1
00:00:18,199 --> 00:00:27,249
A Rogowski coil is a flexible air-cored current transducer (CT) used for measuring AC current.

2
00:00:27,383 --> 00:00:32,666
. Because it has no ferromagnetic core, it does not saturate.

3
00:00:33,126 --> 00:00:40,933
The raw output of the coil is typically proportional to di/dt (i.e., the induced voltage),

4
00:00:41,256 --> 00:00:46,066
), therefore it is normally supplied together with an integrator

5
00:00:46,733 --> 00:00:51,183
so that the output becomes proportional to the current waveform.

6
00:00:51,533 --> 00:00:56,646
The transfer ratio is commonly expressed in mV/A.

7
00:00:57,379 --> 00:01:01,989
Consequently, when testing relays that use Rogowski-coil inputs,

8
00:01:02,656 --> 00:01:06,626
, only accurate voltage sources should be used.

9
00:01:07,093 --> 00:01:13,143
An important consideration when testing such relays with the AMT205

10
00:01:13,733 --> 00:01:21,773
is that the unit’s main voltage sources do not provide sufficient accuracy for these applications.

11
00:01:22,239 --> 00:01:30,469
. This is because their voltage range is ±420 V (840 V peak-to-peak),

12
00:01:31,080 --> 00:01:35,410
which reduces achievable resolution/accuracy.

13
00:01:35,676 --> 00:01:42,286
Therefore, the voltage sources to be used are limited to the device’s Cross Voltage sources,

14
00:01:42,686 --> 00:01:46,656
which have a smaller range and higher accuracy.

15
00:01:47,056 --> 00:01:54,906
To convert current sources to voltage sources (i.e., to use the Cross Voltage sources),

16
00:01:55,172 --> 00:02:01,422
in Hardware Configuration, set the value in the Type column to Voltage.

17
00:02:04,755 --> 00:02:07,925
Note that with this configuration alone,

18
00:02:08,059 --> 00:02:14,323
functions such as Distance and Differential testing cannot be performed directly.

19
00:02:14,550 --> 00:02:19,790
. This is because these functions require outputs with defined Targets;

20
00:02:20,013 --> 00:02:24,503
if the selected source is originally a current source,

21
00:02:24,702 --> 00:02:31,323
the test execution may become challenging due to the way targets and outputs are allocated.

22
00:02:31,563 --> 00:02:37,213
Therefore, to test relays of this type using the Vebko device and software,

23
00:02:37,412 --> 00:02:42,589
the software configuration must be adjusted as described below.

24
00:02:42,783 --> 00:02:46,790
Consider the Distance protection function as an example.

25
00:02:46,913 --> 00:02:59,243
. Testing this function requires three voltage sources with targets VL1-E, VL2-E, VL3-E

26
00:02:59,268 --> 00:03:06,590
and three current sources with targets IL1, IL2, IL3.

27
00:03:06,812 --> 00:03:11,982
Also note that when the relay input is provided via a Rogowski coil,

28
00:03:12,007 --> 00:03:16,057
all test signals must be voltage signals.

29
00:03:16,166 --> 00:03:31,456
Hence, we convert the three phases of Current Group A into Cross Voltage sources with targets VL1-E, VL2-E, VL3-E.

30
00:03:31,481 --> 00:03:35,291
. The Display Type shall be set to Voltage,

31
00:03:42,364 --> 00:03:50,534
and the Coefficient shall be entered according to the coil transfer ratio (e.g., 0.1).

32
00:03:50,559 --> 00:03:56,487
This means any value entered for the test will be multiplied by this coefficient

33
00:03:56,512 --> 00:04:00,962
and will appear as a voltage at the corresponding voltage output.

34
00:04:00,987 --> 00:04:04,557
Next, the current channels must be configured.

35
00:04:04,582 --> 00:04:08,512
For this purpose, set Display Type to Current,

36
00:04:08,559 --> 00:04:22,526
set the targets to IL1, IL2, IL3, and enter the Coefficient according to the coil transfer ratio (e.g., 0.1).

37
00:04:22,551 --> 00:04:28,201
The most critical point here is changing the Type from Current to Voltage,

38
00:04:28,226 --> 00:04:33,985
, because the “current” input is provided by the Rogowski coil as a voltage signal.

39
00:04:34,010 --> 00:04:39,780
With this configuration, the three phases of Current Group A are cross-assigned

40
00:04:39,805 --> 00:04:46,935
and converted to voltage outputs to feed the voltage input of the relay’s Distance function,

41
00:04:46,960 --> 00:04:53,186
and the three phases of Current Group B are cross-assigned

42
00:04:53,211 --> 00:05:00,381
and converted to the required “current” channels to feed the current input of the relay’s Distance function.