Current Transformers For Relay Protection - ABB SafeRing Installation And Operating Instructions Manual

SafeRing / SafePlus
SF 6 insulated ring main unit and compact switchgear
Installation and operating instructions
NHP 304712
The cable shielding is led back
through the centre hole and earthed.
12
NOPOWSR 5976 GB
4.3 CURRENT TRANSFORMERS FOR
RELAY PROTECTION
Installing current transformers. The cable shielding is led back
through the centre hole and earthed.
A protection relay is installed in each vacuum circuit breaker
module. The cables from the protection relay to the current
transformers are placed in the cable compartment, ready for
connection to the three current transformers supplied.
Before installation:
Check that the three current transformers have been
l
delivered and that they are all of the same type.
Check that the current transformers are of the correct type,
l
with the correctly rated transformer ratio, for the
distribution transformer's rated current and for the
adjustment range on the protection relay (see protection
relay manual).
Each current transformer must be mounted onto its high voltage
cable before the cable termination is fitted.
The earth shield on the cable must be led back through the
centre hole in the current transformer (see figure on left) and
earthed on the earthing bar in the cable compartment. A
mounting plate for the current transformers is fitted in the cable
compartment.
After the current transformers have been installed in the unit,
the cables from the protection relay are connected. Consult the
manual supplied with the protection relay for a description of the
connections.
SafeRing with vacuum circuit breakers are prepared for three
different types of protection relays: SACE PR521, SEG WI1-3
and MPRB 99-1.0-GF. All three types are designed so that
there is no need for external auxiliary voltage for correct
functioning.
Separate manuals have been prepared for each of these
protection relay, with examples of adjustments.
SACE PR 521
This relay offers advanced protection with facilities for constant-
time, normal inverse, very inverse and extremely inverse
characteristics as well as simple earth fault protection in
accordance with IEC 60255-3.
MPRB 99-1.0-GF and SEG WI1-3
These are simpler type of inverse-time protection relays, with
fixed settings specially developed for distribution
transformers.The MPRB 99-1.0-GF also have a earthfault
protection module.
It is essential for correct functioning that the current transfor-
mers are properly connected and that the protection relay is
properly adjusted.
SafePlus can be delivered with advanced protection relays. As
option SPAJ140 can be delivered and also other ABB relays
like REJ and REF54 _ can be fitted. This will require additional
low voltage compartment.
See separate documentation for these relays.
ABB / PTMV