Support for the ODEN AT primary current injection test system
There are three possible causes for this:
- Check the miniature circuit breaker (F2); flip the switch to fully off, then back on.
- Overheating may have triggered the thermal protection. This will reset itself automatically after the ODEN AT cools down.
- There is an interrupted circuit.
- Check the connections to the object you are testing. If you are testing a breaker, check that it is closed.
- Check the connection between the control unit and the current unit.
- For series connection, check that a series connection cable is being used and is connected correctly.
Either the fuse (F1) has blown, which you can locate on the left side of the control unit, or there is no mains power. Check that you have plugged the mains cable in correctly and that mains voltage is present.
- Check if the stop condition is set to INT and F2 is off. Close F2.
- Check if the stop condition is set to INT and if the output circuit is open.
- Change the stop condition or close the output circuit.
- If the output current is just a small percentage of the measurement range, either increase the current, decrease INT-level, or use range or output with a lower current rating.
You need to calibrate the zero offset.
- Disconnect all current units from the control unit and make sure the input for ammeter 2 is open.
- Short the voltmeter input.
- Press the “SYSTEM” button.
- Simultaneously press the “ESC” and “ENTER” buttons and quickly turn the “CHANGE” knob clockwise until “CALIBRATION” appears; press “ENTER”.
- Choose “0 DC OFFSET” and press “ENTER”.
- Wait until the relays stop clicking, then press “ENTER” again.
- Press “ESC” twice to leave the calibration menu.
- Disconnect the cable on the shorted voltmeter.
There are several causes for this:
- The settings in the output block on the control panel need to be corrected.
- Select “HIGH I” if you are using the high current output.
- Select 0-30/60 V if you are using the low current output on a type X current.
- Select “PARALLEL” if you have the current units connected in parallel or only one current unit connected.
- Select “SERIES” if you have the current units connected in series.
- “SERIES” is selected in the “OUTPUT” block, and unused current units are connected to the control unit. Disconnect unused current units.
- “ODEN AT” is set for DC Measurement while AC is generated. (Fault will be approx. 10 %) - DC measurements shall only be activated if you have equipped the ODEN AT with a DC box. Select the proper setting for DC Measurement (submenu system).
- The test object has a higher impedance than expected. Increase the voltage applied from ODEN AT by connecting the current units in series or use the low current output if you have a type X current unit.
There is a high inrush current due to remanence. To remedy this:
- Disconnect all current units.
- Set the “FINE” knob in the “CURRENT ADJUST” block to 40 %.
- Press “ON+TIME” and turn the knob up to 100 % and then down to 0 %.
- Connect one current unit. No load should be connected to it.
- Press “ON+TIME” and set the “FINE” knob to 100 %.
- Slowly increase the “COARSE” adjustment to its maximum.
- Press “OFF” and set the “COARSE” and “FINE” adjustments to 0.
- Connect the next current unit without any load connected and repeat the procedure from step 5.
Note: If the problem appears at step 6, try loading some current from the unit. If the problem occurs at step 6 for the second and third current units, proceed with only the newly added current units connected.
You have selected 0-30/60 V in “OUTPUT” to measure current from the low current output, and there is no low-current output on the current unit. You should cancel the 0-30/60 V setting or connect a current unit with a low-current/high voltage output.
In “OUTPUT", you opted to measure current from the 0-30/60 V low current output when the switches on the current units are set differently. Make sure all the switches on the current units have the same settings.
Ensure that you have connected current units of the same type.
The instrument is not activated. Activate the instrument in the “V/A-METER” menu option if its indicator lamp is not lit.
The stop condition is met, but “AUTO OFF” is not activated. Press “RESET” if you want the generation time displayed.
The measurement time needs to be longer, the “HOLD" function cannot present any frozen readings, or there needs to be more time for a range to be selected automatically. Either increase the measurement time or select a fixed range.
The magnitudes of the input signals are too great for the fixed preset range, or the “AUTO” range does not have enough time to function properly for high speed cycles. (“OF” = Overflow). Repeat the measurement or select a fixed range.
No ratio can be calculated because the measurement current is 0. Generate current to resolve this.
The ammeter cannot present measured values for the generated current because different current units are connected, or the current unit is unknown because it is not calibrated. Verify that all current units are of the same type or, if needed, calibrate the current unit(s).
Increase the INT-level, or use a range or output with a higher current rating.
Some manufacturers equip circuit breakers with a ground fault sensor that detects a phase imbalance or current flowing through the ground circuit. The ground fault sensor must be disabled to perform the standard trip tests of long time, short time, and instantaneous trip tests.
Interpreting test results
Proper primary injection testing of low voltage circuit breakers (LVCB) will confirm that they trip at the correct times and can properly isolate a fault. A coordination study is performed, and parameters are set to minimise the amount of interruption to other equipment. The characteristics of the circuit breakers are presented in the form of trip curves, and each circuit breaker will have a unique trip curve published by the manufacturer. The trip curves will have bands, or limits, that show how long it takes for the circuit breaker to trip when a certain amount of current is applied; the current is typically presented in multiples of the rated current. As long as the circuit breaker trips within the specified band, it operates correctly. You may perform up to four primary injection test types to verify that the LVCB is working correctly: a long time test, short time test, instantaneous test, and earth/ground fault test. The long, short, and ground fault tests all have a delay component. In contrast, the instantaneous test trips the circuit breaker immediately.
