Electronic No-Load Voltage 7500V High-Resistance Cable Fault Detection Sheath Fault Pre-Location High-Voltage Bridge
The cable outer sheath fault tester is designed based on the MURRAY bridge principle and can be used to locate the breakdown points of various wires and cables and the defect points that have no breakdown but low insulation resistance values.
The equipment uses an electric voltage regulator and an R-type transformer to form a high-voltage constant current source, and the button operation can increase or decrease the voltage.
The no-load voltage is 7500V, the short-circuit current is 100mA, and a high-sensitivity amplifier and galvanometer are used to indicate balance. It forms a balanced bridge with a proportional potentiometer, and the whole is placed at a high potential.
The measurement cable is a specially designed two-core high-voltage rubber cable. The four-terminal resistance measurement method is used to avoid errors caused by lead resistance.
The entire panel is at low potential. One-touch operation, enter the cable length and automatically calculate the fault distance. The high voltage source and bridge are integrated in a portable protective box. Therefore, the device has high voltage, light weight, easy operation and safe use.
Features
Output voltage is adjustable;
Has high accuracy and stability;
Adopt high-sensitivity amplifier and galvanometer to indicate balance;
Zero protection;
Automatically test fault points, but retain manual testing functions;
Compared with the wave reflection method, the bridge balance method has no blind area and is used to determine the breakdown point of short cables and near the ends.
High voltage bridges are particularly suitable for
1. The high-resistance breakdown point of the cable after laying, especially the linear high-resistance breakdown point that is difficult to burn into low resistance, such as the linear high-resistance breakdown of the cable intermediate joint.
2. Flashover type breakdown point. After breakdown, the constant current source can maintain the arc, a stable current flows through the bridge, and the bridge has sufficient sensitivity.
3. Defects that have not yet broken down but have low resistance, such as insulation defects found with a megohmmeter that have low cable resistance but do not break down under the operating voltage.
Technical specification
No-load voltage | ≥7500V; |
Short-circuit current | ≥100mA (when adjusting balance, it is recommended to set it at 5~40mA); |
Positioning proportion accuracy | ±(0.2%·L±1) meters; |
Weight | 25kg; |
Working power supply | AC 220V (±10%), 50Hz±1Hz; 8.4V built-in battery. |
Working principle
The principle of the cable fault location bridge method is as follows: short-circuit the fault phase and the non-fault phase of the cable under test, connect the two arms of the bridge to the fault phase and the non-fault phase respectively, and adjust an adjustable resistor on the two arms of the bridge to make the cable Bridge balancing, using proportional relationships and known cable lengths, allows the distance to fault to be determined.
The advantage of the cable fault location bridge method is that it is relatively simple, and its accuracy meets the requirements of on-site engineering testing. It is very convenient to measure two-phase short-circuit faults in cable lines. Using the Murray bridge to locate the breakdown point is a classic method, which is convenient and accurate.
The bridge method is based on the fact that the resistance of the wire core (or shielding layer) is uniform and proportional to the length. The following figure shows typical usage:
Panel description
1. Galvanometer: electrical balance zero point is adjustable;
2. Ammeter: output current indication mA meter;
3. Voltmeter: high voltage output voltage indication kV meter;
4. High-voltage indicator light: This light lights up when there is high-voltage output;
5. Display: displays the operation content;
6. Zero indicator light: When this light is on, it indicates that the voltage output is in zero state;
7. Power socket: instrument working power supply, AC 220V connection port;
8. Fuse holder: The installation place of the fuse of AC 220V power supply system;
9. Power switch: "I" turns on the AC 220V power supply switch, "0" turns off the system power;
10. Start button: When the zero light is on, it means that the voltage output is in the zero state. When it is on, the start button is effective. If the zero light does not light up after turning on the power switch, press the step-down button until the light is on. When the zero light is on, , press this button to start high voltage and generate high voltage output;
11. Stop button: When the test is completed or an abnormality occurs, press this button to cut off the high-voltage output;
12. Boost button: Press this button to increase the output high voltage from small to large;
13. Pressure reduction button: Press this button to reduce the output high voltage from high to low;
14. Selection: "Select" encoder switch operation convention: rotation---cursor movement or number modification operation;
Press---Perform or confirm the operation.
15. Sensitivity adjustment: ①. Built-in battery-powered switch; ② Adjust the sensitivity and use it with the zero adjustment knob;
16. Zero adjustment knob: Rotate the zero adjustment knob to make the galvanometer point to zero;
17. Balance adjustment: Adjust the balance knob until the galvanometer deflects significantly so that the galvanometer points to zero. (If the pointer is to the left, rotate clockwise; if the pointer is to the right, rotate counterclockwise). Observe and record its reading P1;
18. Indicator light: Built-in battery working indicator light, this light will turn on after the sensitivity adjustment is turned on;
19. Reference item: The black clip of the output line is connected to the reference phase;
20. Faulty phase: The red clip of the output line is connected to the faulty phase;
21. Charging: DC8.4V charging port, connect the 8.4V charger to start charging;
22. Grounding post: instrument grounding point, safety protection.
The actual wiring is as shown below:
■HV is a high voltage constant current source.
■Faulty cable CD and auxiliary cable AB have the same core cross-section and length L, and the distance between the fault point and the measuring end is X.
■The measurement clamp is connected to both ends of the cable core A and C. The two sides of the clamp are the current and potential ends, which should be reliably connected to the cable.
■R is the balance potentiometer, and its reading is percentage.
■G is a galvanometer, the electrical balance zero point is adjustable.
■At the remote end, both ends of BD must be short-circuited and the short-circuit must be ensured securely.
