GRZ100
8
Overvoltage Inverse Time Curves
0.100
1.000
10.000
100.000
1000.000
1
1.5
2
2.5
3
Applied Voltage (x Vs)
O
p
er
at
in
g Ti
m
e
(
s
e
c
s
)
TMS = 1
TMS = 2
TMS = 5
TMS = 10
Undervoltage Inverse Time Curves
1.000
10.000
100.000
1000.000
0
0.2
0.4
0.6
0.8
1
Applied Voltage (x Vs)
Op
e
ra
ti
ng Ti
me
(s
ec
s
)
TMS = 10
TMS = 5
TMS = 2
TMS = 1
( )
xTMS
Vs
V
t
1
1
−
=
( )
xTMS
Vs
V
t
−
=
1
1
Figure 10 Inverse time characteristics
Autoreclose
Most faults on HV and EHV overhead transmission lines are
transient faults, which are removed following line
de-energization. After a short time, the hot gases disperse
and the air de-ionizes. After clearing the fault and deionizing
the fault arc, reclosing can be performed. GRZ100 provides
two autoreclose schemes, single-shot autoreclose and
multi-shot autoreclose.
The GRZ100 autoreclose function can be initiated by any of
the following high-speed protections.
- Protection using telecommunication
- Zone1 extension protection
Single-shot autoreclose
Single-shot reclosing can provide any of three auto-
reclose modes; single-phase autoreclose, three-phase
autoreclose, and single-and three-phase autoreclose.
In the single-phase autoreclose mode, only a faulted
phase is tripped, and then reclosed if a single-phase
earth fault occurs.
In the three-phase autoreclose mode, all three phases
are tripped, and then reclosed regardless of the fault
mode, whether a single-phase fault or a multi-phase
fault has occurred.
In the single- and three-phase autoreclose mode, the
single-phase is reclosed if a single-phase is tripped and
the three phases are reclosed if three phases are
tripped.
Multi-shot autoreclose
In a multi-shot autoreclose, two- to four-shot reclosing
can be selected. The first shot is selected from any of
the four autoreclose modes available in the single-shot
autoreclose scheme.
If reclosing by the first shot fails, three-phase tripping
and reclosing is applied for the second to fourth shots.
Synchronism Check
For the correct operation of three-phase autoreclose, voltage
and synchronism check are necessary. Characteristics of
the synchronism check element are shown in Figure 11.
V
L
: Line voltage
V
B
: Busbar voltage
θ
: Synchronism
check angle
θ
θ
0 deg
Operating zone
V
L
V
B
OV
θ
θ
Figure 11 Synchronism check element
A detected slip cycle is determined by the following equation:
where,
f: slip cycle
θ
: synchronism check angle setting
TSYN: synchronism check timer setting
One-and-a-half Breaker Scheme (Models 300
and 500)
GRZ100 performs two-breaker autoreclose in a one-and-
a-half breaker scheme.
Only single-shot autoreclose is available in Models 300 and
500. Single-phase autoreclose, three-phase autoreclose or
single and three-phase autoreclose can be applied to the
two circuit breakers.
Fault Detector (Models 400 through 500)
For ultra-critical applications, where security is the over-
riding concern and a two-out-of-two tripping philosophy is
specified, GRZ100 can be provided with an independent
fault detector. This fault detector contains its own main
processing unit (MPU) and trip contacts. The trip contacts
of the main protection are connected in series with the fault
detector trip contacts to ensure completely fail-safe operation.
The fault detector incorporates the following six fault
detection elements.
- Multi-level overcurrent element
- Current change detection element
- Earth fault overcurrent element
- Undervoltage element for earth fault detection
- Undervoltage element for phase fault detection
- Undervoltage change detection element
Interfaces for Integral Communication
GRZ100 can be provided with the following interface(s) and
linked to a dedicated optical fibre communication circuit or
multiplexed communication circuit (multiplexer) shown in
Figure 12.
The electrical interface supports CCITT G703-1.2.1, -1.2.2,
-1.2.3, X.21(RS530) and RS422. Twisted pair cable is used
for connecting the relay and multiplexer. In the case of an
f =
180°
Х
TSYN
θ
