Operation; General Testing Procedure; Connection To Cable Under Test; Measuring Distance To Fault - Megger TDR1000/2P Benutzerhandbuch

Operation

General Testing procedure

Ensure the correct test leads are firmly fitted into
the sockets of the instrument.
Switch on the instrument. The TDR1000/2 will
display the start screen for a couple of seconds,
followed by a trace. The instrument will be set to
the range and velocity factor last used. If these
settings are different for the cable under test
(C.U.T) then use the RANGE and VF keys to set the
correct values. Refer also to 'Velocity factor' later
in this text.

Connection to Cable Under Test

Connect the test lead to the cable under test.
Connection may be made to a live system with a
voltage to earth (ground) less than 300V with an
installation (over voltage) category of III or lower.
This means that the instrument may be connected
to any fixed wiring of a building installation, but
not to primary supply circuits such as overhead
cables.
A Fused Lead Set must be used to connect
to energised live systems. Refer to the
accessories section for options.
When selecting 25 cable impedance, an internal
10
50Hz/60Hz filter is automatically switched in.

Measuring distance to fault

Ensure that the whole length of the cable can be
seen on the display, and that the range selected
is correct.
Find key
The Find key searches for the furthest major
change of impedance. This may be a fault or the
end of the cable if this is a short or open circuit.
When found the event is displayed and the cursor
placed on the leading edge. The gain,
and cursor position may need to be adjusted for
accurate measurement. Note that Find does not
adjust the TxNull or Velocity Factor.
To enable 'difficult to see' faults to be identified,
the gain of the instrument can be adjusted. With
the gain at minimum small changes of cable
impedance may be overlooked. By increasing the
gain the fault becomes more obvious.
If no faults are obvious, adjust the gain until any
major reflections appear. Open and short circuits
should easily be identified. Partial faults can be
less obvious.
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