Electrical maintenance work at the site should be done by specially trained and experienced persons who are aware of the danger that exists when working on or near live mains or apparatus. The safety equipment must always be in order. For this purpose, regular inspection and maintenance of the equipment is a must. We state below the safety procedures for the inspection of equipment.
Inspection of Safety Equipment
• All equipment used for working on overhead lines and apparatus should be surveyed every month by a responsible official and s/he should make random checks on the equipment to satisfy herself/himself that the equipment is in good condition.
• Special attention must be paid to the safety equipment such as safety belt,gloves, ropes used for hoisting, etc. as per schedule. Any replacement due to wear and tear should be made immediately.
• Every authorized person / in charge of a working party before commencing his/her work should ensure that all equipment being used is in safe condition and not weakened by deterioration, abrasion, etc. S/he should not permit the work to be carried out if, for any reason, s/he is in doubt that the equipment is unsuitable or deteriorated to the extent that it is likely to cause a hazard.The safety precautions for working on mains and apparatus for different voltage ranges are different and you must know about all of them. Here we describe them briefly. In each case only a competent and experienced person who is authorized to do so can be allowed to work. Such persons should take all safety measures as are required under the Indian Electricity Rules 1956.
A. SAFETY INSTRUCTIONS FOR WORK UP TO AND INCLUDING 650 V
• Work on dead mains and apparatus: All mains and apparatus to be worked upon should be isolated from all sources of supply before starting work.
• Work on live mains and apparatus: Safety Tags should be attached on or adjacent to the live apparatus and at the limits of the zone in which work may be carried out, immediately before starting work.Rubber gauntlets, if used, should be thoroughly examined by authorized person / user to see whether they are in sound condition.Under no circumstances should a person work with unsound gauntlets, mats, stools, platforms or other accessories and proper testing should be carried out as per manufacturer’s guidelines.
• Connecting dead mains to live mains: When dead mains are connected to live mains, all connections to the live parts should be made last, and in all cases the phases sequence should be checked to ensure that only like phases are connected together by testing Phase Sequence tester Rod and Phase Sequence Meter for HT and LT, respectively. Before inserting fuses or links in distribution pillar controlling the cable on which a fault has been cleared, each phase should first be connected through a test switch fuse lower than the
value of the load.
B. SAFETY INSTRUCTIONS FOR WORK AT VOLTAGES ABOVE 650 V
General
• All high voltage mains and apparatus should be regarded as live and a source of danger and treated accordingly, unless it is positively known to be dead and earthed.
• No person should work on, test or earth mains or apparatus unless covered by a permit to work and after providing the mains dead
except for the purpose of connecting the testing apparatus, etc. which is specially designed for connecting to the live parts.
• While working on mains, the following precautions should be taken:
−When any live mains is to be earthed, the prescribed procedure should be followed scrupulously.
Inspection of Safety Equipment
• All equipment used for working on overhead lines and apparatus should be surveyed every month by a responsible official and s/he should make random checks on the equipment to satisfy herself/himself that the equipment is in good condition.
• Special attention must be paid to the safety equipment such as safety belt,gloves, ropes used for hoisting, etc. as per schedule. Any replacement due to wear and tear should be made immediately.
• Every authorized person / in charge of a working party before commencing his/her work should ensure that all equipment being used is in safe condition and not weakened by deterioration, abrasion, etc. S/he should not permit the work to be carried out if, for any reason, s/he is in doubt that the equipment is unsuitable or deteriorated to the extent that it is likely to cause a hazard.The safety precautions for working on mains and apparatus for different voltage ranges are different and you must know about all of them. Here we describe them briefly. In each case only a competent and experienced person who is authorized to do so can be allowed to work. Such persons should take all safety measures as are required under the Indian Electricity Rules 1956.
A. SAFETY INSTRUCTIONS FOR WORK UP TO AND INCLUDING 650 V
• Work on dead mains and apparatus: All mains and apparatus to be worked upon should be isolated from all sources of supply before starting work.
• Work on live mains and apparatus: Safety Tags should be attached on or adjacent to the live apparatus and at the limits of the zone in which work may be carried out, immediately before starting work.Rubber gauntlets, if used, should be thoroughly examined by authorized person / user to see whether they are in sound condition.Under no circumstances should a person work with unsound gauntlets, mats, stools, platforms or other accessories and proper testing should be carried out as per manufacturer’s guidelines.
