ಕಾಪ್ಯಾಸಿಟರ್ ಬ್ಯಾಂಕ್ದ ಪ್ರತಿರಕ್ಷೆ
Ithara electrical apparatusagalevu, shunt capacitoruvinu nānā internal mattu external electrical faultsallidde avasara illā. Ani, yannu aparādha mattu bahirāparādhadanu nimmādu prōtekt mele hoga. kondensāra banka prōteksiyon madakke anegalu visheshatāvina yōgana iddare. Ani, yannu yōgane pramāne māduttene, kapasitōravina prārambhik invistmentidda ekonomika paḍadalli tindakudarige enu enu ombattu māḍu. Prārambhik invistmentuvinu prōteksiyonavina costuvinu taḷasi māḍu. Kondensāra bankavina prōteksiyonavina nimma 3 prakāragala agalū.
Element Fuse.
Unit. Fuse.
Bank Protection.
Element Fuses
Kapasitōr unitanna prōdhākararu yōgiyuva elementidda pratyēka inbuilt fuse pradhānapu. Yannu kāṣṭhe, yannu elementinda aparādha hogutillā, adu automatage rest of the unitinna nirbandhita maduvudilla. Yannu kāṣṭhe, unituvinu prāyaṇa karu, antha ellide outputilla. Nimma rated kapasitōra bankavina matra yannu inbuilt prōteksiyon yōgana pramāne prabandhittu allārakāre special prōtektive apparatusanna expensēvuvarjaka maduvudilla.
Unit Fuse
Yannu unit fuse prōteksiyonu sarvajnīya faulty kapasitōr unitinda arc duration limit māḍu. Arc duration limit illā, major mechanical deformation mattu faulty unitinda gas production hogu illā, antha bankanna neighborhood unitsuvinu rakṣiṣe. Kapasitōra bankanna pratyēka unit anna individual prōtektettu fuse illā, yannu ekāda unit failure hogutillā, kapasitōra bankuvinu interruption illā running maduvudilla faulty unit remove mattu replace māḍu.
Ani, yannu pratyēka unitanna prōtektettu fuse illā, faulty unitinda exact location indica māḍu. Antha fuse pramāne size choose māḍu, fuse element harmonic systemanna excessive loading withstand māḍu. Tannu pramāne fuse element current rating full load current 65% above māḍu. Individual unit kapasitōra bankanna prōtektettu fuse illā, discharge resistance pratyēka unitanna pradhānapu.
Bank Protection
Sarvajnīya fuse prōteksiyon kapasitōra unitsanna pratyēka pradhānapu, yannu kapasitōra unit fault hogutillā associated fuse element blown out hogutillā, voltage stress series connected other capacitor units illā hogu. Sarvajnīya, pratyēka kapasitōra unit 110% normal rated voltage withstanding pramāne designed illā. Any other capacitor unit further out of service hogutillā, previously damaged unit same row illā, healthy units voltage stress increase illā maximum allowable voltage cross illā.
Hence it is always desirable to replace damaged capacitor unit from the bank as soon as possible to avoid excess voltage stress on the other healthy units. Hence, there must be some indicating arrangement to identify the exact faulty unit. As soon as the faulty unit is identified in a bank, the bank should be removed from the service for replacing the faulty unit. There are several methods of sensing unbalance voltage caused by failure of capacitor unit.
The figure below is showing the most common arrangement of capacitor bank protection. Here, the capacitor bank is connected in star formation. Primary of a potential transformer is connected across each phase. The 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. In exact balanced condition there must not be any voltage appears 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.
The voltage sensitive relay can be so adjusted that up to a certain voltage unbalancing only alarm contacts would be closed and for certain higher voltage level the trip contacts along with alarm contacts would be closed. The potential transformer connected across the capacitors of each phase also serves for discharging of the bank after being 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.
Here, the capacitor bank of each phase is divided into two equal parts connected in parallel and the star points of both parts are interconnected through a current transformer. The secondary of the current transformer are connected across a current sensitive relay. In case any misbalancing occurs between the two parts of the bank, there would be a unbalance current flowing through the current transformer and hence the current sensitive relay will actuate. In this scheme for discharging the bank after switching off, discharge coil may be connected across the capacitors in each phase.
In another scheme of protection of capacitor bank, the star point of a three phase capacitor bank is connected to the ground through a current transformer and a current sensitive relay is connected across the secondary of the current transformer. As soon as there is any unbalancing between the phases of capacitor bank, there must be a current flowing to the ground through the current transformer and hence the current sensitive relay will be actuated to trip the circuit breaker associated with the capacitor bank.
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