CAN CSA C60044-8-07: Electronic Current Transformers – A Comprehensive Guide to Canadian Standards for Digital Instrument Transformers

Introduction to CAN CSA C60044-8-07

CAN CSA C60044-8-07 is the Canadian adoption of the international standard IEC 60044‑8:2002, titled Instrument transformers – Part 8: Electronic current transformers. Published by the Canadian Standards Association (CSA Group), this standard defines the requirements for electronic current transformers (ECTs) used for both measurement and protection applications in electrical power systems. It covers ECTs with analogue or digital outputs, including those integrated with merging units for digital substation communication.

As part of the C60044 series, this standard addresses the specific performance, accuracy, and testing needs of modern non‑conventional current sensors (e.g., Rogowski coils, Faraday‑effect optical sensors, low‑power current transformers) that have replaced traditional iron‑core current transformers in many installations. The adoption retains the technical content of IEC 60044‑8 while introducing minor modifications to align with Canadian electrical codes and utility practices.

Scope of the Standard

The standard applies to electronic current transformers (ECTs) with:

• Rated primary currents up to 30 kA or higher, depending on the design.
• Analogue output voltages (e.g., 0–10 V, 4–20 mA) or digital output data (e.g., sampled values per IEC 61850‑9‑2).
• Rated frequencies of 15 Hz to 60 Hz (covering both 50 Hz and 60 Hz systems).
• Insulation requirements up to the highest voltage for equipment (Um) of 800 kV AC or higher.

It covers electronic current transformers intended for use with measuring instruments, protective relays, and other devices where accuracy and transient performance are critical. The standard also defines the requirements for the merging unit (MU) when it is considered part of the ECT assembly.

Technical Requirements and Performance Specifications

1. Accuracy Classes

Two categories of accuracy are defined:

• Measurement ECTs – Classes 0.1, 0.2, 0.5, 1, 3 (similar to traditional CTs).
• Protection ECTs – Classes 5P, 10P for non‑transient performance, and TPX, TPY, TPZ classes for transient performance (per IEC 61869‑2 adaption for ECTs).

2. Output Signal Characteristics

For analogue output ECTs, the standard specifies:

• Rated secondary output voltage (e.g., 0–10 V, 0–5 V or 4–20 mA).
• Load impedance – maximum burden (in ohms) for which accuracy is guaranteed.
• Linear range – typically from 0.5 % to 200 % of rated primary current.

For digital output ECTs (with a merging unit), the output shall comply with IEC 61850‑9‑2 sampled value format (SV) at 80 samples/cycle for protection and 256 samples/cycle for metering. The standard defines the data set composition, time synchronization accuracy (<10 µs), and loss‑of‑frame detection.

3. Insulation and Safety Requirements

CAN CSA C60044-8-07 adopts the insulation levels defined in IEC 60044‑1 and IEC 60044‑8, including:

• Power‑frequency withstand voltage tests.
• Lightning impulse test (full wave and chopped wave).
• Partial discharge measurement limits (e.g., <10 pC for paper‑oil insulation).
• Clearance and creepage distances per CSA C22.2 No. 0.**

Additionally, the standard incorporates requirements for short‑circuit withstand (rated short‑time thermal current I_th and dynamic current I_dyn) to ensure the sensor can survive temporary overcurrents without damage.

Implementation Highlights for Modern Power Systems

Digital Substation Integration

CAN CSA C60044‑8‑07 is a key enabler for IEC 61850‑based digital substations. Electronic current transformers can be directly connected to merging units that output sampled values over Ethernet, eliminating lengthy copper wiring and reducing the risk of open‑circuit high voltages. The standard specifies the digital data format (16‑bit or 32‑bit integer, with scale factors) and the communication protocol (ISO/IEC 8802‑3 Ethernet).

Measurement and Protection Co‑existence

One ECT can simultaneously serve multiple protection and measurement devices through the merging unit’s multi‑cast SV stream. The standard ensures that the same current data meets both metering accuracy (e.g., 0.2 % error) and protection transient requirements (Ktd up to 10 or more). This dual‑use capability reduces the number of current sensors required in a bay.

Environmental and Long‑Term Reliability

Unlike conventional CTs with magnetic cores, electronic current transformers are immune to saturation, hysteresis, and remanence. The standard includes accelerated aging tests (temperature cycling, vibration, humidity) to validate long‑term stability of optical or electronic components. Many implementations achieve a mean time between failure (MTBF) exceeding 20 years.

Compliance and Certification Notes

Conformity Assessment in Canada

CAN CSA C60044‑8‑07 is listed in the CSA Group’s directory of standards and is recognized by provincial and territorial electrical authorities. Compliance is typically demonstrated through:

• Type tests – performed once on a representative product to verify design integrity (accuracy, transient, insulation, EMC).
• Routine tests – executed on every unit (dielectric test, ratio, polarity, and output signal verification).
• Factory production control (FPC) – the manufacturer must maintain a quality management system (e.g., ISO 9001 or CSA Q9001) and production tests.

Modifications from IEC 60044‑8

While CAN CSA C60044‑8‑07 is largely identical to IEC 60044‑8, the CSA version incorporates the following Canadian deviations:

• Reference to CSA C22.2 No. 0** (General Requirements – Canadian Electrical Code, Part II) for construction and marking.
• Ambient temperature range extended to –40 °C to +55 °C (vs. –25 °C to +55 °C in the IEC edition) to suit Canadian climate conditions.
• Additional requirements for anti‑condensation heating in outdoor enclosures (merging units) per CSA C22.2 No. 94.2.

Frequently Asked Questions

Reference year: 2026 – This article is based on the 2007 edition of CAN CSA C60044‑8‑07, reaffirmed in 2017. Engineers should consult the latest CSA publication for updates.