Testing With the Ramping Test Module Practical Example of Use
Testing With the Ramping Test Module
Manual Version: Expl_RMP.AE.1 - Year 2011 © OMICRON electronics. All rights reserved. This manual is a publication of OMICRON electronics GmbH. All rights including translation reserved. The product information, specifications, and technical data embodied in this manual 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 manual is useful, accurate, up-to-date and reliable. However, OMICRON electronics does not assume responsibility for any inaccuracies which may be present. The user is responsible for every application that makes use of an OMICRON product. OMICRON electronics translates this manual from the source language English into a number of other languages. Any translation of this manual is done for local requirements, and in the event of a dispute between the English and a non-English version, the English version of this manual shall govern.
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Preface This paper describes how to test the pick-up value of the first overcurrent element. This will be explained for directional or non directional relays with IDMT or DTOC tripping characteristics. It contains an application example which will be used throughout the paper. The theoretical background for testing the pick-up value of the 1st element with the Ramping test module will be explained. This paper also covers the definition of the necessary Test Object settings as well as the Hardware Configuration for testing the 1st element pick-up value of directional or non-directional overcurrent relays. Finally the Ramping test module is used to perform the tests which are needed for testing the pick-up value of different protection relays: > non-directional overcurrent protection relays > directional overcurrent protection relays > distance protection relays with overcurrent starter function, etc. Supplements:
Sample Control Center files Example_Ramping_OvercurrentDirectional_ENU.occ and Example_Ramping_OvercurrentNonDirectional_ENU.occ (referred to in this document). Requirements: Test Universe 2.40 or later; Ramping and Control Center licenses.
Note:
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The Ramping test module can also be used for nearly all pick-up functions for current, voltage and frequency protection etc. For testing the 1st element pick-up value of overcurrent protection relays the Pick-up /Drop-off Test tab in the Overcurrent test module can also be used.
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1
Application Example 10.5 kV Protection functions 1st element (67) / directional characteristic forward (IDMT) 2nd element (50/51) / non-directional characteristic (DTOC)
200/1
Overcurrent Relay
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
1st element
IEC Very Inverse
Tripping characteristic
Directional Fwd
Directional characteristic Forward
300 A
Pick-up 1.5 x In CT primary
DTOC
Time multiplier setting (TD; TMS; P, etc.) (only for IDMT characteristics) Relay characteristic angle (only for directional protection function) Tripping characteristic
600 A
Pick-up 3 x In CT primary
100 ms
Trip time delay
1.2 45°
2
nd
element
Notes
Table 1: Relay parameters for this example
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2
Theoretical Introduction
2.1
Define the Ramps for Testing the Pick-Up Value of the 1st Element In this example we will use the following time and current tolerances to define the test ramps. Parameter Name
Absolute
Relative
Delay time
±10ms
1%
Pick-up current
±10mA
3%
Drop-off / pick-up value Angle faults
1)
95% ±3°
1) only necessary for directional overcurrent relays Table 2: Relay tolerances and technical data (only valid for this example)
Note:
The tolerances depend on the relay type. They can be obtained from the technical specification in the relay manual.
1000
Trip time / s
Very Inverse (element 1) DTOC (element 2) 100
10
1
0.1
0.01 200
300
400
500
600
Ip 1.1·Ip
700
800
Fault current /A
= Pick-up current tolerances of the element 1 (±3% = 1.07·IP … 1.13·IP) = Pick-up current tolerances of the element 2 (±3%) The pick-up value of this element can only be tested with the Pulse Ramping test module!
Figure 2: IDMT trip time characteristic from the example (Table 1) with current tolerances
Note:
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Some relays have an increased pick-up value for IDMT characteristics. For example, the relay used in this example has an actual pick-up value that is 1.1 times higher than the IP setting.
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Trip time / s
2.5
2
DTOC (element 1) 1.5
DTOC (element 2)
1
0.5
200
300
400
500
600
700
800
Fault current / A
= Pick-up current tolerances of the element 1 (±3%) = Pick-up current tolerances of the element 2 (±3%) The pick-up value of this element can only be tested with the Pulse Ramping test module!
Figure 3: DTOC trip time characteristic with current tolerances
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The following parameters will be tested (see Figure 3): 1. 2.
Fault current
3.
Pick-up value of the 1st element (measured) Drop-off value of the 1st element (measured) Drop-off/pick-up value (calculated)
1st element
Drop-off ratio · 1st element
Test time = Pick-up current tolerances (±3%)
= Test current
= Measured pick-up value
= Measured drop-off value
Figure 4: Time signal diagram of a pick-up/drop-off test
These three parameters can be tested with the Ramping test module.
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2.2
Structure of the Ramping Test Module A ramp state is defined as the stepped change of one physical quantity. Several settings can be made in the test module.
