BS IEC/IEEE 65700-19-03:2014 pdf download – Bushings for DC application.
3.1.2 bushing for pure DC application DC bushing subject to a DC voltage with only a small AC voltage ripple, such as applied on the high voltage side of a DC converter valve 3.1 .3 bushing for combined voltage application DC bushing subject to a large AC voltage superimposed on a DC bias voltage, such as a bushing applied to the valve winding side of a converter transformer 3.1.4 wall bushing roof bushing bushing intended to be mounted on the wall (roof) of a building such as a converter valve hall 3.1.5 tilted bushing bushing intended to be mounted at an angle of 20° to 70° from the vertical 3.1.6 vertical bushing bushing intended to be mounted vertically or at an angle not exceeding 20° from the vertical 3.1.7 horizontal bushing bushing intended to be mounted horizontally or at an angle 70° to 90° from the vertical 3.1.8 draw-lead bushing bushing that will allow use of a draw-lead conductor 3.1.9 draw-lead conductor cable or solid conductor that has one end connected to the transformer or reactor winding and the other end drawn through the central tube of the bushing and connected to the top of the bushing 3.1.1 0 major insulation insulation material providing the dielectric, which is necessary to maintain proper isolation between the energised conductor and ground potential, consisting of internal insulation and the insulation envelope(s) 3.1.1 1 internal insulation Insulating material provided in a radial direction around the energised conductor in order to insulate it from the ground potential 3.1.1 2 charging current capacitive current current resulting from charge absorbed by the capacitor formed by the capacitance of the bushing
3.1.14 insulation power factor ratio of the power dissipated in the insulation, in watts, to the product of the effective voltage and current in volt-amperes, when tested under a sinusoidal voltage and prescribed conditions Note 1 to entry: The insulation power factor is equal to the cosine of the phase angle between the voltage and the resulting current when both the voltage and current are sinusoidal. 3.1.15 partial discharge discharge that does not completely bridge the insulation between electrodes Note 1 to entry: The term corona is preferably reserved for partial discharge in air around a conductor, but not within the bushing assembly. 3.1.16 corona external partial discharge due to ionisation of the air surrounding a conductor caused by a voltage gradient exceeding a critical value 3.1.17 radio-interference voltage RIV high-frequency voltage generated as a result of partial discharge or corona, which may be propagated by conduction, induction, radiation or a combined effect of all three 3.1.18 polarity polarity of the DC voltage with respect to ground, for example positive or negative 3.1.19 polarity reversal change of voltage polarity from positive to negative or from negative to positive polarity 3.1.20 insulating barriers set of barriers which form part of the insulation structure of the converter transformer or smoothing reactor at the oil end of the DC bushing Note 1 to entry: Usually supplied for DC systems of nominal voltage above 1 50 kV.
4 Ratings 4.1 Rated voltages 4.1.1 Rated continuous DC voltage The rated continuous DC voltage is the maximum continuous DC voltage assigned to the bushing by the manufacturer for specified operating conditions. 4.1.2 Rated peak voltage The rated peak voltage is the maximum value of the combination of DC voltage plus peak AC voltage that the bushing is required to withstand under the specified operating conditions. 4.2 Insulation levels According to IEC 60071 -5 the insulation levels for bushings used in DC applications do not generally follow the standard values of insulation level given in IEC 60071 -1 . The purchaser shall specify the insulation levels. The methods of calculation for test voltages are given in the relevant clauses of this standard. 4.3 Rated currents The definition of rated current depends on the bushing application. If the bushing is one for pure DC application, the ratings are defined in 4.3.1 . If the bushing is one for combined voltage application, the ratings are defined in 4.3.2.