Siemens 7SN71 User manual

   


 

   
Instr ction Man al Order No.: E50410-A0007-U501-A1-7691
Version March 1997 Siemens AG 1997


 
       
#        
       !  % 
          "
#
  
 "        ! 
 #   #   # 
 "    !  % # 
!  !   #"     
!  "# !%  % %
  !  !!   ! 
 "  #

 !    !   !
          # ! $ # 
!  %  #       
!     %        
 !  %     "
    

Transient earth-fault relay 7SN71 ĊInstruction Manual Order No.: E50410-A0007-U501-A1-7691

Siemens AG March 1997
The following list of precautions is not intended as a
complete description of all safety precuations which
apply to the operation of the equipment (device, moĆ
dule) since particular operational conditions call for
additional measures.
Warning
Dangerous voltages may occur in cerĆ
tain components of electrical devices
during operation. Incorrect use of these
devices can therefore result in severe
personal injury or substantial damage of
property.
The earthing screw of the device
must be connected solidly to the
protective earth conductor before
any other connection is made.
Hazardous voltages may be present
on all circuits and components conĆ
nected with the supply voltage.
Hazardous voltages may be present
in the device even after disconnecĆ
tion of the supply voltage (storage
capacitors).
Devices with CT circuits must be
terminated.
The limit values given in the TechniĆ
cal data of the manual must not be
exceeded at all, not even during teĆ
sting and commissioning.
Only suitably qualified staff should
work on this device. Correct and
safe operation of this device is deĆ
pendent on proper handling, installaĆ
tion, operation and maintenance.
This instruction manual does not purport to cover all
details in equipment, nor to provide for every possible
contigency to be met in connection with installation,
operation or maintenance.
Should further information be desired or should partiĆ
cular problems arise which are not covered suffiĆ
ciently for the purchaser`s purpose, the matter should
be referred to the local Siemens sales office.
Aqualified person is one who is familiar with the
installation, construction and operation of the device
and who has the appropriate qualifiactions, e.g.
is trained and authorized to operate and maintain
devices/systems in accordance with established
safety practices for devices with electrical circuits
is trained in the proper care and use of protective
equipment in accordance with established safety
practices
is trained in first aid.
CE-Confor ity
This product is in conformity with the directive of the
Council of the European Communities on the approxiĆ
mation of the laws of the Member States relating to
electromagnetic compatibility (EMC Council Directive
89/336/EEC).
Conformity is proved by tests that had been perforĆ
med according to article 10 of the Council Directive in
accordance with the generic standards EN 50081-2
and EN 50082-2 by Siemens AG.
The device is designed and manufactured for appliĆ
cation in industrial environment.
The device is designed in accordance with the inĆ
ternational standards of IEC 255 and the German
standards DIN 57 435 part 303 (corresponding to
DE 0435 part 303).
Further applicable standards: ANSI/IEEE C37.90,
C37.90.1 and C37.90.2.

Transient earth-fault relay 7SN71 ĊInstruction Manual Order No.: E50410-A0007-U501-A1-7691
List of contents I
Page
I
iemens AG ⋅March1997
1 Application 1-1.....................................................................
1.1 Earth fault directional determination 1 - 1................................................
1.2 Functions and features 1 - 4...........................................................
2 Method of operation 2 - 1............................................................
2.1 Current and voltage input (see figure 2.1) 2 - 1...........................................
2.2 Evaluating logic (see figure 2.2) 2 - 3....................................................
2.3 Indication, signalling and test 2 - 3......................................................
2.4 uppression of switching operations 2 - 4...............................................
2.5 Reset 2-4..........................................................................
2.6 Indication of the continuous earth-fault only in forward direction 2 - 4.......................
3 Operatin instructions 3 - 1..........................................................
3.1 afety precuations 3-1...............................................................
3.2 Connection to auxiliary power supply 3 - 1...............................................
3.3 Connection to auxiliary power supply 3 - 2...............................................
3.4 ettings 3-3........................................................................
3.5 Testing 3-3.........................................................................
3.5.1 Test equipment 7VP8300-0 3 - 3.......................................................
3.5.2 Testing of the 7 N71 3-3.............................................................
3.5.3 Earth-fault direction signal 3 - 4........................................................
3.5.4 Continuous earth-fault signal 3 - 4......................................................
4 Technical Data 4-1..................................................................
4.1 Ordering code / MFLB 4 - 2............................................................
5 Housin types and dimensions 5 - 1..................................................
5.1 Panel flush mounting 5-1.............................................................
5.2 Panel surface mounting 5 - 2...........................................................
5.3 Front view of relay 5-3...............................................................
A.1 Connection dia rams A - 1...........................................................
A.1.1 Connection diagram of the 7 N71 (panel surface mounting with AC power supply unit) A - 1...
A.1.2 Connection diagram of the 7 N71 (panel surface mounting with DC power supply unit) A - 1...
X INDEX X-I.........................................................................

