Protective Elements
Besides that, the negative-sequence overcurrent element (
51Q
) uses the same setting parameters as the phase
overcurrent elements, like trip and reset characteristics from both IEC/ANSI standards, time multiplier, etc.
The negative-sequence overcurrent element (
51Q
) can be used by line, generator, transformer and motor
protection to protect the system from unbalanced faults. Because the
51Q
element operates on the negative-
sequence current component which is normally absent during load conditions, the
51Q
can, therefore, be set
more sensitive than the phase overcurrent elements. On the other hand, coordination of negative-sequence
overcurrent elements in a radial system does not mean automatically very long fault clearing time for the furthest
upstream protection devices, because the tripping time of concerned negative-sequence overcurrent element
needs only be coordinate with the next downstream device with the negative-sequence overcurrent element.
This makes the
51Q
in many cases as an advantageous protection concept in addition to the phase overcurrent
elements.
If you are using inrush blockings, the tripping delay of the current
protection functions must be at least 30 ms or more in order to prevent
faulty trippings.
All elements are identically structured.
At the moment of breaker closure, negative-sequence current might be the
result of transients.
EN MRM4 01/11
Page 311
Содержание MRM4
Страница 1: ...MRM4 HighPROTEC Motor Protection Device Manual DOK HB MRM4E...
Страница 3: ...Order Code EN MRM4 01 11 Page 3...
Страница 18: ...Important Definitions Page 18 EN MRM4 01 11 41 SG Prot ON 42 SG ON Cmd SG Prot ON SG ON Cmd...
Страница 115: ...Navigation Operation Navigation Operation EN MRM4 01 11 Page 115 1 2 3 5 7 6 8 10 9...
Страница 162: ...Recorder Name Description I 2 TripCmd Signal Trip Command Page 162 EN MRM4 01 11...