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A fault indicator is a mechanism that conveys an indication of a fault, or absence of it, in a system. For example, the purpose of the engine-check light commonly found on the dashboard of motor vehicles is to indicate whether or not there is a fault with the engine.
In electric power distribution networks, a fault indicator is a device which provides visual or remote indication of a fault on the electric power system. Also called a faulted circuit indicator (FCI), [1] the device is used in electric power distribution networks as a means of automatically detecting and identifying faults to reduce outage time.
Overhead indicators are used to visualize the occurrence of an electrical fault on an overhead electrical system. Underground indicators locate faults on an underground system. Often these devices are located in an underground vault. Some fault indicators communicate back to a central location using radio or cellular signals.
Typically fault indicators sense magnetic field caused by current flows through a conductor or cable. Some of them also use measurement of electric field caused by voltage in conductor.
During an electrical fault on a grounded system, additional current flows through a conductor, inducing a magnetic field, which is detected up by the fault indicator causing a state change on the mechanical target flag, LED, or remote indication device. Ground fault indicators for isolated ground systems sense the vector sum of the current and look for an imbalance indicating a fault on one or more of the three phases.
Systems with earthing through high resistance have low phase-to-ground fault currents so require high sensitivity of FI[ clarification needed ]. When there are high load currents and low earth fault levels the line mounted fault indicators should look at the differential increase of the current instead of the absolute value.
In insulated neutral systems and systems with earthing through a Petersen coil, ground faults cannot be located with classical FI's at all. Capacitive current appears in overall faulted system so directional fault location devices are required.
Upon energization of the lines there could be high inrush current which may lead the fault indicators to false operation. Some fault indicators can block inrush current.
Advanced fault indicators should monitor the live line to distinguish fault currents from usual current surges. They operate only after making sure of the feeding circuit breaker/fuse has cut the power flow and the line is de-energized. To monitor the live line, some fault indicators look only at the magnetic field caused by the load current. to be independent from the load current, some FI’s look at the E field[ clarification needed ] to check the voltage directly. This feature is used to reset the indicator after the line is re-energized too. Such indicators can also distinguish permanent faults from transient faults.
Some modern network protection systems have time to clear a fault as small as possible down to 60 ms so fault indicators must not only be highly sensitive and directional but additionally very fast. [2] Modern fault indicators can detect faults with the duration of one cycle 18–20 ms. In the networks with low earth fault levels the indicators are required to be set to low values. In such cases the user should consider the downstream capacitive discharge current to avoid false operation of the non-directional indicators.
Some overhead line fault indicators called as pole mounted fault indicators can detect the live line and the fault current from 3 to 5 metres (9.8 to 16.4 ft) below the conductors.
High-voltage fuses commonly drop down after operating, making it obvious where the fault is. However fuses are rarely equipped with remote communication.
The first fault indicators were brought onto the market by Horstmann from Germany in 1946. The E. O. Schweitzer Manufacturing Company (now a division of Schweitzer Engineering Laboratories) introduced a product to the United States in 1948. The first fault indicators were manual reset devices. Later fault indicators automatically reset on system restoration or after a set period of time. More recent fault indicators communicate their status (tripped or reset) via cell signal or radio to a central station, handheld device, or pole-mounted receiver.
Recent developments include a remotely programmable overhead line indicator, fault indication for paper-insulated lead cable, and an overhead fault indicator for mesh networks.
A circuit breaker is an electrical safety device designed to protect an electrical circuit from damage caused by current in excess of that which the equipment can safely carry (overcurrent). Its basic function is to interrupt current flow to protect equipment and to prevent fire. Unlike a fuse, which operates once and then must be replaced, a circuit breaker can be reset to resume normal operation.
A residual-current device (RCD), residual-current circuit breaker (RCCB) or ground fault circuit interrupter (GFCI) is an electrical safety device, more specifically a form of Earth-leakage circuit breaker, that interrupts an electrical circuit when the current passing through line and neutral conductors of a circuit is not equal, therefore indicating current leaking to ground, or to an unintended path that bypasses the protective device. The device's purpose is to reduce the severity of injury caused by an electric shock. This type of circuit interrupter cannot protect a person who touches both circuit conductors at the same time, since it then cannot distinguish normal current from that passing through a person.
An earth-leakage circuit breaker (ELCB) is a safety device used in electrical installations to prevent shock. It consists of either a current sensing mechanism, or a voltage sensing mechanism. Such a protection mechanism may be found in the form of distribution board modules, standalone devices, and special sockets.
A current transformer (CT) is a type of transformer that reduces or multiplies alternating current (AC), producing a current in its secondary which is proportional to the current in its primary.
A distribution transformer or service transformer provides a final voltage transformation in the electric power distribution system, stepping down the voltage used in the distribution lines to the level used by the customer. The invention of a practical, efficient transformer made AC power distribution feasible; a system using distribution transformers was demonstrated as early as 1882.