1
5
2
3
4
1. 2.
3.
4.
With the Set mode the user can decide whether to ramp the output voltages and currents directly, or whether to ramp calculated values such as symmetrical components, fault values or fault impedances. The Signal type and the Quantity can be set to define the values to be ramped. It is possible to ramp two different signals and quantities at the same time. The signals and quantities that can be chosen are defined by the Set mode. The beginning and the end of the ramps have to be defined for testing. The Delta, which is the step size, as well as the duration between two steps dt also have to be defined. The slope d/dt is calculated automatically. The analog outputs of the Detail View show the values which are generated by the CMC test set. The values displayed with a grey background are modified by the ramp and, therefore, cannot be edited in the detail view. The remaining values can be edited freely. Note: The analog values should be set according to realistic fault values. For example, 180° phase shift of the currents for phase to phase faults.
5.
The trigger which stops the ramp can be set in the Trigger tab of the Detail View. This Stop condition is also displayed in the Test View. This is explained in more detail in the following section.
Note:
The step duration dt has to be set according to the trigger. It must be longer than the trigger time. If the start contact is used, for instance, the step time has to be longer than the starting time. However, if the trip command is used, then the step time has to be longer than the trip time. If the unbalanced load protection function (negative sequence) is active, a three phase fault has to be used for testing.
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Trigger conditions can be specified to control the sequence progression. They may be selected to be: 1. 2.
The test object response (e.g., start signal / trip signal) A manual intervention.
1 2
Trigger = valid ?
Start State 2
The Ramping test module includes the measurement and calculation of test values. These can be assessed automatically and added to the report.
Note:
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The definition of these conditions is explained in more detail in the next chapter.
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3
Practical Introduction to Testing with the Ramping Test Module The Ramping test module can be found on the Start Page of the OMICRON Test Universe. It can also be inserted into an OCC File (Control Center document).
3.1
Defining the Test Object Before testing can begin the settings of the relay to be tested must be defined. In order to do that, the Test Object has to be opened by double clicking the Test Object in the OCC file or by clicking the Test Object button in the test module.
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3.1.1 Device Settings General relay settings (e.g., relay type, relay ID, substation details, CT and VT parameters) are entered in the RIO function Device.
Note:
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The parameters V max and I max limit the output of the currents and voltages to prevent damage to the device under test. These values must be adapted to the respective Hardware Configuration when connecting the outputs in parallel or when using an amplifier. The user should consult the manual of the device under test to make sure that its input rating will not be exceeded.
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3.2
Global Hardware Configuration for Directional Overcurrent Relays The global Hardware Configuration specifies the general input/output configuration of the CMC test set. It is valid for all subsequent test modules and, therefore, it has to be defined according to the relay’s connections. It can be opened by double clicking the Hardware Configuration entry in the OCC file.
3.2.1 Example Output Configuration for Protection Relays with a Secondary Nominal Current of 1 A
VA
VC VB
VN
IA IB IC IN
Note:
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For non-directional overcurrent relays the voltage outputs can be set to
.
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3.2.2 Example Output Configuration for Protection Relays with a Secondary Nominal Current of 5 A
VA
VC VN
VB
IA
IC IB
Note:
IN
Make sure that the rating of the wires is sufficient when connecting the outputs in parallel. For non-directional overcurrent relays the voltage outputs can be set to . The following explanations only apply to protection relays with a secondary nominal current of 1A
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3.2.3 Analog Outputs
The analog outputs, binary inputs and outputs can all be activated individually in the local Hardware Configuration of the specific test module (see chapter 3.3 ). 3.2.4 Binary Inputs 3
2
1
1. 2.
Trip
Start
3.
The start and the trip command are connected to binary inputs. BI1 … BI10 can be used. For wet contacts adapt the nominal voltages of the binary inputs to the voltage of the circuit breaker trip command or select Potential Free for dry contacts. The binary outputs and the analog inputs etc. will not be used for the following tests.
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3.2.5 Wiring of the Test Set for Directional Overcurrent Relays Note:
The following wiring diagrams are examples only. The wiring of the analog current inputs may be different if additional protective functions such as sensitive ground fault protection are provided. In this case IN may be wired separately.
Protection Relay VA VB VC (-) (-) IA IB IC IN
Trip optional
(+) Start (+)
Protection Relay VA VB VC (-) (-) IA IB IC IN
Trip optional
(+) Start (+)
Note:
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For non-directional overcurrent relays the wiring of the voltage outputs is not necessary.
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3.3
Local Hardware Configuration for Directional Overcurrent Testing The local Hardware Configuration activates the outputs/inputs of the CMC test set for the selected test module. Therefore, it has to be defined for each test module separately. It can be opened by clicking the Hardware Configuration button in the test module.
