Electrical Safety and Quality Management PDF

EE E05 ELECTRICAL SAFETY AND QUALITY MANAGEMENT Objective: The objective of the course is to introduce IE rules and its significance, electrical safety in residential, commercial and industrial installations. It also helps the students to know about the electrical safety in during installation, tes...

EE E05 ELECTRICAL SAFETY AND QUALITY MANAGEMENT Objective: The objective of the course is to introduce IE rules and its significance, electrical safety in residential, commercial and industrial installations. It also helps the students to know about the electrical safety in during installation, testing and commissioning, operation and maintenance. Besides, it enables the students to know more about the quality management. 1.1 TERMS AND DEFINITIONS: 1. Accident. An unpleasant, unexpected, unforeseen or unintended happening sometimes resulting from negligence, that results in injury, loss, damage, etc. and is caused by a mistake or machine failure or natural disaster, or sabotage. Accidents may cause ‘Mishap, ruin, destruction, injury, death’. Accidents must be prevented by precautions and safety measures and safety management. 2. Danger. A thing or situation which may cause ‘injury, loss, accident, etc’. Such a thing or situation is ‘dangerous’, risky. 3. Hazard. To expose to, ‘danger, risk, chance of accident’. Hazardous. ‘Dangerous, risky, accident prone’. 4. Safety. A quality or condition of being safe from ‘danger, injury, damage, loss, accident’. Safe. Free from ‘injury, damage, accident, loss’ 5. Safety Devices. Devices which ensure safety against injury or loss. e.g. safety belt, Safety glasses, safety Earthing, Safety enclosure, Safety fence. 6. Safe Guard. Any person or thing or devices that prevents injury, loss and ensure, safety and security. 7. Security. State of sense or safety protection or defense against attack, interference, espionage, sabotage etc. Protection. Safeguard. 8. Precaution. Care or measure taken beforehand against possible danger. 9. Caution. (1). A word or sign by which warning is given (2) Act or practice of being cautious. 10. Prevent. To anticipate beforehand and stop from happening. 11. Preventive. Anything that prevents. 12. Prevention. Act of preventing, Means of preventing. Prevent accidents, shocks, burns, flashovers. Save life and property 13. Appliance. Electrical device which performs specific task {e.g. stove, iron, shaver, heater.) 1.2 OBJECTIVES OF SAFETY AND SECURITY MEASURES  To establish Safety Management System, Safety Audit System.  To achieve 100% safety and 100% security of Installations Equipment, Human Life and Animal Life.  To bring awareness about safety hazards and safety rules  To Educate personnel.  To understand Cause and Effect relationship in accidents and scientific phenomena associated with electricity.  To control the situation and prevent accidents, injury and loss to human life, installations and  property.  To minimize loss in case of accident.  To ensure prompt first aid and emergency help in case of accident.  Study of unsafe acts and unsafe conditions leading to accidents. To take corrective measures to eliminate them. 1.3 HAZARDS ASSOCIATED WITH ELECTRIC CURRENT AND VOLTAGE Persons working with electrical appliance/equipment/installation are exposed to following Hazards. The electricity is invisible, hence the hazards are ‘Hidden’ and ‘Invisible’. 1. Electric Shock. Due to direct contact with live wire/conductor, while standing on earth or while in contact with metallic earthed part. 2. Electric Shock. Due to direct contact with non-effectively earthed metal part carrying leakage current or fault current or induced currents.  3. Electric Shock and Burn Injuries: due to flashovers from live part to the person in contact with earth or earthed metallic-parts. 4. Shocks by capacitive charged electrical conductors disconnected from power circuit e.g. capacitors, bus bars. (H.V. circuits should be discharged after switching-off). 5. Falling of persons from height due to shocks or flashovers while working on overhead structures. Falling or persons in uncovered trenches, man-holes. 6. Falling of overhead parts such as conductors, hardware, structure members, on body. 7. Falling of tools, objects, welding-sparks, on body. 8. Explosion of oil filled equipment due to internal arcing. (Transformers, CTs, Bushings, Circuit breakers). Explosion of high pressure gas filled equipment (Circuit breakers). 9. Fires caused by electric loose connections, electric arcs, electric short-circuits, electric flashovers Fires quickly spread and cause deaths due to burn injuries and release of poisonous gases. Fires cause loss to property/installation. Fires are caused by: — Loose connections in power circuit. — Loose connection in auxiliary circuit. — Loose connection at terminals. — Breaking of conductors. — Over heating of conductor and burning of insulation. — Welding of oil-filled equipment. — Electric faults in oil filled equipment. — Electric arcs or faults in equipment having inflammable materials. — Static electric charges, discharged through sparks. — Lightning discharge. — Flashovers. 10. Release of poisonous liquids/gases. e.g. release of arced SF6 gas from circuit breaker during maintenance, release of synthetic fluids from capacitor cans. 11. Natural disasters such as lightning strokes, earthquakes land-slides. 12. Manmade disasters such as sabotage, bombing. 13. Short-circuits caused by snakes, birds, rodents. 14. Explosions or Accidents associated with high power rotating machines due to leakage of cooling medium, mechanical resonance, failure of mechanical parts. 15. Injury due to contact with rotating machine (fan, coupling) or moving mechanical parts of mechanisms. 16. Sparks in electrical equipment installed in explosive atmosphere (mines). 17. Mechanical Accidents due to failure of electrical controls/interlocks/protections/machine or structure component. Vehicle accident (crane, car, lifter). 1.4 WHO IS EXPOSED? Electric field is Invisible and Silent. Persons who approach bare high voltage conductors or encroach in high electric field are exposed to the danger of shocks and electrocution. Persons touching non- effectively earthed, faulted metal parts in electrical installations are exposed. Persons working in substations, power stations, transmission line, cables etc. are exposed. Persons unaware of electricity and carrying out the work in the vicinity of live parts are exposed. In general the following types of personnel are exposed to the hazards of electricity  General Construction worker not related with electrical works but working in the installation and moving in electric field.  Electrical technicians, fitters, Supervisors etc. working with electrical installations equipment for erection, testing, commissioning, operations, maintenance..   Machine operators.  Parsons handling electrical equipment, appliance, devices.  Persons in substations, commercial buildings, residential buildings etc. are exposed to hazards of fires caused by electricity.  From Safety angle, the persons exposed to electrical hazards are :  Innocent persons who are not aware about electricity but have some other work in the danger zone. Such persons are usually cautious and stay away from live parts.  Persons who work in electrical installations and have grown accustomed to working and tend to be overconfident, careless and negligent. Such persons are prone to serious accidents.  Cautious and well-trained persons working in electrical installations are exposed to dangers due to ‘mistake of others’ or faulty/unsafe equipment of situation, for example : supply is switched on while maintenance is in progress. Whereas effect of shock is felt by only a few persons, the effects of fire caused by electric sparks, short-circuits, insulation failure etc. can cause large scale destruction of property and life. The sequence is : Many unsuspecting innocent personnel are subjected to injury due to fires and smoke. 1.5 PRINCIPLES OF ELECTRICAL SAFETY Electrical Safety is concerned with accidents occurring due to electricity. Each electricity accident is caused by certain unsafe act/ acts by a person/persons and/or unsafe conditions. The accidents must be prevented by effective Safety Management. Accidents/Incidents must be investigated and analyzed. Preventive actions/Conditions must be enforced to avoid similar and other accidents. The basic principles have been reviewed. 