ISA T 2000 - Page 19

DOC. MIE11110 Rev. 5
Page
19
of
110
600 V input. The choice is performed considering the test current
IP and the VA rating. Given:
. KCT = CT ratio;
. IP = primary test current;
. VA = VA rating,
compute:
IS = IP / KCT
VS = VA / IS
If VS < 10 V, connect to the 10 V input, that has a better
resolution; else, connect to the 600 V input.
Now, input in the screen:
. The primary and secondary current;
. The secondary current metering method: if the current clamp is
enabled, the clamp’s ratio (1000 to 1 for our option);
. The secondary voltage measurement input.
BEFORE STARTING THE TEST, VERIFY THAT THE SECONDARY
CIRCUIT IS CLOSED: THE CT GENERATES HIGH VOLTAGE IF
THE PRIMARY CURRENT IS INJECTED AND THE SECONDARY IS
OPEN!
Press test start button (56), and adjust the primary current to the
desired value by the adjustment knob (6). There are two tabs to
select the measurement of ratio and polarity or burden. With the
selection RATIO, the screen shows:
. The primary current;
. The secondary current;
. The transformer’s ratio;
. The ratio percentage error with respect to the nominal;
. The polarity, as OK or KO. You will notice that the % error does
not change very much as a function of the test current.
Now select the BURDEN tap: the following screen is displayed.