Glossary terms beginning with P

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

The standard abbreviation for pole, used in relation to the HVDC system - P1 and P2.

PABX

Private automatic branch exchange.

panel

An assembly consisting of a cabinet, equipment, and wiring, usually located in a control, relay or communications room.

parallel plate (coalescer/mesh) oil interceptor

An oil/water gravity separator fitted with parallel plates that enhances oil/water separation and has an oil-in-water effluent between 10 and 50 ppm.

parallel plate (coalescer/mesh) oil separator

An oil water separator fitted with parallel plates to enhance separation.

paralleling

Connecting a power system component (generator, transformer, transmission circuit, etc.) in electrical parallel with another (usually similar) path in the power system, connecting a generator to the power system, usually in parallel with other adjacent generators.

party code

A four-letter code used to identify energy market participants.

Pascal (Pa)

The standard unit of pressure under the SI system equivalent to one Newton per square metre eg 1 Pa = 1000 kPa, 1 kPa = 0.1 mbar = 6.895 p.s.i. PAS number: See prearranged switching number.

patch painting

The method of painting sections or specific members of towers to provide a barrier to allow the complete tower to age to a point of justifying painting.

PCM

A general term describing a digital method to encode information onto a carrier.

peak demand

The peak consumption of energy (averaged over a half-hour period and expressed in watts) recorded during a given time, for example, day, week, year.

peak load

The maximum peak load in amps that can be expected to be carried within a twelve month period on the circuit or by the equipment/component.

peak load station

A generating station designed to operate for a short period each day usually during the time of maximum demand. (See also base-load station - which more economically operates continuously throughout the day).

PECPR

The health and Safety in Employment (Pressure Equipment, Cranes, Passenger Ropeways) Regulations, 1999.

PEG

This is a group of equipment type COB's, Branch COB's and Outage COB's.  A PEG has a relationship to a single Branch COB.  A PEG will be used when any change in assets is planned to be carried out (usually by a project).  It is used to drive notifications and facilitate assessments between the Grid Owner and System Operator.

performance report

A report forwarded on a regular basis to monitor the normal operation of equipment and observe trends.

performance tests

The tests required to determine the characteristics of a machine and to show that the machine complies with its specification.

period

The interval of a half-hour in which resources are allocated for the purposes of dispatch. [GOSP glossary].

peripheral lines

Lines which constitute the principle source of supply to a particular load.

permanent earths

Fault-rated connections permanently bolted between equipment earth terminals and the station earthgrid as a safety measure.

permanent fault

A fault which can only be removed by remedial action taken at the point of the fault.

permanent meter

A meter installed at a station providing the normal revenue metering capability.

permission to proceed

The approval given by the Security Coordinator to the Network Operator to proceed with the operation of grid equipment, where equipment will be subject to a planned Transfer of Control.

permit

Access Permit or Test Permit as defined in SM-EI.

personal earth

A single phase portable earth, used by line workers working with conductors on a structure that has not had 3-phase portable earths applied between the conductors and earth. Personal earths minimises potential shock hazards where line workers are in contact with conductors and structure earths.

personal use

Refers to use for any purpose not related to business operations and activities of Transpower.

personnel

Refers to staff, consultants and contractors using Transpower's IT information systems. Where policy applies to staff, consultants and contractors the term personnel will be used. Where the policy is specific for staff or contractors these terms will be used respectively.

pH value

A logarithmic index for the concentration of hydrogen ions in an electrolyte.

phase sequence test

A test taken to determine whether the phase sequence of a polyphase machine or circuit is correct.

phase swinging

A form of hunting in which the fluctuations are periodic variations in the speed of a synchronous machine above and below the normal speed, resulting in periodic phase variations relative to the rest of the power system.

phase winding (transformers)

An assembly of turns forming one phase of a polyphase winding.

phase-to-phase fault

A defect in a multi-phase circuit that results in a current flow between any two phases at the point of the defect.

pilot

the pilot refers to the pilot in command of any aircraft. S/he is responsible for the operation, conduct and safety of the aircraft and air crew.

pilot cell

An electrode cell (usually cell 20) which has been selected for periodic inspection as an indicator of the condition of all cells.

