Megger PFL22M1500 Series, Руководство пользователя

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MTDR USER GUIDE
AVTMPFL22M Rev 1 April 2011
37
Overview of Methods available on the PFL22M1500
TDR / Pulse Reflection
Reminder : TDR or Pulse Echo is a low voltage method of fault prelocation
suitable for locating short and open circuits and other faults bellow about
300Ohm. It is not suitable for high impedance or flashing faults, where HV
method should be used.
Arc Reflection
Reminder : Arc Reflection is the most widely HV method of fault Prelocation
used. It is suitable for high resistance, flashing and other faults that can be
ignited by a surge generator. A reference trace is taken without the arc, then a
real-time trace is taken during the arc and recorded and compared to the
reference trace. The point of divergence is the fault position.
Arc Reflection Plus
Reminder : As Arc Reflection but with the added advantage of being able to
view multiple traces, all of which have been captured during the period of the
arc. This removes the need to adjust the triggering time, as all stages of the arc
can be interrogated.
Differential Arc Reflection (DART)
Reminder: In Differential Arc Reflection mode unwanted and confusing
reflection are removed leaving a clean trace with only the fault position being
displayed by a positive pulse. This method is especially suited in locating high-
resistance faults in complex cable systems”.
Impulse Current (ICE or Current Impulse)
Reminder : Impulse current whilst being suitable for long or wet cables, it is by
far the most difficult requiring the most interpretation. The fault is ignited and
the resultant transients are recorded on a transient recorder. The trace displays
negative impulse both at the point of fault (low impedance) and also where the
surge generator is connected to the cable. Do not use the first displayed impulse
as this includes the “ionization delay” i.e. the time needed for the fault to
flashover. The distance between the negative going impulses is the distance to
fault. For added accuracy try using more than one measurement and different
voltages!