Versions Compared


  • This line was added.
  • This line was removed.
  • Formatting was changed.



Short for Alternating Current.


Short for Direct Current.


Small charged particles that exist as part of the molecular structure of materials.

Free electron

An electron that is easily separated from the nucleus of the atom to which it belongs.


Bodies that possess free electrons (metals, for example, but also the human body and the earth).


Bodies that do not possess free electrons (e.g., glass, plastic and wood).

Voltage (U)

The difference in charge between two points.

Current (I)

The rate at which charge is flowing.

Resistance (R)

A material's tendency to resist the flow of charge (current).


A closed loop that allows charge to move from one place to another.


Any material that allows electrical energy to be converted to thermal energy.


Additional power available for a short amount of time.

VRLA Battery

Short for Valve Regulated Lead Acid Battery.

Absorption voltage range

The level of charge that can be applied without overheating the battery.

Float voltage range

The voltage at which a battery is maintained after being fully charged.

Distribution Panel:

This is a circuit breaker and contains many electrical circuits. Using this, a circuit can be turned on or off.

Circuit breakers and Fuses:

These protect wires from overheating and are found in the distribution panel box. When there is an overload, that is, too much current flowing, the fuses will blow or the circuit breakers will trip. Fuses and circuit breakers are rated so therefore at a particular current, they will be damaged by the circuit will be off.


Switches can energize energise circuits, that is, they allow a current to flow through. If carelessly used, these can cause damage to a person and to equipment. Receptacles connect the appliances to a circuit.


connecting metal parts of electric appliances to earth.

(W)Short for Watt, the Power unit measure.
(Wh) Short for Watt-hour, the Energy unit measure
(V) Short for Volts, the Voltage unit measure
(A)A Short for Ampere, the Electrical Current unit measure


The aim of this is guide is provide an idea about how to transform and use the electric energy in to electric power where electric current is used to energize energise the equipment and devices needed in the humanitarian interventions. Understanding the basic electric concepts, knowing how to properly size the installation, how to efficiently manage it with all the safety and precautions measures in place.


To be able to use electrical equipment properly and safely it is important to understand electricity works.  It is vital to start by understanding the basics of voltage, current, and resistance - the three basic building blocks required to manipulate and utilize utilise electricity - and how the three relate to each other.


Electricity is the movement of electrons. Electrons create charge, which are harnessed to produce power. Any electrical appliance - a lightbulblight-bulb, a phone, a refrigerator - are all harnessing the movement of the electrons to work. The three basic principles for this guide can be explained using electrons, or more specifically, the charge they create:


These values describe the movement of charge, and thus, the behavior behaviour of electrons.

A circuit is a closed loop that allows charge to move from one place to another. Components in the circuit allows to control this charge and use it to do work.


Resistance determined by load. For example: wire conductors with a larger cross section offer less resistance to current flow and results in a smaller voltage loss. Inversely, resistance is directly proportional to the length of the wire. To minimize minimise voltage loss, current needs the shortest possible wire with a large cross-section. (see cabling section) Note also that the kind of wire (copper, iron, etc.) also affects a cable’s resistance.


The more powerful the load, the more current it draws. This calculation is useful when analyzing analysing power needs.

Power Vs. Energy
  • Watts
  • Kilowatts

"like the flow rate of water"
  • Watt-hours
  • Kilowatt-hours

"like the water that ends up in the bucket"


  • A transformer that converts a higher voltage current to a lower voltage current is called a “step down” transformer, and can work by either converting high voltage low current loads to low voltage high current loads, or by adding resistance between two circuits to limit the voltage output, resulting in lower power being received on the output side.
  • A transformer that converts to a higher voltage is called a “step up” transformer, and works by converting low voltage but high currents into high voltage but low currents. A step up transformer does not add additional electrical power to the circuit, it only increases overall voltage.
  • A transformer that convers converts a current from DC to AC is called an inverter, and physically induces an alternating current on the output side. Inverters typically consume electrical power for the conversion process, and thus are less energy efficient than other forms of transformers.
  • A transformer that convers converts a current from an AC to DC can be called a "battery charger" (for charging batteries) or a "power supply" (for direct powering of a radio, etc.), depending on how the conversion process works.


