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Harmonic distortion detection (HHD)
4.3.2
Detections about total harmonic and demand distortion (HHD) will be performed after the DFT
analysis has been performed.
Detection of total harmonic distortion (THD)
(i)
THD presents the ratio of RSM of all harmonics components to the fundamental component.
Two ratios (�� ��
�� and �� ��
h
�� 1 ) and current (�� �� and�� 1 ):
Detection of total demand distortion (TDD)
(ii)
TDD presents that ratio of RSM of all harmonics components (�� �� ) to the peak value in the
fundamental voltage (�� 1-�������� ).TheTDD ratio (�� ������ ) is computed in equation (4.3-5):
Note: The user can clear HHD values from the LCD screen (Figure 4.3-2). Through the
IEC61850 communication, the upstream user can reset them using reset control
command. See section 4.3.5, for more information.
Data window
(iii)
During the THD and TDD calculations, the equations use inputs having been memorized with
time-averaged data. Figure 4.3-3 illustrates input data is collected from the data window
memory. Note that its window can set the span of data collection period (��4–��10 sampling
locationsaredeterminedwiththewindow),thenthedistortion will be calculated. The time span
of 'data window' is set by settings [AverageTime-V] (for voltage) and [AverageTIme-I] (for
current).
�� ) arecalculatedusingequation (4.3-3) and (4.3-4) with voltages (�� �� and
h
2
√ ∑ ��
��
��
=
× 100[%]
��ℎ��
��
1
√∑ ��
2
��
��
=
× 100[%]
��ℎ��
��
1
√ ∑ ��
2
��
��
=
������
��
1_��������
- 556 -
× 100[%]
6F2T0207 (0.01)
(4.3-3)
(4.3-4)
(4.3-5)
GRE200 (5,6)
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