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  • Yakub Ansari

4 Ways of reverse power flow protection in grid-connected PV systems

Updated: Aug 10, 2021

On-gird (gird-tie/gird connected) solar power (PV) plant generates excess power when the connected load is lesser than the power generated by the solar power plant (Power generation > Power required).


This excess power is synchronized with grid power hence it can revere the power flow. In simple words, power will flow from the PV plant owner’s home to the connected grid [when Solar power generation > Power required by connected load].


And if the net-meter is not installed at the PV plant owner’s home. This excess power will increase the electricity bill of the PV plant owner.


The reason behind this is that a normal energy meter measures only the power flow through it, irrespective of the direction of power. So normal energy meter will measure both imported and export power (reverse power) and sum them up.


Whereas net-meter measure the input power form the gird and subtract the surplus power injected back to gird from an on-grid solar power plant.


Also if PV plant owner is using DG (diesel generator) as reference power source [in place of gird] for on-grid (grid-tie) inverter. This excess power of the on-gird PV plant will damage the DG set or trip its breaker [if there is any breaker].


Related post: Why generators are rated in kVA

Do you want to learn how to synchronize DG set with an On-gird solar power plant? Here is my whole page on "DG synchronization with grid-tie PV plant".


4 ways of reverse power flow protection for gird connected (gird tie) PV system


#1 Use RPR (relay power relay) to isolate PV plant from the gird by means of tripping breaker or releasing contactor, if there is any reverse power detected.


#2 Use Export limiter to limit the power generation of the grid-tie solar inverter concerning the power required by the load.


#3 Use of PLC as an export limiter.


#4 Use Mini PLC to isolate PV plant from the gird by means of tripping breaker or releasing contactor, if there is any reverse power detected.