Technical Hub
Engineering glossary
Defined terms used across our standards guides, studies and test reports.
- Apparent charge
- Charge which, if injected at the terminals of a test object, would give the same reading as the PD pulse; expressed in pC (IEC 60270).
- Arc flash
- Release of thermal and radiant energy from an electric arc between conductors or to earth.
- C-rate
- Battery charge or discharge power relative to its energy capacity; 0.5C means full discharge in two hours.
- Capacitive charging current
- Current drawn by the capacitance of an energised cable or line with no load connected.
- Cpk
- Process capability index comparing process spread with specification limits.
- CT knee-point voltage
- Point on a CT excitation curve where a 10% voltage increase causes a 50% increase in excitation current.
- Design verification
- Verification under AS/NZS 61439 that an assembly design meets the standard, by test, comparison or assessment.
- DNSP
- Distribution Network Service Provider.
- Earth potential rise (EPR)
- Voltage rise of an earthing system relative to remote earth during an earth fault.
- Fault level
- Short-circuit power at a point in the network, usually expressed in MVA.
- Form of separation
- Internal division of an LV assembly into compartments (Forms 1–4) to limit contact and fault propagation.
- GIS
- Gas-insulated switchgear — metal-enclosed switchgear insulated by pressurised gas, typically SF6.
- Hold point
- Stage in an ITP beyond which work must not proceed without documented release.
- Icw
- Rated short-time withstand current of an assembly or busbar for a stated duration.
- Incident energy
- Thermal energy at a working distance from an arc, in J/cm² or cal/cm².
- ITP
- Inspection and Test Plan — the controlled schedule of inspections, tests, hold and witness points.
- Knee-point
- See CT knee-point voltage.
- NCR
- Non-conformance report recording a deviation from requirements and its disposition.
- OTIF
- On time, in full — delivery performance measure.
- Partial discharge (PD)
- Localised electrical discharge that only partially bridges insulation between conductors.
- Routine verification
- Checks performed on each manufactured assembly before dispatch under AS/NZS 61439.
- Soil resistivity
- Electrical resistivity of soil (Ω·m), measured on site and modelled in layers for earthing design.
- Step voltage
- Voltage between two points on the ground surface one metre apart during an earth fault.
- THD
- Total harmonic distortion — RMS of harmonic components relative to the fundamental.
- TNSP
- Transmission Network Service Provider.
- Touch voltage
- Voltage between an earthed structure and a point on the ground where a person may stand while touching it.
- UHF PD detection
- Detection of PD by the ultra-high-frequency signals it radiates inside GIS enclosures.
- VLF testing
- Very-low-frequency (typically 0.1 Hz) AC withstand and diagnostic testing of cables.
- Wenner method
- Four-electrode method for measuring soil resistivity with equal electrode spacing.
- X/R ratio
- Ratio of reactance to resistance at a fault location; drives DC offset and peak fault current.
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