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.