What is an RX diagram?
The operating characteristics of an impedance relay can be more easily represented by a diagram called R-X diagram. The diagram is shown in a plane having X-axis as R (resistance) while the Y-axis as X (reactance). This plane is called R-X plane.
What are the characteristics of impedance relay reactance relay in RX diagram?
The operating characteristics of such relay is a straight line parallel to the x-axis i.e R-axis on R-X diagram. All the impedance vectors have their tips lying on the straight line representing constant reactance. The resistance component of the impedance has no effect on the operation of the relay.
What does a impedance relay do?
An impedance relay is a voltage restrained overcurrent relay. The relay measures impedance up to the point of fault and gives tripping command if this impedance is less than the relay setting Z.
How RX plane of impedance are different from that of mho relays?
Any point on the R-X plane corresponds to an infinite number of possible fault conditions even for the same power system. Impedance relays use not only the faulted phase voltages and currents, but also the prefault and unfaulted phase voltages and currents to determine operation.
Which relay is also called angle impedance relay?
Mho Relay: It is also known as angle impedance relay.
What is the function of Buchholz relay?
The Buchholz relay purpose is to give the protection to a transformer from the different faults happening in the transformer like the Short circuit, inter-turn, core, incipient, etc. This relay will sense these faults and shuts the alarm circuit.
Why impedance relay is non directional?
It is also seen that the impedance relay, basically a non-directional relay, as it operates on the magnitude of the operating quantity and not on its direction of flow, The figure indicates that the operating time of this relay is constant irrespective of the distance within the protective zone.
What is an impedance relay explain its operating principle describe how it is realized using electromagnetic principle?
Principle of Operation of Impedance Relay But when the fault occurs on the line the magnitude of the current rises and the voltage becomes less. The line current is inversely proportional to the impedance of the transmission line. Thus, the impedance decreases because of which the impedance relay starts operating.
What exactly is mho relay with a diagram explain the design and and operation of mho relay in detail?
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.
Why it is called Mho relay?
It is inherently a directional relay as it detects the fault only in the forward direction. The relay is called Mho relay because its characteristic is a straight line, when plotted on an admittance diagram (G-B axes i.e., conductance – susceptance axes) as in the figure.
Is distance relay and impedance relay same?
As the ratio of voltage to current is nothing but impedance so a distance relay is also known as impedance relay. The operation of such relay depends upon the predetermined value of voltage to current ratio. This ratio is nothing but impedance.
What is working principle of Buchholz relay draw its diagram?
How does a Buchholz Relay work? Whenever a minor fault occurs inside the transformer, heat is produced by the fault currents. The produced heat causes decomposition of transformer oil and gas bubbles are produced. These gas bubbles flow in upward direction and get collected in the buchholz relay.
What are the characteristics of directional impedance relay?
The characteristics of directional impedance relay for one value of V can be represented on the R-X diagram as shown in Fig. 3.48. The fact that for some values of θ, impedance Z will be negative which should be ignored. Negative Z has no significance and cannot be shown on R-X diagram.
Are you familiar with R-X diagrams and impedance relay characteristics?
Knowledge of true protective relay characteristics has not been communicated fully and properly from protective relay designers and protection engineers, to field test technicians. As a result, many misunderstandings about R-X diagrams and impedance relay characteristics are widely held.
Why do relay manufacturers draw quadrilateral R-X diagrams?
Relay manufacturers have always drawn quadrilateral characteristics on R-X diagrams with some degree of generality and vagueness. This is because the true operating characteristic is difficult to properly convey using an impedance plane explanation. These diagrams are meant to be conceptual but often we try to take them literally.
Why resistance of impedance relay is negative?
Here it should be noted that Resistance is not negative rather it implies that current is lagging by 180 degree. As the operating characteristics of Impedance Relay is a circle in nature, this Relay is non direction i.e. it doesn’t matter whether the current is leading or lagging it will operate if impedance seen by the Relay is within the circle.