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11 MII FAMILY FAQ (FREQUENTLY ASKED QUESTIONS)
11.1 MIFII FAQ
Q12
My MIFII unit has tripped clearing a system fault, and I would like to analyze oscillography, should I use
special software?
11
A12 EnerVista MII SETUP software allows saving oscillography in a COMTRADE format file (IEEE C37.111 / IEC 60255-
24: Common format for transient data exchange for power systems). As the COMTRADE format chosen is ASCII, these
files can be viewed in any application accepting ASCII format ("Microsoft Excel"), as well as specific applications for
viewing oscillography records, as GE Multilin's GE OSC software.
Q13 My MIFII unit has the display off but the Ready LED is ON; does that mean the relay needs to be repaired?
A13 No, it doesn't. MII relays automatically turn off the display if in 15 minutes no key has been pressed. By pressing any
key the display turns on again.
Q14 I want to pint/view all the relay settings in one window, how can I do it?
A14 In ENERVISTA MII Setup it is possible to see all the settings in a single window. After the communication with the
relay, from the FILE menu of the program you can PRINT or PREVIEW the settings.
Q15 Do harmonics influence the MIFII measure?
A15 No, they don't. MIFII uses a complete cycle recursive DFT (Discrete Fourier Transformation) in order to obtain the
resulting measure phasor. The Fourier transformation consists of decomposing a signal into a series of sinusoidal signals
with frequencies that are multiples of the fundamental frequency. Once these signals have been obtained, harmonics are
extracted to get the phasor value corresponding to the fundamental frequency; therefore, it acts as a digital harmonic filter
and all the relay protection elements work only with the fundamental component of each signal.
GEK-106237P
MIFII Digital Feeder Relay
11-3
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