Application; Description Of Operation - ABB SPAJ 131 C User Manual And Technical Description

Application

Description
of operation
The overcurrent relay SPAJ 131 C is designed
to be used for two-stage phase overcurrent pro-
tection of distribution feeders, large low-voltage
motors, high-voltage motors, medium-sized and
large generators and power transformers. The
relay can be used both as main protection relay
and back-up protection relay.
The relay has two protection stages: a low-set
overcurrent stage I> and a high-set overcurrent
The overcurrent relay SPAJ 131 C is a secondary
relay that is connected to the current transform-
ers of the protected object. The relay can be used
for single-phase, two-phase or three-phase over-
current protection. The overcurrent relay con-
tinuously measures the phase currents of the
object to be protected. On the occurrence of a
fault the overcurrent relay generates an alarm
signal, trips the circuit breaker or starts external
auto-reclose functions, in accordance with the
current application.
When the phase current exceeds the set start
value I> of the low-set stage, the overcurrent
relay starts. When, at definite time operation,
the set operate time t> or, at inverse definite
minimum time (IDMT) operation, the calcu-
lated operate time t>, expires, the relay operates.
In the same way the high-set stage starts once its
set start value I>> is exceeded and, when the set
operate time t>> expires, the relay operates.
I
L1
I
L2
I
L3
Blocking
Fig. 1. Protection functions of the overcurrent relay SPAJ 131 C. The encircled numbers refer to
the ANSI (=American National Standards Institute) number of the concerned protection function.
Three-phase low-set overcurrent stage
with definite time or inverse definite
minimum time operation characteristic
Three-phase high-set overcurrent stage
with instantaneous or definite time
operation characteristic
Blocking of high-set and/or low-set overcurrent
stages by external control signal
Serial communication
stage I>>. The low-set stage operates with defi-
nite-time characteristic or with inverse-time
characteristic, while the high-set stage operates
with definite time characteristic only.
The overcurrent relay is provided with five
output relays, of which four are freely configur-
able for the desired function. Two of the output
relays have heavy-duty contacts capable of di-
rectly controlling a circuit breaker.
The low-set stage of the overcurrent relay can be
given either definite-time or inverse-time char-
acteristic. At inverse time characteristic four
inverse time curve sets with different slopes are
available: Normal inverse, Very inverse, Ex-
tremely inverse and Long-time inverse. These
curve sets comply with the BS 142 and IEC 255
standards.
The start signals from the overcurrent relay are
obtainable as contact functions. The start signal
can be used, for instance, for blocking cooperat-
ing protection relays.
The relay contains one optically isolated logic
input for incoming external control signals,
generally blocking signals.
51
50
Tripping 1
Tripping 2
Signal 1
Start 1
IRF
Serial port
3