Capacitor bushing incoming material inspection process

What is a capacitance graded bushing?

In a capacitance graded bushing, the main purpose of the test tap component is to provide access to measure the bushing capacitance and power factor. The voltage tap can also be used to measure permanent voltage or to monitor PF or partial discharge online.

What is a test tap in a capacitance graded bushing?

In a capacitance graded bushing, the test tap is a component which main purpose is to provide access to measure the bushing capacitance and power factor. The voltage tap, in addition, can be used for permanent voltage measurement or online monitoring of PF or partial discharge.

Does a bushing have a center conductor?

The bushing’s center conductor is above ground potential and must be electrically insulated from the tank walls, which are at ground potential. The bushing’s main function of allowing the current to pass through the apparatus cannot be achieved without the bushing’s ability to insulate the main conductor from ground.

What are the PF limits for OIP bushings?

Such limits vary depending on the type of bushing and are defined at a specific test voltage and frequency. Table 1 shows the accepted IEEE C57.19.01 and IEC 60137 standard limits for PF values for OIP bushings. Typical values for new bushings range between 0.2% and 0.4%.

Do low voltage bushings need a tap?

Lower-voltage bushings do not require a tap, and the capacitance (C) of a bushing without a voltage or test tap is the capacitance between the high-voltage conductor and the mounting flange (ground). C1 capacitance, the bushing’s main insulation, is measured between the high-voltage conductor and the voltage tap or the test tap.

How do you test a high voltage bushing?

High-voltage bushings are usually equipped with a tap for test measurements. The bushing nameplate should list the tap capacitance and power factor of the C2 insulation, as measured from the tap to the grounded flange. Perform power-factor or dissipation-factor tests on each bushing equipped with a power-factor/capacitance tap.