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MiCOM P632
Monitoring Condition
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MiCOM P632
Monitoring Condition
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If CTS is ready, it will monitor the positive- and negative-sequence currents from both transformer ends (a, b).
A CT fault is detected when the following conditions are simultaneously present:
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The positive-sequence current exceeds the set threshold Ipos> in both winding ends. This means that CTS can operate only if a minimum load current is present in the protected object. |
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The negative- to positive-sequence current ratio exceeds a high set threshold value Ineg/Ipos>> in a single winding end. |
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In the other end, the negative- to positive-sequence current ratio is smaller than the low set threshold value Ineg/Ipos>, or no significant current is present (i.e. the positive-sequence current is lower than the Ipos> threshold). |
In such a case, there is a fault in the secondary circuit of the CT at the transformer end where a high negative-sequence current is present.
Because this function uses negative-sequence currents, it can only detect unbalanced CT faults. In practice, this does not present a problem as the occurrence of a three-pole CT fault is very unlikely.
N represents the number of transformer ends, that is N = 2 (a, b).