3.3.1 Analog Outputs
Note:
For non-directional overcurrent relays the voltages are already deactivated in the global Hardware Configuration (see chapter 3.2 ). Therefore, they will not be visible in this tab.
3.3.2 Binary Inputs
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3.4
Defining the Test Configuration
3.4.1 General Approach Note:
In this example an overcurrent relay with an IDMT tripping characteristic and an increased pickup value is used (see Table 1 and Figure 2). Because of this, the nominal trip time for the pickup current of 1.65 A is approximately 162 s. However, the start signal is not delayed which is why the start contact is used as the trigger.
When testing the pick-up and the drop-off values for directional or non-directional overcurrent relays, the following steps are recommended. Calculation of the Nominal Values: For testing the pick-up and the drop-off values, the settings (Table 1) as well as the tolerances (Table 2) of the overcurrent protection function must be known. Also, it must be known whether there is an increased pick-up value. From these values the nominal pick-up current, the nominal drop-off current and the absolute tolerances for these currents can be calculated. The calculations for this example are shown below: Nominal pick-up value: 1.1 · IP Nominal drop-off value: 0.95 · 1.1 · IP Current tolerances: 3% or 10 mA Nominal value
TOL-
TOL+
Pick-up
1.65 A
49.5 mA
49.5 mA
Drop-off
1.57 A
47 mA
47 mA
Table 3: Nominal currents and tolerances for this example
Settings in the Test View:
1 2
3 5
6
7
4
1. 2.
As the currents are to be ramped directly, the Set mode should be Direct. In this example a phase to phase fault will be applied. Note: If an unbalanced load protection is activated in the relay a three phase fault should be chosen because a phase to phase fault could trip the unbalanced load protection instead of the overcurrent protection.
3.
For the overcurrent pick-up the Magnitude is ramped.
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Two ramps are needed. One upward ramp to test the pick-up current and one downward ramp to test the drop-off current. The upward ramp is set from 80% to 120% of the nominal pick-up value. The downward ramp runs in the opposite direction. This ensures that the complete tolerance band is covered. The Delta defines the step size of the ramp. This value should be set to ensure there are enough steps inside the tolerance band. It is recommended that approximately 4 steps are made in each half of the tolerance band. This provides sufficient accuracy and keeps the test time short. The step duration dt has to be longer than the pick-up time of the relay. If the trip contact is used as the trigger, the step duration has to be longer than the trip time.
4. 5. 6.
Fault current
7.
To
Tolerance band
5
IP
7 dt From
6
Delta
5
Test time = Ramp State 1 (to measure the pick-up value) = Ramp State 2 (to measure the drop-off value)
Figure 5: Definition of the ramp settings for a pick-up/drop-off test
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Settings in the Detail View:
1 2
3
For directional overcurrent relays all three voltages must be set to the nominal voltage. The angles of the currents have to be adapted to the fault type. For example, a phase to phase fault has 180° between each fault current. For directional overcurrent relays the angles also have to be adjusted to the directional characteristic. The start contact is chosen as the trigger for this test. If the trip contact is used, the step duration of the ramp has to be longer than the trip time (e.g., 1.2 x Trip Time).
1. 2.
3.
Settings in the Measurement view:
5
6
7
4 9 8 4. 5. 6. 7. 8. 9.
In this test the pick-up and drop-off currents are measured. The pick-up value will be measured during the upward ramp. The drop-off value during the downward ramp. The pick-up current will be measured when the start signal is activated. The drop-off current will be measured when it is deactivated. The nominal values as well as the tolerances (Table 3) have to be set. By dividing the measured drop-off current by the measured pick-up current, the drop-off ratio is calculated. After testing, the assessment is made automatically and the actual values, as well as the deviation from the nominal values, are displayed.
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3.5
Why it is Not Possible to Use the Ramping Test Module for the 2nd Element For this example, the General Start signal or the General Trip signal is defined as the trigger condition for testing the pick-up value of the 1st element.
Fault current
For testing the 2nd element the General Start signal cannot be used as the trigger condition because it will operate after the threshold of the 1st element is exceeded. This would prevent the test current from reaching the pick-up value of the 2nd element (see Figure 6).
To
2nd element
1st element
From
t(1st el.) = General Start signal
Test time = General Trip signal
Figure 6: Time signal view of a ramp during an attempt to test the pick-up value of element 2
Note:
The use of the Ramping test module is only possible if the start signal of the 2nd element is wired separately. If only a General Trip signal is available, the test will be stopped as soon as the current of the 1st element is exceeded and the trip time t(1st element) has elapsed and, therefore, it will fail.
To test the 2nd element the Pulse Ramping test module can be used instead.
Feedback regarding this application is welcome by email at [email protected].
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