Power Monitoring - Measurement for Power availability and reliability

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 class S or class A Testing and measuring techniques – Power quality measurement methods	Power quality instruments (PQI-S or PQI-A) IEC 62586-1 Power quality instruments (PQI) + IEC 62586-2 Functional tests and uncertainty requirements

Fig. S7 – Examples of products compliant with IEC 61557-12, for Electrical Distribution Monitoring

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  Compact NSX circuit breaker equipped with a Micrologic trip unit, Schneider Electric

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  Masterpact MTZ circuit breaker equipped with a Micrologic trip unit, Schneider Electric

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  PowerLogic PM5000 series power meters, Schneider Electric

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  PowerLogic PM8000 series power meters, Schneider Electric