Capacitive voltage indicators are installed in the panels of medium voltage switchgear for simple voltage checking.
Why it is needed?
For some applications, there is no need to measure the voltage for connecting further measurement or protective equipment like Voltmeters and Relays. Example likes to detect system to verify safe isolation from supply. The voltage-free conditions on the equipment, provide guarantee the personal safety during operation and work on the switchgear panel.
If system is isolated from supply there should be no voltage present. For such applications, equipping the switchgear panel with Potential Transformers is very expensive.
Capacitive Voltage Indicator
For such situations, voltage detection using Capacitive voltage indicators offers an efficient and cost-reducing alternative, and is ideally suited for medium-voltage switchgear systems.
Capacitive voltage indicator tells either “voltage present” or “no voltage present” only. If there is potential on the bus bar the LEDs are flashing else no LED flash.
Principle of operation of capacitive voltage indicators:
Capacitive voltage indicators worked based on capacitive voltage dividers. These consist of capacitors connected in series. The voltage across individual capacitors is divided in inverse proportion to the ratios of their capacitances.
The smallest value capacitor coupled to the bus bar. The largest value capacitor is connected to the LED circuit. If any voltage is present LED flashing occurs otherwise no LED flashing. Like this with the help of Capacitor voltage divider circuits, Capacitive voltage indicators shows the presence of voltage on the bus bars.