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Section 8
1MAC050144-MB C
Measurement functions
586
615 series ANSI
Technical Manual
PQSS is used for measuring short-duration voltage variations in distribution networks. The
power quality is evaluated in the voltage waveform by measuring the voltage swells, dips
and interruptions.
Figure 318:
Duration and voltage magnitude limits for swell, dip and interruption
measurement
Voltage dips disturb the sensitive equipment such as computers connected to the power
system and may result in the failure of the equipment. Voltage dips are typically caused by
faults occurring in the power distribution system. Typical reasons for the faults are
lightning strikes and tree contacts. In addition to fault situations, the switching of heavy
loads and starting of large motors also cause dips.
Voltage swells cause extra stress for the network components and the devices connected
to the power system. Voltage swells are typically caused by the ground faults that occur in
the power distribution system.
Voltage interruptions are typically associated with the switchgear operation related to the
occurrence and termination of short circuits. The operation of a circuit breaker disconnects
a part of the system from the source of energy. In the case of overhead networks, automatic
reclosing sequences are often applied to the circuit breakers that interrupt fault currents.
All these actions result in a sudden reduction of voltages on all voltage phases.
Due to the nature of voltage variations, the power quality standards do not specify any
acceptance limits. There are only indicative values for, for example, voltage dips in the
European standard EN 50160. However, the power quality standards like the international
standard IEC 61000-4-30 specify that the voltage variation event is characterized by its
duration and magnitude. Furthermore, IEEE Std 1159-1995 gives the recommended
practice for monitoring the electric power quality.
Voltage variation measurement can be done to the phase-to-ground and phase-to-phase
voltages. The power quality standards do not specify whether the measurement should be
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Summary of Contents for 615 Series ANSI
Page 1: ...Relion Protection and Control 615 series ANSI Technical Manual ...
Page 2: ......
Page 29: ...1MAC050144 MB C Section 615 series ANSI 22 Technical Manual ...
Page 389: ...Section 4 1MAC050144 MB C Protection functions 382 615 series ANSI Technical Manual ...
Page 485: ...Section 6 1MAC050144 MB C Supervision functions 478 615 series ANSI Technical Manual ...
Page 635: ...Section 10 1MAC050144 MB C Other functions 628 615 series ANSI Technical Manual ...
Page 711: ...Section 16 1MAC050144 MB C Glossary 704 615 series ANSI Technical Manual ...
Page 712: ......