2.Mho type distance relay. A typical wiring diagram for a low-voltage impedance relay is shown in Figure 6-38. The relay is used in ‘high impedance’ applications in conjunction with external stabilising resistors and non-linear resistors (Metrosils). This means that for Impedance Relay to Operate the Impedance seen by it must be less than a particular value which can be set to a desired value by the user.. Operating Characteristics on V-I Diagram: Initial bend in the characteristics is because of the presence of spring torque. Pilot Relays . Pilot relaying is a means of communicating information from the end of a protected line to the protective relays at both line terminals. Standardised external components can be provided in an … a restrained analog electronic bus differential relay (RADSS). M&I Materials Limited supply a wide variety of Metrosils designed for the The use of an impulse response may be used in combination with the fast Fourier transform (FFT) to rapidly measure the electrical impedance of various electrical devices. This is an electronic relay that makes use of a hybrid type of circuit that allows for CTs of different ratios and classes to be utilized in a differential scheme. For the characteristics it is obvious that 1/slope i.e. Metrosils for High Impedance Relays March 2016 Page 1 of 4 Introduction In some applications of high impedance relays, a non-linear Metrosil resistor is required to limit the current transformer (CT) secondary voltage to a safe level during maximum internal fault conditions. Impedance relays use not only the faulted phase voltages and currents, but also the prefault and unfaulted phase voltages and currents to determine operation. Lets us assume that High Impedance Differential protection is used to protect a Bus bar as shown in figure. The first section is set higher than the transformer magnetizing current. Through fault is a fault outside the zone of protection. These relays may work on either alternating or direct current, but for alternating current, a shading coil on the pole: 14 is used to maintain contact force throughout the alternating current cycle. In this method a directional relay is added in series with distance relay to get directionality to trip characteristics. "Armature"-type relays have a pivoted lever supported on a hinge or knife-edge pivot, which carries a moving contact. The relay can be applied to busbars, connections, transformers, reactors and motors. Stabilizing Resistor in High Impedance Differential Protection is used to prevent the operation of Relay in case of through fault. Impedance Relays. Some relays use a bias characteristic with three sections, as shown in Figure 7. 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