1. Unsafe Acts and Unsafe Conditions. Each electrical accident is caused by certain unsafe acts and/or unsafe conditions. Behind one accident there are several “chance misses”. 2. Each accident should be followed by inspection and investigation to identify and pinpoint the unsafe acts, unsafe conditions responsible for the accidents and recommend corrective actions to avoid similar accidents in future. Many of the accidents can be prevented by enforcing Safety Management Systems. 3. For example consider and accident caused by placement of a ladder near Live. The inspection and investigation resulted in identification of following act/condition. The Unsafe Act. Placement of ladder near live bus in High Voltage Switchyard. The Unsafe Condition. Entry in high voltage switchyard with ladder The Corrective Action. Switchyard to be provided with fence, gate, lock, entry only against work permit issued after making busbars dead. The studies of H.W. Heinrich, the pioneer safety engineer, resulted in a well known Heinrich Ratios (88 : 10 : 2) as under : Causes of Accident: Unsafe acts : 88% Unsafe condition : 10% Other unsafe causes : 2% The Heinrich Ratios were widely accepted in the middle of the 20th century. During 1990’s the correctness of these ratios has been questioned. Safety Management Systems have received higher emphasis. By effective Safety Management, root causes behind accidents are eliminated at the root itself. 4. Multiple Causes. Behind every electrical accident, there are causes and sub causes. The investigations should bring-out clearly the various causes and subcauses and recommend corrective action against each cause and sub cause. This will help in eliminating similar and other accidents in future. For example consider the case of accident cause by placement of ladder near live busbars. The accident occurred in a 400 kV switchyard during minor repair work of lighting-maintenance. Following causes and sub cause were identified during the investigations. Switchyard had no fence. The person carrying ladders could walk-in and place the ladder near live bus — The person carrying ladder was uneducated, untrained and of low IQ. — The supervisor instructed the persons to carry the ladder and place it near the structure. However the person placed it near the live bus. The supervisor gave unsafe instructions. — Safety procedures were by-passed by the supervisor due to negligence. — Work permit system was not established by the Management. Corrective Actions — Fencing to switchyard with gate and lock. — Work permit system established to ensure opening of gate only after making the busbars dead/earthed. — Safety training to supervisors and workers. 5. Unsafe conditions can be identified in advance and their harmful effects can be controlled. Unsafe conditions associated with electricity and electrical installations are : — High Voltage installations and equipment. — Erection at high rise levels. — Storage of inflammable materials. — High pressure gas filled equipment. — Equipment filled with transformer oil. Causes of an accident include ‘proximate causes’ and ‘prime-cause’ Prime Cause of an accident can be attributed to weakness in Safety Management System of organization. Management’s policies, organization and procedures, supervision and its effectiveness, human resource development in safety systems have strong influence of Safety. 6. Questioning Attitude. The function of Safety is of concern to everyone. The following questions are helpful in identifying unsafe acts/conditions which may lead to an accident. — What can cause accidents ? — What is the possible root cause and what are possible proximate causes that may lead to various accidents ? — How can the situation be controlled to prevent the possible accidents ? How can the root causes be eliminated ? 1.6 SCOPE OF SUBJECT ‘ELECTRICAL SAFETY’ Electrical Safety deals with safety from electricity, supply system, electrical appliances, plant, and equipment. Very large energy flow can occur rapidly during electric fault. Electrical Safety deals with safety of personnel, installations, plants, equipment and property. Electrical Safety covers safety aspects of installation/ equipment design, testing, erection commissioning, maintenance activities as well as Safety Management. The subject matter deals with : — Causes and effects of electrical hazards. — Scientific Phenomena associated with electrical safety. e.g. Electric Shocks, Electric Fields, Flashovers, Hazards, Electric Explosions etc. — Safety Acts and Safety Rules, Safety Habits. — Specifications and Design for safety. — Training in Safety. — Safety during Project Construction. — Safety during Plant Operation and Maintenance — Safety Management. Safety Organization. — Safety Documentation, Systems. — Safety Audit and Safety Inspection. — Safety devices and safety tools. — Live line maintenance.  — Plant Quality, Product Quality and TQM. — First Aid and Facilities. — Loss prevention measures. — Fire prevention and Fire Fighting. — Security measures. — Investigations and analysis of Accidents/Mishaps. — Insurance coverage and procedures. — Electrical Safety has a strong interface with General Safety, Industrial Safety & TQM UNIT I REVIEW OF IE RULES AND ACTS AND THEIR SIGNIFICANCE Objective and scope– ground clearances and section clearances– standards on electrical safety safe limits of current, voltage–Earthing of system neutral –Rules regarding first aid and fire fighting facility. 1.8 INDIAN ELECTRICAL RULES AND INDIAN ELECTRICAL ACTS  IE act was first started in 1903 and then amended in 1910 and in 1948.  IE rules were first framed in 1922 and amended in 1937 and 1956.  IE acts and IE rules are amended from time to time to keep pace with changing scenario of electrical technology. OBJECTIVES AND SCOPE OF IE ACT AND IE RULES OBJECTIVES:  To regulate the relation between the electricity superior and consumer.  To make the generation, distribution and use of electricity as safe as possible. Responsible persons regarding IE rules & IE acts: 1) Supplier 2) The owner or the consumer 3) Electrical inspector 4) Electrical contractor or supervisor 5) Authorized person PROVISIONS: The IE Act 1910 and IE Act 1948 has following provisions : 1. To provide for issue of licenses and sanction to the Electric Supply Companies and regulate their working. 2. To provide for efficient supply of Electricity to consumers. 3. To provide for the appointment of the Electrical Inspector to administer the Act and the rules that may be framed under the Act. 4. To provide for the Constitution of the State Electricity Board and the Generating Company and to lay down their powers and duties. 5. Creation of Central Electricity Authority to regulate the functioning of the State Electricity Board and the Generating Companies. 6. To regulate the rates of the Electricity Sold by Supply Companies and Licenses. IE Rules (1922, 1937, 1956) cover safety requirements of various classes of electrical plants, installations and equipment and define the scope of Electrical Inspectors. IE Rules have a wide coverage with total eleven chapters. Table 1.1 gives the summary of Eleven chapters in IE rules: CHAPTER I Preliminary Data, Definitions and terms used, authorization to persons to work on electrical installations, etc. CHAPTER II Appointment of Electrical Inspector, his qualification, experience, power of Electrical Inspector to enter the premises and to serve order for removal of defects, provision of appeals against the order of Electrical Inspector etc. CHAPTER III Procedure for application of a License. CHAPTER IV General Rules applicable for all class CHAPTER V Electrical Installations (LV to EHV). CHAPTER VI Rules applicable to Low Voltage and Medium Voltage Installations. CHAPTER VII Rules for High-Voltage and Extra High voltage Installations. CHAPTER VIII Rules for Overhead Transmission Lines. CHAPTER IX Rules and provision for Electric Tractions. CHAPTER X Rules and provision for Electrical Equipment and Installations in Mines and Mine Fields. CHAPTER XI Power of Govt, and powers of Electrical Inspector to relax certain provision of rules, mode of entry and penalty for breach of rules have been discussed in this chapter. 