In case of electric traction systems, it generates various power quality problems that have an
important impact on its distribution network. DC traction loads, fed through AC/DC rectifiers,
generates non-linear voltages and currents on the AC system, that will result in harmonic
voltage distortion of the power supply system. Traction power supply system creates power
quality problems to the corresponding grid, which can cause:
•
Poor power quality
•
Increase in operational cost due to less productivity
•
Damage to sensitive equipment in nearby facilities.
GUID-45A6724C-1FF0-4910-9878-01518111EB26 v1
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%.
14.11.3
Setting guidelines
GUID-57719753-00C3-43F6-97B5-AA3B22618A3F v1
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.
14.11.3.1
Setting procedure on the IED
GUID-60CEC5EC-19DC-49E6-946C-FE3883B67975 v1
Parameters for VHMMHAI function are set via the local HMI or PCM600.
GUID-B3611E99-63AD-4722-BFAA-3BC089F9AFF6 v2
Common base IED values for primary voltage (
UBase) is set in the global base values for
settings function GBASVAL.
GlobalBaseSel: It is used to select GBASVAL function for reference of base values.
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.
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.
WrnLimit2ndHD: It defines the warning limit for the calculated second harmonic distortion.
tDelayAlm2ndHD: It defines the alarm delay time from warning for the calculated second
harmonic distortion.
WrnLimit3rdHD: It defines the warning limit for the calculated third harmonic distortion.
tDelayAlm3rdHD: It defines the alarm delay time from warning for the calculated third
harmonic distortion.
WrnLimit4thHD: It defines the warning limit for the calculated fourth harmonic distortion.
1MRK 505 370-UEN D
Section 14
Monitoring
Busbar protection REB670
381
Application manual
Содержание REB670 Series
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