- System or Service Ground: In this type of ground, a wire called "the neutral conductor" is grounded at the transformer, and again at the service entrance to the building. This is primarily designed to protect machines, tools, and insulation against damage.
- Equipment Ground: This is intended to offer enhanced protection to the people themselves. If a malfunction causes the metal frame of a tool to become energised, the equipment ground provides another path for the current to flow through the tool to the ground.
A major precaution aspect to grounding to be aware of: a break in the grounding system may occur without the user's knowledge. Using a ground-fault circuit interrupter (GFCI) is one way of overcoming grounding deficiencies.
The lower the resistance, the better it a grounding system will work.
Grounding System Components
- Plugs and sockets have a grounding pin.
- Plugs with grounding pin are actually connected to a 3-wire network.
- Ground wires are well connected to each other on the distribution board, normally through a grounding pad or a connecting strip in metal.
- The grounding pad or the connecting strip is connected to the ground and this link must be done with a high-thickness wire (for example, 16mm²).
- This wire is connected to the ground.
|Ground Connecting Cables in Use|
A grounding system typically consists of a grounding conductor, a bonding connector, its grounding electrode (typically a rod or grid system), and the soil in contact with the electrode. An electrode can be thought of as being surrounded by concentric rings of of earth or soil, all the same thickness - each successive ring having a larger cross-sectional value and offers less and less resistance until a point is reach that it adds negligible resistance.
Electricity is potentially dangerous and has inherent risks, especially from ; a circuit failure, misuse, inexperienced handling, or negligence. The effects on the humans. , appliances, and other objects can be very devastating. When installing an electrical circuit - the whole system or just an extension - , extending an existing circuit, or looking for a new office or guest house , it is recommended perform a full assessment to on the facility. Full assessments should ensure that the circuit can safely handle the current flow needed, proper protections devices exist, the circuit is grounded, and there are no potential hazards.
For equipment, the dangers of an improperly installed or secure circuit are short circuits and overloads. For people, the dangers are come from insulation faults that lead to direct or indirect contact with electrical currents.
A short circuit is a strong overcurrent of short duration. In single-phase systems, a short circuit occurs whenever the phase and neutral wires accidentally come into contact; in three-phase systems, this can occur when there is contact between two of the phases. For DC, a short circuit can occur when the two polarities come into contact.
An overload is caused from by a weak overcurrent occurring over a long duration. Overloads can be caused by a current that is too high with respect to be conducted through the relative diameter of the conductorsconducting cable.
There are two kinds of overload:
Insulation faults are caused by damage to the insulation of one or more phase conductors. These faults problem problems can lead to electrical shocks from current-carrying lines, and if the damaged conductor touches a metal surface or casing, can cause appliance and equipment to be electrified to the touch as well.
These faults can be very dangerous, especially when a person comes into direct contact with the conductor (directly), a metal casing, or a defective electrical appliance (indirectly). In all cases the human body become becomes part of the electrical circuit causing an electric shock.
This image depicts an electrical current as it flows through the human body.
The arrows demonstrate indicates the flow of electricity from the point it enters the body to the nearest exit point. The blue arrow demonstrates the flow of current through the head to the heart then to ground, which is the most lethal scenario.
|Level of Exposure||Reaction|
More than 3 mA
Painful shock- cause indirect accident
More than 10 mA
Muscle contraction – “No “Cannot Let Go” danger
More than 30 mA
Lung paralysis, usually temporary
More than 50 mA
Ventricular fibrillation, usually fatal
100 mA to 4 A
Certain ventricular fibrillation, fatal
Over 4 A
Heart paralysis, severe burns
To avoid or reduce the damaging effects current can have in a human body, is highly recommended to use protection protective equipment and take precautions when handling electrified circuits and equipment.
- Rubber Gloves – to To prevent touching hands from directly making contact with the current. They must be close fitting and have an excellent grip.
- Tight Sleeves and trouser Trouser Legs – To prevent unintentional contact or being pulled into dangerous equipment.
- Remove rings from fingers.
- Rubber Boots – To prevent the body from forming a complete conducting electrical circuit.
Electric shock occurs when the human body becomes part of the path through which current flows.
The direct result is electrocution. The indirect result can is injury resulting from a fall or uncontrolled movement into machinery because of a shock.
Burns can result when a person touches electrical wiring or equipment that is energised.
Arc-blasts occur from high-amperage currents arcing through the air. This can be caused by accidental contact with energised components or equipment failure.
The three primary hazards associated with an arc-blast are:
Explosions occur when electricity provides a source of ignition for an explosive mixture in the atmosphere.
Electricity is one of the most common causes of fires both in the home and in the workplace. Defective or misused electrical equipment is a major cause of electrical fires.
Safety signs keep persons aware of hazards. It is important to located them accordingly so persons working around the hazard can take proper precaution. They should be in visible places and include the maximum possible information about the source of danger and properties of itthe danger. In case of an incident, this information can be a valuable information.
