
operator resulting in a fatal accident. After thorough
inspection and investigation following were found to
be the causes for the accident.
118. 118
Basic cause
The breaker had not immediately isolated the fault
by tripping. There, had been sluggishness in
breaker operation, which resulted in feeding of fault
with high current, arcing, carbonization of oil and
heavy evolution of gases. (Unsafe condition)
119. 119
Major causes
• All the moving contacts of the breaker were highly
corroded without replacement (Unsafe condition).
• Oil was not tested before filling into Breaker
(Unsafe condition).
120. 120
Minor causes contributing the
accident
The operator did not check for any indication like
smoke or spilling of oil surrounding the tank or thro’
the vent pipe. When there were indications of 3 OL
and 1 EL the operator should have been more alert
and checked for any near by fault. (Human error
-Unsafe action)
122. 122
BATTERY
• Over the years the batteries that are used in power
plants and substations have not changed a lot. Yes,
we have batteries made of different material, some
of them are sealed, and others use different
electrolytes.
• The battery system usually forms the heart of the
DC control and protection system for the station.
This DC system is the power source for equipment
control and protection. The need to have this
system extremely reliable is what drives
preventative maintenance on batteries.
123. 123
• Regardless of the type of battery, it must be maintained to
function properly. We typically maintain our batteries on a
weekly, monthly, and yearly schedule.
• On a weekly cycle, the battery is inspected, several cell
voltages are read, and the respective specific gravities are
checked.
• On a monthly basis, all the cell voltages are read and all the
specific gravity readings are taken.
• Annually, all the inter cell connections are removed, cleaned,
lubricated and reinstalled. Doing all of the recommended
maintenance requires many man-hours.
BATTERY
124. 124
BATTERY
• The installation of the monitoring system consisted
of installing 2 sensing modules to the side of each
battery jar. These are attached with a self-adhering
tape that is an integral part of each cell module. In
addition, it was decided to install a wire gutter to
contain the cell-to-cell data link and other wire.
This made for a neat installation. See Figure 1.
127. 127
BATTERY
• Figure 1 shows the sensing modules and wire gutter
attached to the jars. Also shown are the measuring
leads attached to the bus bars, and the chokes
attached to the main battery leads.
128. 128
BATTERY
• Figure 2 shows the communication interface (with built in
modem) and the bank monitor/controller mounted on the
wall, the current sensor mounted at cell #1, and the rest of
the hardware.
129. 129
BATTERY
• Next, connections were installed to each bus
between the battery posts. These connections are
used to measure cell voltage, and voltage drop
across the cell when a one-millisecond bank load is
applied for the current path integrity test.
• A choke (isolation inductor) is installed around each
main battery lead. The installation of all the
equipment took two days and consisted of mounting
modules on each cell, installing power cabling, and
mounting the bank monitor and communications
interface equipment. See Figures 2.
130. 130
BATTERY
• Measuring leads
• chokes
• Current sensor
• Bank monitor/system controller
• Communications interface
• The overall system is shown schematically in Figure
3. The data links between the cell monitoring
modules are optically isolated to eliminate the
possibility for a current path to exist between
modules. The isolation inductors (chokes) provide
test isolation for approximately one millisecond
during the connection resistance test (current path
integrity test).
132. 132
BATTERY
• Once the equipment was installed the system was set up and
calibrated. A complete set of readings was taken on the
battery and the data entered into the software as the starting
point for monitoring. Much to our surprise, within days of
putting it in service, the monitoring system started to report
problems with the battery.
• The first deficiency it found was high resistance at several
inter-cell link and battery post connections. We had taken
resistance readings on the connections and not found any
problems. However, the monitor takes connection voltage-
drop readings while a load of about 400 amps is applied to the
battery for one millisecond (current path integrity test). This
method found poor connections that we had missed. See
Figure 4.
• Figure 3 shows the overall configuration of the non-invasive
battery monitoring system
133. 133
BATTERY
Figure 4 is a view of the opening page showing cells with
problem in red. All the cells in question had high resistance
connections.
134. 134
BATTERY
• The current path integrity is measured by employing the four-
wire resistance technique. To prepare for the measurement,
the bank monitor simultaneously instructs all cell monitors to
measure their cell’s voltage and store the result in memory.
