Why is an SLD important before a switchboard is manufactured?

The Single Line Diagram forms the basis for switchboard design, equipment selection, protection coordination and system installation. Many project delays and manufacturing changes result from incomplete or poorly reviewed drawings, and careful engineering review reduces those risks before fabrication begins. Common mistakes found at review include missing fault ratings and incorrect breaker sizes.

Does a Single Line Diagram include solar and generators?

Yes. Modern Single Line Diagrams typically include utility supplies, generators, solar PV systems, battery storage and transfer systems where applicable. Showing every source on one drawing makes it possible to check equipment ratings and protection coordination across the whole installation rather than only the utility incomer, which matters on sites with mixed generation.

Who should approve a Single Line Diagram?

Qualified electrical engineers, consultants and project stakeholders should review and approve the drawing before manufacturing begins. Paneltech engineers also review existing Single Line Diagrams to verify equipment ratings, fault levels, protection coordination and overall switchboard suitability before fabrication. This review stage is normally where missing fault ratings and incorrect breaker sizes are picked up.

Article · Published 25 July 2026 · 6 min read · By Ruth

Single Line Diagram Kenya: 2026 Engineering Guide and Specs | Paneltech Systems Kenya

Looking for a single line diagram Kenya engineers rely on? Learn how to read an SLD, verify incomers, breaker ratings, interlocks, and earthing before approving your switchboard design.

A Single Line Diagram (SLD) is the foundation of every electrical power distribution project. Whether you're installing a new factory, upgrading a commercial building, constructing a hospital, commissioning a solar power system, or expanding a data centre, the switchboard cannot be properly designed until the Single Line Diagram has been reviewed and approved.

Unfortunately, many project owners sign off on an SLD without fully understanding what it shows. Missing breaker ratings, incorrect busbar sizing, inadequate fault levels, or poorly coordinated protection may only become apparent after the switchboard has been manufactured—when design changes become expensive and project delays unavoidable.

Understanding single line diagram Kenya projects depend on helps engineers, consultants, contractors, and facility managers verify that the proposed electrical system is safe, compliant, and capable of meeting both present and future operational demands.

In Kenya, reviewing an SLD is particularly important because electrical systems often include:

KPLC utility supplies
Diesel standby generators
Solar PV systems
Battery Energy Storage Systems (BESS)
Automatic Transfer Switches (ATS)
APFC panels
Variable Frequency Drives (VFDs)
Energy monitoring systems

At Paneltech Systems Ltd, we prepare, review, and manufacture switchboards directly from approved Single Line Diagrams, ensuring every panel complies with recognised engineering standards and project requirements. Learn more about our engineering expertise at about, explore our products at products, or contact our engineering team through contact.

What Is a Single Line Diagram?

A Single Line Diagram (SLD) is a simplified drawing that represents an electrical power distribution system using single lines and standard electrical symbols. It shows how electrical power flows from the incoming supply to transformers, switchboards, distribution boards, generators, loads, and protective devices.

Instead of showing every conductor individually, an SLD presents the overall electrical architecture in a clear, simplified format.

Typical components include:

Utility incomers
Transformers
Main switchboards
Busbars
Circuit breakers
Distribution boards
Generators
Solar systems
Battery storage
Earthing arrangements

Why an SLD Matters in Kenya

A properly prepared Single Line Diagram allows engineers to verify protection, coordination, equipment ratings, and future expansion before manufacturing begins. Correcting mistakes on paper is significantly easier and less expensive than modifying completed switchboards.

An approved SLD supports:

Safe system design
Faster project delivery
Accurate equipment selection
Regulatory compliance
Easier maintenance

Every major electrical installation should have an up-to-date SLD.

What Should You Check Before Approving an SLD?

Before approving a Single Line Diagram, verify the incoming supply arrangement, transformer ratings, switchboard fault levels, protective device ratings, cable sizes, earthing method, interlocking logic, and provisions for future expansion. The SLD should accurately represent how the completed electrical installation will operate under both normal and fault conditions.

Key items include:

Utility incomer
Main breaker ratings
Busbar current rating
Fault level
ATS arrangement
Generator integration
Earthing system
Protection coordination

Single Line Diagram Specifications Table

An SLD should contain all critical design information needed to manufacture, install, test, and commission the electrical system safely.

Specification	Typical Requirement
System Voltage	415V AC
Frequency	50 Hz
Incoming Supply	KPLC / Generator / Solar
Busbar Rating	Project Specific
Fault Rating	25kA–65kA (Project Dependent)
Earthing System	TN-S / TN-C-S / TT
Protection Devices	MCCB / ACB / MCB
Metering	Multifunction Energy Meter
Standards	IEC 61439 / IEC 60364
Drawing Format	Single Line Diagram (SLD)

Understanding the Incoming Supply

The SLD should clearly identify the source of electrical power and how it enters the installation. This information determines switchboard ratings, protection settings, and system configuration.

Common incoming supplies include:

KPLC utility supply
Diesel generators
Solar PV systems
Battery Energy Storage Systems
Dual utility incomers

Every source should be clearly labelled and rated.

