Category: electrical Safety

Electrical Safety – Indian Standards In the field of electrical engineering, engineers and other professionals get exposed to electricity indirectly during generation, transportation, installation and usage. Such conditions might cause hazards if accurate safety measures are not taken. To promote the safety and the right usage of equipment, there are certain rules and regulations formulated by the Bureau of Indian Standards (BIS). BIS follows the following five principles − Safety Ease of use and adaptability Simple technology Value for money products Energy efficiency and environment BIS has published the following code of practice for public safety standards in order to promote the right to information, transparency and accountability in a proper manner to the public. Code of Practice for Electrical Wiring Installation IS − 732 (1989) Section − Electrical Installation Application − Design of installation, selection and erection of equipment, inspection and testing of wiring system Code of practice for Earthing IS − 3043 (1987) Section − Electrical Installation Application − Design, installation and calculation of Earthing system Lightning arrester for Alternating Current System IS − 3070 (1993) Section − Electro technical: Surge Arresters Application − Identification, ratings, classification and testing procedure of Arrester Let us now consider other important codes of practice established by BIS for the purpose of electrification. The codes are listed in the table below − General Requirements Sr. No. Standards & Application 1 IS:900 Installation and maintenance of Induction motors 2 IS:1271 Classification of insulating materials for electrical machinery 3 IS:1646 Fire safety of buildings (general) electrical installation 4 IS:1882 Outdoor installation of Public Address System (PAS) 5 IS:1886 Installation and maintenance of Transformers 6 IS:1913 General and safety requirements of electric lighting fittings 7 IS:2032 Graphical symbols related to electrical technology 8 IS:2274 Electrical wiring installations where system voltage is more than 658 volts 9 IS:3034 Fire safety of industrial buildings (Electrical generation and distribution stations) 10 IS:3072 (part-1) Installation and maintenance of switchgear where system voltage is less than 1000 volts 11 IS:3106 Selection, installation and maintenance of fuse where system voltage is less than 650 volts 12 IS:3638 Guide for gas operated relays 13 IS:3646 Practice for interior illumination 14 IS:3716 Guide for insulation coordination 15 IS:3842 Guide for electrical relays for AC system 16 IS:4004 Guide for lightening arrestors (non-linear ) for AC system 17 IS:4146 Guide for voltage transformers 18 IS:4201 Guide for current transformers 19 IS:5571 Selection of electrical equipment in hazardous area 20 IS:5572 Types of hazardous areas for electrical installations 21 IS:5780 Intrinsically safe electrical apparatus and circuit 22 IS:5908 Measurement of electrical installations in buildings Switchgear The following table lists down the codes of practice for the maintenance of switchgear − General Requirements Sr. No. Standards & Application 1 IS:375 Making and arrangement for switchgear bus-bars, main connections and auxiliary winding 2 IS:694(part-1) PVC insulating cables with copper conductors (where voltage is up to 100v) 3 IS:1248 Direct acting electrical indicating instruments 4 IS:2147 Degrees of protections for enclosures for switchgear and control gear (low voltage) 5 IS:2208 Guide for HRC fuse (up to 650v) 6 IS:3202 Guide for climate proofing of electrical equipment 7 IS:3231 Guide for electrical relays of power system protection 8 IS:4047 Guide for heavy duty air break switches and fuses for voltage less than 1000v 9 IS:4237 Requirements for switchgears and control gears for voltage up to 1000v 10 IS:5987 Selection of switches where voltage is up to 1000v 11 IS:335 Insulating oil for transformers and switch gear 12 IS:2516(part-1,sec-2) AC circuit breakers (Tests for the voltage range 1000v to 11000v) 13 IS:3427 Metal enclosed switch gear and control gear for voltage within 1000v to 11000v 14 IS:722 AC electricity meters for 415 volts 15 IS:1951 PVC sleeving for electrical works 16 IS:2516(part-1sec-1 & part-2sec2) AC circuit breaker (Tests for voltage within 1000v) 17 IS:2419 Guide for dimension of electrical indicating instruments Motor Control Centre (MCC) The following table lists down the codes of practice for the maintenance of Motor Control Centre − General Requirements Sr. No. Standards & Application 1 IS:1554(part-1) PVC insulated heavy duty electric cables for the voltage up to 1100v 2 IS:1822 AC motor starters of voltage less than 1000v 3 IS:2959 AC contactors of voltage less than 1000v 4 IS:3961(part-2) Recommended current ratings for PVC insulated and PVC sheathed cables 5 IS:5124 Installation and maintenance of AC induction motor starters within 1000v 6 IS:2959 Guide for AC contactors of voltage less than 1000v Invertors The following table lists down the codes of practice for the maintenance of invertors − General Requirements Sr. No. Standards & Application 1 IS:391 Mains transformers for