View source for Power Monitoring - Measurement for Power availability and reliability

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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):

{{tb-start|id=Tab1451|num=S5|title=Main problems that can occur in an electrical network, and their potential consequences|cols=5}}
{| class="wikitable"
|-
!Electrical quantities to measure
!Symbol
!Benefits of measurement
|-
|Current
|''I, I<sub>N</sub>''
|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
|''U<sub>h</sub>, THD<sub>u</sub>''
| rowspan="2" |Monitor non-positive-sequence harmonics causing overheating of components (motors, transformers, cables, capacitors…), and motor shaft vibrations, resulting in premature failure.
|-
|Individual current harmonics
|''I<sub>h</sub>, THD<sub>i</sub>''
|-
|Voltage unbalance
|''U<sub>nb</sub>''
| rowspan="2" |Monitor non-positive-sequence voltage causing motors and generators to overheat and fail prematurely.
|-
|Current unbalance
|''I<sub>nb</sub>''
|-
|Voltage dips, voltage interruptions
|''U<sub>dip</sub>, U<sub>int</sub>''
| rowspan="2" |Detect degradation of supply quality before it leads to process stoppages with financial impact.
|-
|Voltage swells
|''U<sub>swl</sub>''
|-
|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
|-
| colspan="3" |'''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):

{{tb-start|id=Tab1452|num=S6|title=Standards for power availability and reliability|cols=5}}
{| class="wikitable"
|-
!Application assessment standards or rules
!Method standards
!Usual product standards
|-
| rowspan="2" |Electrical distribution monitoring, asset management, facility planning
|included in IEC 61557-12
|<u>'''PMD (Power Metering and Monitoring Devices)'''</u>

'''IEC 61557-12'''<br>Power metering and monitoring devices (PMD)
|-
|included in IEC 60051 series
|'''<u>Analog electrical measuring instruments</u>'''

'''IEC 60051 series'''<br>Direct acting indicating analogue electrical measuring instruments
|-
| rowspan="2" |'''IEC TR 63191'''

Demand side power quality
|included in IEC 61557-12
|<u>'''PMD (Power Metering and Monitoring Devices)'''</u>

'''IEC 61557-12'''<br>Power metering and monitoring devices (PMD)
|-
|'''IEC 61000-4-30{{tn|A}}''' class S or class A<br>Testing and measuring techniques – Power quality measurement methods
|'''<u>Power quality instruments (PQI-S{{tn|B}} or PQI-A)</u>'''

'''IEC 62586-1'''<br>Power quality instruments (PQI)<br>
+<br>
'''IEC 62586-2{{tn|A}}'''<br>Functional tests and uncertainty requirements
|-
|}
{{Tb-notes|A=Compliance with IEC 62586-2 means compliance with IEC 61000-4-30.|B=Usually PQI-S are used for this purpose.}}

{{Gallery|S7|Examples of products compliant with IEC 61557-12, for Electrical Distribution Monitoring||
|PB117053.jpg||Compact NSX circuit breaker equipped with a Micrologic trip unit, Schneider Electric
|PB115935_32.jpg||Masterpact MTZ circuit breaker equipped with a Micrologic trip unit, Schneider Electric
|PB117054.jpg||PowerLogic PM5000 series power meters, Schneider Electric
|PB117055.jpg||PowerLogic PM8000 series power meters, Schneider Electric
}}