Practical Example of Use
Testing Directional Overcurrent Protection Author OMICRON electronics Date September 2010 Related OMICRON Product Test Universe Application Area Area Overcurrent Version DirOvcrEx.AE.1
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Content Preface ......................................................................................................................................................... ......................................................................................................................................................... 3 1
Application Example ............................................................................................................................ ............................................................................................................................ 3
2
Theoretical Theoretical Introduction Introduction .......................................................... ...................................................................................................................... ............................................................ 4 2.1 Tripping Characteristics .......................................................................... ................................................................................................................. ....................................... 4 2.2 IDMT-Characteristics (51, 51N, 67) ........................................................................................ ............................................................................................... ....... 5 2.3 Directional Overcurrent Protection (67) ......................................................................................... ......................................................................................... 6
3
Practical Introduction Introduction ......................................................................... ........................................................................................................................... .................................................. 8 3.1 Defining the Test Object ................................................................................................................ ................................................................................................................ 9 3.1.1 3.1.2
3.2
Device Settings ............................................................ .................................................................... . 9 Defining the Overcurrent Protection Parameters ................................................................ ............ 10
Global Hardware Configuration Configuration CMC ................................................................ .......................................................................................... .......................... 14 3.2.1 Output Configuration for Protection Relays with a Secondary Nominal Current of 1 A ................... 14 3.2.2 Output Configuration for Protection Relays with a Secondary Nominal Current of 5 A ................... 15 3.2.3 Analog Outputs ............................................................ ................................................................... 16 3.2.4 Binary Inputs ................................................................ .................................................................. . 16 3.2.5 Wiring of the Test Set ..................................................................................................................... 17
3.3
Defining the Test Configuration .................................................................................... ................................................................................................... ............... 18 3.3.1 3.3.2 3.3.3 3.3.4
General Approach ........................................................ ................................................................... 18 Pick-up Test ................................................................. .................................................................. . 18 Trip Time Characteristic Test .............................................................. ............................................ 19 Directional characteristic test .............................................................. ............................................ 21
Please use this note only in combination with the related product manual which contains several important safety instructions. The user is responsible for every application that makes use of an OMICRON product.
OMICRON electronics GmbH including all international branch offices is henceforth referred to as OMICRON. © OMICRON 2010. All rights reserved. This application note is a publication of OMICRON. All rights including translation reserved. reserved. Reproduction of any kind, kind, for example, photocopying, photocopying, microfilming, optical character recognition and/or storage in electronic data processing systems, requires the explicit consent of OMICRON. Reprinting, wholly or in part, is not permitted. The product information, specifications, and technical data embodied in this application note represent the technical status at the time of writing and are subject to change without prior notice. We have done our best to ensure that the information given in this application note is useful, accurate and entirely reliable. However, OMICRON does not assume responsibility for any inaccuracies which may be present. OMICRON translates translates this application note from the source language English into a number of other languages. Any translation of this document is done for local requirements, and in the event of a dispute between the English and a nonEnglish version, the English version of this note shall govern.
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Preface This paper describes how to test directional and non-directional overcurrent protection stages. It contains an application example which will be used in the whole paper. The theoretical background of the directional and non-directional overcurrent protection will be explained. Also this paper covers the definition of the overcurrent overcurrent Test Object as Object as well as the Hardware Configuration for Configuration for directional overcurrent tests. Finally the Overcurrent test module is used to perform the tests which are needed for the directional overcurrent protection function. Supplements: Sample Supplements: Sample Control Center file Overcurrent file Overcurrent Example.occ (referred to in this document). Requirements: Test Universe 2.40 or later; Overcurrent and and Control Center licenses. licenses.
1
Application Example Protection functions
10.5 kV
I> stage (67) / directional characteristic forward (IDMT) I>> stage (50) non-directional characteristic (DMT) 200/1
Figure 1: Feeder connection diagram of the application example Parameter Name
Parameter Value
Frequency
50 Hz
VT (primary/secondary)
10500 V / 110 V
CT (primary/secondary)
200 A /1 A IEC Very Inverse
Tripping characteristic
Directional Directio nal Fwd
Directional characteristic characterist ic Forward
300 A
Pick-up value = 1.5 x In CT primary
1.2
DMT
Time multiplier (TD; TMS; P, etc. (only for IDMT characteristics) Relay characteristic characterist ic angle (only for directional protective function) Tripping characteristic
600 A
Pick-up value = 1.5 x In CT primary
100 ms
Trip time delay
I> stage
45 ° I>> stage
Notes
Table 1: Relay parameters for this example
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2
Theoretical Introduction
2.1
Tripping Characteristics Tripping characteristics
Definite Minimum Time overcurrent relay
Inverse-Definite Minimum Time overcurrent relay
trip-time characteristic of a two-step DMT-overcurrent relay
trip-time characteristic of a IDMT- overcurrent relay t[s]
t[s]
t I>
t I>
t I>>
t I>>
I/In
I>
I>>
50-1 or 50N-1
50-2 or 50N-2
IP
I>>
I/IP
51 or 51N or 67
Characteristic
Formula
LTI (long time inverse)
t
SI (standard inverse)
t
VI (very inverse)
t
EI (extremely inverse)
t
Annotation
120
I
I P
1
T P
0.14
I
I P
0.02
13.5
I
I P
1
I
I P
T P
T P
80 2
1
Suitable for motors, for example.
