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All nuts and screws should be tight, particularly on the tap plugs .
The felt gasket on the cover should be securely cemented in place in order to keep
out dust.
Determine the impedance and phase angle seen by the relays.
and phase angle is determined, the tap value at which the relay will just operate can be
calculated.
It is then only necessary to reduce the tap setting of the relay until the
units operate, and see how close the actual tap value found checks with the calculated
value.
The calculated value should take into account the shorter reach of the unit at
low currents.
This effect is shown in Figure
A procedure to check most of the possible open circuits in the AC portion of the
relay is as follows:
(
)
a
Open the potential circuit by removing one of the
plugs.
Place current taps in the
(
)
b
With current greater than two amps flowing in the current coils, the left
contact of the unit should close.
(
)
c
Replace the
unit should close its right contact, while the other unit should have
increased torque closing the left contact.
closed, and which has its right closed, is determined by the direction of the
current in the current circuit, relative to the voltage on the potential
circuit.
In view of the vital role of protective relays in the operation of a power system,
it is important that a periodic test program be fo
periodic checks will vary depending upon environment, type of relay and the user•s
experience with periodic testing.
select the test interval best suited to his individual requirements, it is suggested
that the points listed under
two years.
CONTACT CLEANING
A flexible burnishing tool should be used for cleaning relay contacts.
flexible strip of metal with an etched-roughened surface, which in effect resembles a
superfine file.
The polishing action of this file is so delicate that no scratches are
left on the contacts, yet it cleans off any corrosion thoroughly and rapidly.
flexibility of the tool insures the cleaning of the actual points of contact.
contacts should never be cleaned with knives, files, or abrasive paper or cloth.
GEK-49778
and #2 restraint tap plugs. With
#1
PERIODIC CHEC KS AND ROUTINE MAINTENANCE
Until the user has accumulated en ough experience to
ACCEPTANCE TEST S
14.
ohm taps.
1. 5
120
Which unit has its left contact
11
owed.
be checked at an interval of from one to
15
Once the impedance
and one of the
#1
#2
volts on the relay, one
1
The i nterva
between
This is a
tap
The
R elay
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