Detecting device and method for detecting a fault in a transformer of a wind turbine

1. A detecting device for detecting a fault in a transformer of a wind turbine, wherein the transformer transforms a lower voltage, which is output from a generator of the wind turbine at a low voltage side of the transformer, to a higher voltage, which is output from the transformer at a high voltage side, wherein the detecting device comprises:

a voltage detection device configured to detect a voltage at a first node at the low voltage side of the transformer;

a current detection device configured to detect a current at a second node at the high voltage side of the transformer; wherein the detecting device is configured to detect the fault in the transformer based on the detected voltage and the detected current; wherein the detecting device comprises a logic circuit, wherein the detecting device is configured to detect the fault in the transformer if the logic circuit detects at least one of the following conditions:

an open phase at the low voltage side if the voltage detection device detects a zero-sequence voltage exceeding a particular threshold and a voltage unbalance exceeding a particular threshold; and

an open phase at the high voltage side if the voltage detection device detects a zero-sequence voltage falling below a particular threshold and a voltage unbalance exceeding a particular threshold.

2. The detecting device according to claim 1 , further comprising a control device configured to open a line switch so as to interrupt an output line of the transformer based on the detected voltage and the detected current.

3. The detecting device for detecting a fault in a transformer of a wind turbine according claim 1 , wherein the detecting device is configured to detect the fault in the transformer if at least one of the following conditions occurs: an overvoltage is detected by the voltage detection device, an overcurrent is detected by the current detection device and a difference between a frequency at the low voltage side or the high voltage side and a respective target frequency exceeds a threshold value.

4. The detecting device for detecting a fault in a transformer of a wind turbine according to claim 1 , wherein the detecting device is configured to detect the fault in the transformer if at least one of a phase overcurrent, a zero-sequence or neutral overcurrent and a negative sequence overcurrent is detected by the current detection device.

5. The detecting device for detecting a fault in a transformer of a wind turbine according to claim 1 , wherein the detecting device is configured to detect the fault in the transformer if at least one of an undervoltage, a zero-sequence or neutral voltage and a Total Harmonic Distortion (THDv) over a defined level is detected by the voltage detection device.

6. The detecting device for detecting a fault in a transformer of a wind turbine according to claim 2 , wherein the detecting device is configured to detect the fault in the transformer if an external trip signal is input into the control device.

7. The detecting device for detecting a fault in a transformer of a wind turbine according to claim 1 , wherein the detecting device further comprises the line switch which is arranged in an output line of the transformer behind the second node at the high voltage side.

8. A wind turbine comprising a detecting device according to claim 1 .

9. A method of detecting a fault in a transformer of a wind turbine wherein the transformer transforms a lower voltage, which is output from a generator of the wind turbine at a low voltage side of the transformer, to a higher voltage, which is output from the transformer at a high voltage side, the method comprising the following steps:

a voltage detection step to detect a voltage at a first node at the low voltage side of the transformer;

a current detection step to detect a current at a second node at the high voltage side of the transformer; and

a detecting step to detect the fault in the transformer based on the detected voltage and the detected current; wherein the detecting step detects the fault in the transformer in at least one of the following conditions:

an open phase at the low voltage side if the voltage detection step detects a zero-sequence voltage exceeding a particular threshold and a voltage unbalance exceeding a particular threshold; and

an open phase at the high voltage side if the voltage detection step detects a zero-sequence voltage falling below a particular threshold and a voltage unbalance exceeding a particular threshold.

10. The method according to claim 9 , further comprising

a controlling step to open a line switch so as to interrupt an output line of the transformer behind the second node based on the detected voltage and the detected current.

11. The method according to claim 9 , wherein the detecting step detects the fault in the transformer if at least one of the following conditions occurs: an overvoltage is detected in the voltage detection step, an overcurrent is detected in the current detection step and a difference between a frequency at the low voltage side or the high voltage side and a respective target frequency exceeds a threshold value.

12. The method according to claim 9 , wherein the detecting step detects the fault in the transformer if at least one of a phase overcurrent, a zero-sequence or neutral overcurrent and a negative sequence overcurrent is detected in the current detection step.

13. The method according to claim 9 , wherein the detecting step detects the fault in the transformer if at least one of an undervoltage, a zero-sequence or neutral voltage and a Total Harmonic Distortion (THDv) over a defined level is detected in the voltage detection step.

14. The method according to claim 9 , wherein the controlling step opens the line switch if an external trip signal is input.