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Power Systems AnalysisCompleted Technical Study

Ofosu Islanded Solar Mini-Grid - ETAP Power-System & Protection Study

Independent ETAP reconstruction and technical assessment of the Ofosu standalone mini-grid, covering 24-hour PV-BESS operation, islanded short-circuit behaviour, generator and inverter-based fault contribution, device-duty screening, and representative feeder protection coordination.

Ofosu Islanded Solar Mini-Grid - ETAP Power-System & Protection Study project visual

Project image

Location

Ofosu, Nigeria

Period

2026

01 / Scope of Work

Work modelled, designed or delivered.

  1. 01

    Develop and review the Ofosu standalone mini-grid model in ETAP with PV generation, BESS/PCS, diesel generation, transformers and the 11 kV distribution feeder.

  2. 02

    Assess 24-hour islanded PV-BESS power sharing and network voltage performance.

  3. 03

    Evaluate generator-only islanded short-circuit performance.

  4. 04

    Screen protective-device duty under the generator-only fault condition.

  5. 05

    Assess islanded PV-BESS short-circuit behaviour and device duty.

  6. 06

    Evaluate representative downstream feeder selectivity using an LV breaker and upstream 11 kV overcurrent protection.

02 / Results & Findings

Results from the project work.

  1. 01

    Completed a 24-hour islanded operating assessment showing daytime PV support, surplus-energy absorption by the DC/BESS side and overnight BESS supply.

    Modelled result

  2. 02

    Observed solar generation reaching approximately 400 kW in the modelled daily profile while supplying the community load and network losses.

    Modelled result

  3. 03

    Evaluated generator-only short-circuit behaviour using the modelled 0.556 MVA diesel generator.

    Modelled result

  4. 04

    Identified materially lower islanded fault levels on the 11 kV feeder than on the LV buses, highlighting the importance of protection sensitivity in islanded operation.

    Modelled result

  5. 05

    Completed PV-BESS islanded short-circuit and device-duty assessment using the configured ETAP inverter-based resource models.

    Modelled result

  6. 06

    Demonstrated selective operation for a representative three-phase fault at the Load 1 bus: downstream CB12 cleared at 60 ms, Relay1 operated at 298 ms, and upstream CB11 opened at 358 ms.

    Modelled result

Ofosu / Modelled ETAP study

Power flow & protection.

Explore the modelled operating day and fault-response sequence.

Explore the study Close study

Islanded operation / ETAP Case 1

Follow the power through the day.

24 hourly samples
27 Jan 2026

Ofosu hourly solar, AC demand and DC source powerSolar peaks at 400 kilowatts at noon. AC demand stays near 197 to 201 kilowatts. The DC source supplies power overnight and absorbs power around midday. Exact values are in the hourly data table. -200 0 200 40000040812162023kW Hour of study day
12:00

Move the slider or point to the chart to inspect a sample.

Engineering decision

Check both directions of converter power flow: the DC side supplies the network overnight and absorbs surplus PV during the middle of the day.

Read Case 1 report Pages 12–13
Model assumptions & limits
  • 24 samples at one-hour intervals, using the report’s simultaneous AC/DC load-flow solution. Lines connect reported samples; this explorer does not run a new simulation.
  • Positive DC source power means supply; negative values mean absorption. Values are rounded for display.
  • The report uses the “Rated Voc & R” battery model but records zero battery energy and state of charge in its ESS summary. DC source power does not establish battery autonomy or usable storage capacity.
  • The report also records cable current-imbalance alerts. This view focuses on system power and does not show every study result.
View hourly data
Reported hourly values, in kW
HourSolar PVAC demandDC sourceLosses
00:000.0196.7204.27.6
01:000.0196.7204.27.6
02:000.0196.7204.27.6
03:000.0196.7204.27.6
04:000.0196.7204.27.6
05:0017.6196.9186.57.2
06:0055.9197.3147.96.5
07:00116.4197.987.56.0
08:00199.3198.85.96.3
09:00284.1199.7-76.67.9
10:00347.6200.3-137.59.8
11:00390.8200.7-178.611.4
12:00400.0200.8-187.311.8
13:00394.7200.8-182.311.6
14:00370.1200.5-158.910.6
15:00305.5199.9-97.28.4
16:00222.0199.0-16.46.6
17:00137.1198.167.16.0
18:0056.1197.3147.76.5
19:0017.6196.9186.57.2
20:000.0196.7204.27.6
21:000.0196.7204.27.6
22:000.0196.7204.27.6
23:000.0196.7204.27.6

Feeder protection / ETAP Case 4

See the order of fault response.

