Differential protection method and differential protection device for a transformer

Patent metadata

Field	Value
Publication number	US-10707677-B2
Application number	US-201415517257-A
Country	US
Kind code	B2
Filing date	Oct 10, 2014
Priority date	Oct 10, 2014
Publication date	Jul 7, 2020
Grant date	Jul 7, 2020

Abstract

A differential protection method allows monitoring a three-phase transformer. Current measured values are recorded for each phase on all sides of the transformer, a phase-related formation of difference values is carried out using the current measured values from a reference side and amplitude-adjusted and phase-angle-adjusted current measured values from all other sides. An internal error is detected if a difference value exceeds a threshold value. In order to form the amplitude-adjusted and phase-angle-adjusted current measured values, the current measured values recorded for all phases are initially subjected to an amplitude adjustment and then to a phase angle adjustment. In order to allow the phase angle shift to be freely adjusted, a defined matrix equation with a defined matrix coefficient is used for the phase angle adjustment of the current measured values from the particular other side of the transformer. There is also described a differential protection device.

First claim

The invention claimed is:

1. A differential protection method for monitoring a three-phase transformer for internal faults, the method comprising:
registering measured current values defining a current curve within a respective phase for each phase on all sides of the transformer;
carrying out a phase-related difference-value formation using the registered measured current values from a reference side of the transformer and amplitude-adjusted and phase-angle-adjusted measured current values from all other sides of the transformer while forming respective difference values;
detecting an internal fault in the transformer if at least one of the difference values exceeds a prespecified threshold value;
in order to form the amplitude-adjusted and phase-angle-adjusted measured current values, initially subjecting the measured current values for all phases registered on all other sides of the transformer to an amplitude adjustment with a formation of amplitude-adjusted measured current values using a transformer ratio; and
thereafter subjecting the amplitude-adjusted measured current values to a phase-angle adjustment with a formation of amplitude-adjusted and phase-angle-adjusted measured current values, to compensate for a phase shift caused by the transformer;
using the following equation for the phase-angle adjustment of the measured current values:

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Assignees

• Siemens Ag

Inventors

• Weilbier Joerg

Classifications

• H02H7/055

  for tapped transformers or tap-changing means thereof · CPC title

• H02H7/045 Primary

  Differential protection of transformers · CPC title