Three-phase instantaneous overcurrent protection function block description

Transcription

1 Three-phase instantaneous overcurrent protection block description Document ID: PRELIMINARY VERSION

2 User s manual version information Version Date Modification Compiled by Preliminary Preliminary version, without technical information Petri Technical information added Petri PRELIMINARY VERSION 2/12

3 CONTENTS 1 Instantaneous overcurrent protection Operating characteristics Structure of the instantaneous overcurrent protection algorithm The Fourier calculation (Fourier) The peak selection (Peak selection) The instantaneous decision (Instantaneous decision) The decision logic (Decision logic) Technical summary Technical data The parameters Binary output status signals The binary input status signals The block PRELIMINARY VERSION 3/12

4 1 Instantaneous overcurrent protection The instantaneous overcurrent protection operates according to instantaneous characteristics, using the three sampled phase currents. The setting value is a parameter, and it can be doubled by graphic programming of the dedicated input binary signal. The basic calculation can be based on peak value selection or on Fourier basic harmonic calculation, according to the parameter setting. 1.1 Operating characteristics t(g) t G) ( when G GS t OP t OP G G S 2*G S Figure 1-1 Overcurrent independent time characteristic where t OP (seconds) G G S theoretical operating time if G> G S (without additional time delay), measured value of the characteristic quantity, peak values or Fourier base harmonic of the phase currents, setting value of the characteristic quantity (IOC50_StCurr_IPar_, Start current). PRELIMINARY VERSION 4/12

5 1.2 Structure of the instantaneous overcurrent protection algorithm Fig.1-2 shows the structure of the instantaneous overcurrent protection (TOC50) algorithm. Preparation IOC50 IL1 IL2 Fourier IL1 Fourier IL2 Decision logic IL3 Fourier IL3 Instant. decision Binary outputs Peak IL1 Peak IL2 Peak IL3 Parameters Status signals Figure 1-2 Structure of the instantaneous overcurrent protection algorithm The inputs are the sampled values of three phase currents, the RMS values of the fundamental Fourier component of three phase currents, parameters, status signals. The outputs are the binary output status signals. PRELIMINARY VERSION 5/12

6 The software modules of the differential protection : Fourier calculations These modules calculate the RMS values of the fundamental Fourier component of three phase currents individually (not part of the IOC50 ). Peak selection These modules select the peak values of the phase currents individually. Instantaneous decision This module compares the peak value or the Fourier basic harmonic components of the phase currents with the setting value. Decision logic The decision logic modules generate the trip command of the. The following description explains the details of the individual components. 1.3 The Fourier calculation (Fourier) These modules calculate the RMS values of the fundamental Fourier component of the three phase currents individually. They are not part of the IOC50 ; they belong to the preparatory phase. IL1 IL2 IL3 Fourier IL1Four IL2Four IL3Four Figure 1-3 Principal scheme of the Fourier calculation The inputs are the sampled values of the three phase currents (IL1, IL2, IL3). The outputs are the RMS values of the fundamental Fourier component of three phase currents (IL1Four, IL2Four, IL3Four). PRELIMINARY VERSION 6/12

7 1.4 The peak selection (Peak selection) These modules select the peak values of the phase currents individually. IL1 IL2 IL3 Peak selection IL1Peak IL2Peak IL3Peak Figure 1-4 Principal scheme of the peak selection The inputs are the sampled values of the three phase currents (IL1, IL2, IL3). The outputs are the peak values of the analyzed currents (IL1Peak, IL2 Peak, IL3 Peak). PRELIMINARY VERSION 7/12

8 1.5 The instantaneous decision (Instantaneous decision) This module generates a trip command without additional time delay based on the Fourier components of the phase currents, or based on the peak values if the detected values are above the current setting value. The inputs are the RMS values of the fundamental Fourier component of three phase currents (IL1Four, IL2Four, IL3Four), the peak values (IL1Peak, IL2 Peak, IL3 Peak), parameters and status signals. The outputs are the status signals of the three phases individually. These indicate the generated trip command if the currents are above the current setting value. IL1Four IL2Four IL3Four Binary outputs IL1Peak IL2Peak IL3Peak Instantaneous decision Parameters Figure 1-5 Principal scheme of the instantaneous characteristic calculation Enumerated parameter Parameter name Title Selection range Default Parameter for type selection IOC50_Oper_EPar_ Operation On,Off,Peak value,fundamental value On Table 1-1 The enumerated parameters of the instantaneous overcurrent protection Integer parameter Parameter name Title Unit Min Max Step Default Starting current parameter: IOC50_StCurr_IPar_ Start current % Table 1-2 The integer parameters of the instantaneous overcurrent protection PRELIMINARY VERSION 8/12