• Connecting dead mains to live mains: When dead mains are connected to live mains, all connections to the live parts should be made last, and in all cases the phases sequence should be checked to ensure that only like phases are connected together by testing Phase Sequence tester Rod and Phase Sequence Meter for HT and LT, respectively. Before inserting fuses or links in distribution pillar controlling the cable on which a fault has been cleared, each phase should first be connected through a test switch fuse lower than the
value of the load.
B. SAFETY INSTRUCTIONS FOR WORK AT VOLTAGES ABOVE 650 V
General
• All high voltage mains and apparatus should be regarded as live and a source of danger and treated accordingly, unless it is positively known to be dead and earthed.
• No person should work on, test or earth mains or apparatus unless covered by a permit to work and after providing the mains dead
except for the purpose of connecting the testing apparatus, etc. which is specially designed for connecting to the live parts.
• While working on mains, the following precautions should be taken:
−When any live mains is to be earthed, the prescribed procedure should be followed scrupulously.
The earths and short circuits, specified on the permit to work should not be removed or interfered with except by authority from
the person in charge of the work.
Minimum Working Distance
No person should work within the minimum working distance from the exposed live mains and apparatus. The minimum working distance
depends upon actual voltages.
• Exposed live equipment in the vicinity should be guarded off and the guarding should be done in a manner so that it does not hinder the movement of the personnel. If necessary, a person for observing safety could be posted.
• All barriers, shutters, etc. of high voltage equipment should be kept locked except when required for carrying out work under a permit to work. The keys should be kept under the control of authorized persons only.
C. OPERATIONS OF SWITCHES AND ISOLATORS
General
• No high voltage switch, isolator or earthing switch should be operated or earth connection attached or removed without the sanction of an authorized person, except in the case of moveable earth connection on high voltage overhead lines, which may be fixed or moved by an authorized person under the direction of the permit to work, which authorizes him to carry out the work.
• When a switching operation has to be carried out, the authorized person should convey his/her instructions to the operating person detailed to carry out the operations. On receipt of the instructions, the operating person should notify the authorized person of any objections to the carrying out of such instructions; the authorized person should then decide whether the work is to proceed.
• The authorized person should immediately after this, inform the Power System Control of his instructions and the objections if any. The authorized person should also inform the same receiving station of the operations he is to perform just prior to carrying them out, with objections if any. The procedure for delivering the message and logging them should be carried out in all cases. The two messages should be checked by Shift in charge / Shift Officer of Grid / PSC and clearance given for carrying out the work, if in order. On completion the authorized person should report back to the grid station and perform operations according to the guide lines of Power System Control.
Emergency
In case of danger to life, switches may be opened without instructions but in no case must a switch be closed except with previous writteninstruction or special permission from an authorized person or when a switch trips on temporary faults, and then only twice in succession.
•When any operation is carried out in an emergency in case of grave danger without the permit to work being issued or without emergency authorization or in case of trapping due to temporary faults, the grid station from which supply is received should be informed as soon as possible and the message logged on the log sheet. The number of the message on the log sheet should be marked in the report of occurrence. Such messages should also be conveyed immediately to higher authorities or the person authorized by them on their behalf.
D. TESTING OF MAINS AND APPARATUS
• No person should apply test voltage to any mains unless he has received a permit to work and has warned all persons working on the mains of the proposed application of the test voltage. If any part, which will thus become alive is exposed, the person in charge of the test should take due precautions to ensure that the exposed live portion does not constitute danger to any person. It should also be ensured before the application of test voltage, that no other permit to work has been issued for working on this main.
• Authorization for Testing: When equipment is isolated from the mains supply for the testing, the official responsible may give sanction for the operation of switches, isolators, earthing switches, earth connections, etc. and for the application of testing supplies to the isolated section, without reference to her/him. The person in charge of the testing then becomes wholly responsible for the safety precautions within the isolated sections but no switch or isolator connecting any isolated sections to the main supply system should be operated without direct sanction of the responsible official except for purpose of obtaining testing supplies.