pilot exciter

An exciter which supplies all or part of the power required for the excitation of a main exciter.

pilot inspection (circuit-breaker)

A sample internal inspection of interrupter unit of one pole of a "family" of circuit-breakers of the same type, age, and duty, to be carried out at specified intervals. These inspections will be used to assess the need for a major service of other interrupter units of the same type in service.

pilot wire protection

A differential protection scheme for a transmission circuit, where a relay at each end of the transmission circuit compares the current in the local end with a current representing the current at the remote end, sent via a metallic circuit (the pilot wires). A difference between these two currents indicates a fault on the protected transmission circuit, and causes tripping of the circuit via the relays.

plain break contact system

Where the circuit breakers are not fitted with internal arc control devices sometimes referred to as explosion pots or tubulators.

plan width

Refers to the overall distance between the outer conductors of a circuit when measured in a horizontal plane.

Planned Equipment Group

This is a group of equipment type COB's, Branch COB's and Outage COB's.  A PEG has a relationship to a single Branch COB.  A PEG will be used when any change in assets is planned to be carried out (usually by a project).  It is used to drive notifications and facilitate assessments between the Grid Owner and System Operator.

planned interruption

An interruption caused by a planned outage.

planned operating

Operating which has been subjected to the normal planning/approval (PROMS) process.

planned outage

A deliberate outage, with at least 24 hours notice, scheduled for maintenance purposes.

planned outage programme

An asset owner's overall programme of planned outages for the year.

planned work period

The time requested by the contractor to carry out the work.

plant

A term used in TP.MS 20.01 to include oil reconditioning and reclamation plants.

plant history

An on-going dated record of significant events, including hours in service, repairs effected, operational or performance changes occurring during the service life of equipment, as well as costs.

plant request

Consolidation of individual operational requests that share the same window.

platform

A general term used for scissor lift, aerial platform, or an extensible or articulating boom aerial device (either self-propelled or vehicle-mounted) used for the purpose of positioning personnel, their tools, and necessary materials to elevated work locations. Not included in this definition are ladder stands, scaffolds, or industrial trucks.

PLC

A computer-based controller, the logic of which can be programmed to enable it to perform varying functions.

point of connection

The physical point within the New Zealand power system where ownership of the transmission assets changes from a grid owner to a connecting party. [GOSP glossary].

point of isolation

Electrical: A disconnector, fuse-link, withdrawable circuit-breaker etc. that, when open or removed, provides a specific minimum separation distance between live equipment and that which is isolated.  Mechanical: A gate, damper, valve etc. that, when closed, provides a physical barrier between a source of harm and equipment which is isolated.

point of supply (POS)

Point of supply (POS)

polarisation

A shift in the potential of an electrode from the equilibrium value as a result of current flow through its surface.

polarity test

A test to demonstrate that the relative polarities of conductors are correct.

pole (of circuit-breaker)

The portion of a circuit-breaker associated exclusively with one electrically separated conducting path of its main circuit and excluding those portions which provide a means for mounting and operating all poles together.

pole discrepancy device

A device activated when a circuit-breaker fails to operate on all three poles. It applies a trip pulse to the circuit-breaker, operates an alarm, and brings up a relay flag.

pole slip

When an a.c. generator/motor operates asynchronously because its field excitation is too low or too negative to maintain synchronism.

pole-mounted substation

An outdoor distribution substation mounted on one or more poles.

Poles or Towers

Poles and Towers are support structures that have crossarms to hold the conductors clear of the ground. Towers are sometimes referred to as pylons.

policy

A principle or statement of Transpower's direction on a particular issue, as determined by management.

policy document

A controlled document explaining Transpower's direction on a particular issue, as determined by management.

pollution performance

The ability of an insulator to operate with a specified level of pollutants on its outer surface without suffering flashover.

portable earth

A portable device: for the temporary earthing of equipment; comprising flexible conductors and clamps of appropriate rating and design for the  conditions of use (the device is applied by a fixed or detachable insulating stick); of a type proven by appropriate type test and either provided or endorsed for use by the industry or any industry sector.  Note: For three-phase ac, a "set of earths" consists of portable earths which, when applied, effectively connect the three phases together as well as to earth/neutral. It does not include earthing trucks or other earthing devices for special situations. [SR-EI April 1995].