Cable sizing table is used by running across the top row until the column with the relevant amperage is found, and then moving down the left-hand column until the row with the relevant distance is reached. The color colour coding in the body of the table at the intersection of this row and column is the wire size. Compare this with the Cable Conversion Table to see what size cable to use.


















Diameter (mm)














Cross Section (mm2)














Color Colour Code

Color Colour Coding

While is possible to use the same cables, (as far the diameter will be the appropriate one) for AC and DC circuits, it is advisable to use different colored coloured cables between the two types of currents, both to increase handling safety but also to make installation and repair work much faster. In existing appliances or installations have colorscolours, logistics managers may consider replacing or standardizing standardising them by re-color colour coding the wires with an external paint or marking in a method that makes sense.

A general color colour cod for AC looks like:

  • Neutral: blue
  • Phase: brown or black
  • Ground: green/yellow.

The neutral and the phase are the two connections for the electricity, the ground is for safety.

Color Colour code for DC (direct current, battery):


However, many international standards apply. Please reference the below table for color colour coding of different countries and regions around the world 

Standard Wire Colors Colours for Flexible Cable

(e.g. Extension Cords, power cords and lamp cords)

Region or Country



Protective Earth/Ground

European Union (EU), Argentina, Australia, South Africa

Australia, New Zealand




United States, Canada




(green) or


Standard Wire Colors Colours for Fixed Cables

(e.g. In/On/Behind the wall wiring cables)

Region or Country



Protective Earth/Ground



European Union and UK


UK Prior to March 2004


Australia, New Zealand

Any colors colours other than:


Recommended for single-phase:


Recommended for multiphasemulti-phase:


 (since 1980)

 (since 1980)

bare conductor, sleeved at terminations (formerly)


South Africa


bare conductor, sleeved at terminations

India, Pakistan

United States


(120/208/240V) (brass),






bare conductor

(ground or isolated ground)




(single-phase isolated systems)


(three phase isolated systems)




bare conductor

(isolated ground)



A fuse is a very basic protection device used to protect the circuit from overcurrent. It consists of a metal strip that liquefies when the flow of current through it surpasses a pre-defined limit. Fuses are essential electrical devices, and there are different types of fuses available in the market today based on specific voltage and current ratings, application, response time, and breaking capacity.

The characteristics of fuses like time and current are selected to give sufficient protection without unnecessary disruption.

Miniature Circuit Breaker (MCB)

An MCB is a modern alternative to fuses, and are maybe centrally located in buildings – usually called a “fuse box” or “braker “breaker box”, or attached to specific equipment. They are just like switches, turning off when an overload is detected in the circuit. The basic function of a circuit breaker is to stop the flow of current once a fault has occurred. The advantage of MCBs over fuses is that if they trip, they can be reset without having to replace the whole MCB. MCBs can also be calibrated more precisely than fuses, tripping at exact loads. Circuit breakers are available in different sizes from small devices to large switch gears which are used to protect low current circuits as well as high voltage circuits.

Residual Current Device (RCD)

Residual Current Devices (or RCDs) are designed to detect and disconnect supply in the event of a small current imbalance between the Live and Neutral wires at a pre-defined value - typically 30mA. RCDs can detect when a live conductor touches an earthed equipment case, or when a live conductor is cut through; this type of fault is potentially dangerous and can result in electric shocks and fires.

An RCD does not give safety against short circuit or overload in the circuit. It cannot detect – for example - a human being accidentally touching both conductors at the same time. An RCD cannot replace a fuse in function.

RCDs can be wired to protect a single or a number of circuits - the advantage of protecting individual circuits is that if one circuit trips, it will not shut down the whole building or distribution system, just the protected circuit.

Residual Current Breaker with Overcurrent (RCBO)

An RCBO combines the functions of a MCB and an RCD in one unit. CRBOs are a safety device which detects a problem in the power supply and is capable of shutting off in 10-15 milliseconds.

