Schneider Electric PM820, PM870 Evaluations During Abnormal Operation, Supply Voltage Unbalance

63230-500-225A2	PowerLogicTM Series 800 Power Meter
3/2011	Appendix D—Advanced Power Quality Evaluations

Supply Voltage Unbalance

EN50160 states that, under normal operating conditions, during each period of one week, 95% of the ten minute mean rms values of the negative phase sequence component of the supply voltage shall be within the range 0–2% of the positive phase sequence component.

Harmonic Voltage

EN50160 states that, under normal operating conditions, during each period of one week, 95% of the ten minute mean rms values of each individual harmonic voltage shall be less than or equal to the value given in Table D–7. Additionally, the THD of the supply voltage shall be less than 8%.

Table D–7: Values of individual harmonic voltages at the supply terminals for orders up to 25 in % of nominal voltage

	Odd Harmonics			Even Harmonics
Not Multiples of 3		Multiples of 3
Order h	Relative	Order h	Relative	Order h	Relative
	Voltage		Voltage		Voltage
5	6%	3	5%	2	2%
7	5%	9	1.5%	4	1%
11	3.5%	15	0.5%	6...24	0.5%
13	3%	21	0.5%
17	2%
19	1.5%
23	1.5%
25

NOTE: No values are given for harmonics of order higher than 25, as they are usually small, but largely unpredictable because of resonance effects.

Evaluations During Abnormal Operation

Count of Magnitude of Rapid Voltage Changes

The standard does not specify the rate of change of the voltage for this evaluation. For this evaluation, the PM850 and the PM870 counts a change of ≥ 5% nominal and ≤ 10% nominal from one one-second meter cycle to the next one-second meter cycle. It counts rapid voltage decreases and increases separately. The interval for accumulation of these events is one week.

You can configure the number of allowable events per week in register 3917. (Default = -32768 = Pass/Fail evaluation disabled.)

Detection and Classification of Supply Voltage Dips

According to EN50160, voltage dips are generally caused by faults in installations or the electrical utility distribution system. The faults are unpredictable and frequency varies depending on the type of power system and where events are monitored.

Under normal operating conditions, the number of voltage dips expected may be anywhere from less than a hundred to nearly a thousand. The majority of voltage dips last less than one second with a depth less than 60%. However, voltage dips of greater depth and duration can occasionally occur. In some regions, voltage dips with depths between 10% and 15% of the nominal voltage are common because of the switching of loads at a customer’s installation.

Supply voltage dips are under-voltage events that last from 10 ms to 1 minute. Magnitudes are the minimum rms values during the event. Disturbance alarms are used to detect these events in the PM870. Standard speed under-voltage alarms are used to detect these events in the PM850. The standard does not specifically address how to classify supply voltage dips or how many are allowable. Table D–8shows how the PM850 and the PM870 detect and classify the dips for each phase voltage.

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