The phasor diagram for directional over-current relay is shown below. These relays consist of two beam-type over­ current unit, a directional unit, and an indi­ cating contactor switch. The consequent emphasis on circuit relia-bility means that more and more dependence must be placed on the system relaying. Static Instantaneous and Definite Time Overcurrent Relays: The block diagram of an instantaneous overcurrent relay is shown in Fig. When the power system is not radial (source on one side of the line), an overcurrent relay may not be able to provide adequate protection. … The overcurrent relay REJ 513 is a secondary relay which is connected to the current transformers of the object to be protected. is not open circuited. Directional Over current Relays; 1. Its operation is time independent. Seek to live, currently behind live LIVE. Directional overcurrent relay: Construction: It consists of two units: i) Non-directional Over-current unit ii) Directional power unit. Explain with a neat sketch the working of Voltage balance differential Relay 17. The SEL-751 Feeder Protection Relay is ideal for directional overcurrent, fault location, arc-flash detection, and high-impedance fault detection applications. Now our Directional Overcurrent (67) test plan looks like the following drawing where we start with the raw currents and voltages, calculate the non-faulted phase-to-phase voltage, and plot the operating current and polarizing signal, which in … The phasor diagram of a meter test on the Directional Overcurrent 67 relay connected to Circuit Breaker 4 would look like the following. The trip circuit of the relay includes the directional contacts in series with the contacts of one overcurrent unit, the operation indicator, and the contac­ tor switch. Here, Øv is the flux created by Voltage Coil which lags behind the Voltage by around 70 to 80 degree. The compensating winding ampere-turns on the lower magnet opposes the ampere-turns produced by the current coil. 4. The The directional element is added with the over-current relay in order to minimize the outage area [13, 14]. Optional Mirrored Bits® communications and power quality monitoring add flexibility to solutions. To protect ring or loop networks directional over current relays are commonly employed. Remaining Time -0:00 . 4.9. One is a directional element, which determines the direction of current flow with respect to a voltage reference. The same construction may be used for under-voltage, overvoltage or earth fault relays too. Normally, the conventional over current relay non-direction will act for fault current in any direction. of the directional relays should be connected as shown. The relay can be polarized from a po-tential source, from a local ground source, or from both simultaneously. The directional overcurrent relay suffers from the drawback that the feeder voltage falls to a much lower value when a fault occurs resulting into non-operation of the relay. Directional Overcurrent Ground Relays Types IRP, IRC and IRD in each winding at the maximum torque angle for the directional units used with the 0.5 to 2.5 and 2 to 6 ampere range time overcurrent units. The IBC relays consist of two units, an instantaneous power-directional unit (bottom) of the induction-cup type, and a time overcurrent unit (top) of the induction-disk type. THE USE OF THE R-X DIAGRAM IN RELAY WORK INTRODUCTION Practical system economics demand heavier line loadings than were considered possible years ago. Contacts must close to inhibit overcurrent relay. Overcurrent is used for automatic testing of directional and non-directional overcurrent relays with auto-assessment of the trip time characteristic, the directional boundaries of the current stages, and the pick-up/drop-off ratio. 3. Directional overcurrent relays are constructed using a normal overcurrent unit plus a unit that can determine the direction of the power flow in the associated distribution system element. The directional unit consists of upper electromagnet excited from potential transformer (PT), so it produces flux proportional to voltage. 1x. On detection of a fault, the relay will start, trip the circuit breaker, provide alarms, record fault data, etc., in accordance with the application and the configured relay functions. Directional overcurrent relays (67) respond to excessive current flow in a particular direction in the power system. The IBC directional overcurrent relays are employed primarily for the protection of feeders and trans-mission lines in applications where single-phase relays are desired or required. In case of directional relay it is necessary to set correct MTA for over current as well as earth fault relay. Three conditions must be satisfied for its operation: current magnitude, time delay and directionality. The other overcurrent unit is used to start carrier signal transmission. Explain with block diagram Microprocessor based Over Current Relay 16. n GE JBC Phase Directional Overcurrent Relay • Uses quadrature polarizing voltage • Has an MTA of 45 degrees • Has a pickup of 2VA at MTA • Has a directionally controlled instantaneous unit . If we reversed the source and load, you could swap the phasor diagrams above for each relay. These increased loadings have focused attention on system stability and its horde of associated prob-lems. Explain construction and working of Static Type Over Current Relay 14. Modern microprocessor-based directional relays have a definite advantage in this regard over legacy electromechanical relay designs, in being able to intelligently select the best polarizing quantity to use during fault conditions. Explain with a neat … Play. WITH EXTERNAL DIAGRAMS 52 Power Circuit Breaker 67 - Directional Overcurrent Relays, Type mc or Type mcv 67N - Directional Ground Relay, Type mCG a - Auxiliary Contact, 0;> en when Breaker Opens Dill - Directional Unit SI - Seal-in Unit with Target OC - Overcurrent Unit TC - Trip Coil PC - Polarizing Coil (Dir 0 Unit) RC - Restraining Coil (Dir 0' Unit) , A-C BUS TO POTENT I AL +-+--'---COI …