CAN CSA C60044-7-07: Electronic Voltage Transformers – Technical Overview and Compliance Guidelines

Introduction and Scope

CAN CSA C60044-7-07, officially designated as the Canadian adoption of IEC 60044-7:1999, specifies the requirements for electronic voltage transformers (EVTs) used for measurement and protection in electrical power systems. This standard applies to voltage transformers with analogue or digital outputs intended for use at frequencies of 15 Hz to 100 Hz, covering rated voltages above 1 kV. It defines the technical characteristics, performance requirements, and testing methods for EVTs, which differ fundamentally from conventional inductive voltage transformers by employing electronic circuitry to convert primary voltage into a low-power output signal.

The standard was published in 2007 as part of CSA Group’s harmonization with IEC standards. It is recognized across Canada and supports the integration of modern electronic instrument transformers into grid infrastructure, enabling digital substations and smart grid applications. The scope includes transformers for both metering (revenue-grade accuracy) and protective relaying, and it covers all environmental conditions typical for indoor and outdoor installations.

Key Distinction: Unlike conventional VTs that output a scaled-down AC voltage (e.g., 115 V / √3), electronic voltage transformers under CAN CSA C60044-7-07 can output low-level analogue signals (e.g., 1 V, 2 V, 4 V) or digital frames via IEC 61850 process bus. This reduces burden and enables direct interface with microprocessor-based relays and meters.

Technical Requirements

Accuracy Classes for Measurement and Protection

The standard defines multiple accuracy classes to suit different applications. Table 1 summarizes the limits of voltage error and phase displacement for the most common classes used in Canada.

Table 1 – Accuracy Classes for Electronic Voltage Transformers per CAN CSA C60044-7-07
Class	Application	Voltage Error (±%)	Phase Displacement (± minutes)
0.1	Precision metering	0.1	5
0.2	Revenue metering	0.2	10
0.5	General metering	0.5	20
1.0	Indication / control	1.0	40
3P	Protection (relaying)	3.0	120
6P	Protection (general)	6.0	240

These classes apply at rated frequency (typically 60 Hz in Canada) over a voltage range of 80% to 120% of rated primary voltage. For protection classes, the standard also specifies accuracy under transient conditions, ensuring reliable operation during system faults.

Output Voltage Specifications

CAN CSA C60044-7-07 standardises low-power output signals to facilitate interchangeability. The rated secondary voltage (U_s) is defined at rated primary voltage. Common values include:

Analogue output: 0 – 4 V, 0 – 10 V, or 0 – 100 V (rms) for line-to-line or phase-to-neutral connections.
Digital output: IEC 61850-9-2 sampled values (SMV) with data formats defined in the standard.

The output burden must be within the specified range, typically between 10 kΩ and 1 MΩ, to maintain accuracy. The standard also mandates a maximum allowable change in output voltage due to temperature variations over the range -40°C to +55°C.

Caution for Retrofits: When replacing an inductive VT with an EVT in an existing installation, verify that the secondary wiring and protection devices are compatible with the low-energy output. Traditional electromechanical relays may not operate correctly without signal conditioning.

Implementation and Testing Considerations

Manufacturers and users must follow rigorous type-test and routine-test procedures to demonstrate compliance. Key tests defined in the standard include:

Accuracy tests: Verification of voltage ratio and phase displacement under steady-state and transient (if applicable) conditions.
Insulation tests: Power-frequency withstand voltage, lightning impulse, and partial discharge measurements to ensure dielectric integrity.
Electromagnetic compatibility (EMC): Immunity to radiated and conducted disturbances, as EVTs contain sensitive electronic circuits.
Environmental tests: Temperature cycling, humidity, and vibration to verify ruggedness in field conditions.

For digital EVTs, conformance with the communication protocol (e.g., IEC 61850-9-2) is also evaluated. CAN CSA C60044-7-07 references IEC 60044-7 for most test procedures but includes Canadian deviations, particularly for voltage levels (e.g., 138 kV, 230 kV) and ambient temperature ranges typical of Canadian climates.

Compliance and Certification in Canada

All electronic voltage transformers sold or used in Canada for utility applications must meet CAN CSA C60044-7-07. Certification is typically performed by CSA Group or other accredited bodies. The standard is harmonised with IEC, but there are specific Canadian variations:

Rated primary voltages include 69 kV, 115 kV, 138 kV, 230 kV, and 500 kV as standard values.
Maximum operating temperature range is -50°C to +55°C for outdoor installations in northern regions.
Digital output must support a minimum sample rate of 80 samples/cycle for protection and 256 samples/cycle for metering.

Compliance marks (e.g., CSA Monogram) are accepted by provincial regulators such as the Ontario Electrical Safety Authority (ESA) and the British Columbia Safety Authority (BCSA). ANSI/IEEE standards may also be referenced, but CAN CSA C60044-7-07 is the primary instrument transformer standard for voltage measurement in Canadian high-voltage grids. The standard was reaffirmed in 2011 and 2022, confirming its ongoing relevance.

Compliance Best Practice: Always request a certificate of type-test from the EVT manufacturer that explicitly cites CAN CSA C60044-7-07. This ensures that the device is accepted by Canadian utilities without additional project-specific testing.

Frequently Asked Questions

Q: Is CAN CSA C60044-7-07 identical to IEC 60044-7?
A: It is technically equivalent but includes national deviations for Canadian voltage classes, climatic conditions, and cross-references to CSA insulation standards. Any manufacturer claiming compliance to IEC 60044-7 must also meet the Canadian differences to be certified under this standard.

Q: Can an electronic voltage transformer replace a conventional VT without changing relays?
A: Not directly. The low-level output (typically 0–10 V) is incompatible with traditional 115 V relay inputs. You will need a signal converter or a relay that directly accepts low-voltage signals. Modern protection relays often have dedicated low-energy input modules; check the relay manual before substitution.

Q: What accuracy class should I select for revenue metering?
A: For billing applications, Class 0.2 is commonly required in Canada. Confirm with your local utility, as some provinces may mandate Class 0.1 for high-power transmission interties. Protection applications typically use Class 3P or 6P.

Q: Does the standard cover EVTs with digital output?
A: Yes. It defines the protocol, data format, and accuracy requirements for sampled values. For substation integration, the digital output must conform to IEC 61850-9-2 LE (Light Edition) or the full edition as specified by the utility.

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