• The bank monitor next switches an electronic load across the
bank that draws current for approximately one millisecond. At
the peak of the bank current, which is arranged to be roughly
equal to the amp-hour capacity of the bank, the bank monitor
again simultaneously instructs all cell monitors to re-measure
cell voltage and subtract the results from the zero-current
values of voltage already stored in memory.
• The difference voltage for each cell, reported as “delta V” is
proportional to the resistance of the current path including
both the cell and strap/post connections. Figure 5 shows the
relationship of the voltages and currents during this test.
136. 136
BATTERY
• Upon opening the software up to the individual
cells, one can get either a cell-by-cell view of the
battery or a view that shows the average cell, the
high cell, and the low cell in each category.
• In looking at Figure 6 you can see the trends of cell
#1 over a period of time. Of interest is the gradual
rise in the voltage drop across the connection of
this cell. With every voltage drop alarm, our
electricians reported that the connecting bolts did
tighten before the torque wrench reached the
desired value.
• It was also interesting to note that just prior to
developing a high resistance connection the battery
underwent a load cycle as indicated by the
downward spike in the readings, shown in Figure 6.
137. 137
BATTERY
• Voltage-current relationship for measuring the
voltage drop across connection resistance in the
series circuit
• The load is electronically inserted across the battery
for one millisecond. The chokes provide test
isolation.
• Figure 5 shows the process for automatically
measuring current path integrity
139. 139
BATTERY
• After some months of operation MCM reviewed the
data that was being taken. They noticed that the
water consumption of the battery was fairly high.
From the Float Current Bypass cell readings it was
noted that all the cells were bypassing 100% of the
float current. In essence this indicated that the
battery was being over charged, making it use more
water. We started lowering the float voltage until
most of the cells read in the 80% bypass range.
This reduced water consumption in the battery. See
Figure 7.
140. 140
BATTERY
• The system allows the user to look at many
conditions in each cell, and the battery bank as a
whole.
• In addition it will record bank discharges, showing
the overall bank and each cell’s performance during
the discharges.
• This information goes a long way to assuring the
quality and integrity of the battery.
141. 141
BATTERY
• The monitoring system performs a test on the
battery however often the user desires. The
monitoring system is set up to automatically do a
test and collect data every 24 hours at Morrow
Point.
• This gives us good data without building a huge
database. However, during a load test on the
battery or during an actual emergency event, the
battery monitoring system steps up its data
measurement rate to capture the performance of
the battery, during the event.
142. 142
BATTERY
• The data is downloaded to a computer in the plant
once a week, reviewed, and any necessary actions
taken.
• This test sequence yields the data that we have
looked at above. This system has been in use for
almost two years, and has successfully found
serious problems; it has also minimized the
required battery maintenance.
143. 143
BATTERY
• The cost of this system approaches the cost of a
battery. In order to justify this cost we must take a
close look at what our battery does, and how
important it is in the overall scheme of things.
• Not all battery systems are used for the same
purpose, however most of them operate the control
and protection schemes for large rotating
equipment and breakers when they are employed in
power plants and substations.
144. 144
BATTERY
• Figure #7 is a screen view showing the high, low and average
of all the cells. Note that the fluid levels move down. The
straight line shows where water was added. Note place where
the bank voltage is lowered you also notice that the slope of the
water use curve changes, and the cell bypass currents drop.
145. 145
BATTERY
• For the most part the DC control and protection circuits in
Reclamation facilities run on battery chargers most of the
time. Only under charger failure or loss of station AC power
do we need the batteries. As often happens, it is during times
of system or equipment problems when station AC
disturbances will occur.
• This is simply Murphy’s Law in action. These are the times
when controls, protection and breakers MUST operate to
prevent damage to equipment. Thus, the main purpose of the
battery is to provide critical power to control and protection
equipment when it most needs it. Failure of the battery
system during these periods of time can have consequences
that range into the millions of dollars for the equipment they
protect.
• Thus it must be argued that the justification for the
monitoring system should be based on the cost of these
consequences rather than the ratio of the cost of the battery
versus the monitoring system.
146. 146
BATTERY
• The bottom line for the monitoring system at Morrow Point is
that it has drastically cut our man-hours of maintenance.
Since the monitor’s installation, several bad connections have
been corrected, and the battery bank has had water added
only twice.
