T-P23 low voltage fault locator for finding intermittent faults on live cables

The Kehui T-P23 has been designed for locating all types of low voltage cable fault, but especially the difficult and troublesome transient and intermittent fault. It is especially suitable for branched cables. The T-P23 has three modes of operation; Time Domain Reflectometry (TDR) where a single unit is used, Travelling Wave (TRS) using simultaneous testing from two units and Voltage Gradient using records from two or more units. The unit can be connected to a suspect cable and can then be controlled locally from a portable PC through its internal Bluetooth transceiver, or remotely over the Internet using its integral GSM/GPRS modem. The resulting signals can be examined in the T-P2X system software to identify the position of the fault.

LV cable systems are susceptible to transient fault conditions. Damage to an underground cable may only become apparent when moisture causes the fault to ignite resulting in flickering lighting or the rupturing of the associated fuse. The heat of the fault can cause the moisture to evaporate apparently returning the system to normal and allowing the fuse to be successfully replaced. However, the underlying problem remains.

The situation is further complicated by the construction of LV systems in many parts of the world, which do not allow the isolation of the suspect part of the cable. This prevents it from being treated by an HV surge generator to make the fault permanent. The situation is further complicated as the cables have many branches with direct connections to customers’ premises.

One solution is to monitor the cables with a T-P23 acting as a Time Domain Reflectometry (TDR) unit regularly injecting TDR signals into the cable. The data can then be stored on a cyclic basis, until such time as a fault occurs. The fault will trigger the T-P23 and saves the data in such a way that the location can be determined through the comparison of pre and post fault data.

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