Introduction; Application - GE SPA11A Instructions Manual

The Type SPA static pilot-wire-monitoring relays are designed for use in conjunction
with an SPD pilot-wire system to provide detection of open, shorted, reversed or grounded
pilot wires. The relays are powered by a dual-rated, self-contained, isolated DC-to-DC
power supply, to reduce the possibility of battery grounds interfering with operation of
the pilot-wire scheme. Models are available with 48/110-125 volt DC ratings.
The Type SPA 11A and SPA 12A relays provide the basic pilot-wire-monitoring
functions. The SPA 11A is the sending-end relay and operates in conjunction with a Type
SPA 12A receiving-end relay at the remote terminal (or terminals) of two (or three)
terminal lines. These relays will close contacts and operate a light-emitting diode (LED)
when an abnormal pilot-wire condition is detected. The Type SPA 11 B and SPA 12B relays
include provisions for the transmission and reception of direct transfer-trip signals in
either direction, as well as the basic pilot-wire-monitoring functions.
The SPA monitoring scheme uses a low-level DC signal in order to avoid interfering
with the primary AC pilot wire signal (SPD relays).
monitoring signal is separated from the AC signal by low-pass filters. SPA models are
available for use with 50 hertz and 60 hertz SPD relays.
The Types SPA11A, SPA11B, SPA12A and SPA12B are each packaged in the S2
drawout case, the outline and panel drilling of which is shown in Figure 11.
The Type SPA static relays are intended for application as pilot-wire-monitoring
relays and/or transfer-trip relays. As noted above, they are designed specifically for use
with the SPD pilot-wire relaying
When only the monitoring function is desired, the Type SPA 11A is required at one
end of the pilot circuit, designated as the sending end; and the Type SPA 12A is required at
the remote receiving end, or at both remote ends in the case of a three-terminal line. The
SPA 11A relay at the sending end circulates a low-level DC current around the pilot loop,
which holds the contacts of the undercurrent (UC) functions in both the sending-end and
These instructions do not purport to cover all details or variations in equipment nor provide for every possible
contingency to be met in connection with installation, operation or maintenance. Should further information be desired
or should particular problems arise which are not covered sufficiently for the purchaser's purposes, the matter should be
referred to the General Electric Company.
To the extent required the products described herein meet applicable ANSI, IEEE and NEMA standards; but
no such assurance is given with respect to local codes and ordinances because they vary greatly.
GEK-65512
STATIC PILOT WIRE MONITORING RELAY
TYPES:
SPA11A
SPA11B
SPA12A
SPA12B

INTRODUCTION

APPLICATION

system.
Within the SPA relays, the DC
3