PA-9 Series

Application Guide

TRIPPING BREAKERS

Tripping Breakers can be a nuisance problem that can cause

sags, power interruptions and industries to go off line. Current

swells, voltage swells or transients are the most common cause of

tripping breakers. First or second generation solid-state tripping

devices on low-voltage circuit breakers use to respond to peak

currents. Since about 1978, these devices have been responding to

RMS current values. Therefore, earlier models may cause nuisance

tripping in circuits carrying harmonic currents.

Common Causes of current swells can include in-rush current

or load switching.

Common Causes of voltage swells can include load switching or

utility faults.

Common Causes of transients can include lightning strikes or

capacitor bank switching.

Below is an example of an RMS Current and Voltage swell.

PA-9 Configuration

Feature Status Notes

Enable Power Calculations Enable (Select correct configuration)

Enable RMS Recording Enable

MIN, RMS and MAX MIN, RMS and MAX

Clock Hour Orientation Enabled

Enable Flicker Recording Disabled

Hysteresis 2%

Sags Enabled

Sag Limit See Below

Swells Enabled

Swell Limit See Below

Sub-cycle Enabled

Sub-Cycle Limit See Below

THD Limit Enable Voltage Only

THD Limit See below

Enable Waveform Capture Enabled

Waveform Trigger Event Trigger

Pre-Triggers 2

This configuration is designed

to capture out of limit events.

It focuses on sub-cycle, sag,

swell and THD events.

In this configuration the

waveform capture is set to

Exceedance. This will allow

the unit to capture a

waveform every time there is

an out of limit event. By

analyzing the waveforms

associated with transients one

can determine whether the

transient is due to lightning or

capacitor switching.

Also note that waveform limit

is enabled and set to 200. This

will limit the number of

waveforms captured to 200.

This is done so that the unit’s

memory does not fill

PA-9

Application Guide

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ISO STATEMENT

Registered to ISO 9001:1994 Reg no. Q 09250

Registered to ISO 14001 Reg no. EMS 61597

PA9_18_AG_En_V02

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Megger is a registered trademark

Feature Status Notes

Post Triggers 5 - 10

Waveform Limit Enabled

Expected Number of Events 300

Memory Mode Stop When Full

Default Frequency 50 or 60Hz as Required

Enable Frequency Recording Enabled

MIN, AVG, MAX AVG

prematurely in the case of a

large amount of events in a

small period of time.

IEEE Recommendations: For a 120V / 60Hz Load

per IEEE1159.

Sag Limit = 108V (10% of Nominal)

Voltage Swell Limit = 126V (5% of Nominal)

Current Swell Limit = Dependant on Breaker Trip point

Sub-cycle = 200V (Approx 2 times Phase to Neutral)

Voltage Imbalance = +/- 2%

Voltage THD = 20% for small customers, 5% for large customers

Frequency Limit = +/- 1Hz

European Recommendations: For a 230V / 50Hz Load

per EN50160.

Sag Limit = 207V (10% of Nominal)

Swell Limit = 253V (10% of Nominal)

Current Swell Limit = Dependant on Breaker Trip point

Sub-cycle = None Provided

Voltage Imbalance = +/-2%

Voltage THD Limit = 8%

Frequency Limit = +/- 1Hz

NOTE: If equipment is tripping out due to over voltages it may

be advantageous to set the sub-cycle limit to approximately 25% of

nominal. (Often sensitive electronic equipment will trip out at

transient over-voltages of no more than 115-120% of nominal.)

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