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TB: EMC within power plants and substations

13/03/2013

WG C4.208 has developed a newly revised version of this important EMC guide

Electrical power generating stations, substations, control centres and networks are increasingly complex. As such, required standards of reliability are becoming more demanding. While modern electronic systems provide the ever-advancing computing power that enables online automation, the need for greater electromagnetic compatibility (EMC) is ever increasing.

Technology has achieved significant advances in energy efficiency and energy transfer in modern automation and telecommunications processes. Meanwhile, the equipment involved is becoming more susceptible to electromagnetic interference (EMI). Cigré Working Group (WG) C4.208 has followed these technology advancements and their impact on EMC.

 

New guide reflects latest technology developments

The EMC Guide 124 (“EMC within Power Plants and Substations”) was first published by Cigré in December 1997 to provide practising engineers with a reference for EMC within power systems. Indeed, it is used extensively by utilities and engineers around the world.

 

Since the guide’s initial publication, there have been significant changes in several areas of EMC, which contributed to the need for an updated guide. These changes include:

  • Power system, network control and monitoring developments
  • Implementation of smart grids at the distribution level
  • Increased use of fibre-optic technology
  • Introduction of decentralised electronics or integrated electronic sensors/systems

 

As such, Cigré WG C4.208 has developed a newly revised version of this important EMC guide.  Also reflected in the guide is recent work by Cigré working groups and Italtel in the following areas:

  • Insulation coordination and EMC in substation secondary circuits
  • EMI in HV substations
  • Radio frequency interference from substations
  • Cable earthing
  • New measurements and IEC standards

 

Written primarily for those responsible for measurement, control, protection, communications and supervision circuits, the guide provides an overview of problems encountered, solutions, implementation best practices and recommended tests to ensure problems will not recur. The updated guide incorporates user feedback on structure and layout to facilitate easy reading.

 

A close look at EMI disturbances

Electromagnetic interference manifests as errors and failures that tend to recur until properly diagnosed and solved. Every incident of interference involves a source of disturbance, a coupling mechanism and a susceptible piece of equipment. EMC ensures adequate immunity margins are continuously maintained to keep equipment from becoming susceptible to this type of interference.

 

In practice, the enormous quantity of parameters involved in calculating disturbance levels makes it costly and difficult to verify every combination at the design stage. Instead, the working group used the experience of designers, builders and users of different installations to:

  • Classify electromagnetic environments
  • Characterise worst-case disturbances
  • Choose reasonable immunity levels for each environment
  • Ensure no disturbances exceed the threshold
  • Specify equipment to provide immunity level
  • Develop tests to verify success

 

Identifying sources of disturbance

Characterised in terms of amplitude, frequency and duration, the main sources of disturbance are discussed, including high- and low-voltage equipment, communication systems and atmospheric phenomena. The focus is on sources of disturbance likely to have an effect on primary plant (the system handling power flow) or secondary plant (the control and monitoring system).

 

Field experiences provide the characteristics of disturbance levels in HV substations and generating plants. Classes of disturbance levels are discussed along with their role in defining appropriate immunity tests. The working group investigates the mechanics involved in coupling – the bridge between a disturbance and a vulnerable piece of equipment – including the ways that disturbances propagate through cables and other components. This provides the background information to devise disturbance mitigation measures.

 

Testing and implementation

Immunity and emission tests were developed to determine acceptable and unacceptable degrees of interference, taking into account the nature of disturbances and equipment functions affected. Lab tests check whether equipment, once installed in the field, will be compatible with its electromagnetic environment. In-situ tests can be used as the final step of EMC design to check specific mitigation methods and margins.

 

The guide discusses practical implementation and the importance of adopting an EMC plan at every stage of a project, including:

  • Conceptual design
  • Specification
  • Construction
  • Installation
  • Testing
  • Maintenance

 

The best technical-economical solution is to balance actions during installation, such as reducing disturbances at the source and preventing unwanted coupling, with actions to improve immunity on vulnerable equipment. While acknowledging the significant risks of deficient EMC design, the working group concludes that standardised EMC measures should be included at the design stage rather than on a case-by-case basis.

 

Want to learn more? Read the full technical brochure on e-Cigré: ‘EMC within Power Plants and Substations’

 

A special thanks to the Cigré members who participated in the Working Group for this study!

W.H. Siew (Convener, United Kingdom), Akihiro Ametani (Japan), Xiang Cui (China), Roy Hubbard (South Africa), Purshottam Kalky (India), Qingmin Li (China), Neil McDonagh (Ireland), Peeter Muttik (Australia), William Radasky (USA), Patricio Munhoz Rojas (Brazil), Pieter Pretorius (South Africa), Joao Saad Junior (Brazil), Ener Salinas (Sweden), David Thomas (United Kingdom), John Van Coller (South Africa), Xiaowu Zhang (China), Jean Hoeffelman (Belgium)