ABB CWC Instruction Leaflet

Effective: October 1975
Supersedes I.L. 41-242.4E, dated October 1973
Denotes Change Since Previous Issue
*
!
Before putting relays into service, remove all
blocking which may have been inserted for the
purpose of securing the parts during shipment,
make sure that all moving parts operate freely,
inspect the contacts to see that they are clean
and close properly, and operate the relay to
check the setting and electrical connections.
1.0 APPLICATION
The type CWC and CWP relays are induction disc
type relays used for directional ground fault protec-
tion on grounded neutral power systems. The type
CWC relay is polarized by current from a suitably
grounded power transformer bank neutral. Therefore,
*
its application does not require voltage transformers.
The type CWP relay is voltage polarized by residual
voltage obtained across the open corner of the delta
winding of a grounded wye-delta voltage transformer.
At stations where the power transformer bank natural
is grounded, the residual voltage will be small gener-
ally, and the type CWC relay is recommended. At
ungrounded stations, or at ground stations where the
power transformer bank neutral is not available, the
type CWP relay is applicable.
2.0 CONSTRUCTION
The type CWC and CWP relays consists of an oper-
ating unit, an indicating contactor switch, and optional
indicating instantaneous trip unit. In addition to the
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 Automation Inc.
Substation Automation and Protection Division
Coral Springs, FL 33065
CAUTION
Type CWC and CWP
Directional Ground Relays
above components, the type CWP relay has a phase
shifter network. The principal component parts of the
relay and their locations are shown in Fig. 1-8.
2.1 OPERATING UNIT
This unit is an induction disc unit with an electromag-
net that has poles above and below the disc as
shown in Fig.2 and 4. The upper pole of both the
CWC and CWP relays are tapped. In addition, the
lower pole is tapped on the type CWC relay
The electromagnets are connected to the protested
apparatus in a manner so that out-of-phase fluxes are
produced by the flow of currents in both the upper
and lower pole circuits. The out-of-phase fluxes
cause either a contact opening or a contact closing
torque depending upon the relative direction of cur-
rent flow in the upper and lower pole circuits.
2.2 PHASE SHIFTER NETWORK
The phase shifter network of the type CWP relay con-
sists of a capacitor and resistor connected in series
with the lower pole circuit.
2.3 INDICATING CONTACTOR SWITCH UNIT
(ICS)
The d-c indicating contactor switch is a small clapper
type device. A magnetic armature, to which leaf-
spring mounted contacts are attached, is attracted to
the magnetic core upon energization of the switch.
when the switch closes, the moving contacts bridge
two stationary contacts, completing the trip circuit.
Also during this operation two fingers on the armature
deflect a spring located on the front of the switch,
Instruction Leaflet
41-242.2F
.