Operation and Maintenance of Capacitors

A routine check of the capacitor performance is made by measuring current with the help of Ammeter/Tong tester once in two months and the record is maintained. If any reduction in current /failure of capacitor is noticed, supplier/ manufacturers must be contacted immediately and replacement of capacitor initiated. The status of the capacitor is determined by the voltage at the highest voltage bus available at the substation. It is subject to the maximum permissible voltage at the bus on which the capacitor bank is connected and the loading factor. The loading factor is the ratio of the total MVA load on the bus at which the capacitor is installed to the MVAR rating of the capacitor. Accordingly, the switching on/off of the capacitor bank is done as per Table 1.

Table 1 : Voltage of Highest Level at the Substation

The loading factor and the status of capacitor switch are given in Table 2.

Table 2: Loading Factor and the Status of Capacitor Switch

LV bus voltage is controlled through changing transformer taps. Notwithstanding the above, if the voltage at the bus on that capacitor is connected is 1.1 per unit or higher, the capacitor is switched off.