Transient earth-fau t re ay 7SN71 ĊInstruction Manua Order No.: E50410-A0007-U501-A1-7691
List of contents
I
Page
II Siemens AG ⋅March1997
[List of] i ustrations
Figure 1.1 Charging process in compensated or isolated networks 1 - 1...............................
Figure 1.2 Direction o the displacement voltage and the earth current (earth- ault isolates at t1)
in
isolated systems 1-2.................................................................
Figure 1.3 Detection o ault location 1 - 3.........................................................
Figure 2.1 Current and voltage input 2 - 2.........................................................
Figure 2.2 Evaluating logic and signalling 2 - 3.....................................................
Figure 2.3 Adjusting elements 2-4..............................................................
Figure 3.1 Connection to c.t. in Holmgreen circuit 3 - 1.............................................
Figure 3.2 Connection to the auxiliary power supply 3 - 2...........................................
Figure 3.3 Test setup 3-4......................................................................
Figure 5.1 Dimensions or housing and panel cutout ( or panel lush mounting) 5 - 1....................
Figure 5.2 Dimensions or housing/mounting and terminal assignment ( or panel sur ace mounting) 5 - 2.
Figure 5.3 Front view o relay 5-3...............................................................
Figure A.5.4 Connection diagram o the 7SN71 (panel sur ace mounting with AC power supply unit) A - 2...
Figure A.5.5 Connection diagram o the 7SN71 (panel sur ace mounting with DC power supply unit) A - 3...
[List of] tab es
Table 4.1 Technical Data 4-1...................................................................
Table 4.2 Selection and ordering data 4 - 2.......................................................

Tran ient earth-fault relay 7SN71 ĊIn truction Manual Order No.: E50410-A0007-U501-A1-7691
Application 1
1 - 1
Sieme s AG ⋅March 1997
1 Application
1.1 Earth fault directional determination
The highly se sitive ta sie t earth-fault relay 7SN71
determi es the directio of tra sie t a d co ti uous
earth faults i systems with isolated eutral, i syĆ
stems with high-impeda ce resistive earthi g a d i
compe sated systems.
The co ti uous earth-faults are o ly i dicated i co Ć
ju ctio with a earth-fault directio al discrimi atio
eleme t.
I the eve t of a earth fault, the eutral-poi t volĆ
tage to earth ca be as high as the full phase voltage.
The phase-to-earth capacita cies of the o -earth-
faulted phases are charged via the tra sformer i ducĆ
ta ce.
This chargi g process is bou d up with a stro g curĆ
re t surge (starti g oscillatio ).
The amplitude of this curre t surge depe ds o the
expa ds of the system a d o co tact resista ce vaĆ
lues at the earth-fault locatio . This curre t flows via
the phase-to-earth capacita cies of the u -effected
li es to earth a d e ters the earth-faulted phase via
the earth-fault locatio .
The curre t flows via this li e to the i -feed tra sforĆ
mers.
Thus the directio of the earth-fault i duced curre t
surge is ide tical with that of the short-circuited curĆ
re t at the same locatio (see figure 1.1)
ÇÇÇÇÇÇÇÇ
ÇÇÇÇÇÇÇÇÇÇÇÇÇÇ


1
2
3
4



        

