Protection Coordination Study
Relay coordination, time-current curve analysis, settings development, and selectivity verification for reliable power system protection.
What is Protection Coordination?
Protection coordination ensures that protective devices (relays, fuses, breakers) operate in the correct sequence to isolate faults with minimal impact to the system. Proper coordination prevents unnecessary outages, limits equipment damage, and maintains service continuity beyond the faulted section.
A coordination study evaluates device characteristics, fault currents, and operating times to verify selectivity—meaning upstream devices allow downstream devices to clear faults first. Time-current curves (TCCs) graphically demonstrate coordination margins and identify miscoordination risks.
This study is critical for new installations, equipment changes, interconnection projects, and compliance with protective relaying standards. It informs settings development, device selection, and operational practices.
When This Study Is Required
New Generator/BESS Interconnection
Protection scheme development and utility coordination
Facility Expansion or Upgrades
New feeders, transformers, or equipment requiring protection
Relay Replacement or Settings Changes
Modernization, upgrades, or technology changes
Miscoordination or Protection Issues
Addressing operational problems and compliance gaps
What eGridSync Delivers
One-line diagram review and protection zone identification
Short-circuit analysis (if not already completed)
Device characteristic data collection and validation
Time-current curve (TCC) development showing coordination
Relay settings calculations and recommendations
Selectivity verification and margin documentation
Miscoordination identification and mitigation options
Settings tables and relay programming files (where applicable)
Final coordination report and TCC plots
Inputs Required (Data Request Checklist)
| Item | Examples | Why Required |
|---|---|---|
| One-line diagram | Protection zones, relay locations, device types | Define coordination scope |
| Short-circuit currents | Max/min fault duties at key buses | Required for all coordination studies |
| Relay types and models | Manufacturer, model, firmware version | Characteristic curves and capabilities |
| CT/PT ratios | Current/voltage transformer ratios | Convert primary to secondary values |
| Existing settings (if applicable) | Current relay settings files | Baseline and validation |
| Protection philosophy | Design criteria, coordination time intervals | Alignment with operational requirements |
Key Coordination Principles
Selectivity
Downstream devices operate before upstream devices allow time delay
Time Interval
Adequate margin (typically 0.2-0.4s) between device operations
Coordination Margin
Safety factor accounting for tolerances and uncertainties
Sensitivity vs Speed
Balance fault detection with clearing speed requirements
Common Coordination Issues
Insufficient Time Margin
Upstream and downstream curves too close causing potential misoperation
Curve Crossover
Protection curves intersect losing selectivity at certain fault levels
Settings Not Updated After Changes
System modifications invalidating existing coordination requiring settings revision
Inadequate Short-Circuit Data
Missing or incorrect fault currents causing improper coordination analysis
Frequently Asked Questions
What is protection coordination?
Ensuring protective devices operate in proper sequence to isolate faults with minimal impact.
Do you create TCC plots?
Yes—time-current curves showing coordination margins.
Can you support relay commissioning?
Yes—settings files and field support if needed.
What software do you use?
Industry-standard tools for coordination and arc flash analysis.
How does this relate to PRC standards?
Coordination supports PRC-005 maintenance and PRC-027 performance requirements.
What if coordination cannot be achieved?
We document constraints and recommend alternatives (adjust settings, change device types, add equipment).
Do you verify existing settings?
Yes—settings review and validation against current system conditions.
Can you coordinate with utility protection?
Yes, if utility provides data; otherwise we coordinate to the POI.
What deliverables do you provide?
TCC plots, settings tables, coordination report, and settings files.
How long does a coordination study take?
Typically 2-4 weeks depending on system size and complexity.
Ready for Protection Coordination Analysis?
Contact eGridSync for relay coordination and settings development support.