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DIRECT CURRENT COMPENSATION – FIELD EXPERIENCE UNDER SERVICE CONDITIONS

Helfried Passath ; Siemens AG Österreich Siemens AG Österreich Transformers Weiz
Gerald Leber ; Siemens AG Österreich Siemens AG Österreich Transformers Weiz
Peter Hamberger ; Siemens AG Österreich Siemens AG Österreich Transformers Weiz
Florian Bachinger ; Siemens AG Österreich Siemens AG Österreich Transformers Weiz

Sažetak

Modern grain oriented core steel used in power transformers has a very high magnetic
conductivity. This advanced material makes the transformer susceptible even for small direct current (DC)
in the power grid. Already minor DC increases the no-load noise and no-load losses of the transformer
considerably. This effect is known as half-cycle saturation. In order to overcome these parasitic DC an
active compensation method called “DC compensation” (DCC) was recently developed by Siemens [1].
The question about the origin of the DC is not fully answered yet. However the following sources
have been already identified: power electronics, renewable power generation (wind, solar), HVDC
transmission lines and DC operated railroad or subway systems. The parasitic direct currents can flow
over the power lines to ground or asymmetrically in the power line phases only.
In this paper field data, a four-month DC load profile, of single-phase core type transformers,
equipped with active DC compensation, are shown. The discussed unit, a bank of three single-phase
autotransformers, is in service mainly exposed to DC flowing from the overhead lines through the
windings to the common neutral. DC magnitude varies from 0.05 A to about 0.2 A DC per phase
throughout the day. From factory tests we know that only 0.2 A DC causes a noise increase of 5.6 dB(A)
compared to the noise level without any DC compensation. This might cause troubles at the substation
when noise has to be below a guaranteed level.
Data analysis of the field data shows that the DC throughout the day follows a clear profile with
its highest level during midnight and lunch time. This might indicate a correlation to the load and / or
switching operations in the grid to adjust to the actual needed load.
However, the DC compensation equipment fully eliminates the direct flux in the core and thus the
DC caused increase in noise.

Ključne riječi

Transformer – Direct current – DC bias – Saturation – Noise – No-load loss – Renewable power generation

Hrčak ID:

199072

URI

https://hrcak.srce.hr/199072

Datum izdavanja:

15.8.2017.

Posjeta: 1.126 *