Audiens® IIs CableID is our innovative apparatus for identifying dead underground power utility cable using non-clamping method.
Cable identification is defined as the positive selection of a particular cable that lies within a bunch of cables, and is necessary when cables need to be diverted for reasons such as, but not limited to, re-routing of roads, construction of culverts, looping in and out to a new substation from an existing distribution network and facilitating cable fault repairs.
Cable identification at cable termination in electric utility substation is straightforward. However, cable identification at intermediate cable portions is more complicated, especially if the intermediate cable portions are buried underground together with many similar power utility cables in close proximity in urban areas due to congestion and if underground conditions are complex. Accordingly, underground cable identification in urban areas is fraught with difficulties and prone to wrong identification.
Many existing cable identification methods, known as current transducer (CT) type, identify the dead cable mainly by determining current pulse polarity. CT type methods face many issues:
- CT clamping must be in the correct direction – incorrect clamping direction will result in identification of wrong cable;
- the risk of incorrect clamping direction is increased if a cable in a joint pit has a ‘S’ shape or ‘IT turn route;
- CT clamping contacts can become unreliable due to dust and dirt in the joint pit.
Any clamping method including non-CT type requires every cable to be tested (clamped) be fully excavated which is not always possible especially in highly congested urban areas.
Certain other methods, known as audio type (AT), apply audio frequency signal (tone) to cable conductors and use a probe to pick up the tone in field to do cable tracing or identification without clamping around the cable under test. These methods are mostly related to communication wire tracing, low voltage live power wire tracing or specific Digital Signal Processing (DSP) technique like compressed filtration. They are not relevant to power utility cables with armouring, twisting conductors and wide voltage range from LV (such as 400VAC) to HV (such as 66kVAC) and do not provide a reliable method to identify dead power utility cables from its adjacent power utility cables of close proximity, live or dead.
Our patent pending non-clamping method and apparatus – Audient® IIs Cable Identifier provides an innovative and effective way for identification of dead underground power utility cable.
The method comprises:
- forming a complete circuit by connecting a transmitter to two of a plurality of conductors of a target dead power cable at a first end thereof;
- short-circuiting and grounding the plurality of conductors at a second end of the dead power cable; injecting an audio frequency current signal from the transmitter into the complete circuit;
- within a pit which at least partially exposes a plurality of underground power cables:
- detecting a first audio frequency magnetic flux signal on a surface of a random first one of the underground power cables;
- detecting a second plurality of audio frequency magnetic flux signal on respective surfaces of some of the underground power cables being spatially-adjacent to the first one of the underground power cables;
- identifying the first one of the underground power cables as the target dead power cable if a peak amplitude of the first audio frequency magnetic flux signal as displayed on a display device exceeds any peak amplitude of the second plurality of audio frequency magnetic flux signals as displayed on the display device by more than about 50%.
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