Numerical Pilot Protection 7SD52 using digital wide-band communication

1
Numerical Pilot Protection 7SD52 using digital
wide-band communication
2
Numerical pilot protection relay 7SD52
Universally applicable
to
power system
n
configurations
up to
six ends
,
containing

OH-
Lines
q
Cables
q
Transformers
q
n
For
digital
data transmissen
Via
dedicated optical fibres
q
Via
Communication networks
q
3
Numerical Pilot Differential Protection Principle
IA
IB
IAS , IAC
DI
DI
IBS , IBC
ID
j
operate
IA
IAC
stabilize
IB
ID
Operate ID ?IA IB? Bias IB ?IA
IB? Operating Criterium ID ? K1 K2 . IS
IBS
IAS

IBC
IB
IA IAS j IAC IB IBS j IBC
4
Definition of Synchronous Phasor measured at
different locations based on a common time
reference
5
Numerical pilot protection Advanced Fourier
analysis of the currents - Supress DC
components, harmonics
6
Advanced Fourier Transformation - Optimized
filtering coeffizients for 7SD52 -gt Suppress DC 4
times better thanconventional Fourier-filters -gt
Archieve high sensitivity
i0
i1
i2
iN
Dt
0
1
2
N
3 . . . .
n
0
1
2
N
3 . . .
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Advanced Full Cycle Fourier analysis Filter
characteristic
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Orthogonal Current Components (Advanced Fourier
Filter)
wt
I(wt)
Æ 0
j IC
I
wt
t 0
IS
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Numerical Pilot Differential Relay Propagation
Time Measurement and Phasor Angle Correction
A
B
?I
?I
...
IS(A), IC(A)
tA1
tA1
tL1
tB1
tA2
tB2
tV
tA3
tB3
tA4
tL2
tB4
....
IS(B), IC(B)
tV
tA1
tA5
tB3
IB(tA3)
Propagation time tL1 tL2 1/2 x (tA-reception -
tA1- tV) Corrected sampling instant tB3
tA-reception -tL2
?
IB(tB3)
? (tB3 - tL2) x (360O/Tperiod)
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Example for the delay time calculation
Flight from Berlin lt-gt New York You can not
calculate the duration of a flight if you look at
the clock in Berlin on departure and later note
the local New York time on arrival. The reason
are the different time zones.The relays are also
in two time zones.. Each relay has its own 1 us
resolution timer.
Tdepart / B-gtNY (600) --------------------gt
Tarrival / B-gtNY (800) From the flight back
from New York to Berlin the local departure time
in NY and the arrival time in Berlin is T
arrival / NY-gtB (2300) lt--------------- T
depart / NY-gtB (900) Under the assumption, that
the flight to New York and the flight back from
NY have the same durationthe relevant time
results can be calculated. The time difference
between NY and B and the duration of the flight
(transmission time)
Duration ( T arrival / B-gtNY - T depart /
B-gtNY T arrival / NY-gtB - Tdepart / NY-gtB ) /
2 Time difference (Tdepart / B-gtNY - Tarrival
/ B-gtNY Tarrival / NY-gtB - Tdepart / NY-gtB ) /
2 Duration (800 - 600 2300 - 900) / 2
8 hours (-gt delay time) Time diff. (6 Uhr -
8 Uhr 23 Uhr - 9 Uhr)/2 6 hours (-gt
difference between the time zones)
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Coded message of current differential protection
7SD52
HDLC FRAME FORMAT
Frame Check Seqence (FCS)
Opening Flag
Address Field (A)
Control Field (C)
Information Field (I)
Closing Flag
01111110
16 bits relays address
8 or 16 bits
any length 0 - N bits
32 bits
01111110
Synchronizing
message validation
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Numerical pilot differential protection
Communication options
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Application for a three terminal configuration
Monomode fibre optic cable up to 35 km with 1300
nm interface
Monomode fibre optic cable up to 10 km (1300 nm
modul)
Distance relay 7SA52
X21 G703.1
SDH comms-network
o
e
820 nm max. 3 km
e
o
OptionI-REGB
Comms- converter G703.1 64 kBitX21 N64
kBit (1?N?8)
time synchronisation
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Scope of functions / Hardware options
Numerical line differential protection 7SD52
- For system configurations with up to 6
terminals - Fast high set charge comparision
(subcycle trip)- Sensitive current phasor
differential - Inrush restraint (2nd harmonic)
and vector group adaption - CT saturation
detector - Autoreclosure 1/3 pole - Overload
protection - Switch on to fault protection - 4
remote commands, 24 remote signals
3Iph, and IE 4 U 8 binary inputs 16 contacts
1 - 2 protection interfaces System
interface PC-interface Time synchronisation
½19
16 binary inputs 24 contacts 24 binary inputs 32
contacts Option 5 fast trip contacts
119
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Communication Options

