Power Monitoring - Measurement for Power availability and reliability

From Electrical Installation Guide
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In order to operate an electrical installation, it is recommended that measurement of the main characteristics of the supply such as voltage, current, frequency, and/or active power are provided as a minimum.

Some electrical phenomena can have an impact on both installation assets and operations within a plant (e.g. unbalance can reduce the life time of motors, dips can stop a process, etc.)

The following table describes the main problems that can occur in a network (see Table 3 of IEC TR 63213):

Fig. S5 – Main problems that can occur in an electrical network, and their potential consequences
Electrical quantities to measure Symbol Benefits of measurement
Current I, IN Detect overheating or conditions that may lead to nuisance trips.
Voltage U, V Detect abnormal supply conditions of sensitive loads (e.g. motors) leading to premature failure.
Frequency f Detect abnormal speed of rotating machines.
Individual voltage harmonics Uh, THDu Monitor non-positive-sequence harmonics causing overheating of components (motors, transformers, cables, capacitors…), and motor shaft vibrations, resulting in premature failure.
Individual current harmonics Ih, THDi
Voltage unbalance Unb Monitor non-positive-sequence voltage causing motors and generators to overheat and fail prematurely.
Current unbalance Inb
Voltage dips, voltage interruptions Udip, Uint Detect degradation of supply quality before it leads to process stoppages with financial impact.
Voltage swells Uswl
Power demand or Current demand P Optimize the load distribution, determine where new loads may be placed, or which feeder needs to be upgraded to serve the planned capacity.
Load profiles LP Detect abnormal load profiles
Reactive power Q Detect abnormal reactive power consumption
Apparent power S Detect abnormal apparent power consumption
NOTE In general, it is useful to detects drifts, to log measurements and possibly to alarm if a measurement is out of some specified limits.

The main standards are specified below (see Table 4 and Table 5 of IEC TR 63213):

Fig. S6 – Standards for power availability and reliability
Application assessment standards or rules Method standards Usual product standards
Electrical distribution monitoring, asset management, facility planning included in IEC 61557-12 PMD (Power Metering and Monitoring Devices)

IEC 61557-12
Power metering and monitoring devices (PMD)

included in IEC 60051 series Analog electrical measuring instruments

IEC 60051 series
Direct acting indicating analogue electrical measuring instruments

IEC TR 63191

Demand side power quality

included in IEC 61557-12 PMD (Power Metering and Monitoring Devices)

IEC 61557-12
Power metering and monitoring devices (PMD)

IEC 61000-4-30[a] class S or class A
Testing and measuring techniques – Power quality measurement methods
Power quality instruments (PQI-S[b] or PQI-A)

IEC 62586-1
Power quality instruments (PQI)
IEC 62586-2[a]
Functional tests and uncertainty requirements

  1. ^ 1 2 Compliance with IEC 62586-2 means compliance with IEC 61000-4-30.
  2. ^ Usually PQI-S are used for this purpose.