The long time test is a test of the overload function and requires two settings. The first setting is the pickup, which determines the load current level that is tolerable before an overload condition occurs. The second setting is the time delay that determines how long the overload condition is acceptable. Systems are generally designed to handle overload conditions for a short time. Still, damage will occur if the overload persists for too long. You typically perform a long time test at 3 times the rated current.
The short time test is also an overload test with a pickup time like the long time test but has a shorter duration with a higher current. Typical currents are at 6 times the rated current. A short time setting on the breaker is used to allow high current loads for a short duration, for example, a motor starting.
The instantaneous trip conditions test the breaker under fault conditions. Therefore, there is no intentional time delay built in, and the breaker should trip within milliseconds. If the circuit breaker fails to trip and clear the fault, this may result in damage to equipment or personnel. Additionally, an upstream breaker may need to clear the fault, resulting in other electrical system components unrelated to the fault being shut down. An instantaneous trip is typically tested using 8 to 12 times the rated current.
An earth/ground fault trip in the circuit breaker occurs when higher-than-normal currents flow through the ground path. Like the long time and short time functions, the ground fault has both a pickup current and a delay time. Both can be adjusted to fit the coordination study. There is typically a maximum delay that is permitted from ground fault conditions.
Each test is performed separately for each phase. As long as the trip time falls between bands on the time-current curves, the circuit breaker is considered to be in working condition.
Note: the ground fault sensor must be disabled to test long, short, and instantaneous trips.
User guides and documents
Software and firmware updates
No. ODEN AT can only supply a single-phase current.
The output current of the ODEN AT is determined by two main factors: the available output voltage at the ODEN AT’s terminals and the impedance of the test circuit, which includes the current conductors and the object under test. Even if ODEN AT can withstand a higher current, the impedance in the circuit can be the limiting factor. Ohm’s law (I = U/Z) is always valid.
There are 5 common reasons for this:
The mains input voltage is too low
- Check to make sure the input voltage is at the nominal voltage to which your ODEN is rated. Although the ODEN can be powered at 14 % less than rated voltage, this will also reduce the output voltage and output current by 14 %.
- The mains input voltage can be weak and drop when loaded by the ODEN AT. Therefore, in addition to checking the voltage source under float conditions, you should also check the input voltage under load.
The impedance in the test circuit is too high
- Verify that the cables have enough cross-sectional area for the output voltage and currents required. The impedance of the standard cable sets provided by Megger are published in the manual.
- Use more than one cable in parallel.
- Use shorter cables.
- If using more than one cable, twist the cables in pairs to reduce impedance.
- If cables cannot be twisted, keep the cables with the same current direction away from each other as much as possible and avoid any loops or ‘windows.’
- Use copper bars as opposed to cables.
The ODEN AT is not set correctly
- Verify that the ODEN AT is set to the correct setting of “Serial” or “Parallel” on the control panel according to the physical connection of the current units and that the output is also set to “HIGH I”.
- If using the X model at 30 V or 60 V, verify that the switch on the current unit is in the correct position and output setting on the ODEN control panel is set to “0-30 V/60V”.
The output capability of your equipment is insufficient for your application.
In the manual, there are curves representing the output voltage versus current for each configuration. If the output voltage is lower than the current x, the impedance of the conductors and the test object, the configuration won’t be able to perform the test. Check if adding additional current boxes will provide the necessary current at the required voltage.
The equipment is faulty
To test if the ODEN AT is operating correctly:
- Disconnect any loads from ODEN AT.
- Set the coarse and fine current settings to maximum.
- Measure the output voltage from ODEN AT.
- The output voltage should conform with the no-load (idle) voltage specified in the manual as long as the input voltage is at the nominal voltage specified.
- If the output voltage is considerably lower than the specifications, you will need to send the unit for repair.
No. You can only use one ODEN AT at a time. Connecting multiple units can damage the ODEN AT systems due to back feeding.
When units are connected in parallel, you must take care that one unit does not supply the major part of the current. Otherwise, the unit's thermal protection can trip. Ensure that the cable impedance between each current unit and test object is equal (same number of cables and same length). If the number of cables used cannot be evenly divided by the number of current units, make parallel connections between the terminals of the current units. Contact must be good, preferably using bars. Connect the cable set between the bars and the test object.
ODEN AT is operable down to 14 % under nominal input voltage. When operating at a voltage lower than the nominal input voltage, the output voltage available to push current through the test circuit and the current available will go down by the same amount.
Distortion caused by the ODEN AT itself is a few percent at most. Total distortion also depends on the mains input curve form. Sometimes, the test object is a source of distortion, for instance, when the impedance changes during the cycle.