1
T P
Good adjustment on fuse tripping characteristics possible.
Table 2: IDMT tripping characteristics (range / show IEC 60255-3 or BS 142, section 3.5.2) t TP or TMS I IP
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= = = =
trip time in seconds setting value of the time multiplier fault current setting value of the pick-up current
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2.2
IDMT-Characteristics (51, 51N, 67) As these characteristics characteristics differ considerably considerably from each each other, the operational operational equipment equipment to be protected has to be taken into account (overload, short-circuit behavior, etc.).
1 3
2
4
5
6
7
8
Figure 2: Parameters of an overcurrent relay (AREVA) 1. 2. 3. 4. 5. 6. 7. 8.
Tripping characteristic for for the I> stage (for (for this example example IDMT IEC very inverse) Directional function (for this example forward) Pick-up value of I> stage Time multiplier for the I> stage Tripping characteristic for for the I>> I>> stage (DMT for this example) example) Pick-up value of I>> stage Trip time delay of I>> stage Relay characteristic characteristic angle RCA (only for the directional function)
4
1
7
3
6
Figure 3: Comparison of IEC very inverse tripping characteristics with different time multiplier
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2.3
Directional Overcurrent Protection (67) A factor which is characteristic characteristic to the short-circuit short-circuit is the angle angle between short-circuit voltage and short-circuit current. This angle depends on the voltage level and the respective operational equipment equipment (overhead line, cable and transformer). First of all it shall be examined more closely.
Short circuit angle
380 kV
220 kV
110 kV
10 – 30 kV
Electric arc
Approx. 85 °
Approx. 80 °
Approx. 72 °
30 - 50 °
Approx. 0 °
Table 3: Short-circuit angle of overhead lines and cables depending on the voltage level The short-circuit angle sc can be calculated from the resistance R and the reactance X of the protected object.
sc
arctan
X R
It is clear that the short-circuit current has to be used for determining the direction. For the selection of the voltage to be applied the following conditions have to be taken into account:
For a close fault the short-circuit voltage is almost zero. The angle angle of the directional directional characteristic characteristic depends depends on the fault type (L1-E, L2-E, etc.). In order order to determine the correct position of the forward and the reverse direction, the relay needs a reference voltage.
For this, relay connections have been developed which make use of different reference voltages with corrected phase angles. Connections
Advantages
Disadvantages
0 Iph , V ph
Maximum sensitivity with arc faults.
Not feasible in HV-systems, no decision with a close fault. Reference voltage depending on the fault.
Maximum reference voltage with PhE- and PhPh- faults.
Not feasible for arc faults.
30 Iph , Vph
Vph a
60 Iph , Vph a
90
Iph, Vph
a
2
Vph a
Table 4: Relay connection for determining determining the reference voltage. Note: The Note: The method that is used for the reference voltage depends on the relay manufacturer. For the following discussion, discussion, we use the overcurrent relay P14x (AREVA).
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Im
reverse direction
Vc forward direction
Va φsc
Vb directional characteristic line
45° -Vc
Vsc
Re
I sc
-45° Vref
Vref =Vb -V - Vc
Figure 4: 90 ° relay connection with a relay characteristic angle of 45 ° (L1-E fault) Note: The forward direction for the measuring element "phase A" results from the angle range 45 ° > sc > -135 °.
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3
Practical Introduction The Overcurrent test test module is designed for testing directional and non-directional overcurrent protective functions with DMT or IDMT tripping characteristics (short-circuit, thermal overload, overload, zero sequence, negative sequence, and customized curve characteristics). The test module can be found at the Start Page of Page of the OMICRON Test Universe. Universe. It can be inserted into an OCC File as well.