They are used to protect a particular circuit, instead of having a single RCD for the whole building

These devices are testable as well as resettable apparatus. A test button securely forms a tiny leakage condition; along with a reset button again connects the conductors after an error state has been cleared.


  1. 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.
  2. 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 energizedenergised, the equipment ground provides another path for the current to flow through the tool to the ground.


The connection between metal parts and grounding is made using a third wire in the electrical circuit. Ground wires usually have a green-yellow color colour and must have the same gauge as the biggest wire used on the installation to protect.




Possible Sources


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 injury resulting from a fall or movement into machinery because of a shock.

  • Electrical Cords can Cause Trip Hazards.
  • Frayed power cords are dangerous
  • Overloading Electrical Sockets.
  • Damaging Cords by Running over them or placing heavy objects on them
  • Modifying Electrical Plugs.
  • Overheating Machinery by not having adequate ventilation.
  • Damaged Electrical Outlets.
  • Exposed Wires.
  • Working Close to Power Sources.
  • Overhead Lines.
  • Water Dripping on Live Equipment.


Burns can result when a person touches electrical wiring or equipment that is energizedenergised.


Arc-blasts occur from high-amperage currents arcing through the air. This can be caused by accidental contact with energized energised components or equipment failure.

The three primary hazards associated with an arc-blast are:

  • Thermal radiation.
  • Pressure Wave.
  • Projectiles.


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.


Most humanitarian interventions - and especially the ones performed during emergencies - take place in remote or jeopardized jeopardised communities with a poor availability and/or reliability of the electrical public grid. To operate, humanitarian organizations 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.

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 organizationorganisation.

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 management: minimize minimise energy consumption without reducing quality of service and avoid unnecessary energy consumption.
  • Energy supply management: selecting the best main and back-up power supplies in accordance to the particular situation, properly sized to optimize optimise investment and running costs.


It is normal to take electricity for granted, however it always will come with some costs.  To improve the way the energy is used, avoid unnecessary consumption and minimize 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 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 maximizes 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.
  • Optimize consumption 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 use can be postponed, such as ones for comfort or non-urgent tasks with red stickers and with one label the unpostponable ones used for work, security, communications with another so users can tell one from the other.


Properly choice of main and back-up power supply will have a large impact not only in cost savings, but in the way the energy consumption is optimizedoptimised. The chosen combination must be able to:

  • Deliver enough power for the installation.
  • If possible, guarantee a 24/7 availability of electricity in the building.
  • Ensure a minimum quality (limited voltage drop or frequency fluctuations).
  • Minimize Minimise costs.
  • Run and operate safely.
  • Keep the impact on the local environment as low as possible, including reducing smoke, vibrations, noise during the night, ensure good living and working conditions and prevent neighborhood neighbourhood conflict.
  • Minimize Minimise the global environmental impact.


Example: Standard Label on the Side of Generator

Power rating is standardized standardised as ISO-8528-1, the most common standards are:


Most of the time, only PRP is relevant when purchasing a generator. When acquiring a generator, check if the power of the generator is indicated without reference to a standardized standardised rating method. If no rating model is indicated, either consult it with the manufacturer or obtain documentation from the seller.

Power can be rated either in watt (W), kilowatt (kW), volt-amps (VA) or kilovoltkilo-volt-amps (kVA).  For the sake of clarity, 1kW = 1000W and 1kVA = 1000VA

A rating in watts indicates a real power (P); a rating in volt-amperes indicates an apparent power (S). Only the real power has to be considered when planning consumption. Real power is the power actually consumed or utilized utilised in an AC Circuit, and therefore it is the way power needs and energy consumption is calculated in a diagnostic exercise.


Tank Capacity

A generator cannot be refueled refuelled while it is running, thus the tank capacity is one of the main factors determining autonomy. A conservative estimation of a 1500 RPM generator hourly consumption is 0.15 L x rated power. Fuel tank must be chosen accordingly.


