5-6 G60 Generator Management Relay GE Multilin5.1 OVERVIEW 5 SETTINGS5Figure 5–1: BREAKER-AND-A-HALF SCHEMEIn conventional analog or electronic relays, the sum of the currents is obtained from an appropriate external connection ofall CTs through which any portion of the current for the element being protected could flow. Auxiliary CTs are required toperform ratio matching if the ratios of the primary CTs to be summed are not identical. In the UR series of relays, provisionshave been included for all the current signals to be brought to the UR device where grouping, ratio correction and summa-tion are applied internally via configuration settings.A major advantage of using internal summation is that the individual currents are available to the protection device; forexample, as additional information to calculate a restraint current, or to allow the provision of additional protection featuresthat operate on the individual currents such as breaker failure.Given the flexibility of this approach, it becomes necessary to add configuration settings to the platform to allow the user toselect which sets of CT inputs will be added to form the net current into the protected device.The internal grouping of current and voltage signals forms an internal source. This source can be given a specific namethrough the settings, and becomes available to protection and metering elements in the UR platform. Individual names canbe given to each source to help identify them more clearly for later use. For example, in the scheme shown in the abovediagram, the configures one Source to be the sum of CT1 and CT2 and can name this Source as “Wdg 1 Current”.Once the sources have been configured, the user has them available as selections for the choice of input signal for the pro-tection elements and as metered quantities.b) CT/VT MODULE CONFIGURATIONCT and VT input channels are contained in CT/VT modules. The type of input channel can be phase/neutral/other voltage,phase/ground current, or sensitive ground current. The CT/VT modules calculate total waveform RMS levels, fundamentalfrequency phasors, symmetrical components and harmonics for voltage or current, as allowed by the hardware in eachchannel. These modules may calculate other parameters as directed by the CPU module.A CT/VT module contains up to eight input channels, numbered 1 through 8. The channel numbering corresponds to themodule terminal numbering 1 through 8 and is arranged as follows: Channels 1, 2, 3 and 4 are always provided as a group,hereafter called a “bank,” and all four are either current or voltage, as are channels 5, 6, 7 and 8. Channels 1, 2, 3 and 5, 6,7 are arranged as phase A, B and C respectively. Channels 4 and 8 are either another current or voltage.Banks are ordered sequentially from the block of lower-numbered channels to the block of higher-numbered channels, andfrom the CT/VT module with the lowest slot position letter to the module with the highest slot position letter, as follows:INCREASING SLOT POSITION LETTER -->CT/VT MODULE 1 CT/VT MODULE 2 CT/VT MODULE 3< bank 1 > < bank 3 > < bank 5 >< bank 2 > < bank 4 > < bank 6 >UR-seriesrelayCT1 CT2CT3 CT4Winding 1Winding 2Powertransformer827791A3.CDRthrough currentWinding 1current
