EP0506035A1
Expired / Lapsed
EP
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Method and device for detecting saturation in current transformers
Assignee: ABB AB
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Filing: 1992-03-26
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Granted: —
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Expires: 2012-03-26
Abstract
Abstract A Method and a detector for detecting saturation in current transformers (1) based on the following criteria: |I(t)| < K1, |d(I(t))/dt| < K2, |I(t-τ)| > K3, I(t) is the low-pass filtered current of the current transformer and K1, K2, K3 and τ are constants of predetermined values. If all three conditions are fulfilled, the current transformer is saturated.
Inventors
- 👤 Mohan Saha Murari
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-08 16:07
CPC Classifications
H; H02; H02H; H02H1/00; H02H1/04; H02H1/046; H02H1/0007
Claims Analysis
Total Claims: 2
Claim 1
Independent Claim
166 words
Method for detecting saturation in current transformers (1) based on continuous determination of the absolute value of both the current (|I(t)|) and the derivative (|d(I(t))/dt|) of the current, characterized in that the delivered current of the current transformer is first low-passed filtered, that thereafter are formed both the absolute value of the current and the absolute value of the derivative of the current, and that current transformer saturation is indicated when the following three conditions are simultaneously met: |I(t)| < K1, |d(I(t))/dt| < K2, |I(t-τ)| > K3, where K1 is a predetermined value corresponding to a few per cent of the rated value of the current in question, K2 is a predetermined value of a few per cent of the maximum value of the derivative of the current at sinusoidal waveform, K3 is a predetermined value corresponding to the rated value of the current, and the time τ is set at a value lower than the time for 1/4 period of the power frequency in question.
Claim 2
Dependent Claim
342 words
Detector for for detecting saturation in current transformers (1), characterized in that the detector comprises - a low-pas filter (2) for filtering off harmonics in the current (I(t)) from the secondary side of the current transformer, - a first absolute value generator (3) for forming |I(t)|, - a differentiating unit (6) for forming the derivative (DI(t)) of the current (I(t)), which differentiating unit (6) is connected to a second absolute value generator (7) for forming |DI(t)|, - a memory circuit (9) for producing I(t-τ) where τ has a value lower than the time for 1/4 period of the power frequency in question, said memory circuit (9) being connected to a third absolute value generator (10) for forming |I(t-τ)|, that said first absolute value generator (3) is connected to a first comparator (4) which compares its input signal with a first predetermined value (K1), corresponding to a few per cent of the rated value of the current, and which comparator generates an output signal if the input signal is smaller than the first predetermined value, that said second absolute value generator (7) is connected to a second comparator (8) which compares its input signal with a second predetermined value (K2), which corresponds to a few per cent of the maximum value of the derivative of the current, and which comparator generates an output signal if the input signal is smaller than the second predetermined value (K2), that said third absolute value generator (10) is connected to a third comparator (11) which compares its input signal with a third predetermined value (K3), which corresponds to to the rated value of the current, and which comparator generates an output signal if the input signal is greater than the second predetermined value (K3), and that the output signals of the three comparators (4,8,11) are connected to one input each of an AND-element (5), which is adapted to deliver an output signal (M) when all three of its inputs simultaneous receive a signal from their associated comparators, said output signal (M) indicating saturation of the current transformer.
References Cited (Backward Citations)
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