ABB SRW Instruction Leaflet

Effective: December 1996
Supersedes I.L. 41-252. Dated April 1987
( | ) Denotes Change Since Last Issue
!
CAUTION
It is recommended that the user become
acquainted with the information in this instruc-
tion leaflet before energizing the equipment. Fail-
ure to observe this precaution may result in
damage to the equipment.
1. APPLICATION
The type SRW relay is a single phase directionally
controlled timing relay used to protect ac generators
from motoring. When such a condition occurs and
persists for a predetermined time interval, the gener-
ator may be tripped or an alarm sounded. The SRW
may also be used to sense lagging power factor load
flow in an abnormal direction as shown in
The directional unit has 30 degree maximum sensitiv-
ity characteristics. The timer unit is adjustable from 2
to 21.5 seconds, .2 to 2 seconds or 2 to 63 seconds
depending upon relay style. The range of the current
pickup settings is from 1 mA to 40 mA at the maxi-
mum sensitivity angle.
2. CONSTRUCTION
The SRW relay consists of three printed circuit mod-
ules and a front panel packaged in a FT-11 case. For
detailed information on the flexitest case, refer to I.L.
41-076.
The photograph in
Figure 1
its case.
All possible contingencies which may arise during installation, operation or maintenance, and all details and
variations of this equipment do not purport to be covered by these instructions. If further information is
desired by purchaser regarding this particular installation, operation or maintenance of this equipment, the
local ABB Power T&D Company Inc. representative should be contacted.
Printed in U.S.A.
ABB Power T&D Company Inc.
Power Automation and Protection Division
Coral Springs, FL 33065
Figure 8.
shows the SRW relay in
SRW
Reverse Power Relay
with Adjustable Timer
2.1. Interface Module
The interface module, mounted at the bottom of the
relay, contains a voltage transformer, a current trans-
former, a reed relay and two miniature high power
relays. This module also contains a dc power supply
and its dropping resistors.
(1) DC Power Supply — Three dc input voltages,
48, 125 and 250 volts, can be selected by con-
necting a jumper to a suitable position which is
printed on the PC board's left-hand side. The
relay is shipped with a setting of 125 volts.
(2) Voltage Transformer — This transformer con-
sists of one primary winding and one second-
ary winding. The continuous voltage rating at
primary side is 150% of the rated line voltage
but the relay's accuracy is designed between
30% and 110%. The secondary voltage is fed
to the SRW module as a phase angle refer-
ence.
(3) Current Transformer — this is a two-winding
transformer with a turns ratio of 20 to 400. A
load resistor of 20 ohms is connected across
the secondary winding. The secondary voltage
is linearly proportional to the primary current if
the input current is less than 5 amps. For cur-
rent higher than 5 amps, the secondary volt-
age is clamped to approximately peak-to-peak
voltage of 20 volts in order to void ct satura-
tion.
(4) Trip Relays — Two miniature high power
relays are connected to the trip circuit. Each
relay is equipped with a normally open contact
Instruction Leaflet
41-252A