Earthing System International
Earthing System International
About
An earthing (or grounding) is system connects specific parts in electrical installations with the Earth's conductor use for safety and functional purposes. The purpose of this protection to allow fault happening such as leakage current from equipment to go to ground and absorbed by earth. This can minimized damage done on to human or equipment. This is a mandatory requirement in Malaysia and it most important in electrical system as protection.
There are four types of earthing system according to IEE Wiring Regulations standard.
TT system (is also known as local earthing)
TN-S system
TN-C-S system
IT system
Basic Component for earthing
Main earth conductor - or commonly known as electrode copper rod.
Standard size of electrode copper rod shall be 16 mm diameter.
Depth of the electrode copper rod shall be buried into the ground at least 3 meter or more.
1. TT systems
At one point is connected directly to earth (functional earthing). The exposed-conductive parts of the electrical installation are connected to earth electrodes which are electrically isolated from the earth electrode for earthing the system.
T - Secondary side of supply transformer shall be earthed. Direct connection of a point with earth.
T - All exposed metal frame or body of equipment shall be earth. Earth connection is by a local direct connection to earth.
Applications of TT system in Malaysia.
residential supply
commercial supply system
industry supply system
Figure TT system
One point at the supply source (secondary transformer by electricity provider) is connected directly to earth. All exposed- and extraneous-conductive-parts are connected to a separate earth electrode at the installation. All earth conductor shall connects back to an earth chamber where electrode copper rod is been installed into the ground minimal 3 meter depth.
Ground/Earth contact for TT system
Earth conductor is required commonly known as electrode copper rod.
2. TN-S system
This earth terminal is connected by the supply protective conductor (PE) back to the star point (neutral) of the secondary winding of the supply transformer, which is also connected at that point to an earth electrode. Consumer premise do not have to construct earth chamber and do not required to install an electrode copper rod onto the premise' ground. This safe cost of purchasing complete earthing accessories.
Applications of TN-S system in Malaysia.
overhead line (LT) supply system
NOT ALLOWED for residential, commercial and industry
Protective Earth (PE)
An earth ground connection of the exposed conductive parts of electrical equipment helps protect from electric shock by keeping the exposed conductive surface of connected devices close to earth potential.
Figure TN-S system
Earth conductor is NOT REQUIRED at consumer supply.
Ground/Earth contact for TN-S system
Earth conductor is not required , it is provide by local electricity provider at secondary transformer.
3. TN-C-S system
This method is a basically jointing the neutral and earth together at same point on the secondary transformer of electricity provider. The protective conductor is being shared same with neutral point, known as protective earth neutral (PEN).
Terms : C - combine but S - separate
Applications of TN-C-S system in Malaysia.
NOT ALLOWED for residential, commercial and industry
Protective Earth Neutral (PEN)
An earth ground connection of the exposed conductive parts of electrical equipment helps protect from electric shock by keeping the exposed conductive surface of connected devices close to earth potential and share together with neutral conductor.
Figure TN-C-S system
The diagram above showing the earth terminal is shared with neutral terminal in the connection. This method is not advisable to use in Sarawak and Malaysia, because it may cause frequent trips to happen.
Ground/Earth contact for TN-C-S system
Earth conductor is NOT REQUIRED at consumer supply.
Danger: If the metallic surface of electrical equipment detect leakage current may cause electrocution to happen.
4. IT system
This method is where the neutral conductor is not connected to earth. The IT system can have an unearthed supply, or one which is not solidly earthed but is connected to earth through a current limiting impedance. IT system is used for circuits supplying medical equipment and not allowed for public use.
I - indicates either that the supply system is not earthed at all, or that the earthing includes a deliberately-inserted impedance, the purpose of which is to limit fault current.
Applications of IT system in Malaysia.
NOT ALLOWED for residential, commercial and industry
only for HV transmission line
Figure IT system
The diagram above showing the earth terminal is not available at supply provider. So all earthing system shall apply the following bonding method which are equip-potential bonding, supplementary bonding and circuit protective conductor (CPC).
Ground/Earth contact for TN-C-S system
Earth conductor is REQUIRED at consumer supply and extra grounding or earth bonding is recommend such as CPC.