1MAC050144-MB C
Section 6
Supervision functions
615 series ANSI
449
Technical Manual
Figure 240:
Functional module diagram
6.4.4.1
No-load detection
No-load detection module detects the loading condition. If all the three-phase currents of
any two sets of current transformer are zero, the protected equipment is considered to be
in the no-load condition and the function is internally blocked by activating the
INT_BLKD output.
To avoid any false operation, the function is also internally blocked if any two-phase
currents of any set of current transformers are below Min alarm current. This activates
INT_BLKD. The value of the Min alarm current setting depends on the type of equipment
to be protected. For example, in case of transformer protection, Min alarm current depends
on the no-load current rating. Typically, it can be set equal to the transformer no-load
current rating.
6.4.4.2
CT failure detection
This module detects the CT secondary failure in any sets of current transformers. The
module continuously scans the value of all the three-phase currents in all groups of current
transformers to detect any sudden drop in the current value to zero. The detection of a zero
current should not be the only criterion for considering a fault in the current transformer
secondary. Two other criteria are evaluated to confirm the CT failure:
• A zero current due to the CT failure does not result in a negative-sequence current on
healthy CT sets.
On the detection of a zero current in any phase on either group of CT, the
negative-sequence current I2 is further evaluated. For a genuine CT secondary
failure, the magnitude of I2 changes only on the side where zero current has been
Содержание 615 Series ANSI
Страница 1: ...Relion Protection and Control 615 series ANSI Technical Manual ...
Страница 2: ......
Страница 29: ...1MAC050144 MB C Section 615 series ANSI 22 Technical Manual ...
Страница 389: ...Section 4 1MAC050144 MB C Protection functions 382 615 series ANSI Technical Manual ...
Страница 485: ...Section 6 1MAC050144 MB C Supervision functions 478 615 series ANSI Technical Manual ...
Страница 635: ...Section 10 1MAC050144 MB C Other functions 628 615 series ANSI Technical Manual ...
Страница 707: ...Section 15 1MAC050144 MB C Applicable standards and regulations 700 615 series ANSI Technical Manual ...
Страница 711: ...Section 16 1MAC050144 MB C Glossary 704 615 series ANSI Technical Manual ...
Страница 712: ......