ABB Relion 670 Series Applications Manual page 537

1MRK 511 401-UEN Rev. K
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.
tDelayAlm4thHD : It defines the alarm delay time from warning for the calculated fourth
harmonic distortion.
WrnLimit5thHD : It defines the warning limit for the calculated fifth harmonic distortion.
tDelayAlm5thHD : It defines the alarm delay time from warning for the calculated fifth
harmonic distortion.
18.14 Voltage harmonic monitoring VHMMHAI
18.14.1 Identification
Function description
Voltage harmonic monitoring
18.14.2 Application
In order to maintain the power quality for better supply, harmonics in the system must be
monitored. Due to the nonlinear loads connected to the system, harmonics (apart from
fundamental frequency component) are generated and thereby the system voltage is
distorted. Voltage distortion appears to have a little effect on operation of nonlinear loads
connected, either phase-to-phase or phase-to-neutral. Current distortion is limited at the
point of common coupling PCC to control the harmonic current from the utility to the
consumer. Thereby, the voltage distortion must be limited in order to prevent it from
spreading to other facilities.
Voltage harmonic distortion levels can vary drastically, depending on the configuration of
system. These voltage harmonics can damage the equipment as they are designed to operate
for certain range of voltage inaccuracy.
Moreover, in four-wire distribution systems (three-phase and neutral), the currents in the three
phases will return via the neutral conductor, a 120 degree phase shift between corresponding
phase currents that causes the currents to cancel out in the neutral, under balanced loading
conditions. When nonlinear loads are present, any 'Triplen' (3
currents does not cancel out. However, they will be added cumulatively in the neutral
conductor, which can carry up to 173% of phase current at a frequency of predominately 180
rd
Hz (3 harmonic).
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:
Bay control REC670
Application manual
IEC 61850
identification
VHMMHAI
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GUID-BF90E93F-C0F4-43F7-BDD5-F3C289B5535B v1
IEC 60617 ANSI/IEEE C37.2
identification device number
UTHD VTHD
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Section 18
Monitoring
531