• Then since system has been in service; a set of readings was
manually taken after one year to verify the readings of the
monitoring system, and they proved to be identical. The
Morrow Point crew has decided that a lot of the maintenance
that was done previously was probably causing as many
problems as they solved. Redoing the jumper bar connections
probably loosened more connections than it did to repair
possible corrosion and tightness problems.
• The need to be assured that your battery will operate as
designed when it is needed most has been assured. This along
with the reduced maintenance makes the cost of the system
easily justifiable.
148. 148
SAFETY IN SUB-STATION
• Prevention of damages to equipment’ s and men
working on then due to any accidents is an essential
aspect in any establishment. Prevention of accident
which is an unforeseen one is more essential aspect
of any establishment / organization.
• As accidents occur mainly due to unsafe execution,
actions and circumstances, these accidents can be
avoided by adopting safety precautions,
implementing safety procedures and following
safety rules.
149. 149
SAFETY IN SUB-STATION
• General safety methods:
• While execution of any work, that part of equipment
or line is to be isolated from the supply.
• Using discharge rods, charging, current if any is to
be discharged.
• Using Earth rods, all phases/conducting path are to
be property earthed by securing good Earthing.
• When even opening an AB switch or removing of
fuse, it is also advisable and preferable to wear
rubber gloves.
• Use of belt rope is another safety method to be
adopted to work on elevated places.
150. 150
SAFETY IN SUB-STATION
• Safety methods to be adopted in Sub-Stations :
• In any work is to be attended to any line, first and fore most
item of work is to get proper approval from the competent
controlling authority for execution of the work specifying the
date, time, duration, place of work, affected parties etc. .
• For Grid feeders and Stations, the authorized officer for issue
of approval is S.E. (L.D. Centre), Madras, For 110 KV, 66 KV,
radial feeders Superintending Engineer / Distribution is the
approving authority. Similarly for 33 KV Divisional Engineer
incharge of distribution is the approving authority.
151. 151
SAFETY IN SUB-STATION
• Without obtaining proper approval from the
competent authority, no L.C. should be issued nor
availed by anybody. If the above procedure is not
followed, it is nothing but a suicidal. Further it also
amounts to murder of others.
• So, after getting proper approval, line clear is to be
issued to the requested party. But the issue and
receiver should be aware/have full knowledge about
the SS equipment’s, control room panel details etc.,
152. 152
SAFETY IN SUB-STATION
• The line clear issuing person should clearly record
the following:
• a) Which breaker have been tripped
• b) Which A.B. switches were opened
• c) Where Earthing was done
• d) What is the Safer place / Line to carry on the
execution of work
153. 153
SAFETY IN SUB-STATION
• Safety arrangements in control room:
• Key Board should be in open condition so that the keys could
be taken out quickly during any urgency.
• Line clear keyboard should be in locked up condition to
prevent other persons from using the keys inside, before the
cancellation of the Line clear permit.
• The keys should be placed in the key board in an orderly
manner according to their numbers. Otherwise, the required
lock could not be opened in time and the possibility of opening
a wrong lock may happen.
• Rubber mat should be provided on the floor in front of the
panel board.
154. 154
SAFETY IN SUB-STATION
• The following details should be clearly displayed in the control
room.
• Approved operating instructions for all equipment’s.
• Break down instructions.
• Operating instructions including for the emergency operations
to be carried out in the event of operation of buchholz relay.
Differential relay, Group control trip, total supply failure, grid
failure. The operator should be fully conversant with the above
instructions and the must be able to act quickly and
effectively.
• The Board containing D.C. cable layout. A cable layout panel
wiring diagram and Earthing layout should be displayed in the
control room. This is necessary to attend the faults
immediately after their occurrence.
• 5) D.C. Earth leakage test system should be available.
155. 155
SAFETY IN SUB-STATION
• There should not be any defective power plugs,
switches and bulb holders in the control room
wiring.
• One artificial respirator should be available in ready
condition.
• Stools made of insulating material should be used
for operating high tension communication
equipment’s (Telephones).
• Adequate number of rubber gloves, belt ropes,
discharge rods, and earth rods in good condition
should be available in the control room.
156. 156
SAFETY IN SUB-STATION
• Battery room:
• Battery room should be in locked up condition.
