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State the working principle and operation of Automatic power factor controller used in Transmission and Distribution system.

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Diagram of Automatic over factor controller


Automatic Power factor control: The pf controller is used to maintain the pf at unity across the lines it is connected. Maintaining the pf at unity leads to reduction in the current through the lines as real power = apparent power x pf. The apparent power decides the MD for which the consumer is billed. For a certain motor the current in the lines will depend on its pf which is lagging. For higher pf near unity maintained at the motor terminals the line currents are minimized leading to lower MD and hence saving in MD charges. Also as the current is minimized line voltage drops and power losses are reduced leading to improvement in the motor power supply system efficiency. The pf controller does not efficiency


1. Please check if required kVAr of capacitors are installed. 2. Check the type of capacitor installed is suitable for application or the capacitors are de rated. 3. Check if the capacitors are permanently ‘ON’. The Capacitor are not switched off 4. when the load is not working, under such condition the average power factor is found to be lower side. 5. Check whether all the capacitors are operated in APFC depending upon the load operation. 6. Check whether the APFC installed in the installation is working or not. Check the CT connection is taken from the main incomer side of transformer, after the fix compensation of transformer. 7. Check if the load demand in the system is increased. 8. Check if power transformer compensation is provided.

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