electronic equipment Transformers The following table lists down the codes of practice for the maintenance of transformers − General Requirements Sr. No. Standards & Application 1 IS:335 Insulating oil for transformer and switch gear 2 IS:2026 Power transformers 3 IS:2099 High voltage porcelain bushings 4 IS:3637 Gas operated relays 5 IS:3639 Fitting and accessories for power transformers Motors The following table lists down the codes of practice for the maintenance of motors − General Requirements Sr. No. Standards & Application 1 IS:325 3-ph induction motors 2 IS:4691 Degrees of protection provided by enclosures for rotating machinery 3 IS:4722 Guide for rotating electrical machines Batteries The following table lists down the codes of practice for the maintenance of batteries − General Requirements Sr. No. Standards & Application 1 IS:1652 Guide for stationery cells and batteries, lead-acid type with plante positive plates Cables The following table lists down the codes of practice for the maintenance of cables − General Requirements Sr. No. Standards & Application 1 IS:1753 Aluminum conductors for insulated cables 2 IS:3961(part-2) Guide for current ratings for cable 3 IS:3975 Guide for mild steel wires, strips and tapes for armouring cables 4 IS:5819 Guide for short circuit ratings of high voltage cables 5 IS:5831 Guide for PVC insulation and sheath of electric cables Alternators The following table lists down the codes of practice for the maintenance of alternators − General Requirements Sr. No. Standards

Electrical Safety – Power System The power system consists of a three-stage network – generation, distribution, and transmission. The power system is responsible for the production of electricity with the help of energy such as coal and diesel. All the devices connected to the system such as a motor, circuit breaker, transformer, etc., fall under the umbrella of a power system. Components of a Power System There are six main components of a power system. Let us see what the components are − The Power Plant The place where power is generated and set for transmitted with the help of a transformer. Transformer Transmit electrical energy from one circuit to another. Transmission Line The power passes through the transmission line towards the substations. Substation Power is transferred to the distribution line through a medium. Distribution Line It comprises of low and medium level power lines that connect to the distribution transformer. Distribution Transformer From the distribution line, the electricity is distributed to consumers as per an appropriate value. Causes of Hazards Electrical hazards are recorded in thousands of number per year, which includes more than 30 fatality cases. Therefore, it is essential to stay away from electrical hazards. Several factors lead to electricity hazards. The factors are described below in brief − Faulty wiring Exposure to loose, frayed and naked wires possess a severe health risk. It is the responsibility of the worker to report cases for damage or faulty cable to the authority as soon as possible. The best way to avoid risk is to inform everyone about it and never try to deal if one is not legally authorized. Improper usage of equipment Practicing a safety approach for using electrical equipment is imperative. If a worker is not permitted and trained to use a particular electrical device, then he/she should avoid using it. Sometimes live equipment can seem dead and can cause a severe fatality. A worker should also avoid using electrical tools when on a suspended platform unless he/she is entitled to it. Overused outlets All electrical outlets have thresholds. After usage, an outlet starts to fray and poses a risk. When overused, an outlet begins to overheat or generates less power than usual. If a worker experiences an overheating or sparks from an outlet, then he/she must inform the authority rather than dealing with it him/herself. Exposure to liquid Water and all other liquids are a good conductor of electricity. Therefore, all workers should always try to keep their electrical equipment away from any liquid. Also, while using electric equipment, all workers must pat their hands dry to avoid any shock or burn. Need for safety Electrical hazards are something that should be taken seriously in a workplace. Every organization has to conduct an electrical safety programme for all their workers. Apart from informing them about the hazards, the workers should also take a safety workshop. Many workers in a workplace do not pay much heed towards electricity hazards. Some think that electrical related incidents are a part of life and some even believe that accidents can never happen to them. What makes it worse is that, some workers think that health risk is a part of their job and it cannot be avoided. Such type of careless attitude among employees results in more work-related injuries. To bring effective changes in worker’s perspective, a safety program is of paramount importance. Learning working make money