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3.1
Defining the Test Object The first step of testing is defining the settings of the relay under test. In order to do that, the Test Object has Object has to be opened. This can be done by double clicking the Test Object in Object in the OCC file or by clicking the Test Object button Object button in the test module.
3.1.1
Device Settings General relay settings (e.g., substation, relay ID, CT and VT parameters) are entered at Device Settings. Settings.
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3.1.2
Defining the Overcurrent Protection Parameters More specific data concerning the overcurrent relay can be entered in the RIO function Overcurrent Protection Parameters . The definition of the overcurrent characteristic has to be done here as well. Relay Parameters This first tab contains the definition of the directional behavior as well as the relay tolerances.
1
2
3
4
1. 2. 3.
4.
Since we want to test a directional overcurrent relay, this has to be activated. Regarding the feeder connection diagram (Figure 1) the 1) the VT is placed At protected object. object . If you choose Not at protected object , the voltage will have the nominal value after tripping. The CT starpoint connection has connection has to be set according to the connection of the secondary windings of the CT. For this example the feeder connection diagram shows, shows, that the CT grounding is towards the protected object. The current and time tolerances have to be looked up in the relay manual.
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Elements This tab defines the characteristic of the different overcurrent stages.
1 5 2
3
4 The default overcurrent characteristic is shown above. It contains an IEC Definite Time scheme with one stage for a phase overcurrent protection. This characteristic has to be adjusted to parameters of the relay (Table 1): 1): 1.
2.
3. 4. 5.
In order to define the elements of the phase overcurrent protection, select Phase as Phase as the Selected element type. type . Note: In Note: In case other element types would also be present in the r elay select the related element types one after another in (1) to (1) to enter these elements. The selection field shows the number of already defined related stages and how many of these are marked as active. This table shows the elements which define the tripping characteristic for the selected element type. The name of the first element may be changed according to the name used in the relay, e.g. "I> stage". The characteristic type of the first element has to be changed to IEC Very inverse ( inverse (Error! Error! Reference source not found.). found. ). Afterwards I pick-up pick-up and the Time index have index have to be set. Now the second element can be added. It has an IEC Definite Time characteristic, Time characteristic, which might be renamed to "I>> stage". Also I pick-up and pick-up and the Trip time have time have to be set.
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3
4 The list of the elements after these adjustments is shown below.
1
1. 2.
2
The Reset Ratio has Ratio has to be looked up in the manual as well. In order to define the directional behavior, behavior, the Direction of the "I> stage" has to be set to Forward. Note: This Note: This setting is an orientation help for the reader, and, once it is set, it will rotate the directional limits by 180 ° if changed to Backward. Backward .
The adjustments of the directional characteristic have to be done in the tab Define Element Directional Behavior :
3.
As the relay characteristic characteristic angle cannot cannot be entered entered in the Test Object directly, Object directly, the Trip sector definition has definition has to be calculated. Figure calculated. Figure 5 shows the difference between the relay characteristic angle, which is a relay setting, and the Maximum torque angle that angle that can be set in the Test Object. Object.
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Im
reverse direction
Vc forward direction
Va
Vsc
Re
maximum torque angle (MTA) Vb directional characteristic line
-45° Vref
MTA = -90° + RCA
-Vc Vref =Vb -V - Vc
relay characteristic angle (RCA)
Figure 5: Difference between the relay characteristic angle and the maximum torque angle. The resulting overcurrent characteristic is shown below.
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3.2
Global Hardware Configuration CMC The global Hardware Configuration has Configuration has to be defined according to your relay connection. It can be started by double clicking the Hardware Configuration entry Configuration entry in the OCC file.
3.2.1
Output Configuration for Protection Relays with a Secondary Nominal Current of 1 A
V A
VC VB
Vn
I A IB IC In
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3.2.2
Output Configuration for Protection Relays with a Secondary Nominal Current of 5 A
V A
VC VB
I A
IC IB
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Vn
In
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3.2.3
Analog Outputs
The analog outputs as well as the binary inputs and binary outputs can be activated individually in the local Hardware Configuration of Configuration of the specific test module. 3.2.4
Binary Inputs 4
3
1
1. 2. 3. 4.
2
The start command is optional (it is needed if you select Starting as Starting as time reference in the test module or if you want to perform a pick-up / drop-off test). The trip command has to be connected to a binary input. You can use BI1 … BI10. For wet contacts the nominal voltages of the binary inputs have to be adapted to the voltage of the CB trip command. Or check Potential Free for Free for dry contacts. The binary outputs, the analog inputs etc. will not be used for the following tests.
t r a t
S p i r T
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3.2.5
Wiring of the Test Set Note: The Note: The following wiring diagram is an example, only. Depending on the protective functions of the relay such as sensitive earth fault protection, the wiring of the analog current inputs (I E separately) is different.
