Glossary terms beginning with B

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

Voltage that appears on an apparently isolated circuit as a result of either other parallel connections from the “energised” side or an independent source of generation on the “isolated” side.

Backup protection

Protection equipment which operates when a system fault is not cleared in the specified time because of failure of the main protection, or failure of a circuit-breaker other than the associated circuit-breaker.

Bar

A metric unit of pressure (approximately one standard atmosphere). It is commonly used for measuring SF6 gas and compressed air pressure. Vacuum is measured in negative millibars (that is, gauge pressure). The bar is equal to 100,000 N m-1. 1 bar = 1000 mbar.

Bare hand live line work

The method whereby a worker is placed at the same potential as, and works directly on energised conductor or equipment. The transfer of the worker to conductor potential may be accomplished through the use of insulated ladders, live line rope, insulated EPV personnel buckets or helicopters.

Barrier

An electrically isolated buffer zone established through the use of equipment designed to pass wanted signals but reject hazardous voltages.

Barring gear

A manual or motor-operated device for rotating the rotor of a machine at slow speed.

Base load (power system)

That component of the power system load which is continuously present over a stated period.

Base load station

A generating station serving mainly to meet the base load of the system.

Basic impulse insulation level (BIL)

A specific insulation level expressed in terms of the crest value of a standard lightning impulse.

Basic insulation level (BIL)

To meet a given BIL rating a bushing must be able to withstand a simulated lightning wave that has a wave shape of 1.2 by 50 microseconds and in both positive and negative polarities. The wave reaches its peak in 1.2 microseconds and decays to ½ of the peak value in 50 microseconds. BIL ratings are expressed in kV.

Basic Lightning Impulse

A specific insulation level expressed in terms of the crest value of a standard lightning impulse. Note 1: The manufacturer of equipment will generally subject the equipment to a voltage impulse test using a standard 1.2/50 us lightning impulse with a crest value equal to the BIL or LIWL. Note 2: The older term ‘BIL’ is being gradually replaced by the term ‘LIWL’.  Standard values for LIWL are set by IEC 71-1 Insulation Co-ordination – Definitions, Principles, and Rules. Insulation co-ordination design attempts to limit lightning surges to below the LIWL of equipment.

Battery

A unit consisting of one or more cells connected in series, parallel or a series parallel arrangement to provide the required voltage and current requirements of the connected load.

Battery bank

A unit consisting of one or more cells connected in series to provide the required voltage and current requirements of the connected load.

Battery charger

A unit which converts a.c. mains to d.c. for charging a battery and supplying the load.

Baud

A measure of data rate, expressed as the reciprocal of the shortest time element in a binary data stream.

Bay (of a station)

That part of a substation or power station within which the switchgear relating to a given circuit is contained. According to the type of circuit, a substation or power station may include: feeder bays, transformer bays, bus coupler bays etc.

BIL

A specific insulation level expressed in terms of the crest value of a standard lightning impulse. Note 1: The manufacturer of equipment will generally subject the equipment to a voltage impulse test using a standard 1.2/50 us lightning impulse with a crest value equal to the BIL or LIWL. Note 2: The older term ‘BIL’ is being gradually replaced by the term ‘LIWL’.  Standard values for LIWL are set by IEC 71-1 Insulation Co-ordination – Definitions, Principles, and Rules. Insulation co-ordination design attempts to limit lightning surges to below the LIWL of equipment.

Bipole power control (HVDC)

Bipole power control (HVDC).

Black start

The ability to start generating sets at a point of connection and raise them to speed, ready to liven the grid at that point of connection without any power being obtained from the grid.

Black start capability

The ability of a power station to commence generation and liven the bus after being completely shut down, with no electrical input from the power system.

Blind spot

The conductors between a circuit-breaker and the associated CT which may not be effectively protected unless dedicated blind spot protection is installed.

Block

A group of cells within one common container. Common block voltages are 2, 4, 6, 12 V.

Blocked

The non-conducting condition of the main and/or bypass valves of the HVDC system.