Tran ient earth-fault relay 7SN71 ĊIn truction Manual Order No.: E50410-A0007-U501-A1-7691
Application
1
1 - 2 Siemens AG ⋅March 1997
At measurin point A, as a result of the transformer
summation circuit, the earth current of the faulted line
is not included in the measurement, as this current
portion flows throu h the summation transformer of
the relevant Holm reen circuit and back, thereby canĆ
cellin itself out. It is the total of the capacitative
earth currents from the non-faulted system which
has an effect. In the dia ram they are summated on
the upper line. The capacitative currents of the non-
faulted lines 1, 3 and 2, 4 accumulate vectorially,
which is why only three arrows instead of four are
shown at measurin point A.
With a transient earth-fault relay, the equalizin curĆ
rent formin with a damped oscillation of 100 to more
than 1ā000 Hz decays after only a few periods.
The displacement volta e VEthereupon also returns
to zero. In earthed systems this takes place after a
number of periods (decay of the Petersen coil - earth
capacitance oscillation circuit); in non-earthed syĆ
stems this occurs after a very short time (fi ure 1.2).
In the case of a continuous earth fault, the equalizin
current in the non-earthed system chan es into the
mostly capacitive continuous earth current or, in comĆ
pensated systems, into the relatively low residual acĆ
tive current.
Earth fault
be innin
end
VE
0
t1
t
Figure 1.2 Direction of the displacement voltage and the earth current (earth-fault isolates at t1) in isolated systems
Examples of typical applications:
If the system is of radial confi uration (fi ure 1.3 a),
the red lamp immediately indicates the faulted line.
If one of the lines consists of several sections (fi ure
1.3 b), the fault is upstream of the last red lamp.
The transient earth-fault relay can also be used wiĆ
thout restrictions in any type of meshed network
(fi ures 1.3 c and 1.3 d). The directional indications
clearly identify the fault location.
Transient earth-fault relays distributed at suitable
points throu hout the system allow detection of the
earth-fault location from the directional indications
(see examples in fi ure 1.3).

Tran ient earth-fault relay 7SN71 #In truction Manual Order No.: E50410-A0007-U501-A1-7691
Application 1

  ⋅ 
  "  
!  " 
 
 
 
     

Tran ient earth-fault relay 7SN71 ĊIn truction Manual Order No.: E50410-A0007-U501-A1-7691
Application
1
1 - 4 Siemens AG ⋅March 1997
1.2 Functions and features
Device versions for panel surface mounting or
flush mounting
Bidirectional measurement, indication and signalĆ
ling
Indication of direction and and continuous earth
fault where displacement voltage 0> 25 perĆ
sists after 2 s
High pick-up sensitivity due to separate detection
and evaluation of total current and displacement
voltage
1 A and 5 A connection for transformer current
matching
Four sensitivity stages
Withing the frequency band of 100 Hz up to
2.5 kHz the pick-up sensitivity is mostly indepenĆ
dent of the frequency of the transient response
Optional suppression of switching operations
Connection to 230 AC
Connection to 100 AC (voltage transformer)
Connetion to 24, 48, 60, 110/125 and 220/250
DC.
Remote reset (reset:24to250 DC)
Automatic reset facility for indications and signals
Signalling and indication of a continuous earth fault
possible only in the forward direction
Command contacts of relay for continuous earth
fault

Tran ient earth-fault relay 7SN71 ĊIn truction Manual Order No.: E50410-A0007-U501-A1-7691
Method of operation 2
2 - 1
Sie ens AG ⋅March 1997
2 Method of operation
2.1 Current and voltage input (see figure 2.1)
The su ation current of the cable-type CT or of the
three phase-current CTs in Holgreen circuit is transĆ
for ed into a proportional voltage in the input circuit
and is supplied to positive and negative co parators.
As soon as the positive or negative trigger threshold
is exceeded, the e ory for the corresponding half-
cycle is set while that of the other is blocked 1.
The three phase voltages for the virtual starpoint of
the voltage transfor er delta via the capacitors in
start-delta connection. Hence, the displace ent volĆ
tage of the syste is located between this point and
the supplied earth potential of the transfor ers. This
voltage is supplied to the positive and negative co Ć
parators via an input transfor er. As soon as the
positive or negative trigger threshold is exceeded and
upon si ultaneous pickup of a current trigger the
corresponding e ory is set while the other is
blocked 2.
In order to prevent incorrect signalling during switĆ
ching operations in the syste , it is verified whether
the displace ent voltage still exceeds approx. 25 eff
after 70 s. Only after this verification is the evaluaĆ
tion of the set e ories released. If this is not the
case, the result are discarded and the e ories are
reset 3.
This function can be disabled by withdrawing the
front plug v". Since in isolated networks the displaĆ
ce ent voltage is present for only a short period of
ti e after a transient earth-fault, the front plug v"
should in this case also be withdrawn.
If after approx. three seconds the displace ent volĆ
tage persists above 25 eff, the annunciation ConĆ
tinuous earth fault" is released 4.

