Sampled Value Alignment; Channel Mappings For Sav Test, Sav Questionable, Sav Invalid; Data Quality - GE MiCOM P40 Technical Manual

Chapter 6 - Sampled Value Operation
4

SAMPLED VALUE ALIGNMENT

Sampled Value frames from different Merging Units on the Process Bus may not arrive at the same time at the IED.
The transmission delay depends on the background Ethernet traffic and how many switches are used in the
Process Bus network.
Transmission delays do not usually matter for functions such as three-phase overcurrent protection where current
signals are all received in a single frame. However, a function such as distance protection uses voltage and current
signals which may be from different merging units with different transmission delays. The SV interface
synchronises the voltage and current samples that are sent to the IED's distance protection function. The IED then
uses the Merge Unit Delay setting, which is set to the maximum expected delay between the first and last
Sampled Value.
The following examples show how you would need to set the delay.
If the IED receives one Logical Node only, no delay is needed so set the merging unit delay to 0 ms.
●
If the IED receives several Logical Nodes at the same time, no delay is needed so set the merging unit delay
●
to 0 ms.
If the IED receives several Logical Nodes but not at the same time, set the merging unit delay to an
●
appropriate non-zero value.
If all the Logical Nodes configured in the IED are not received during the merging unit delay time, an alarm is
raised.
To set the merging unit delay during commissioning, set MUs Delay Search to Yes. The IED then monitors the
Sampled Value frames received for the next two seconds and displays the maximum delay between identical
samples.
4.1

CHANNEL MAPPINGS FOR SAV TEST, SAV QUESTIONABLE, SAV INVALID

These signals correspond to the analogue channels in a conventional MiCOM IED. The channel name appears on
the IED display against each bit.
P446, P546, P841B
0 1 2 3 4
VA VB VC VSC1 IA1 IB1 IC1
4.2

DATA QUALITY

Any degradation in the measurement or transmission of Sampled Values means that the protection function of the
IED may not operate correctly. Data frames from a typical Logical Node have quality flags assigned to each of the
channels. The device adapts the behaviour of protection functions according to these quality flags. The available
quality flags are Good, Invalid and Questionable. A Test flag is also available for test purposes.
A protection function operates normally when all the necessary Sampled Value inputs are available and have a
Good Quality flag. When the flag for one or more of the Sampled Value inputs changes to Invalid, the protection
function is inhibited. When the flag for one or more of the Sampled Value inputs changes to Questionable, the
protection function can either be inhibited or not, depending on the chosen options in the Trus Ques Data setting.
The options are:
Bit 0:Out of Range
●
Bit 1:Bad Reference
●
Bit 2:Oscillatory
●
Bit 3:Old Data
●
● Bit 4:Inconsistent
Bit 5:Inaccurate
●
98
5 6 7 8 9
IM INSEN IA2 IB2 IC2
10 11 12 13 14 15 16 17 18 19 20 21 22 23
VSC2
P446SV
P446SV-TM-EN-1