Testing loop impedance in an RCCB electrical test circuit
AssigneeMegger Limited
InventorsEdward Smithson, Rongkai Xu, Agung Kurniawan Sadya Mandala, Freddie Yun Heng Chin
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Abstract
A method and apparatus for testing the loop impedance in residual current circuit breaker (RCCB) protected circuits is provided. An alternating test current is applied across the phase earth connections of a supply and a plurality of voltage samples are then taken across the connections. The voltage samples are subsequently transformed from time space to frequency space to allow the component due to the test current to be isolated. The loop impedance is then calculated.
Claims35
A method for testing loop impedance in an RCCB protected AC electrical circuit, comprising the steps of:
- applying an alternating test current to the RCCB protected AC electrical circuit at a test frequency substantially lower than an AC supply signal frequency, the magnitude of the test current being lower than the RCCB trip level, thereby affecting a test voltage between line and earth connections of the electrical circuit;
- taking, from the test voltage, a plurality of voltage samples across a time period at a rate determined by a sampling frequency;
- transforming the voltage samples from time space to frequency space, thereby producing a frequency dependent transformed test voltage;
- and,
- calculating the loop impedance using a value of the transformed test voltage observed at the test frequency.
An apparatus for testing loop impedance in an RCCB protected AC electrical circuit, comprising:
- a test signal generator adapted to apply an alternating electrical test signal to the RCCB protected electrical circuit at a frequency substantially lower than an AC supply signal frequency, the magnitude of the test current being lower than the RCCB trip level, thereby affecting a test voltage between line and earth connections of the electrical circuit;
- a sampler adapted to take, from the test voltage, a plurality of voltage samples across a predetermined time period at a rate determined by a sampling frequency;
- and,
- a signal processor, adapted to transform the voltage samples from time space to frequency space, thereby producing a frequency dependent transformed test voltage, and calculate the loop impedance using a value of the transformed test voltage observed at the test frequency.
Dependencies are inferred from the claim text.