Reading Circuit Breaker Ratings

Every protective device shown on the SLD should include its current rating, interrupting capacity, and protective function. These values ensure the switchboard can safely withstand expected operating and fault conditions.

Typical information includes:

Current rating (A)
Breaking capacity (kA)
Trip characteristics
Protection settings
Device type

Incorrect breaker selection can compromise system safety.

Understanding Busbars

The busbar system distributes power throughout the switchboard and must be correctly sized for continuous current, future expansion, and prospective fault levels.

Busbar information typically includes:

Material
Current rating
Fault withstand rating
Arrangement
Segregation

Paneltech designs LV switchboards with engineered busbar systems through low-voltage-panels.

ATS and Generator Interlocking

Where standby generators are installed, the SLD should clearly show Automatic Transfer Switch (ATS) arrangements and electrical or mechanical interlocking that prevents unsafe parallel operation unless specifically designed.

Typical ATS information includes:

Utility incomer
Generator incomer
ATS operation
Manual bypass
Interlocking method

Proper interlocking improves operational safety.

Solar and Battery Integration

Modern SLDs increasingly include renewable energy systems alongside traditional utility supplies. These connections should be clearly shown to ensure safe operation and protection coordination.

Common renewable energy components include:

Solar inverters
Battery storage
Hybrid inverters
AC combiner panels
DC isolation

Paneltech also designs solar-ready distribution panels through #solar-ac-db-combiner.

Earthing and Bonding

The earthing arrangement shown on the SLD is essential for personnel safety and fault protection. Every switchboard should clearly indicate the earthing system used throughout the installation.

Common earthing systems include:

TN-S
TN-C-S
TT

The SLD should also identify:

Earth bars
Protective conductors
Bonding arrangements

Protection Coordination

Protection coordination ensures that only the device closest to a fault disconnects, minimising disruption to the remainder of the electrical installation.

An SLD should support:

Selective coordination
Discrimination studies
Time-current analysis
Protective relay settings

Proper coordination improves system uptime.

Planning for Future Expansion

A well-designed Single Line Diagram should accommodate future electrical growth without requiring complete replacement of the switchboard.

Future provisions may include:

Spare feeders
Larger busbars
Additional generators
Solar expansion
Battery storage
Extra metering

Planning ahead reduces future upgrade costs.

Environmental Considerations in Kenya

Switchboards represented on the SLD should also be specified with enclosure ratings appropriate for their installation environment.

Nairobi

Typical applications:

Commercial buildings
Office developments
Mixed electrical loads

Coastal Kenya

Typical requirements:

IP65 enclosures
Corrosion-resistant construction

Industrial Areas

Typical requirements:

Dust protection
Heavy-duty switchboards
High fault ratings

Environmental conditions should influence final panel specifications.

Common SLD Review Mistakes

Many project delays and manufacturing changes result from incomplete or poorly reviewed Single Line Diagrams. Careful engineering review reduces these risks before fabrication begins.

Common mistakes include:

Missing fault ratings
Incorrect breaker sizes
No generator contribution
No future spare capacity
Missing metering
Incorrect earthing details
No protection coordination

Professional review ensures the drawing accurately reflects project requirements.

Standards and Compliance

Single Line Diagrams should support electrical systems designed in accordance with recognised international standards and Kenyan regulatory requirements.

Relevant standards include:

IEC 61439 – Low Voltage Switchgear Assemblies
IEC 60364 – Electrical Installations
IEC 60947 – Low Voltage Switchgear and Controlgear
BS EN standards for switchgear
EPRA electrical requirements applicable in Kenya

Why Choose Paneltech Systems Ltd?

Paneltech Systems Ltd reviews Single Line Diagrams before manufacturing to ensure switchboards meet project specifications, operational requirements, and recognised engineering standards.

Our specialised services include:

Low Voltage Switchboards
Single Line Diagram Review
Motor Control Centres (MCCs)
APFC Panels
ATS / MTS Systems
VFD Control Panels
Energy Monitoring Panels
PLC Automation Panels
Electrical Engineering Consultation
Custom Panel Manufacturing

Explore our engineering solutions through home-main, access technical resources through knowledge-site, discover residential solutions through paneltechhomes, or visit home1.

Frequently Asked Questions

Understanding a Single Line Diagram helps ensure electrical systems are correctly designed before manufacturing begins.

What is a Single Line Diagram?

It is a simplified drawing showing how electrical power flows through an installation using standard electrical symbols and single-line representations.

Why is an SLD important?

It forms the basis for switchboard design, equipment selection, protection coordination, and system installation.

Who should approve an SLD?

Qualified electrical engineers, consultants, and project stakeholders should review and approve the drawing before manufacturing begins.

Does an SLD include solar and generators?

Yes. Modern Single Line Diagrams typically include utility supplies, generators, solar PV systems, battery storage, and transfer systems where applicable.

Can Paneltech review an existing Single Line Diagram?

Yes. Paneltech engineers review SLDs to verify equipment ratings, fault levels, protection coordination, and overall switchboard suitability before fabrication.

Contact Paneltech Systems Ltd

Powering Kenya's Future with Reliable Electrical Solutions

Email: [email protected]

Phone: 0799 531765

Location: Nairobi, Kenya

Website: https://paneltechsystems.co.ke/