Evaluation Of Zero Crossings, Half-Cycle Times, Amplitudes - Hitachi Relion 650 Series Technical Manual

Section 14
Basic IED functions
Table 356: Reference voltage specification
Setting
UConnType
UConnPh
When only one phase voltage is available, the setting UConnPh is used to specify the phase
information that is connected. Selection of "L1/L1-L2" implies that L1 phase is connected if selection
in UConnType is "One phase star", or L1-L2 voltage is connected if selection in UConnType is "One
phase delta". The same is applicable for "L2/L2-L3" and "L3/L3-L1".
14.5.7.3

Evaluation of zero crossings, half-cycle times, amplitudes

When a signal is rated "healthy", ANSGPROC continuously extracts zero crossings in each
connected phase. Using linear interpolation, the time stamp of exact zero crossing point is calculated
between the two consecutive samples of opposite polarity and stored in a cyclic list of zero crossings.
As soon as minimum two zero crossings are detected, the half cycle time is calculated as the
difference between the latest two zero crossings. For the example of ZC
instantaneous half cycle time is calculated as:
Instantaneous half cycle time = ZC
With each new zero crossing, the function updates its moving average of the last settable number of
half-cycle times, which can be configured using the NumOfHalfCycle setting. This information is used
for extrapolating zero crossings and evaluating frequency in the controlled switching algorithms.
For any reference source, the frequency and point-on-wave targets are ascertained by tracking the
signal for a settable number of half cycles. The higher values of NumOfHalfCycle are used to provide
more stable tracking. Conversely, if the system frequency is expected to change rapidly, a lower
value of NumOfHalfCycle can be provided. However, in case of rapid changes in frequency, a low
value of the parameter may lead to inaccurate targeting.
386
Description
Specifies the connection type of the source voltage transformer. It can be selected as:
• One phase star – Any one phase-to-ground voltage signal is available
• Three phase star – All three phase-to-ground voltage signals are available
• One phase delta – Any one phase-to-phase voltage signal is available
• Three phase delta – All three phase-to-phase voltage signals are available
When UConnType is selected as "One phase star" or "One phase delta", the actually
connected phase or phase-to-phase information has to be specified here from the options
• "L1/L1-L2" when either L1-ground or L1-L2 voltage signal is connected to the first
voltage input
• "L2/L2-L3" when either L2-ground or L2-L3 voltage signal is connected to the first
voltage input
• "L3/L3-L1" when either L3-ground or L3-L1 voltage signal is connected to the first
voltage input
Selection in this setting is irrelevant if "Three phase star" or "Three phase delta" is selected
for UConnType setting
When "One phase star" or "One phase delta" is being used, that voltage signal shall
always be connected to the L1 voltage input of the IED irrespective of the phase/
phases that are acquired by the voltage transformer.
If the phase difference between system phases may significantly deviate from 120
degrees, set UConnType to "One phase star" or "One phase delta".
There is no provision for single-phase current signal connection. A 3-phase CT must
always be connected to the IED.
- ZC
2
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1
1MRK 511 557-UEN Rev. A
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and ZC in Figure 172, the
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