Example of these sings can besigns include:
|Voltage Warning Labels||Electrical Voltage Symbol||Danger of Death from Electricity Warning||Switch Off when not in Use|
|Electric Shock Warning||High Voltage Warning||Overhead Cables Warning||Live Wires Warning|
|Buried Cables Warning||Mains Voltage Warning||Danger - Do not Enter Sign||Warning - Isolate Before Removing Cover|
Electricity is one of the most common causes of fire. Electrical current and the chemical reaction of fire are both methods of transferring energy; while electricity involves the movement of negatively charged electrons, a flame consists of the dispersal of both positive and negative ions. Therefore, faulty wiring for example can cause arcing and sparking that can easily become a flame if the conditions to produce a fire are present (, such as oxygen, heat and or any kind of fuel).
Power sources that are directly related to electrical fires can be any of the following:
Electrical fires need to be put out by a substance that is non-conductive substance, unlike the water or foam found in class A fire extinguishers. If someone attempts to put out an electrical fire with something like water, there is a high risk of electrocution since water is conductive. This is why class Class C fire extinguishers exist; the substances that can be found in these types of extinguishers are use monoammonium phosphate, potassium chloride, or potassium bicarbonate, which do not conduct electricity. Another option would be is a class C extinguisher that contains carbon dioxide (CO2). CO2 is great for suppressing fires because it takes the fire’s oxygen source away as well as diminishes the fire’s heat since the CO2 is cold when expelled from the extinguisher.
Prevention is the most effective measure to mitigate risk. Some of these preventive measures /actions planners can take when working around electricity include:
- Never plug appliances rated at 230 V into an 115V electrical socket.
- Place all lamps on level surfaces and away from things that can burn.
- Use bulbs that match a lamps’ rated wattage.
- Do not overload an electrical outlet by connecting several devices into a single receptacle using any device.
- Do not tug or pull any electrical cords.
- If an outlet or switch is feeling warm, shut off the circuit and call an electrician to check the system.
- Follow manufacturer’s instructions for plugging a device into an electrical outlet.
- Avoid running extension cords under carpets or across doorways.
- Do not connect the cord of an old electrical device to a newer cord.
- Replace and repair frayed or loose cords on all electrical devices.
- Keep all electrical appliances away from water.
- Contact electricity authority if any damage done to overhead cables, outdoor panel boxes, or trees touching high voltage lines is seen.
- Review architectural drawings and/or contact electrical authorities before doing any work involving digging.
- Take heed to all warning signs indicating electrical hazards.
- Ensure a fire extinguisher is placed where the likelihood of a hazard occurring is great.
- Always wear safety equipment when around electrical equipment.
Most humanitarian interventions - and especially the ones performed during emergencies - take place in remote or jeopardised communities with a poor availability and/or limited reliability of the electrical public grid. To operate, humanitarian organisations premises are frequently equipped with at least one independent power supply (batteries, generator or solar equipment), either as back up in case of grid failure or as the primary method of producing electricity. Independent power supplies include batteries, generators and solar-electric equipment.
Purchasing, installing and running such equipment requires important investments that can be reduced with a proper sizing and energy demand management. Electricity is not cheap, and running a generator can become quite expensive. Energy production also has an environmental impact and has the potential to damage the perception that the community could have about the organisationof organisations.
It is often possible to reduce electricity consumption without degrading the quality of service by improving the energy management, focusing on reducing the demand, and choosing the correct supply.
- Energy demand managementDemand Management: minimise Minimise energy consumption without reducing the quality of service and avoid unnecessary energy consumption.
- Energy supply managementSupply Management: selecting Select the best main and back-up power supplies in accordance to with the particular situation, properly sized to optimise investment and running costs.
To manage both demand and supply management, a proper diagnostic to understand the installation power and energy needs is required. Continued diagnostics it will be necessary at each step of the energy management process, mainly:
- To calculate the total energy and power needs of a planned operating environment and help sizing size the power supplies (generator, solar, or other).
- To identify the appliances and services that account for a significant part of the total energy and power needs.
- To understand the variation of the power and energy needs within a day and identify the peak periods.
It is normal to take electricity for granted, however it always will come with some costsenergy always comes at a cost. To improve the way the energy is used, avoid unnecessary consumption and minimise the inevitable without degrading the quality of the service. It is important to think in terms of service instead of devices, and try to find the most effective solutions to accomplish the required service.
- Identify high-impact services to understand what services have significant impact on power and energy consumption and when the peak periods occur.
- Examine potential alternatives – working tools, refrigerators, and lighting are obvious consumers of electricity and hard to avoid. Other consumers of energy offer other possibilities, such as water heaters and stoves. Consider possible solutions according to feasibility and initial cost, energy consumption and running cost and service quality.
- Reduce losses, increase efficiency by choosing efficient and well-sized appliances according to the purpose and number of users, and by using them in a way that maximises their efficiency, such as cleaning and maintaining equipment and appliances to increase their efficiency.
- Reduce unnecessary use by switching off and unplugging appliances when not in use. It may be required to display posters or leaflets to reminder users.
- Optimise consumption over time, identifying peak periods and if possible, avoid or postpone the use of the most powerful appliances during peaks or when running on battery/solar back-up systems. Mark powerful appliances for which who's use can be postponed, such as ones those for comfort or non-urgent tasks with red stickers and with one label the unpostponable ones used for , and differentiate those used or work, security, communications with another so users can tell one from the other.
Energy Supply Management