Electrical Outage Terms

A glossary of electrical outage terms that may be used in the Alectra Utilities (formerly PowerStream) Outage Communication Service, Alectra Utilities media releases or electrical emergency situations.

ANIMAL CONTACT An outage term used to define the cause of an interruption. Typically due to birds, squirrels and raccoons that utilize the primary distribution system as travel paths or landing spots.
ARC The flow of an electric current across a gap between two conductors, terminals or contacts. An arc can result in sparks, a loud noise and a momentary or sustained outage as protective equipment operates.
AUTO-RECLOSURE A brief, split-second outage, where a protective device senses a fault and instructs the substation circuit breaker to trip, and then automatically re-closes the circuit breaker on the assumption the fault was transient.
CIRCUIT BREAKER Circuit breakers are typically located at substations and are the main devices to connect and disconnect power to the distribution network. Upon protective relaying sensing faults downstream, circuit breakers trip to prevent further damage to the network.
CABLE FAULT A large portion of the Alectra Utilities distribution network comprises of buried cable. When this term is used, it typically is describing a failure of the cable or a splice connecting cables. Upstream fusing will operate to isolate the faulted cable section from the rest of the distribution network. In many instances, Alectra Utilities crews can isolate the faulted section and restore power to all customers.
CIRCUIT The Alectra Utilities distribution network is comprised of circuits that are supplied by circuit breakers at substations. Most circuits have multiple connections to other circuits to provide redundancy in supply.
CONDUCTOR A conductor is the overhead wire utilized in the distribution network to deliver power. Conductors range in size to accommodate the planned and connected power delivery requirements on that portion of the circuit.
CROSSARM Located at the top of a utility pole, it is a fiberglass, wooden or metal bar that power line conductors are attached to via insulators. The crossarm keeps the lines separated by a sufficient distance to prevent arcing.
CUSTOMER A customer is a metered connection to the Alectra Utilities distribution network. The customer entity may range from a single residence to a large industrial complex to a multi-unit condominium building.
FUSED CUTOUT A term commonly used by system control operators to describe a distribution system fused switch.
DIP (RISER) POLE The transition point where an overhead wire migrates to an insulated cable for an underground installation.
DISTRIBUTION SYSTEM The electrical distribution system is the Alectra Utilities plant that is used to deliver power from our delivery points (typically the transmission system) to our customers.
ELBOW An insulated connector in the underground system, which connects cables to switches and transformers.
ELECTRICAL SAFETY AUTHORITY (ESA) The provincial body responsible for inspecting and approving all electrical installations. Alectra Utilities cannot connect any facility to our distribution network without ESA approval.
EMERGENCY CONTROL ACTIONS Actions taken by Alectra Utilities to assist in the mitigation of unplanned contingencies on the bulk supply of power in the province.
EQUIPMENT ISSUE An outage term used to define the cause of an interruption meaning that a piece of equipment or device on the distribution network may have prematurely failed or become inoperable, resulting in an interruption.
FAULT A fault is used to describe a failure of some component of the distribution network in its ability to deliver power. A fault generally is defined as a path from the distribution network to “ground”. The cause can range from equipment failure to foreign interference (e.g. tree contact, dig-in, etc.) Protective devices are utilized to sense faults and automatically isolate that section of network or component.
FEEDER A feeder is the term used to “name” the circuit supplied by a circuit breaker on the distribution network.
FUSE A protective device consisting of conducting material which melts and burns open when current values exceed the design capacity of the downstream circuit. This typically happens when faults occur.
GALLOPING Overhead conductors that sway extraordinarily under high wind conditions.
INDEPENDENT ELECTRICITY SYSTEM OPERATOR (IESO) The provincial entity that ensures adequate generation is always dispatched to meet the instantaneous need (demand) in the province. They operate the financial spot market (financial) and the physical market (generation/demand). They are an independent body created upon the de-regulation of the Ontario electricity industry in 1998.
INSULATOR A non-conducting device used to separate energized conductors from support structures.
ISOLATE/ISOLATION This term is used when components or portions of the distribution network are removed from service and “isolated” from the energized network.