Measurement steps:
Preparation (determine the faulty phase and wire correctly)
1. Use a multimeter, megger or other voltage-resistant equipment to confirm the breakdown status of the cable, and record the insulation resistance to ground or breakdown residual voltage of each core.
2. Record the length, model, cross-section and other parameters of the cable to be tested, patrol along the cable laying path, short-circuit the faulty cable and auxiliary cable outlet terminal at the remote end, and leave someone to monitor at the remote end to prevent high voltage from hurting people.
3. Wiring. The ground terminal of the instrument must be connected to the ground body at the location.
The first end of the measurement (red clip) is connected to the core of the faulty cable, and the end of the measurement (black clip) is connected to the core of the auxiliary cable.
Measurement (proportion of fault detected by boosting voltage)
4. The power supply is connected to AC220V. Turn on the sensitivity switch and rotate it to the maximum, the battery indicator light will turn on.
5. Zero adjustment of the bridge (when the galvanometer pointer is not at zero). Turn the zero adjustment knob to make the galvanometer point to zero.
6. Boost. Turn on the power switch and the zero indicator light will light up. If it does not light up, click the voltage reduction button until the light turns on. Then click the start button and the high voltage indicator light will turn on.
7. Click the boost button and observe the voltmeter and ammeter until the ammeter exceeds 20mA. If the current is unstable, you can continue to increase the voltage and maintain it for a period of time to form a stable arc or conductive area to stabilize the current during the test.
8. Balance adjustment. Adjust the balance knob until the galvanometer deflects significantly so that the galvanometer points to zero. (If the pointer is to the left, rotate counterclockwise; if the pointer is to the right, rotate clockwise). Observe and record the reading P1 of the dial, and stop boosting the voltage after measuring the fault ratio.
Calculation (automatically calculates the distance to fault)
9. After turning on the power, enter the welcome page and automatically enter the next page in 2 seconds
10. Enter the cable length
"Select" encoder switch operation convention: rotation---cursor movement or number modification operation
Press---Perform or confirm the operation.
Enter the cable length page (the initial value is %, increase clockwise and decrease counterclockwise.)
Rotate the "select" encoder switch left and right, move the cursor to the "0000" position where the data needs to be modified, press the "select" encoder switch to determine the current position, rotate the "select" encoder switch, the current position number will be from "0 to 9" change, and then press the "select" encoder switch to confirm the input number, the cursor will automatically move to the next digit, and the input of each digit value (i.e., cable length L) will be completed in sequence. When the cursor is on Next, press the "Select" encoder switch to enter the next page
11.Test page
When the cursor is on Test, press the "Select" encoder switch, and the system will automatically collect the primary bridge proportional coefficient P (balance scale reading) and calculate the fault distance X. Collect once per click.
When the cursor is on Last, press the "Select" encoder switch to return to the previous page (10. Input page).
When the cursor is on Next, press the "Select" encoder switch to enter the next page
12. Result page
Display measurement results.
When the cursor is on Last, press the "Select" encoder switch to return to the previous page (11. Test page).
When the cursor is on Rest, press the "Select" encoder switch, reset and restart, and enter (9. Welcome page).
Reverse connection to check calibration: voltage reduction and discharge. Exchange the measuring clamps and repeat steps (4) to (12) to obtain another reading P2, which should be calculated as P1+P2=100.
The location of the fault point is X=2×L×P1% , Special attention should be paid to the "2" in the formula, since adding an auxiliary cable doubles the length of the cables involved in the calculation.
Packing list
Host(main unit) | 1set |
High power connection wires | 1set |
Power cable | 1pcs |
Output cable(red, black) | 1set |
Ground wire | 1pcs |
Charger | 1pcs |
Fuse(3A) | 5pcs |
More photos and test site
Company profile
XZH TEST is a professional cable fault detection equipment manufacturer. We are a young team. Our development philosophy is humanized management, intelligent cloud-based products, and internationalized operations. Our development mission is to make electrical equipment free from undetectable failures.
Since its inception in 2013, our company has grown to become one of the largest manufacturer of underground cable fault detection equipment in China. An ISO 9001 and CE certified company, we produces a broad range of testing equipment.
What we can do
We have the ability to innovate new products and technologies.
We can provide complete system solutions for your project.
We provide online and offline practical and theoretical training.
We provide instrument repair and calibration.
FAQ
1. Are you a trading company or a manufacturer?
We are a professional manufacturer with more than 10 years of experience. We can strictly control the quality of parts and finished products.
2. What is the delivery time and inventory?
If our best-selling products are in stock, it will be 5-8 working days for shipment. But for mass production and customized production, the time will take 2-4 weeks.
3. What are your payment terms?
Payment ≤ USD 2000, 100% T/T prepayment. Orders over USD 2000 can be negotiated.
4. How long is your product warranty?
We provide 1 year warranty for the equipment.
5. How do you ensure quality?
The product links include R&D, manufacturing, commissioning and technical support, following strict and scientific management principles. Therefore, we can support strong production and R&D capabilities, and can produce high-quality products at competitive prices to meet customers' high requirements.
6. What support can I get?
We will provide training support, marketing support, technical support and supply chain support. You can contact us for more information.
7. Where is your factory? Can I visit your factory?
We are located in Xi'an, Shaanxi, China. We are close to Xi'an Xianyang International Airport, which is about 2 and half hours by plane from Shanghai and Guangzhou. All customers from all over the world are welcome to visit us.
8. How to become your dealer?
Every company interested in power system instruments can contact us without hesitation, including website letters, emails, telephones, etc. We will contact you quickly according to your company information and cooperation intentions.