DETAILED OPERATION - Section 4
MTS-3000 OPERATION AND REFERENCE MANUAL 4-1
CU M004 01A
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DETAILED OPERATION
4.1
FAULT STATES
The MTS operates in one of three unique fault states: Prefault, Fault and Postfault, as indicated by the
FAULT and TRIP (POSTFAULT) LEDs. A flashing LED indicates that the AC outputs are enabled.
4.1.1 Prefault State
Prefault state is used to simulate power system conditions prior to the occurance of a fault. Under normal
conditions, balanced three-phase voltage and current occur during the prefault period. Many modern
protective relays monitor and use these prefault conditions to determine the type and location of fault.
When testing certain aspects of these types of protective devices, it isn’t sufficient to simply switch from a
no-AC condition to a fault condition. Other types of testing require that no AC be present during the
prefault state. Pressing the PREFAULT button while the ENABLE LED is lit enables (prefault LED on) or
disables (prefault LED off) the AC outputs during prefault.
4.1.2 Fault State
This is used to simulate power system conditions during the fault. Typically one or more phases of the
voltage will decrease while the current increases, and the phase angle between the voltage and current will
change during the fault period.
4.1.3 Postfault State
Postfault state is used to simulate power system conditions after the faulted section of the power system
has been isolated from the remainder of the power system. The MTS sets all AC outputs to zero during the
postfault period.
4.2
CHARACTERISTICS OF FAULT STATES
The MTS-3000 can output different voltage and current levels, phase and frequency in the prefault and fault
states.
FAULT LED
TRIP LED
Fault state
OFF
OFF
PREFAULT
ON or FLASHING
OFF
FAULT
OFF
ON or FLASHING
POSTFAULT
PREFAULT
FAULT
POSTFAULT
AC outputs at prefault settings
(or off if prefault disabled)
AC outputs at fault settings
AC outputs disabled
Timer=0.0sec
Timer running
Timer reading frozen
AUX contacts de-energized*
AUX contacts energized*
AUX contacts energized*