The OMICRON CPC 100 is a portable primary injection system that delivers up to 800 A AC, 400 A DC and 2 kV, with variable frequency from 15 to 400 Hz. On power transformers it covers ratio, winding resistance, demagnetization, short-circuit impedance and, with the CP TD accessory, capacitance and dissipation factor. It is for measuring; deciding what to test and how to interpret it remains the job of the test plan.
What the CPC 100 is and what it is used for
The OMICRON CPC 100 is a portable primary injection system of about 29 kg, which the manufacturer describes as a multifunction solution for substation commissioning and maintenance. The idea is to bring together in a single box what used to require several instruments: a current source, a voltage source and the measurement inputs to read the result.
It is used to test power transformers, instrument transformers, rotating machines, cables, circuit breakers and grounding systems. In this guide we limit ourselves to power transformers. Current and voltage transformers are covered in a separate guide; to understand the transformer itself, see power transformer. To go further: transformer turns ratio out of tolerance.
What it delivers and what it measures
These are the capabilities the manufacturer declares on its data sheet:
| Feature | Manufacturer data |
|---|---|
| AC current | up to 800 A AC (2 kA with the CP CB2 booster) |
| DC current | up to 400 A DC |
| AC voltage | up to 2 kV (12 to 15 kV with the CP TD12/15 accessories) |
| Power | up to 5 kVA |
| Frequency | 15 to 400 Hz |
| Auxiliary output | 6 A / 130 V AC and 6 A DC |
| Measurement inputs | 10 A AC/DC, 300 V AC, 3 V AC low level and 10 V DC |
Variable frequency is one of its most useful features: it allows measuring under conditions other than power frequency; the manufacturer presents it together with strong interference suppression, which matters in an energized substation. The 6 A DC output is intended for resistance measurements with simple test leads and, according to the manufacturer, also for demagnetizing power transformers, including large ones. The 400 A DC output is intended for the resistance of very large transformers and for ground grid integrity.
Which transformer tests it covers
The manufacturer’s data sheet places the instrument, with its accessories, in these power transformer tests:
- Transformation ratio and polarity. The 300 V AC input complements the 2 kV output to measure ratio from the low-voltage side. Phase displacement and vector group are deduced from the same test; the fundamentals are in ratio, polarity and vector group test.
- Winding resistance. With the DC current outputs, which serve to detect poor contacts in windings, terminals and the tap changer. See winding resistance test.
- Demagnetization. After measuring resistance with direct current, the core is left with residual magnetism that can alter later measurements and the energization. The 6 A DC output is used to bring it to a known state.
- Short-circuit impedance and leakage reactance. With the 6 A / 130 V AC output. It is the basis of the short-circuit (Z) test, useful for detecting winding deformation after a short-circuit event or transport.
- Excitation current. With the CP TD accessory, which the manufacturer indicates for tan delta and excitation current measurements; the reading criteria are covered in the no-load excitation test guide.
- Capacitance and dissipation factor (tan δ). With the CP TD accessory, which combines a high-voltage source and a measuring unit. It is the test described in power factor and tan delta, applied to windings and bushings.
The CP SB1 accessory is a switching box that the manufacturer presents for automatic three-phase testing of power transformers. The Primary Test Manager (PTM) software guides the work from the plan to the report.
Where it fits and where it does not
The CPC 100 is designed for transformers from medium voltage up to high and extra-high voltage, both new and in service. Its value is in its versatility: the same instrument and the same operator cover several tests, which reduces transport and setup time when the visit is short.
There are limits that do not depend on the instrument. On a large transformer, the resistance reading takes time to settle because of the winding inductance; that is why there are systems that measure all three phases at once with a single wiring, such as the manufacturer’s TESTRANO 600. Also, no electrical test replaces dissolved gas analysis or frequency response analysis when the question is a different one: the instrument is chosen by the question, not the other way around.
Interpreting is the hard part
A ratio or resistance value says nothing on its own. It is compared with the nameplate, the factory protocol, the other phases and earlier measurements. The reference standards for these tests are IEC 60076-1 and IEEE C57.12.90 for the tests, and IEEE C57.152 as the field-testing guide for liquid-filled transformers; the guide power transformer commissioning shows how they are chained together. The numerical acceptance criteria depend on the standard applicable to the equipment and on the factory protocol, and they are set by the test plan.
Transformer testing on request
The CPC 100 and the CP TD1 accessory are frequently used in our tests. Need this test? We do it for you: depending on your case we recommend the right test and equipment and include it in the quotation. You get the test your case really needs, without paying for extra ones.
See the scope in power transformer testing and request your quotation through the form. Field tests are done in Colombia, or elsewhere on request.
Related guides
- Primary substation equipment testing
- Power transformer
- How to quote testing for a power transformer
- Insulation resistance and polarization index test
- Tap changer dynamic resistance test
- OMICRON TESTRANO 600: three-phase transformer testing
- OMICRON CP TD1: power factor and tan delta
- Transformer Turns Ratio Out of Tolerance: Causes
References
- OMICRON electronics, CPC 100 product data sheet (omicronenergy.com/en/products/cpc-100).
- OMICRON electronics, data sheets of the CP TD12/15 and TESTRANO 600.
- IEC 60076-1, Power transformers – Part 1: General.
- IEEE Std C57.12.90, Standard Test Code for Liquid-Immersed Distribution, Power, and Regulating Transformers.
- IEEE Std C57.152-2025, Guide for Diagnostic Field Testing of Liquid-Filled Power Transformers, Regulators, and Reactors.
Frequently asked questions
Which power transformer tests are done with the OMICRON CPC 100?
According to the manufacturer, the CPC 100 and its accessories measure transformation ratio, winding resistance, demagnetization, short-circuit impedance and leakage reactance, and capacitance and dissipation factor with the CP TD accessory. Which ones apply to a given transformer depends on its rating, its voltage level and whether it is a commissioning or a diagnostic test.
Can the CPC 100 be used on a three-phase transformer?
Yes. Measurements are made phase by phase or by winding pairs; with the CP SB1 switching box the manufacturer offers an automatic three-phase test setup. To measure all three phases at once with a single wiring, the manufacturer has another system, the TESTRANO 600, which has its own guide.
Does the CPC 100 replace the transformer test plan?
No. The instrument provides the injection and the measurement; which tests are done, in what order, against which criterion and how they are interpreted against the factory protocol and the standards is defined by the test plan. A good instrument with the wrong plan delivers numbers that do not answer the owner's question.