Abstract:The dual-frequency(DF)IP is a new kind of frequency domain IP method.Not only is the dual-frequency current transmitted simultaneously but the electric potential difference due to dual frequency current is measured synchronously.This paper discusses the principle and charateristic of DF current, DF current can be formed by two rectangular currents which must be coherent or else false Percent Frequency Effect(PEE)will occur.DF currents with different waveforms are equivalent in the ability of detecting IP anomalies.Unstable current has much less effect of DF IP than on conventional variable frequency method;in fact,there is no need to stabilize current in DF IP method.There are many differences between harmonic contents of DF current and that of rectangular wave used in variable frequency method,but theoretical analysis,labaratory mod- eling and field data all show that the anomalies of both DF and variable frequency method are sim- liar in character and close in value.DF IP can match v...更多ariable frequeney IP and time domain IP in the ability of detecting IP anomaly,furthermore,dual-frequency IP measurements are more rapid,more accurate and more simple in operation.  

Key words: dual frequency IP; percent frequency effect; IP anomaly