The choice of fuel must be determined according to local price and availability of both type of fuel. One point to consider is what type of fuel the vehicles in the organizations organisations use, using the same fuel for both generators and vehicles can reduce complexities of keeping multiple types of fuel in stock. Safety may also be a concern for very large stock quantities of fuel - diesel fuel also has a significantly higher flash point than gasoline, meaning it will ignite in the open air only above 52°C while gasoline can ignite in below freezing temperatures.


Generators must be equipped with a residual current circuit breaker, so that power surges and short circuits can trip the breaker locally, making it easier to reset and preventing damage from further down the circuit. Additionally, generators usually have a manual breaker/transfer switch to control the connection of centricity electricity to the installed circuit of the office or compound.


The room or storage area must cover several purposes; isolate the generator to decrease the noise and environmental impact on its surroundings, and preventing non-authorized authorised access from staff, visitors, animal, or others. Even if a generator is relatively exposed, such as a covered awning with no walls, it is still advisable to have some sort of access control to the physical generator. Generator’s storage areas may require additional physical built up walls on one or more side of the generator to block noise and prevailing winds.

Although construction materials can vary, the orientation must be planned carefully, taking advantage of the wind currents and minimizing minimising the noise and heat disturbances. A generator space should always be well ventilated, including use of soffit vents or entirely exposed walls. If a generator is in a tightly enclosed space, a specially made air outlet ducts is required. Ensure all outlets don’t discharge into areas where humans and animals work or access frequently. If no other option is available than to ventilate into areas where humans and animals access, then all discharge points should be at least two meters from said spaces and be well marked.


In general, proper management of a generator starts by having an accurate and up to date monitoring system. Monitoring is crucial to be able to perform analysis, identify potential failures and misuses, and inform future repairs and decision making. It is important to maintain records at least on:

  • Running hours.
  • RefuelingRefuelling.
  • Maintenances Maintenance performed.

A simple but complete logbook should be used. A logbook should be kept near the generator, and all persons managing the generator should be trained and sensitized sensitised in its correct use.

Even though PRP generator types are rated for “unlimited” usage, this does not mean generators can run for an unlimited continuous time. Generators are still machines, which suffer from degradation and can overheat or break down. The continuous operability operation of generators may vary from machine to machine, but generally speaking the generators that humanitarian agencies obtain in field contexts are not designed to operate for more than 8 to 12 hours of continuous use at one single time. Running a generator for longer than an 8 to 12 hour period can dramatically shorten the life of a generator as well as lead to a higher frequency of break downs.


Use of two generators can be planned according to needs – either both generators should have identical power supplying capability, or the secondary generator is used for hours when load requirements are less. Solar power and other backup power supplies can also be connected to the external transfer switch. Usually, the act of switching between generators includes starting the incoming generator while the outgoing is still running. This will allow the incoming generator to warm up. It will also allow the main transfer switch to move between generators while power is being supplied, to minimize minimise disruption to offices or living quarters.


Preventative maintenance thus ensures that the organization organisation get uninterrupted power supply for all the needs.


In some programs or sites of operation, it makes sense to have a trained repair technician permanently as part of the team. In most of the cases, is recommended to identify and establish a long-term agreement or other form of service contract with a trusted provider, in charge of the main maintenance and be ready in case of breakdowns. Important criteria when selecting a third party provider is their ability to supply spare parts for the required equipment. If a third-party provider cannot supply spare parts, then organizations organisations will need to maintain a stock of their own spare parts.

A generator set is the combination of an engine and an alternator plus wiringswiring, controls, protections and connections. Therefore, that is what needs to be checked when looking for a failure.


  • To receive an AC current the battery will need a transformer or specialized specialised battery charger.
  • To deliver an AC current, the battery will need an external inverter.


As each battery has a limited capacity, battery power supplies require special equipment to monitor and control the flow of electricity entering a battery, called a charge controller. A charge controller will continuously monitor the charge state of a battery – recognizing recognising how “full” it is – and should automatically terminate charging once a battery is full. Batteries are highly energetic and can be extremely dangerous of over charged! An overcharged battery can spark, start fires, and even explode, possibly throwing hazardous chemicals while it does. No battery power backup should be attempted without a proper charge controller in place.