• FO5 distance 1,5 km (with clock feed-back)
• FO6 distance 3km

820 nm1,5 km / 3 km
internal

• FO7 distance 10km

1300 nm10 km
internal

• FO8 distance 35km

O
1300 nm35 km
internal

• KU hook-up to communication network

X21 G703
external
Km data for worst-case conditions
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Hardware option of the comms interfaces
Remote line end 2
Plug in modules
Remote line end 1
Protection interface 1Port D
Synchronous N x 64kB/sec
Subst. control interface
Substation control
communication modules
Interfacemodul 2
FO (Fibre optic) or RS485or RS232 Available
ProtocolsIEC - standard
RS485 or FO
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Main board of the relay with its Communication
- Interfaces
Main processor board of the relay Sockets for
the communicationmodules
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Adaptive Algorithm Fast Charge comparison and
very sensitive Phasor differential

Charge comparison Fast normal trip stage
IDiffgtgt Setting 0,67ILoadmax/IN Fast, lt1cycle
Phasor differential For high resistive
faultsIDiffgt Setting 0,1-0,2 IN
1 cycle Phasor, fundamental frequency
Every 5ms (128-512 bBit), 10 ms (64 kBit)
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Adaptive differential relayingConsideration of
CT- and communication-errors
IDiffIN,load.
trip
I2
I3
I1
I2
restrain
0,15
I3
IDiffgt
I1
Through fault
load
I1
Irestr IN,Betr.
0.5
Calculated Phasor sum
IDiff I1 I2 I3
IDiff Ilow set
Minimum pick-up
IRestrain ? c.t. tolerance ? Syncronising
tolerance
Restrain
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Spill Current through Line Charging Capacitances
Source V1
Kichhoff equation I1 I2 - IDiff - IC
0 Service conditions IDiff 0, IC I1 I2
? Difference equals charging
current Pick-up value IDiffgt gt2,5.. 4 IC ?
sensitive set point at short lines,
minimum 0,1 IN
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Setting above spill currents c.t. error and
line charging
Resulting set point
Set points
IDiff
Percentage bias related to c.t. errors
IDiff - I1 I2 f1 I1 f2 I2 Load
I1 IN IDiff???0,1 I1 0,1 IN Through
Fault I1 10 IN IDiff 10,5 IN - 9,5
IN IN
IDiffgt
Minimum pick-up related to line charging current
I1

• IDiffgt set point gt line charging current
• Percentage bias gt Sum of c.t. errors

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Approximated c.t. ToleranceBasis for the
restraint current calculation
IDiff
I1
Fault current tolerance

Tolerance of a real CT
Load current tolerance

ALFe / ALFN IN,c.t
I1
parameter 7SD52
Example 10P10, fB lt 3, fK at ALFN 10
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Current transformer data
C.t. Parameter
c.t. e.g. 5P20, 10VA
Pi PN
tolerance at ALFN
With PB Pleads Prelay (?0,1
VA)
ALFe ALFN
Pi PB
Thumb rule Ri ? 0,1...0,2 RN RN at 10 VA ?
10? gt Ri ? 2 ?
ALFe ALFN
2 VA 10 VA

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2 VA 1 VA

• Resulting Relay Parameter
• effective ALF / nominal ALF 4 (calculation as
  per above)
• IEC 44 -1 tolerance in load area up to ALFe /
  ALFN 1 with 5P, 3 with 10P c.t.s
• total error at accuracy limit nN 5 with
  class, 5P and 10 10 P

