Protection Engineering Services
Effective protection coordination is essential for safe and reliable power system operation. Whether you're connecting new generation to the grid or managing an existing industrial facility, correct protection settings ensure faults are cleared quickly and selectively, minimising damage and maintaining supply to healthy parts of the network.
We deliver protection studies for a wide range of applications, from G99 grid connections requiring coordination with DNO network protection, to complex industrial sites with legacy equipment and challenging constraints.
Chartered Engineer led, with extensive experience developing practical protection solutions that work within real-world limitations, not just theoretical grading curves.
Protection Study Types
Protection Coordination
Full grading studies from source to load, ensuring correct fault detection, discrimination, and clearance times across all protective devices.
Short Circuit Analysis
Fault level calculations to determine equipment ratings, breaking capacity requirements, and fault contribution from connected generation or network.
Relay Settings Development
Protection settings for overcurrent, earth fault, differential, and distance protection schemes including testing specifications.
Applications
Grid Connections
Protection coordination for G99 Type C and Type D connections, ensuring correct grading with DNO network protection.
Industrial Facilities
Protection studies for manufacturing sites, data centres, and commercial buildings, working within existing equipment constraints.
Network Upgrades
Re-grading studies following switchgear replacement, transformer changes, or network reconfiguration.
Our Approach
Data Gathering
We collect single line diagrams, equipment data, existing protection settings, and network information. For existing sites, we work pragmatically with whatever data is available.
Network Modelling
We build detailed models in DIgSILENT PowerFactory incorporating all protective devices, their characteristics, and the network impedances affecting fault levels.
Grading Analysis
We develop protection settings that achieve correct discrimination throughout the network, accounting for equipment constraints and any non-adjustable upstream protection.
Deliverables
We provide comprehensive reports with settings schedules, time-current curves, and technical notes. Settings are formatted for direct implementation or commissioning testing.
Why the Relay Runs on Extremely Inverse
Above an LV breaker with an I²t long-time band, a standard inverse relay can grade at the maximum fault and still cut under the breaker on overload. Extremely inverse runs parallel with it all the way down.
From an issued grading study, anonymised: a 2500 kVA transformer with the relay 0.366 s above the incomer at the maximum fault.
Frequently Asked Questions
What is protection coordination?
Protection coordination (also called protection grading) ensures that when a fault occurs, only the protective device nearest to the fault operates, while upstream devices remain ready to act as backup. This provides selective fault clearance and minimises disruption to healthy parts of the network.
Do you work on existing industrial sites?
Yes. We specialise in protection studies for existing facilities where equipment constraints, missing data, and legacy protection arrangements require pragmatic engineering solutions. See our Kawneer case study for an example of a large industrial protection project.
What deliverables are included?
A typical protection study includes: short circuit analysis results, time-current coordination curves, recommended settings for all protective devices, equipment adequacy assessment, and technical notes explaining methodology and any caveats.
Try The Calculators First
Four free protection tools, written and maintained in house. Useful on their own, and the quickest way to see how we work before commissioning anything.
IDMT Protection Curves
Trip times for the IEC curves, with the characteristic plotted against the settings.
Open tool →IDMT Test Comparison
Injected test results against the expected curve, per phase, with the deviation.
Open tool →Fault Waveform
Asymmetric fault current with the d.c. offset, against X/R and point on wave.
Open tool →Get Your Protection Study Quote
Send us your single line diagram and project details. We'll confirm scope and provide a fee proposal.