• “Naked flame is prohibited inside of the battery room” and “Smoking
prohibited” warnings should be kept written on the battery room door.
• One exhaust fan should be functioning.
• Accurate D.C. cell testing volt meters, hydro meters and thermometers should
be available in the battery room.
• Pilot cell voltage, specific gravity and temperature should be taken every
week.
• The specific gravity should not be maintained below 1195 at 15.6°C and below
1183 at 32. 20°C. The battery should not be allowed to discharge below
1160.
• Cell voltage should be maintained between 1.95 V to 2.05 V. The battery
should not be allowed to discharge below 1.85 V.
• Battery should be allowed neither to over charge not to undercharge. It
should not also be kept idle.
• Electrolyte level must be checked in every shift. It must be ensured that the
level is 10mm above the top of the plates.
• Weak cells should be rectified then and there.
• While taking specific gravity readings, care must be taken not to allow the
acid to come in contact with the eyes.
157. 157
SAFETY IN SUB-STATION
• Safety adopted for transformers:
• Transformers are to be maintained periodically as per
schedule. Switches on HV side and LV side are to be isolated
after reducing the Load by tripping the breakers.
• Kiosks and OCB : All the Live parts of the kiosk should have
H. T. insulation tape. To be protected by wiremesh. It should
be vermin proof. Keys are to be kept with interlock. When
ever to open the door of the kiosk, kiosk should be tripped
link should be opened by the interlock key. The opening of the
links are to be verified physically. After doing all the above
precautions, the tank should be lowered down. Proper care is
to be taken and it should be kept in mind that supply is
available at the roofing.
• Oil leak should be arrested. Back feeding is avoided.
• Cotton waste should not be used for clearing purpose.
158. 158
SAFETY IN SUB-STATION
• AB switches:
• Handle of the AB switch is to be earthed properly.
Blades should be kept at opening position. It should
not be closed automatically, proper maintenance is
to be done for this.
• AB switch blades are to be opened fully. AB
switches are to be kept locked on both conditions.
• AB switches are to be opened only after tripping the
breakers.
159. 159
SAFETY IN SUB-STATION
• Lightning arresters :
• Lightning arresters are used to bypass the sudden
lightning surges and thereby to protect the
equipment’s.
• Only after proper discharging is done on lightning
arresters, it should be attempted to attend to
maintenance.
• Fencing is to be provided around lightning arresters.
Door arrangements with lock is to be provided.
Separate earth connections are to be provided for
lightning arresters
160. 160
SAFETY IN SUB-STATION
• Current transformers:
• Current transformer secondary side is to be short
circuited during maintenance and testing.
• Before doing any testing, the current transformers
are to be discharged.
161. 161
SAFETY IN SUB-STATION
• Potential transformers:
• Potential transformers primary side is to be Earthed
during maintenance and testing. Secondary side is
to be earthed at only one place. Whenever giving
connection, or removing meters on the secondary
side of die potential transformer, the fuses are to be
removed and renewed
162. 162
SAFETY IN SUB-STATION
• Capacitors and H. T. Coupling capacitor:
• Capacitors should be provided inside fencing.
Before attempting to do any work, proper
discharging is to be done. They only it should be
attempted for maintenance work. Proper Earthing
should be provided during the execution of the
work.
• After completion of the work, Earthing is to be
removed.
163. 163
SAFETY IN SUB-STATION
• Earth pits:
• Sub-station earth connections should be properly
maintained so that the earth resistance is
minimum. Water should be poured in the earth pits
daily.
• Earth connections, must be capable of protecting
the persons working in the electrical equipment’s
and protect in the equipment’s during heavy fault
current.
• Earth resistance should not exceed the following
limits.
• Grid stations: I Ohm Other sub-stations ..2 Ohm
164. 164
SAFETY IN SUB-STATION
• Earth pits:
• Distribution transformers ..5 Ohm.
• They must be a clearance of 5 feet, between the sub-station
fence and the electrical equipment’s / live points. The fence
should be earthed at every 200 feet, separately. Generally the
fence Earthing should not be linked with the sub-station
Earthing. But if the clearance is less than 5 ft. feet fence
Earthing must be linked with the sub-stations Earthing. The
iron gates in the sub-station fence should also be earthed
separately.