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Internal restraint current calculation due to
CT-errors
The restraint current is the sum of the maximal
expected CT-errors
5P20 20 VA 16001ALFe/ALFN 5fLoad 1 1
(0,01) fSC 1 5 (0,05)
5P20 20 VA 16001ALFe/ALFN 2fLoad 2 1
(0,01) fSC 2 5 (0,05)
IN,load 1600 A
IC 100 A
1200 A 5600 A
800 A 4800 A
10P10 10 VA 4001ALFe/ALFN 1fLoad 3 3
(0,03) fSC 3 10 (0,1)
400 A 800 A
IStab 2.5 line charge currents (basic
restraint value) ? c.t. error currents IDiff
actual deviation of vector summation and charge
summation Case 1 (Through load) IRest 2,5
100 A 800 A 0,01 1200 A 0,01 400 A
0,03 282 A Irestr / IN,load
0,176 Idiff 100 A

IDiff / IN,load
0,063 Case 2 (Through fault) IRest 2,5 100 A
4800 A 0,01 5600 A 0,05 800 A 0,1
658 A Irestrain / IN,load 0,41 IDiff 40
A

IDiff / IN,load 0,025
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CT Saturation detector based on harmonic analysis
ct I2
ct I1
Harmonic content of the differential current
2
0
Id I1 - I2
0
Harmonic order
10
0
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Charge comparison Operating Principle
I
I
1
3
protected Line configuration
I
4
1
2
3
4
Q
Q
Q
Q
Q
diff
I
2
Q
2
Q
1
Q
3
Q
4
3
1
2
3
2
1
2
1
1
Q
Q
Q
Q
Q
Q
Q
Q

Q
part
part
p
art
S
7SD52
7SD52
7SD52
2
2
3
4
3
3
4
4
4
Q
Q
Q
Q
Q

Q
Q
Q

Q
Q
part
part
part
diff
1
2
3
4
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Charge Comparison Charge calculation, Operating
characteristic, Tripping times
Operate
diff
Q
D
(internal fault)
Charge calculation by numerical integration
slope depending on
Settable pick-up value
Q
IDiffgtgt
1
Restraint Area
qdiff12.dsf
t
t
t
t
t
t
t
0
1
2
3
4
5
6
Calculated charge restraint valuefrom CT-errors
, synch. errors
QRest
Current Measuring window
Relay calculates the charge. Setting as current
value IDiffgtgt
5 ms (50 Hz)
Corrected time instantsafter end-to-end time
synchronisation
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7SD52 Pilot Protection Sliding data windows
fault- inception
current, voltage
voltage
current
time
5 ms charge and 20 ms phasor data windows
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Familiar with digital communication networks
Features of the relay to relay communication

• Synchronous data transmission by HDLC- protocol
  
• Permanent supervision of the data transmission
• Measurement and compensation of signal
  transmission time (max. 20 ms)
• Counts number of invalid telegrams
  Blocking the diff.protection if transmission
  failure rate is too high
• Settings for the data transmission (N64
  kBit/s, N settable from 1 - 8, synchronous
  HDLC-protocol)
• Communication device addresses (Protection
  devices are clearly assigned to a defined
  protection section)
• Detection of reflected data in the loops in
  comms- network
• Step 2 Microsecond exact time synchronisation
  via satellite (civil - IRIG-B) (If
  signal transmission time depends on the
  transmission direction, Online high
  resolution fault recorder)

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Ring and Chain topologie
Automatic change fromclosed ring to chain, if
one connection is lost or not available
side 2
side 3
I2
Connection to other diff. relays
I3
I3I1
I2
I1I2
I3
I1
I3I1
I1I2
side 1
Closed ring
Partial current summation
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Breaker-and-a-half Scheme, Through Fault
Stabilisation
busbar 2
busbar 2
87L
To remote end
87L
If through fault current
To remote end
If through fault current
87L
busbar 1
busbar 1
Partial differential
Full differential
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Topologies Chain topology for max. 6 line ends
1
3
2
PI1
PI1
PI2
PI1
PI2
PI - Protection Interface
PI1
4
6
5
PI2
PI1
PI2
PI1
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Topologies Ring topology, 6 line ends
3
1
2
PI1
PI2
PI1
PI2
PI2
PI1
PI1
PI2
4
6
5
PI2
PI1
PI2
PI1
PI - Protection Interface
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Web-Browser based commissioning tool
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7SD52 Commisioning and Monitoring using
Web-Browser