1.9 CLASSIFICATION OF ELECTRICAL INSTALLATIONS The electrical installations are classified on the basis of Nominal rated voltage as : 1. Low Voltage Electrical Installation (LV or LT). Where the voltage does not exceed 250 volts under normal conditions. LT refers to Low Tension. 2. Medium Voltage Electric Installation (MV). Where the voltage exceeds 250 volts but does not exceed 650 volts under normal conditions. 3. High Voltage Electrical Installation (HV or HT). Where the voltage exceeds 660 volts but does not exceed 33000 volts under normal conditions. 4. Extra High Voltage Electrical Installation (EHV), Where the voltage exceeds 33000 volts under normal conditions.  Electrical Installation of the above categories comprises of transformer, sub-station, Switchgears, Operating devices, Panel Boards, Electric Motors, Portable Equipment, Pumps, Lights, Fans, Ventilation Systems, Air conditioning System, Auxiliary Electrical Distribution Power Cables, etc.  The classification LV, HV, MV, EHV, as per Indian Electrical Rules differs from classification of CIRED and general terminology in transmission and distribution.  As per IEC and CIRED classifications, the term Low Voltage (LV) applies to voltages upto and including 1000 V, Medium Voltage applies to voltages above 1000 V and upto and including 36 kV, High Voltages (HV) includes all voltages above 36 kV. Including and upto 245 kV, and EHV applies to voltages above 245 kV.  The Voltages refer to phase to phase RMS values of Sinusoidal AC voltages of standard frequency of 50 Hz.  Each voltage level has three values of voltages: (1) Nominal Voltage, (2) Highest Voltage, (3) Lowest Voltage. Significance of Voltage Class: The voltage levels are standardized. With each voltage level, the highest system voltage and lowest system voltage values are also specified. The power supply company has to ensure that the voltages at various points in the system are within the specified limits. The equipments are designed to withstand the highest system voltage continuously without failure. The insulation levels of each equipment have a reference to the rated voltage of the equipment. Thus, the voltage class is important with reference to insulation requirements of the plant and equipment. The clearances, creepage distances, test voltages and safety precautions to be taken increase progressively with higher voltage class. For example, voltage stresses are low in LV systems and high in HV systems. The LV systems are generally used for domestic and commercial lighting loads. And loads up to above 250 kVA MV system are used for Industrial and Power Plant auxiliaries and distribution systems. Rated up to about 2 MW. The nominal system voltage is for reference and operational target. However, during regular operation of the electrical system, the system voltage varies with changes in the load and changes in the flow of reactive power. By effective voltage control, the system voltages are held within specified limits. These limits are in terms of Highest System voltage and Lowest System Voltage. Thus each voltage level in the system has following voltage values 1. Nominal System Voltage 2. Highest System Voltage 3. Lowest System Voltage 1.10 GROUND CLEARANCES AND SECTION CLEARANCES: Clearances and their significance: The term clearance denotes the clear distance between two conducting points along stretched string. Important clearances include the following: 1.Phase-to-Earth Clearance: It is the clearance between live conducting part and neighboring earthed parts or ground. 2.Phase-to-phase-Clearance: It is the clearance between live parts of different phase. 3. Isolating Clearance : It is the minimum distance along a stretched string between the two sides of an open isolator pole. 4. Work Section and Section Clearance: Certain minimum clearance should be provided to prevent flashovers during transient over voltages under worst atmospheric and pollution conditions. The various standards recommend the minimum clearances in air for outdoor installations and indoor enclosed installations. These recommendations serve as a guide for equipment designers and substations designers.  5.Ground Clearance. The distance between the uppermost earthed metallic point (on structure or tank) and the ground level (on which person stands) is called Ground Clearance. Such a clearance is essential for safe distance between raised finger of a man standing on the ground near the equipment structure/tank and the uppermost earthed point. If such a ground clearance is not available, fence/earthed/guard/screen-fence must be provided around the equipment and entry in the enclosed fence area should be prohibited. Table 1.3. Minimum air clearance values in substations as per I.E. Rules Rule 64(2), phase to earth and sectional clearances to be maintained for H.V. and E.H.V. installations have been introduced in 1987, are as follows; VOLTAGE CLASS PHASE TO EARTH CLEARANCES SECTIONAL CLEARANCES Not exceeding 11 KV 2.75 2.6 Not exceeding 33 KV 3.70 2.8 Not exceeding 66 KV 4.00 3.0 Not exceeding 132 KV 4.60 3.5 Not exceeding 220 KV 5.50 4.3 Not exceeding 400 KV 8.00 6.5 Ground Clearance (Minimum): 2.55 m. Minimum Ground Clearance (2.55 m) is specified on the basis of height of a tall man’s raised finger tip and the ground. User may provide ground clearance of 2.8 m or 3 m, or even more to perint movement of vehicles, tools carried by persons etc. without encroaching in phase to ground clearance. 1.11 METALLIC EARTHED FENCE FOR SWITCHYARDS. Switchyards have busbars mounted on insulators and structures, CTs/VTs, Isolators, Surge Arrestors etc. mounted on structures, Power Transformers mounted on foundations. Switchyards must be provided with metallic earthed fence of minimum 1.8 m height. Equipment which are not mounted on earthed, galvanized steel structures of 2.55 m height must be provided with additional earthed metallic fence of 1.8 meter height. The metallic fence has sections of 3 to 4 meter length around the entire perimeter of the switchyard. Earthing bars of Earthing system are laid outside the fence along the entire perimeter and the individual fence sections are connected to the Earthing bar ring by welding smaller Earthing strips/bars with the welded joints per section of the fence. Consecutive fence sections are connected to each other by steel strips/clamps bolted on either sides. IE. Rule 68. In case of outdoor type sub-station a metallic fencing of not less than 1.8 metres height shall be erected around transformer, and/or entire switchyard. 1.12 CLEARANCES BETWEEN LOWEST POINT OF CONDUCTOR AND GROUND FOR TRANSMISSION LINES AND DISTRIBUTION LINES Transmission lines and distribution lines have conductors which have natural sag. The sag is maximum at mid span. The sag is maximum during summer and peak loads. When the sag is maximum, the mid span clearance is minimum. Certain minimum mid-span line conductor to ground clearance must be provided to ensure that vehicles of normal height can pass under the line without flashover. Table 1.4 gives the summary' of I.E. Rules for line to ground clearance. Table 1.4. I.E. Rules regarding Conductor to Grounds Clearance for overhead transmission lines Minimum Span Conductor To IE RULE CONDITION Class of Line Ground Clearances 1) Across a street 5.8 m LV to MV 2) Along a street 6.1m HV 3) Anywhere else (bare 5.5m, LV &MV conductor) 5.8m HV RULE 76 4.6m LV,MV,HV Upto 11 KV 4) Anywhere else (insulated 4.0m LV,MV,HV Upto 11 KV conductor) 5.2m HV & above 11 KV 5) Anywhere else not near 6.1 EHV road 1) Line near building with LV&MV Vertical 2.5m RULE 79 the roof or inclined roof 2) Building to line LV & MV Horizontal 1.2m 1) Line near to the HV line HV Vertical 3.7m 33KV line 2) EHV lines above 33KV EHV Vertical 3.7m +0.3m/each RULE 80 33KV Horizontal 11KV to 1.2m, 3.3KV to 2m and above 33KV Rule 77 and 82 specify the clearance for the service lines, electric transmission and distribution lines at various voltages. Rule 82 specify the procedure to be adopted for construction of any building structure addition, alteration or elevation of roads etc. In the vicinity of any electric line. 1.13 EARTHING OF EQUIPMENT BODIES, STRUCTURES TANKS AND OTHER NON-CURRENT CARRYING METALLIC PARTS IN ELECTRICS PLANTS All non-current carrying metallic parts in electric plant must be connected to the station Earthing system for ensuring safety against shock. Such Earthing is essential safety requirement of every electric installation The IE Rules regarding Equipment Earthing are summarized in Table 1.5 Table 1.5. Summary of IE Rules for Equipment Earthing IE Rule No. Description of Rules The supplier of electricity shall provide Earthing terminal at consumer’s premises to Rule 33 which the Earthing system in consumer’s installation shall be connected. The consumer should protect the Earthing terminal against damage. Rule 36 Lines should be disconnected and earthed before handling.  