Anti-Islanding
Is a type of electrical protection for State-Grid connected Generators that can include one or many sources such as Solar, Wind, Hydro and fuel Generators.
Anti-Islanding ensures the generator system Disconnects all electrical supply into the State-Grid in the event of a State Grid outage/blackout.
Anti-Islanding protection exists to protect mainly persons working on State grid infrastructure, when a State-Grid distribution fault or maintenance occurs.
Why do we need Anti-Islanding Protection?
Islanding can be dangerous to utility workers, who may not realize that a circuit is energised, and it may prevent automatic re-connection of devices. For that reason, inverters must detect islanding and immediately stop SENDING power into the State Distribution Grid, this is referred to as Anti-islanding protection.
The most common example of islanding is where a Micro Power Grid (MPG) inverter has any form of energy from solar, wind, battery etc. generating electricity into the MPG inverter if connected into the State Grid infrastructure.
In the case of a blackout, the MPG will continue to deliver power to the inverter as long as the sun is shining or any other form of Power is being Generated from Batteries, Wind, Aqua or fuel Generator. In this case, the MPG Power supply line is an "island" with power, connected & supported by un-powered state-grid lines.
Can Solar Only Inverter be connect to Batteries ?
Directly NO, however there are two simple ways to do this, and there is one thing that you will need to consider after/when you install Energy Storage into your Micro Grid, being
How Connect Batteries to a Solar Only Inverter;
- We consider the simplest method is leave your existing Solar Only Inverter in place and use it to Exporting any Excess Power you Generate into the State Grid for a Feed-in-Tariff (FIT), and AC connect one or more Hybrid Inverters in Parallel if wanting 2-Phase or 3-phase power, see this article on AC Coupled System, it shows images & explains how to do this.
- Replacing your Solar Only Inverter with a Hybrid Inverter may not be needed id you DC Couple one or more Hybrid inverters to provide single, two or three phase Power, and utilise Batteries or other Power sources like Wind, Aqua or a fuelled Generator, see this article on DC Coupled System that shows images how to do this.
For those reason inverters that are designed to supply power to the state-grid are generally required to have some sort of automatic Anti-islanding protection in them.
In an intentional Off-grid system, the islanding feature disconnects itself from the State grid, and forces the inverter to power the local MPG circuit. This was previously and often used as a backup system.
Islanding
Grid-interactive inverters are required to produce AC power that matches the existing power presented on the State grid. In particular, the voltage, frequency and synchronise phases of the feed the inverter connects to.
Islanding is commonly a self contained Off-Grid System, that's NOT reliant on the State Grid, until all other sources of Alternate Energy are depleted. (This subject can get deep)
Basically Islanding Protection is a way to KEEP the State Grid Safe for Workers & Infrastructure, in the event of a power disruption to the State-grid lines.
A MPG inverters convert the varying DC current generated by the panels, into AC power that matches the grid supply. If the grid is disconnected, the voltage on the grid line would be expected to drop to zero, a clear indication of a service interruption (Black-out).
However, you can install Two inverters if you require energy independence, meaning that Your Main Inverter can be an Off-Grid Inverter, that should have a AGS Function (Auto Gen-set Start), so that your Solar, Aqua & Wind Turbines etc. connected to IT, your MPG work independently to the State Grid.
For the Cost of a Second Inverter that is ONLY connected to any State Grid Lines, would only be used for two functions, Exporting or Importing Energy to Black-Out Proof your Premises, if all your forms of Energy Generation Stop/Fail to Generate!
Exporting is to return an income based on what would normally Waster Energy, and Two figures, the "Remain Grid Connected Charge" & Feed-in Tariff Rate the Retailers offer (P2P Energy is New).
Please Note: We are AGAINST all approved Generators being Charge the standard $80 per quarter to "Remain State-Grid Connected", as this means you as a Generator, have to first gift 800kWh of Energy to the Retailer to break even, that is if the FIT is 10cents kWh, Only then will you start receiving a profit!
We strongly feel Generators should NOT be Charged a Connection Fee, as it is & should be a mutual Two way street, as we are talking just the Wires to the nearest power pole, not the network!
Currently an Off-Grid System with a Second Inverter, would only be used to connect to State Grid for Export excess energy or Black-out proofing an Off-Grid System, and as such would Rarely be used for Importing, it is SMARTER sending what would Normally be Un-used ENERGY (as a Generator) into the grid power lines, ONLY when there is MORE than 9kWh per Day or 800kWh of Excess Energy per Quarter to break even!
Again, when the house's load matches the output of the solar array at the instant of the grid interruption, the panels can continue supplying power, which is used up by the house's load. In this case there is no obvious indication of an interruption.
Even when usage and generation are matched, the failure of the state grid will result in additional transient signals, there will almost always be a short decrease in line voltage, which will indicate a potential fault. Such events can also be caused by normal events, like the starting of Hi-Amp electrical goods.
Ways to detect islanding without a large number of false trips is the subject of considerable research. Each way has some threshold that needs to be met before a state is considered to be a signal of State Grid interruption, which leads to a protection blind spot in the range of conditions where a real grid failure will be filtered out. These are several ways of detecting islanding. |
