Power System Analysis

Load Flow is the backbone of power analysis, establishing equipment suitability based on loadings, voltages, and through currents. 

We validate performance across all realistic operational conditions; normal operation, contingency conditions, quasi-dynamic and/or unbalanced, ensuring system resilience.

Key Assessments

·        Equipment Loading Verification: Assess primary asset ratings.

• Voltage Profile Analysis: Ensure node voltages stay within statutory limits.

• System Losses Assessment: Determine equipment type losses as well as total system losses.

• Transformer Optimisation: Establish optimum transformer parameters, tap numbers and off-load tap positions

• Loading Optimisation: Evaluate equipment loadings to maximise utilisation and propose alternatives if required.

• Reactive Power Compensation: Assess and establish if there is a need and size based on the use case.

Short-circuit analysis is pivotal to ensure all equipment can handle potential fault currents and switchgear can safely isolate faults. Grounded Energy assess against a variety of standards depending on the specific application, including IEC 60909, IEC 61363, and G74

Key assessments

• Switchgear: Make and break duties.

• Bus/switchboard: RMS and Peak withstand ratings.

• Transformers: withstand ratings, impedance selection for limiting faults levels

• Cables: Conductor and sheath/armour ratings.

• NERs/AUXTX: Impedances and Neutral rating assessment (more specific to sites with high capacitive cable charging effects e.g., offshore wind)

Detailed Time-Domain Modelling: For sites with large transformers, embedded generation, or high X/R ratios, typical short-circuit assessments sometimes require a more granular approach. Grounded Energy conducts time-domain analysis (RMS or EMT) to ensure proposed equipment can handle asymmetrical duty and sufficient thermal ratings.

Modern electrical networks consitute increasingly of non-linear loads, such as variable speed drives (VFDs), LED lighting, and battery and renewable energy inverters. Power quality issues are a major concern throughout the industry. Grounded Energy conducts comprehensive Harmonic Analysis to identify distortion levels, predict resonance issues, and ensure your asset complies with requirements.

Standards and Compliance

We assess to strict industry recommendations and standards: ENA Recommendation G5/5 (and legacy G5/4) & IEC 61000-3-6.

Key assessments:

• Loci generation: Determine impedance loci for connection points by considering all realistic operational scenarios for electrically close infrastructure.

• Frequency Scans: Essentially an impedance ‘before and after shot’ at specific nodes on the system when plant is being connected/removed. This aids in identifing series and/or parallel resonances which if left unaddressed can pose signficant ramifications.

• Incremental Harmonics: Establishes the contributions of a site to the grid and are assessed against apportioned limits provided by the DNO/TO

• Total Harmonics: Determines the harmonic levels once the Incremental and existing background harmonics at the connection point are amalgamated. Assessed against apportioned limits provided by the DNO/TO

• THD: The ratio of the sum of the powers of all harmonic components relative to the power of the fundamental frequency. This is compared with limits dependant on the voltage level and the applicable standard.

• Equipment Rating: Verifying transformers and cables have the headroom to accommodate harmonics.

• Voltage Gain Factors: Assists in visualising the amplification/reduction of harmonics due to the connection of a site as well as variance due to alternative operational scenarios.

• Mitigation & Filter Design: If harmonic limits are exceeded and/or severe resonances are identified, we provide the solution. We provide filter specifications: single and double tuned filters, C-type. We can also shift resonances by detuning equipment e.g. capacitor banks. For all mitigations, the harmonic assessment is repeated to demonstrate the solutions merit.

Voltage disturbance studies assess the impact your equipment has on grid voltage stability. Whether you are energising a transformer, starting a motor, connecting renewables and/or battery storage, we have it covered.

Key assessments

• Step Voltage Assessment: Assesses the effects of site discoonection on the connection point voltage.

• Transformer Inrush: Assess energisation events and provide the P28 classification and sequencing where required.

• Flicker Calculations: Determine Pst and Pit values for disturbing loads and assess against planning levels

• Power Swing: Typically for BESS sites to determine if the specified ramp rates are suitable without breaching voltage bounds.

• Motor Starting Analysis: Calculate voltage sag for Direct-on-line/Soft-start sequences.

• Mitigations: If required Grounded Energy can determine the most suitable mitigation equipment dependant on the situation. Soft Starters, Pre-insertion Resistors, VSDs, and Point-on-Wave switching devices to reduce inrush currents and voltage dips.

When loads are not evenly distributed across each phases, it creates voltage unbalance. Excessive unbalance creates negative phase sequence currents. This is detrimental and can lead to overheating in motors and generators and mal-triping of protection relays.

P29 is typically viewed as an ‘LV issue’. However, as more single phase technologies connect at higher voltages this is likely to be increasingly not the case: e.g.  EV Charging Hubs, Large Heat Pumps

P29 also is mandatory for specialist high-voltage applications :Rail Electrification, Electric Arc Furnaces, Rural Networks

Key Assessments

• Calculation of Voltage Unbalance Factor (%).

• Negative Phase Sequence (NPS) voltage and current analysis.

• Load balancing strategies and transposition recommendations.(e.g. balancers, Scott-T Transformers)