D20/D200 Technical Overview
GE Grid Solutions
70
PRPI-019-3.00-10
GE Information
Type
Properties
D.20 Link
•
Provides communications between the D20/D200 main processor and D20 I/O peripherals
•
Two D.20 Links per main processor
•
High-speed, high-level data link (HDLC/X.25)
•
RS-485 serial link, half duplex, 250 kbps
•
Transformer-coupled/isolated for high reliability and protection from electrically noisy
environments
•
Manchester-encoded for increased data integrity
•
Dual communication channels for backup communications
•
Shielded LAN cable or a glass/plastic fiber optic cable
•
RS-485 to multi-mode fiber-optic converters are available to extend the distance range of the
D20/D200, or to improve system noise immunity
•
Each D.20 Link supports the following:
D20ME/ME II in D20
Chassis
D20ME/ME II in D200
Chassis
Without Repeaters
Up to 31 I/O Peripherals
Up to 31 I/O Peripherals
With Repeaters
Up to 120 I/O Peripherals
Up to 120 I/O Peripherals
Ethernet
•
D20/D200 supports communication with substation equipment through two Ethernet ports
•
D20EME Ethernet Memory Expansion module provides two independent Ethernet channels
using one of the following formats:
10BASE-T
Provides two RJ-45 connectors for connecting to CAT5, or greater, UTP
cabling
10BASE2
Provides two BNC connectors for connecting to thin coax cabling
10BASE-FL
Provides two ST-style connectors for directly connecting to a single or
multi-mode glass or plastic fiber optic cable
2.8 D.20 Link
The D20 main processor communicates with D20 peripheral I/O modules over a high-speed,
high-level data link (HDLC) called the D.20 Link. The D.20 Link is an RS-485 serial link,
operating half-duplex at 250 kbps. The link is transformer-coupled/isolated for high reliability
and protection from electrically noisy environments. A fiber-optic communications link, which
has greater noise immunity to power switching transients and voltage gradients, is also available.
The D.20 Link protocol is a partial emulation of the standard X.25 protocol. This
communications protocol uses the HDLC format with Manchester encoding.
Using a D.20 Link, the D20 main processor can support up to 31 D20 I/O peripheral modules in
a standard configuration. Repeater/extension modules may be used to expand beyond this limit to
a maximum of 120 (D20) or 480 (D200) peripheral I/O modules.
The D20/D200 can be equipped to provide D.20 Link redundancy, as described in section 2.9.2 ,
