Darui Electric recommends
Equipment Operating Environment Conditions:
1. Ambient medium temperature: -5℃ to +40℃;
2. Relative air humidity: not greater than 85% (when temperature is 20℃±5);
3. Altitude: not exceeding 2500m;
4. No explosive medium around, and no gas or dust that can corrode metals or damage electrical insulation;
5. No significant impact or vibration, and no place where rain or snow can intrude.
Structural Features:
1. This equipment consists of a control part (low voltage) and high-voltage rectification, discharge, and testing parts. Sufficient safety space is reserved between high and low voltage, and between high/low voltage and the casing.
2. To ensure the safety of equipment and personnel, the high-voltage start must be operated by a dedicated person with a key.
3. Each time flaw detection or cable testing is performed, it is ensured that high voltage starts from zero and gradually increases. There are high and low voltage limit shapes. The voltage increase or decrease process is controlled by buttons, with stable voltage change rate, safe and simple operation.
4. The DC withstand voltage test time can be automatically controlled by a digital timer (or manually controlled), with accurate and reliable test time.
5. Leakage current can be measured at any time as needed during the withstand voltage test.
6. The equipment has overcurrent and short-circuit protection, with start-up pre-alarm and overcurrent protection.
7. The control panel is equipped with power switch, high-voltage start, high-voltage stop, voltage increase, voltage decrease switches or buttons, and a digital timer relay for withstand voltage test, etc.
8. The display panel has meters for high voltage, leakage current, and low-voltage total current, with indicator lights for power, high voltage, timing, and an observation window for sphere gap discharge.
9. A dedicated high-voltage discharge rod is provided for discharging after each flaw detection or test to ensure safety. The bottom of the box has a grounding symbol.
Instructions:
Principle
1. Preparation before testing
a. Before use, the equipment casing must be reliably grounded, with grounding resistance not greater than 4 ohms.
b. Before testing or use, carefully inspect the equipment inside and outside. Keeping the equipment, especially the high-voltage terminals and wires, clean is crucial.
c. The maximum working voltage of this equipment can be adjusted and limited to 30KV for capacitive loads.
d. Avoid severe vibration when moving the equipment. After moving, it must be left for 1 hour before use.
e. The high-voltage meter scale is calibrated for a capacitive load of 0.01μF.
f. After properly installing the discharge rod, fix its grounding terminal to the box grounding bolt with a screw, and place it on top of the box.
2. Cable flaw detection test
a. On the back of the box, reliably short-circuit the high-voltage terminals and with a copper nut and short-circuit plate.
b. Connect the cable core to be tested to the high-voltage terminal on the back of the box. Short-circuit the other cores, shielding wires, and ground wires and connect to the terminal. Adjust the discharge sphere gap to 1-2mm.
c. Close the power switch ZK in the box, turn the changeover switch to the flaw detection position, start the control power with the key, press the bell warning button LK to make the bell DL emit a start warning, press the high-voltage box, and press the voltage increase button until the sphere gap discharges.
d. Inspect along the cable length to determine the damaged location and mark it. If the damage is not easily found after discharge, appropriately increase the sphere gap to enhance discharge intensity, making the fault point more clearly exposed.
e. Repeat the above steps until all wounds on each core are identified (Note: after each operation, reliably discharge all parts with the discharge rod before proceeding to the next operation).
3. Cable withstand voltage and leakage current test
a. Disconnect the short-circuit plate between the high-voltage output terminals on the back.
b. Connect the cable core to be tested for withstand voltage to the high-voltage output terminal or, short-circuit the other cores, shielding wires, or ground wires and connect to the ground terminal.
c. Close the power switch ZK in the box, start the control power with the key, turn the changeover switch to the withstand voltage test position, preset the test time, press the alarm to make DL emit a warning, press high-voltage on, then press the voltage increase button. After increasing voltage, automatic timing will start.
d. If no breakdown or flashover occurs within the specified time, it is qualified.
e. During the withstand voltage test period, the leakage current value of the cable can be read on the microammeter.
f. Switch to other cores and repeat the above steps until the entire cable is tested.
4. Precautions after use
a. After each test, immediately disconnect QK and use the discharge rod to fully discharge the test piece and all high-voltage parts.
b. Before leaving work every day, cut off the external main power switch (capacity not less than 50A) and turn off the internal ZK switch.
Operating Precautions:
1. Lay an insulating rubber mat in front of the equipment.
2. Operators should wear insulating rubber shoes and insulating gloves.
3. The cable core under test should be firmly fixed to the high-voltage terminal with a nut, maintaining good contact to avoid leakage and increased current due to *discharge.
4. Unrelated personnel should be prohibited from approaching the work site.
5. After one year of use, the transformer oil should be promptly checked for withstand voltage, which must not be lower than 30KV/2.5in.
6. Periodically (depending on equipment usage intensity), use zero-grade sandpaper to carefully polish the surface of the discharge copper sphere, keeping the surface and surroundings clean and dust-free.
7. The effectiveness of this equipment depends on the careful maintenance by users and continuous accumulation of operating experience to master the relationship between sphere gap spacing and discharge voltage for different cables.
Main Technical Parameters:
Current and voltage: Single-phase AC 220V, 50Hz
Flaw detection DC output voltage: 0-30KV (button control)
Cable flaw detection accuracy: within ±50mm
Test output DC voltage: 0-30KV (button control)
Automatic withstand voltage test time: 0-30 minutes (settable)
Leakage current test range: 0-100 microamperes
Main transformer rated capacity: 3KVA
Rectification method: Single-phase half-wave
Discharge sphere gap: Adjustable by handle screw
Dimensions: 1100×1000×1200mm (width×depth×height)
Overview
Coal mines are major users of cables. Due to the harsh underground working environment, the annual damage of various cables is relatively large. To save costs and reduce production expenses, most mines have their own cable maintenance teams. However, due to limitations of testing equipment and processes, flaw detection testing of cables such as fully mechanized mining cables is often unsatisfactory, and most use the forced breakdown method that causes significant damage to cable insulation. This device uses the partial discharge method based on not destroying the original structure of the cable for flaw detection, which can simply and accurately detect the damaged parts of the cable, and also has the function of testing after repair. Therefore, it is a fully reliable tool for current coal mine cable maintenance services.
Purpose:
This equipment is specially designed for flaw detection of various mining cables below 6KV on the coal mine surface, and for DC withstand voltage testing and leakage current testing after cable repair. It is a comprehensive essential tool for cable repair and testing that meets the requirements of the "Coal Mine Electrical Test Regulations" and is highly practical.
Note: The above information and technical parameters are compiled and released by Yangzhou Darui Electric Co., Ltd.
