Three-phase apparent power
S = √3 × V × I ÷ 1000
- S
- apparent power in kilovolt-amperes (kVA)
- V
- line-to-line voltage in volts (V)
- I
- line current in amperes (A)
Knowledge
Engineering Reference
A concise reference for common commissioning and troubleshooting discussions. Values, settings and acceptance criteria must always be verified for the actual system.
Reference 01
Electrical and power systems
Use measured line values and the actual system configuration. The relationships below assume a balanced three-phase system and line-to-line voltage.
Three-phase real power
P = √3 × V × I × PF × η ÷ 1000
- P
- real output power in kilowatts (kW)
- PF
- power factor as a decimal
- η
- efficiency as a decimal; omit only when calculating electrical input power
kW, kVA and power factor
kVA describes voltage-and-current loading; kW describes useful real power. For a balanced load, kW is approximately kVA multiplied by power factor. Equipment ratings, harmonics and unbalanced conditions require project-specific review.
Synchronising
Before closing a generator breaker, voltage, frequency, phase sequence and phase angle must be compatible with the live bus. Automatic synchronisers and check-synchronising protection require verified settings and functional testing.
Load sharing and AVR fundamentals
Prime-mover governing primarily controls real-power sharing; excitation and voltage regulation primarily affect reactive-power sharing and voltage. Cross-current compensation, droop, communication links and power-management logic vary by installation.
Protection, blackout and recovery
Trip testing should prove the intended function without creating uncontrolled risk. A blackout-recovery test needs an approved sequence, stable starting supplies, verified protection and clear abort criteria. Simulated signals must not be confused with full end-to-end proof.
Electrical boundary: These simplified relationships support checking and estimation. Verify wiring configuration, phase balance, ratings, protection, efficiency basis and manufacturer information before operational use.
Use the three-phase power calculator or read the structured troubleshooting method.
Reference 02
Mechanical systems
| Check | Purpose | Typical evidence | Important boundary |
|---|---|---|---|
| Rotation | Confirm intended direction before loaded operation | Marked direction, witnessed bump test, driven-equipment check | Uncoupled testing may not prove the complete train |
| Lubrication | Establish correct oil, level, circulation and cleanliness | Approved lubricant, flushing record, pressure/flow indication | Manufacturer requirements and preservation state govern |
| Alignment | Control shaft and coupling condition | Cold alignment record, soft-foot result, final installation condition | Thermal growth and pipe strain may alter operating alignment |
| Flushing and cleanliness | Remove construction debris and commissioning contamination | Acceptance record, filter or strainer inspection, sample result | Acceptance method depends on system sensitivity |
| Pressure and leak testing | Demonstrate containment for the approved test boundary | Test pack, calibrated instruments, reinstatement record | Test medium, pressure and exclusions require engineered control |
| Temporary strainers | Protect equipment during initial circulation | Location register, differential pressure, inspection and removal record | Temporary items need visible ownership and removal criteria |
Pre-start mechanical check
- Installation and supports complete
- Guards and coupling condition verified
- Lubrication available
- Valves and line-up confirmed
- Temporary items identified
- Cooling and sealing services available
- Rotation risk assessed
- Instrumentation usable
- Vendor limits understood
- Abort criteria agreed
Mechanical boundary: This list does not define a test pressure, alignment tolerance, lubricant, cleanliness criterion or safe operating limit. Use approved project and manufacturer requirements.
Reference 03
Instrumentation and control
Loop checks
Prove the path from field device through marshalling, control logic, display and final element as applicable. Record range, engineering units, indication, action and any part simulated rather than physically proven.
Cause and effect
Test each initiating condition against the approved matrix, including sequence, delays, voting and reset behaviour. Confirm that inhibited or bypassed functions are controlled and restored.
Alarms, trips and interlocks
Verify alarm priority and acknowledgement separately from protective action. Permissives allow an action when conditions are satisfied; interlocks prevent or change action when defined conditions exist. Project terminology may differ.
Signal simulation
Simulation can prove logic safely, but it may exclude the sensor, cabling, process connection or final element. The test record should state exactly where the signal was introduced and what remained outside the test.
Recording test evidence
Record tag, range, units, test points, expected result, actual result, instrument identity, configuration, exceptions and acceptance. Preserve before-and-after settings for authorised changes. A screenshot without tag, time and test context is weak evidence.
Controls boundary: Changes to trips, voting, permissives, protection or safety functions require authorised project-specific control. A simulated test is not automatically equivalent to full functional proof.
