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Electrical engineering

Electrical engineering for resilient power infrastructure

Medium and low voltage distribution, switchgear, earthing and protection systems designed for operational continuity, safety and code compliance across building types.

Service scope

Electrical engineering at SEINZEN covers the full power distribution hierarchy from utility intake through medium voltage switchgear, transformers, low voltage distribution boards and final circuit protection. Design begins with load analysis, diversity assessment and fault level studies to establish infrastructure capacity and selectivity.

Earthing, bonding and lightning protection systems are developed alongside distribution design to meet touch voltage limits, equipment protection requirements and applicable IEC, BS and NFPA standards. Emergency and standby power interfaces are coordinated with mechanical and life safety systems from schematic stage.

Documentation is prepared in Revit electrical models with single-line diagrams, load schedules, cable sizing calculations and equipment specifications issued at defined project milestones. Protection coordination, voltage drop and short-circuit analysis support equipment selection and circuit design.

Construction support includes submittal review, site inspection and as-built verification to maintain design intent through installation, testing and commissioning.

Key engineering capabilities

  • Load analysis and diversity

    Connected and demand load calculations with diversity factors applied per occupancy type, operating schedule and metering strategy.

  • MV and LV distribution design

    Switchgear, transformers, busbar risers and distribution board layouts sized for fault levels, future expansion and maintenance access.

  • Protection coordination

    Discrimination studies, relay settings and fuse/breaker coordination to ensure selective fault clearance and minimise outage scope.

  • Cable sizing and routing

    Current-carrying capacity, voltage drop and fault withstand verification with routing coordinated through risers and ceiling zones.

  • Earthing and bonding

    Main earthing terminal, protective bonding and equipotential systems designed to applicable earthing standards and soil resistivity data.

  • Lightning protection

    Risk assessment, air terminal layout and down conductor systems per IEC 62305 or NFPA 780 depending on project jurisdiction.

  • Emergency and standby power

    Generator, UPS and static transfer switch interfaces coordinated with critical load schedules and mechanical plant requirements.

  • Energy metering and monitoring

    Sub-metering architecture, CT locations and BMS integration for operational energy management and tenant billing.

  • Harmonic and power quality

    Assessment of non-linear loads, THD limits and mitigation strategies for sensitive equipment and utility connection requirements.

Design and delivery methodology

  1. 01

    Utility and load assessment

    Incoming supply capacity, tariff structure and preliminary load estimates reviewed with client and utility provider to establish design basis.

  2. 02

    Schematic design

    Single-line diagrams, riser strategies and preliminary equipment selections issued for design team review and fault level confirmation.

  3. 03

    Detailed engineering

    Cable sizing, protection settings, earthing design and equipment schedules prepared with calculation reports to construction standard.

  4. 04

    Coordination and modelling

    Revit electrical models coordinated with architectural, structural and MEP disciplines through federated clash detection.

  5. 05

    Tender and construction issue

    Specifications, drawings and schedules issued for tender with submittal review procedures established.

  6. 06

    Testing and commissioning support

    Witness testing, insulation resistance verification and protection setting confirmation through energisation and handover.

Technical design criteria

  • Fault level analysis

    Prospective short-circuit current calculations at key nodes to verify switchgear rupturing capacity and protective device coordination.

  • Voltage drop and regulation

    Circuit voltage drop limits applied per applicable standard with cable sizing adjusted for starting currents and long feeder runs.

  • Selectivity and discrimination

    Time-current coordination curves analysed to achieve upstream/downstream selectivity and minimise fault impact on operational continuity.

  • Earthing system design

    TN, TT and IT system selection with earth electrode resistance, step and touch voltage verification for safe operation.

  • Transformer and switchgear specification

    Rating, impedance, cooling class and enclosure selection with loss evaluation for lifecycle cost and energy performance.

  • Busbar and riser design

    Vertical and horizontal busbar systems sized for fault withstand, thermal limits and future tenant load provision.

  • Surge protection coordination

    SPD type and location selection at service entrance, distribution boards and sensitive equipment interfaces.

  • Arc flash hazard assessment

    Incident energy calculations and PPE category determination where required by project safety management and applicable standards.