Separated and distinct Earthing terminal and earth connection shall be provided for Rule 51 to 61 every non-current carrying metallic part associated with electric plant equipment, lines cable. Rule 66 Guard wires shall be earthed Earthed guard wires shall be provided below HV and LV Line conductors. Rule 88 Earthed guard wire shall be provided between power line conductor (HT or LT) and Telecommunication lines. Rules 107 Traction Guard wires shall be earthed All metal fittings all support, all support, structure for line, stay wires, metal parts in Rule 90 electric apparatus shall be earthed unless they are mounted on insulator at appropriate height and distance from touch point. Surge arrestor Earthing terminals shall be connected by a separate Earthing strip to Rule 92 station Earthing system and with additional Earthing electrodes connected to the Earthing terminal. Frames of every stationary and portable electric motor, metallic parts of transformer Rule 61(2) and every other electric apparatus shall be earthed by two separate and distinct earth connections to underground Earthing system. All metal casings and metallic covers containing electrical supply lines and apparatus Rule 61(3) shall be connected to earth ensuring continuous good mechanical and electrical connection of entire length and breadth with the earth. All non current carrying metals part in mines and mine fields shall be earthed. The Rule 115,117 methods of Earthing in mine are specified in Rule 115. 45 Penalty for damaging public lamps 46 Penalty for negligently using energy 47 Penalty for offences not otherwise provided for 48 Penalties for not to affect other liabilities 49 Penalties where works belong to Government Offences by companies : If the offence is committed by company aggrieved by the 49A offence can only institute prosecution against the person responsible for offence and breach of section, Rules or Condition of supply as the case may be. 1.14 ELECTRICAL SAFETY-GENERAL REQUIREMENTS AS PER IE RULES Summary of Rules^8^30', 31 to 36, 41, 45, 46, 64, 77, 79, 80 is given in this section. These rules have important bearing on safety. Rule 29 : Construction, installation, protection, operation and maintenance of electric supply lines and apparatus All electric supply lines and apparatus shall be of sufficient ratings for powers, insulation and estimated fault current and of sufficient mechanical strength, for the duty which they may be required to perform under the environmental conditions of installation, and shall be constructed, installed, protected, worked and maintained in such a manner as to ensure safety of personnel and property. Rule 30: Service lines and apparatus on consumer’s premises The supplier shall ensure that all electric supply lines, wires, fittings, and apparatus belonging to him or under his control which are on a consumer’s premises are in a safe condition and in all respects fit for supplying energy and the supplier shall take due precautions to aviod danger arising on such premises from such supply lines, wires, fittings and apparatus. Service lines placed by the supplier on the premises of a consumer which are underground and which are accessible shall be so insulated and protected by the supplier as to be secured under all ordinary conditions against electrical, mechanical, chemical or other injury to the insulation. The consumer shall, as far as circumstances permit, take precautions for the safe custody of the equipment on his premises belonging to the supplier. The consumer shall also ensure that the installation under his control is maintained in a safe condition. Rule 31: Cut out on consumer’s premises The supplier shall provide a suitable cut out in each phase of every service line other than an earthed or earthed neutral conductor or the earthed external conductor of a concentric cable within a consumer’s premises, in an accessible position. Such cut-out shall be contained within an adequately enclosed fireproof receptacle. Where more than one consumer is supplied through a common service line, each such consumer shall be provided with an independent cut out at the point of junction to the common service. Rule 32: Identification of earthed and earthed neutral conductors and position of switches and cut outs therein Where the conductors include an earthed conductor of a two wire system or an earthed neutral conductor of a multiwire system or a conductor which is to be connected thereto, the following conditions shall be complied with: An indication of a permanent nature shall be provided by the owner on the earthed or earthed neutral conductor, or the conductor which is to be connected thereto, to enable such conductor to be distinguished from any live conductor. Such indication shall be provided: (a) Where the earthed or earthed neutral conductor is the property of the supplier, at or near the point of commencement of supply. (b) Where a conductor forming part of a consumer’s system is to be connected to the supplier’s earthed or earthed neutral conductor, at the point where such connection is to be made. No cut out link or switch other than a linked switch arranged to operate simultaneously on the earthed or earthed neutral conductor and live conductors shall be inserted or remain inserted in any earthed or earthed neutral conductor of a two wire system or in any conductor connected thereto with the following exceptions : (a) a link for testing purposes or (b) a switch for use in controlling a generator or transformer. Rule 33 : Earthed terminal on consumer’s premises The supplier shall provide and maintain on the consumer’s premises for the consumer’s use a suitable earthed terminal in an accessible position at or near the point of commencement of supply. Provided that in the case of medium, high or extra high voltage installation the consumer shall in addition to the afore mentioned earthing arrangement, provide his own earthing system with an independent electrode. The consumer shall take all reasonable precautions to prevent mechanical damage to the earthed terminal and its lead belonging to the supplier. Rule 34 : Accessibility of bare conductors Where bare conductors are used in a building the owner of such conductors shall: (a) ensure that they are inaccessible (b) provide switch in readily accessible position for rendering them dead whenever necessary. Rule 36 : Handling of electric supply lines apparatus Before any conductor or apparatus is handled adequate precautions shall be taken by earthing or other suitable means to discharge electrically such conductor or apparatus and any adjacent conductor or apparatus if there is danger therefrom and to prevent any conductor or apparatus from being accidentally or inadvertently electrically charged when persons are working thereon. No person shall work on any live electric supply line or apparatus and no person shall assist such person on such work unless he is authorized in that behalf and takes the safety measures. Every telecommunication line on supports carrying a high or extra high voltage line shall, for the purpose or working thereon be deemed to be a high voltage line. Rule 41: Distinction of different circuits The owner of every generating station, sub-station, junction box or pillar in which there are any circuits or apparatus, shall ensure by means of indication of a permanent nature that the respective circuits are readily distinguishable from one another. Rule 42 : Accidental charge The owner of a circuits and apparatus shall so arrange them that there shall be no danger of any part thereof becoming accidentally charged to any voltage beyond the limits of voltage for which they are intended. Where A.C. and D.C. circuits are