Step Voltage Testing (Sv); Factory Settings; Custom Timed Pi Test; Custom Timed Dd Test - Megger BM25 Guia Del Usuario

OPERATION

Step Voltage Testing (SV)

This test is based on the principle that an ideal insulator will produce
identical resistance readings at all voltages while an insulator which is
being over stressed will show lower values at higher voltages. Operating at
either 2,5 kV or 5 kV , the voltage steps up one fifth every minute for 5
minutes, and successive measurements are taken.
1. Using the L M Range keys move the right hand cursor to 'SV'.
2. Accept the default test time of 5 minutes.
3. Accept the default voltage of 2500 V , or using the L M Selector
keys move the left hand cursor to the 5000 V position.
4. Start the test by pressing the red test button for at least one second.
5. On completion, each of the 5 separate results are sequentially
displayed followed by the capacitance value, where available. This
sequential display repeats until a key is pressed or Auto switch-off
operates. For more details of final display information see
Appendix 1.

Factory settings

The following table shows these test times as they are set on a new
instrument, for each of the Test modes. Note that the T1 and the T2 test
times set for the PI test are used to calculate a PI result when carrying out
a DD test.
Test Mode T1
-
SV
1 min
PI
DD
Same as PI
-
BURN - IR
12
T2 T3
-
5 min (fixed)
10 min 10 min
Same as PI 30 min
-
30 min

Custom timed PI test

When new, the BM25 is set up with PI ratio is calculated on the time
settings of 1 minute (T1) and the 10 minute (T2) values. Time setting T3
is also set at 10 minutes. These settings can be adjusted from 15 seconds
to 90 minutes. This original setup produces one PI result, based on the
ratio of T1 and T2. T3 is the total test time (initially 10 minutes for the
test time). By adjusting T3, two separate PI ratio values can be calculated.
The first PI ratio is based upon the measurements of the T1 and the T2
values. The second result is calculated on the time settings of T2 and T3.
Note that if T2 is equal to T3, only one result will be calculated.

Custom timed DD test

The DD test can be customised in the same way as the PI test.
Initially T1 = 1 minute, T2 = 10 minutes, T3 = 30 minutes. This gives a
PI ratio based on T2 / T1, in addition to the DD value.

Setting Custom Test Time values

1. Using the right hand L M Range keys, select the desired test mode.
2. Using the left hand L M Selector keys, select
3. Adjust time T3 using the right hand L M range keys. On
completion, press the left hand M selector key. Time T2 is
displayed as - - 2.
4. Adjust T2 using the right hand L M range keys. On completion,
press the left hand M selector key. Time T1 is displayed as - - 1.
Note:-
These times can be adjusted in any order, but T1 must be
I
shortest, and T3 must be longest.
The values set for T1 and T2 will apply to both PI and
I
DD test.
.