Power cable fault locator

Purpose:

T-505Power cable fault locatorIn conjunction with a high-voltage signal generator, acoustic magnetic synchronization testing can be performed to locate high resistance and flashover faults in power cables, while also detecting the path. Combined with an audio signal generator, audio induction testing can quickly and accurately detect cable paths, locate low impedance faults, and perform cable identification and depth measurement.

Features:

Fully functional, capable of pinpointing and determining cable paths for various cable faults.

High measurement accuracy, with errors of no more than 0.2 meters for high impedance fault location and path detection, and no more than 2 meters for low impedance fault location.

The instrument has two working modes: acoustic magnetic synchronization and audio induction, each using two different probes. After replacing the probe, the instrument automatically switches working modes.

Synchronize the sound and magnetic field signals generated by the discharge of cable fault points, with strong anti-interference ability.

The cursor can be used to determine the delay between sound and magnetic field signals, thereby determining the distance of the fault point.

The detection method mainly relies on waveform recognition, supplemented by headphone listening, to eliminate auditory errors and reduce fatigue during operation.

For different types of faults and fixed-point environments, the instrument provides two triggering and non triggering methods for the headphones to listen to faults during fixed-point, enabling operators to quickly and effectively determine the fault location and achieve accurate fixed-point.

The signal waveform is displayed on a large LCD screen, which is intuitive and easy to recognize.

It can be powered by rechargeable lithium-ion batteries or easily replaceable dry batteries.

Equipped with backlight, automatic shutdown, and charging protection circuit.

Easy to operate, aesthetically pleasing, and portable.

Power cable fault locatorTechnical Indicators:

High resistance fault location accuracy: ≤ 0.2m

Path detection accuracy: ≤ 0.2m

Low resistance fault location accuracy: ≤ 2m

Power consumption: 1.5W

Charger input voltage: AC: 220V ± 10%

Charger output voltage: DC: 9.1V

Volume (host): 200mm × 90mm × 165mm

Quality (host): 1kg

Operating temperature: -10~40 ℃

Structure of the instrument:

1. Whole machine composition

host

Attachment, packed in backpack, including:

Acoustic magnetic probe

Lift the bar, handball

probe

earphones

charger

2. Composition and function of the panel

The input and output sockets, display devices, and adjustment knobs of the fixed-point instrument are mostly arranged on the panel, as shown in Figure 4-1.

Figure 4-1 Panel of the fixed-point instrument

Signal input jack: connected to a probe output cable, used for inputting signals.

Earphone socket: Connect the headphone plug for listening purposes.

Magnetic field gain knob: used to adjust the gain of the instrument's magnetic field amplifier during acoustic magnetic synchronization testing, so that the instrument can be correctly triggered by the magnetic field signal emitted by cable breakdown discharge.

Sound gain knob: used to adjust the gain of the instrument's sound amplifier, so that the amplitude of the sound waveform displayed on the screen is large enough without distortion, and the headphone listening experience is clear and not harsh.

Synchronous indicator LED: During acoustic magnetic synchronization testing, when the instrument is triggered by a magnetic field signal, it emits light for about 0.2 seconds, indicating that the fault point has been discharged. If the detection point is within a few meters of the fault point, a discharge sound different from the ambient noise can be heard at this time.

LCD screen: used to display instrument waveforms and prompt information.

Charging socket: used to connect a charger and charge the lithium-ion battery inside the instrument. When the indicator light on the charger is red during the charging process, it indicates that it is rapidly charging; When the indicator light turns green, it indicates that the charging is complete.

The functions of each button are as follows:

Key: Used to turn on/off the power of the instrument.

Backlight button: When the surrounding environment is dark and the content displayed on the LCD is not clear, press this button to turn on the LCD backlight and obtain a clear image. Press it again to turn off the backlight. After the backlight is turned on for half a minute, the instrument will automatically turn it off.

Pause button: It can pause the triggering of the instrument for careful observation and analysis of the waveform. At this time, the screen will flash with the words "Pause Trigger". Press it again to restore normal operation.

Memory key: Press this key to store the current waveform in the memory, and the last stored waveform will be flushed out.

Comparison key: Used in conjunction with the memory key. Press this button, and the instrument will display the memorized waveform on the screen, which can be compared with the current waveform after each screen update. Press the key again, and the waveform of the memory will disappear.

Trigger button: used to switch the listening mode of the headphone sound. The cable fault locator provides two types of sound listening triggering and non triggering modes (default) to cope with different types of cable faults and adapt to different working environments. This makes it more convenient, fast, and accurate to locate cable faults.

<and>keys: the left and right arrow keys of the cursor. Press it once, and the cursor will move left or right. If the hand does not leave after pressing the key, the cursor will continue to move rapidly. Lift the hand and the cursor will stop moving.

When conducting acoustic magnetic synchronization testing, the cursor keys are used to calibrate the size of the acoustic magnetic delay. Move the cursor to the beginning of the discharge sound waveform at the fault point, and the acoustic magnetic delay value will be displayed in the upper right corner of the sound waveform box. The cursor is in another position, and the displayed time value is meaningless.

Acoustic magnetic synchronization test: (in conjunction with a high-voltage signal generator)

The acoustic magnetic synchronization test is suitable for detecting high resistance and flashover faults in power cables, and can detect the path of the cable at a fixed point.

This method requires the cooperation of a high-voltage signal generator.

