Demystifying Anti islanding feature of Solar Inverter

Solar inverter is the heart of any solar system. It converts your DC power generated from solar PV panels into usable AC power. It is inverter’s smart feature that keeps electricity distribution system protected from external disturbances from Solar side. It is the connecting point between AC utility network grid and DC Solar PV plant.

What is Islanding?

In simple words, islanding means, a network cutoff from all power source.

An electrical system is protected from any network disturbances by protection devices. In case of any fault or unwanted condition, protection system acts, and it disconnects the faulty section from the grid.

Concern for Electricity Distribution utility

Main issues concerning power distribution utilities about the Grid connected Inverter solar system is the possibility that solar plant could feed parts of the electricity distribution grid, even when the grid is disconnected from the main power system. Such a condition is called unwanted island. It is potentially critical both for safety of the person working on the line and health of the network. Sometimes it may be fatal.

The grid failure may be attributed to two reasons.

  1. It could be due to fault in the network and protection system has switched off the line.
  2. For maintenance purpose someone from utility engineer has switched off the line.
  3. Auto failure of the power grid due to some disturbances at far end.
  4. Malfunctioning of network protection device which turned off the supply.

How to protect Human life and system during islanding condition?

It is mandatory to equip the solar PV plant with an Interface Protection (IP) which has to detect the islanding condition and, in this case, to disconnect the Solar PV plant from the distribution grid. This feature is inbuilt in Grid tied inverter that is called anti islanding system. All inverter manufacturer must comply the IEC 62116 standard.

In fact, it is one of the major checkpoints for distribution utility engineer before synchronizing solar PV plant with the grid. Utility engineer physically must check the proper functioning of Anti islanding feature. This must be checked by switching off the incoming power source and checking whether Inverter shuts off automatically or not.

      International Standard (IEC)

To mitigate the risk of safety and network disturbances, it is mandated by the government

to follow IEC 62116:2014 standard by all Inverter manufacturer.

IEC 62116:2014 provides a test procedure to evaluate the performance of islanding

prevention measures used with utility-interconnected PV systems. This standard describes a

guideline for testing the performance of automatic islanding prevention measures installed in or with single or multi-phase utility interactive PV inverters connected to the utility grid.

Moral of the story

Inverter shuts down the solar PV system once the AC supply fails for any reason. It means that when there is no power from utility side, your solar system will cease to work. Inveter will start automatically once both utility supply restores and Solar generation is going on. Anti islanding feature of the inverter is very much important to prevent safety hazard and network disturbance.

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