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If the pilot wire is to be used only for the transfer trip function and no pilot-wire
differential relays are connected to the pilot wire, the operating time will be as follows:
Short Pilot Wire
Long Pilot Wire
The transfer-trip operating time is virtually independent of station battery voltage for
two reasons: 1) the
relay; and 2) the operating time of the TTA units varies only slightly with battery voltage, as
shown in Fig. 12.
LOW PASS FILTER
The current circulating through the pilot wire is monitored through a low-pass filter
in each of the SPA relays. The filter serves two purposes: 1) it screens out the AC signals
transmitted over the pilot wire by the SPD relays; and 2) it screens out any AC disturbances
or "noise" on the pilot wire. Relay models are available for use on 50 hertz systems and 60
hertz systems. The filters are slightly different, to ensure adequate attenuation at the
system frequency.
BURD ENS
The table below indicates the burdens of the SPA relays on the DC station supply
under normal operating conditions.
SPA11A
SPA11B
SPA12A
SPA 12B
The SPA relays were designed and are factory tested such that calibration by the user
is unnecessary. There are no adjustments to be made.
The power supplies within the relay must be set by the user to correspond with the DC
input voltage. This entails the positioning of two adjacent selectors on the printed-circuit
board that contains the power supply. The positions are clearly labeled on the printed
circuit board. The relays that include the transfer trip feature {SPA 11 B and 12B) contain an
additional voltage link to be set. It is located above the target seal-in unit on the mounting
plate.
GEK-65512
TT
units are energized from the regulated 12 volt power supply in the
v
48 V
110
60 ma
25 ma
60 ma
25 rna
60 ma
25 ma
25 rna
60 ma
TI
Remote
approximately 2 cycles
approximately 3 cycles
TABLE VI
DC BURDENS
v
125
48 V
30 ma
30 ma
150 rna
30 ma
30 ma
150 rna
SETTINGS
9
WITH TTA ENERGIZED
v
110
80 ma
80 ma
v
125
90 ma
90 ma
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