Application, design and protection of mechanically switched capacitors with damping networks

All our clients have access to the combination of excellent quality products backed by specialist local and international engineering skills to develop and deliver solutions at all levels of the energy business.

For example in this article design aspects of mechanically switched capacitors with damping networks (MSCDN), also called “C-type filters” are presented, with relevant information and recommendations regarding the specification and protection of the filter components. Innovative relaying schemes are presented to ensure reliability and sensitivity for internal faults on the components, in particular air-core reactors, in order to avoid major damage to them and allowing further analysis of the causes of faults.

The combination of our ability to model and understand your electricity network and the support of excellent engineering and production resources internationally provides our clients with un-equalled confidence in the solutions they implement. Contact us and experience it for yourself.

A new era with GE Grid Solutions

It is a great pleasure to announce that due to the acquisition of Alstom Grid by GE, and the subsequent formation of GE Grid Solutions, we can now serve our customers even better with an expanded, fully resourced and competitive product range of reactive power compensation solutions. The formal transaction occurred on Monday 2 November 2015.

Our full product range is available on the download page. Here are some extracts:

As always we look forward to serving our customers by adding value to their businesses with our local expertise, excellent quality products and project delivery capabilities.

Specifying and designing medium voltage enclosed capacitor banks

We provide solutions based on strong technical merits and a professional approach to our business.  An example of our approach can be found in our solution for enclosed capacitor banks as described in this article. We understand that buyers, users and suppliers all have somewhat different histories and preferences, and we aim to provide a clear description of the most important things to look out for in the specification, procurement, design, manufacturing, delivery and operation of enclosed medium voltage capacitor banks. We would be delighted to discuss this in more detail with you.

Recertification of Quality System

We support our power industry customers from concept designs, power system analysis, product selection and all the way through their project delivery. Our specialists are available to provide you with all the detailed product and application information you need for optimised, best quality solutions.

These are not empty words. Our recent recertification to ISO 9001:2008 demonstrates that all our activities are governed by our quality system. Our customers see the benefits of dealing with a lean, technically expert supplier that does not compromise on quality when advising on, designing, or delivering reactive power compensation solutions.

Contact us at any time and we will work hard to optimise your network.

Need active harmonic filters? We have the best.

What do you get when you combine the best performing active harmonic filter on the market with on-site evaluation and detailed application engineering support? The MaxSine Compact: it ticks all the boxes:

  • Modular design from 50 A to multiples of 100 A
  • Flexible mounting in OEM panels, wall or floor mounted cubicles
  • Several control options for fast and super fast (<1 ms) compensation
  • Neutral current compensation
  • Reactive power compensation
  • Powerful yet simple setup by means of web browser interface

Applications range from anywhere with electronic loads that are sensitive to power disturbances like hospitals and office blocks, to any fast changing linear or non-linear load.

Optimised Network Equipment has the necessary measurement equipment to evaluate your requirements on site, and can carry out efficient studies to confirm your exact requirements for harmonic filtering – active or passive – no matter what your location or application.

Zero power harmonic filters

Harmonic filters remove harmonic current from the network and improve load power factor. Some applications require harmonic mitigation without any significant reactive power contribution, for example when non-linear loads operate at close to unity power factor and the network cannot accept leading reactive power.

ONE has designed, delivered and tested solutions based on harmonic filters that draw current only at harmonic frequencies, and describe the design and steady state and transient performance in a technical note. The outcome is a passive filter circuit that is an effective solution of harmonic distortion yet that draws almost no fundamental frequency current, and has no onerous switching requirements.

Please contact us if more information is required.

Selecting current transformers for capacitor bank protection

Medium and high voltage capacitor banks require protection against faults in the capacitor units and in the associated equipment such as feeder cables, series reactors, overhead structures and conductors connecting the various parts of the capacitor bank.

Faults inside capacitor units are generally cleared by internal fuses. The operation of these fuses must be monitored to allow for appropriate alarm and trip instructions to be issued based on voltage stress levels in the capacitor units. The same applies for unfused units with unbalance current providing an indication of the number of shorted elements. Such protection depends on very sensitive detection of relatively small currents in the star points of capacitor banks. External faults are either phase to ground or phase to phase and require more conventional over current and earth fault detection.

Both of these types of protection require current transformers to provide the necessary detection of current in the primary circuit. Appropriate selection of protection current transformers is therefore essential for safe operation of capacitor banks. This selection must be done to assure correct operation of protection while minimising cost and avoiding any false operation of protection, i.e. ensuring continuity of operation wherever possible.

ONE has prepared a brief application note describing this selection process to assist our clients in this process. Please contact us if more information is required.

Experts in harmonic filter design

Harmonic mitigation can take many forms and Optimised Network Equipment can assist you in selecting the most appropriate solution, whether that relates to alternative network designs, active filters or passive filters.

Passive filters are very efficient solutions and can reduce harmonic emissions up to 90%.

The art of harmonic filter design is to select the shape of the filter impedance to modify the network impedance in such a manner that the necessary reduction in harmonic current is achieved without causing amplification of other harmonics, taking into account the possible variations in network impedance, and to produce this solution at the lowest possible cost.

We have summarised some important aspects of filter design, including the nature of loads in modern electricity networks, practical harmonic measurements and guidelines on passive filter design in an application note. Please see our downloads area for articles and other technical content.

Training for Vestas Singapore

In early December 2013 we presented a training course on harmonic filters to specialist engineers from Vestas in Singapore. The intention of the course was to extend the knowledge of engineers on practical and theoretical aspects of harmonic analysis, filter design, and component ratings. The course was attended by a truly international audience, with Singapore, Australia, New Zealand, China, India, Venezuela and Vietnam represented. The training lasted three days and included real world examples of filter design for wind farm connections.

We are passionate about our field of expertise and welcome any opportunity to share our knowledge with customers and their consultants. Contact us if you would like to know more.

ONE participates in the DIgSILENT User Group meeting in Sydney on 5-6 September 2013

Having the right tools for the job is essential, and when the job is to carry out complex harmonic filter design studies then the choice of the best power system analysis tools is critical. At Optimised Network Equipment we make extensive use of DIgSILENT PowerFactory for network analysis, allowing us to offer services ranging from compliance studies, conceptual design of solutions, and all the way to detailed engineering design covering aspects of harmonic filter component rating, switching transient analysis and stability analysis. Our infinite bus license enables us to tackle any problem, no matter how complex.

As a demonstration of our commitment to this aspect of our business and to share our experience with other users of the software we recently presented a paper on harmonic filter design to the bi-annual user group meeting in Sydney.

The paper can also be found in the Download section of the site. We would welcome any comment to this contribution.