There are special devices for testing that the mains and electrical apparatus is dead. We describe them briefly in the Box .
the person in charge of the work.
Minimum Working Distance
No person should work within the minimum working distance from the exposed live mains and apparatus. The minimum working distance
depends upon actual voltages.
• Exposed live equipment in the vicinity should be guarded off and the guarding should be done in a manner so that it does not hinder the movement of the personnel. If necessary, a person for observing safety could be posted.
• All barriers, shutters, etc. of high voltage equipment should be kept locked except when required for carrying out work under a permit to work. The keys should be kept under the control of authorized persons only.
C. OPERATIONS OF SWITCHES AND ISOLATORS
General
• No high voltage switch, isolator or earthing switch should be operated or earth connection attached or removed without the sanction of an authorized person, except in the case of moveable earth connection on high voltage overhead lines, which may be fixed or moved by an authorized person under the direction of the permit to work, which authorizes him to carry out the work.
• When a switching operation has to be carried out, the authorized person should convey his/her instructions to the operating person detailed to carry out the operations. On receipt of the instructions, the operating person should notify the authorized person of any objections to the carrying out of such instructions; the authorized person should then decide whether the work is to proceed.
• The authorized person should immediately after this, inform the Power System Control of his instructions and the objections if any. The authorized person should also inform the same receiving station of the operations he is to perform just prior to carrying them out, with objections if any. The procedure for delivering the message and logging them should be carried out in all cases. The two messages should be checked by Shift in charge / Shift Officer of Grid / PSC and clearance given for carrying out the work, if in order. On completion the authorized person should report back to the grid station and perform operations according to the guide lines of Power System Control.
Emergency
In case of danger to life, switches may be opened without instructions but in no case must a switch be closed except with previous writteninstruction or special permission from an authorized person or when a switch trips on temporary faults, and then only twice in succession.
•When any operation is carried out in an emergency in case of grave danger without the permit to work being issued or without emergency authorization or in case of trapping due to temporary faults, the grid station from which supply is received should be informed as soon as possible and the message logged on the log sheet. The number of the message on the log sheet should be marked in the report of occurrence. Such messages should also be conveyed immediately to higher authorities or the person authorized by them on their behalf.
D. TESTING OF MAINS AND APPARATUS
• No person should apply test voltage to any mains unless he has received a permit to work and has warned all persons working on the mains of the proposed application of the test voltage. If any part, which will thus become alive is exposed, the person in charge of the test should take due precautions to ensure that the exposed live portion does not constitute danger to any person. It should also be ensured before the application of test voltage, that no other permit to work has been issued for working on this main.
• Authorization for Testing: When equipment is isolated from the mains supply for the testing, the official responsible may give sanction for the operation of switches, isolators, earthing switches, earth connections, etc. and for the application of testing supplies to the isolated section, without reference to her/him. The person in charge of the testing then becomes wholly responsible for the safety precautions within the isolated sections but no switch or isolator connecting any isolated sections to the main supply system should be operated without direct sanction of the responsible official except for purpose of obtaining testing supplies.
There are special devices for testing that the mains and electrical apparatus is dead. We describe them briefly in the Box .
E. WORKING ON CABLES
• Identification of Cables to be Worked Upon: A cable should be identified as that having been proved dead prior to cutting or carrying
out any operation which may involve work on or movement of the cable. A neon-contact indicating rod, induction testing set may be used for proving the cable dead. Simply with the help of neon-contact indicating rod, the cable should be checked after being switched off.
• Working on High Voltage Cable: Work on high voltage cables should be only permitted on receipt of the permit to work. In addition to the precautions taken, the person carrying out such work should be personally instructed on the spot by an authorized person who should
first satisfy himself/herself that the cable has been made dead, isolated and earthed and if possible, the switch controlling the cable drawn from the cubicle and suitable danger boards installed in position.
Box : Devices for Proving Mains and Apparatus Dead
• Identification of Cables to be Worked Upon: A cable should be identified as that having been proved dead prior to cutting or carrying
out any operation which may involve work on or movement of the cable. A neon-contact indicating rod, induction testing set may be used for proving the cable dead. Simply with the help of neon-contact indicating rod, the cable should be checked after being switched off.
