Banka Paşînê Pêşkeftin

Pêşnûmîna Banka Capacitor

Pêşnûmîna bankên capacitor dike ku hûn bigihînin kexmiranên dervey û dervey dixebitandina çalakî û ewlehiyayê.

Element Fuses

Herî zeman degerandîyan fuses bingehîn yên her elementê. Eger kexmiranek di element de bigihîne, otomatîk ji yekîtiya yekîtiya werin virast kirin. Yekîtiya hala yekîtiya dikare bikar bibe, lê bi pêşketinê ve qalîb. Ji bo bankên capacitorên meheng, tenha vê cihêza pêşnûmîna bingehîn anîn ne hatîn bikar estin da ku bi mafeyê re têkiliya pêşnûmîna bêtir bike.

Unit Fuse

Pêşnûmîna fuse unit dike ku dema xulka di unitên capacitorên kexmiran de girîng bikin. Ew riseka zaravên mekanîkîya mezin û çêkirina gazan were girîng bikin, unitên dinçên parast dike. Eger her unit di banka capacitor de fuse wekî heye, banka dikare bi bistîweyê li serdane bikin, heta ji bo virastkirina unita kexmiran u barkirina wê.

Yekîtra zêdeba mezin ya pêşnûmîna fuse ji bo har unita banka ye ku nîşan dike ku unita kexmiran de ku şoqet e. Lakin, dema dewana mezatê ya fuse ji bo vê amadeyê, hewce ye ku elementa fuse biguherebine ku berazîn bike bekar û barkirina harmonikên di sisteman de. Di navbera wan de, mezata currenti ya elementa fuse ji bo vê amadeyê 65% ji bo full load current li serdar in. Herdemêji unita individuala banka capacitor pêşnûmîna fuse hene, hewce ye ku resistance discharge di her unit de bikin.

Bank Protection

Herî unita capacitor fuse protection hene, eger unita kexmiran bigihîne û fuse yekîtiya were virast kirin, voltage stress di unitên din de di rowa series de girîng dike. Her unita capacitor dizayn kirin ku 110% ji rated voltage-ya wê tuhaf bike. Eger unita din di rowa yekem de kexmiran bigihîne, stress di unitên dinçên din de girîng dike û divê maximum voltage limit-ê bifeqe.

Nimûne, hewce ye ku unita capacitor kexmiran ji banka jî werin virast kirin ji bo nirxandinê voltage stress ê li unitên dinç. Nima, hewce ye ku vê amada arrangement bînin da ku unita kexmiran nîşan bide. Bi salîhera unita kexmiran di banka de nîşan bide, banka divê ji serdane were virast kirin ji bo virastkirina unita kexmiran. Ji bo sensen unbalance voltage ji bo kexmiran unita capacitor zêdetir metoda hene.

Wêneya jêrîn nîşan dike ku amada pêşnûmîna banka capacitor yên piştguhîn. Li vir, banka capacitor bi formasyona star hate pêserast kirin. Primary of a potential transformer across each phase connected is. Secondary of all three potential transformers are connected in series to form an open delta and a voltage sensitive relay is connected across this open delta. 

Di şertê balansînan de nabe ku voltage across the voltage sensitive relay because summation of balanced 3 phase voltages is zero. But when there would be any voltage unbalancing due to failure of capacitor unit, the resultant voltage will appear across the relay and the relay will be actuated for providing an alarm and trip signals.

Voltage-sensitive relay can be adjusted so that at a certain voltage imbalance, only the alarm contacts close. At a higher voltage level, both the trip and alarm contacts close. The potential transformer connected across each phase’s capacitors also helps discharge the bank after it’s switched off.

In another scheme, the capacitors in each phase are divided into two equal parts connected in series. Discharge coil is connected across each of the parts as shown in the figure. In between the secondary of discharge coil and the sensitive voltage that unbalances the relay an auxiliary transformer is connected which serves to regulate the voltage difference between secondary voltages of discharge coil under normal conditions.

Here the capacitor bank is connected in star and the neutral point is connected to the ground through a potential transformer. A voltage sensitive relay is connected across the secondary of the potential transformer. As soon as there is any unbalance between the phases, the resultant voltage will appear across the potential transformer and hence the voltage sensitive relay will be actuated beyond a preset value.