ABB Relion 670 Series Applications Manual page 536

Section 18
Monitoring
Various practical conditions which have dynamic characteristics like the speed of locomotion,
load and line condition will make this problem even worse. Harmonic current increases the
heat dissipation due to hysteresis and eddy currents, which causes stress on insulation
materials. Harmonic current increases transmission loss and the voltage drops.
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%.
Current harmonic limits vary based on the short circuit strength of the corresponding system
they are injected into. Harmonic current limit defines the maximum amount of harmonic
current that can be inject into the utility system. The difference between THD and TDD is used
to calculate the harmonics level during light load conditions.
18.13.3 Setting guidelines
The recommended limits for total harmonic distortion and individual harmonic distortion are
available in the IEEE 519 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.
18.13.3.1 Setting procedure on the IED
Parameters for CHMMHAI function are set via the local HMI or PCM600.
Common base IED values for primary current (
settings function GBASVAL.
GlobalBaseSel : It is used to select GBASVAL function for reference of base values.
MaxLoadCurr : Maximum demand load current at PCC for total demand distortion calculation.
When the point of common coupling (PCC) is considered at the service entrance or utility
metering point, IEEE 519 standard recommends that the maximum demand load current must
be calculated as the average current of maximum demand for the preceding 12 months.
WrnLimitTDD : It defines the warning limit for the calculated total demand distortion.
Harmonic current distortions on a power systems with ratio between the maximum short
circuit current to the maximum demand load current is 20, limited to 5% of the total demand
distortion (TDD).
tDelayAlmTDD : It defines the alarm delay time from warning for the calculated total demand
distortion.
WrnLimitTHD : It defines the warning limit for the calculated total harmonic distortion.
tDelayAlmTHD : It defines the alarm delay time from warning for the calculated total harmonic
distortion. This intimates the operator to take corrective operations immediately, otherwise
the system will undergo thermal stress.
530
Minimum and maximum current limit is set as 5% of the
respectively. If the current is outside the above range, the calculation of total
harmonic distortion, individual harmonic distortion, total demand distortion
and crest factor are blocked and outputs are provided as zero.
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Bay control REC670
Application manual