Three-phase fault
Load 1 bus

Ofosu reported protection sequenceEvent 1: CB12 at 60 milliseconds. Event 2: Relay1 at 298 milliseconds. Event 3: CB11 at 358 milliseconds, measured from fault inception.01002003004001. 60 ms2. 298 ms3. 358 msTime from fault inception (ms)
238 msCB12 to Relay1 separation
60 msRelay1 to CB11 breaker delay
Engineering decision

Coordinate the downstream breaker ahead of the upstream relay and breaker, preserving the upstream devices as backup in the reported sequence.

Read Case 4 report Page 12
Fault assumptions & limits
  • Representative symmetrical three-phase fault at the Load 1 bus. Timings come from the report’s Sequence-of-Operation Event Summary.
  • Bars show cumulative reported times from fault inception. The 60 ms upstream breaker delay is included in CB11’s 358 ms total.
  • This is a modelled coordination result, rather than a field test. Selecting a device explains the existing report; it does not recalculate protection settings.
View event data
Reported sequence of operation
DeviceRoleTime (ms)Current (kA)
CB12Downstream LV breaker603.594
Relay1Upstream 11 kV relay2980.131
CB11Upstream breaker358Not listed

Sites & Work Packages

Work covered by each site.

Site-level scope recorded for this assignment.

01

24-Hour Islanded Operation

Evaluated daily PV and BESS power sharing, network voltages, feeder loading and losses under standalone operation.

02

Short-Circuit & Device Duty

Assessed generator-only and PV-BESS islanded fault conditions using IEC 60909 and reviewed protective-device duty.

03

Protection Coordination

Coordinated a representative downstream LV breaker with the upstream 11 kV overcurrent relay and breaker, confirming selective operation through ETAP Sequence of Operation.

Technical Areas

Engineering methods and tools.

01

ETAP 24

Related projects

02

Time-Domain Load Flow

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03

Islanded Operation Assessment

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04

PV-BESS Power Flow Analysis

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05

IEC 60909 Short-Circuit Analysis

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06

Device Duty Screening

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07

Protection Coordination

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08

ETAP Star / TCC

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09

Sequence of Operation

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Related Disciplines

Mini-GridETAPSolar PVBESSDiesel GenerationIslanded OperationTime-Domain Load FlowShort CircuitIEC 60909Device DutyProtection CoordinationSelective Coordination

Project Evidence

Supporting project records.

Available for Ofosu Islanded Solar Mini-Grid - ETAP Power-System & Protection Study: Engineering Drawings · Reports / PDFs. Open an image for a closer view or select a document to read it.

01

Engineering Drawings

1 item

02

Reports / PDFs

6 items

PDF

Reports / PDFs

ETAP Single-Line Diagram - Full Resolution

Full-resolution PDF export of the ETAP single-line model used for the Ofosu mini-grid assessment.

Sep 2026

View document
PDF

Reports / PDFs

Case 1 - 24-Hour Islanded PV-BESS Operational Assessment

Time-domain assessment of 24-hour PV-BESS power sharing, network voltage performance, equipment loading and system losses under standalone operation.

Sep 2026

View document
PDF

Reports / PDFs

Case 2A - Generator-Only Islanded Short-Circuit Assessment

IEC short-circuit assessment of the islanded network with the modelled diesel generator acting as the principal rotating fault-current source.

Jul 2026

View document
PDF

Reports / PDFs

Case 2B - Generator-Only Device-Duty Assessment

Protective-device duty screening under the generator-only islanded short-circuit condition.

Jul 2026

View document
PDF

Reports / PDFs

Case 3 - Islanded PV-BESS Short-Circuit & Device-Duty Assessment

Islanded short-circuit and device-duty assessment evaluating the configured PV and BESS inverter-based fault-current contributions.

Jul 2026

View document
PDF

Reports / PDFs

Case 4 - Islanded Hybrid Feeder Protection Coordination

Representative feeder protection study demonstrating selective operation between downstream CB12 and the upstream Relay1/CB11 protection combination for a three-phase fault at the Load 1 bus.

Sep 2026

View document

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