Copyrighted material licensed to BR Demo by Thomson Reuters (Scientific), Inc., - 8 - TR62711@IEC:2011(E) Table3-Measuring relays-General MNEMONICS M/I/ GRAPHICAL NAMES DESCRIPTIONS DESIGNATION R/G SYMBOLS D M Directional relay Relay that responds to the relative phase position of a current with respect to another current or voltage reference. NOTE the above definition which applies IEC 60617-S0 basically to a single phase directional relay may be extended to cover a polyphase directional 0104 (2001-07) relay. Df M Differential relay Measuring relay having two windings so connected in different parts of a circuit that the relay will operate if the difference between the p currents in the two circuits exceeds a specified value. IEC 60617-S0 (IEC 60050-811:1991, 811-31-16) 0331 (2001-07) , subscriptions.techstreet.com, downloaded on Nov-28-2014 by James Madison. No further reproduction or distribution is permited. RDf M Ratio (Percentage) Differential relay which functions when the Differential relay difference between two quantities of the same nature exceeds a fixed ratio (percentage) of the smaller quantity. IEC60617-S0 0332(2001-07) G M Ground relay, Earth Relay which operates when a failure of fault relay insulation to earth is detected in the equipment or circuits protected. (IEC 60050-811:1991, 811-31-15) IEC 60617-S0 0200(2001-07) DG M Directional Ground Directional relay used primarily to detect N/A relay single-phase-to-ground faults, but also sensitive to double-phase-to-ground faults. NOTE This type of relay is usually operated from the zero-sequence components of voltage and current, but is sometimes operated from negative-sequence quantities. DfG M Differential Ground Differential relay used primarily to detect N/A relay internal ground faults of generators. s M Short circuit relay Device that operates with no intentional time N/A delay when the current exceeds a preset value. SG M Selecting Ground relay Measuring relay that, by comparing the N/A magnitudes of the zero sequence currents in two parallel lines, will identify a line having ground fault. ss M Selecting Short-circuit Measuring relay that, by comparing the N/A relay magnitudes of the currents in two parallel lines, will identify a line having a short- circuit fault. DS M Directional Directional relay used primarily to detect N/A Short-circuit relay short-circuit faults. TT M Iransfer Irip relay Form of remote trip in which a communication N/A channel is used to transmit a trip signal from the relay location to a remote location. Uncontrolled when printe Copyrighted material licensed to BR Demo by Thomson Reuters (Scientific), Inc., TR62711@IEC:2011(E) - 6 - Table4-Measuringrelays-C Current MNEMONICS M/I/ GRAPHICAL NAMES DESCRIPTIONS DESIGNATION R/G SYMBOLS c M N/A Current relay Actuating when the current quantity is equal to a setting value. BC M Band Current relay Current relay with maximum and minimum setting. <3A IEC 60617-S0 0345(2001-07) CB M Current Balance relay Balance relay that operates by comparing the N/A magnitudes of two current inputs oc M Qver Current relay Measuring relay which operates when the value N/A of the current exceeds the setting (operating value) of the relay. , subscriptions.techstreet.com, downloaded on Nov-28-2014 by James Madison. No further reproduction or distribution is permited. (IEC 60050-811:1991, 811-31-12) DCG M Direct Current Ground Device that functions when the d.c. input N/A relay current exceeds a predetermined value, and in which the input current and operating time are inversely related through a substantial portion of the performance range. OCG M Over Current Ground Device that functions when the net (phasor N/A relay sum) current flowing in the phase and neutral conductors or the total current flowing in the normal neutral to ground connection exceeds a predetermined value. OcV M Over Current relay with Overcurrent relay which is used primarily to N/A Yoltage restraint protect a generator. The functio