In electric power distribution, automatic circuit reclosers (ACRs) are a class of switchgear designed for use on overhead electricity distribution networks to detect and interrupt transient faults. Also known as reclosers or autoreclosers, ACRs are essentially rated circuit breakers with integrated current and voltage sensors and a protection relay, optimized for use as a protection asset. Commercial ACRs are governed by the IEC 62271-111/IEEE Std C37.60 and IEC 62271-200 standards. The three major classes of operating maximum voltage are 15.5 kV, 27 kV and 38 kV.
In an electric power system, a switchgear is composed of electrical disconnect switches, fuses or circuit breakers used to control, protect and isolate electrical equipment. Switchgear is used both to de-energize equipment to allow work to be done and to clear faults downstream. This type of equipment is directly linked to the reliability of the electricity supply.
Inrush current, input surge current, or switch-on surge is the maximal instantaneous input current drawn by an electrical device when first turned on. Alternating-current electric motors and transformers may draw several times their normal full-load current when first energized, for a few cycles of the input waveform. Power converters also often have inrush currents much higher than their steady-state currents, due to the charging current of the input capacitance. The selection of over-current-protection devices such as fuses and circuit breakers is made more complicated when high inrush currents must be tolerated. The over-current protection must react quickly to overload or short-circuit faults but must not interrupt the circuit when the inrush current flows.
An electronic component is any basic discrete electronic device or physical entity part of an electronic system used to affect electrons or their associated fields. Electronic components are mostly industrial products, available in a singular form and are not to be confused with electrical elements, which are conceptual abstractions representing idealized electronic components and elements. A datasheet for an electronic component is a technical document that provides detailed information about the component's specifications, characteristics, and performance. Discrete circuits are made of individual electronic components that only perform one function each as packaged, which are known as discrete components, although strictly the term discrete component refers to such a component with semiconductor material such as individual transistors.
An earthing system or grounding system (US) connects specific parts of an electric power system with the ground, typically the equipment's conductive surface, for safety and functional purposes. The choice of earthing system can affect the safety and electromagnetic compatibility of the installation. Regulations for earthing systems vary among countries, though most follow the recommendations of the International Electrotechnical Commission (IEC). Regulations may identify special cases for earthing in mines, in patient care areas, or in hazardous areas of industrial plants.
A test light, test lamp, voltage tester, or mains tester is a piece of electronic test equipment used to determine the presence of electricity in a piece of equipment under test. A test light is simpler and less costly than a measuring instrument such as a multimeter, and often suffices for checking for the presence of voltage on a conductor. Properly designed test lights include features to protect the user from accidental electric shock. Non-contact test lights can detect voltage on insulated conductors.
Galvanic isolation is a principle of isolating functional sections of electrical systems to prevent current flow; no direct conduction path is permitted.
In electric power systems and industrial automation, ANSI Device Numbers can be used to identify equipment and devices in a system such as relays, circuit breakers, or instruments. The device numbers are enumerated in ANSI/IEEE Standard C37.2 Standard for Electrical Power System Device Function Numbers, Acronyms, and Contact Designations.
In an electric power system, a fault or fault current is any abnormal electric current. For example, a short circuit is a fault in which a live wire touches a neutral or ground wire. An open-circuit fault occurs if a circuit is interrupted by a failure of a current-carrying wire or a blown fuse or circuit breaker. In three-phase systems, a fault may involve one or more phases and ground, or may occur only between phases. In a "ground fault" or "earth fault", current flows into the earth. The prospective short-circuit current of a predictable fault can be calculated for most situations. In power systems, protective devices can detect fault conditions and operate circuit breakers and other devices to limit the loss of service due to a failure.
Pre-charge of the powerline voltages in a high voltage DC application is a preliminary mode which limits the inrush current during the power up procedure.
Stray voltage is the occurrence of electrical potential between two objects that ideally should not have any voltage difference between them. Small voltages often exist between two grounded objects in separate locations by the normal current flow in the power system. Contact voltage is a better defined term when large voltage appear as a result of a fault. Contact voltage on the enclosure of electrical equipment can appear from a fault in the electrical power system, such as a failure of insulation.
High-voltage switchgear is any switchgear used to connect or disconnect a part of a high-voltage power system. This equipment is essential for the protection and safe operation, without interruption, of a high voltage power system, and is important because it is directly linked to the quality of the electricity supply.
An electric power system is a network of electrical components deployed to supply, transfer, and use electric power. An example of a power system is the electrical grid that provides power to homes and industries within an extended area. The electrical grid can be broadly divided into the generators that supply the power, the transmission system that carries the power from the generating centers to the load centers, and the distribution system that feeds the power to nearby homes and industries.
In utility and industrial electric power transmission and distribution systems, a numerical relay is a computer-based system with software-based protection algorithms for the detection of electrical faults. Such relays are also termed as microprocessor type protective relays. They are functional replacements for electro-mechanical protective relays and may include many protection functions in one unit, as well as providing metering, communication, and self-test functions.
This glossary of electrical and electronics engineering is a list of definitions of terms and concepts related specifically to electrical engineering and electronics engineering. For terms related to engineering in general, see Glossary of engineering.