Core Expertise
Power Systems Engineering
Short-circuit, protection coordination, arc flash and power quality are not disconnected services; they are overlapping analysis layers of the same power system model. A single impedance and topology model is built, and each analysis uses the output of the previous one as its input. This page explains both the facility safety and continuity decisions and the engineering method behind them.
Who it is for
- Industrial facilities with medium-voltage distribution and their own substation
- Plants with continuous or critical loads (process, data, healthcare)
- Operations planning equipment renewal, capacity increase or solar / BESS integration
- Businesses with electrical safety and compliance obligations
One Model, Four Layers
The analyses are run over a shared power system model rather than as separate reports. The impedance model of the grid, transformers, cables and motors is built once; the four layers answer different questions of that model.
The order is not arbitrary: short-circuit analysis gives the fault current, protection coordination attaches a clearing time to that current, and arc flash incident energy is derived from these two outputs. Power quality shares the same topology and impedance model.
Short-Circuit Analysis
How much current flows during a fault, and can the equipment withstand it?
Short-circuit analysis is the foundation of power systems engineering. The impedance model of grid, transformer, cable and motor contributions is built; symmetrical and asymmetrical fault currents at each busbar are calculated with the IEC 60909 method. These values are the shared input for breaker interrupting-capacity selection, protection settings and arc flash incident energy — which is why it is the first link in the chain.
- Three-phase and phase-to-earth fault currents per busbar
- Verification of equipment interrupting and short-time withstand capacity
- Motor contribution, X/R ratio and DC component assessment
- A validated impedance model carried into the following layers
Protection Coordination
In a fault, does only the faulted section trip, or does the whole facility go dark?
Protection coordination places the fault currents from the short-circuit model onto relay and breaker time-current curves. The goal is selectivity: the protective device nearest the fault should trip first, with the upstream stage held in reserve. Device curves are overlaid to verify coordination margins and clearing times for every fault scenario; setting recommendations rest on this verification.
- Time-current curve (TCC) coordination and selectivity across stages
- Relay setting recommendations: pickup, time dial and instantaneous
- Verification of clearing times against fault scenarios
- Backup coordination and control of protection blinding risk
Protection Coordination — Time-Current Curve
Sample Scenario
Time-current coordination curve (log-log)
- Downstream stage (near the fault)
- Upstream stage (backup)
- Available fault current
Two protection stages for a representative medium-voltage feeder. Because the upstream stage stays above and to the right of the downstream stage at every point, selectivity is preserved; the intersection of the fault-current line with the downstream stage (marked point) gives the clearing time that determines arc flash incident energy.
Sample scenario prepared with representative values; it cannot be used on its own for protection settings or safety decisions.
Arc Flash Analysis
What is the arc energy when working in front of a panel, and what protection is required?
Arc flash analysis is not just about printing labels or selecting PPE. Incident energy rests largely on the outputs of the two previous layers: the fault current from short-circuit analysis and the clearing time from protection coordination. The IEEE 1584 model combines these with equipment geometry (electrode configuration, conductor gap, enclosure type) and working distance to calculate incident energy and the arc flash boundary at each work point. A protection setting that shortens clearing time is often the most effective way to lower the PPE level; NFPA 70E ties these results to electrical safety procedures.
- IEEE 1584 incident energy (cal/cm²) and arc flash boundary calculation
- Analysis of the clearing-time / incident-energy relationship together with protection settings
- Approach distances and risk-reduction options per work point
- NFPA 70E-compliant labelling and work procedure input
Power Quality
How do harmonics, voltage events and reactive power affect production continuity and equipment life?
Power quality is assessed over the same grid topology and impedance model. Harmonic distortion, voltage events (sag / swell), imbalance and reactive power behaviour are examined with measurement and modelling together; compensation and filter needs are determined. Results are compared against EN 50160 and IEC 61000 limits to define compliance and the scope for improvement.
- Harmonic analysis (THD, individual harmonics) and resonance risk
- Voltage sag / swell and phase imbalance assessment
- Reactive power, compensation and harmonic filter needs
- Compliance check against EN 50160 / IEC 61000 limits
Assumptions and Limits
Analysis results depend on specific data and configuration assumptions; these limits are stated explicitly within the report scope.
Result accuracy depends on the single-line diagram and equipment data being current; analysis on data that does not match the field is invalid.
Short-circuit and arc flash results are sensitive to the grid supply strength (short-circuit power); if the value from the utility changes, the analysis is updated.
Protection coordination uses the actual characteristic curves of the existing devices; uncertainty increases for out-of-catalogue or legacy devices.
The analysis is for a specific operating configuration; switching scenarios such as parallel or split busbar operation are assessed separately.
Reference Frameworks
The principal standards and guides used in the analyses. Each layer is directly tied to its relevant framework.
- IEC 60909
- Method for calculating short-circuit currents in three-phase AC systems.
- IEC 60255
- Measuring relays and protection equipment — relay characteristics and performance requirements.
- IEEE 242 (Buff Book)
- Application guide for protection and coordination of industrial and commercial power systems.
- IEEE 1584
- Arc flash hazard calculations (2018 model) — incident energy and arc flash boundary.
- NFPA 70E
- Electrical safety in the workplace — risk assessment, working boundaries and PPE requirements.
- EN 50160
- Voltage quality characteristics of electricity supplied by public distribution networks.
- IEC 61000-4-30
- Power quality measurement methods — measurement classes for harmonics, voltage events and imbalance.
Defining the Power System Analysis Scope
Based on your single-line diagram, equipment data and protective device information, we come back with a scope proposal defining which analysis layers are needed and in what order they will be carried out.
Request an Analysis Scope Discussion