• Working on High Voltage Cable: Work on high voltage cables should be only permitted on receipt of the permit to work. In addition to the precautions taken, the person carrying out such work should be personally instructed on the spot by an authorized person who should
first satisfy himself/herself that the cable has been made dead, isolated and earthed and if possible, the switch controlling the cable drawn from the cubicle and suitable danger boards installed in position.
Box : Devices for Proving Mains and Apparatus Dead
•Working on Underground Cables
− For isolation of cables, at least one set of disconnecting switches or fuses in every source through which the cables can be made
alive including leads to the cable of potential transformers should be opened and then the cable should be discharged to the earth.
− Cable route indicators should be provided and cable route records maintained. It would access the particulars of all underground
cables correctly in the vicinity of the faulty cable.
− Use of sharp edged crowbars or pick axes should be avoided during excavation while locating the faulty cable or laying new
cable.
− All the cables in the vicinity in the fault area should be exposed and identified to establish the identification of the faulty cable.− Before any high voltage joint of chamber is to be opened in circumstances where it is not desirable to spike the cables or earthing the joint or chambers, the authorized person should satisfy from cable route record and, if necessary, by approved
tests that the joint or chamber is associated with the particular cable which has been made dead and it is safe to work on it.
− Employees should not step on live cables even though those are insulated and enclosed in a lead sheath. Tools and materials should not be rested against the sheath of the cable.
F. WORKING AT A HEIGHT
Before any work is begun on any pole or tower of a high voltage overhead line, which is adjacent and parallel to any other high voltage overhead line with conductors “alive” or any pole or tower which supports, more than one set of high voltage conductors “alive” the following special precautions, in addition to the foregoing, should be taken in every case:
• The authorized person in charge of the work should ensure that each workman who is to work on the poles or towers is definitely informed and thoroughly understands on which set of conductors the work is to be carried out.
• A “red” flag / Caution Tape (or lamp at night) which are available with maintenance crew, should be displayed on the side of the pole or structure on which the conductors are “alive”.
• Work should not be performed on any higher position of tower / line when a line below is energized.
G. WORKING ON HIGH VOLTAGE APPARATUS AND OVERHEAD LINES
Work on high voltage apparatus: Before commencing any work of repairs, alterations, extensions, additions or cleaning of high voltage apparatus, the following operations should be carried out in sequence.
1. The apparatus or cable or transmission line should be switched out and isolated from all points of supply under the direction of the
authorized person.
2. The switches, isolators and control links should be locked in position by the keys provided for the purpose.
3. Safety Tags should be placed at all points where apparatus can be made alive.
4. All apparatus should be discharged to earth and efficiently connected to earth near all points from which supply could be connected to it or between such points and the place of the work. All earthing should be done by the approved methods. The earthing leads used for earthing should be of adequate cross section according to voltage levels to enable passage of the fault current without fusing. Safety Tags should be removed only by an authorized person.
5. Earthing should also be carried out at the point of work by means of temporary earths on each phase and in no case should the temporary earths be removed from two phases simultaneously while the work is being carried out.
H. WORKING ON LOWER PORTION OF TOWERS CARRYING LIVE LINES
Painting and other work on the lower portion of towers or supports carrying live lines, and above the anti-climbing device may be permitted under the permit to work card provided that suitable precautions are taken to ensure that all persons carrying out work are acquainted with the distinctive marks (caution order) that have been placed on the tower and the support. For this purpose all the towers and the supports should be distinctly marked either by colour or by other positive manner above which no operation should be carried out without making the line dead. Distinctive marking should be so provided that it is not possible to get nearer than a minimum distance of 6 feet from a live conductor.
I.WORKING ON DEAD LINES AND EQUIPMENTS
•Grounding of Lines and Equipments
− Before doing any work on dead lines or equipment where there is
a possibility of their becoming energized from any source, such line or equipment should be short circuited and grounded between
the location of work and all possible sources of energy.
− Conductors to be grounded should be checked for potential by an approved method before the ground is installed.
− Temporary grounding cables should be flexible stranded copper not less than No.10 and should be equipped with approved clamps
at each end.
− Grounding cables should be inspected before each use.