Reference 04
Lifting equipment and rigging
Classify each item before selecting its controls. Equipment that lifts, supports, suspends, connects or measures a load may require different design information, markings, records, examinations and competent-person decisions.
| Equipment family | Representative examples | Review focus |
|---|---|---|
| Lifting machines and appliances | Pedestal, mobile and overhead cranes; hoists; lifting winches; workplace davits; forklifts; personnel or goods lifts; MEWPs; jacks | Identity, intended use, rated capacity or load chart, installed configuration, controls, brakes, limits and current status |
| Integral, supporting and load-carrier items | Hook and sheave blocks, hoist ropes and terminations, beam trolleys, runways, gantries, fixed padeyes and containers designed as loads for lifting | Define whether each item is part of the lifting machine, a structure or the load; then verify its design, support, marking, condition and operating limits |
| Lifting accessories | Wire-rope, chain and synthetic slings; shackles; accessory hooks; removable eyebolts; lifting and spreader beams; purpose-designed detachable lifting clamps and lifting-rated turnbuckles | Unique identification, manufacturer WLL or rated capacity, applicable SWL, size and grade, assembly, orientation, compatibility, damage and applicable discard criteria |
| Load-indicating and protective devices | Dynamometers, crane weighers, load cells, safe-load indicators and rated-capacity indicators | Range, units, calibration or verification status, configuration, functional checks, alarms, limiting functions and relationship to the load path |
| Marine, offshore and personnel-lifting arrangements | Lifeboat davits and blocks, man-riding winches, stabbing boards, diving or man-riding ropes, offshore containers and detachable lifting sets | Confirm whether LOLER, merchant-shipping, Flag, Class, MCA, owner or other equipment-specific requirements apply; control personnel lifting, emergency functions and the examination or testing basis separately |
Do not treat every control as the same activity
| Control | What it establishes | Important boundary |
|---|---|---|
| Pre-use check | A user check for identification, visible condition, assembly and obvious defects before operation | Does not replace planned inspection, maintenance or thorough examination |
| Inspection | A planned condition check with a defined scope, method and record | Is not automatically a thorough examination; the required competence and purpose must be clear |
| Maintenance | Work intended to preserve or restore condition and function | Does not by itself confirm examination status or fitness for a particular lifting arrangement |
| Thorough examination | A systematic assessment by a competent person for defects affecting safe use, under the applicable examination basis | Does not remove the need for pre-use checks, maintenance or defect control between examinations |
| Testing | Functional, load or proof evidence produced to an approved method when required by the applicable design, installation, repair or examination basis | Test loads, acceptance criteria and timing must never be inferred from a generic equipment summary |
| Calibration or functional verification | Evidence that an indicator or protective device responds correctly over its required range, units, configuration and alarm or limiting points | Is distinct from proof testing and thorough examination, although the competent person may consider its results when assessing the equipment |
Lifting boundary: Verify the actual equipment, intended use, applicable legislation, applicable equipment-specific examination scheme, manufacturer instructions, standards, markings, test basis and competent-person decisions. Quarantine equipment when identity, condition, rating or status is uncertain.
Use the LOLER Examination Reference for examination categories and limitations, and the Best Rigging Practices guide for lift planning and execution controls.
Reference 05
Completions and handover terminology
Terms vary between projects. The definitions below are practical distinctions, not universal contractual definitions.
| Term | Practical meaning | Do not assume |
|---|---|---|
| Mechanical completion | Defined construction and inspection scope is complete for an agreed boundary, subject to accepted exceptions | That the system is energised, functional or ready to start |
| Systems completion | Structured control of tags, records, boundaries, punch items and status gates | That database status alone proves field condition |
| Commissioning | Activities that demonstrate systems function and can be operated within the intended test envelope | That every commissioning phase or acceptance requirement is identical |
| Ready for commissioning | Project-defined status permitting specified commissioning activities | Unrestricted operation or start-up |
| Ready for start-up | Project-defined status after required commissioning, operational and safety reviews | That every close-out item is complete |
| Punch categories | Project rules for classifying incomplete or defective work by consequence and timing | A universal A/B/C definition |
| Turnover package | Evidence supporting transfer of a defined system and status | That document quantity equals evidence quality |
| PSSR | Pre-start-up safety review or the project’s equivalent authorised readiness review | One universal scope or regulatory basis |
| Handover evidence | Records, configuration, exceptions and acceptance demonstrating the state transferred | That a signature removes unresolved conditions |
Terminology boundary: Use the project’s approved completion, commissioning, PSSR and handover procedures for formal status decisions.
See systems completion and turnover, commissioning readiness, and safe handover and start-up preparation.