IEC 61869-15:2018

Overview

IEC 61869-15:2018 is an international standard specifying additional requirements for voltage transformers used in direct current (DC) applications, commonly referred to as DC voltage transformers (DCVTs). This part of the IEC 61869 series addresses the unique needs of voltage transformers operating in DC power systems with rated voltages above 1.5 kV. The standard applies regardless of the technology used, encompassing both passive voltage dividers and active voltage transformers with analogue or digital output signals.

Designed to support measuring, protection, and control functions in DC networks, IEC 61869-15:2018 details the configuration, performance, and testing criteria specific to voltage transformers for DC environments. It supplements and modifies requirements established in IEC 61869-1 (General Requirements) and IEC 61869-6 (Additional Requirements for Low-Power Instrument Transformers), thereby integrating the complex challenges posed by DC systems into the broader instrument transformer framework.

Key Topics

• Scope and Applicability
  The standard covers voltage transformers with rated voltages exceeding 1.5 kV that are used primarily for measurement, control, and protection purposes in DC power systems. It defines requirements applicable to output signals that may be analogue or digital, facilitating integration into modern monitoring and control setups.

• Technology Considerations
  Presently, DCVTs commonly utilize resistive voltage dividers, optionally supplemented by capacitive elements. The standard incorporates additional requirements relevant to these technologies but remains technology-neutral to accommodate emerging solutions such as optical voltage sensors.

• DC Converter Technologies
  IEC 61869-15 classifies DC power systems by the type of converter technology employed:

  • Line-Commutated Converters (LCC): Based on thyristor technology, characterized by unidirectional current flow and voltage polarity reversals. These systems generate significant voltage and current harmonics up to 3-4 kHz.
  • Voltage Source Converters (VSC): Employing transistor switches, these allow bi-directional current flow with a single voltage polarity. Harmonic frequencies can reach up to approximately 20 kHz.

• Functional Requirements
  The standard emphasizes two main functional criteria for DCVTs:

  • Accurate measurement of DC voltage, including harmonic components.
  • Robust electrical insulation and ability to withstand steady-state and transient DC voltages.

• Performance Standards
  IEC 61869-15 outlines accuracy classes ranging from 0.1 to 3 for ratio errors, defining strict limits to maintain measurement precision in challenging DC environments. It also mandates rigorous testing regimes, including partial discharge, voltage withstand, polarity reversal, and step response time assessments to ensure reliability and safety.

Applications

IEC 61869-15:2018 is critical for industries relying on high-voltage DC systems that require precise and dependable voltage measurement and monitoring. Typical applications include:

• HVDC Transmission
  Ensures accurate voltage measurements in high-voltage direct current transmission lines, enhancing system protection and control.

• Power Conversion Systems
  Supports equipment employing both LCC and VSC technologies by providing harmonics-safe voltage measurement solutions.

• Renewable Energy Integration
  Facilitates measurement and control in DC power plants and energy storage systems where DC voltage transformers are integral to monitoring and protection.

• Industrial and Utility Control Systems
  Offers reliable voltage sensing for operations in electrochemical processes, rail transport electrification, and other industrial DC applications.

Related Standards

IEC 61869-15:2018 is part of the IEC 61869 instrument transformer series and should be used alongside the following relevant documents for comprehensive compliance:

• IEC 61869-1: General Requirements for Instrument Transformers
• IEC 61869-6: Additional General Requirements for Low-Power Instrument Transformers
• IEC 61869-14: Additional Requirements for Current Transformers for DC Applications
• IEC 61869-3: Additional Requirements for Inductive Voltage Transformers
• IEC 61869-9: Digital Interface for Instrument Transformers

These complementary standards collectively cover various types of instrument transformers, providing a complete regulatory framework for both AC and DC systems.

Keywords: IEC 61869-15, voltage transformers, DC voltage transformers, DCVT, instrument transformers, voltage measurement, high-voltage DC systems, line-commutated converters, voltage source converters, power system protection, electrical standards, measurement accuracy.