Electrical Safety – Earth Fault Protection We will now understand what Earth Fault Protection is. We will being by focusing on Earth Fault. Earth Fault Earth Fault is an inadvertent fault between the live conductor and the earth. When earth fault occurs, the electrical system gets short-circuited and the short-circuited current flows through the system. The fault current returns through the earth or any electrical equipment, which damages the equipment. It also interrupts the continuity of the supply and may shock the user. To protect the equipment and for the safety of people, fault protection devices are used in the installation. Earth Fault Protection Devices The devices give the tripping command to break the circuit when earth fault occurs. The fault current is restricted and the fault is dispersed by the Restricted Earth Fault Protection (REFP) scheme. Normally earth fault relay, earth leakage circuit breaker and ground fault circuit interrupter, etc. are used to restrict the fault current. Earth Fault Relay (EFR) It is a safety device used in electrical installations with high earth impedance. It detects small stray voltages on the metal enclosures of electrical equipment. The result is to interrupt the circuit if a dangerous voltage is detected. The EFR is protected against tripping from transients and prevents shock. The following figure shows the Earth Fault Relay − Earth Leakage Circuit Breaker The Earth Leakage Circuit Breaker detects the leakage current directly and prevents injury to humans and animals due to electrical shock. It is a voltage-sensing device and has recently been replaced by Residual Current Circuit Breaker (RCCB), which is a current sensing device. It is a special type of latching relay that is connected to the main power supply. When the fault current flows from live wire to the earth wire within the installation, the coil of ELCB senses the voltage and switches off the power. This requires a manual reset process to work again. The RCCB senses the leakage current and sends a signal to trip the system. Ground Fault Circuit Interrupter The Ground Fault Circuit Interrupter is a safety device to prevent an electrical accident when any faulty tool is plugged in. It is a fast acting circuit breaker to shut down the supply when the earth fault occurs within 1/40th of a second. It compares the incoming and outgoing current from the equipment along the circuit conductor. If there is any difference as little as 5 mA, GFCI restricts the current and trip quickly. GFCI does not help much with line contact hazards but protects from fire, overheating and destruction of wire insulation. Restricted Earth Fault Protection Scheme Let us consider a star winding transformer, which is protected by a Restricted Earth Fault Protection with EFR protecting device as shown in the figure below. The following image shows the Earth Fault Protection with EFR − When an external fault F1 occurs in the network, I1 and I2 flow through the secondary side of the CTs. The resultant of I1 and I2 will be zero. However, if an internal fault F2 occurs inside the protective zone, only I2 flows and I1 is neglected. The resultant current I2 passes through the earth fault relay, which senses the fault current and protects the restricted portion of winding. The fault current is approximately 15% more than the rated winding current. To avoid the magnetizing inrush current, the stabilizing current must be in series with the relay. Learning working make money

Do”s and Don”ts at a Glance Confusing a live equipment for a dead one is one of the major reasons that can result in an electrical accident. It is essential for an organization to train their workers properly to take appropriate precautions while operating machinery. Although, it is also the responsibility of a worker to work with extreme caution and abstain from hazardous situations as much as possible. The do”s for a worker In this section, we will learn about the actions that need to be performed by a worker. Before carrying out any task, make sure that the equipment is 100% dead and is in no condition to get energized at any stage of work. For proper caution, it is ideal to write down all the measures that you are going to take, on a control sheet. Reanalysis your written instructions, and if possible, you can discuss this with your supervisor or fellow workers. Always stick with the work instruction provided to you. Using a well-rated instrument is necessary. It is recommended that only good quality, insulated tools, probes, and prods are used. Working in the sequence is the key to a safe operation especially the switching sequences. Make sure you close the isolator first and then close the associated circuit breaker. While testing equipment, it is vital that you create a spacious exclusion area. While working in the field, it is your life that is at stake. So, you must take appropriate cautions while working. Before taking any risk, it is always recommended that you think of the repercussion and take adequate measures. If you found anyone is interfering with your way of work, then stop them politely. If a co-worker is working on your test area and following a wrong procedure, then insist him/her to follow the right method. Before starting your work, make sure that you draft a proper layout of all