potential (native potential)

The potential which the tower leg exhibits while unaffected by any external influence. This could also be termed the unpolarised or rest potential.

potential (on potential)

The potential which the tower leg exhibits while influenced by an energised cathodic protection system. As well as the polarised potential this measurement will contain a contribution commonly termed the 'IR drop', which arises because of the current flow through a resistive medium, the soil.

potentially hazardous (transmission towers)

A tower is considered to be potentially hazardous when, regardless of the climbing difficulty, it would be possible to reach within flashover distance of the conductors by leaning out from the tower body. (An angle suspension tower of any voltage would be typical of this category.).

pothead,

The connection between a HV cable and air-insulated conductors.

power cable

A term used in this standard to include HV and EHV, AC and DC, paper and polymeric insulated power cables.

power factor

The ratio between active power (expressed in watts, W) and true power (expressed in volt-amperes, VA). Can vary between 1 and 0.

power line carrier (PLC)

A method for point-to-point transmission of information utilising transmission circuits as the primary transmission medium. Usually installed for power-line protection signalling, voice communication, data transfer, etc. See also protection signalling, line trap.

power quality

The electrical conditions to be found on the grid at any physical point. [GOSP glossary]

power spark gaps

A device comprising a spark gap assembly where the electrodes are completely enclosed in a housing (e.g. porcelain).

power station

A facility which exists primarily for the generation of electricity.

power supply (control, protection and comms)

A complete power system for control, protection, communication, consisting of a modular power cabinet or d.c. power cabinet, rectifiers, and battery and battery fuses.

power swing block

A device in a distance relay which prevents the relay tripping incorrectly due to power swings during system disturbances.

power system

See NZ power system.

power system stability

The capability of a power system to regain a steady state, characterised by the synchronous operation of the generators after a disturbance due, for example, to variation of power or impedance. [GOSP glossary - IEC 50 (603-03-01)].

power transformer

power transformer

PRBS

Psuedo Random Binary Sequence

pre-livening inspection

The final inspection which determines that livening of equipment can safely proceed.

pre-stressed concrete

Means concrete containing reinforcing steel, some or all of which has been tensioned prior to the application of external loads. Refer to HSE PECPR regulations Schedule 1.

precommissioning inspection (lines)

An inspection carried out during the precommissioning stage of commissioning to identify any work necessary to ensure that the line meets all Transpower Operations and Maintenance take-over standards.

preparing for service

A term used in this standard to include the necessary tests, inspections and functional checks prior to commissioning instrument transformers.

pressure equipment

Any pressurised equipment (including piping) containing a gas and/or liquid at a pressure in excess of 50kPag. It includeds all attachments, fittings, foundations, mountings and supports.

pressure relief current limit

The maximum power frequency current (rms) that an arrester can withstand, following an internal failure, without explosion of the housing.

pressure relief device

A device fitted to an electrical oil system (for example, tap-changers, power transformers, reactors) to detect an explosive fault and trip the system. When the pressure returns to normal, the device reseals. [Related term: burst disk].

pressure vessel

Refer to HSE PECPR regulations Schedule 1.

pressure vessels/air receivers

Tanks used for the storage of compressed air. They also serve to damp discharge line pulsations and remove condensate.

prevailing torque nut

A nut that incorporates a nylon insert to lock it on to the bolt thread (commonly known by the brand name "Nyloc").

primary d.c. panel

A cabinet in which the separate batteries and battery chargers of a station dual system are parallelled through steering diodes to a common bus.

primary equipment

Power system equipment operating at a high voltage (cf. secondary equipment, ancillary equipment).

primary surface preparation

Preparation of non-rusted tower steel for primary painting by high-pressure water cleaning.

primary winding

The transformer winding that receives ac power from a source.

prime mover

A general term applied to any primary source of motive power, that is, engine, turbine, motor, etc.

principal tapping (transformers)

The voltage tapping to which the power transformer’s rated quantities are related.

priority factor (Pf)

The factor dervied from the Graph in TP.GL 01.04 Appendix D which indicates the priority assigned to painting particular towers.

