Function: Scope - Phasor
The Scope function provides a clear view of current and voltage
waveform shapes. Voltage waveforms in particular should be smooth
and sinusoidal. If you see voltage distortion on the waveform,
check the harmonics display. The RMS voltages and frequency should
be close to their nominal values.
Waveform and Phasor display are also a useful way to verify that
voltage leads and current clamps are connected correctly. In the
vector diagram, ensure that the phase voltages and currents L1
(A), L2 (B), and L3 (C) appear in sequence when observing them in
clockwise direction.
To access, push the Scope button. Then, push F3
for Phasor.
Function: V-Amps-HZ
Voltage and frequency should be close to the applicable nominal
values: 120 V, 230 V, 480 V, 60 Hz, or 50 Hz. For example: Check
the voltages and currents in the table to see if power applied to
a three phase induction motor is in balance. Each of the phase
voltages should not differ more than 1 % from the average of the
three. Current unbalance should not exceed 10 %. Voltage unbalance
causes high unbalanced currents in stator windings, resulting in
overheating and reduced motor life. If unbalance is too high, use
other measuring modes to further analyze the power system. A Crest
Factor close to 2.0 indicates high distortion. A pure sine wave
would have a crest factor of 1.414. Anything higher is a result of
distortion.
To access, push the Menu button and select Volt/Amps/Hertz.
Function: Dips & Swells
Dips (Sags) and Swells may indicate a weak power distribution
system. In a weak system, voltage will change considerably when a
big motor or a welding machine is switched on or off. This may
cause lights to flicker or even show visible dimming. It can also
cause reset and data loss in computer systems and process
controllers. By monitoring the voltage and current trend at the
power service entrance, you can determine if the cause of the
voltage dip is inside or outside the building. The cause is inside
the building (downstream) when voltage drops while current rises;
it is outside (upstream) when both voltage and current drop.
To measure dips and swells, push the Menu button and
select Dips & Swells.
Function: Harmonics
The harmonic number indicates the harmonic frequency: the first
harmonic is the fundamental frequency (60 or 50 Hz), the second
harmonic is the component with two times the fundamental frequency
(120 or 100 Hz), and so on. The harmonics sequence can be positive
(+), zero (0), or negative (-).
Harmonic Frequencies and Sequences
| Order |
1st |
2nd |
3rd |
4th |
5th |
6th |
| Frequency |
60 Hz
50 Hz |
120 Hz
110 Hz |
180 Hz
150 Hz |
240 Hz
200 Hz |
300 Hz
250 Hz |
360 Hz
300 Hz |
| Sequence |
+ |
- |
0 |
+ |
- |
0 |
As you can see, the sequence is + - 0 + - ….
Positive sequence harmonics try to make a motor run faster than
the fundamental; negative sequence harmonics try to make the motor
run slower than the fundamental. In both cases the motor loses
torque and heats up. Harmonics can also cause transformers to
overheat. Even harmonics will disappear if waveforms are
symmetrical, i.e. as equally positive and negative. Zero sequence
current harmonics add in Neutral conductors. This can cause these
conductors to overheat.
Current distortion is expected in a system with non-linear
loads like DC power supplies. When the current distortion starts
to cause voltage distortion (THD) of more than 5 %, this signals a
potential problem.
K-factor indicates the amount of harmonic currents and can
help in selecting transformers. Use K-factor along with apparent
power (kVA) to select a replacement transformer to handle
non-linear, harmonics-rich loads. K-factor is a mathematically
derived value that takes into account the effects of harmonics on
transformer loading and losses. A K-rated transformer is one that
is specifically designed to handle the effects associated with
higher levels of harmonics.
To measure Harmonics, push the Menu button and select Harmonics.
To measure K-factor, select Power & Energy.
Function: Power & Energy
Power mode can be used to record apparent power (kVA) of a
transformer over several hours. Look at the Trend and watch for
periods or peaks that exceed the rating of the transformer. To
mitigate the overload, transfer loads to other transformers,
stagger the timing of loads, or install a larger transformer.
Interpretation of Power Factor when measured at a device: PF = 0
to 1: not all supplied power is consumed, a certain amount of
reactive power is present. Current leads (capacitive load) or lags
(inductive load). PF = 1: all supplied power is consumed by the
device. Voltage and current are in phase. PF = -1: device
generates power. Current and voltage are in phase. PF = -1 to 0:
device is generating power. Current leads or lags.
