Three-phase instantaneous overcurrent
protection function block description
Document ID: PRELIMINARY VERSION
Budapest, October 2009
Three-phase instantaneous overcurrent protection
User’s manual version information
Version
Preliminary
Date
30.10.2009
18.06.2010
PRELIMINARY VERSION
Modification
Compiled by
Preliminary version, without technical information Petri
Technical information added
Petri
2/12
Three-phase instantaneous overcurrent protection
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
PRELIMINARY VERSION
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Three-phase instantaneous overcurrent protection
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
t (G) tOP when G
GS
t(G)
tOP
G
GS
2*GS
Figure 1-1 Overcurrent independent time characteristic
where
tOP (seconds)
G
GS
theoretical operating time if G> GS (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
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Three-phase instantaneous overcurrent protection
1.2 Structure of the instantaneous overcurrent protection
algorithm
Fig.1-2 shows the structure of the instantaneous overcurrent protection (TOC50) algorithm.
Preparation
IL1
IOC50
Fourier IL1
Decision
logic
IL2
Fourier IL2
Instant.
decision
IL3
Fourier IL3
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
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Three-phase instantaneous overcurrent protection
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.
IL1
IL1Four
IL2
IL2Four
IL3
IL3Four
Fourier
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).
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Three-phase instantaneous overcurrent protection
1.4 The peak selection (Peak selection)
These modules select the peak values of the phase currents individually.
IL1
IL1Peak
IL2
IL2Peak
IL3
Peak
selection
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
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Three-phase instantaneous overcurrent protection
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
IL1Peak
IL2Peak
IL3Peak
Binary outputs
Instantaneous
decision
Parameters
Figure 1-5 Principal scheme of the instantaneous characteristic calculation
Enumerated parameter
Parameter name
Title
Parameter for type selection
IOC50_Oper_EPar_ Operation
Selection range
Default
On,Off,Peak value,Fundamental value
On
Table 1-1 The enumerated parameters of the instantaneous overcurrent protection
function
Integer parameter
Parameter name
Title
Starting current parameter:
IOC50_StCurr_IPar_
Start current
Unit
Min
Max
Step
Default
%
20
3000
1
200
Table 1-2 The integer parameters of the instantaneous overcurrent protection
function
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Three-phase instantaneous overcurrent protection
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
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 function
The binary output status signals of the three-phase instantaneous overcurrent protection
function are listed in Table 1-4.
Binary output signals
IOC50_TrL1_ GrI_
IOC50_TrL2_ GrI_
IOC50_TrL3_ GrI_
Signal title
Trip L1_i
Trip L2_i
Trip L3_i
Explanation
Trip command of the function in phase L1
Trip command of the function in phase L2
Trip command of the function in phase L3
Table 1-4 The binary output status signals of the instantaneous overcurrent protection
function
PRELIMINARY VERSION
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Three-phase instantaneous overcurrent protection
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.
IOC50_TrL1_ GrI_
IOC50_GenTr_GrI_
OR
IOC50_TrL2_ GrI_
AND
IOC50_TrL3_ GrI_
IOC50_Blk_GrO_
NOT
Figure 1-6 The logic scheme of the instantaneous overcurrent protection function
Binary input signals
IOC50_TrL1_GrI_
IOC50_TrL2_GrI_
IOC50_TrL3_GrI_
Signal title
Trip L1
Trip L2
Trip L3
Explanation
Trip command of the function in phase L1
Trip command of the function in phase L2
Trip command of the function in phase L3
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
IOC50_Blk_GrO_
Explanation
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
Binary output signals
IOC50_GenTr_GrI_
Signal title
General Trip
Explanation
General trip command of the function
Table 1-7 The binary output status signals of the instantaneous overcurrent protection
function
PRELIMINARY VERSION
10/12
Three-phase instantaneous overcurrent protection
1.7 Technical summary
1.7.1 Technical data
Function
Operating characteristic
Reset ratio
Operate time at 2*In
Reset time
Instantaneous
0.95
Peak value calculation
Fourier calculation
16 – 25 ms
<2%
<15 ms
<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.
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Three-phase instantaneous overcurrent protection
1.7.3 Binary output status signals
The binary output status signals of the instantaneous overcurrent protection function are
shown in Table 1-9.
Binary output signals
IOC50_TrL1_GrI_
IOC50_TrL2_GrI_
IOC50_TrL3_GrI_
IOC50_GenTr_GrI_
Signal title
Trip L1
Trip L2
Trip L3
General Trip
Explanation
Trip command of the function in phase L1
Trip command of the function in phase L2
Trip command of the function in phase L3
General trip command of the function
Table 1-9 The binary output status signals of the instantaneous overcurrent protection
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
IOC50_Blk_GrO_
IOC50_Doubl_GrO_
Explanation
Output status of a graphic equation defined by the user to
disable the instantaneous overcurrent protection function.
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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