procedure

Specified way to perform an activity.

procedure sheet

A document that sets out in detail each step to be followed when carrying out a specific activity.

process

Set of inter-related resources and activities which transform inputs into outputs.

producer

Any party that owns or operates one or more generating sets (units). Such sets may be embedded in a network or directly inject into the grid at a point of connection. [GOSP glossary].

programmable logic controller

A computer-based controller, the logic of which can be programmed to enable it to perform varying functions.

project controller

A Transpower Field Services employee responsible for: the overall management of a project involving the commissioning of equipment, and; afacilitating approval of the commissioning plan.

project engineer

A project controller appointed person responsible for the overall coordination of all project activities involving the commissioning of equipment.

PROMAINT

Westronic/GE Harris RTU resident software user interface which allows maintenance staff to interrogate the peripheral, via a RS232 port on each D20 P peripheral board to run diagnostic checks and to force certain types of data for testing purposes. The software is more limited than the WESMAINT.

PROMS

Transpower’s Plant Request and Outage Management System. This is a computer-based information system for nationally managing outage windows and plant requests.

protection (PROT)

The equipment provided for detecting abnormal conditions in a power system and then initiating fault clearance or actuating signals or indications.

protection current

The current made to flow into a structure from the soil in order to effect cathodic protection of the structure.

protection group

A protection group is a number of protection relays normally taken out of service as an entity when performing routine maintenance on the protection. In many cases the group will comprise the complete protection for a primary plant item but on lines equipped with 2 protections, No. 1 protection and No. 2 protection are separate groups.  On bus zone protection each zone is a group.

protection installation

The protection relays and all other devices required to protect a particular item of primary plant.  This includes the relays, CTs, VTs, CB(s), communications links, auxiliary supplies and all the cabling between these items.

protection operated alarms

These are alrms initiated during operation of the protection.

Protection Operated Main Mode

Protection Operated Back Up Mode.

protection potential

The more negative level to which the potential of a structure with respect to a reference electrode has to be depressed in order to effect cathodic protection.

protection signalling

Signals transmitted between the protection relays at each end of a transmission circuit.

protection signalling equipment

Communications equipment used to transmit protection signals between protection relays at each end of a transmission circuit. Does not include the communications bearer (i.e. PLC, radio, OPGW).

protection supervision alarms

There are alarms initiated should the protection become defective.  Examples are:Relay internal power supply fail : initiates "Protection Defective" alarm, VT Supervision operated (VT supply faulty) : initiates "Protection Defective" alarm, Trip Circuit Supervision relay operated : initiates "Trip Circuit Defective" alarm, VCB Operated : initiates "Protection Defective" alarm.

protective gap

A protective device connected in parallel with a resistor bank which permits fault current to start discharging when a predetermined voltage is reached.

protective level

For arresters with spark gaps it is the higher of the impulse sparkover voltage and the residual voltage. For gapless arresters it is the residual voltage.

protective ratio

The insulation level divided by the protective level. Note: This differs from the definition given in IEC 99.

proven de-energised

Use of an approved voltage detector to confirm that a conductor or equipment termination is de-energised.

provider (of grid security services)

Any party, that is not a producer, that contracts with the grid operator to provide reserves or reactive power to support the operation of the grid. [GOSP glossary].

PSB

A device in a distance relay which prevents the relay tripping incorrectly due to power swings during system disturbances.

PSE

Communications equipment used to transmit protection signals between protection relays at each end of a transmission circuit. Does not include the communications bearer (i.e. PLC, radio, OPGW).

PSTN

That part of the public telecommunications network that enable any customer to call and communicate with any other customer, either automatically or with operator assistance.

PTP

The approval given by the Security Coordinator to the Network Operator to proceed with the operation of grid equipment, where equipment will be subject to a planned Transfer of Control.

public area

The part of a station or communications site that is open for public access.

public switched telephone network

That part of the public telecommunications network that enable any customer to call and communicate with any other customer, either automatically or with operator assistance.

pulse code modulation

A general term describing a digital method to encode information onto a carrier.

purging

The controlled removal of a fluid or gas by replacing it with another.

PV array

The controlled removal of a fluid or gas by replacing it with another.