9 Binary status signal The decision block of the instantaneous overcurrent protection has a binary input signal, which serves the purpose of doubling the setting value of the. The conditions are defined by the user, applying the graphic equation editor. Binary status signal IOC50_Doubl_GrO_ Explanation If this status signal is logic TRUE then the value of the parameter Start current is doubled Table 1-3 The binary input signal for the decision block of the instantaneous overcurrent protection The binary output status signals of the three-phase instantaneous overcurrent protection are listed in Table 1-4. Binary output signals Signal title Explanation IOC50_TrL1_ GrI_ Trip L1_i Trip command of the in phase L1 IOC50_TrL2_ GrI_ Trip L2_i Trip command of the in phase L2 IOC50_TrL3_ GrI_ Trip L3_i Trip command of the in phase L3 Table 1-4 The binary output status signals of the instantaneous overcurrent protection PRELIMINARY VERSION 9/12

10 1.6 The decision logic (Decision logic) The decision logic module combines the status signals, binary and enumerated parameters to generate the trip command of the. IOC50_TrL1_ GrI_ IOC50_TrL2_ GrI_ IOC50_TrL3_ GrI_ OR AND IOC50_GenTr_GrI_ IOC50_Blk_GrO_ NOT Figure 1-6 The logic scheme of the instantaneous overcurrent protection Binary input signals Signal title Explanation IOC50_TrL1_GrI_ Trip L1 Trip command of the in phase L1 IOC50_TrL2_GrI_ Trip L2 Trip command of the in phase L2 IOC50_TrL3_GrI_ Trip L3 Trip command of the in phase L3 Table 1-5 The binary input status signals of the instantaneous overcurrent protection Binary status signal The instantaneous overcurrent protection has a binary input signal, which serves the purpose of disabling the. The conditions of disabling are defined by the user, applying the graphic equation editor. Binary status signal IOC50_Blk_GrO_ Explanation Output status of a graphic equation defined by the user to disable the instantaneous overcurrent protection. Table 1-6 The binary input signal of the instantaneous overcurrent protection Binary output signals Signal title Explanation IOC50_GenTr_GrI_ General Trip General trip command of the Table 1-7 The binary output status signals of the instantaneous overcurrent protection PRELIMINARY VERSION 10/12

11 1.7 Technical summary Technical data Function Operating characteristic Instantaneous <2% Reset ratio 0.95 Operate time at 2*In Peak value calculation <15 ms Fourier calculation <25 ms Reset time ms Table 1-8 Technical data of the instantaneous overcurrent protection The parameters The parameters are summarized in Chapter 1.5. PRELIMINARY VERSION 11/12

12 1.7.3 Binary output status signals The binary output status signals of the instantaneous overcurrent protection are shown in Table 1-9. Binary output signals Signal title Explanation IOC50_TrL1_GrI_ Trip L1 Trip command of the in phase L1 IOC50_TrL2_GrI_ Trip L2 Trip command of the in phase L2 IOC50_TrL3_GrI_ Trip L3 Trip command of the in phase L3 IOC50_GenTr_GrI_ General Trip General trip command of the Table 1-9 The binary output status signals of the instantaneous overcurrent protection The binary input status signals Binary input signals The instantaneous overcurrent protection has a binary input signal, which serves the purpose of disabling the. The conditions of disabling are defined by the user, applying the graphic equation editor. Binary input signal IOC50_Blk_GrO_ IOC50_Doubl_GrO_ Explanation Output status of a graphic equation defined by the user to disable the instantaneous overcurrent protection. If this status signal is logic TRUE then the value of the parameter Start current is doubled Table 1-10 The binary input signal of the instantaneous overcurrent protection The block The block of the instantaneous overcurrent protection is shown in Figure 1-7. This block shows all binary input and output status signals that are applicable in the graphic equation editor. Figure 1-7 The block of the instantaneous overcurrent protection PRELIMINARY VERSION 12/12