Method for detecting water leakage of coil and water leakage detector applicable to this method

A method of detecting water leakage in a coil, which determines whether or not cooling water leaks into an insulation layer, the water being supplied to a conductor of a coil covered with the insulation layer, comprising the steps of:

• applying an AC voltage to the conductor;
• bringing a surface electrode device into pressure contact with the insulation layer;
• measuring a phase difference between a potential waveform of the surface electrode device and a waveform of an applied voltage by grounding the surface electrode device through an impedance;
• and
• determining that the cooling water leaks from the conductor to the insulation layer when a measured phase difference is different from a normal coil.

A method of detecting water leakage in a coil, which determines whether or not cooling water leaks into an insulation layer, the water being supplied to a conductor of a coil covered with the insulation layer, comprising the steps of:

• applying a DC voltage to the conductor;
• bringing a surface electrode device grounded through an impedance into pressure contact with the insulation layer;
• measuring a potential of the surface electrode device;
• and
• determining that the cooling water leaks from the conductor to the insulation layer when a measured potential is higher than a potential of a normal coil.

An apparatus for detecting water leakage in a coil, comprising:

• an AC power source for applying an AC voltage to a conductor or DC voltage source for applying a voltage stepwise upon determining whether or not cooling water supplied to a conductor of a coil covered with the insulation layer leaks into an insulation layer;
• a surface electrode device brought into contact with the insulation layer;
• an impedance inserted between the surface electrode device and ground;
• and
• a voltage measuring device for measuring a potential of the surface electrode device through a potential measurement probe and a potential meter.

An apparatus for detecting water leakage in a coil, comprising:

• an AC power source for applying an AC voltage to a conductor or DC voltage source for applying a voltage stepwise upon determining whether or not cooling water supplied to a conductor of a coil covered with the insulation layer leaks into an insulation layer;
• a surface electrode device brought into contact with the insulation layer;
• an impedance inserted between the surface electrode device and ground;
• and
• an AC voltage measuring device or an oscilloscope for measuring a potential of the surface electrode device.

An apparatus for detecting water leakage in a coil, comprising:

• an AC power source for applying an AC voltage to a conductor or a DC voltage stepwise upon determining whether or not cooling water supplied to a conductor of a coil covered with the insulation layer leaks into an insulation layer;
• a surface electrode device brought into contact with the insulation layer;
• an impedance inserted between the surface electrode device and ground;
• and
• a computer for measuring a potential of the surface electrode device though a converter.