IEC 61850-9-2 conformance test and the required net-

work bandwidth

Smart Grid Testing depart-ment

Woohyun Seo

1. Merging Unit• Introduction, Advantages, Standards

2. Tripping in Process Bus

3. Conformance test

4. Network Bandwidth for Process Bus

5. Conclusion

Contents

1. Merging Unit - IntroductionBusbar

- Analog Input Transformers

- Analog Measurement

- A/D conversion

are moved away from the IEDs and “are placed” into the merging

unit

Conven-tional CTs/VTs

- Advantage . Good saturation curve- Disadvantage . Signal level output . Noise influence

Non-Conventional CTs/VTs

Merging Unit

Propri-etary Link

Propri-etary Link

Controlled Ethernet Ports

Line protec-tion

PIOC, PTOV, …

Bay controllerCSWI, CSYN, …

Device control inter-face

Process Bus

Time synchConfigura-

tion

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 - StandardsMerging

UnitSignal processing interface

Digital interface(Communication)

IEC TC38 WG37

IEC TC57 WG10IEC 61869-7, ADDITIONAL REQUIRE-

MENTS FOR ELECTRONIC VOLTAGE TRANS-FORMERS

IEC 61869-8, ADDITIONAL REQUIRE-MENTS FOR ELECTRONIC CURRENT RANS-FORMERS

IEC 61869-9, DIGITAL INTERFACE FOR INSTRUMENT TRANSFORMERS

IEC 61869-13, Stand Alone Merging Unit

…

Not published

IEC 61850-9-1, Specific Communication Service Map-ping (SCSM) – Sampled values over serial unidirec-tional multidrop point to point link

IEC 61850-9-2, Specific communication service map-ping (SCSM) – Sampled values over ISO/IEC 8802-3

Withdrawn

Implementa-tionImplementation Guideline for Digital Interface to Instru-ment Transformers using IEC 61850-9-2

Conformance test procedure

Test procedures for Sampled Values Publishers according to the "Implementation Guideline for Digital Interface to In-strument Transformers using IEC 61850-9-2" (9-2LE)

GOOSE OUT

2. Tripping in Process Bus

GOOSE IN GOOSE OUT

SAMPLED VALUES

Time require-ment is more critical!!!

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

2. Tripping in Process Bus

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)

– Verification # of messages per cycle

PPS pulse SV with

Sm-pCnt=0

SV de-lay

Publisher(MU)

Subscriber

288000 messages for 80 samples of 60 Hz

… … …

PPS pulse

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?

PPS pulse

SV with Sm-pCnt=0

SV de-lay

Vo, Io

Vo, Io

Real tripping time may be de-layed

CT/VT or eCT/eVT

Signal process-ing delay

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

Rate Tested(%)(01,01,01) to

(01,01,02) (us)-CT

70.00 18.0

75.00 18.6

80.00 17.4

85.00 17.7

90.00 17.7

95.00 1512529.4

100.00 1502608.9

Rate Tested(%) (01,01,01) to (01,01,02) (%)

70.00 0.000

75.00 0.000

80.00 0.000

85.00 0.000

90.00 0.000

95.00 1.080

100.00 5.789

Passed Rate(%)(01,01,01) to

(01,01,02) (pks/sec)

94.12 73529

Through-put

La-tency

Packet Loss

Network load : 5.88 Mbps

• 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

Rate Tested(%)(01,01,01) to

(01,01,02) (us)-CT

70.00 18.9

75.00 17.0

80.00 19.0

85.00 23.0

90.00 2649.6

95.00 1508004.1

100.00 1499575.3

Rate Tested(%) (01,01,01) to (01,01,02) (%)

70.00 0.000

75.00 0.000

80.00 0.000

85.00 0.000

90.00 1.906

95.00 7.156

100.00 11.577

Passed Rate(%)(01,01,01) to

(01,01,02) (pks/sec)

88.40 69061

Through-put

La-tency

Packet Loss

Network load : 11.6 Mbps= 2*5.8 Mbps

• 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 imple-

mented

– For more stable process bus implementa-tion, the critical points will be• Actual A/D signal processing time delay in device• Packet jitter and latency delay from device

Thank you for lis-tening

Any Questions?

Whseo@keri.re.kr031-8040-4421