Tran ient earth-fault relay 7SN71 ĊIn truction Manual Order No.: E50410-A0007-U501-A1-7691
Method of operation
2
2 - 2 Siemens AG ⋅March 1997

S
=1
 
>
R
S
>
R
>
>
&
&
S
R
S
R
>
2B1
1B2
1B1
2A1
2A2
2A3
2A4
1A4
2B2
N=1A
N=5A
E
L1
L2
L3
E
PE v
M
Reset
+
-
+
"Re ease"
-
Continous
earth fau t
1
2
3 4
     

Tran ient earth-fault relay 7SN71 ĊIn truction Manual Order No.: E50410-A0007-U501-A1-7691
Method of operation 2
2 - 3
iemens AG ⋅March 1997
2.2 Evaluating logic (see figure 2.2)
Once the set current and voltage memories have
been released 1and evaluated 2, the memories for
the directional indication are set and the corresponĆ
ding relay/LED is activated 3. The respective relay or
LED is also activated 6, once the signals for directioĆ
nal indication and continuous earth-fault 5are releaĆ
sed.
forward
&
&
w1
R
R
&
+
+
-
-
Reset
Continuous earth
fault
4A1
4A2
3B3
3A2
3B2
3A1
3B4
3B1
Transient earth-fault
forward direction
L+
2
H1 K1
H2 K2
H3 K3
3
5
1
6
Continous
earth fault
"Release" 7


reverse
Transient earth-fault
reverse direction
Continuous earth fault


     
2.3 Indication, signalling and test
The indication and signalling for the direction of a
transient earth fault are stored and are therefore not
set anew upon further occurence of a transient earth-
fault. Indication and and signalling for the continuous
earth-fault" are not stored. i.e. are discontinued upon
disappearance of the displacement voltage (cf. also
sections 2.4 and 2.5).
The green LED (Operation") indicates the readiness
(auxiliary voltage) of the device. An alarm signal is
output in the event of an auxiliary voltage supply faiĆ
lure.
The test buttons for forward and reverse direction are
used to test the analog evaluation, the evaluating loĆ
gic, the LEDs and the alarm relays.

Transient earth-fault relay 7SN71 ĊInstructi n Manual Order N .: E50410-A0007-U501-A1-7691
Method of operation
2
2 - 4 iemens AG ⋅March 1997
2.4 Suppression of switching operations
The front plug v" is used to enable or disable the
delay time for control of the displacement voltage
once a directional indication has been effected
through earth faults or switching operations.
If the front plug v" is inserted, switching operations
in isolated systems are not indicated or signalled.
In compensated systems, the plug should always be
withdrawn.
2.5 Reset
Indications and signals can be reset
by pressing the Reset" button on the front plate
via the remote reset with 24 to 250 V
automatically by opening jumper 8 (position as
delivered: closed). Indication and signalling of the
transient earth-fault direction is reset approx. 3 s
after the earth fault has disappeared.
Cauti n!
Electrostatic discharges via the
component connections, the PCB
tracks or the connecting pins of the
modules must be avoided under all
circumstances by previously touĆ
ching an earthed metal surface.
2.6 Indication of the continuous earth-fault only in forward direction
If jumper 7 is opened (position as deliverd: closed),
occurrances of continuous earth faults will only be
indicated in forward direction (tripping contact !) Cauti n!
Electrostatic discharges via the
component connections, the PCB
tracks or the connecting pins of the
modules must be avoided under all
circumstances by previously touĆ
ching an earthed metal surface.
IC
Trimming pot.
Capacitors
Front panel
Jumpers 7 + 8 (Dip-Fix)
Printed board cutout: top view
   

Tran ient earth-fault relay 7SN71 ĊIn truction Manual Order No.: E50410-A0007-U501-A1-7691
Operating instructions 3
3 - 1
Si m ns AG ⋅March 1997
3Operating instructions
3.1 Safety precuations
All saf ty pr cautions which apply for work in l ctriĆ
cal installations ar to b obs rv d during commissioĆ
ning.
3.2 Connection to auxiliary power supply
Figur 3.1 shows th conn ction to a curr nt transforĆ
m r s t in Homgr n circuit.
H r , th starpoint at th lin -sid of th c.t.s must
b conn ct d to t rminal 1 (2B1) or 2 (1B2), whil th
starpoint at th bus-bar sid of th c.t.s must b conĆ
n ct d to t rminal 3 (1B1). Th thr phas voltag s
L1,L2 and L3 ar conn ct d to t rminals 4 (2A1),
5 (2A2) and 6 (2A3), r sp ctiv ly. Th arth d starpoĆ
int of th c.t. is conn ct d ot t rminal 7 (2A4).
1 2
2B1 1B2
3 1B1 4 5
2A1 2A2
6 2A3
7 2A4
t rminals for
flash mounting
1A 5A E
oth r prot ction r lay
.g. O/C r lay
L-
L1
L2
L3
t rminals for
surfac mounting
       

