Glossary terms beginning with H

Terms used within Transpower
Click one of the letters above to go to the page of all terms beginning with that letter.
hand control

Control by hand, that is, not automatic.

handling SF6 gas

A term used in this standard to include the filling, topping up, recovering and removal of SF6 gas for electrical equipment.

hanger bracket

General term for the component used to attach an insulator set or earthwire set to a tower. The term includes fabricated hanger brackets, solid swivels, hanger shackles and twisted barrel tongues.

harm

Any illness, injury, or both; and includes physical or mental harm caused by work-related stress.

harmonic filter

A device which is designed to suppress harmonic currents and voltages from being injected into the power system.

harmonic frequencies

Integral multiples of the fundamental frequency causing distortion of the sinusoidal alternating waveform.

Haywards frequency control

Controls the amount of HVDC transferred if the Wellington area becomes split from the rest of the North Island system. Normally disabled, can be manually selected. Normally set to 50 Hz but can be varied to help reparalleling.

Haywards special RTU

RTU located at Transpower's Haywards substation for the purpose of monitoring the South Island-to-North Island power transfer runback action of the HVDC link and reporting htis state to the FRED Master at SCH.  The RTU is located in position P170 in the main relay room.

Haywards voltage stabiliser

A very fast acting control at Haywards to prevent ac system collapse after faults by reducing HVDC power transfer. Normally enabled.

hazard

An activity, arrangement, circumstance, event, occurrence, phenomenon, process, situation, or substance (whether arising or caused within or outside a place of work) that is an actual or potential cause or source of harm or significant property damage. It includes a situation where a person's behaviour may be the actual or potential cause or source of harm to the person or another person.

hazard (environmental adverse effects)

Any activity, arrangement, circumstance, event, occurrence, phenomenon, process, situation, or substance that is an actual or potential cause or source of adverse effect to the environment. "Effect" as defined in the Resource Management Act. Any potential or probable, harmful, temporary or permanent, past present or future, acute, or chronic, effects, or any cumulative effects which arise over time or in combination with other effects. [Resource Management Act 1991].

hazard (personal safety)

Any activity, arrangement, circumstance, event, occurrence, phenomenon, process, situation, or substance that is an actual or potential cause or source of harm; and hazardous has a corresponding meaning. [Health and Safety in Employment Act 1992].

hazard level

A rating of the hazard of pressure equipment determined from the pressure, volume and  contents of the equipment. It is determined from AS 4343.

hazard zone

The area around an earthing system within a contour joining all points of earth potential equal to the maximum acceptable voltage (where the voltage exceeds the specified value for the specified time) outside which zone no special precautions need be taken to protect telecommunications plants or personnel within the area.

headclamp

The clamp that connects the portable earth to the earthing horn or conductor.

headgate

A gate controlling the "head" of water behind a dam (known as an intake gate) or at the upper end of a canal (known as an inlet gate). In a hydro power station, the gate controlling the entry of water to the pipeline or penstock supplying the hydraulic turbine/s.

headwater

Also referred to as "headpond", is that part of the reservoir created by the dam which is adjacent to the dam structure, and from which the water is drawn down the penstocks.

headwater level

The level of water in the headwater.

helical fitting

Fittings for overhead lines and guys consisting of sets of rods each of which has been formed into an open helix. Each fitting normally has the same direction of lay as the outer strands of the conductor or guy strand to which it is applied. These fittings are more often referred to by their trade names "preformed", "heliformed" or "superformed".

helicopter live line work

Where any helicopter, or personnel supported by an air craft, are positioned within 5 m of live line components, that helicopter is engaged in helicopter live line work and is required to comply with helicopter live line work standards.

hermetically-sealed surge arrester

A surge arrester which is non-breathing, that is, so sealed that there can be no significant interchange between its contents and the external atmosphere.

hermetically-sealed transformer

A transformer which is non-breathing, that is so sealed that there can be no significant interchange between its contents and the external atmosphere.

HF

High frequency, 3 to 30 MHz.

