ABB REB670 Series, Applications Manual

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14.9.3 Setting guidelines
GUID-D3BED56A-BA80-486F-B2A8-E47F7AC63468 v1
The settings
tAlarm and tWarning are user settable limits defined in hours. The achievable
resolution of the settings is 0.1 hours (6 minutes).
tAlarm and tWarning are independent settings, that is, there is no check if
tAlarm > tWarning.
The limit for the overflow supervision is fixed at 99999.9 hours.
The setting
tAddToTime is a user settable time parameter in hours.
14.10 Current harmonic monitoring CHMMHAI
GUID-692151F8-812B-4B32-AE86-E7A4E4B0101B v1
14.10.1 Identification
GUID-C7863D78-34DB-42E5-90FE-6483EDAAF319 v1
Function description IEC 61850
identification
IEC 60617
identification
ANSI/IEEE C37.2
device number
Current harmonic monitoring CHMMHAI ITHD ITHD
14.10.2 Application
GUID-987BCB6C-C559-42EE-9AAB-5F71189A58C6 v2
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
rd
, 9
th
…) harmonics in the phase
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
Hz (3
rd
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:
• Poor power quality
• Increase in operational cost due to less productivity
• Damage to sensitive equipment in nearby facilities.
Section 14 1MRK 505 370-UEN D
Monitoring
378 Busbar protection REB670
Application manual