Tran ient earth-fault relay 7SN71 ĊIn truction Manual Order No.: E50410-A0007-U501-A1-7691
Operating instructions
3
3 - 2 Siemens AG ⋅Marc 1997
3.3 Connection to auxiliary power supply
Connection is eit er made to t e 230 V AC mains or
between two p ases (100 V) of t e v.t.s. Connection
to t e station battery is also possible (see figure 3.2).
12 14
1A1 1A3
4 5
2A1 2A2
6 2A3
7 2A4
L1
L2
L3
22 23
4B1 4B2
L+ L-
13 14
1A2 1A3
DC AC DC DC DC AC
Connection
to substation
battery
Connection
to lig ting
system
Connection to t e
voltage transformer
terminals for
flas mounting
terminals for
surface mounting
       

Transient eart -fault relay 7SN71 ĊInstruction Manual Order No.: E50410-A0007-U501-A1-7691
Operating instructions 3
3 - 3
iemens AG ⋅March 1997
3.4 Settings
The pick-up sensitivity is adjusted to the system load
and c.t. ratios by means of the three coding plugs on
the front panel of the 1 or 5 A connection. The setting
is based on the earth current Eof the unearthed
system converted for the secondary side of the c.t.s.
The coding plugs are selected according to the folloĆ
wing table.
Zero-sequence current 0(sec.)
Terminals for
<0.5 A
1A
<2.5 A
1A
<5 A
5A
>5 A
5A
Front plug withdrawn
for normal sensitivity, plug no.
for increased sensitivity, plug no.
3
all
1
2
3
all
1
2
If the marking on the plug is in vertical position, the
plug is withdrawn and effective. In the in-effective,
plugged-in position the marking is horizontal.
3.5 Testing
Function tests of the transient earth-fault relay, incluĆ
ding tests of the connection wiring (e.g. of the cubicle
terminals), can be carried out with test equipment
7VP8300-0.
3.5.1 Test equipment 7VP8300-0
Test equipment 7VP83 serves to test the transient
earth-fault relay 7TH2300-0ā/ā7 N70 and 7 N71.
The test equipment operates at 230 V AC.
Test current 0and test voltage 0for the directional
detection of the transient earth-fault are made avaiĆ
lable via the terminal sockets.
The connection of the test current/voltage and the
phase rotation of the current are effected by means
of pushbutton 1. Activation of the test current/volĆ
tage is indicated by LED H1.
3.5.2 Testing of t e 7SN71
All safety precautions which apply for work in electriĆ
cal installations are to be observed during tests.
Before testing, the current and voltage inputs of the
test object must be isolated.
Otherwise, the accuracy of the test results can be
invalidated.
the test object ic connected to test equipment 7VP83
as shown in figure 3.3.

Transient eart -fault relay 7SN71 ĊInstruction Manual Order No.: E50410-A0007-U501-A1-7691
Operating instructions

3 - 4 Siemens AG ⋅March 1997
3.5.3 Eart -fault direction signal
If the pushbutton of 7 P83 is pressed to forward"
(>100 ms), the red "LED " of 7SN71 must light
up. In addition, the forward" signal (relay contact)
must be released.
If the pushbutton is pressed to reverse" (>100 ms),
the yellow "LED ā" of 7SN71 must light up. In adĆ
dition, the reverse" signal (relay contact) must be
released.
For the 1 A input circuit of the test object, the setting
of the sensitivity (via front plugs 1 to 3) has no beaĆ
ring upon the test.
For the 5 A input circuit, front plugs 1 to 3 must be
withdrawn.
Connection of the test current/voltage is independent
of the phase relation of the line voltage. If testing is
started during zero crossing of the voltage wave, an
incorrect directional detection may result. In this case,
repeated measurements must be carried out.
3.5.4 Continuous eart -fault signal
In order to test the continuous earth fault" signal,
the rocking switch must be actuated for approx. 4 s
until after approx. 2 s the indication for continuous
earth fault" is given (red LED and relay)
S1
L1-3 L
H1
E
N
E
E
N/1 A
E
N/5 A
220
7VP8300-0 ā7SN71
Test equipment
   