Hitachi Relion 670 Series Applications Manual page 352

Section 15
Monitoring
• Poor power quality
• Increase in operational cost due to less productivity
• Damage to sensitive equipment in nearby facilities.
In general, harmonics can cause reduced equipment life if a system is designed without considering
the harmonics and if the equipment is not designed to withstand harmonics. Hence, it is important to
measure and monitor harmonics in power systems. Harmonic voltage distortions on 161 kV power
system and above is limited to 1.5% of total harmonic distortion (THD), in with each individual
harmonic is limited to 1.0%.
15.12.4 Setting guidelines
The recommended limits for total harmonic distortion and individual harmonic distortion are available
in the IEEE 519-2014 standard. The limits are based on measurements which are done at the point
of common coupling. It should not be applied to either individual pieces of equipment or at locations
within a user's facility. In most cases, harmonic voltages and currents at these locations could be
found to be significantly beyond recommended limits at the PCC due to the lack of diversity,
cancellation, and other phenomena that tend to reduce the combined effects of multiple harmonic
sources to levels below their algebraic summation.
15.12.4.1 Setting procedure on the IED
Parameters for VHMMHAN function are set via the local HMI or PCM600.
Common base IED values for primary voltage (UBase) is set in the global base values for settings
function GBASVAL.
GlobalBaseSel: To select GBASVAL function for reference of base values.
WrnLimitTHD: It defines the warning limit for the calculated total harmonic distortion. According to
standard IEEE 519-2014, harmonic voltage distortions on a power system 161 kV and above is
limited to 1.5% total harmonic distortion (THD) with each individual harmonic limited to 1.0%.
tDelayAlmTHD: It defines the alarm time limit for the calculated total harmonic distortion which is
applied after the warning signal pickup and depends on its sustainability. This intimates the operator
to take corrective operations immediately, otherwise the system will go under thermal stress.
WrnLimit2ndHD: It defines the warning limit for the calculated second harmonic distortion. According
to standard IEEE 519-2014, harmonic voltage distortions on power system 161 kV and above is
limited to 1.0% for each individual harmonic.
tDelayAlm2ndHD: It defines the alarm time limit for the calculated second harmonic distortion which
is applied after the warning signal pickup and depends on its sustainability.
WrnLimit3rdHD: It defines the warning limit for the calculated third harmonic distortion. According to
standard IEEE 519-2014, harmonic voltage distortions on power system 161 kV and above is limited
to 1.0% for each individual harmonic.
tDelayAlm3rdHD: It defines the alarm time limit for the calculated third harmonic distortion which is
applied after the warning signal pickup and depends on its sustainability.
WrnLimit4thHD: It defines the warning limit for the calculated fourth harmonic distortion. According to
standard IEEE 519-2014, harmonic voltage distortions on power system 161 kV and above is limited
to 1.0% for each individual harmonic.
346
Minimum and maximum voltage limit is set as 5% of the UB and 300.0% of UB
respectively. If the voltage is outside the above range, the calculation of total harmonic
distortion, individual harmonic distortion and crest factor are blocked, and outputs are
provided as zero.
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