165. 165
SAFETY IN SUB-STATION
• Fire fighting equipments:
• These equipment’s are to be kept on good and
working condition. Proper schedule of maintenance
is to be done for keeping them in good conditions.
These equipment’s should be kept at an easily
accessible place so as to use them immediately
under emergency.
• Dry sand heaps are to be available wherever
necessary. Empty buckets are to be provided.
166. 166
SAFETY IN SUB-STATION
• S.S. Yard:
• S.S. yard should be provided with fencing.
• Unauthorised persons should not enter into the yard
• Cable ducks are to be provided with slabs.
• Best illumination is to be provided for the yard.
• A warning board with a display that “Umbrella” stick
Dogs should not be brought inside the yard” is to
be provided at the entrance of the yard.
• A separate room is to- be provided for keeping the
empty drums. At the entrance of the room “No
smoking” Board is to be provided.
167. 167
SAFETY IN SUB-STATION
• General
• The territory of the work spot which was declared safety to
work is to be clearly identified by tying a rope. Inside this
boundary is to be further identified by hanging a green flag.
Outside this boundary where it is unsafe to work is to be
identified by a red flag.
• Wherever necessary caution boards like “Men on working”
“Don’t Switch on“ Safe for work” etc., are to be provided.
• If any unauthorized, unskilled staff happen to go near the
equipment’s he can do so with the assistance and under the
vigil of an experienced, authorised staff.
• Conversation is strictly prohibited wile execution of any work.
It should be totally avoided especially when work is being
carried out on any bus bars and kiosk.
• Placing the materials, tools and plants and men are to be at a
safety clearance from the Live. parts.
168. 168
SAFETY IN SUB-STATION
General:
• T & Ps like spanners etc. are to be lifted and brought
down only by means of ropes and not by throwing
and catching.
• Study and safe ladder with steps at convenient
intervals is to be used. To avoid slippage of the ladder,
necessary precaution is to be taken at the bottom of the
ladder by providing empty gunnies.
• Lifting of any ladder or rods (Earth) are to be done only
horizontally. Vertical lifting may cause damages by
interrupting with the safe clearances.
• The bus and line links art’; to be kept opened while
doing work on OCB and OMCB Summing up, 100% care
should be taken in adopting and implementing safety
rules and precautions.
169. 169
SAFETY IN SUB-STATION
• Conclusion:
• In each and every sub-stations, action should be
taken for adopting safety precautions, so as to
avoid accidents. Each and every staff should be
wel1 educated about the safety rules, precautions
and methods. If everybody is aware of the safety
procedures, rules etc., accidents can be eliminated
in sub-stations.
&lt;number&gt;
This is not a meeting to discuss difficulties in project coordination or the details of project technicalities. Issues that could not have been resolved by the secondary level of management that the Belt would have to deal with would qualify for approval at this meeting
The “Status” quadrant refers to displaying the appropriate status of the project. This means a mean/stdev status or associated project accomplishments in terms of ppm can be displayed. This would raise the attention of the management on what the issues are at hand to get the project moving if there is a gap.
The “Needs” quadrant refers to specifically listing the needs in 3 or more primary areas, such as resources, budget, and timeline in order to improve the project “status.” Once the needs of the project are met, the status has to move in the right direction. Without any negative implications, this has to be point specific, that the management comes out with a “yes,” “no,” or “maybe” by the latest within a week prior to the next review. Use escalation policy here if needed.
The “Issues” quadrant refers to a direct consequence of not meeting the needs by the expected time. This usually gets the attention provided it is validated by the team at the appropriate level of management. This quadrant leads the management immediately into, “what do we need to do to get this project accomplished?”
The “Action Items” quadrant is the kicker and it deals with the highest level of commitment from the management top-down. The other advantages of this quadrant is two-fold. (a) First, if the action items on this are accomplished by the date expected, it automatically forces the belt in a positive way to lean on his mentor. This would indirectly make the review meetings, training, and other exercises more exciting as they go back to a management that is responsive and totally supportive. (b) Secondly, the subsequent review would be very effective by merely looking at the past action items and any new issues that needs to be addressed.