If you see negative power or power factor readings and you are
connected to a load, check to make sure the arrows on your current
clamps are pointing towards the load. Reactive power (VAR) is most
often due to inductive loads such as motors, inductors, and
transformers. Installing correction capacitors can correct for
inductive VARs. Check with a qualified engineer before adding
PF-correction capacitors, especially if your system is already
carrying current harmonics.
To access power mode, push the Menu button and select Power
& Energy.
Function: Flicker
Flicker refers to rapid change (to fast to see) in overhead
lightning resulting in human visual annoyance, headaches and
eye-strain. From the Flicker function, use the PF5
flicker trend and half-cycle voltage or current trends to find the
source of flicker. Press function key F1 to assign the
arrow keys to flicker, voltage, and current trends. Use a 10
minute (PST) measuring period to eliminate the influence of random
voltage variations and detect interference from a single source
with a long working cycle, such as household appliances and heat
pumps. A two hour measuring period (PLT) is useful when facing
more than one interference source with irregular working cycles
and for equipment such as welding machines and rolling mills.
To access, push the Menu button and select Flicker.
Function: Unbalance
The voltages and currents in the Unbalance table can be used to
check if applied power is in balance; for example, on a three
phase induction motor. Voltage unbalance causes high unbalanced
currents in stator windings, resulting in overheating and reduced
motor life. Each of the phase voltages should not differ more than
1 % from the average of the three. Current unbalance should not
exceed 10 %. If unbalance is too high, use other measuring modes
to further analyze the power system. Each phase voltage or current
can be split into three components: positive sequence, negative
sequence, and zero sequence. The positive sequence is the normal
component present in balanced 3- phase systems. The negative
sequence results from unbalanced phase-to-phase currents and
voltages. For instance, this component causes a 'braking' effect
in three phase motors, resulting in overheating and life
reduction. Zero sequence may appear in an unbalanced load in 4
wire power systems and represents the current in the N (Neutral)
wire. Unbalance exceeding 2 % is considered too high.
To access, push the Menu button and select Unbalance.
Function: Transients
Transients in a power distribution system can cause many types of
equipment to malfunction. Equipment subjected to repeated
transients can eventually fail. Events occur intermittently,
making it necessary to monitor the system for a period of time to
locate them. Look for voltage transients when electronic power
supplies are failing repeatedly or if computers reset
spontaneously. To isolate the fault location, use the Transients
function and monitor at several points in the distribution. As you
work your way down the line, eliminate circuits that don't show
events and follow the circuits that show the event in sharper
detail. The sharper the event, the closer you are to the load
causing the problem. Three phase monitoring also allows you to
determine if it is a single, dual or three phase load causing the
problem, further reducing the number of culprits.
To access, push the Menu button and select Transients.
Function: Inrush Currents
Inrush is the large spike most commonly caused by a motor load
coming on-line. As it first energizes, the motor utilizes a higher
amount of current than when runs at a constant speed. This large
current draw frequently causes a large enough voltage dip to send
other equipment off-line or cause the lights to blink. The Inrush
function allows you to capture the inrush magnitude along with the
length of time it takes the motor to come up to speed: Start
recording, watch for inrush events and check the peak currents and
their duration. Use the Cursor for readout of momentary
values. Check if fuses, circuit breakers, and conductors in the
power distribution system can withstand the inrush current during
this period. If the inrush exceeds the breaker setting, it will
trip. Measuring inrush current can help set appropriate breaker
trip levels. Also check whether phase voltages stay stable as a
large inrush can cause a voltage sag. Since the 434 Analyzer
simultaneously captures inrush current and voltage trends, you can
use this measurement to check voltage stability as large loads
come on line.
To access, push the Menu button and select Inrush.
Function: Monitor
Monitor is a fully adjustable threshold driven feature. The
Monitor screen displays a bar chart as a Go-No-Go against the
thresholds. Drill down into the event to locate details for
further investigation. By default, the meter is programmed to use
the EN50160 power standard. These values are fully adjustable and
can be set as desired. Use the Monitor function to quickly
determine if a manufacturer's specification is being met for a
particular load or for doing regular power audits against
corporate defined limits. EN50160 is designed more for the
incoming utility and not necessarily a guarantee that all loads
will function within this standard.
To access, push the Monitor button.
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