A battery is a storage device capable of storing chemical energy and converting it into electrical energy though electrochemical reaction. There are many different types of chemistries chemistry that are used, such as nickel-cadmium batteries used to power small portable devices or Lithium-ion (Li-on) batteries used for larger portable devices. The most proven type of chemistry and the longest used however is the lead acid battery.


Batteries are made with several materials and shapes suitable for different purposes. This guide will focus on the most common batteries used as a back-up of a power generation sources. The two main types can be summarized summarised as:

  1. Flooded Batteries.
  2. Valve Regulated Lead Acid Batteries.


AGM (Absorbed Glass Mat) Batteries 

The AGM construction allows the electrolyte to be suspended in close proximity with the plate’s active material. This enhances both the discharge and recharge efficiency.

Since there are no liquid inside, these batterie batteries scan perform better than flooded batteries in applications where maintenance is difficult to perform, however they are sensitive to over or under charging affecting their life and performance. AGM batteries perform most reliably when their use is limited to the discharge of no more than 50% of battery capacity.

AGM batteries are usually the type of batteries selected in off-grid power systems.

Gel Cell Batteries

Gel cell batteries have a water-acid in gel form. The electrolyte in a gel cell battery has a silica additive that causes it to set up or stiffen.  The recharge voltages on this type of cell are lower than the other styles of lead acid battery and gel cells are probably the most sensitive cell in terms of adverse reactions to over-voltage charging.

Gel batteries are best used in very-deep cycle applications and may last a bit longer in hot weather. Unfortunately a total deep discharge will irreversibly destroy the battery. If the incorrect battery charger is used on a gel cell battery, poor performance and premature failure is certain. 

Note: It is very common for individuals to use the term gel cell when referring to sealed, maintenance-free batteries, much like one would use Kleenex when referring to facial tissue. Be very careful when specifying a charger. More often than not, what someone is referring to a gel cell they really mean sealed, maintenance-free VRLA or AGM-style battery. Gel cell batteries are not as common as AGM batteries, and would be hard to source in humanitarian contexts.


  • Isolate the battery system to decrease the risk of accident - such as acid leakage, harmful gas emissions - and prevent non-authorized authorised access.
  • Ensure good operating conditions: battery room must protect electronics against water and dust and be well ventilated.


The power of the charger will determine how long recharging will take. A high-power charger that can charge batteries rapidly are useful if the main power supply is very expensive – a big generator with high consumption - or if the electricity from the main power supply is only available during short durations duration - public grid available only few hours per day.


Solar panels are devices able to transform light radiation into electricity through a process of trapping the photons and using them to excite P-type and N-Type semiconductors to move free electrons. Modern photovoltaic panels can generally convert around 15-20% of energy directly into electricity. There are panels that are more efficient, but they are very costly and easy to damage, and are generally not accessible in places where humanitarian organizations organisations might work.

Light enters the device through an anti-reflective coating that minimizes minimises the loss of light by reflection; it effectively traps the light striking the solar cell by promoting its transmission to the three energy-conversion layers below.  


Most solar cells are a few square centimeters centimetres in area and protected from the environment by a thin coating of glass or transparent plastic. Because a typical 10cm×10cm (4 inch × 4 inch) solar cell generates only about two Watts of electrical power, cells are usually combined in series to boost the voltage or in parallel to increase the current. A solar, or photovoltaic (PV), module generally consists of 36 or more interconnected cells laminated to glass within an aluminum aluminium frame.

One or more of these PV modules may be wired and framed together to form a solar panel, and multiple panels can combined to form a solar array, together supplying power as a single unit.


Sometimes it is difficult to completely avoid shades. The priority should be to avoid shades during the sunny hours (generally 10am to 16pm). Remember that the positions and sizes of shadows change with seasons.

Solar Panel Position

To optimize optimise energy production, solar panels must be carefully oriented to take full advantage of sunlight exposure. Solar panel pointing includes.