| 1. | Due to the use of frequency conversion technology, accurate measurement can be ensured under strong electric field interference. |
| 2. | The instrument adopts a Chinese menu operation, and the microcomputer automatically completes the entire measurement process. |
| 3. | This instrument is also suitable for measuring the tgδ and capacitance of high-voltage electrical equipment in workshops, laboratories, and scientific research institutions; it has the advantages of convenience, simplicity, and accuracy for insulation oil loss testing. |
| 4. | This instrument can measure high-voltage electrical equipment that is ungrounded or directly grounded using positive or reverse wiring methods. It can also measure the tgδ of capacitive voltage transformers and the capacitance of main capacitors C1 and C2. |
| 5. | The instrument is equipped with a high-voltage step-up transformer and adopts safety protection measures such as zero-crossing switching and lightning protection. During the test, it outputs high voltage of different levels from 0.5kV to 10kV, making operation simple and safe. |
Tester Parameters
1. High voltage output: 0.5 to 10kV, increasing by 500V per step, with a total of 20 steps
High voltage output cable can be used dragged on the ground
Three frequencies: 45Hz, 50Hz, 55Hz
2. Capacity: 1500VA
3. Accuracy: tgδ: ±(reading*1.0%+0.08%)
Cx: ±(reading*1.5%+5PF)
4. Resolution: tgδ: 0.01% Cx: 1pF
5. Measurement range: 0.1% < tgδ < 50%
3PF< Cx < 60000PF
At 10KV, Cx ≤30000PF
At 5KV, Cx ≤60000PF
6. Power supply: AC 220V ±10% 50±1Hz
7. Harmonic adaptation: ≤3%
8. Operating conditions: -15℃ to 50℃, relative humidity <80%
9. Dimensions: 460(L)×335(W)×340(H)
10. Weight: 30 kg
Working Principle:
After the variable frequency dielectric loss tester starts measurement, the high voltage setting value is sent to the variable frequency power supply. The variable frequency power supply uses the PID algorithm to slowly adjust the output to the set value. The measurement circuit sends the actual high voltage to the variable frequency power supply, fine-tuning the low voltage to achieve accurate high voltage output. According to the positive/reverse wiring setting, the measurement circuit automatically selects the input and switches the range based on the test current. The measurement circuit uses Fourier transform to filter out interference, separates the fundamental wave of the signal, performs vector operations on the standard current and the test current, calculates capacitance from the amplitude, and calculates tgδ from the phase difference. Multiple measurements are repeated, and a middle result is selected after sorting. At the end of the measurement, the measurement circuit sends a voltage reduction command, and the variable frequency power supply slowly reduces the voltage to 0.
Precautions and Others
Precautions
1. This instrument can only be used on equipment that is de-energized; the grounding terminal should be reliably connected to the grounding grid. The instrument should be used in a spacious, safe, and reliable place as much as possible.
2. The equipment under test should be disconnected from the high-voltage leads from the operating state to the maintenance state, cleaned, and after preliminary insulation tests are good, the instrument can be used for testing to prevent damage to the instrument during voltage application due to poor insulation of the equipment under test.
3. Determine the wiring method based on the installation situation of the equipment, and select the corresponding wiring method in the menu options.
4. Correctly select the test voltage level according to different equipment, and select the required voltage in the corresponding menu options.
5. If a special situation endangering safety occurs during the test, the main power can be urgently turned off.
6. Only after turning off the power switch on the panel and clearly disconnecting the 220V test power supply can wiring changes be made or work be completed; when repeating the test on the same test equipment, press reset and then measure again, or choose to repeat after the previous test is completed.
7. To ensure measurement accuracy, especially when the loss of small capacitance test samples is small, it is necessary to ensure that the low-voltage end (or secondary end) of the equipment under test has good insulation and measure in an environment with relatively low humidity.
8. When conducting large capacitance test sample experiments, the grounding of the instrument and the grounding of the test sample should not be at the same grounding point to prevent the back-strike voltage or traveling wave from affecting the safety of the instrument during grounding discharge.
9. The instrument comes with a voltage boosting device; attention should be paid to the insulation distance of the high-voltage lead and personnel safety; 10. The instrument should be reliably grounded; poor grounding may cause machine protection or danger.
10. After the instrument is started, except for special circumstances, it is not allowed to suddenly turn off the power to avoid overvoltage damage to the equipment;
11. Although the special high-voltage wire (HVx) provided with the instrument has been tested and qualified at the factory, it still needs to be kept away from the human body and the low-voltage test line (Cx) during measurement; neither the high-voltage core wire nor the high-voltage shielding wire is allowed to be grounded or in contact with the low-potential part of the test circuit.
The core wire and shielding wire of the CX input line are not allowed to contact the high-voltage part of the test circuit.
12. The instrument should be protected from moisture and severe vibration.
13. When the on-site interference is large and the power frequency cannot obtain definite results, the variable frequency measurement should be used; in other cases, the power frequency measurement should be used.
14. When the measurement command is issued and the measurement result does not appear on the screen for a long time (1 minute), it may be caused by the test sample capacitance being too large or a crash. After restarting, reduce the measurement voltage and measure again.
15. A short circuit in the test sample will prevent measurement, and the instrument will automatically protect itself. When a section extends from the paper outlet above the machine head, press the button once to stop paper feeding. The printing paper is allowed to be pulled outward.
Instrument Structure
Measurement circuit: performs all calculations such as Fourier transform, complex number operations, range switching, and variable frequency power supply control.
Control panel: printer, keyboard, display, and communication relay.
Variable frequency power supply: uses SPWM switching circuit to generate high-power sine wave stabilized output.
Step-up transformer: boosts the output of the variable frequency power supply to the measurement voltage, with a maximum reactive power output of 2KVA/1 minute.
Standard capacitor: internal Cn, measurement reference.
Cn current detection: used to detect the current of the internal standard capacitor, 10μA to 1A. Input resistance <2Ω.
Cx positive wiring current detection: only used for positive wiring measurement, 10μA to 1A. Input resistance <2Ω.
Cx reverse wiring current detection: only used for reverse wiring measurement, 10μA to 1A. Input resistance <2Ω.
Reverse wiring digital isolation communication: uses a precision MPPM digital modulation demodulator to transmit the reverse wiring current signal.
