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Earth Leakage in Turbine Systems

Posted on by Voltsys Team

The most common fault found with modern transformerless inverters is earth leakage.

Transformerless inverters take DC power from the turbine, boost it to the required voltage and directly inject it into the grid. It is essential that the DC side is isolated from earth because usually the neutral side of the grid is earthed. The inverter has circuits which work a bit like an RCD or ELCB to detect earth leakage, and also initially to measure “RISO” (Resistance of Isolation).

These circuits will detect leakage via other inverters connected to the same DC supply. For this reason, if you use two or more inverters on the same DC from a turbine, you need to isolate the grid via a transformer on the second and subsequent inverters. So for example, if you have a 15kw turbine on a single phase supply, you would need 3 x 5kw inverters and 2 x isolation transformers. You would disable RISO detection on the two inverters that are isolated

Sometimes, the inverter will fail to start because of a RISO error. The inverter may report a different fault (e.g. IGBT saturation) but the root cause is often RISO. RISO seldom arises in a solar PV environment because the DC side is isolated from the frames. However, water ingress into turbine windings, poor quality underground cables, or exposed connections can all cause tiny earth leakage which will cause failure.

Please read Aurora RISO earth leakage information for further information on how to resolve this problem when it arises.

NZEB – Near Zero Energy Buildings

Posted on by Voltsys Team

Under European Directives, all new buildings must be “Near Zero Energy” if they are completed after 31st Dec. 2020. The new standards apply to all building acquired by public bodies and completed after 31st Dec. 2018.

NZEB-implementation

Any buildings completed after these dates must achieve the standard irrespective of when they were started.

The ‘Nearly Zero – Energy Buildings’ standard requires a very high energy performance, and a significant percentage of the energy requirement must come from renewable sources produced on-site or nearby.

Solar photovoltaic panels are a scalable system that can easily, and economically, help a well-built house to meet these standards.

On 29th July 2016 the European commission published additional guidance on the NZEB standard for the Oceanic zone which applies to Ireland the guidance proposes the following recommendation;

  • Offices: 40-55 kWh/(m2.y) of net primary energy with, typically, 85-100 kWh/(m2.y) of primary energy use covered by 45 kWh/(m2.y) of on-site renewable sources.
  • New single family house: 15-30 kWh/(m2.y) of net primary energy with, typically, 50-65 kWh/(m2.y) of primary energy use covered by 35 kWh/(m2.y) of on-site renewable sources.

In January 2017, the Department of Housing Planning, Community and Local Government, the Office of Public Works, the Department of Education and Skills, the Health Services Executive and Sustainable Energy Authority of Ireland published an Interim NZEB Specification for Public Sector buildings (see HERE). This sets out a performance specification for new buildings owned and occupied by Public Authorities after 31st Dec 2018 effectively meaning that all public buildings on the drawing board must meet the standard.

Implementation

At time of writing, there is a government consultation process on implementation, but the revised regulations and technical document Part L published by the Dept. of Housing, Planning and Local Government require buildings to use up to 60% less energy than allowed under current regulations, plus a requirement for up to 20% of this final demand to be met with renewables. If a higher level of efficiency is achieved the renewables ratio may be reduced to 10% of final demand. (Final demand does not include occupant equipment)