19
Connect together all the output relay terminals and measure the insulation resistance
between these terminals and all other terminals connected together to earth.
A minimum value of 2. 5 to 3 meg ohms can be considered as satisfactory value.
5.2. Secondary injection
Select the relay configuration and settings for the application. Note that the MIT relay can
be connected either as 1A or 5A-rated device. The user should check this before
commencing secondary test. Please refer Sec. 2.1. in installation
5.2.1. P
ICK UP AND
R
ESET
The test checks accuracy of the current settings for the relay earth fault characteristics.
Apply single-phase current into the current inputs. Slowly increase the current until the
starter LED (yellow) operates and record the pick up current in Table 1. Reduce the
current until the LED goes off and record this as the reset level. Repeat this test for low set
also.
Check that all the pick up current levels are measured within 104%
±
4% of the applied
setting. Check that the reset levels are
≥
94% of the setting.
POLE
PICK-UP
SETTING
MEASURED
PICK-UP
PICK-UP
ERROR
MEASURED
RESET
RESET
ERROR
E/F
LOW SET
TABLE 1
5.2.2. IDMTL / DTL C
HARACTERISTICS
This test checks the accuracy of the main time delay characteristics (IDMTL / DTL).
Select the relay current setting characteristics and time multiplier settings as required and
then inject a level of current which is a multiple of the relay setting.
A time interval meter should be connected to the correct output contact terminals. The
timer should be started by the source “ON" switch and stopped by the relay trip contacts.
Lowset should be selected. A secondary injection timing test circuit is illustrated in Fig. 6.
The secondary injection test equipment should be made 'OFF', once the relay contact is
closed.
