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CAN CSA C61869-4-14 (2015): Comprehensive Guide to Combined Instrument Transformer Standards
Understanding the Canadian Adoption of IEC 61869-4 for Combined Transformers
Scope and Application
CAN CSA C61869-4-14 (2015) is the Canadian adoption of the international standard IEC 61869-4:2014, which specifies additional requirements for combined instrument transformers. A combined transformer integrates a current transformer (CT) and a voltage transformer (VT) within a single insulation enclosure, often used in high-voltage substations for metering, protection, and control.
This standard applies to newly manufactured combined transformers with rated voltages above 1 kV, covering both inductive and capacitive designs used in power systems at frequencies of 15 Hz to 100 Hz. It supplements the general requirements defined in IEC 61869-1 (adopted as CAN CSA C61869-1) and the specific parts for current (CAN CSA C61869-2) and voltage (CAN CSA C61869-3) transformers.
The document is intended for manufacturers, testing laboratories, utility engineers, and regulatory authorities. It defines performance parameters, type and routine tests, and marking requirements specific to the unique interaction between voltage and current sensing elements within a common housing.
Tip: Although CAN CSA C61869-4-14 is harmonized with IEC 61869-4, users in Canada should always check the national deviations published by CSA Group, which may impose additional environmental or seismic requirements for Canadian installations.
Key Technical Requirements
Construction and Insulation
The standard mandates that the combined transformer must maintain electrical clearances between the CT and VT circuits that are at least equivalent to those required for each component individually. The common insulation system must withstand the same lightning impulse, switching impulse, and power-frequency test voltages as specified for the highest voltage of the equipment (Um).
Accuracy and Burden
Accuracy classes for the current and voltage elements are defined separately, and the standard requires that the presence of one element does not degrade the performance of the other beyond permissible limits. For example, the magnetic flux produced by the CT core must not induce significant error in the VT output. The rated burdens for each element are assigned independently, but the combined thermal rating must consider the sum of the internal heat generation.
| Element | Class Designation | Application | Limit of Error (Ratio/Phase) |
|---|---|---|---|
| Current (CT) | 0.2S, 0.5S, 1.0 | Metering / Protection | ±0.2% / ±10 min (0.2S) |
| Current (CT) | 5P, 10P, PR | Protection core | ±1%–3% / ±60–120 min |
| Voltage (VT) | 0.2, 0.5, 1.0, 3.0 | Metering / Protection | ±0.2%–3.0% / ±10–40 min |
No-load losses and overvoltage performance of the combined unit are tested as a whole. The standard also introduces specific partial discharge (PD) limits that must not be exceeded when the combined transformer is energized from either the CT or VT side.
Warning: When performing type tests, the mutual electromagnetic interference between the CT and VT elements must be evaluated. Failure to verify this interaction can lead to unmet accuracy specifications in field operation.
Implementation and Design Considerations
Designers integrating combined transformers into switchgear or GIS must pay attention to the thermal dissipation capability. Because two independent core-and-winding assemblies share a common insulation system, heat accumulation may be higher than in separate devices. The standard requires a temperature-rise test at rated continuous current and rated voltage simultaneously.
Mechanical resonance frequencies of the combined assembly must be measured and documented, as the larger mass can affect seismic withstand. The standard references IEC 61869-1 for vibration and shock tests but adds specific deflection limits between the CT and VT parts.
Marking and Documentation
Each combined transformer must be marked with both the ratings for the current and voltage circuits, the common insulation level, and a warning that the device contains two independent secondary circuits. Terminal markings follow IEC 61869-2 and -3 conventions, with additional differentiation for the shared primary terminals.
Good practice: Prepare a single winding diagram that shows the electrical and magnetic coupling between the CT and VT circuits. This simplifies both type testing and field commissioning.
Compliance and Certification
Compliance with CAN CSA C61869-4-14 (2015) is typically demonstrated through:
- Type tests performed on a representative sample at an accredited laboratory, including impulse voltage, accuracy verification, and temperature rise for the combined unit.
- Routine tests on every manufactured unit — power-frequency voltage withstand (applied separately to CT and VT windings), partial discharge measurement, and verification of terminal markings.
- Special tests such as mechanical strength (short-circuit) for the CT element and residual voltage measurement for the VT element, as required by the purchaser.
In Canada, certification by a recognized body (e.g., CSA, QPS, or Intertek) is often a condition of sale to major utilities. The standard may be referenced in provincial electrical codes or by individual power authorities. Manufacturers should maintain a product file that includes a declaration of conformance to the national deviations of CAN CSA C61869-4-14.
Critical: The Canadian adoption includes a national deviation for operation in extreme cold climates down to –50 °C. Manufacturers must verify that the insulating oil or SF6 gas pressure remains within acceptable limits over the full temperature range.
Frequently Asked Questions
Q: How does CAN CSA C61869-4-14 differ from the original IEC 61869-4:2014?
A: The CAN CSA version is technically equivalent to IEC 61869-4:2014, but includes Canadian national deviations related to extreme temperature ranges (Class 1A and 2A climates), seismic requirements, and bilingual marking. Always consult the current CSA Group publication for the precise list of deviations.
A: The CAN CSA version is technically equivalent to IEC 61869-4:2014, but includes Canadian national deviations related to extreme temperature ranges (Class 1A and 2A climates), seismic requirements, and bilingual marking. Always consult the current CSA Group publication for the precise list of deviations.
Q: Can a combined transformer designed to IEC 61869-4 be sold in Canada without retesting?
A: Not automatically. While the two standards are aligned, a declaration of conformity to the CAN version is required. Some laboratories offer a verification audit to convert existing IEC type test reports to CSA acceptance, but climate-related deviations often necessitate additional testing.
A: Not automatically. While the two standards are aligned, a declaration of conformity to the CAN version is required. Some laboratories offer a verification audit to convert existing IEC type test reports to CSA acceptance, but climate-related deviations often necessitate additional testing.
Q: What is the typical certification process for a combined transformer under this standard?
A: The process involves submitting a type test report from an ISO/IEC 17025 accredited lab, completing a product review by a certification body (e.g., CSA), and undergoing periodic factory inspections. The certification mark (e.g., CSA or cUL) must appear on the nameplate.
A: The process involves submitting a type test report from an ISO/IEC 17025 accredited lab, completing a product review by a certification body (e.g., CSA), and undergoing periodic factory inspections. The certification mark (e.g., CSA or cUL) must appear on the nameplate.
Q: Are there separate requirements for optical or non-conventional combined transformers?
A: Yes. Non-conventional instrument transformers (NCIT) are covered by IEC 61869-9 to -12 series, which is not yet fully adopted by CSA. For combined NCIT, the applicable part is IEC 61869-13, and a separate CSA adoption may follow. Until then, project-specific agreements are common.
A: Yes. Non-conventional instrument transformers (NCIT) are covered by IEC 61869-9 to -12 series, which is not yet fully adopted by CSA. For combined NCIT, the applicable part is IEC 61869-13, and a separate CSA adoption may follow. Until then, project-specific agreements are common.
First published: 2015 | Current edition reaffirmed: 2026. This article provides general guidance; always refer to the official standard and your certification body for exact requirements.