0.1Hz Digital Portable 80kV VLF Cable Hipot Tan Delta AC Withstand Voltage Tester

XHDP series ultra low frequency withstand voltage tester
VLF AC Hipot Tan Delta Tester

INTRODUCTION
Ultra low frequency insulation withstand voltage test is actually an alternative method of power frequency withstand voltage test. We know that when the power frequency voltage withstand test is carried out on large generators, cables and other test objects, because their insulation layer presents a large capacitance, a large capacity test transformer or resonant transformer is required. Such huge equipment is not only bulky and expensive, but also inconvenient to use.

In order to solve this contradiction, the power department has adopted reducing the test frequency, thereby reducing the capacity of the test power supply.

Many years of theory and practice at home and abroad have proved that using 0.1Hz ultra-low frequency voltage withstand test instead of power frequency voltage withstand test can not only have the same equivalence, but also greatly reduce the volume and weight of the equipment.

FEATURES

This product adopts digital frequency conversion technology, single-chip microcomputer control, voltage boost, buck, measurement, protection completely automatic. Due to the full electronic, so small size and light weight, the use of large screen color touch display, clear and intuitive, simple operation, display output waveform. The design index conforms to the national standard of "General Technical Conditions of Ultra-low frequency high voltage generator". The main features are as follows:

1. The ultra-low frequency with rated voltage less than or equal to 60kV adopts a single link structure (a booster); The ultra-low frequency of more than 60kV adopts a series structure (two booster in series), which greatly reduces the overall weight and enhances the load capacity, and the two booster can be used separately to achieve a multi-purpose machine.

2. Current and voltage data are sampled directly from the high voltage side, so the data is accurate.

3. Intelligent comprehensive protection function: there is no need to set the current and voltage protection value, the instrument can calculate the overvoltage and overcurrent protection value according to the size of the test capacity and the test voltage value, and can also protect the voltage and current mutation, so it can capture the discharge situation. The protection operation time is less than 20ms.

4. 150kV high voltage line output, safe and reliable.

5. Because of the closed-loop negative feedback control circuit, the output has no capacity rise effect.

TECHNICAL DESCRIPTION

Input power: frequency 50Hz, voltage 220V±5%(or frequency 60Hz, voltage 110V±5%). If the micro generator is used for power supply, the frequency conversion generator should be used, and the ordinary generator can not be used, because the ordinary generator speed is unstable, which will make the boost voltage abnormal and damage the instrument.

MAIN STRUCTURE

1.For the ultra-low frequency with a rated voltage below 60kV(include 60kV), a booster is used, which is called the single-coupled ultra-low frequency, and its structure and components are described in the following figure:

2.For ultra-low frequency with rated voltage above 60kV, two boosters are used in series, which is called series ultra-low frequency, and its structure and components are described in the following figure:

CONNECTION METHOD

1.Below 60kV single-link ultra-low frequency voltage test connection mode is as follows:

2.The connection method of ultra-low frequency voltage withstand test when the two-stage booster is connected in series is as follows:

OPERATION STEPS- FOR AC WITHSTAND VOLTAGE TEST

After connecting the field test system according to the above, the power supply can enter the test.

1. The home page of the touch screen of the control box is connection diagram selection. Select a connection diagram consistent with the actual situation.

2.If the cable under test is less than 100 meters and the instrument cannot output a smooth sine wave voltage, the compensation capacitor can be connected in parallel at the test end.

3. After entering to the parameter setting page, test time, test voltage, can be modified according to test requirements. Click on the data you want to modify and a numeric keypad will pop up to enter the required data. In order to ensure safety, the system limits the input data: test voltage range 0 to the rated value; The test duration is 1 to 99 minutes, and data entry beyond the range is invalid. After the test, this parameter is automatically saved as the default value for the next test.

4. Click withstand voltage test to start the test, the instrument will take two to three cycles to raise the voltage to the set voltage.
In the first two cycles, pre-test the test product, determine whether the test product has low resistance fault, measure the capacitance of the test product, and then determine the appropriate frequency according to the size of the capacitance of the test product for voltage resistance test.
The system provides intelligent protection for the test process: overvoltage, overcurrent, voltage and current sudden change, discharge and other protective actions.

5.After counting the test time, the instrument will automatically stop, or you can directly click the stop button to stop.

The shutdown process will automatically discharge the test object. After shutdown, the data can be printed or saved, and 90 groups can be stored in a cycle. The selected data record can be printed in the historical data query.

The top line of the screen is a reminder of the working status of the instrument, including some instrument fault information. Click the Details button to view all the information, including the working status and fault information of the instrument and the sample. Because of the touch key prompts and help information, users can also follow the prompts.

6.Before removing the cable, unplug the power cord, discharge the test with the discharge rod, and then short-circuit discharge, and then remove the cable operation.