− When grounding lines or equipment, the connection to the ground should be made first and that to the circuit or equipment last. In
removing grounds, first remove the connection to the circuit or apparatus and then remove the ground connection. Insulated hot-sticks should be used in making the ground connection to the circuit or apparatus.
− Grounds should be placed on all phases even if work is to be carried out on one phase only.
− For work on the line, ground should be placed at nearest tower on each side of the point of work, but in no case should earths bemore than six spans apart. As an additional safety measure, if possible, in addition to above grounds, line should also be grounded on the tower where the work is to be carried out.
− When work is to be carried out on lines of all-insulated construction and grounding point is not provided at point of work, temporary
grounds should be connected at point of work to an efficient portable earth stake driven into the ground. The line should also
be grounded at the nearest line grounding point on either side of the point of work.
Line Work on Poles and Towers
− Before climbing any elevated structure, every employee should first assure himself that the structure is strong enough to sustain his weight safely.
− If poles or cross arms are apparently unsafe because of decay or unbalanced tensions of wires on them, they should be properly
braced or guyed before they are climbed.
1. The apparatus or cable or transmission line should be switched out and isolated from all points of supply under the direction of the
authorized person.
2. The switches, isolators and control links should be locked in position by the keys provided for the purpose.
3. Safety Tags should be placed at all points where apparatus can be made alive.
4. All apparatus should be discharged to earth and efficiently connected to earth near all points from which supply could be connected to it or between such points and the place of the work. All earthing should be done by the approved methods. The earthing leads used for earthing should be of adequate cross section according to voltage levels to enable passage of the fault current without fusing. Safety Tags should be removed only by an authorized person.
5. Earthing should also be carried out at the point of work by means of temporary earths on each phase and in no case should the temporary earths be removed from two phases simultaneously while the work is being carried out.
H. WORKING ON LOWER PORTION OF TOWERS CARRYING LIVE LINES
Painting and other work on the lower portion of towers or supports carrying live lines, and above the anti-climbing device may be permitted under the permit to work card provided that suitable precautions are taken to ensure that all persons carrying out work are acquainted with the distinctive marks (caution order) that have been placed on the tower and the support. For this purpose all the towers and the supports should be distinctly marked either by colour or by other positive manner above which no operation should be carried out without making the line dead. Distinctive marking should be so provided that it is not possible to get nearer than a minimum distance of 6 feet from a live conductor.
I.WORKING ON DEAD LINES AND EQUIPMENTS
•Grounding of Lines and Equipments
− Before doing any work on dead lines or equipment where there is
a possibility of their becoming energized from any source, such line or equipment should be short circuited and grounded between
the location of work and all possible sources of energy.
− Conductors to be grounded should be checked for potential by an approved method before the ground is installed.
− Temporary grounding cables should be flexible stranded copper not less than No.10 and should be equipped with approved clamps
at each end.
− Grounding cables should be inspected before each use.
− When grounding lines or equipment, the connection to the ground should be made first and that to the circuit or equipment last. In
removing grounds, first remove the connection to the circuit or apparatus and then remove the ground connection. Insulated hot-sticks should be used in making the ground connection to the circuit or apparatus.
− Grounds should be placed on all phases even if work is to be carried out on one phase only.
− For work on the line, ground should be placed at nearest tower on each side of the point of work, but in no case should earths bemore than six spans apart. As an additional safety measure, if possible, in addition to above grounds, line should also be grounded on the tower where the work is to be carried out.
− When work is to be carried out on lines of all-insulated construction and grounding point is not provided at point of work, temporary
grounds should be connected at point of work to an efficient portable earth stake driven into the ground. The line should also
be grounded at the nearest line grounding point on either side of the point of work.
Line Work on Poles and Towers
− Before climbing any elevated structure, every employee should first assure himself that the structure is strong enough to sustain his weight safely.
− If poles or cross arms are apparently unsafe because of decay or unbalanced tensions of wires on them, they should be properly
braced or guyed before they are climbed.
J. WORKING ON SWITCHING OPERATIONS
• Every message relating to the switching operations on the high voltage system should, wherever practicable, be written down. Every such message should be repeated in full to the sender to ensure that the message has been accurately received.
• A record of high voltage switching will be entered in station log.
• All breakers and isolators should bear lettering or sign boards to indicate the circuit they control.
