Voltage interruptions
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:
An interruption occurs when the supply voltage or load current decreases to less than 10% for a period of time not exceeding 3 minutes. Longer periods of such low voltage are referred to as sustained interruptions.
Interruptions can be the result of power system faults, equipment failures, and control malfunctions. The interruptions are measured by their duration, since the voltage magnitude is always less than 10% of nominal. The duration of an interruption due to a fault on the utility system is determined by the operating time of utility protective devices. Instantaneous reclosing generally will limit the interruption caused by a non-permanent fault to less than 30 cycles. Delayed reclosing of the protective device may cause a momentary or temporary interruption. The duration of an interruption due to equipment malfunctions or loose connections can be irregular.
Some interruptions may be preceded by a voltage sag when these interruptions are due to faults on the source system. The voltage sag occurs between the time a fault initiates and the protective device operates.
--BSRIA
[edit] Related articles on Designing Buildings
Featured articles and news
A now architectural practice looks back at its concept project for a sustainable oceanic settlement 25 years on.
Copyright and Artificial Intelligence
Government report and back track on copyright opt out for AI training but no clear preferred alternative as yet.
Embedding AI tools into architectural education
Beyond the render: LMU share how student led research is shaping the future of visualisation workflows.
Why document control still fails UK construction projects
A Chartered Quantity Surveyor explains what needs to change and how.
Inspiration for a new 2026 wave of Irish construction professionals.
New planning reforms and Warm Homes Bill
Take centre stage at UK Construction Week London.
A brief run down of changes intentions from April in an onwards.
Reslating an ancient water mill
A rare opportunity to record, study and repair early vernacular roofs.
CIOB Apprentice of the Year 2025/26
Construction apprentice from Lincoln Mia Owen wins this years title.
Insulation solutions with less waste for a circular economy
Rob Firman, Technical and Specification Manager, Polyfoam XPS explains.
Recycled waste plastic in construction
Hierarchy, prevention to disposal, plastic types and approaches.
UK Net Zero Carbon Buildings Standard V1 published
Free-to-access technical standard to enable robust proof of a decarbonising built environment.
Prostate Cancer Awareness Month
Why talking about prostate cancer matters in construction.
The Architectural Technology podcast: Where it's AT
Catch up for free, subscribe and share with your network.
The Association of Consultant Architects recap
A reintroduction and recap of ACA President; Patrick Inglis' Autumn update.
The Home Energy Model and its wrappers
From SAP to HEM, EPC for MEES and FHS assessment wrappers.
Future Homes Standard Essentials launched
Future Homes Hub launches new campaign to help sector prepare for the implementation of new building standards.
Building Safety recap February, 2026
Our regular run-down of key building safety related events of the month.