installed on the same support they shall be so arranged and protected that they shall not come into contact with each other when live. Rule 45: Precautions to be adopted by consumers, owners, electrical contractors, electrical workmen and suppliers No electrical installation work, including additions, alterations, repairs and adjustments to existing installations except such replacement of lamps, fans, fuses, switches, low voltage domestic appliances and fittings as in no way alters its capacity or character, shall be carried out upon the premises of or on behalf of any consumer, owner or occupier, for the purpose of supply to such consumer or owner except by an electrical contractor licensed in this behalf by the State Government and under the direct supervision of a person holding a certificate of competency issued or recognised by the State Government. Rule 46: Periodical inspection and testing of consumer’s installation Where an installation is already connected to the supply system of the supplier, every such installation shall be periodically inspected and tested at intervals not exceeding five years either by the Inspector or any officer appointed to assist the Inspector or by the supplier as may be directed by the State Government in this behalf. Rule 64 (2): The following provisions shall be observed where energy at high or extra high voltage is supplied converted, transformed or used. (а) Clearances as per Indian Standard Code shall be provided for electrical apparatus so that sufficient space is available for easy operation and maintenance without any hazard to the operating and maintenance personnel working near the equipment and for ensuring adequate, ventilation. (b) The following minimum clearances shall be maintained for bare conductors or live parts or any apparatus in outdoor sub-stations, excluding overhead lines, of HV and EHV installation: Ground clearance Sectional clearance Voltage class (Metres) (Metres) Not exceeding 11 kV 2.75 2.6 Not exceeding 33 kV 3.7 2.8 Not exceeding 66 kV 4.0 3.0 Not exceeding 132 kV 4.6 3.5 Not exceeding 220 kV 5.5 4.3 Not exceeding 400 kV 8.0 6.5 (c) Where transformer or transformers are used, suitable provision shall be made, either by connecting with earth a point of the circuit at the lower voltage or otherwise, to guard against danger by reason of the said circuit becoming accidentally charged above its normal voltage by leakage from or contact with the circuit at the higher voltage. (d) A sub-station or a switch station with apparatus having more than 2000 litres of oil shall not be located in the basement where proper oil draining arrangement cannot, be provided. (e) Where a sub-station or a switch station with apparatus having more than 2000 litres of oil is installed, whether indoors or outdoors, the following measures shall be taken, namely: The baffle walls of 4 hour fire rating shall be provided between the apparatus in the following cases : (i) single phase banks in the switchyards of generating stations and sub-stations. (ii) on the consumer premises 0iii) where adequate clearance between the units is not available. (/) Adequate fire protection arrangement shall be provided for quenching the fire in the apparatus. (g) Cable trenches inside the substations and switch stations containing cables shall be filled with sand, pebbles or similar non-inflammable materials or completely covered with non- inflammable slabs. All EHV apparatus shall be protected against lightning as well as against switching over- voltage. The equipment used for protection and switching shall be adequately co-ordinated with the protected apparatus to ensure safe operation as well as to maintain the stability of the interconnected units of the power system. The following additional provisions shall be observed where energy at high or extra high-voltage is supplied, converted transferred or used namely : Rule 64 A(l): Interlocks Suitable inter-locks shall be provided in the following cases : (а) Isolators and the controlling circuit breakers shall be interlocked so that the isolators can not be opened unless the corresponding breaker is in open position. (b) Isolators and the corresponding earthing switches shall be interlocked so that no earthing switch can be closed unless and until the corresponding isolator is in open position. (c) When two or more supplies are not intended to be operated in parallel, the respective circuit-breakers or linked switches controlling the supplies shall be interlocked to prevent possibility of any inadvertent paralleling or feed back. (d) When two or more transformers are operated in parallel, the system shall be so arranged as to trip the secondary breaker of a transformer in case the primary breaker of that transformer trips. (e) All gates or doors which give access to live parts of an installation shall be interlocked in such a way that these cannot be opened unless the live parts are made dead. Proper discharging and earthing of these parts should be ensured before any person comes in close proximity of such parts. (f) When two or more generators operate in parallel and neutral switching is adopted, interlock shall be provided to ensure that generator breaker cannot be closed unless one of the neutrals is connected to the earthing system. Rule 64 A(2): Protection All system and circuits shall be so protected as to automatically disconnected the supply under abnormal conditions. The following protection shall be provided, namely а) Over current protection to disconnect the si. pply automatically if the rated current of the equipment, cable or supply line is exceeded for that length of time which the equipment, cable or supply line is not designed to withstand. (b) Gas pressure type protection to give alarm and tripping shall be provided on all transformers of ratings 1000 kVA and above. (c) Transformers of capacity 10 MVA and above shall be protected against incipient faults by differential protection and all generators with rating of 100 kVA and above shall be protected against earth fault/leakage. All generators of rating 1000 kVA and above shall be protected against faults within the generator winding using restricted earth fault protection or differential protection or by both. In our country as well as in our State (M.P.) also most of the distribution mains are over-head. In the past, it has been observed that good number of accidents have taken plane due to improper clearance from ground to line and from building to overhead line. As per Indian Electricity Rule 1956, the following clearances have been specified which are as below : Rule 77. Clearance above ground of the lowest conductor No conductor of an overhead line, including service lines erected across a street shall or any part thereof be at a height less than : (a) for low and medium... 5.8 metres voltage lines (b) for high voltage lines... 6.1 metres No conductor of an overhead line including service lines, erected along any street shall or any part thereof be at a height less than: (а) for low and medium... 5.5 metres voltage lines (b) for high voltage... 5.8 metres No conductor of an overhead line including service lines erected elsewhere than along or across any street shall be at a height less than : (a) for low, medium and... 4.6 metres high voltage linos upto and including, 11,000 volts, if bare (b) for low, medium and... 4.0 metres high voltage line upto and including, 11,000 volts if insulated (c) for high voltage lines... 5.2 metres above 11,000 volts. For extra high voltage lines the clearance above ground shall not be less than 5.2 metres plus 0.3 metre for ever 33,000 volts or part thereof by which the voltage of the line exceeds, 33,000 volts. Provided that the minimum clearance along or across any street shall not be less than 6.1 metres. Rule 79 : Clearance from buildings of low and medium voltage lines and Service lines Where a low or medium voltage overhead line passes above or adjacent to or terminates on any building, the following minimum clearances from any accessible point on the basis of maximum sag, shall be observed: (а) For any flat roof open balcony, verandah roof and lean-to- roof (i) when the line passes above the building a vertical clearance of 2.5 metres from the highest point and («) when the line passes adjacent to the building a horizontal clearance of 1.2 metres from the nearest point. (b) For pitched roof-when the line passes above the building a vertical clearance of 2.5 metres immediately under the lines and when the line passes adjacent to the building a horizontal clearance of 1.2 metres. Rule 80: Clearance from building of high and extra high voltage lines Where a high or extra high voltage overhead line passes above or adjacent to any building or part of a building it shall have on the basis of maximum sag a vertical clearance above the highest part of the building immediately under such line of the not less than: (a)For high voltage lines... 