  • Power factor correction

    Capacitor bank sizing and harmonic filtering to meet utility power factor requirements and reduce demand charges.

  • Critical load segregation

    Essential, life safety and business-critical circuits identified and routed through resilient distribution paths with appropriate backup.

Engineering principles and calculation approaches

  • P = √3 × V × I × cos φ

    Variables

    P = three-phase active power (W); V = line voltage (V); I = line current (A); cos φ = power factor

    Application

    Three-phase load current estimation for cable sizing and protective device selection.

    Notes

    Apply design power factor; verify against measured data where retrofitting existing installations.

  • Vd = (2 × I × L × R) / 1000

    Variables

    Vd = voltage drop (V); I = design current (A); L = circuit length (m); R = conductor resistance (Ω/km)

    Application

    Single-phase circuit voltage drop verification against applicable limit percentages.

    Notes

    Include reactance for large cables and motor starting circuits; apply diversity where permitted.

  • I = P / (√3 × V × cos φ × η)

    Variables

    I = motor full-load current (A); P = shaft power (W); V = line voltage (V); cos φ = power factor; η = efficiency

    Application

    Motor circuit design for starters, cables and overload protection sizing.

    Notes

    Apply starting current multiplier for inrush verification; coordinate with mechanical equipment schedules.

  • Ik = c × Un / (√3 × Zk)

    Variables

    Ik = prospective short-circuit current (A); c = voltage factor; Un = nominal voltage (V); Zk = impedance at fault point (Ω)

    Application

    Fault level estimation at distribution boards and switchgear for rupturing capacity verification.

    Notes

    Use utility-provided source impedance; verify with manufacturer data for final switchgear selection.

  • R = ρ × L / A

    Variables

    R = earth electrode resistance (Ω); ρ = soil resistivity (Ω·m); L = electrode length (m); A = effective cross-section (m²)

    Application

    Preliminary earth electrode resistance estimation for earthing system design.

    Notes

    Confirm with site measurement; consider seasonal variation and parallel electrode effects.

Final design values must be determined using project-specific inputs, applicable standards, manufacturer data and engineering judgement.

BIM, Revit and integrated design

  • Electrical distribution is modelled in Revit with panels, busbar, cable trays, conduits and equipment represented at defined LOD for coordination and quantity take-off.

  • Circuit data including load, cable size, protective device rating and panel schedule information is linked through shared parameters and schedule views.

  • Single-line diagram information is cross-referenced to model elements with panel and circuit tagging consistent across drawings and schedules.

  • Federated coordination resolves clashes with structural elements, HVAC ductwork and plumbing risers before construction issue, with responsibility matrices documenting resolution.

International standards and codes

IEC 60364

Standard

Low-Voltage Electrical Installations

Application area

International electrical design

Project relevance

Fundamental principles, protection against shock, overcurrent and overvoltage for building installations.

BS 7671

Standard

Requirements for Electrical Installations (IET Wiring Regulations)

Application area

UK electrical installations

Project relevance

Design, erection and verification requirements for low voltage systems in UK and aligned projects.

NFPA 70

Standard

National Electrical Code

Application area

US and international reference

Project relevance

Wiring methods, overcurrent protection and grounding for projects under NEC jurisdiction.

IEC 61439

Standard

Low-Voltage Switchgear and Controlgear Assemblies

Application area

Switchboard design

Project relevance

Assembly verification, temperature rise limits and short-circuit withstand for panel boards.

IEC 62305

Standard

Protection Against Lightning

Application area

Lightning protection design

Project relevance

Risk assessment, protection level selection and LPS component requirements.

IEEE 1584

Standard

Guide for Performing Arc-Flash Hazard Calculations

Application area

Electrical safety

Project relevance

Incident energy calculation methodology for arc flash labelling and PPE determination.

IEC 61000

Standard

Electromagnetic Compatibility

Application area

Power quality

Project relevance

Emission and immunity limits for equipment in shared electrical environments.

EN 50522

Standard

Earthing of Power Installations Exceeding 1 kV a.c.

Application area

MV earthing

Project relevance

Earthing design for medium voltage substations and transformer installations.

IEC 60076

Standard

Power Transformers

Application area

Transformer specification

Project relevance

Rating, insulation, losses and testing requirements for distribution transformers.