1. Working principle

(1) Principle of Acoustic Magnetic Synchronous Path Detection

When a high voltage causes a cable fault to click through, a strong instantaneous current will generate a magnetic field signal around the cable (throughout its entire length), as shown in Figure 5-1:

The initial direction (polarity) of the magnetic field generated by the pulse current on both sides of the cable is opposite. The instrument collects magnetic field signals at different positions and displays the waveform on the LCD screen. When it is determined that the initial direction has changed, it means that the instrument probe has moved to the other side of the cable. This method can be used to repeatedly detect and determine the path of the cable.

(2) Principle of High Resistance Fault Location:

The high resistance fault point of the cable discharges under high voltage, generating magnetic field signals around the cable and vibration sound signals at the fault point. Directly above the fault point, the sound takes the least time to travel from the fault point to the ground, while the perceived sound intensity is the highest.

The instrument collects the magnetic field and sound signals generated when a cable fault occurs, displays the waveform on the LCD screen, and outputs the sound through headphones for listening. When receiving the discharge sound signal from the fault point, moving the cursor can calibrate the time difference (acoustic magnetic delay value) between the sound and the magnetic field signal reaching the probe. Since the propagation speed of the magnetic field is much higher than that of the sound, the propagation time of the magnetic field can be ignored. The acoustic magnetic delay value is the required propagation time of the sound signal from the fault point to the probe. According to the formula: distance=time x speed, the distance of the fault point can be determined (as it is difficult to determine the propagation speed of sound in different media, the distance of the fault point cannot be accurately calculated based on the acoustic magnetic delay value). By listening to the sound and judging the amplitude of the sound waveform, the intensity of the sound can also be identified. The point with the smallest acoustic magnetic delay value and the highest sound intensity is the fault point.

2. Preparatory work

(1) Fault location measurement

When a cable failure occurs, please first use a power cable fault rangefinder to measure the fault distance. For detailed usage instructions, please refer to the rangefinder's operating manual.

(2) High voltage equipment wiring and use

In order to locate the fault, a high-voltage generating device should be connected to one end of the cable, and a high-voltage impulse pulse should be applied to the cable to cause the cable fault to click through and discharge. The grounding fault location of the core wire and the wiring of high-voltage equipment are the same as the flashing method used for fault location, as shown in Figure 5-2:

In the picture:

T1 is a voltage regulator;

T2 is a high-voltage test transformer;

D is a silicon stack;

G is the ball gap;

C is a capacitor, and a model with a larger capacitance should be selected, especially when the fault distance is far away. Large capacity capacitors can generate strong sound signals at the fault point, making it easy to locate the fault. Generally, capacitors with a capacity of 1 to 4 microfarads and a rated voltage of 6 kV or 10 kV are used.

The above complete set of equipment can use our company's high-voltage signal generator for better results.

Adjust the interval of the ball gap, then connect the high-voltage equipment power supply, gradually increase the voltage until the ball gap discharges. If the discharge sound of the ball gap is loud, the fault point has generally been penetrated (at this time, a cable fault rangefinder can also be used to monitor whether the fault point has been discharged). If the fault point is not broken down, the discharge voltage needs to be increased. Firstly, stop the high-voltage equipment, discharge the charges on the capacitor and cable, increase the gap between the balls, and repeat the above process until the fault point can be broken down and discharged.

The larger the capacity of a capacitor, the higher the discharge voltage, and the stronger the sound signal emitted by the discharge at the fault point, making it easier to detect. However, the discharge time interval of high-voltage equipment will be extended, increasing the time required for fixed-point detection. It is necessary to select the capacitor capacity and adjust the discharge voltage reasonably according to the actual situation, in order to facilitate rapid positioning.

At the fault point, if the fault point is relatively close to the high-voltage equipment, the sound of ball gap discharge may be received by the probe and difficult to distinguish from the sound signal of the fault point discharge. In this case, the discharge equipment can be moved to the other end of the cable for further positioning.

For pure wire breakage faults, the ground wire should be short circuited to the fault at the far end of the cable.

If the wire is disconnected and grounded with a resistor, the wiring method in Figure 5-2 should be used as much as possible, so that the discharge occurs between the core wire and the ground, and the sound signal is easily transmitted to the ground. For individual short-circuit faults (with low fault resistance close to zero), due to the inability to trigger discharge or the very weak sound signal emitted by discharge, audio induction method should be used for detection (see Chapter 6 "Audio Induction Method Testing").

3. On site installation of instruments

Insert the output cable plug of the acoustic magnetic probe into the signal input jack on the front panel of the instrument, place the probe flat on the ground, and use it to receive signals;

Insert the headphone plug into the headphone output jack on the front panel of the instrument for listening to sound;

Screw the lifting rod into the screw hole on the upper part of the probe for easy carrying;

If the ground on site is relatively soft, the probe can be screwed into the bottom of the probe and inserted vertically into the ground to improve detection sensitivity.

Notes:

The probe of the instrument should avoid strong impact.

When the instrument exhibits the following phenomena, users can handle them themselves:

Turn on the instrument, there is no display on the screen

Reason: The internal battery voltage of the instrument is too low

Solution: Charging

Turn on the instrument, the screen displays, but it automatically shuts down after a few seconds

Reason: The internal battery voltage of the instrument is too low

Solution: Charging

crash

Reason: The instrument is strongly interfered with

Solution: Shut down and restart

When the malfunction of the instrument cannot be easily eliminated, please do not repair it yourself to avoid expanding the scope of the fault. Please contact our company for timely repair.