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Standard

Unit

AWG

0000

000

00

0

1

2

4

6

8

10

12

14

16

Diameter (mm)

11.68

10.40

9.27

8.25

7.35

6.54

5.19

4.11

3.26

2.59

2.05

1.63

1.29

Cross Section (mm2)

107.1

84.9

67.5

53.5

42.4

33.6

21.2

13.3

8.4

5.3

3.3

2.1

1.3

Colour Code

Colour Coding

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

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The lower the resistance, the better a grounding system will work.

Grounding System Components

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

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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.

Short Circuit

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.

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Physical damage can expose cables inside of insulation, while a sudden temperature increase of the conductors can cause the insulation and copper cores to melt.

Overload

An overload is caused by a weak overcurrent occurring over a long duration. Overloads can be caused by a current that is too high to be conducted through the relative diameter of the conducting cable.

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  • Normal overloads, which can occur when a motor starts up. Normal overloads are short-lived and pose no danger.
  • Abnormal overloads occur when too many appliances are connected to the same circuit or the same outlet at the same time, or when a connection terminal isn’t properly tightened. These problems are common in old buildings with too few outlets, but can occur on any installation as the number of electric devices increase. The current is lower in an abnormal overload than that of a short circuit, but the results are identical: overheated wires, damaged insulation, high risk of fire.

Insulation Faults

Insulation faults are caused by damage to the insulation of one or more phase conductors. These 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.

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Level of ExposureReaction

More than 3 mA

Painful shock

More than 10 mA

Muscle contraction – “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

Safety Equipment

To avoid or reduce the damaging effects current can have in a human body, is highly recommended to use protective equipment and take precautions when handling electrified circuits and equipment. 

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In this configuration the main power supply is a generator that provides electricity during peak hours. The back-up is a battery system that accumulates electricity when the generator is running and supplies the installation during low consumption hours. 

Advantages

Disadvantages

  • 24/7 electricity without outage or micro-outage
  • No nuisance during low consumption hours 
  • Good electricity quality
  • Better reliability and service-life of the generator
  • More flexibility on power consumption
  • Easy to add solar supply


  • Fuel supply and stock required
  • Minimum daily running duration for the generator to reload batteries
  • Local purchase and maintenance may not be possible
  • Battery room required
  • Higher initial cost than generator alone
  • Back-up generator may still be necessary
  • Limited lifespan of the batteries (2 to 5 years) and possible environmental impact of battery disposal


Recommended for

  • Isolated office or compound
  • First step towards Solar system installation

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Public Grid OR Generator + Solar

In this configuration, electricity is provided by the main source - grid or generator - during peak hours and by solar system during the day. A battery system accumulates electricity from all sources and supplies the installation when they are off.

Advantages

Disadvantages

  • Same as “grid/generator + battery”
  • Lower nuisances
  • Fuel saving, best cost/efficiency ratio on the long run for isolated building
  • Very reliable back-up power supply


  • Could require some time to be installed.
  • Local purchase and maintenance may not be possible
  • Battery room and a large open surface required
  • High initial cost
  • Limited lifespan of the batteries (2 to 5 years) and possible environmental impact of battery disposal


Recommended for

  • Isolated guest-house
  • Isolated building with limited energy needs
  • Isolated building in area where fuel supply is very difficult and/or very expensive
  • Building where security context impose a very reliable and totally autonomous back-up power supply, such as places with possible hibernation requirements.

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Generators Sets

A generator is a combination of an engine (prime mover) that produces mechanical energy from fuel and an electrical generator (alternator) that converts mechanical energy into electricity. These two parts are mounted together to form a single piece of equipment.

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The 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 minimise disruption to offices or living quarters.

Starting and Stopping a Generator

Generators above a certain size and made for medium to long term usage generally have an internal switch used to connect or disconnect the unit from the main installed circuit of the office or compound. If the generator switch is set so that the generator is not connected, the motor will still run and the alternator will still produce electricity, however the main circuit will not be able to receive an electrical current.

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  1. Warn users that the power will be cut.
  2. Open the generator circuit breaker (if the generator does not have a circuit breaker: open the installation main breaker).
  3. Wait 2 minutes and.
  4. Stop the generator.
  5. Record time of stoppage on the associated log book.
  6. Refuel if necessary.

Care & Maintenance

A generator must be regularly maintained to ensure it provides quality power throughout its life. Routine maintenance is relatively straight forward - there are general guidelines on what and when services are needed to prevent failures or enhance the equipment functioning.

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Intensive Usage

Occasional Usage

Starting generator

As often as required

At least once a week

150 hours maintenance

Every month

Every 4 months

250 hours maintenance

Every 3 month

Every year

500 hours maintenanceEvery 6 monthsEvery 2 years

Corrective Maintenance

In some programs or sites of operation, it makes sense to have a trained repair technician permanently as part of the team. In most cases, is recommended to identify and establish a long-term agreement or other form of service contract with a trusted provider. Service providers should be 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 organisations will need to maintain a stock of their own spare parts.

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It is recommended to refer to the user manual for specific fault-finding instructions as designs vary between manufacturers. Unless a problem is immediately identifiable, a professional generator technician or a qualified electrician may be required.

Safety Considerations

  • A generator must never be operated in a room continually occupied by persons or animals.
  • A generator room must be correctly ventilated.
  • Fuel and oil must not be stored in the generator room.
  • A fire extinguisher rated for electric and fuel fires (preferably a CO2 fire extinguisher) must be available outside the generator room. Fire sand bucket can be an option when extinguishers are not available or as a backup.
  • All generator must be properly grounded. Usually, generators came with a grounding bolt in the frame marked with the ground symbol, to which ground cables should be attached. If there is no evident bolt, the ground line can directly be connected to the metallic frame of the generator.

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