HGAS

Term used to define a hydrogen gas detection system indicator panel which includes the components and devices connected to the indicator panel being gas monitors, gas alarm sounders and alarm lights and alarm signalling equipment for both remote and local alarms Devices such as automatic gas isolation valves which are activated by the system are to be recognised as part of the system.

hi-pot testing

A method of live testing of high voltage insulators and bushings in situ.

hidden appendix

Supplementary material that supports the standard, but that is confidential to Transpower. Such appendices are not released with the standard, but are available on the Intranet.

high potential testing

A method of live testing of high voltage insulators and bushings in situ.

high pressure water jetting

The use of high pressure water with or without the addition of chemicals or abrasives to remove unwanted matter from various surfaces.

high voltage

Depending on context, can be one or more of: The set of voltage levels in excess of low voltage (LV); In terms of the Electricity Regulations 1993, any voltage exceeding 1000 V ac or 1500 V dc; The highest voltage level in a transformer; In terms of general usage in Transpower, the voltage on the primary winding of a transformer; Cables rated 3.3 kV ac and up to and including 33 kV ac.

holiday

A localised defect, where the coating has insufficient thickness or a discontinuity including missed area left uncoated with paint.

horizontal tension

Means the horizontal conductor tension in a span or series of spans within a tension section.

hot spot

An area of localised heating in electrical equipment.

hot stick (lines)

A rigid insulated pole usually made of fibreglass reinforced plastic (FRP) used to physically bridge the distance between energised components and earth, or to bridge between adjacent phases and to enable loads to be taken or tools to be applied.

hot stick live line work

The method of performing work on live transmission circuits using tools and equipment mounted on insulating poles. Live line workers remain at earth potential and are insulated from the conductor.

hot work

Any activity liable to produce a spark, hot metal or a naked flame. Activities designated as hot work include grinding, gas cutting, welding, drilling and any other activity which could provide an ignition source. [SM-EI].

HSE PECPR

Health & Safety in Employment (Pressure Equipment, Cranes and Passenger Ropeways) DRAFT Regulations.

humidity

The maximum amount of moisture (saturation or dew point) that can be absorbed into air varies greatly with temperature and absolute pressure. When air is at the saturation point, it is said to have humidity of 100%. The relative humidity of air at any time is the percentage of moisture contained in it as compared with the maximum amount it is capable of holding at the same temperature and pressure.

hunting

Unstable state in which a machine output, system frequency, etc. runs alternatively too fast and too slow. In synchronous machines hunting can arise from phenomena closely related to system stability or to the instability of an active feedback control system, for example a speed governor, or voltage regulator.

HV

Depending on context, can be one or more of: The set of voltage levels in excess of low voltage (LV); In terms of the Electricity Regulations 1993, any voltage exceeding 1000 V ac or 1500 V dc; The highest voltage level in a transformer; In terms of general usage in Transpower, the voltage on the primary winding of a transformer; Cables rated 3.3 kV ac and up to and including 33 kV ac.

HV cables

Cables rated 3.3 kV ac and up to and including 33 kV ac.

HV metal-clad switchgear

High voltage switchgear of a type that has its associated buswork totally enclosed in metal chambers or trunking.

HVAC

High voltage alternating current.

HVDC restart

An automatic control system which attempts to restart HVDC valve groups (Pole 1) or the thyristor (Pole 2) after a protection operation.

HW

Also referred to as "headpond", is that part of the reservoir created by the dam which is adjacent to the dam structure, and from which the water is drawn down the penstocks.

HWL

The level of water in the headwater.

hydrogen gas detection system

Term used to define a hydrogen gas detection system indicator panel which includes the components and devices connected to the indicator panel being gas monitors, gas alarm sounders and alarm lights and alarm signalling equipment for both remote and local alarms Devices such as automatic gas isolation valves which are activated by the system are to be recognised as part of the system.

hydrophobicity class

A term used for the assessment of the water repellency of a non-ceramic insulator.