• When releasing the electric circuits, breakers or equipment for work on them, the associated breaker and disconnecting switches should be opened in the following order:
− the breaker will be opened first.
− the isolator will be opened, but before operating the isolator, it should be made sure that the breaker is open.
• After opening isolators and air break switches, check carefully to see that all blades are in full open position.
• When lines and circuits are taken out of service, the breaker control circuit should be opened either by operating the opening device or by removing the control circuit fuses.
• If the circuit is controlled by automatic reclosing breaker, the reclosing mechanism should be made inoperative.
• Isolators should be closed in firm positive manner, using sufficient force to make full contact of blades.
• Before removing fuses, switches should be opened if provided.Removing fuses from inductive circuit carrying current without opening
the switch is hazardous.
K. WORKING IN SUBSTATIONS
• Safety Tags should be placed on all enclosures of high voltage equipment and wherever necessary warn persons of the presence of
high voltage equipment. Safety audits should be conducted from time to time.
• Gates in switchyard fences and doors to switch gear and other enclosures containing live equipment, or other hazards, should be kept
locked at all times except when Authorized Person has entered for working inside.
• Every message relating to the switching operations on the high voltage system should, wherever practicable, be written down. Every such message should be repeated in full to the sender to ensure that the message has been accurately received.
• A record of high voltage switching will be entered in station log.
• All breakers and isolators should bear lettering or sign boards to indicate the circuit they control.
• When releasing the electric circuits, breakers or equipment for work on them, the associated breaker and disconnecting switches should be opened in the following order:
− the breaker will be opened first.
− the isolator will be opened, but before operating the isolator, it should be made sure that the breaker is open.
• After opening isolators and air break switches, check carefully to see that all blades are in full open position.
• When lines and circuits are taken out of service, the breaker control circuit should be opened either by operating the opening device or by removing the control circuit fuses.
• If the circuit is controlled by automatic reclosing breaker, the reclosing mechanism should be made inoperative.
• Isolators should be closed in firm positive manner, using sufficient force to make full contact of blades.
• Before removing fuses, switches should be opened if provided.Removing fuses from inductive circuit carrying current without opening
the switch is hazardous.
K. WORKING IN SUBSTATIONS
• Safety Tags should be placed on all enclosures of high voltage equipment and wherever necessary warn persons of the presence of
high voltage equipment. Safety audits should be conducted from time to time.
• Gates in switchyard fences and doors to switch gear and other enclosures containing live equipment, or other hazards, should be kept
locked at all times except when Authorized Person has entered for working inside.
L. WORKING ON TRANSFORMER
1. When work is to be carried out on a transformer, both low and high tension breakers and isolators should be opened. Similarly, during isolation of transformers to which potential transformers are connected, such potential transformers should be isolated.
2. Before starting any work on a transformer installation, it is important to check carefully for back feed, abnormal voltage or other dangerous conditions. Unusual circuit conditions may exist which require special consideration.
3. Whenever transformers are replaced, the new transformer should be checked carefully for voltage, polarity and phase sequence before
taking into service.
4. Area should always be cordoned off and Safety tagging should be done prior to starting the job on the transformer.
M. WORKING ON CIRCUIT BREAKERS
For isolation purposes it should be ensured that
• Disconnecting switches on sides, control switches, relay trip blocking switches and compartments’ doors are open.
• Mechanical blocking, wherever necessary, to prevent unauthorized movement of the mechanism is installed.
• In OCBs trip-free feature should be blocked.
N. WORKING ON METAL CLAD, SWITCH GEAR AND CONTROL PANEL
• While working on manually operated panel mounted circuit breakers when the operating handle is on the front and the circuit breaker is on the rear of switchgear or on another panel, a danger notice should be placed on the handle.
• When the work is to be carried out on the bus bars spouts the following operations should be carried out:
O. WORKING ON OUTDOOR STRUCTURES
•Bus Bars
In isolating the point of work from supply, care should be taken to disconnect right points in case of sectionalized, and/or meshschemes of bus bars. Isolators/switches closing on the section of bus bars on which work is to be carried out should be locked in open position and the closing mechanism rendered inoperative.
Capacitors
− Every capacitor should be treated as hot until proved otherwise.Capacitors store energy and are not necessarily dead when disconnected from the line. Once charged, a capacitor may retain its charge for several hours after it has been disconnected.