your equipment in proper order. Following a correct order will not only help you to provide a comfortable working position but also offer you other advantages such as − Provide ample of space to work Provide ease of accessibility to your equipment Allows you appropriate time and visibility to read your instructions Provide adequate light Provide you quick gateway during an emergency The don”ts for a worker In this section, we will see the different actions that should be avoided by a worker. Never try to reclose a circuit during a fault, when it is still under process. A fault should always be located and then it should either be removed or rectified. Until proper steps have been followed, do not do anything with the circuit. Unless the motor load has been disconnected, do not try to open the supply of the alternator set. If the primary winding is capable of allowing current flow through it, then never try to open-circuit the secondary winding. Also never, use the secondary winding open-circuit as an energizer for primary winding. Before working on a circuit make sure, it is entirely dead or has been discarded by an authorized worker. Until then, it is better to maintain your distance from it. While using test equipment, never try to interact with any safety devices as it is quite unsafe. While running a zdc machine, it is crucial to make sure you arrange an armature and open the field circuit at the same time. Without proper provisions, do not ever attempt to run a DC machine. However, you can try it with caution only if you secure the circuit breaker in the field circuit. While using test equipment never alter, any permanent connects and even if you do, make sure you consult correctly with your supervisor. If you modify test equipment, make sure you label it with block letter. After using the equipment, replace the connection to its original position unless your supervisor has asked you not to do it. Never use damage equipment or leave faulty equipment at a place that is accessible by others. Even if your injuries seem light, always get yourself adequately checked by a trained expert. Questions 1. What should not be done before operating a piece of equipment? a) Alter the permanent connection b) DE energize it adequately Ans – A 2. While running a DC machine, you must a) Open the field circuit b) Close the field circuit Ans – A 3. What should be written on a control sheet? a) Proper measure you should take while carrying out a task b) Technical specifications of equipment Ans – A Learning working make money

Electrical Safety – Useful Resources The following resources contain additional information on Electrical Safety. Please use them to get more in-depth knowledge on this topic. Useful Links on Electrical Safety − Wikipedia Reference for Electrical Safety. Useful Books on Electrical Safety To enlist your site on this page, please drop an email to [email protected] Learning working make money

Discuss Electrical Safety In the field of electrical engineering, engineers and other professionals are exposed to electricity indirectly during generation, transportation, installation and usage. Such conditions might cause hazards if accurate safety measures are not taken. This tutorial will help you understand measures that can be taken for electrical safety. Learning working make money

Implications of Human Behaviour The role of a human in the workplace is of great importance. No matter how technologically equipped, an organization gets, it will always require a human for operating and monitoring. The safety of a worker lies in his/her approach towards a machine. Careless attitude while running a machine results in accidents and even death in some cases. It is quite significant to analyze a worker’s behavior towards the machine so that you can stop any electrical hazards in future. Identification of Accident In this section, we will see how to identify an accident. The following points need to be considered to identify an accident − Cause of Accident Identifying the reason that leads to the accident. Events A detailed analysis of the chain of events, that leads to the accident. Difference between accidents Comparing the current accident with previous accidents. The intensity of risk Identifying the risk involved in the task that is being carried out by the workers. Organization’s fault Find out if it is the worker’s fault or the organization’s. Improving the System In this section, we will learn how to improve the system. Task Analysis Each work requires a different set of actions and each action of a worker has a ripple effect on the other. Each task carried out by a worker needs some degree of choice by the worker and that choice sometimes can cause hazards in the workplace. Follow the example given below to have a fair idea about task analysis. Example Suppose a worker at a workplace is asked to raise the temperature of the Air Conditioner by 2 degrees. Now, this task seems easy to execute, but errors can occur due to human behavior. Consider the following actions that can cause errors − Pressing the wrong button A slip type Error will happen if the worker does not know which button to press