three-phase instantaneous overcurrent protection … instantaneous overcurrent protection function...

Three-phase instantaneous overcurrent protection function block description

Document ID: PRELIMINARY VERSION

Budapest, October 2009

Three-phase instantaneous overcurrent protection

PRELIMINARY VERSION 2/12

User’s manual version information

Version Date Modification Compiled by

Preliminary 30.10.2009 Preliminary version, without technical information Petri

18.06.2010 Technical information added Petri



CONTENTS 1 Instantaneous overcurrent protection function ....................................................................4

1.1 Operating characteristics .............................................................................................4

1.2 Structure of the instantaneous overcurrent protection algorithm .................................5

1.3 The Fourier calculation (Fourier) .................................................................................6

1.4 The peak selection (Peak selection) ............................................................................7

1.5 The instantaneous decision (Instantaneous decision).................................................8

1.6 The decision logic (Decision logic) ........................................................................... 10

1.7 Technical summary ................................................................................................... 11 1.7.1 Technical data .................................................................................................... 11 1.7.2 The parameters .................................................................................................. 11 1.7.3 Binary output status signals ............................................................................... 12 1.7.4 The binary input status signals .......................................................................... 12 1.7.5 The function block .............................................................................................. 12



1 Instantaneous overcurrent protection function The instantaneous overcurrent protection function 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

OPtGt )( when SGG

Figure 1-1 Overcurrent independent time characteristic

where tOP (seconds) theoretical operating time if G> GS (without additional time delay), G measured value of the characteristic quantity, peak values or Fourier

base harmonic of the phase currents, GS setting value of the characteristic quantity (IOC50_StCurr_IPar_,

Start current).

G

GS

tOP

t(G)

2*GS



1.2 Structure of the instantaneous overcurrent protection algorithm

Fig.1-2 shows the structure of the instantaneous overcurrent protection (TOC50) algorithm.

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.

Status signals

IL1

Instant. decision

Binary outputs

Parameters

IL2

IL3

Fourier IL1 Decision

logic

Fourier IL2

Fourier IL3

IOC50

Peak IL1

Peak IL2

Peak IL3

Preparation



The software modules of the differential protection function:

Fourier calculations

These modules calculate the RMS values of the fundamental Fourier component of three phase currents individually (not part of the IOC50 function).

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 function. 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 function; they belong to the preparatory phase.

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).

IL1

IL2

IL3

IL1Four

IL2Four

IL3Four

Fourier



1.4 The peak selection (Peak selection) These modules select the peak values of the phase currents individually.

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).

IL1

IL2

IL3

IL1Peak

IL2Peak

IL3Peak Peak selection



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.

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

function

Integer parameter

Parameter name Title Unit Min Max Step Default

Starting current parameter:

IOC50_StCurr_IPar_ Start current % 20 3000 1 200

Table 1-2 The integer parameters of the instantaneous overcurrent protection

function

IL1Four

Binary outputs

Instantaneous decision

Parameters

IL2Four

IL3Four

IL1Peak IL2Peak

IL3Peak



Binary status signal The decision block of the instantaneous overcurrent protection function has a binary input signal, which serves the purpose of doubling the setting value of the function. The conditions are defined by the user, applying the graphic equation editor.

Binary status signal Explanation

IOC50_Doubl_GrO_ 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 function

The binary output status signals of the three-phase instantaneous overcurrent protection function are listed in Table 1-4.

Binary output signals Signal title Explanation

IOC50_TrL1_ GrI_ Trip L1_i Trip command of the function in phase L1



Table 1-4 The binary output status signals of the instantaneous overcurrent protection

function



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 function.

Figure 1-6 The logic scheme of the instantaneous overcurrent protection function

Binary input signals Signal title Explanation

IOC50_TrL1_GrI_ Trip L1 Trip command of the function in phase L1



Table 1-5 The binary input status signals of the instantaneous overcurrent protection

function

Binary status signal The instantaneous overcurrent protection function has a binary input signal, which serves the purpose of disabling the function. The conditions of disabling are defined by the user, applying the graphic equation editor.

Binary status signal Explanation

IOC50_Blk_GrO_

Output status of a graphic equation defined by the user to disable the instantaneous overcurrent protection function.

Table 1-6 The binary input signal of the instantaneous overcurrent protection function


IOC50_GenTr_GrI_ General Trip General trip command of the function


function

IOC50_TrL1_ GrI_

IOC50_TrL2_ GrI_

OR

IOC50_TrL3_ GrI_

IOC50_GenTr_GrI_

IOC50_Blk_GrO_

AND

NOT



1.7 Technical summary

1.7.1 Technical data

Function

Operating characteristic Instantaneous <2%

Reset ratio 0.95

Operate time at 2*In Peak value calculation

Fourier calculation <15 ms <25 ms

Reset time 16 – 25 ms

Table 1-8 Technical data of the instantaneous overcurrent protection function

1.7.2 The parameters

The parameters are summarized in Chapter 1.5.



1.7.3 Binary output status signals

The binary output status signals of the instantaneous overcurrent protection function are shown in Table 1-9.





IOC50_GenTr_GrI_ General Trip General trip command of the function


function

1.7.4 The binary input status signals

Binary input signals The instantaneous overcurrent protection function has a binary input signal, which serves the purpose of disabling the function. The conditions of disabling are defined by the user, applying the graphic equation editor.

Binary input signal Explanation

IOC50_Blk_GrO_

Output status of a graphic equation defined by the user to disable the instantaneous overcurrent protection function.

IOC50_Doubl_GrO_ 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

function

1.7.5 The function block The function block of the instantaneous overcurrent protection function 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 function block of the instantaneous overcurrent protection function

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three-phase instantaneous overcurrent protection … instantaneous overcurrent protection function...

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