ABB Remote I/O RIO600 Installation And Commissioning Manual page 94

Section 6
Commissioning
86
Distortion measurement
The distortion measurement module measures harmonics up to the 8
total demand distortion (TDD) is calculated from the measured harmonic components
with the formula.
L
2
I
∑
k
k 2
=
TDD
=
I
N
GUID-FC55400F-5773-492C-88EF-123A07556471 V1 EN
I Nominal current amplitude
N
The nominal current amplitude is available from the Nominal Current
setting under the SIM8F operation parameter.
Demand calculation
The demand value for TDD is calculated separately for each phase. If any of the
calculated total demand distortion values is above the set TDD alarm limit value, the
HiATdd output is activated.
Application
The power quality standards are defined through the characteristics of the supply
voltage. The key characteristics describing power quality are transients, short-
duration and long-duration voltage variations, unbalance and waveform distortions.
Power quality is a customer-driven issue and any power problem concerning voltage
or current that results in a failure or misoperation of customer equipment is a power
quality problem.
Harmonic distortion in a power system is caused by nonlinear devices. Electronic
power converter loads constitute the most important class of nonlinear loads in a
power system. The switch mode power supplies in a number of single-phase
electronic equipment, such as personal computers, printers and copiers, have very
high third-harmonic content in the current. Three-phase electronic power converters,
that is, dc/ac drives, do not generate third-harmonic currents but they can be
significant sources of harmonics.
Power quality monitoring is an essential service that utilities can provide for their
industrial and key customers. Not only can a monitoring system provide information
about system disturbances and their possible causes, it can also detect problem
conditions throughout the system before they cause customer complaints, equipment
malfunctions and even equipment damage or failure. Power quality problems are not
limited to the utility side of the system. In fact, the majority of power quality problems
are localized within customer facilities. Thus, power quality monitoring is not only an
effective customer service strategy but also a way to protect a utility's reputation for
quality power and service.
1MRS757488 H
th
harmonic. The
(Equation 5)
Installation and Commissioning Manual
RIO600