Method of determining a temperature of a heating element of a wind turbine blade

A method of determining a temperature of a heating element of a wind turbine blade, the method comprising:

• heating the heating element by providing a heating current in the heating element;
• measuring a first value of the heating current at a first time;
• determining a first temperature of the heating element;
• and
• measuring a second value of the heating current at a second time,
• wherein the first temperature of the heating element is determined using the measured first value of the heating current, the measured second value of the heating current, and a known functional dependency between the heating current in the heating element and the temperature of the heating element.

A system for determining a temperature of a heating element of a wind turbine blade, the system comprising:

• a current sensor for measuring a first value of a heating current in the heating element at a first time and for measuring a second value of the heating current at a second time;
• and
• a controller configured for determining a first temperature of the heating element using:
• the measured first value of the heating current;
• the measured second value of the heating current;
• and
• a known functional dependency between the heating current in the heating element and the temperature of the heating element.

A method for determining a performance degradation characteristic of a heating element of a wind turbine blade, the method comprising:

• applying a voltage to the heating element to provide a heating current in the heating element for heating the heating element, wherein the heating current is provided during a heating cycle of the heating element;
• performing a cold measurement of the heating current at an initial phase of the heating cycle before the heating current causes the heating element to substantially heat up, wherein the cold measurement yields a measured value of the heating current;
• and
• determining a performance degradation characteristic of the heating element using the measured value of the heating current and the applied voltage.