LOAD SHEDDING Emergency actions to remove load in an attempt to stabilize the electricity infrastructure in the province.
LOSS OF SUPPLY An outage term used to define the cause of an interruption meaning loss of supply from the transmission system or facility.
METER A device used to measure the consumption of electricity by a customer. Enhanced features of smart meters also can report when the consumption occurred and other important operational information such as indicating real-time power interruptions.
MOMENTARY INTERRUPTION An electrical interruption lasting one minute or less.
OPERATE The act of opening or closing a device
OUTAGE MANAGEMENT SYSTEM (OMS) An advanced software application that allows Alectra Utilities to manage the response to outages much more efficiently. The application takes real-time statuses of circuit breakers, switches, and even smart meters to constantly provide a visualization of the status of the distribution network.
PLANNED MAINTENANCE An outage term used to define the cause of an interruption meaning planned work on some component of the distribution network. Usually this means the removal of service of the equipment with an associated interruption. This type of interruption is planned with advanced notification given to customers.
PRIMARY This term is used when describing the medium voltage level components of the distribution network – typically the wires and cables used to deliver bulk amounts of power through our network.
PROTECTIVE DEVICE/EQUIPMENT A device or equipment that responds to fault conditions that appear on the network. These devices will operate under fault conditions (fuse) or instruct a circuit breaker to trip. All components of the distribution network are associated with protective devices and equipment.
RELAY Protective device found in substations which can identify that a part of the distribution system is in trouble and initiates the automatic tripping of a circuit breaker.
S.C.A.D.A. Supervisory Control and Data Acquisition. Allows Alectra Utilities system control operators to monitor and remotely control the distribution system from a central control room.
SECONDARY Service taken at 600 volts or less. Most residential and business customers receive electricity through secondary distribution lines (from the distribution transformer)
SECTIONALIZE The process of opening switches or fuses to divide a circuit into sections to isolate a faulted component. Separating damaged equipment from the rest of the distribution system enables electricity to move through the undamaged part of the system without interruption.
SEVERE WEATHER Extraordinary weather patterns that contribute to power outages (such as high winds or freezing rain).
SUBSTATION The substation takes power from the transmission system and transforms it down to the distribution voltage level. Circuit breakers are the main interface between the substation and the distribution network.
SURGE A term usually used to describe a brief, but higher than normal voltage condition on a feeder circuit. This sometimes occurs during lightning strikes.
SUSTAINED (INTERRUPTION) An electrical interruption that lasts longer that one minute.
SWITCH A device for making, breaking or changing connections in an electrical circuit.
SWITCHYARD An outdoor enclosure containing devices for routing the flow of power. These are usually located at substations.
TRANSFORMER A device that transforms electric energy from one voltage to another. Distribution transformers can be pole-mounted, surface pad-mounted or installed underground. Large transformers are located at substations and transform power from transmission voltages to distribution voltages.
TRANSFORMER STATION A large substation connecting taking power from the transmission system, transforming it power distribution levels, and containing circuit breakers to interface to the distribution network.
TRANSMISSION SYSTEM The transmission system carries electric power at very high voltages, generally between 50,000 and 500,000 volts. It also carries electricity over long distances, usually from generating sources to a transformer station or substation for voltage reduction.
TREES INTO LINES Used when trees or tree branches come into contact with overhead conductors. Trees can also come into contact when they are being cut down improperly and fall into the conductor.
UNDER FREQUENCY LOAD SHEDDING Planned scheme to drop load automatically upon degradation of the system frequency. This occurs in stages and is usually the result of large scale problems with provincial bulk power system.
UNDER INVESTIGATION A power outage has been reported and entered into the Outage Management System to begin the restoration process.
VAULT Space underground for cable splices, transformers and other parts of the underground electric system.
VOLTAGE The term used to describe the electric potential of the distribution network. The measurement of voltage is the potential between two separate points (typically “ground” and our energized conductors).
VOLTAGE REDUCTION Voltage reductions are an important emergency control action that can help protect the reliability of the power system. The reduced voltage will remain within the industry standards specified for electrical equipment used by the vast majority of residential and commercial consumers