IEC 61850-9-2 conformance test
and the required network bandwidth
Smart Grid Testing department
Woohyun Seo
Contents
1. Merging Unit
•
Introduction, Advantages, Standards
2. Tripping in Process Bus
3. Conformance test
4. Network Bandwidth for Process Bus
5. Conclusion
1. Merging Unit - Introduction
Busbar
Non-Conventional CTs/VTs
Conventional
CTs/VTs Proprietary
Proprietary
Link
Link
- Advantage
. Good saturation curve
- Disadvantage
. Signal level output
. Noise influence
Merging Unit
- Analog Input Transformers
- Analog Measurement
- A/D conversion
are moved away from the IEDs and “are placed” into the merging unit
Controlled Ethernet Ports
Process Bus
Line protection
Bay controller
PIOC, PTOV, …
CSWI, CSYN, …
Device
control
interface
Time synch
Configuration
1. Merging Unit - Advantages
• Advantage of process bus with MERGING
UNIT
– Reduce wiring cables and # of CTs/VTs
• In conventional scheme, every IED needs CT(s) and/or
VT(s) for processing
– Improved measuring accuracy
• Short distance between CTs/VTs and signal processor
– Adopting high-performance eCT/eVT
• Small, Light, Broad dynamic range, Isolation between
primary & secondary circuits, etc
– Unified platform for information sharing
• Merging unit broadcast the digitized measured data
based on IEC 61850 standard
1. Merging Unit - Standards
Merging Unit
Signal processing
interface
IEC TC38 WG37
IEC 61869-7, ADDITIONAL REQUIREMENTS
FOR ELECTRONIC VOLTAGE TRANSFORMERS
IEC 61869-8, ADDITIONAL REQUIREMENTS
FOR ELECTRONIC CURRENT RANSFORMERS
IEC 61869-9, DIGITAL INTERFACE FOR
INSTRUMENT TRANSFORMERS
…
IEC 61869-13, Stand Alone Merging Unit
Not published
Digital interface
(Communication)
IEC TC57 WG10
IEC 61850-9-1, Specific Communication Service Mapping
(SCSM) – Sampled values over serial unidirectional
multidrop point to point link
Withdrawn
IEC 61850-9-2, Specific communication service mapping
(SCSM) – Sampled values over ISO/IEC 8802-3
Implementation
Implementation Guideline for Digital Interface to Instrument
Transformers using IEC 61850-9-2
Conformance test procedure
Test procedures for Sampled Values Publishers according to
the "Implementation Guideline for Digital Interface to Instrument
Transformers using IEC 61850-9-2" (9-2LE)
2. Tripping in Process Bus
GOOSE OUT
2. Tripping in Process Bus
SAMPLED VALUES
GOOSE IN
Time requirement
is more critical!!!
GOOSE OUT
2. Tripping in Process Bus
• A/D signal processing time delay
– Primary condition for available protection
• Guideline : 3 ms (IEC 60044-8)
• Packet jitter and latency control
– Part of performance test
• Only the total number of packets in 1 sec existed
• Standard based syntax
– Following IEC 61850-9-2 and IEC 61869 series
• Network bandwidth
– Lack of bandwidth makes packet loss
• Out of range from conformance test
3. Conformance test
• Conformance test procedure
– Documentation : 2 test cases
– Configuration : 9 test cases
– Communication services : 17 test cases
• 50/60 Hz, 80/256 samples
According to “Guideline”,
Time master is based on
“PPS”
3. Conformance test
• SV conformance test
– Verify conformity and performance
• Performance is very important for MU
• Accuracy test is not included
• Conformity
– Connecter and Link layer format verification
• 100Base-FX full duplex with ST, MT-RJ, LC fibers or Rj45
– APDU or ASDU format verification
– Quality and Test bit verification
3. Conformance test
• Performance test
– SV maximum delay criterion : ~3 ms(3.3 ms)
Publisher(MU)
PPS pulse
SV delay
SV with
SmpCnt=0
Subscriber
– Verification # of messages per cycle
…
PPS pulse
…
…
288000 messages for 80 samples of 60 Hz
PPS pulse
Jitter and latency control are required!
3. Conformance test
• Limitation of SV conformance test
– Not verifying focusing on packet treatment
• What if MU makes the signal processing delay?
CT/VT or eCT/eVT
Vo, Io
PPS pulse
SV delay
Signal processing
delay
SV with
SmpCnt=0
Vo, Io
Real tripping time may be delayed
4. Network Bandwidth for Process Bus
• Background from IEC 61850-9-1
– Telegram length : 888bit(packet) + 96bit(interFrame)
– BW : 80samples*60Hz*984bits < 5Mbps (per stream)
Reliable?
4. Network Bandwidth for Process Bus
• Simple test
– Merging Unit
• 100Mbps, Max 2 streams, 80samples/Hz
– Time Synch
• 1 PPS from GPS
– Switch
• Separate network only for process bus with MU
• Switching latency : 7 micro second
• Switching bandwidth : 9.2 Gbps
– Testing tool
• Smart bit applications
• Packet size : 140 bytes(SMV packet : 128 bytes)
4. Network Bandwidth for Process Bus
• 1 stream
Latency
Throughput
Passed Rate(%)
94.12
(01,01,01) to (01,
01,02) (pks/sec)
73529
Network load : 5.88 Mbps
•
Rate Tested(%)
Packet Loss
(01,01,01) to (01,01,0
2) (us)-CT
Rate Tested(%)
(01,01,01) to (01,01,0
2) (%)
70.00
18.0
70.00
0.000
75.00
18.6
75.00
0.000
80.00
17.4
80.00
0.000
85.00
17.7
85.00
0.000
90.00
17.7
90.00
0.000
95.00
1512529.4
95.00
1.080
100.00
1502608.9
100.00
5.789
Switching bandwidth(9 Gbps) is enough to handle this amount of traffic load
(9,000 / 5.88 = 1,530 ports can be supported)
4. Network Bandwidth for Process Bus
• 2 streams
Latency
Throughput
Passed Rate(%)
(01,01,01) to (01,
01,02) (pks/sec)
88.40
69061
Rate Tested(%)
Packet Loss
(01,01,01) to (01,01,0
2) (us)-CT
Rate Tested(%)
(01,01,01) to (01,01,0
2) (%)
70.00
18.9
70.00
0.000
Network load : 11.6 Mbps
75.00
17.0
75.00
0.000
= 2*5.8 Mbps
80.00
19.0
80.00
0.000
85.00
23.0
85.00
0.000
90.00
2649.6
90.00
1.906
95.00
1508004.1
95.00
7.156
100.00
1499575.3
100.00
11.577
•
Network load for 2 streams is similar to twice one for 1 stream
5. Conclusion
• Expectation
– Network Bandwidth measurement in the real
(simulated) process bus network
• Theoretically, 100 Mbps based network can handle more
than 10 MUs
• But, need to check if how many MUs can implemented
– For more stable process bus implementation, the
critical points will be
• Actual A/D signal processing time delay in device
• Packet jitter and latency delay from device
Thank you for listening
Any Questions?
Whseo@keri.re.kr
031-8040-4421