Electrical Terms

Electrical Substation Equipment

For transferring of electrical power from generating unit to distributing units various types of electrical equipment are required. The equipment like bus bars, isolator, power transformer etc., are assembled together in the electrical substation through which consumers get electrical supply. The main equipment required for the substation installations is explained below in details: Lightning Arrestor …

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Outdoor Substation

A substation which is used for all voltage levels between 55 KV to 765 KV is called outdoor substation. Such type of substation requires less time for construction but uses more space. The outdoor substations are mainly classified into two types, namely pole-mounted substation and foundation-mounted substations. Pole Mounted Substation Such substations are used for supporting …

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Indoor Substation

A substation in which the apparatus is equipped inside the substation building is called indoor substation. Such type of substation is mainly used for the voltage up to 11000 v, but when the surrounding air is contaminated by impurities such as metal corroding gases and fumes, conductive dust, etc., their voltage can be raised up …

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Critical Clearing Angle

The critical clearing angle is defined as the maximum change in the load angle curve before clearing the fault without loss of synchronism. In other words, when the fault occurs in the system the load angle curve begin to increase, and the system becomes unstable. The angle at which the fault becomes clear and the …

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Equal Area Criterion

The equal area criterion is a simple graphical method for concluding the transient stability of two-machine systems or a single machine against an infinite bus. This principle does not require the swing equation for the determination of stability conditions. The stability conditions are recognized by equating the areas of segments on the power angle diagram …

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Electronic Relay

Definition: The electronic relay is a type of an electronic switch that opens or close the circuit contacts by using electronic component without any mechanical operation. In this relay, the current carrier pilot relaying scheme is used for the protection of the transmission line. In such type of relay, the electronic valves are used as …

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Negative Sequence Relay

Definition: A relay which protects the electrical system from negative sequence component is called a negative sequence relay or unbalance phase relay. The negative sequence relay protects the generator and motor from the unbalanced load which mainly occurs because of the phase-to-phase faults. The negative sequence relay has a filter circuit which operates only for the …

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Differential Protection Relay

Definition: The relay whose operation depends on the phase difference of two or more electrical quantities is known as the differential protection relay. It works on the principle of comparison between the phase angle and the magnitude of the same electrical quantities. For example: Consider the comparison of the input and output current of the …

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Mho Relay

A mho Relay is a high-speed relay and is also known as the admittance relay. In this relay operating torque is obtained by the volt-amperes element and the controlling element is developed due to the voltage element. It means a mho relay is a voltage controlled directional relay. A mho relay using the induction cup structure …

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Reactance Relay

The reactance relay is a high-speed relay. This relay consists of two elements an overcurrent element and a current-voltage directional element. The current element developed positive torque and a current-voltage developed directional element which opposes the current element depending on the phase angle between current and voltage. Reactance relay is an overcurrent relay with directional …

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