− When a capacitor is to be worked on, first open all cutouts or disconnecting devices to the capacitor, then wait for at least five minutes for the internal resistors to reduce the voltage. Next, using the hot stick (discharge rod), short circuit and ground all terminals of the capacitors. These terminals should remain short circuited and grounded while work is being done on the capacitor.
− To bring the capacitor banks back into service, first remove the jumpers with hot sticks, and then close the cut-outs.
Q. WORKING ON PORTABLE LAMPS AND APPLIANCES
• Ensure that all portable appliances are provided with 3-pin plug and socket connections and the metal work of the apparatus is effectively earthed.
• Always use portable hand-lamps of the insulated safety type and provided with a rubber, plastic or wooden handle and wire-guard.
• Do not use a lamp in a metal holder fixed to the end of a loose flexible wire as a portable hand-lamp.
• Do not disconnect a plug by pulling the flexible cable or when the switch is ON.
• Do not plug in any portable lamp or apparatus before making sure that the switch is OFF and that the wall plug is properly inserted in the socket.
So far, we have explained to you the various safety procedures that have to be strictly followed while working with electrical mains and apparatus. You may like to review these procedures in real-life situations
1. When work is to be carried out on a transformer, both low and high tension breakers and isolators should be opened. Similarly, during isolation of transformers to which potential transformers are connected, such potential transformers should be isolated.
2. Before starting any work on a transformer installation, it is important to check carefully for back feed, abnormal voltage or other dangerous conditions. Unusual circuit conditions may exist which require special consideration.
3. Whenever transformers are replaced, the new transformer should be checked carefully for voltage, polarity and phase sequence before
taking into service.
4. Area should always be cordoned off and Safety tagging should be done prior to starting the job on the transformer.
M. WORKING ON CIRCUIT BREAKERS
For isolation purposes it should be ensured that
• Disconnecting switches on sides, control switches, relay trip blocking switches and compartments’ doors are open.
• Mechanical blocking, wherever necessary, to prevent unauthorized movement of the mechanism is installed.
• In OCBs trip-free feature should be blocked.
N. WORKING ON METAL CLAD, SWITCH GEAR AND CONTROL PANEL
• While working on manually operated panel mounted circuit breakers when the operating handle is on the front and the circuit breaker is on the rear of switchgear or on another panel, a danger notice should be placed on the handle.
• When the work is to be carried out on the bus bars spouts the following operations should be carried out:
O. WORKING ON OUTDOOR STRUCTURES
•Bus Bars
In isolating the point of work from supply, care should be taken to disconnect right points in case of sectionalized, and/or meshschemes of bus bars. Isolators/switches closing on the section of bus bars on which work is to be carried out should be locked in open position and the closing mechanism rendered inoperative.
Capacitors
− Every capacitor should be treated as hot until proved otherwise.Capacitors store energy and are not necessarily dead when disconnected from the line. Once charged, a capacitor may retain its charge for several hours after it has been disconnected.
− When a capacitor is to be worked on, first open all cutouts or disconnecting devices to the capacitor, then wait for at least five minutes for the internal resistors to reduce the voltage. Next, using the hot stick (discharge rod), short circuit and ground all terminals of the capacitors. These terminals should remain short circuited and grounded while work is being done on the capacitor.
− To bring the capacitor banks back into service, first remove the jumpers with hot sticks, and then close the cut-outs.
Q. WORKING ON PORTABLE LAMPS AND APPLIANCES
• Ensure that all portable appliances are provided with 3-pin plug and socket connections and the metal work of the apparatus is effectively earthed.
• Always use portable hand-lamps of the insulated safety type and provided with a rubber, plastic or wooden handle and wire-guard.
• Do not use a lamp in a metal holder fixed to the end of a loose flexible wire as a portable hand-lamp.
• Do not disconnect a plug by pulling the flexible cable or when the switch is ON.
• Do not plug in any portable lamp or apparatus before making sure that the switch is OFF and that the wall plug is properly inserted in the socket.
So far, we have explained to you the various safety procedures that have to be strictly followed while working with electrical mains and apparatus. You may like to review these procedures in real-life situations
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