Insulator FRP core oil puncture test machine

FRP core oil puncture test machine at a glance

• Purpose: measures the electrical puncture voltage of the fibre reinforced core of a composite insulator.
• Procedure: a short sample of the core is placed in transformer oil and the voltage is raised between the electrodes until the sample punctures; the puncture voltage is recorded.
• Why oil: transformer oil insulates better than air, so the puncture happens through the core and not along its surface.
• Ratings: test voltage up to 100 kV, AC or DC; capacity of the high voltage part 10 kVA; supply 220 V; consumption 2 kW.
• Control: computer controlled, software in Chinese, English or Russian.
• Users: composite insulator manufacturers, core suppliers and testing laboratories.

1. What this machine is used for

The core of a composite insulator is a fibre reinforced plastic rod, the FRP or ECR rod. Its insulating property is an essential part of the quality of the finished insulator, and the way to check it is to stress a sample of the rod until it punctures and to record the voltage at which that happens.

In this test a short piece of the rod is cut and placed in transformer oil, which has a better insulating property than air. The voltage is then applied to both ends and increased until the sample punctures. Because the surrounding oil suppresses any discharge along the surface, the measured value is the puncture strength of the core material itself, not the flashover strength of the sample in air. The machine records the whole procedure and the puncture voltage.

The machine consists of the power frequency high voltage part, the control system, the measuring device, the automatic protection system and the electrodes, which together carry out the test as the test methods and acceptance criteria of the standard require.

2. Standards applied

• IEC 61109 – Composite suspension and tension insulators for overhead lines with a nominal voltage above 1000 V. It requires the insulation property of the core to be verified as part of the quality control of a composite insulator.
• GB/T 19519 – the Chinese national equivalent for composite insulators for a.c. overhead lines, referenced by IEC 61109:2008 in this context.
• IEC 62217 – Polymeric insulators for indoor and outdoor use; used together with IEC 61109 for the material and core test programme.

3. Technical parameters

The machine is delivered with the high voltage part, the control system, the measuring device, the automatic protection system and the electrode set. An independent earth connection is required for the test area.

4. Key functions

• Voltage raised automatically to the puncture point, with the puncture voltage recorded.
• Test carried out in transformer oil so that the result is the puncture strength of the core and not a surface discharge.
• AC or DC output, selected for the requirement of the test.
• Computer control with the test procedure, the voltage and the result shown on screen.
• Automatic protection for overvoltage and overcurrent, and interlocked earthing.
• Test record saved and printed.

5. Typical applications

• Composite insulator manufacturers – verification of the insulation property of the core as required by IEC 61109.
• FRP / ECR rod suppliers – qualification and batch verification of the rod.
• Material and high voltage laboratories – third party verification, and comparison of standard and acid proof core grades.
• Failure investigation – checking whether a field or test failure is related to the insulating property of the core.

6. Frequently asked questions

1. Is this the same test as the puncture test on a complete insulator?

No. This test punctures a sample of the core material in oil and measures the electrical strength of that material. The puncture test on a complete insulator stresses the finished insulating part, including the housing and the interface, and is a different test with a different object.

2. Why is the sample put in oil?

Transformer oil insulates better than air. Immersing the sample suppresses any discharge along its surface, so the voltage rise ends in a puncture through the material, which is the value the test is looking for.

3. Is the test voltage a.c. or d.c.?

Both are possible; the machine supplies up to 100 kV and the output is selected as a.c. or d.c. according to the requirement.

4. Which standard requires this test?

IEC 61109, with GB/T 19519 as its Chinese national equivalent. Both treat the insulation property of the core as an essential check on the quality of a polymer insulator.

5. Is the test destructive?

Yes. The sample is stressed until it punctures, so it is carried out on samples taken from production rather than on units that are shipped.

6. Can the machine be used for the water diffusion test?

No. The water diffusion test boils the core sample in water and then measures the leakage current at a specified voltage without puncturing it, and it is served by a dedicated device.

Related composite insulator test equipment

This machine belongs to the electrical test equipment for insulators range. The resistance of the core to moisture is checked on the water diffusion test device for FRP cores and the housing material on the tracking and erosion test machine. The complete programme for composite insulators is listed in the insulator testing machines catalogue.