and presses the wrong button assuming it the right. Execute without knowledge The worker pushes the right button, but during that time he/she thought (guessed of his/her own) that the switch is for other use. Violation In this situation, the employee is perfectly aware of which button to press but still presses a wrong button to complete the task sooner. Choice Analysis All humans tend to make mistakes at workplace especially during the end of their shift, as they are tired and focus on reaching their home as soon as possible. Therefore, while evaluating the human behaviour and performance, one must consider the fact that no human is 100% perfect. When a worker faces stress inside or outside the work, he/she is most likely to commit a mistake. Addressing the issues can help to prevent the errors and avoid any accidents in future. The Choice analysis of a worker is categorized into two perspectives − Personal perspective of the worker Age Gender Personal characteristics The way of learning The tendency to take a risk Workplace perspective of the worker Organizational culture Office politics Reward System of the organization Management system Quality of training provided by the organization Classifying Human Errors In this section, we will classify the different human errors. There are two types of classification approach − PHECA − Potential Human Error Cause Analysis SHERPA − Systematic Human Error Reduction and Prediction Approach PHECA Potential Human Error Cause Analysis focuses on the tasks given in workplace and the error he/she commits. Tasks could be about an operation, maintenance, monitor, check, and communication. Following are the errors caused by workers − Task not done Partially completed the task Done the task but not precisely what was asked for Done the task more than what asked for Done the task before the specified time SHERPA Systematic Human Error Reduction and Prediction Approach combines the task and the error methods. The approach stores the error type separately. SHERPA tie the errors of a worker to his/her performance goal. The causes of the error are linked to the worker’s skill or the knowledge he/she possess. Questions 1. Identification of accident in an organization is crucial. Which one is not a method of identifying a workplace accident? a) Cause of an accident b) Events leading to an accident c) Number of people involves in the accident Ans – c 2. Which one of this does not fall under “personal perspective of a worker” while conducting choice analysis? a) Personal Characteristics b) Reward System c) The tendency to take a risk Ans – b 3. What does PHECA Stand for? a) Potential Human Error Cause Analysis b) Potential Human Error Cause Awareness c) Personal Human Error Cause Awareness Ans – a Learning working make money

Electrical Safety – Types of Safety Equipment The chances of occurrences of hazards at the work place cannot be ignored. So, each employee should be provided with adequate personal protective equipment (PPE) as per Section 19 of the Constitutional Safety and Health Act 1984. Categories of Personal Protective Equipment Personal Protective Equipment can be considered in the following different categories. Respiratory safety Chemicals, dust can enter inside the body through breathing thereby causing chest pain, headache and other symptoms related to breathing problems. Therefore, respiratory safety equipment like disposable filtering half mask, half mask, full face mask, etc. are necessary. Eye Safety Following equipment are used to protect the eyes − Safety glasses Eye shields Goggles Face shields, etc. Ear safety Hearing protection equipment are necessary to protect the eardrums if the noise or sound level exceeds 85 decibels. For the protection, equipment like earplugs, semi-insert ear plugs and ear muffs can be used. Hand safety Harmful substances and chemicals can get absorbed into the skin thereby causing bruises, cuts, abrasion, etc. To avoid these, hand safety equipment can be used such as gloves, finger guards and arm coverings. Foot Safety In plant areas, falling from height, rolling down, crushing or penetrating pointed material are more common. To protect the foot from all these, employees need the following − Safety toe shoe Metatarsal guards Toe guards Leggings Studded treads, etc. Head Safety Protecting employees from potential head injuries forms the major part of any safety program. Therefore, employees are provided hardhats. The hardhats are divided into three categories Class A (Vol res up to 2.2k volt) Class B (Vol res up to 20k volt) Class C (provide protection against light weights) Learning working make money

