G. Ziegler. Digital Differential Protection
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G. Ziegler, 10/2005 page 121
Differential Protection Symposium
Belo HorizonteNovember 2005
Protection of a short line lines
Differential relay using direct digital relay-to-relay communication
Communication via direct relay-relay connection
Fibre typeoptical wavemaximum permissible
length attenuationdistance
Multi-mode
62.5/125 µm820 nm16 dBca. 3.5 km
Monomode
9/ 125 µm1300 nm29 dBca. 60 km
9/ 125 µm1500 nm29 dBca. 100 km
D
7SA6
D
7SA6
A
B
G. Ziegler, 10/2005 page 122
Differential Protection Symposium
Belo HorizonteNovember 2005
Line differential relaying using digital communication
Chain topology or
redundant ring topology
O
E
O
E
X21 or
G703.1
X21 or
G703.1
Communication
converter
A
B
C
Communication
network
typical <1.5 km
multimode fibre
62.5/ 9/ 125 µm
D
7SD52
D
7SD52
D
7SD52
G. Ziegler, 10/2005 page 123
Differential Protection Symposium
Belo HorizonteNovember 2005
Differential protection
with communication through data net
l Microsecond exact time keeping in the relays
n Each relay has its individual time keeping
n Sent and received telegrams get microsecond accurate time stamps
l Special relay properties for network communication
Measurement of propagation times and automatic correction 0 -30 ms
Detection of channel switching in the network
Unique address for each relay (1 -65525)
to detect signal misdirection (channel cross-over of loop-back)
Measurement of channel quality (availability, error rate)
l Change of the network path -> Adaptive add-on stabilisation
Settable time difference to consider given data transmission asymmetry
l Adaptive topology recognition
Automatic recognition of connections and remote end devices
Automatic re-routing from ring to chain topology if one data connection fails
In case of multi-terminal protection, remaining relay system continues operation
if one line end is switched off and the relay is logged out for maintenance
G. Ziegler, 10/2005 page 124
Differential Protection Symposium
Belo HorizonteNovember 2005
Individual time references by synchro-phasors
Definition of a
Definition of a
synchro
synchro
-
-
phasor
phasor
:
:
Synchro
Synchro
-
-
phasors
phasors
, are
, are
phasors
phasors
, which are measured at different network locations by
, which are measured at different network locations by
independent devices and referred to a common time basis
independent devices and referred to a common time basis
Time reference
Ort : B
Ort : A
relay A
RE
i
A
i
B
I
A
I
B
IM
relay B
G. Ziegler, 10/2005 page 125
Differential Protection Symposium
Belo HorizonteNovember 2005
Phasorsynchronisation between line ends
AB
∆I
∆I
c
u
r
r
e
n
t
p
h
a
s
o
r
s
.
.
.
t
A
1
c
u
r
r
e
n
t
p
h
a
s
o
r
s
.
.
.
t
B
3
t
A1
t
V
t
PT2
t
PT1
t
A1
t
A2
t
A3
t
A4
t
A5
t
AR
t
B1
t
B2
t
B3
t
B4
()
D
t-
AR
t-
A1
t
2
1
PT2
t
PT1
t ==
Signal transmission time:
t - t t
TP2ARB3
=
I
B( t
A3
)
I
B( t
B3
)
α
°⋅=α 360
T
t - t
P
A3B3
t
BR
t
D
Sampling instant:
G. Ziegler, 10/2005 page 126
Differential Protection Symposium
Belo HorizonteNovember 2005
Specification of data channel for line differential protection
based on CigreReport: Protection using Telecommunication *)
Data rate64 kbit/s(min.)
Channel delay time:< 5 ms
Channel delay time unsymmetry:< 0.2 ms
Bit error rate normal:< 10
-6
during power system fault< 10
-5
*)
Availability:> 99.99 %
*) Report of WG34/35.11, Brochure REF. 192, CigreCentral Office, Paris, 2001,
*) It is suggested that for a BER of less than 10
-6
the dependability shall not suffer a noticeable deterioration .For a
BER of 10
-6
to 10
-3
the teleprotectionmay still able to perform its function although a loss in dependability is to be
expected.
G. Ziegler, 10/2005 Seite 116
Differential Protection Symposium
Belo HorizonteNovember 2005
Digital Protection
of
Generators and Motors
Gerhard Ziegler
G. Ziegler, 10/2005 Seite 117
Differential Protection Symposium
Belo HorizonteNovember 2005
a
a
c
A
S S
S S
A
S
S
A
1234
1
2
3
56
I
A
/I
n
I
S
/I
n
ConnectioncircuitOperatingcharacteristic
Generator differential protection
G. Ziegler, 10/2005 Seite 118
Differential Protection Symposium
Belo HorizonteNovember 2005
a
b
c
A
A
A
Generator HI differential protection
G. Ziegler, 10/2005 Seite 119
Differential Protection Symposium
Belo HorizonteNovember 2005
a
b
c
A
S S
S S
A
S
S
A
Transversedifferential protection