GE GEK-45404F - Manual (Page 15)

GEK-45404
15
Time Setting
The time of operation of the overvoltage relay is determined primarily by the setting of the time dial.
Further adjustment is obtained by moving the permanent magnet along its supporting shelf; moving
the magnet in toward the back of the relay decreases the time, while moving it out increases the time.
Fig. 11 shows the time-voltage characteristics of the IAV51D, IAV52D, IAV51K and IAV52K for
the four tap settings for the Number 1, 5, and 10 time- dial positions. The time-voltage characteristic
of the 1AV52C, which has no taps, is the same as for the "A" tap in the D & K relays.
To make time settings, set the time dial to the number required (to give the desired characteristic) by
turning it until the number lines up with the notch in the adjacent frame. The time indicated by the
curves is the time required to close the relay contacts when the voltage is suddenly increased from a
value below pickup to the value on the curve (expressed in multiples of tap setting). The time
obtained should be the value on the curve ± 15%.
PERIODIC CHECKS AND ROUTINE MAINTENANCE
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 followed. It is recognized that the interval between periodic checks will
vary depending upon environment, type of relay and the user's experience with periodic testing. Until
the user has accumulated enough experience to select the test interval best suited to his individual
requirements, it is suggested that the points listed under INSTALLATION PROCEDURE be
checked every six months.
* Revised since last issue
MAINTENANCE
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 be observed in restoring them.
DISK AND BEARINGS
The lower jewel may be tested for cracks by exploring its surface with the point of a fine needle. If it
is necessary to replace the jewel, the new jewel should be turned up until the disk is centered in the
air gap, after which it should be locked in position by the set screw provided for the purpose.