Capacitor bank ni kundi la capacitors zinazokuwa na uwezo sawa unazozuiwa kutoka kwa mstari au upande wa pembeni ili kukusanya nishati ya umeme katika mfumo wa nishati ya umeme. Capacitors ni zawadi zinazoweza kuhifadhi chaguo cha umeme kwa kutengeneza electric field kati ya vibao viwili vya chuma vilivyotengenezwa kati ya materiali ya kuzuia. Capacitor banks zinatumika kwa maana tofauti, kama vile power factor correction, voltage regulation, harmonic filtering, na transient suppression.
Power factor ni utaratibu wa kuangalia jinsi AC (alternating current) power system inatumii nishati iliyotolewa. Inaelezwa kama uwiano wa real power (P) na apparent power (S), ambapo real power ni nishati inayofanya kazi muhimu katika load, na apparent power ni mfululizo wa voltage (V) na current (I) katika circuit. Power factor inaweza pia kutathmini kama cosine ya pembe (θ) kati ya voltage na current.
Power factor = P/S = VI cos θ
Power factor mzuri sana ni 1, ambayo inamaanisha kwamba yote ya nishati iliyotolewa imebadilika kwa kazi muhimu, na hakuna reactive power (Q) katika circuit. Reactive power ni nishati inayoflowa kuelekea na kutoka kutoka kwa chanzo hadi load kutokana na presence ya inductive au capacitive elements, kama vile motors, transformers, capacitors, etc. Reactive power haijafanya kazi yoyote, lakini huchangia losses zingine na kurudia efficiency ya system.
Reactive power = Q = VI sin θ
Power factor wa system inaweza kuwa kutoka 0 hadi 1, kulingana na aina na wingi wa load uliyoungwa kati yake. Power factor chache inamaanisha reactive power demand mkubwa na utilization chache ya nishati iliyotolewa. Power factor kubwa inamaanisha reactive power demand ndogo na utilization bora ya nishati iliyotolewa.
Power factor correction ni mchakato wa kuboresha power factor wa system kwa kuongeza au kupunguza reactive power sources, kama vile capacitor banks au synchronous condensers. Power factor correction ina faida kadhaa kwa wateja na watumiaji, kama vile:
Kupunguza line losses na kuimarisha efficiency ya system: Power factor chache inamaanisha current flow mkubwa katika system, ambayo huchangia resistive losses (I2R) na kupunguza voltage level katika mwisho wa load. Kwa kuongeza power factor, current flow huachwa, na losses humpunguziwa, kufanyika voltage level kubwa na performance bora ya system.
Kuongeza capacity na reliability ya system: Power factor chache inamaanisha apparent power demand mkubwa kutoka kwa chanzo, ambayo huchukua wingi wa real power unaweza kutumika kwa load. Kwa kuongeza power factor, apparent power demand huachwa, na zaidi ya real power inaweza kutumika kwa load, kufanyika capacity na reliability kubwa za system.
Kupunguza utility charges na penalties: Wengi wa utilities wanatamba ada au kuleta penalties kwa wateja ambao wana power factor chache, kama wana sababisha more burden kwenye transmission na distribution network na kuongeza costs zao za operations. Kwa kuongeza power factor, charges hizi au penalties zinaweza kupunguziwa, kufanyika bills za umeme chache kwa wateja.
Capacitor bank hufanya kazi kwa kutumia au kupata reactive power kutoka kwa au kutoka kwa system, kulingana na connection mode na location yake. Kuna aina mbili za capacitor banks: shunt capacitor banks na series capacitor banks.
Shunt capacitor banks zinawunganishwa in parallel na load au katika points maalum katika system, kama vile substations au feeders. Wanatumia leading reactive power (positive Q) kutatua au kupunguza lagging reactive power (negative Q) ulioelewa kutokana na inductive loads, kama vile motors, transformers, etc. Hii huboresha power factor ya system na kupunguza line losses.
Shunt capacitor banks ina faida kadhaa kwa reactive power compensation devices mingine, kama vile:
Wanahitajika rasimu, wachezezi na rahisi kusimamia na kuhifadhi.
Wanaweza kusimamiwa au kurejesha kulingana na variation ya load au requirement ya system.
Wanaweza kugawanya kwenye units ndogo au steps ili kupatikana flexibility na accuracy zaidi katika control ya reactive power.
Wanaweza kuboresha voltage stability na quality katika mwisho wa load kwa kutumia local reactive support.
Hata hivyo, shunt capacitor banks pia ina faida chache au limitations, kama vile:
Wanaweza kusababisha overvoltage au resonance problems ikiwa si kwa njia sahihi kusimamia au kusambaza na devices mingine katika system.
Wanaweza kuongeza harmonics au distortions katika system ikiwa si kwa njia sahihi filtered au protected.
Wanaweza si kwa urahisi kwa long transmission lines au distributed loads.
Series capacitor banks zinawunganishwa in series na load au transmission line, kupunguza effective impedance ya circuit. Wanatumia lagging reactive power (negative Q) kutatua au kupunguza leading reactive power (positive Q) ulioelewa kutokana na capacitive loads, kama vile long cables, transmission lines, etc. Hii huboresha voltage regulation na stability ya system.
Series capacitor banks ina faida kadhaa kwa shunt capacitor banks, kama vile:
Wanaweza kuongeza power transfer capability na efficiency ya long transmission lines kwa kupunguza line losses na voltage drop.
Wanaweza kupunguza short-circuit current na fault level ya system kwa kuongeza impedance ya fault path.
Wanaweza kuboresha transient response na damping ya system kwa kupunguza natural frequency na oscillations.
Hata hivyo, series capacitor banks pia ina faida chache au limitations, kama vile:
Wanaweza kusababisha overvoltage au resonance problems ikiwa si kwa njia sahihi kusimamia au kusambaza. Kwa mfano, wakati wa fault condition, voltage across the capacitor inaweza kusonga hadi 15 mara ya rated value yake, ambayo inaweza kuang'ara capacitor au equipment mingine katika system.
Wanaweza kuongeza harmonics au distortions katika system ikiwa si kwa njia sahihi filtered au compensated.
Wanaweza si kwa urahisi kwa low voltage au distributed loads.
Ukubwa wa capacitor bank unategemea kwa factors kadhaa, kama vile:
Improvement desired ya power factor au reactive power compensation
Voltage level na frequency ya system
Aina na location ya capacitor bank (shunt au series)
Load characteristics na variation
Cost na availability ya capacitor units
