| 1. | Due to the use of frequency conversion technology, accurate measurement can be ensured under strong electric field interference. |
| 2. | The instrument adopts 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 the loss test of insulating oil. |
| 4. | This instrument can measure high-voltage electrical equipment that is ungrounded or directly grounded using positive and reverse wiring methods. It can also measure the tgδ of capacitive voltage transformers and the capacitances 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, high voltages of different levels from 0.5kV to 10kV are output, making operation simple and safe. |
Test Instrument 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 dragging 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℃－50℃, relative humidity <80%
9. Dimensions: 460(L)×335(W)×340(H)
10. Weight: 30 kg
Working Principle:
After the off-frequency dielectric loss tester starts measurement, the high voltage set value is sent to the variable frequency power supply. The variable frequency power supply uses a PID algorithm to slowly adjust the output to the set value. The measurement circuit sends the actual high voltage back to the variable frequency power supply, which fine-tunes 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 object current, calculates the capacitance from the amplitude, and calculates tgδ from the phase difference. Multiple measurements are repeated, and a middle result is selected after sorting. After the measurement is completed, 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 and switched from the operating state to the maintenance state, and after cleaning and preliminary insulation tests are satisfactory, 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. In case of special situations that endanger safety during the test, the main power can be turned off urgently.
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 tests on the same test equipment, you can press reset and 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 objects 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 object experiments, the grounding of the instrument and the grounding of the test object 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, and 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 dedicated high-voltage wire (HVx) provided with the instrument has been tested and qualified at the factory, it should still 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 shield wire is allowed to be grounded or connected to the low-potential part of the test circuit.
The core wire and shield 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 off-frequency measurement should be used; in other cases, the power frequency measurement should be used.
14. If after issuing a measurement command, the measurement result does not appear on the screen for a long time (1 minute), it may be due to the test object capacitance being too large or a crash. Restart the machine and reduce the measurement voltage before measuring again.
15. A short circuit in the test object will prevent measurement, and the instrument will automatically protect itself. When a section of paper extends from the paper outlet above the machine head, press the button to stop paper feeding. The printing paper is allowed to be pulled out.
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 regulated 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～1A. Input resistance <2Ω.
Cx positive wiring current detection: only used for positive wiring measurement, 10μA～1A. Input resistance <2Ω.
Cx reverse wiring current detection: only used for reverse wiring measurement, 10μA～1A. Input resistance <2Ω.
Reverse wiring digital isolation communication: uses precision MPPM digital modem to transmit the reverse wiring current signal.