Electrical Safety – Primary Ex-protection The hazards are generally created in chemical factories, refineries, and paint workshops, cleaning equipment, mills and stores for milled products and in tank facilities and loading areas for flammable gases, liquids and solids. The explosion protection defines the health and safety at the workplace. The principle of Explosive protection When a mixture occurs in air under an atmospheric condition with flammable substances in the form of gas, vapor, dust, fibers or flyings, explosion hits the workspace. Safety parameter is a function of the pressure, temperature and oxygen. So the limitations are necessary. There are three factors of the explosion. flammable material Oxygen (Air) Source of Ignition Figure 1: Basis of Explosion By limiting any one of the above factors can reduce the probability of primary explosion and protection can be determined accordingly. Basic/Primary Ex- protection Primary explosive protection is a process to reduce the number of flammable substances or atmospheric oxygen to a point which ensures no danger of explosion. The open layout and proper ventilation increases air circulation and flushes the air. It is not possible to completely replace the atmospheric oxygen of an area where people work. According to the analyzing facts there are three possibilities of an explosion in presence of flammable gas. Due to heat − open flame/hot surface/hot gases Electrical Sparks − opening and closing of contacts, short circuit, static discharge Mechanical Spark − friction, hammering, grinding The first question arises that is there any form of dangerous materials which potentially causes an explosion. Then what is the quantity of those combustible substances? The potential of an atmosphere for explosion needs to be measured. The primary ex-protection implementation and compliance should meet ex-protection rules and standards. Primary Ex-protection Measures The main aim of primary ex-protection is to prevent the formation of dangerous substances. The protection measures are only to reduce the probability of occurrence of such materials and its spreading capacity. The measures must be cost-effective. Some of the protection measures are below − Try to use incombustible or less volatile substances or replace critical components if possible. System parts should be used with inert gases such as nitrogen. Dilute the combustible liquids with a non-reacting material such as water. Reduce the number of combustible substances. Moistening of dust is necessary. Regular cleaning also reduces the number of dust. Use enclosures filled with inert substances Provide natural or artificial ventilation systems which limit the concentration of flammable materials. Install dangerous gas detection system which can provide a notification through an alarm or breaking of the system. The flash point of flammable liquid should be changed by adding other materials such as water. Otherwise the processing temperature must be lowered. If the flash point of a flammable liquid is above the processing temperature then the faults, stand-stills, leakage come under control. Questions 1. Which one is not a factor of explosion? A. Oxygen B. Electrical spark C. Acetylene D. None of these Ans: D Explanation − No fire exists without oxygen in the air. An electrical spark is a source of ignition and acetylene is a flammable substance. So A, B and C are the factors of the explosion. 2. Why is ventilation necessary for every workplace? A. To flush the air B. To circulate the air C. To limit the concentration of flammable substances D. All of the above Ans: D Explanation − All (A, B, C) are related to each other which are the works of a ventilator. Ventilation is necessary for a workplace for circulating and flushing the air that reduces the concentration of combustible substances. 3. Which substances are used in the enclosures? A. Water B. Inert gases C. Alkali materials D. All of the above Ans: B Explanation − The inert gases don’t react with any material. So enclosures are protected by inert gases. Learning working make money

Electrical Safety – Bonding A fault current always seeks for the low resistance path and through that travels to the nearby systems thereby damaging them to the core. In this regard, all major members of metallic structure should be bonded and well connected as per the lightning protection system. This includes the continuous metal reinforcement and services of the concerned metallic structure. Such bonding should be made at least at two places around the structure. They should be equally spaced and the gap between them should not exceed 15m. The structures contain metalwork frames. The metalwork frames should also be bonded to the lightning protection system. All the conductors entering inside should be metal-cased. The metal casing should be electrically continuous within the structure. It is the critical responsibility of the safety officer to inspect the structure. The point at which the conductor is marking its entry inside the structure should be earthed with respect to the supply side and should be bonded directly to the lightning protection system. There is a different bonding strategy concerned to the conductors of the structure connected directly to the overhead lines. Here, a buried cable of metallic sheath of armour should be connected between the overhead line and the point of entry to the structure. Surge protective devices like voltage-dependent resistors can also be connected. The earth terminal of this protective device should bond with the cable sheath or armouring. Bonding of such type will keep the overall structure safe from lightning. Learning working make money