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Isolated island effect, that is, when the power grid loses voltage due to some fault, the photovoltaic power station can keep supplying power to part of the system line. Silos can be either planned or unplanned. As the name implies, when the occurrence of unplanned should be caused by a certain reason in the power grid, which may affect the normal operation of the station, equipment damage or personnel safety. Therefore, in order to prevent this failure, it is required to set up island protection.

So what are the requirements for protection against isolated islands? * In general, island protection should be active and passive. Active includes high frequency, active and reactive power changes, etc. Passive includes voltage phase jump, frequency change and so on. The island protection trip outlet is generally connected to the grid-connected circuit breaker. When the island phenomenon occurs, the grid-connected circuit breaker is cut off. Therefore, the island protection device must have the voltage and frequency of the dot. Then when the voltage, frequency fluctuation and greater than the custom trip outlet action, disconnect the grid-connected switch.

The configuration requirements for anti-island protection are as follows:

1. Low frequency protection

The low-frequency protection is enabled only when the frequency is between 35HZ and 65HZ and has been higher than the low-frequency value. The low-frequency protection action returns immediately after 200ms.

2, over frequency protection

Protection starts when frequency ** is set.

3, low pressure protection

Action when the voltage is fixed

4, overvoltage protection

Action when the voltage is fixed

5. Connect optical fibers

Support the substation side optical fiber tie-in, that is, when the substation side tie-in command is received, delay the opening of the trip exit and switch the grid connection switch of the station.

6. Abrupt change in frequency

When the frequency fluctuation value * exceeds the set value, the protection action. For the distributed photovoltaic power generation that is going to be connected to the grid, the anti-island protection equipment is the equipment installed. The acquisition analog quantity includes current and voltage. Generally, the voltage transformer and current transformer on the grid-connected switch belong to the power grid side, so the analog quantity of island protection device is taken from the grid-connected switch.