Texas Instruments | Design for State Grid Corporation of China RS-485 Standard – THVD1500 | Application notes | Texas Instruments Design for State Grid Corporation of China RS-485 Standard – THVD1500 Application notes

Texas Instruments Design for State Grid Corporation of China RS-485 Standard – THVD1500 Application notes
Application Report
SLMA008 – November 2017
Design for State Grid Corporation of China RS-485
Standard - THVD1500
ABSTRACT
The new THVD1500 half-duplex RS-485 transceiver was designed to meet the Electroc-Static Discharge
(ESD) requirements listed in the Q/GDW 11179.11-2015 standard, published by the State Grid
Corporation of China (SGCC). This document describes these standards, and details the THVD1500
performance versus the standards.
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2
3
Contents
State Grid Corporation of China (SGCC) ................................................................................. 2
IEC 61000-4-2 and IEC 61000-4-4 Tests................................................................................. 2
Application Case ............................................................................................................. 3
List of Figures
1
Voltage Waveform of an EFT Pulse and Timing Sequence of an Entire Test Cycle ............................... 2
2
THVD1500 Bus Voltage Waveform During EFT Strike ................................................................. 3
3
Inspection Report From SGCC Showing the THVD1500 Passed All Tests
.........................................
4
List of Tables
1
IEC 61000-4-2 ESD Test Voltage Levels ................................................................................. 2
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SLMA008 – November 2017
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Design for State Grid Corporation of China RS-485 Standard - THVD1500
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1
State Grid Corporation of China (SGCC)
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www.ti.com
State Grid Corporation of China (SGCC)
The State Grid Corporation of China (SGCC) is a state-owned electric utility company in China which
provides electricity to five geographic regions and 80% of the Chinese population. In the State Grid
Enterprise Standard (Q/GDW), published by SGCC, the standard Q/GDW 11179.11-2015 covers the
technical specification of components for electricity meters. The document is published with the intention
to promote smart e-meters and electricity information acquisition systems. Part 11 of the standard
discusses serial communication protocol for RS-485 transceivers. The standard gives technical
specifications in many details such as pin-out, functionality, data rate, and the electrical characteristics of
drivers and receivers. To help make the e-meter energy efficient, the standard also requires RS-485
devices to consume lower power, such as 1-uA receiver input leakage and 700-uA operation current for
driver and receiver. Additionally, to accommodate the latest industrial needs, the standard gives specific
requirements on ESD performance, which is ±4-kV HBM, ±2-kV EFT (similar to IEC 61000-4-4), and ±8kV IEC (similar to IEC61000-4-2).
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IEC 61000-4-2 and IEC 61000-4-4 Tests
IEC 61000-4-2 is a system-level ESD test that imitates a charged person discharging to a grounded end
system through a metal object, such as a screw driver. This test is considered more stringent than HBM,
and is summarized in Table 1. The ±8-kV test voltage of level 4 is equivalent to 30-A peak current during
the transient. THVD1500 can create a low impedance at the transient event that takes a large amount of
current. Thus, it survives the 8-kV IEC test under the SGCC inspection.
Table 1. IEC 61000-4-2 ESD Test Voltage Levels
Contact Discharge
Air Discharge
Level
Test Voltage (kV)
Peak Current (A)
Level
Test Voltage (kV)
1
2
7.5
1
2
2
4
15
2
4
3
6
22.5
3
8
4
8
30
4
15
*
Special
Special
*
Special
Inductive loads such as relays, switch contactors, or heavy-duty motors can create high-frequency bursts
during transition. The IEC 61000-4-4 test is intended to simulate the transients created by such switching
of inductive loads on AC power lines. The test can be performed on power lines or I/O data lines, with a
burst of pulses that have predetermined amplitude and limited duration. Figure 1 shows the shape of a
typical EFT pulse and the timing sequence of the test pulses. SGCC requires RS-485 transceivers to have
BER < 10-7 during communication with the disturbance of ±2-kV spikes at a repetition rate of 5 kHz, 10
kHz, and 100 kHz.
Figure 1. Voltage Waveform of an EFT Pulse and Timing Sequence of an Entire Test Cycle
2
Design for State Grid Corporation of China RS-485 Standard - THVD1500
Copyright © 2017, Texas Instruments Incorporated
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Application Case
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Figure 2 shows the voltage waveform captured on the bus (differential voltage) during the EFT test. The
waveform shows that THVD1500 recovers the communication quickly enough that the message to or from
the controller does not get misinterpreted.
Figure 2. THVD1500 Bus Voltage Waveform During EFT Strike
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Application Case
To demonstrate a real application case, TI published reference design TIDM-1005. This reference design
implements a smart meter data collector with protocol conversion between Meter Bus (M-Bus) and RS485 networks. The system design is discussed in detail, and many related system tests are also shown.
This report shows that the system passed the IEC ESD tests beyond the ±8-kV level, and showed less
than 10-7 BER with all EFT tests.
These test results demonstrate that the THVD1500 meets the requirements specified in Q/GDW
11179.11-2015. The THVD1500 has been certified by SGCC (shown in Figure 3) and is qualified for use
in all smart e-meters deployed by SGCC.
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Application Case
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Figure 3. Inspection Report From SGCC Showing the THVD1500 Passed All Tests
4
Design for State Grid Corporation of China RS-485 Standard - THVD1500
Copyright © 2017, Texas Instruments Incorporated
SLMA008 – November 2017
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