Dabbobi na Bankin Capacitor
Sannan da duk fadada tashar karkashin kula, mafarin shunt capacitor ya zama da yake sa hankali da gano na farkon da na kananan kulan. Saboda haka, wannan fadan ya bukata da hankali da gano na farkon da na kananan kulan. Ana da wasu tsohon fasahar za su iya amfani da su don hankalin mafarin shunt capacitor, amma a lokacin da ake amfani da wani babban fasahar, ya kamata a tuna cewa abin da aka yi a farko zuwa wannan mafarin shunt capacitor ne daga sabbin lura. Ya kamata a duba abin da aka yi a farko da ma'aikata da ke amfani don hankalin. Ana da uku na nufin hankalin da suke amfani da su a mafarin shunt capacitor.
Fuse Element.
Fuse Unit.
Hankalin Mafarin Shunt Capacitor.
Fuse Element
Makamai masu sana'ar mafarin shunt capacitor suna bayar fuse element a binciken har daidai. Idan yakin da ya faru a bincike, ya zama da ake karfe ta daga binciken da suka bi. A nan, mafarin shunt capacitor ya ci gaba da ciyawa, amma da ciyawa mai yau. A mafarin shunt capacitor da duka mutum da suka fiye, ana amfani da wannan fasahar bayan hankalin don in ba da kasuwanci da take samun irin hankalin mafi yawa.
Fuse Unit
Fuse unit na hankali da ya zama don in iya tsara waɗanda ake faru a mafarin shunt capacitor. Daga cewa an tsara waɗanda ake faru, akwai tsari mai yawa wajen kawo gane da al'amuran jiki da lafiyar gas a mafarin shunt capacitor da ke faru, saboda haka, mafarin shunt capacitor da suka bi daɗi ake faru suke buƙaci. Idan kowace mafarin shunt capacitor ana hankali da fuse, idan wani mafarin shunt capacitor ya faru, mafarin shunt capacitor zan iya ci gaba da ciyawa har da koyar da kuma ake faru mafarin shunt capacitor da ke faru.
Wannan faɗinsu na musamman na hankalin fuse unit shine cewa ya bayyana wurin da mafarin shunt capacitor da ke faru. Amma a lokacin da ake zaba girman fuse da ya zama, ya kamata a tuna cewa element of the fuse ya zama da kyau don in iya taka da muhimmin koyar da suka faru a cikin harmonics a system. Don haka, rating of the fuse element for this purpose is taken as 65% above the full load current. Idan kowace mafarin shunt capacitor ana hankali da fuse, ya kamata a bayar discharge resistance a binciken da suka bi.
Hankalin Mafarin Shunt Capacitor
Idan mafarin shunt capacitor ta faru da fuse element ta shiga, voltage stress ya zama da yake so a mafarin shunt capacitor da suka bi daɗi a kan layin da mafarin shunt capacitor ta faru. Gaskiya, har daidai mafarin shunt capacitor ana kunshi 110% of its normal rated voltage. Idan wani mafarin shunt capacitor da suka bi daɗi ta faru, a kan layin da mafarin shunt capacitor ta faru, voltage stress upon other healthy units of that row will increase further and easily crosses the limit of maximum allowable, voltage of these units.
Saboda haka, ya kamata a koyar mafarin shunt capacitor da ke faru daga bank a matsayin yanayi don in ba da excess voltage stress on the other healthy units. Saboda haka, ya kamata a bayar fasahar don in bayyana wurin da mafarin shunt capacitor da ke faru. Idan ake bayyana mafarin shunt capacitor da ke faru a bank, bank ya kamata a koyar da ita don in ake koyar mafarin shunt capacitor da ke faru. Akwai wasu hukumar don in tabbatar da 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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