3.7 metres upto and including 33.0 volts (b)For extra high voltage... 3.7 metres plus 0.30 metre lines for every additional 33,000 volts or part thereof. The horizontal clearance between the nearest conductor and any part of such building shall on the basis of maximum deflection due to wind pressure be not less than : (а) For high voltage line... 1.2 metres upto and including 11.0 volts (b] For high voltage lines... 2.0 metres above 11,000 volts and upto and Including 33.0 volts (c) For extra high voltage... 2.0 metres plus 0.3 metre lines for every additional 33,000 volts or part thereof. Even after these clear rules, every year there are about 80 to 90 fatal accidents/non fatal accidents, due to improper clearance and lack of supervision from Electricity Board Authority and Electrical Inspectorate Authorities. It has been observed that although proper clearance has been maintained as per Indian Electricity Rules while constructing the buildings, but during the course of construction of the second storey, there have been cases of fatal electrical accidents, while putting the M.S. Bar for slab. Actually, length of these M.S. Bars is always ten to fifteen metres, and while making them straight and putting for slab they touch the over head lines passing about 8 to 10 feet away from the building causing fatal electrical accidents. 1.15 SIGNIFICANCE OF EQUIPMENT EARTHING AND EAR THING OF NON-CURRENT CARRYING METALLIC PARTS Non current which are not at high potential with respect to earth and which are normally near earth potential may give shock to operation and maintenance personnel or general public due to — leakage current through poor insulation, — induced current in metallic part due to vicinity with power circuit, , — dielectric charges in the capacitance associated with those metal parts. By providing Earthing to such metal parts (which are not at high potential and which are not in the power circuit or auxiliary circuit) that part is held at ground potential and following advantages are obtained. Earthing of non current carrying metallic parts (at low potential with respect to earth) ensures : — The earthed part is at earth potential and therefore safe to touch — Leakage current are discharged to earth — Induced current are discharged to earth — Capacitive charge are discharged to earth — Protective-gear / fuse operate in the event of earth fault. — 1.16 EARTHING OF SYSTEM NEUTRAL Three phase AC System has three phase supply and three phase loads. The star point of 3 phase generator windings and three phase transformer windings (HT or LT) are also called Neutral Point or System Neutral. Under balanced supply and load condition the three phase voltage are equal in magnitude and displaced by 120° (electrical) mutually. Likewise three phase current vectors are equal in magnitude and at 120° (electrical) mutually. Neutral Point should be earthed at least at one star point at each voltage level at source-end. Connection of star point of 3 phase AC system to earth (station Earthing system) is called System Neutral Earthing. The system natural Earthing is different in purpose than the equipment Earthing (safety Earthing), However both deal with connecting a metallic point to Earthing system. All three phase AC power systems of today operate with grounded neutrals. In some continuous process industries unearthed systems are used, however higher insulation levels are necessary for such systems. Neutral grounding offers several advantages. The neutral points (star point) of generator, transformer system., circuit, rotating machines, etc., and star points of CT secondary circuit and VT Secondary Circuit are connected to earth either directly or through a resistance or a reactance. In some cases the neutral point is earthed through an adjustable reactor of reactance matching with line to earth capacitance of a line. The neutral Earthing is one of the most important features of system design. In every substation, neutral grounding important because : — Neutral of 3 phase AC system must be held at earth potential to ensure balance 3 phase AC supply. By neutral Earthing. The neutral remains at earth potential even though phase currents may be slightly unbalanced. — Earth fault protection becomes simpler. Earth fault current flows through neutral and operates earth fault relay or earth fault fuse. Arcing grounds are minimized or eliminated. ‘Arcing grounds’ are small phase to grounds arcs due to repeated charging and discharging of phase to grounds capacitance through air gaps. By neutral grounding, the return current through neutral is in phase opposition with capacitive arcing currents. Hence arcing grounds are eliminated and voltages are stabilized — Star points of CT and VT secondary’s are earthed to ensure proper balanced currents/voltages on secondary side for proper measurement, protection, control of 3 phase AC system. Transient lightning surges and switching surges are discharged to earth through neutral Earthing. Neutral Earthing plays an important role in the insulation Co-ordination of power system.In ungrounded neutral systems, higher class of insulation should be provided for each equipment and plant {e.g. 33 KV class insulation for 22 kV class equipment/plant) to prevent insulation failure during earth fault anywhere in the system at that voltage level. Neutral Grounding Practice 1. Generally one neutral ground is provided at each voltage level.  Between generator voltage level and distribution voltage level there are several voltage levels. One ground is provided at each voltage level. Note. Flow of steady third harmonic current or induced current through neutral wire is possible if two different neutral points at same voltage level are connected to each other directly through neutral wire or two neutral points at same voltage level are connected individually to earth. Hence only one neutral point at every voltage level is earthed to avoid steady induced current flow through neutral. 2. The grounding is provided to source end and not at load end. 3. Each major bus section provided with grounded neutral. Voltage Grounding type Below, up to 660 V Solid Between 3.3 kV and 11 kV Low resistance or Reactance 22 kV and above Solid. 4. Star Point CT Secondary is earthed. Star point of VT secondary is earthed. NEUTRAL GROUNDING IMPORTANCE: 1) Ensure balance 3 phase supply. 2) Earth fault becomes simpler. 3) Arcing grounds are minimised or eliminated. 4) Lightening and the switching surges was discharged. 5) Star point of the C.T and V.T secondary’s are earthed to ensure proper balanced currents and voltages on system side 6) Find insulation coordination of power system. ADVANTAGES OF NEUTRAL GROUNDING: 1) The voltages of the healthy line with the respective earth remain at harmless value during single line fault on third phase. 2) They do not increase to the normal value as in the case of ungrounded system. 3) Arcing grounds due to the discharge of the capacitive comments through the repeated sparks are eliminated operation or maintenance personnel. 4) Stable neutral point. 5) The earth fault protection becomes simple. 6) Creates a safety to personnel and equipments. 7) The over voltages due to the lightening are discharged to the earth. 8) Life of the equipments, machines, installation was improved due to the limitation of the over voltage, and hence overall economy. 9) Earth fault can be located in the grounded neutral system. 10) Safety persons operating the electrical equipments working in the plant carrying out maintenance are not subjected to the shocks due to the eliminations of arcing grounds. 1.16 RULES REGARDING FIRST AID AND FIRE FIGHTING FACILITY:  The owner of the construction site or plant site should provide the first aid facilities & fire fighting facility.  