8.2.7.6
Internal ground-fault protection structure
The protection is internally divided into the following parts:
1. Four residual overcurrent steps.
2. Directional supervision element for residual overcurrent steps with integrated
directional comparison step for communication based ground-fault protection
schemes (permissive or blocking).
3. Second harmonic blocking element with additional feature for sealed-in blocking
during switching of parallel transformers.
4. Switch on to fault feature with integrated Under-Time logic for detection of breaker
problems during breaker opening or closing sequence.
8.2.7.7
Four residual overcurrent steps
Each overcurrent step uses operating quantity Iop (residual current) as measuring
quantity. Each of the four residual overcurrent steps has the following built-in facilities:
•
Directional mode can be set to
Disabled
/
Non-directional
/
Forward
/
Reverse
. By this
parameter setting the directional mode of the step is selected. It shall be noted that the
directional decision (Forward/Reverse) is not made within the residual overcurrent
step itself. The direction of the fault is determined in common “directional
supervision element”.
•
Residual current pickup value.
•
Type of operating characteristic (inverse or definite time). By this parameter setting
it is possible to select inverse or definite time delay for the ground-fault protection.
Most of the standard IEC and ANSI inverse characteristics are available. For the
complete list of available inverse curves please refer to section
.
•
Type of reset characteristic (
Instantaneous
/
IEC Reset
/
ANSI Reset
). By this
parameter setting it is possible to select the reset characteristic of the step. For the
complete list of available reset curves please refer to section
""
.
•
Time delay related settings. By these parameter settings the properties like definite
time delay, minimum operating time for inverse curves, reset time delay and
parameters to define user programmable inverse curve are defined.
•
Supervision by second harmonic blocking feature (
Enabled
/
Disabled
). By this
parameter setting it is possible to prevent operation of the step if the second harmonic
content in the residual current exceeds the preset level.
•
Multiplier for scaling of the set residual current pickup value by external binary
signal. By this parameter setting it is possible to increase residual current pickup
value when function binary input MULTPUx has logical value 1.
Simplified logic diagram for one residual overcurrent step is shown in figure
.
1MRK 511 365-UUS A
Section 8
Current protection
Phasor measurement unit RES670 2.1 ANSI
203
Technical manual
Содержание Relion 670 Series RES670
Страница 1: ...Relion 670 series Phasor measurement unit RES670 2 1 ANSI Technical manual ...
Страница 2: ......
Страница 36: ...30 ...
Страница 76: ...70 ...
Страница 106: ...100 ...
Страница 150: ...144 ...
Страница 274: ...268 ...
Страница 326: ...320 ...
Страница 356: ...350 ...
Страница 382: ...376 ...
Страница 416: ...410 ...
Страница 590: ...584 ...
Страница 604: ...598 ...
Страница 694: ...688 ...
Страница 756: ...750 ...
Страница 834: ...828 ...
Страница 836: ...830 ...
Страница 876: ...870 ...
Страница 886: ...880 ...
Страница 887: ...881 ...