The critical philosophy of this four-block is that for a successful session, the belt needs to spend about 5 % of their time on the “status” quadrant and the rest on the remaining. In many cases due to no fault of their own, they end up talking about the “status” 95 % of the time and by the time they get to the action items, the management is not energized enough to take decisions on the action item. Thus in a 10 minute review session, take about a minute or two on the “Status” part and devote the rest on the remaining three quadrants. Get the sponsor, functional leader, and site leader to sign off on the action items and communicate via e-mail to document the process.
This is not a meeting to discuss difficulties in project coordination or the details of project technicalities. Issues that could not have been resolved by the secondary level of management that the Belt would have to deal with would qualify for approval at this meeting
The “Status” quadrant refers to displaying the appropriate status of the project. This means a mean/stdev status or associated project accomplishments in terms of ppm can be displayed. This would raise the attention of the management on what the issues are at hand to get the project moving if there is a gap.
The “Needs” quadrant refers to specifically listing the needs in 3 or more primary areas, such as resources, budget, and timeline in order to improve the project “status.” Once the needs of the project are met, the status has to move in the right direction. Without any negative implications, this has to be point specific, that the management comes out with a “yes,” “no,” or “maybe” by the latest within a week prior to the next review. Use escalation policy here if needed.
The “Issues” quadrant refers to a direct consequence of not meeting the needs by the expected time. This usually gets the attention provided it is validated by the team at the appropriate level of management. This quadrant leads the management immediately into, “what do we need to do to get this project accomplished?”
The “Action Items” quadrant is the kicker and it deals with the highest level of commitment from the management top-down. The other advantages of this quadrant is two-fold. (a) First, if the action items on this are accomplished by the date expected, it automatically forces the belt in a positive way to lean on his mentor. This would indirectly make the review meetings, training, and other exercises more exciting as they go back to a management that is responsive and totally supportive. (b) Secondly, the subsequent review would be very effective by merely looking at the past action items and any new issues that needs to be addressed.
The critical philosophy of this four-block is that for a successful session, the belt needs to spend about 5 % of their time on the “status” quadrant and the rest on the remaining. In many cases due to no fault of their own, they end up talking about the “status” 95 % of the time and by the time they get to the action items, the management is not energized enough to take decisions on the action item. Thus in a 10 minute review session, take about a minute or two on the “Status” part and devote the rest on the remaining three quadrants. Get the sponsor, functional leader, and site leader to sign off on the action items and communicate via e-mail to document the process.
This is not a meeting to discuss difficulties in project coordination or the details of project technicalities. Issues that could not have been resolved by the secondary level of management that the Belt would have to deal with would qualify for approval at this meeting
The “Status” quadrant refers to displaying the appropriate status of the project. This means a mean/stdev status or associated project accomplishments in terms of ppm can be displayed. This would raise the attention of the management on what the issues are at hand to get the project moving if there is a gap.
The “Needs” quadrant refers to specifically listing the needs in 3 or more primary areas, such as resources, budget, and timeline in order to improve the project “status.” Once the needs of the project are met, the status has to move in the right direction. Without any negative implications, this has to be point specific, that the management comes out with a “yes,” “no,” or “maybe” by the latest within a week prior to the next review. Use escalation policy here if needed.
The “Issues” quadrant refers to a direct consequence of not meeting the needs by the expected time. This usually gets the attention provided it is validated by the team at the appropriate level of management. This quadrant leads the management immediately into, “what do we need to do to get this project accomplished?”
The “Action Items” quadrant is the kicker and it deals with the highest level of commitment from the management top-down. The other advantages of this quadrant is two-fold. (a) First, if the action items on this are accomplished by the date expected, it automatically forces the belt in a positive way to lean on his mentor. This would indirectly make the review meetings, training, and other exercises more exciting as they go back to a management that is responsive and totally supportive. (b) Secondly, the subsequent review would be very effective by merely looking at the past action items and any new issues that needs to be addressed.
The critical philosophy of this four-block is that for a successful session, the belt needs to spend about 5 % of their time on the “status” quadrant and the rest on the remaining. In many cases due to no fault of their own, they end up talking about the “status” 95 % of the time and by the time they get to the action items, the management is not energized enough to take decisions on the action item. Thus in a 10 minute review session, take about a minute or two on the “Status” part and devote the rest on the remaining three quadrants. Get the sponsor, functional leader, and site leader to sign off on the action items and communicate via e-mail to document the process.