Rule no.44 &45 requires the first aid box, buckets and the fire extinguishers. The authorized person is required to the trained in first aid resuscitation. RULE 43: FIRST AID BOX AND FIRE PROTECTION  First aid box must be kept at every work place. The location must be displayed and shown to every working member. RULE 44: FIRE EXTINGUISHER FACILITY FOR FIRE PROTECTION  Sand buckets and portable fire extinguisher must be provided at the each risk zone in each plant. 1.17 FUNDAMENALS OF FIRE: Fire is the rapid combustion resulting in release of the heat and light of the flame. Fire is an active, rapid, burning process accompanied by the heat, light and poisonous gases or smoke or gases due to the combustion  It is started or ignited or begun at o hot spot and spread the combustible material to neighbouring area subject to the availability of air, heat and the local temperature. CAUSES OF FIRE:  1) Electric arcs, flashovers and short circuits. 2) Corona discharge. 3) Loose connection resulting sparks. 4) Welding sparks. 5) Hot resistors. 6) Bursting of capacitor cones. 7) Arcs due to the static charges. 8) Switching surges. TYPES OF FIRE: 1) Class A 2) Class B 3) Class C 4) Class D& E FIRE EXTINGUISHER TECHNIQUE: 1) Cooling 2) Water 3) Ventilation 4) Smothering Fire extinguishing media, 1) Water 2) Co2 3) Foam 4) Dry chemicals 5) Halon  Fire risk can be minimized by the good house keeping, adequate control during the civil work and the plant equipment design, storage, installing, commissioning activities.  The precautions are listed in the safety documentation. The risk is further reduced. Insurance coverage is essential for every plant and the conditions of insurance policy must be satisfied for fire safety and fire protection TYPES OF FIRES According to European and US Standards, Fires are classified into five classes : A, B, C, D, E on the basis of the material involved in the fire. The type of fire extinguishing technique recommended differs with the Class of Fire. Water is used as quenching medium for Class A fires. Water is not suitable for Class B, Class C, Class E fires. Table. Classification of Fires as per European Standards Fire Material Involved Fire Extinguishing Medium Class Fires involving Ordinary Solid Materials Water or Solution with high water Class A such as Wood, Coal, Plastics, Cloth, Paper, content Cooling and wetting of Fire Rags, Rubbish, Construction and Packing material helps in quenching the fire materials, Rubber, etc. Fires involving Flammable Liquids/ Vapours/Solvents : Transformer oil, Diesel Limiting air or oxygen supply, Class B oil, Solvents, Liquid chemicals Lubricating inhibiting fire Dry chemicals, Foam, Fire oils, Paints/Varnishes/thinners Greases, Halon. Water is not suitable. Contained/Uncontained. Fires involving live Electrical Equipment, in CO2 gas, Dry chemicals. Water in Class C Fire Energized state. If equipment is dead Class is not suitable. A or B. Normal extinguishing media not Fires involving Metals like magnesium, Class D Fire suitable. Special chemicals and titanium. techniques are used.  Fires involving Flammable Gases and Fuels Starvation of fire is most useful. Class E Hydrogen, Ammonia, Acetylene, LPG, Special methods necessary inlet Fire Petrol, Furnace oil value closed. 1.18 FIRE-EXTINGUISHING TECHNIQUES Fire is initiated by ignition and sustained by simultaneous supply of three essentials: heat, oxygen and material of combustion, Fire extinguishing techniques/aim at rapidly removing one/two or all the three essentials. Cooling is removal of heat. Smothering is removal of oxygen supply. Starving is removal of combustible material supply. Breaking / Interrupting Chain reaction is separating combustible material from ongoing fire. Triangle of Extinction Fig. Triangle of fire extinguishing. Cooling. Cooling is removal of heat. Temperature of fire zone and combustion zone must be reduced below ignition temperature rapidly so that fire does not sustain. Rate of cooling must be higher than the rate of heat generated by combustion. Water is the most commonly used coolant for class A fires. Only condition being: Electrical Supply should be disconnected and the electrical machines/system must be made dead, earthed so that the cooling water does not conduct electricity/give shock the firemen and does not create short circuits. Only after cooling the combustible material, the extinction of fire can be achieved. Ventilation (Release of Heat) helps in cooling and fire extinction. Slab above fire zone is deliberately ruptured to release heat to atmosphere. Smothering (Blanketing). Smothering is suffocating the fire by external covering it completely by dense blanket of extinguishing medium (CO2, Foam, Halon, Water etc.). Smothering of fire aims at “Oxygen Starvation” of fire. By combination of Cooling and Smothering, the fires can be certainly extinguished. Smothering is useless when the combustion of material releases oxygen on its own (e.g. Cellulose Nitrate). Starvation. Fire is starved by stopping the supply or removal of combustible material, and filling dry nitrogen gas. For example, Gas Fires can be stopped by closing of gas inlet valve at supply end. Oil fire can be stopped by closing inlet valve of oil supplying pipe. Tank containing oil can be drained and emptied to stop the supply of oil to fire. Nitrogen can be filled quickly in the pipe/tank. Blowing off the flame and dilution of flame are also forms of “starving”. By blowing of flame the gas is moved away faster so that flame cannot sustain. A Class fire is usually blown to safer area and extinguished. Water soluble liquid fires can be extinguish by dilution of the combustible liquid by water. The combustible liquid gets diluted and fire cannot sustain as water is non-combustible. Oxygen Starvation can be achieved by increasing C02 concentration in the surrounding dome around the fire. Oxygen Starvation can also be achieved by Nitrogen or SF6 gas envelope/filling. Breaking Chain Reaction of Fire. Fire continues in the form of chain reaction. Fresh combustible material receives heat from adjacent burning material and thereby fire continues. Dry chemicals or Halogenated hydrocarbons are used for breaking chain reaction of fire. However other techniques of cooling and smothering and starvation must also be used. Table Check List For Fire Prevention Actions  Description and Desirable Feature Check Storage for Inflammable Materials — Fire Safety Document Issued or not ? — Fire protection system in ready state or not ?+ — Separate store for each inflammable material — Firewall between store and other parts — Good spark-proof wiring — No permission for Smoking and Flames — Good housekeeping, No rubbish kept — Safety audit conducted ? — Security — Lightning Protection — Storage according to recommendations Storage of Equipment/Spares — Fire Safety Document Issued or not ?+ — Fire protection system in ready state or not ?+ — Insurance coverage obtained and valid ?+ — Good spark-proof wiring — Separate store for transformer oil — No permissioned for Smoking and Flames — Good housekeeping, No rubbish kept — Fire protection — Good security — Lightning Protection — Storage according to recommendations Civil Works Fire Safety Document Issued or not ? Fire protection system in ready state or not ?+ Good housekeeping, No rubbish kept Precaution while Welding Good construction Use of fire retarding materials Follow fire safety-recommendations Good quality wiring Compartmentisation of rooms/ducts Provision of Fire walls, fire escapes, fire hydrants, raw-water systems, fire station, etc. Installation Work Fire Safety Document Issued or not ? Fire protection system in ready state or not ?+ Welding with care No welding of oil filled tanks No loose connections in temporary wiring Supervision during drying out of transformers Field Quality Checks for current carrying paths to ensure low resistance Field Quality Checks on Gas Filled and Oil Filled Equipment, Chemical piping for leakless joints Field quality checks on Electrical Clearances Field Quality Checks on Cooling Systems Field Quality Checks on Fire Fighting Systems Testing, Commissioning Work Fire Safety Document Issued or not ? Fire protection system in ready state or not ?