Gidagidi Mai Tsawo na Ayyuka da Turanci
Sistem earthing, ko da ake kira sistem grounding, yana haɗa wani abubuwa daga cikin sashe na noma power system da karamin harkar mulki, tare da karamin harkar mulki na Earth, don dalilai masu inganci da maƙasidun. Zan iya zama da takamataccen nasara ga cin bayanai da kuma electromagnetic compatibility ta gida. Koyarren da ke sa a yi wa suka shafi da kuma cin bayanai na earthing suna bambanta a kan kasashen, amma akwai mafi yawan da suka tabbatar da International Electrotechnical Commission (IEC). A nan, za a bayyana farkon abubuwan da ke earthing, muhimmancinta da kuma yadda ake kiranta da kuma tsara.
Mai Suna Da Sistem Earthing?
Sistem earthing yana nufin set da ke conductors da electrodes wadanda ke ba aiki da low-resistance path don electric current zuwa harkar mulki a lokacin fault ko malam. Wannan yana da muhimmanci saboda:
Protection of equipment: Sistem earthing yana taimakawa da protection da electrical equipment daga damage da ke faruwa da overvoltage ko short-circuit conditions. Yana taimaka kuma da static buildup da power surges da suka faruwa da lightning strikes ko switching operations.
Protection of people: Sistem earthing yana taimakawa da prevention da electric shock hazards tare da ensuring da exposed metal parts da electrical installations suka fi sune da potential da Earth. Yana taimaka kuma da operation da protective devices kamar circuit breakers ko residual current devices (RCDs) wadanda suke disconnect supply a lokacin fault.
Reference point: Sistem earthing yana ba reference point don electrical circuits da equipment don haka za su iya operate da safe voltage level da respect to Earth. Wannan yana taimaka cewa energy da ba a yi da load ba za a kasa da Earth.
Farkon Abubuwan Da Ke Earthing Systems
BS 7671 ta bayyana biyar abubuwan da ke earthing systems: TN-S, TN-C-S, TT, TN-C, da IT. Dukata T da N suna nufin:
T = Harkar Mulki (daga French word Terre)
N = Neutral
Dukata S, C, da I suna nufin:
S = Separate
C = Combined
I = Isolated
Abubuwan da ke earthing system ana tabbatar da ita tare da how source of energy (kamar transformer ko generator) yana haɗa da harkar mulki da kuma consumer’s earthing terminal yana haɗa da source ko local earth electrode.
TN-S System
A TN-S system, shown in Figure 1, has the neutral source of energy connected with earth at one point only, at or as near as is reasonably practicable to the source. The consumer’s earthing terminal is typically connected to the metallic sheath or armor of the distributor’s service cable into the premises.
Figure 1: TN-S System
The advantages of a TN-S system are:
It provides a low impedance path for fault currents, which ensures a fast operation of protective devices.
It avoids any potential difference between neutral and earth within the consumer’s premises.
It reduces the risk of electromagnetic interference due to common mode currents.
The disadvantages of a TN-S system are:
It requires a separate protective conductor (PE) along with the supply conductors, which increases the cost and complexity of wiring.
It may be affected by corrosion or damage to the metallic sheath or armor of the service cable, which can compromise its effectiveness.
TN-C-S System
A TN-C-S system, shown in Figure 2, has the supply neutral conductor of a distribution main connected with the earth at the source and at intervals along its run. This is usually referred to as protective multiple earthing (PME). With this arrangement, the distributor’s neutral conductor is also used to return earth fault currents arising in the consumer’s installation safely to the source. To achieve this, the distributor will provide a consumer’s earthing terminal, which is linked to the incoming neutral conductor.
Figure 2: TN-C-S System
The advantages of a TN-C-S system are:
It reduces the number of conductors required for supply, which lowers the cost and complexity of wiring.
It provides a low impedance path for fault currents, which ensures a fast operation of protective devices.
It avoids any potential difference between neutral and earth within the consumer’s premises.
The disadvantages of a TN-C-S system are:
It may create a risk of electric shock if there is a break in the neutral conductor between two earth points, which can cause an increase in touch voltage on exposed metal parts.
It may cause unwanted currents to flow in metal pipes or structures that are connected to the earth at different points, which can result in corrosion or interference.
TT System
A TT system, shown in Figure 3, has both the source and the consumer’s installation connected to the earth through separate electrodes. These electrodes do not have any direct connection between them. This type of earthing system is applicable for both three-phase and single-phase installations.
Figure 3: TT System
The advantages of a TT system are:
It eliminates any risk of electric shock due to a break in the neutral conductor or contact between live conductors and earthed metal parts.
It avoids any unwanted currents in metal pipes or structures that are connected to the earth at different points.
It allows for more flexibility in choosing the location and type of earth electrodes.
The disadvantages of a TT system are:
It requires an effective local earth electrode for each installation, which may be difficult or costly to achieve depending on soil conditions and the availability of space.
It requires additional protection devices such as RCDs or voltage-operated ELCBs to ensure a reliable disconnection in case of a fault.
It may result in higher touch voltages on exposed metal parts due to higher earth loop impedance.
TN-C System
A TN-C system, shown in Figure 4, has both the neutral and protective functions combined in a single conductor throughout the system. This conductor is called PEN (protective earth neutral). The consumer’s earthing terminal is directly connected to this conductor.
Figure 4: TN-C System
The advantages of a TN-C system are:
It reduces the number of conductors required for supply, which lowers the cost and complexity of wiring.
It provides a low impedance path for fault currents, which ensures a fast operation of protective devices.
The disadvantages of a TN-C system are:
It creates a risk of electric shock if there is a break in the PEN conductor or if it comes into contact with live parts due to insulation failure.
It causes unwanted currents to flow in metal pipes or structures that are connected to PEN at different points, which can result in corrosion or interference.
It requires special precautions for connecting appliances with exposed metal parts that may be accessible simultaneously with other earthed metal parts.
IT System