Blocking protection scheme

A distance protection scheme where the relays are set for rapid tripping for all faults up to and beyond the remote busbar. Tripping of one relay for faults at or beyond the remote busbar is blocked by a signal transmitted from the relay at the remote end. The relays do not exchange signals for faults on the protected transmission circuit.

Boilerplate

A generic statement appearing, with minimal variations, on all standards for legal clarification, copyright protection and user assistance.

Bonding (lines)

The electrical connecting together of adjacent conductive objects in close proximity to a work site to ensure that they are all at the same electrical potential, thereby eliminating electrical shock hazards.

Bonding-on (lines)

Live line bare hand procedure whereby the conductive-suited bare hand line worker bonds on to the live conductor using a bonding lead attached to the conductive suit which electrically bonds the live line worker to the live conductor.

Breaker-and-a-half station

A double-bus substation where, for two circuits, three circuit-breakers are connected in series between the two buses, the circuits being connected one each side of the central circuit-breaker.

Bridging / shunting (lines)

The term used to describe the electrical bridging by connecting a conductive shorting strap across, or in parallel with, two conductive components before they are separated, thereby preventing a difference of potential occurring across the gap, and eliminating a possible shock hazard.

Bulk-oil circuit-breaker

A circuit-breaker with contacts submerged in a reservoir of insulating oil, the tank of which is earthed.

Bunded area

The bunded impermeable area around oil-filled equipment to catch oil spills.

Bus

The common primary conductor of power from a power source to two or more separate circuits.

Bus changeover

Energising one busbar at a multiple busbar station, and subsequently de-energising another by the operation of bus selectors.

Bus coupler circuit-breaker

A circuit-breaker which is located between two busbars that can both be accessed by the same external circuit. The bus coupler circuit-breaker permits the busbars to be connected together or separated under load or fault conditions.

Bus section

Part of a bus that can be isolated from another part of the same bus.

Bus section circuit-breaker

A circuit-breaker in series with two bus sections that cannot be accessed by the same external circuit. The bus section circuit-breaker permits the bus sections to be connected together or separated under load or fault conditions.

Bus section disconnector

A disconnector in series between two bus sections.

Bus selector

The functional term for a disconnector that enables a circuit, transformer, etc. to be connected to a selected bus at a multiple bus station.

Bus zone

A zone of protection created when a busbar is divided for fault clearance purposes. A bus zone is bounded by circuit-breakers.

Bus zone protection

A scheme of one or more sets of differential relays connected to the CTs at the boundary of a bus (either one three-phase or three single phase relays per zone). The protection detects faults within the zone and trips all the circuit-breakers connected with that bus zone.

Busbar (bus)

A low impedance conductor to which several circuits/conductors can be separately connected.

Busbar (gas insulated switchgear)

Aluminium and/or copper hollow and solid bar supported by epoxy insulating barriers which sectionalise the GIS compartments.

Bushing

A device that enables one or several conductors to pass through a partition such as a wall or a tank, and insulates the conductors from it.  The means of attachment to the partition (flange or fixing device) forms part of the bushing.

Bushing current transformer

A current transformer in which the primary winding is either a cable or an insulated component of other apparatus.

Business plan

Has: a vision (what the future should look like), a mission (why it's important), objectives (the stated goals to achieve the vision), strategies for achieving each goal, and the actual plan of action for each strategy including financial aspect. In order to formulate each strategy the following is considered: where are we now in the context of the stated goal/objective, where do we want to be, how to get there - this forms a basis for the plan of action, key performance indicators (KPIs) and distribution of funds across the organisation.

Buswork

Outdoor busbars and connected hardware such as droppers, jumpers, tails, connection assemblies, and post and suspension insulators.

Bypass contactor

A protective device connected in parallel with the protective gap which closes when the current passing through the protective gap reaches a predetermined valve.

BZ

A zone of protection created when a busbar is divided for fault clearance purposes. A bus zone is bounded by circuit-breakers.