Aim of Testing the Insulation Properties (Non destructive Testing)
Q. What non destructive testing of insulating materials ? State briefly the characteristics of these methods.
- Prior to use the insulating materials as the part of the equipment, its quantity is to tested by taking a sample of it so that it shall not create a problem in the operation of equipment once the materials are used for it.
- The tests are mainly carried out to assess the electrical properties of the materials such as
- D.C. resistivity(p)
- Dielectric constant (i.e. permittivity ∈)
- Loss factor over a wide frequency range.
- A properly shaped specimen of insulation is taken for these tests and tests are to be conducted at the desired temperature (or over a range of temperature).
- The findings from such tests help the design engineer for using the proper insulation in the equipments.
Non destructive testing of insulating materials
- All the insulating materials that form a part of the high voltage equipment are tested to ensure their quality in the said ranges of operation.
- These tests are designed in such a way that the insulating material is not damaged or destroyed during these tests and hence these tests are known as non-destructive tests.
Characteristics of such tests (NDT) are
- These tests mainly assess electrical properties of materials such as DC resistivity (p) dielectric constant (ɛ), loss factor etc over a wide frequency range.
- These may be carried for specific temperature or a temperature ranges by keeping test specimen in controlled temperature ovens.
- Variation of different electrical properties over the operating range is obtained from such tests.
- These help design engineers to take into account such variations in design of electrical insulation for any electrical apparatus.