ODEN AT primary current injection test system

Primary injection testing is a method where high currents, typically in the hundreds to tens of thousands of amps, are injected into the test circuit to replicate actual currents the circuit will encounter during operation. Primary injection testing is most often used for testing current transformers (CTs) and low voltage circuit breakers. You can also use primary injection testing to test a complete circuit. 

For a test of the complete circuit, a high current is injected on the primary side of the current transformer. The test covers the entire chain, e.g., current transformer (CT), conductors, connection points, relay protection, and sometimes circuit breakers. You must take the system being tested out of service during primary injection testing. Testing is usually conducted in connection with commissioning.

For testing a CT’s ratio and polarity with primary injection, current is injected into the CT’s primary winding, and the resulting current is measured on the secondary circuit.

For testing a low voltage circuit breaker with primary injection, the current is injected through the circuit breaker, and the trip times are measured. The only way to verify that a direct-acting, low voltage circuit breaker operates properly is to inject a high current. Typical testing times are long time, short time, and instantaneous trip.

The two most common applications of the ODEN are primary current injection of low voltage circuit breakers and primary injection testing of current transformers (measuring ratio, polarity, and phase angle). In addition to these two applications, you can use the ODEN for heat run tests and ground grid integrity testing. Moreover, you can test automatic reclosers and sectionalisers with the ODEN; the instrument allows you to set custom operating limits, partial times, total times, and the number of operations before lockout.

The 480 V ODEN AT with three H units connected in parallel has a maximum output of 21 kA, given a suitable input source and minimal impedance. Megger manufactures a DDA3000 and DDA6000 if you need more current for your applications; the DDA instruments have a maximum current of 35 and 60 kA, respectively.

Yes, Megger manufactures a complete line of primary injection test sets. Two smaller units are the INGVAR, which can inject up to 5000 A, and the SPI, which can inject up to 2000 A. Both of these units are significantly smaller and lighter than the ODEN. The SPI has the option of paralleling multiple units together to provide additional current. 

The ODEN AT is an AC test set. If looking for a DC primary injection test set, the BALTO line of primary injection test sets from Megger is offered in testing currents from 4 kA to 40 kA.

No, the ODEN AT is a single-phase current injection unit.

Primary injection testing of CTs involves injecting current into the primary circuit of the CT and measuring the resulting current on the secondary side of the CT. The ODEN has a built-in ammeter that allows you to measure the CT turns ratio, phase angle, and polarity. An optional switchbox (BH-90130) enables you to connect to five individual secondary taps and easily switch between them for measurement (while de-energised). Secondary injection testing of CTs is often used because much smaller and lighter instruments are available for CT testing. Secondary injection measures the CT’s ratio, polarity, phase angle, and knee points by applying a voltage to the secondary side of the CT and measuring the resulting voltage on the primary side of the CT. Megger manufactures two CT test sets, the MRCT and MVCT. 

The primary application of the ODEN test set is testing low voltage circuit breakers (less than 1000 V). A circuit breaker analyser is needed to test medium and high voltage circuit breakers. Megger manufactures three different analyzers: the EGIL, TM1700, and TM1800, to meet all your circuit breaker testing applications.

There are many good reasons you might choose to go for a primary injection test, but one of the most convincing is that it’s a much more comprehensive test. To illustrate this, consider the simple example of a circuit breaker with an overcurrent trip relay that operates via a current transformer (CT).

You could inject your test current directly into the relay (secondary injection), showing you whether or not the relay was operating correctly. But it would tell you nothing about the CT and the connections between the CT and the relay. On the other hand, if you inject your test current into the primary circuit (primary injection), your results will confirm that the relay is operating correctly, that the CT is serviceable, and that the connections to it are present and correct.

Primary injection testing also has other valuable benefits. For example, it mimics the normal operating conditions of the equipment under test much more closely – the high test current will stress the equipment you’re testing just as it would be stressed in service. This can make a big difference to the test results.

There are several factors to consider in addition to the desired current when selecting the optimal ODEN configuration. The test circuit, which includes the test object and the cables, has a specific impedance requiring a minimum voltage to push the current through the circuit. Once the required voltage and current are determined, you must verify the load time to match the duty cycle of your testing parameters. 

An ODEN AT system consists of a control unit and one, two, or three current units. The system required depends on the type of testing you will perform and how much current, and in some cases voltage, will be required. The S (Standard) and X (Extra output) current units are identical, except that the X unit has an additional 30/60 V output. The extra voltage is used for higher impedance applications, e.g., low voltage circuit breakers rated in the ten to hundreds of amps, and higher compliance voltage applications, e.g., a recloser. When the highest available current output is needed, you can use an H (high current) unit. The current units can be configured in series or parallel to meet the required voltage or current demands. 

Note: you cannot mix and match current units. When adding additional ones, they must all be the same type.

In addition to the current unit type, three different configurations are available based on input voltage. If running on 50 Hz, there are 240 V and 400 V models. The 400 V version requires less input current and has a higher current capability for short-duration loading. In some cases, the 240 V version can provide a higher continuous current rating. If running on a 60 Hz system, a 480 V ODEN configuration is required. You should also note that the input current required depends directly on the output current and voltage source. You can use the following formula to determine the amount of input current required: (Output current) x (Open circuit voltage) / (Source voltage). 

In addition to selecting the proper ODEN configuration, you must select the appropriate cable set or bar. Megger has several cable sets and bars designed for parallel or series connections. The correct cable depends on the application, e.g., the required distance to the test object and the impedance of the test object. Multiple cables can be connected in parallel and twisted to help reduce impedance. However, connecting too many cables in parallel will make testing cumbersome by increasing the weight and making the connections difficult.

No, once you select a current unit type (S, X, or H), all other current units must be the same. You can connect in parallel or series to reach desired currents or voltages.

Yes, as long as the same current unit is used (S, X, or H), you can add more units later to meet the desired currents and voltages required.

When testing circuit breakers, you must de-energise them, but you do not need to uninstall them completely for testing. Megger has developed a high current probe, the HCP2000 (AA-90165), that allows the test technician to connect one side of the ODEN AT to the common bus and the other to the probe that can be inserted into the MCCB that is still connected to the cabinet. The HCP2000 provides a quick method of testing that drastically reduces overall testing time. 

The ODEN provides several methods to record the trip time. The most common one is to use the internal detection INT. This setting configures the ODEN to record the time the current stops flowing. In addition to the INT setting, you can select to detect the opening or closing of a contact or the application or interruption of voltage to determine the stop input. 

No, you manually control the current using a rotary dial and will need to test to the manufacturer’s specifications. The Megger Smart Primary Injection (SPI) test is available if you want a fully automated test set. However, it has a lower output current than the ODEN.