ABB Relion 670 Series Applications Manual page 535

1MRK 511 401-UEN Rev. K
18.12.4.3 Application example for OHL
Additionally, the PTRSTHR function can be used to monitor faults on OHL. In such cases, the
OHL current and voltage shall be connected to W1 inputs. In case of one-and-a-half breaker
configuration, W1 and W2 currents shall be used.
For such applications, the PTRSTHR function can be triggered either by the set phase current
level or externally by the START or TRIP signal from the distance protection. As a result, a
summary list that provides an overview about all through faults seen by the IED will be
available on the local HMI.
18.13 Current harmonic monitoring CHMMHAI
18.13.1 Identification
Function description
Current harmonic monitoring
18.13.2 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:
• Poor power quality
• Increase in operational cost due to less productivity
• Damage to sensitive equipment in nearby facilities.
Maintaining high power quality in traction system is very complex. The presence of non-linear
loads reduces the capability of the existing harmonic mitigation techniques. However, it is
essential to minimize the issues like harmonics, voltage sags and flicker to protect sensitive
equipment affected by the aforementioned issues produced by traction systems.
Bay control REC670
Application manual
IEC 61850
identification
CHMMHAI
© Copyright 2017 Hitachi Power Grids. All rights reserved
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IEC 60617 ANSI/IEEE C37.2
identification device number
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Section 18
Monitoring
529