01 · Calculation
Protection Studies & Settings Calculation
Short-circuit, coordination and relay settings calculations with a documented basis your engineers can review.
- 50/51
- 50N/51N
- 67/67N
- 87T
- 49
- 27/59
- 81
Protection settings are only as sound as the data and criteria behind them. A protection study establishes fault levels for the operating cases that matter, checks how devices coordinate, and records why each setting has its value — so the result can be reviewed, implemented and revisited when the system changes.
When this work is relevant
- The network has changed since settings were last calculated.
- Trips have been non-selective or difficult to explain.
- New equipment or a new installation needs settings.
- Existing settings have no documented basis.
Typical inputs
- Single-line diagram
- Source fault levels from the utility or upstream system
- Transformer, cable, generator and motor data
- CT and VT ratios and classes
- Existing relay settings and models
Missing information is common. We list what is missing and agree how to handle it — for example by stating assumptions.
Possible scope
What the work can include
The scope for each project is agreed in writing. These are the elements most often included.
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01
Short-circuit calculation
Fault levels at relevant points for the agreed maximum and minimum operating cases, using methods such as IEC 60909 where appropriate to the project.
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02
Relay settings calculation
Settings for overcurrent, earth-fault, directional, differential, voltage, frequency and thermal functions as required — each with its basis recorded.
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03
Coordination and grading
Time–current coordination for each protection path, checked at the fault levels and operating cases agreed in the scope.
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04
CT adequacy checks
Checks of current transformer performance for the functions that depend on it, based on the CT data available.
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05
Settings review
Independent review of existing settings against the current system, highlighting where they no longer meet the agreed criteria.
Expected deliverables
Advice, engineering — or both
Advice & review
Independent reviews, investigations and second opinions that help you decide what to do — and explain why.
- Settings criteria and protection philosophy review
- Independent review of existing settings
- Review of disturbance and event records you provide
- Review of third-party study reports
Engineering deliverables
Calculations, settings, logic and documentation developed to an agreed scope, ready for your team's review and implementation.
- Short-circuit and coordination study report
- Relay settings schedule with calculation references
- Time–current coordination plots
- Manufacturer-native settings files, where the platform, tools and scope allow
See illustrative previews: Protection study and coordination report · Relay settings schedule · Technical findings and recommendations
Dependencies and scope boundaries
- Results depend on the data provided. Where data is missing, assumptions are stated and should be confirmed.
- The study covers the operating cases agreed in scope; other cases may give different results.
- A study does not confirm how relays are actually set in the field — that requires checking and testing on site by authorised personnel.
How the work usually runs
- 01Data reviewCheck the drawings and data provided and list what is missing or uncertain.
- 02Model and calculateBuild the system model, calculate fault levels and develop settings against the agreed criteria.
- 03Coordinate and reviewCheck coordination for each protection path and discuss findings with your team.
- 04IssueIssue the report and settings schedule, and answer questions during implementation.
Questions we are often asked
Which calculation tools do you use?
The calculation approach and any software model format are agreed at scoping. If you already maintain a network model, tell us which tool it uses so we can discuss whether to work within it.
Can you review settings that someone else calculated?
Yes. An independent review is often useful after network changes, new connections or an unexplained trip. The review states which data and criteria it was checked against.
How long does a coordination study take?
It depends on the size of the system, the number of operating cases and how complete the data is. We give a timeframe once the scope and data are clear.
Start a conversation
Tell us what your system is doing — and what you need it to do.
A few lines are enough to start. We will ask for drawings, settings or records later, through a channel agreed with you — there is no need to send them with your first message.