+ Field Quality Tests on Equipment, Protection Systems, Cooling Systems Field Quality Tests on Cooling Systems Field Quality Tests on Fire Fighting System Precautions while testing oil Filled Equipment: Presence of Fire Engine Commission checks under close supervision. Operation Fire Safety Document Issued or not ? Fire Protection system in ready state or not ?+ No overload beyond permissible limit Supervision of temperature rise Supervise control boards carefully at regular intervals. Keep log book records. Inspect plant carefully at regular intervals. If any smoke ? any overheating ? any burning smell ? any abnormal sound ? any leakage ? any bearing overheating ? Attend to leakages, abnormal sounds, operational snags, abnormal conditions promptly. Follow safety rules for Operation Maintenance  Document for Maintenance of Fire Protection system is issued and followed or not  Fire protection system in ready state or not ?  Follow planned Inspection and Periodic Preventive Maintenance and Test Plan  Current Carrying parts to be inspected for tightness of joints, hardware and there are  no burning/overheating marks.  Sharp corners should be removed,  Any decolouration should be investigated.  Insulators should be cleaned.  Cooling system should be maintained.  Transformer oil should be maintained  Auxiliaries, Protection Systems, Interlocks, Battery systems, Ventilation and Air  Conditioning systems must be maintained.  Fire protection system must be maintained  Conduct mock-trial of Fire Event for Operation and Maintenance Staff  Maintain Lighting System, Wiring, Switchboards, Fuse gear etc.  Maintain Switchgear and Protective Systems STEPS AFTER OCCURRENCE OF FIRE  Fire Occurs  Fire is Detected by Observer or Detection System Alarm is Sounded  Electric Power Supply and Other Fuel Supplies are Switched Off  Immediate Use of Portable Fire Extinguishers and Water/Sand for Extinguishing Small Fires then and there  Automatic Fire Fighting System Gets Initiated  Call Fire Brigade  Persons vacate the place CARBON DIOXIDE FIRE EXTINGUISHERS Carbon Dioxide (C02) is effective extinguishing agent primarily it reduces the oxygen content of air to a point where combustion cannot continue. C02 is non combustible and does not react with most substances. Being a gas it can penetrate and spread to all areas affected by fire. Carbon Dioxide fire extinguishers are used for putting out fires in oils, petroleum products, gaseous substances under pressure, and also on electronic apparatus. Carbon Dioxide extinguishers are not to be used in : (i) Fires involving chemicals that contain their own oxygen supply (such as cellulose nitrate). (it) Fires involving reactive metals such as sodium, potassium and magnesium. The common type of portable carbon dioxide extinguisher covered by IS : 2878-1976 is discussed here. Construction. The principal parts of extinguishers are, as.shown in Fig. 13.6 figure above. Carbon Dioxide is retained in the cylinder as liquid under pressure. The cylinder is filled with the charge to about two-thirds by weight of its total water capacity. Method of Operation. Take extinguisher to the place of fire. Remove the safety pin operate the discharge device or unscrew the valve depending on the design. Carbon dioxide is delivered by means of discharge horn through a high pressure flexible hose. Project the hose to the base of the fire, starting at one edge and sweeping across the surface of the burning material. When used in open air, the operator should stand on the up-wind side of the fire. < fires in electrical equipment first switch off the current. Then < Direct the jet or horn straight at the fire. The gas at the time of discharge makes considerable noise. The user should therefore be well conversant with its operation to prevent the jet from being misdirected during the first few vital Seconds PRINCIPLE OF CARBON DIOXIDE EXTINGUISHER When the extinguisher is actuated carbon dioxide from the cylinder comes out at a considerable velocity into the atmosphere and forms a layer of gas which is about one and a half times heavier than air. The vapour blanket puts out fire and reducing the oxygen supply needed to continue combustion  Total Fire Protection Systems includes — Fire Detection Systems — Fire Alarm Systems — Fire Alarm and Control Panel — Fire Hydrant System — Monitoring System Fire Fighting Systems include 1. Water Spray System (Sprinkler System) 2. C02 Systems 3. Dry Chemical Powder (DCP) Systems. 4. Foam Systems 5. Halon Systems The choice of System/systems for particular zone depends on the type of equipment and extinguishing medium to be used FIRE DETECTION AND ALARM SYSTEM Smoke indicates presence of fire. Flame and light and heat confirm the presence of fire. Fire must be detected rapidly and the zone of fire must be indicated on fire-control panel at earliest. Fire should be quenched before it grows. Fire is detected by fire detection system comprising fire detectors. The fire detectors are located in various zones of the power plant/substations and are connected to the fire alarm and fire control panel located in the control room and to the Automatic fire fighting system distributed in the plant. The detection of smoke/flre, sounding of alarm and initiating the Fire Extinguishing Action can be achieved by various methods. Fire Detector System initiates Fire Alarm System. Fire Alarm/Control Panel is installed in.Control Room of the Power Plant/Substation. The operation of a fire detector is immediately indicated and Buzzer is sounded on the respective Zone—Window of the panel. The function of alarm system are to sound fire alarm send signals to fire brigade and indicating zone of fire. The fire alarm is initiated by the fire detectors. Depending upon the design features and specifications, the functions of fire detection and alarm system include one or more of the following : — To detect smoke, fire and sound alarm, siren, warning indication of fire control panels and warn personnel abound occurrence of smoke/fire and its location by sounding alarm/horn.  — To initiate operation of automatic fire fighting system in the affected zone — To initiate operation of Deluge Valves and to admit water through projectors — To initiate tripping of circuit breakers feeding power to electrical plants in the affected areas, via fire control and relay panel. 1.19 SAFE LIMITS OF CURRENT & VOLTAGE: 1) Electric shock: due to the direct contact with the live wire. 2) Due to the flashovers. 3) Falling of person due to the shocks or flashover. 4) Shock by the capacitive changed electrical conductors. 5) Explosion of oil filled equipment. 6) Fires caused by:  Loose connections in power circuit.  Loose connection in auxiliary circuit. 7) Natural disasters 8) Explosions 9) Short circuits caused by the snakes, birds etc 10) Injury due to the contact with the rotating machine. 11) Mechanical accidents due to the failure of electrical controls CAUSES OF ACCIDENTS: 1) Unsafe act: 88% 2) Unsafe condition: 10% 3) Other unsafe causes: 2% 1.19 STANDARDS ON ELECTRICAL SAFETY Standards for electrical safety It specifically addresses working in restricted areas; working near exposed energized overhead lines or parts; operating equipment near radio and microwave transmission towers; working on electrical equipment and systems; personal protective grounding; temporary wiring; disconnect and overcurrent protection; ground-fault protection; hazardous locations; wet locations; and battery charging. General Electrical Safety Requirements All electrical work practices must comply with applicable sections of the Occupational Safety and Health Administration (OSHA), National Fire Protection Association (NFPA), National Electrical Code, National Electrical Safety Code, and State adopted electrical codes. The following standards are some of the most important for electrical safety: A code is a document that contains only mandatory requirements. It uses the word shall and is cast in a form suitable for adoption into law by an authority that has jurisdiction. Explanations in a code must appear only in fine-print notes, footnotes, and appendices. A standard also contains only mandatory requirements, but compliance tends to be voluntary, and more detailed notes and explanations are given. A manual or guide is a document that is informative and tutorial but does not contain requirements.