Rêbaza Pêşkêşkirînê ya Dahaşên Erdîngan
Sistem pîvaneyê, an jî sistem grounding, binyanên taybetî yên sisteman rêzgeran derbarên derga hewl bike. Li ser virê, li ser yekîtiya Tirinê, ji bo amniyet û xebitandina kar. Herêmekê pîvaneyê dikare amniyet û kompatibilitiyê elektromagnetik ê destkir bike. Qanûnakên herêmekê pîvaneyê di navçeyên de girihandin, lê çendîyan wekheviyên Komisyonê Yekbûyê Elektroteknîk (IEC) bibin. Li vê nivîsê de, divê çêna cûrên herêmekê pîvaneyê, zaf û kêmêtirên wan, û yekem jî ye ku bi çawa dizayn bikin û bindest bikin.
Pîvaneyê Sistem Dîsa?
Sistem pîvaneyê diha ve dike heye seti rêzgeran û elektrodan ku hewl dide paqijka rêzgerî ya bi cîhan digire. Li viriya serdema re û malperê, ev pirrast e:
Parastina pergalan: Sistem pîvaneyê yardim dike parastina pergalan rêzgeran ji daneya vegere û serdema re. Ji ber vê, vegerekan static û qetel û serdema re yên ku ji deketin lightning an operasyonên switching hatine girtin parast kirin.
Parastina mirovan: Sistem pîvaneyê yardim dike parastina azdeyaş û şok rêzgeran bi hesabkirina ku pirgalên metali tevahî yên installyasyonan rêzgeran li ser potensiyala Tirinê be. Ev da ku operasyonên pergalan parastana wekheviya circuit breakers an residual current devices (RCDs) ku dikarin destkirin ji viriya serdema re.
Nokta referansa: Sistem pîvaneyê nokta referansa dike bi viriya Tirinê ji bo sirkelan û pergalan rêzgeran bi viriya safe voltage. Ev da ku her rêzgerî ji bo viriya Tirinê bi viriya safe voltage.
Cûrên Sisteman Pîvaneyê
BS 7671 pêdivî dike cûrên pîvaneyê: TN-S, TN-C-S, TT, TN-C, û IT. T û N ji bo:
T = Tirin (ji fermana Fransî Terre)
N = Neutral
Herfên S, C, û I ji bo:
S = Separate
C = Combined
I = Isolated
Cûra herêmekê pîvaneyê bi viriya ku (transformer an generator) bi Tirinê li ser Tirinê bibin û ji bo consumer's earthing terminal bi source an local earth electrode.
TN-S Sistem
Sistem TN-S, di Figure 1 de, neutral source of energy li ser Tirinê li viriya yek ji viriya source. Consumer's earthing terminal li ser metallic sheath an armor of the distributor's service cable into the premises.
Figure 1: TN-S Sistem
Zaf û kêmêtirên sistem TN-S:
Hewl dike paqijka impedance li ser fault currents, ku bi viriya fast operation of protective devices.
Li viriya consumer’s premises, potential difference between neutral and earth.
Rizika electromagnetic interference li ser common mode currents.
Kêmêtirên sistem TN-S:
Bi viriya separate protective conductor (PE) li ser supply conductors, cost û complexity of wiring.
Corrosion an damage to the metallic sheath or armor of the service cable, effectiveness.
TN-C-S Sistem
Sistem TN-C-S, di Figure 2 de, 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 Sistem
Zaf û kêmêtirên sistem TN-C-S:
Number of conductors required for supply, cost û complexity of wiring.
Hewl dike paqijka impedance li ser fault currents, fast operation of protective devices.
Potential difference between neutral and earth within the consumer’s premises.
Kêmêtirên sistem TN-C-S:
Electric shock if there is a break in the neutral conductor between two earth points, touch voltage on exposed metal parts.
Unwanted currents to flow in metal pipes or structures that are connected to the earth at different points, corrosion or interference.
TT Sistem
Sistem TT, di Figure 3 de, 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 Sistem
Zaf û kêmêtirên sistem TT:
Risk of electric shock due to a break in the neutral conductor or contact between live conductors and earthed metal parts.
Unwanted currents in metal pipes or structures that are connected to the earth at different points.
Flexibility in choosing the location and type of earth electrodes.
Kêmêtirên sistem TT:
Effective local earth electrode for each installation, difficult or costly depending on soil conditions and space availability.
Additional protection devices such as RCDs or voltage-operated ELCBs to ensure reliable disconnection in case of a fault.
Higher touch voltages on exposed metal parts due to higher earth loop impedance.
TN-C Sistem
Sistem TN-C, di Figure 4 de, 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 Sistem
Zaf û kêmêtirên sistem TN-C:
Number of conductors required for supply, cost û complexity of wiring.
Hewl dike paqijka impedance li ser fault currents, fast operation of protective devices.
Kêmêtirên sistem TN-C:
Electric shock if there is a break in the PEN conductor or if it comes into contact with live parts due to insulation failure.
Unwanted currents to flow in metal pipes or structures that are connected to PEN at different points, corrosion or interference.
Special precautions for connecting appliances with exposed metal parts that may be accessible simultaneously with other earthed metal parts.
IT Sistem
Sistem IT, di Figure 5 de, has its source either isolated from Earth or connected to Earth through an impedance (such as a resistor or an inductor). The consumer’s installation is connected to the earth through one or more local electrodes. These electrodes do not have any direct connection with the source.