NFPA 110

Standard

Standard for Emergency and Standby Power Systems

Application area

Emergency power

Project relevance

Generator installation, transfer equipment and testing requirements for life safety loads.

IEC 60502

Standard

Power Cables with Extruded Insulation

Application area

Cable specification

Project relevance

Voltage rating, insulation type and testing for power cable selection.

EN 50160

Standard

Voltage Characteristics of Electricity Supplied by Public Distribution Networks

Application area

Supply quality

Project relevance

Voltage tolerance and supply quality parameters for equipment compatibility assessment.

Applicable standards depend on the project location, building use, authority having jurisdiction, employer requirements and contract documents. The current adopted edition must be confirmed at the beginning of each project.

Project deliverables and documentation

  • Electrical load schedule

    Connected and demand loads by panel, floor and tenancy with diversity factors documented.

  • Single-line diagrams

    MV and LV distribution hierarchy from utility intake through final distribution boards.

  • Fault level and discrimination study

    Short-circuit analysis and protective device coordination curves for switchgear and panel selection.

  • Cable sizing calculations

    Current capacity, voltage drop and fault withstand verification for major circuits.

  • Earthing and bonding design

    Earth electrode layout, main bonding and supplementary bonding details with resistance calculations.

  • Lightning protection design

    Risk assessment, air terminal layout and down conductor routing where applicable.

  • Equipment schedules

    Transformer, switchgear, panel board and major equipment schedules with technical data.

  • Revit electrical models

    Coordinated electrical models with panels, cable trays, conduits and equipment at defined LOD.

  • Performance specifications

    Technical specifications for switchgear, cables, earthing materials and installation prepared for tender.

  • Riser and routing drawings

    Electrical riser diagrams and cable routing layouts coordinated with other MEP services.

  • Emergency power design

    Generator, ATS and critical load distribution for life safety and essential services.

  • Testing and commissioning schedules

    Insulation resistance, continuity and protection setting verification procedures.

Quality control and verification

  • Load calculations reviewed against architectural programme and equipment schedules before schematic issue.

  • Fault level and discrimination studies verified against utility data and manufacturer time-current curves.

  • Cable sizing independently checked for current capacity, voltage drop and fault withstand compliance.

  • Earthing design validated against soil resistivity data and touch voltage limits.

  • Model and drawing tag consistency verified across single-line diagrams, schedules and Revit models.

  • Submittal deviations documented and resolved before installation approval.

Applicable project types

  • Commercial towers with MV intake, tenant distribution and sub-metering infrastructure.

  • Healthcare facilities requiring segregated essential, life safety and normal power systems.

  • Data centres with high power density, redundant feeds and UPS integration.

  • Mixed-use developments with multiple tenancy types and phased energisation strategies.

  • Industrial facilities with motor loads, power factor correction and process power requirements.

  • Hotel and hospitality projects with guest room distribution, kitchen power and emergency systems.

Frequently asked questions

  • How is medium voltage equipment selected for a new building?

    MV switchgear selection follows fault level analysis at the point of common coupling, load forecast and utility connection requirements. Ring main units, switchboards and transformer ratings are coordinated with the utility provider and future expansion provisions defined in the basis of design.

  • What earthing system is typically used for commercial buildings?

    System type depends on utility supply configuration and local regulations. TN-S and TN-C-S systems are common in UK and European projects; TT systems may apply where utility earth cannot be relied upon. Earth electrode design is verified against measured soil resistivity.

  • How are emergency and life safety loads segregated?

    Life safety loads are identified per applicable fire and electrical codes and routed through dedicated distribution boards with appropriate backup duration. Essential and business-critical loads are segregated based on project operational requirements and client brief.

  • Is arc flash analysis included in electrical design?

    Arc flash hazard assessment is provided where required by project safety management, client policy or applicable standards. Incident energy calculations support equipment labelling and PPE category determination for maintenance personnel.

  • How does electrical design integrate with BMS and metering?

    Sub-metering CT locations, communication protocols and panel interfaces are defined during detailed design. Energy monitoring points align with operational management requirements and tenant billing structures.

Discuss electrical engineering scope

Contact our electrical engineering team to review distribution strategy, load analysis or protection coordination for your project.

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