The cable identification instrument is a device frequently used by electric power workers, mainly for the identification of important cables. It has many characteristics such as fast testing speed and high precision, and has always been welcomed by the majority of electric power workers. However, since the cable identification instrument is a high-voltage power testing device after all, there are still many issues that need attention during use. Only by using and storing it in accordance with relevant specifications can the instrument achieve the expected testing accuracy and service life. This article takes YTC601cable identification instrument as an example to briefly explain the issues that should be paid attention to when using the cable identification instrument.
1. Operators should read the instruction manual in advance to master the functions, working methods, pre-test preparation items, and correct testing requirements of the instrument.
2. Before testing, disconnect the armored grounding at both ends of the cable under test, and connect the core wire at the far end (terminal end) to the ground.
3. According to the requirements on page 2 of the manual, connect the red clip of the two output lines of the instrument to the core wire of the cable under test, and the black clip to the ground.
4. Before turning on the transmitter, you must first turn the output adjustment knob counterclockwise to zero, then turn on the power. Slowly adjust the output adjustment knob to make the output reach 5A-15A (the adjustment knob is generally adjusted within two-thirds of the range). If the system grounding resistance of the substation is greater than 4 ohms, the output current will be less than 8A. As long as the receiver meter can deflect in both positive and negative directions, normal operation can be achieved.
Note: On site, if the grounding resistance is too small, when the output adjustment knob of the transmitter is turned counterclockwise to zero, the output current will still be very large, and the protection circuit inside the transmitter will activate (manifested as a small rapid swing of the meter). At this time, the high-power test resistor (1 to 2 ohms/20W-30W) provided with the instrument can be connected in series in the transmitter circuit.
In actual testing, in the same cable trench, if there are more than two other cables connecting between two power distribution rooms, the grounding resistance becomes very small or even close to zero due to the connection of the armor of other running cables, causing the transmitter output current to be too large and the protection circuit to activate. At this time, the test resistor can be connected in series in the transmitter circuit for testing. After testing, the test resistor will be very hot. Pay attention to cooling it down before packing it. The test resistor can also be replaced by other resistors of 1-2 ohms with a power greater than 20W.
5. Before identifying cables on site, the receiver of the identification instrument should be calibrated at the starting end of the cable according to the calibration requirements in the manual.
6. The standard for identifying cables on site: when the sensor is clamped on one of the cables for testing, the receiver meter deflects to one side with a large swing. When testing on the other cables (keeping the same clamping direction of the sensor), the receiver meter deflects to the other side with a smaller swing. The more cables there are, the smaller the deflection. The cable where the receiver meter deflects to one side with a large swing is the cable that needs to be identified.
The cable identification instrument is a high-precision, high-voltage power testing device. Many issues need to be paid attention to during use. Electric power workers should memorize the above six key points during actual testing to achieve twice the result with half the effort.
