Schneider Electric PM5100 manual Energy pulsing considerations, VT and CT considerations

PowerLogic™ PM5100 series user guide Chapter 10—Verifying accuracy

Where:

•EM = energy measured by the meter under test

•ES = energy measured by the reference device or energy standard.

NOTE: If accuracy verification reveals inaccuracies in your meter, they may be caused by typical sources of test errors. If there are no sources of test errors present, please contact your local Schneider Electric representative.

Energy pulsing considerations

The meter’s alarm / energy LED and digital outputs are capable of energy pulsing within the following limits:

Energy pulsing limits

Description	Alarm / energy LED	Digital output
Maximum pulse frequency	50 Hz	25 Hz
Minimum pulse constant	1 pulse per k_h
Maximum pulse constant	9,999,999 pulses per k_h

The pulse rate depends on the voltage, current and PF of the input signal source, the number of phases, and the VT and CT ratios.

If Ptot is the instantaneous power (in kW) and K is the pulse constant (in pulses per k_h), then the pulse period is:

Pulse period (in seconds) =	3600	=	1
	K-------------------× Ptot		Pulse--------------------------------------------------frequency (Hz)

VT and CT considerations

The test points are always taken at the secondary side, regardless of whether VTs or CTs are used. Ptot is derived from the values of the voltage and current inputs at the secondary side, and takes into account the VT and CT ratios.

If VTs and CTs are used, you must include their primary and secondary ratings in the equation. For example, in a balanced 3-phase Wye system with VTs and CTs:

Ptot = 3 × VLN ×	---------------------------------VT primary	× I ×	----------------------------------CT primary	× PF ×	------------------1 kW
	VT secondary		CT secondary		1000 W

Total power limit for alarm / energy LED

Given the maximum pulse constant (Kmax) you can enter is 9,999,999 pulses per kWh, and the maximum pulse frequency for the alarm / energy LED is 83 Hz, the maximum total power (Max Ptot) the alarm / energy LED’s energy pulsing circuitry can handle is

29.88 Watts:

3600 × (Maximum pulse frequency) 3600 × 83

Maximum Ptot = -------------------------------------------------------------------------------------- = ----------------------- = 0.02988 kW

Kmax9,999,999

Total power limit for digital output

Given the maximum pulse constant (Kmax) you can enter is 9,999,999 pulses per kWh, and the maximum pulse frequency for the digital output is 25 Hz, the maximum total power (Max Ptot) the digital input’s energy pulsing circuitry can handle is 9 Watts:

© 2014 Schneider Electric All Rights Reserved 75