The four main operating interfaces are as follows:

Select Wiring Diagram(The picture above is the wiring diagram of equipment of 60kV and below.)

Set test voltage and test time according to actual test requirements

Click AC Withstand Test to enter the test interface

Test end interface

OPERATION STEPS-FOR VLF DIELECTRIC LOSS TEST

Special note: Only ultra-low frequency testing devices with dielectric loss function can be purchased to measure dielectric loss

1. Why should ultra-low frequency be used for dielectric loss testing of cables
Due to the large capacitance of the insulation layer of the cable, it is required that the dielectric loss instrument have a large testing capacity and a high testing voltage. For example, for 35kV cables, the dielectric loss test voltage should be 1.5 times U0 (i.e. 39KV). The conventional power frequency dielectric loss tester has a small load capacity and a low test voltage (less than 12KV), which cannot meet this testing requirement. Ultra low frequency has strong carrying capacity due to its low operating frequency, making it suitable for conducting dielectric loss tests on cables.

2. Introduction to Dielectric Loss Ultra Low Frequency Series Products
All specifications and products of different voltage levels can be equipped with dielectric loss testing function. Dielectric loss ultra-low frequency is a multifunctional cable tester that can measure the dielectric loss, capacitance, insulation resistance of cables, and also perform AC and DC withstand voltage tests. Due to the installation of the sampling device for electrical parameters related to dielectric loss in the ultra-low frequency booster and control box, the device is small in size, light in weight, simple in connection, and easy to use. It is a good helper for on-site cable testing and determining cable insulation performance.

3. Dielectric loss ultra-low frequency technical indicators

4.Field Wiring Diagram
The on-site wiring method is the same as the withstand voltage test. If you want to eliminate the impact of surface leakage current at the end of the cable on dielectric loss, you can introduce leakage current to the instrument and deduct this impact from the total dielectric loss. The wiring method of introducing leakage current from one end of the cable is called single end shielding method; The wiring method of introducing leakage current from both ends of the cable is called the double end shielding method. The working principle of eliminating the influence of surface leakage current on dielectric loss is shown in section 3.6 below. How to eliminate the influence of cable surface leakage current on dielectric loss. The two on-site wiring diagrams are as follows:
4.1 Single ended shielding method wiring diagram

4.2 Wiring diagram of dual terminal shielding method

Operation steps

1. After connecting the on-site testing system as described above, connect the power supply to enter the test.

2.The homepage of the touch screen of the control box is for selecting the wiring diagram, entering the parameter setting interface, testing time, testing voltage, and modifying according to the testing requirements.

Click on the data to be modified, and a numeric keypad will pop up to input the required data. In order to ensure safety, the system has limited the input data: the test voltage range is 1kV to the rated value; The test time is 1-99 minutes.

3. Continuous dielectric loss test is a continuous measurement of dielectric loss at a set voltage, which can also be used as an AC withstand voltage test. The national standard dielectric loss test is to perform eight data tests on three-phase cables under three point voltages (0.5U0, U0, 1.5U0) according to regulations, and calculate the average value, variation, and stability of dielectric loss, automatically distinguishing the insulation quality of cables according to regulations.

3. After the experiment, this parameter will be automatically saved as the default value for the next experiment.

4.Continuous dielectric loss testing program: The instrument first enters a self check, which is a pre test of the test object and calibration of the instrument itself. The length of the self check time is related to the length of the cable. The longer the cable, the longer the self check time, which can be as long as one to five minutes. It requires patience to wait. After the self inspection is completed, it automatically enters the continuous dielectric loss test, which can simultaneously measure the dielectric loss, capacitance, and insulation resistance values, and update the data once per cycle.

After a few measurement cycles, the data will become very stable and can be read.

The system provides intelligent protection for the testing process: overvoltage, overcurrent, voltage and current sudden changes, discharge, and other protective actions.

5. The shutdown process will automatically discharge the test object. After shutdown, the current data can be printed or saved, and the selected data records can also be printed in the historical data query on the homepage. The top line of the screen is a prompt for the working status of the instrument, which includes some fault information of the instrument. Because there are touch key prompts and help information, users can follow the prompts to operate.

6. Before disassembling the wire, the power cord should be unplugged first, and the test object should be discharged with a discharge rod, followed by a short circuit discharge before disassembling the wire.

7. If the length of the tested cable is less than 100 meters and the instrument cannot output a smooth sine wave voltage, compensation capacitors can be connected in parallel at the test object end. On the parameter setting interface, select "Add Compensation Capacitor", so that the test results will deduct the influence of the compensation capacitor. The compensation capacitor must be the one that comes with this product, as the parameters of this capacitor are preset in the instrument.

The following pictures show the pre-test parameter setting interface, IEEE. test interface, and test result interface. Note: The PD test shown in the picture will only appear on devices that have purchased the PD test function.

PHYSICAL TEST PICTURES

Onsite testing