Harmonic voltage
BSRIA Power quality guide (AG 2/2000) was written by C C Pearson and V Uthayanan and published by BSRIA in July 2000. It states:
Distortion is usually measured using a value called the total harmonic distortion (THD). The THD reports the percent of the harmonic components relative to the fundamental. Generally the fundamental component is of constant amplitude. During disturbances the fundamental may drop or increase significantly so that the same level of harmonic becomes a different percentage of the fundamental. In the US standard, IEEE 519, the nominal voltage value is used as the fundamental. An alternative approach is to record the harmonic rms value (hrms), defined as the square root of the sum of the squares of all harmonic components at or above the second component.
Two methods can be used to calculate the hrms value. The most direct way is to determine the value of each harmonic component at or above the second component, sum the squares of each component’s magnitude and then take the square root. However, a more computationally efficient method is to first find the total rms value (which is being calculated anyway), square it, subtract the squares of the fundamental and dc components, and take the square root. This method is equivalent to the direct method since the total rms values are equal to the square root of the sum of the squares of the Fourier coefficients. The formula for hrms is:
--BSRIA
[edit] Related articles on Designing Buildings
Featured articles and news
How much does it cost to build a house?
A brief run down of key considerations from a London based practice.
The need for a National construction careers campaign
Highlighted by CIOB to cut unemployment, reduce skills gap and deliver on housing and infrastructure ambitions.
AI-Driven automation; reducing time, enhancing compliance
Sustainability; not just compliance but rethinking design, material selection, and the supply chains to support them.
Climate Resilience and Adaptation In the Built Environment
New CIOB Technical Information Sheet by Colin Booth, Professor of Smart and Sustainable Infrastructure.
Turning Enquiries into Profitable Construction Projects
Founder of Develop Coaching and author of Building Your Future; Greg Wilkes shares his insights.
IHBC Signpost: Poetry from concrete
Scotland’s fascinating historic concrete and brutalist architecture with the Engine Shed.
Demonstrating that apprenticeships work for business, people and Scotland’s economy.
Scottish parents prioritise construction and apprenticeships
CIOB data released for Scottish Apprenticeship Week shows construction as top potential career path.
From a Green to a White Paper and the proposal of a General Safety Requirement for construction products.
Creativity, conservation and craft at Barley Studio. Book review.
The challenge as PFI agreements come to an end
How construction deals with inherited assets built under long-term contracts.
Skills plan for engineering and building services
Comprehensive industry report highlights persistent skills challenges across the sector.
Choosing the right design team for a D&B Contract
An architect explains the nature and needs of working within this common procurement route.
Statement from the Interim Chief Construction Advisor
Thouria Istephan; Architect and inquiry panel member outlines ongoing work, priorities and next steps.
The 2025 draft NPPF in brief with indicative responses
Local verses National and suitable verses sustainable: Consultation open for just over one week.
Increased vigilance on VAT Domestic Reverse Charge
HMRC bearing down with increasing force on construction consultant says.
Call for greater recognition of professional standards
Chartered bodies representing more than 1.5 million individuals have written to the UK Government.