GE D30 Instruction Manual

Also see for D30 series: Communications manual Communications guide Instruction manual Instruction manual Instruction manual

Contents

5-6 D30 LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUALOVERVIEW CHAPTER 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 can 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, andsummation 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 protectionfeatures that 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 userto select which sets of CT inputs are to be added to form the net current into the protected device.The internal grouping of current and voltage signals forms an AC source. This source can be given a specific name throughthe settings and becomes available to protection and metering elements in the UR platform. Individual names can begiven to each source to help identify them for later use. For example, in the scheme shown in the preceding figure, the userconfigures one source to be the sum of CT1 and CT2 and can name this source as “Wdg1 I.”Once the sources have been configured, the user has them available as selections for the choice of input signal for theprotection elements and as metered quantities.5.2.2.2 CT/VT module configurationCT and voltage transformer (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 waveformRMS levels, fundamental frequency phasors, symmetrical components, and harmonics for voltage or current, as allowedby the hardware in each channel. These modules can 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,and from 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