Siemens siprotec 7SD5 User Manual page 226

2 Functions
starpoint of a source transformer. A relatively sensitive setting can be applied for this
value, as the measurement of the starpoint current is quite accurate by nature.
If the direction determination must be carried out with the negative sequence system
signals, the setting values 3U2> (address 3166) and 3I2> (address 3167) are deci-
sive for the lower limit of the direction determination. The setting values must in this
case also be selected such that operational asymmetry in the system does not lead to
a pickup.
If you are using the zero-sequence power protection and the fault direction is deter-
mined on the basis of the zero-sequence power, address 3169 S forward indicates
the value of the compensated zero-sequence power above which the direction is rec-
ognized as forward. This value should be smaller than the reference power S ref (ad-
dress 3156, see above paragraph at „Zero-Sequence Power Stage"). This ensures
the availability of direction determination even with smaller zero-sequence power con-
ditions.
The position of the directional characteristic can be changed in dependance of the se-
lected method of direction determination (address 3160 POLARIZATION, see above).
All methods based on angle measurement between measured signal and reference
signal (i.e. all methods except POLARIZATION = zero seq. power), allow the angle
range of the direction determination to be changed with the setting angles Dir.
ALPHA and Dir. BETA (addresses 3162 and 3163). This parameter can only be
altered with DIGSI
the presettings may be left unchanged. If you want to change these values, refer to
margin heading „Direction Determination with Zero-Sequence System" for the angle
determination.
The direction determination POLARIZATION with zero seq. power determines the
directional characteristic by means of the compensation angle PHI comp (address
3168) which indicates the symmetry axis of the directional characteristic. This value
is also not critical for direction determination. For information on the angle definition,
refer to margin heading „Direction Determination with Zero-Sequence Power". This
angle determines at the same time the maximum sensitivity of the zero-sequence
power stage thus also affecting indirectly the trip time as described above (margin
heading „Zero-Sequence Power Stage").
Teleprotection with The earth fault protection in the 7SD5 may be expanded to a directional comparison
Earth Fault Protec- protection using the integrated teleprotection logic. Additional information regarding
tion the available teleprotection schemes and their mode of operation may be obtained
from Section 2.9. If this is to be used, certain preconditions must already be observed
when setting the earth current stage.
Initially, it must be determined which stage must operate in conjunction with the tele-
protection. This stage must be set directional in the line direction. If, for example, the
3I
3I0> = Forward (see above „Definite Time Stages").
Furthermore, the device must be informed that the applicable stage has to function to-
gether with the teleprotection to allow undelayed release of the tripping during internal
faults. For the 3I
YES. The time delay set for this stage T 3I0> (address 3132) then functions as a
back-up stage, e.g. during failure of the signal transmission. For the remaining stages
the corresponding setting parameter is set to NO, therefore, in this example: address
3123 3I0>> Telep/BI for stage 3I
3I
If the echo function is used in conjunction with the teleprotection scheme, or if the
weak-infeed tripping function should be used, the additional teleprotection stage
226
®
under Additional Settings. As these set values are not critical,
> stage should operate as directional comparison, set address 3130 Op. mode
0
> stage this means that address 3133 3I0> Telep/BI is set to
0
>>>, address 3148 3I0p Telep/BI for stage 3I
0
>>, address 3113 3I0>>> Telep/BI for stage
0
(if used).
0P
7SD5 Manual
C53000-G1176-C169-1