TRANSFORMER INRUSH EFFECTS STUDIES DOWNLOAD LINK

DOWNLOAD LINK OF STUDIES ON TRANSFORMER INRUSH EFFECTS
Transformer Inrush Studies Link


Introduction
In a typical UK wind farm a series of radial 33kV collector circuits run from the main switchboard and link together individual wind turbine generator (WTG) transformers. At the design stage it is necessary to determine the maximum number of WTG transformers that can be energised simultaneously from the 33kV system.

One of the factors to be considered is the voltage dip experienced at the point of common coupling (PCC) or interface between the electrical system of the wind farm and the utility company. The UK standard applied is the Electricity Council’s Engineering Recommendation P28, which allows a 3% voltage dip. This article describes wind farm transformer inrush analysis studies the Glasgow based power systems consultants Mott MacDonald have undertaken using PSCAD to demonstrate compliance with P28.

Transformer inrush
When a transformer is energised, it may draw a high magnitude transient current from the supply causing a temporary voltage dip. This current, characterised as being almost entirely unidirectional, rises abruptly to its maximum value in the first half-cycle and then decays until the normal steady-state magnetizing conditions are reached. The magnitude and duration of the inrush current depends upon the following all of which can be represented using a PSCAD model:

the point on the voltage wave at the instant the transformer is energised (i.e. switching angle);
the impedance of the supply circuit;
the value and sign of the residual flux linkage in the core;
the non-linear magnetic saturation characteristic of the core.

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