Protective Relay
Va Vb Vc (-) (-)
Ia Ib Ic IE
optional
(+)
(+)
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Trip Start
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3.3
Defining the Test Configuration
3.3.1
General Approach When testing the directional overcurrent protection, the following steps are recommended:
Pick-up Test: Test: Testing the pick-up value of the overcurrent protection (only if start contact is wired for this relay). Trip time characteristic: characteristic : Verifying the trip times of every element of the tripping characteristic. Directional characteristic: characteristic : Verifying the angle of the directional characteristic.
Each of these tests can be done with the Overcurrent test test module.
3.3.2
Pick-up Test 2
1
3
4
1.
2. 3. 4.
5
6
The trigger for this test has to be set in the Trigger tab. tab. For this example the trigger will be the start contact. This is the reason why this test cannot be performed if the start contact is not wired. Settings in the Fault tab Fault tab will not be needed in this test. As we use the start start contact to trigger, trigger, Relay with start contact has contact has to be chosen. The phase overcurrent function is tested with a three phase fault. Otherwise a ground fault protection or a negative sequence sequence protection may interfere.
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5. 6.
Note: If Note: If these functions or elements are present they may be specified in the Test Object in Object in the same manner as the phase elements were entered in this example. The resulting characteristic will individually be calculated and shown for each test shot depending on its fault type (4) and (4) and fault angle (5), (5), ensuring a proper assessment according to the expected overall relay behavior. The test angle for the forward direction should be the maximum torque angle. As the pick-up is not not delayed, delayed, a step length of 50 ms should should be sufficient. sufficient.
Note: Note: The pick-up value will be measured and assessed automatically. automatically. The drop-off value will be measured as well, but it will not be assessed. The assessment of the drop-off value and the reset ratio has to be done manually. You can add more test lines if needed, e.g., a test in backward direction.
3.3.3
Trip Time Characteristic Test Trigger and and Fault tabs: Fault tabs:
2
1
1. 2. 3.
3
The trigger for this test will be the trip contact. A Load current during current during the prefault state will not be used. The Absolute max. time has time has to be adjusted. It has to exceed the upper tolerance of the test point with the longest trip time. Otherwise an assessment will not be possible. On the other hand, it should not be set to an unnecessarily high value since for shots where No trip is trip is expected this will be the waiting time until the assessment 'no trip' is done, before continuing with the next shot, so this would unnecessarily prolong the test duration.
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Characteristic Test tab: Test tab:
1
2 3 4 5
6
1.
2. 3. 4. 5. 6.
As the function to test is a phase overcurrent function, function, a three phase phase fault is used. used. Otherwise a ground fault protection or a negative sequence protection may interfere. NOTE: If these functions or elements are present they may be specified in the Test Object in the same manner as the phase elements were entered in this example. The resulting characteristic will individually be calculated and shown for each test shot depending on its fault type (1) and (1) and fault angle (2), (2), ensuring a proper assessment according to the expected overall relay behavior. The Angle for Angle for the forward direction should be the Maximum torque angle. angle. For reverse direction it has to be entered shifted by 180 °. As the trip time of the the IDMT stage depends depends on the current, this element element has to be confirmed with more than one test point. Whereas the trip time of the "I>> stage" can be confirmed with only one test point. The directional behavior is tested with one shot in each zone in reverse direction. The value of the "I>> stage" is also confirmed by placing two test points outside of the tolerance band of this setting. Instead of directly entering the magnitude value you can express the magnitude by its relation to an element setting, e.g., set Relative to: to to: to "I>> stage" and set the factor to 1.06 (i.e. 6 % above the threshold) or 0.94 (i.e. 6 % below the threshold).
Note: Regarding Note: Regarding the ways to enter and modify test data please also have a look at the Help of the module (press F1).
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3.3.4
Directional characteristic test
The Trigger and and Load settings are settings are the same as explained for the trip time characteristic test. The Absolute max. time can time can be reduced, because the test current will be set shortly below the lower tolerance of the "I>> stage" value.
As this test confirms confirms the angle of of the directional directional characteristic, the test test points have to be placed on on both sides of the directional characteristic line. In order to get a correct assessment, they should be placed just outside of the angle tolerance.
Feedback regarding this application is welcome under
[email protected] [email protected]..
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