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Fig.
Test Connections for Checking Pickup and
Operating Time of the Time Overcurrent Unit Using
Current Polarization
POLARITY CHECK
The polarity of the external connections to the
directional unit, when it is potential polarized, may
be checked using load currents. The idea is to
tat" current from one current transformer and
voltage from the same phase. The voltage is
tained by
phase 1 from the primary of the
wye-broken-delta transformer and shorting the
phase-one primary winding. Current is obtained by
shorting the current transformers in phases two
and three and opening their circuits to the relay.
This permits the current transformer in phase one
to supply the operating current.
Connect a phase angle meter to
between the current and voltage supplied to the relay.
It is recommended that a mechanical
tion and an operational test be performed at least
annually and if possible at the same time associated
equipment is
tested.
The interval of
the relative importance of individual protective
equipment, their exposure to unfavorable conditions,
such as extreme heat, moisture or fumes. Dust and
may contaminate the relay when the protective
cover is removed.
Courtesy of NationalSwitchgear.com
Ground Directional
ob-
the angle
read
MAINTENANCE
may vary depending on
Test Connections for Checking Pickup and
Fig.
Operating Tine of the Time Overcurrent Unit Using
Potential Polarization
The relay has maximum torque at 60 degrees fag.
With power flowing in the proper direction for oper-
ation, the relay should
in plus or
angle.
If the unit is current
transformer in the power transformer neutral, such
a check is not easily made. It is sometimes prac-
tical to introduce a single phase current in one
phase of the primary circuits in such a way that
current flows through both the transformer neutral
current transformer and one of the line current
transformers.
If this cannot be done, a careful
wiring check must suffice.
Fig. 15 shows the test connections for checking
the polarity of the directional unit itself.
These relays are adjusted at the factory and it
is advisable not to disturb the adjustments. If, for
any reason, they have been disturbed, the following
points should
observed in restoring them:
be
DISK AND BEARING6
The lower jewel should be turned up until the
disk is centered in the air gaps, after which it
Relay Type IBCG GEH-2032
of the maximum torque
from a current
11
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